//! Compile complete source in a fresh VM or retain a worker-owned Console VM.
//! Console retains mounted native references and publishes immutable frames after successful inputs.
use anyhow::{Result, bail};
use endor_core::{ExecutionLimits, ObjectRef, Value, Vm, VmError};
use frontend::{
    EndorReader, SourceUnit, Span,
    ast::{AstRoot, Decl, DeclKind, Expr, ExprKind, Spanned, Stmt, StmtKind, visitor::Visitor},
};
use std::collections::BTreeSet;

use crate::{
    document::{CodeNode, RenderDocument},
    endor_script::{self, SourcePlan},
    layout, ui_bridge,
};

pub const MAX_SOURCE_BYTES: usize = 1_048_576;
const LIMITS: ExecutionLimits = ExecutionLimits {
    max_frames: 128,
    max_instructions: 1_000_000,
};
const MAX_AST_NODES: usize = 10_000;
const MAX_AST_DEPTH: usize = 64;

pub fn compile(source: &str, namespace: &str, submission: u64) -> Result<RenderDocument> {
    if source.len() > MAX_SOURCE_BYTES {
        bail!("source exceeds the 1 MiB limit");
    }
    let source = EndorReader::from_text(format!("{namespace} [submission {submission}]"), source);
    let plan = endor_script::parse(&source)?;
    let mut budget = AstBudget::default();
    for ast in plan.roots() {
        budget.visit_ast_root(ast)?;
    }
    let compiled = compile_plan(&source, &plan)?;
    let root = architecture(&source, &plan, namespace, submission);
    let mut candidate = Candidate::new()?;
    let result: Result<RenderDocument> = (|| {
        let globals = candidate.vm.new_dict()?;
        candidate.globals = Some(globals);
        candidate.roots.push(globals);
        let bridge = ui_bridge::install(&mut candidate.vm, &mut candidate.roots)?;
        bridge.install_globals(&mut candidate.vm, globals)?;
        let limits = match &plan {
            SourcePlan::Module(_) => LIMITS,
            SourcePlan::Script(_) => ExecutionLimits {
                max_instructions: LIMITS.max_instructions / compiled.len().max(1),
                ..LIMITS
            },
        };
        for template in &compiled {
            let code = template.load(&mut candidate.vm)?;
            candidate.roots.push(code);
            let value = candidate
                .vm
                .execute_with_limits(code, globals, limits)
                .map_err(|error| runtime_error(&candidate.vm, error))?;
            candidate.vm.release_value(value)?;
        }
        let ui_root = match &plan {
            SourcePlan::Script(_) => bridge
                .rendered(&candidate.vm)?
                .ok_or_else(|| anyhow::anyhow!("script must call ui.page().render(root)"))?,
            SourcePlan::Module(_) => {
                let entry = candidate
                    .vm
                    .dict_get(globals, &Value::Text("main".into()))?
                    .ok_or_else(|| {
                        anyhow::anyhow!("declare main or render a page from a top-level script")
                    })?;
                let Value::Object(entry) = entry else {
                    bail!("main must be a callable function");
                };
                let value = candidate
                    .vm
                    .call_with_limits(entry, &[], LIMITS)
                    .map_err(|error| runtime_error(&candidate.vm, error))?;
                let snapshot = bridge
                    .rendered(&candidate.vm)
                    .and_then(|rendered| match rendered {
                        Some(root) => Ok(root),
                        None => ui_bridge::snapshot(&candidate.vm, &value),
                    });
                candidate.vm.release_value(value)?;
                snapshot?
            }
        };
        let document = RenderDocument {
            source: source.text().to_owned(),
            root: Some(root),
            frame: layout::frame(&ui_root)?,
            ui_root: Some(ui_root),
        };
        document.validate()?;
        Ok(document)
    })();
    let cleanup = candidate.close();
    match (result, cleanup) {
        (Ok(document), Ok(())) => Ok(document),
        (Err(error), Ok(())) | (Ok(_), Err(error)) => Err(error),
        (Err(error), Err(cleanup)) => Err(error.context(format!("candidate cleanup: {cleanup}"))),
    }
}

/// Evaluate exactly one expression in a disposable VM; never touch the published page.
pub fn evaluate(source: &str) -> Result<String> {
    if source.len() > MAX_SOURCE_BYTES {
        bail!("expression exceeds the 1 MiB limit");
    }
    let source = EndorReader::from_text("console expression", source);
    let ast = frontend::parse_source_ast(&source, frontend::ParseMode::Expression)?;
    AstBudget::default().visit_ast_root(&ast)?;
    let compiled = compiler::compile_ast(&ast, &source, &compiler::CompileOptions::default())
        .map_err(|error| source.annotate(error))?;
    let mut candidate = Candidate::new()?;
    let result = (|| {
        let globals = candidate.vm.new_dict()?;
        candidate.globals = Some(globals);
        candidate.roots.push(globals);
        let code = compiled.load(&mut candidate.vm)?;
        candidate.roots.push(code);
        let value = candidate
            .vm
            .execute_with_limits(code, globals, LIMITS)
            .map_err(|error| runtime_error(&candidate.vm, error))?;
        let rendered = match &value {
            Value::Nil => "nil".to_owned(),
            Value::Bool(v) => v.to_string(),
            Value::Text(v) => format!("{v:?}"),
            Value::Number(v) => v.to_string(),
            Value::Object(v) => candidate.vm.repr(*v)?,
        };
        candidate.vm.release_value(value)?;
        Ok(rendered)
    })();
    let cleanup = candidate.close();
    match (result, cleanup) {
        (Ok(value), Ok(())) => Ok(value),
        (Err(e), _) | (_, Err(e)) => Err(e),
    }
}

fn compile_plan(source: &SourceUnit, plan: &SourcePlan) -> Result<Vec<compiler::CompiledCode>> {
    compile_plan_with_globals(
        source,
        plan,
        std::iter::once("ui")
            .chain(ui_bridge::TYPE_NAMES.iter().copied())
            .chain(ui_bridge::QUERY_NAMES.iter().copied())
            .map(str::to_owned)
            .collect(),
    )
}

fn compile_plan_with_globals(
    source: &SourceUnit,
    plan: &SourcePlan,
    mut globals: BTreeSet<String>,
) -> Result<Vec<compiler::CompiledCode>> {
    // Match Aster module behavior for function forward references. Bindings are
    // added in source order; every executable statement still uses Aster's own
    // single-input Interactive compiler and the candidate's shared globals.
    for root in plan.roots() {
        if let AstRoot::Interactive(input) = root {
            for statement in &input.statements {
                if let StmtKind::Declaration(decl) = &statement.kind {
                    let name = match &decl.kind {
                        DeclKind::Function(function) => &function.name,
                        DeclKind::Class(class) => &class.name,
                    };
                    globals.insert(name.text.clone());
                }
            }
        }
    }
    let mut compiled = Vec::with_capacity(plan.roots().len());
    for root in plan.roots() {
        let options = compiler::CompileOptions {
            globals: globals.iter().cloned().collect(),
        };
        compiled.push(
            compiler::compile_ast(root, source, &options)
                .map_err(|error| source.annotate(error))?,
        );
        if let AstRoot::Interactive(input) = root {
            for statement in &input.statements {
                if let StmtKind::Binding(binding) = &statement.kind {
                    globals.insert(binding.name.text.clone());
                } else if let StmtKind::Assignment(assignment) = &statement.kind {
                    globals.insert(assignment.name.text.clone());
                }
            }
        }
    }
    Ok(compiled)
}

/// One real VM, owned only by the existing execution worker. No history replay.
/// The UI bridge shares the same managed object heap and publishes atomic frames.
pub struct ReplSession {
    candidate: Candidate,
    bridge: ui_bridge::UiBridge,
    pub id: u64,
    inputs: usize,
    ast_nodes: usize,
    source: String,
    nodes: Vec<CodeNode>,
    faulted: bool,
    program_root: Option<CodeNode>,
}
pub struct ReplResult {
    pub value: String,
    pub document: Option<RenderDocument>,
    pub bindings: usize,
    pub input: usize,
}
impl ReplSession {
    /// Compile once into an isolated candidate, then keep its actual heap and
    /// callback environments alive after the first successful publication.
    pub fn load(
        source: &str,
        namespace: &str,
        submission: u64,
        id: u64,
    ) -> Result<(Self, RenderDocument)> {
        Self::load_with_viewport(source, namespace, submission, id, None)
    }

    pub fn load_with_viewport(
        source: &str,
        namespace: &str,
        submission: u64,
        id: u64,
        viewport: Option<crate::layout::Size>,
    ) -> Result<(Self, RenderDocument)> {
        if source.len() > MAX_SOURCE_BYTES {
            bail!("source exceeds the 1 MiB limit");
        }
        let unit = EndorReader::from_text(format!("{namespace} [submission {submission}]"), source);
        let plan = endor_script::parse(&unit)?;
        let mut budget = AstBudget::default();
        for ast in plan.roots() {
            budget.visit_ast_root(ast)?;
        }
        let compiled = compile_plan(&unit, &plan)?;
        let mut runtime = Self::new(id)?;
        runtime
            .bridge
            .set_viewport(&mut runtime.candidate.vm, viewport)?;
        let globals = runtime.candidate.globals.expect("program globals");
        let limits = if matches!(plan, SourcePlan::Script(_)) {
            ExecutionLimits {
                max_instructions: LIMITS.max_instructions / compiled.len().max(1),
                ..LIMITS
            }
        } else {
            LIMITS
        };
        for template in &compiled {
            let code = template.load(&mut runtime.candidate.vm)?;
            let result = runtime
                .candidate
                .vm
                .execute_with_limits(code, globals, limits)
                .map_err(|error| runtime_error(&runtime.candidate.vm, error));
            runtime.candidate.vm.release(code)?;
            runtime.candidate.vm.release_value(result?)?;
        }
        if matches!(plan, SourcePlan::Module(_)) {
            let main = runtime
                .candidate
                .vm
                .dict_get(globals, &Value::Text("main".into()))?
                .ok_or_else(|| anyhow::anyhow!("declare a main function"))?;
            let Value::Object(main) = main else {
                bail!("main must be callable");
            };
            let value = runtime
                .candidate
                .vm
                .call_with_limits(main, &[], LIMITS)
                .map_err(|error| runtime_error(&runtime.candidate.vm, error))?;
            let opened = if runtime.bridge.has_page()? {
                Ok(())
            } else {
                runtime.bridge.open_value(&mut runtime.candidate.vm, &value)
            };
            runtime.candidate.vm.release_value(value)?;
            opened?;
        }
        if !runtime.bridge.has_page()? {
            bail!("script must call page.render(root) or ui.open(value)");
        }
        runtime.source = source.into();
        runtime.ast_nodes = budget.nodes;
        runtime.program_root = Some(architecture(&unit, &plan, namespace, submission));
        let document = runtime
            .refresh_document()?
            .ok_or_else(|| anyhow::anyhow!("program did not publish a Page"))?;
        runtime
            .bridge
            .reclaim(&mut runtime.candidate.vm, &mut runtime.candidate.roots)?;
        Ok((runtime, document))
    }

    pub fn new_with_viewport(id: u64, viewport: Option<crate::layout::Size>) -> Result<Self> {
        let mut runtime = Self::new(id)?;
        runtime
            .bridge
            .set_viewport(&mut runtime.candidate.vm, viewport)?;
        Ok(runtime)
    }

    pub fn new(id: u64) -> Result<Self> {
        let mut candidate = Candidate::new()?;
        let globals = candidate.vm.new_dict()?;
        candidate.globals = Some(globals);
        candidate.roots.push(globals);
        let bridge = ui_bridge::install(&mut candidate.vm, &mut candidate.roots)?;
        bridge.install_globals(&mut candidate.vm, globals)?;
        Ok(Self {
            candidate,
            bridge,
            id,
            inputs: 0,
            ast_nodes: 0,
            source: String::new(),
            nodes: Vec::new(),
            faulted: false,
            program_root: None,
        })
    }
    pub fn execute(&mut self, source: &str, namespace: &str) -> Result<ReplResult> {
        if self.faulted {
            bail!(
                "runtime stopped after a callback or rendering failure; reset the session or replace its program"
            );
        }
        if source.len() > MAX_SOURCE_BYTES {
            bail!("input exceeds 1 MiB");
        }
        if self.inputs >= 256 || self.source.len() + source.len() + 80 > MAX_SOURCE_BYTES {
            bail!("console session exceeds 256 inputs or 1 MiB; reset the session to continue");
        }
        let source = EndorReader::from_text(
            format!("console session {} input {}", self.id, self.inputs + 1),
            source,
        );
        let plan = endor_script::parse(&source)?;
        let mut budget = AstBudget::default();
        for ast in plan.roots() {
            budget.visit_ast_root(ast)?;
        }
        if self.ast_nodes + budget.nodes > MAX_AST_NODES {
            bail!("console session exceeds 10000 AST nodes; reset the session to continue");
        }
        let globals = self.candidate.globals.expect("live console globals");
        let names = self
            .candidate
            .vm
            .dict_items(globals)?
            .iter()
            .filter_map(|(key, _)| {
                if let Value::Text(name) = key {
                    Some(name.clone())
                } else {
                    None
                }
            })
            .collect();
        let compiled = compile_plan_with_globals(&source, &plan, names)?;
        // Parsing/compilation finish before any new statement runs. Successful earlier
        // statements in a runtime-failed input remain live, as in an ordinary REPL.
        self.bridge.discard_pending(&mut self.candidate.vm)?;
        self.bridge
            .reclaim(&mut self.candidate.vm, &mut self.candidate.roots)?;
        self.inputs += 1;
        self.ast_nodes += budget.nodes;
        if let Some(root) = self.program_root.take() {
            self.nodes.push(root);
        }
        if !self.source.is_empty() && !self.source.ends_with('\n') {
            self.source.push('\n');
        }
        let offset = line_starts(&self.source).len();
        self.source
            .push_str(&format!("// Console input {}\n", self.inputs));
        self.source.push_str(source.text());
        if !self.source.ends_with('\n') {
            self.source.push('\n');
        }
        let mut node = architecture(
            &source,
            &plan,
            &format!("{namespace}:console-{}", self.id),
            self.inputs as u64,
        );
        node.name = format!("Input {}", self.inputs);
        shift_node_lines(&mut node, offset);
        self.nodes.push(node);
        let result: Result<ReplResult> = (|| {
            let limits = ExecutionLimits {
                max_instructions: LIMITS.max_instructions / compiled.len().max(1),
                ..LIMITS
            };
            let mut rendered_value = "nil".to_owned();
            for (ast, template) in plan.roots().iter().zip(&compiled) {
                let code = template.load(&mut self.candidate.vm)?;
                let executed = self
                    .candidate
                    .vm
                    .execute_with_limits(code, globals, limits)
                    .map_err(|error| runtime_error(&self.candidate.vm, error));
                self.candidate.vm.release(code)?;
                let value = executed?;
                // Keep the actual last result accessible as `_`, including unnamed UI objects.
                let display = if let AstRoot::Interactive(input) = ast {
                    match &input.statements[0].kind {
                        StmtKind::Binding(binding) => self
                            .candidate
                            .vm
                            .dict_get(globals, &Value::Text(binding.name.text.clone()))?
                            .unwrap_or_else(|| value.clone()),
                        StmtKind::Assignment(assignment) => self
                            .candidate
                            .vm
                            .dict_get(globals, &Value::Text(assignment.name.text.clone()))?
                            .unwrap_or_else(|| value.clone()),
                        _ => value.clone(),
                    }
                } else {
                    value.clone()
                };
                let repr = value_repr(&self.candidate.vm, &display);
                let retained =
                    self.candidate
                        .vm
                        .dict_set(globals, Value::Text("_".into()), display);
                self.candidate.vm.release_value(value)?;
                retained?;
                rendered_value = repr?;
            }
            let document = self.refresh_document()?;
            Ok(ReplResult {
                value: rendered_value,
                document,
                bindings: self
                    .candidate
                    .vm
                    .dict_items(globals)?
                    .len()
                    .saturating_sub(1),
                input: self.inputs,
            })
        })();
        if result.is_err() {
            self.take_window_commands()?;
            self.bridge.discard_pending(&mut self.candidate.vm)?;
            if let Some(node) = self.nodes.last_mut() {
                node.name
                    .push_str(" (error; earlier statements may remain live)");
            }
        }
        self.bridge
            .reclaim(&mut self.candidate.vm, &mut self.candidate.roots)?;
        result
    }

    fn refresh_document(&mut self) -> Result<Option<RenderDocument>> {
        let mut last = None;
        let mut work = 0;
        let mut mutated_mounts = false;
        let result = (|| loop {
            let Some(root) = self.bridge.prepare_frame(&mut self.candidate.vm)? else {
                return Ok(last);
            };
            mutated_mounts = true;
            let frame = self
                .bridge
                .layout_frame(&mut self.candidate.vm, root.clone())?;
            let mut document = RenderDocument {
                source: self.source.clone(),
                root: Some(self.program_root.clone().unwrap_or_else(|| CodeNode {
                    id: format!("console-session-{}", self.id),
                    name: format!("Console session {}", self.id),
                    kind: "repl-session".into(),
                    start_line: 1,
                    end_line: self.source.lines().count(),
                    children: self.nodes.clone(),
                })),
                frame,
                ui_root: root.clone(),
            };
            document.frame.session = self.id;
            document.validate()?;
            work += document.frame.mounts.len().max(1);
            if work > 200_000 {
                bail!("layout dependencies did not stabilize within the rendering work budget");
            }
            self.bridge.paint_frame(
                &mut self.candidate.vm,
                root.as_deref(),
                &mut document.frame,
            )?;
            document.validate()?;
            last = Some(document);
        })();
        if result.is_err() && mutated_mounts {
            self.faulted = true;
        }
        result
    }

    pub fn take_window_commands(&self) -> Result<Vec<crate::window::Command>> {
        self.bridge.take_window_commands(&self.candidate.vm)
    }

    pub fn resize(
        &mut self,
        viewport: Option<crate::layout::Size>,
    ) -> Result<Option<RenderDocument>> {
        if self.faulted {
            bail!("runtime stopped after a callback or rendering failure");
        }
        if !self.bridge.set_viewport(&mut self.candidate.vm, viewport)? {
            return Ok(None);
        }
        let result = self.refresh_document();
        if result.is_err() {
            self.take_window_commands()?;
            self.bridge.discard_pending(&mut self.candidate.vm)?;
        }
        self.bridge
            .reclaim(&mut self.candidate.vm, &mut self.candidate.roots)?;
        result
    }

    pub fn is_faulted(&self) -> bool {
        self.faulted
    }

    pub fn dispatch(&mut self, input: &crate::events::Input) -> Result<ReplResult> {
        if self.faulted {
            bail!("runtime stopped after a callback or rendering failure");
        }
        if input.session != self.id {
            bail!("event belongs to another runtime session");
        }
        let result = (|| {
            self.bridge.dispatch(&mut self.candidate.vm, input)?;
            let document = self.refresh_document()?;
            Ok(ReplResult {
                value: "nil".into(),
                document,
                bindings: self
                    .candidate
                    .vm
                    .dict_items(self.candidate.globals.expect("live globals"))?
                    .len()
                    .saturating_sub(1),
                input: self.inputs,
            })
        })();
        if result.is_err() {
            self.take_window_commands()?;
            self.faulted = true;
            self.bridge.discard_pending(&mut self.candidate.vm)?;
        }
        self.bridge
            .reclaim(&mut self.candidate.vm, &mut self.candidate.roots)?;
        result
    }
}
fn shift_node_lines(node: &mut CodeNode, offset: usize) {
    node.start_line += offset;
    node.end_line += offset;
    for child in &mut node.children {
        shift_node_lines(child, offset);
    }
}
fn value_repr(vm: &Vm, value: &Value) -> Result<String> {
    Ok(match value {
        Value::Nil => "nil".into(),
        Value::Bool(v) => v.to_string(),
        Value::Text(v) => format!("{v:?}"),
        Value::Number(v) => v.to_string(),
        Value::Object(v) => vm.repr(*v)?,
    })
}

struct Candidate {
    vm: Vm,
    roots: Vec<ObjectRef>,
    globals: Option<ObjectRef>,
}

impl Candidate {
    fn new() -> Result<Self> {
        Ok(Self {
            vm: Vm::new()?,
            roots: Vec::new(),
            globals: None,
        })
    }

    fn close(&mut self) -> Result<()> {
        if let Some(globals) = self.globals.take() {
            self.vm.dict_clear(globals)?;
        }
        while let Some(root) = self.roots.pop() {
            self.vm.release(root)?;
        }
        self.vm.collect_cycles();
        if self.vm.object_count() != 0 {
            bail!("candidate VM retained objects after cleanup");
        }
        Ok(())
    }
}

impl Drop for Candidate {
    fn drop(&mut self) {
        // Explicit close reports accounting errors; dropping the fresh VM is
        // also the final cleanup boundary on every early return or unwind.
        let _ = self.close();
    }
}

pub(crate) fn runtime_error(vm: &Vm, error: VmError) -> anyhow::Error {
    let locations = vm
        .last_traceback()
        .iter()
        .map(|frame| {
            format!(
                "{}:{} in {} (instruction {})",
                frame.filename, frame.first_line, frame.function, frame.instruction_offset
            )
        })
        .collect::<Vec<_>>()
        .join("\n");
    if locations.is_empty() {
        error.into()
    } else {
        anyhow::anyhow!("{error}\n{locations}")
    }
}

#[derive(Default)]
struct AstBudget {
    depth: usize,
    nodes: usize,
}

impl Visitor for AstBudget {
    type Error = anyhow::Error;
    fn enter_node(&mut self, _span: Span) -> Result<()> {
        self.depth += 1;
        self.nodes += 1;
        if self.depth > MAX_AST_DEPTH || self.nodes > MAX_AST_NODES {
            bail!("Aster AST exceeds the 64-level or 10000-node host budget");
        }
        Ok(())
    }
    fn leave_node(&mut self) {
        self.depth -= 1;
    }
}

fn architecture(
    source: &SourceUnit,
    plan: &SourcePlan,
    namespace: &str,
    submission: u64,
) -> CodeNode {
    let mut tree = Architecture {
        line_starts: line_starts(source.text()),
        next_id: 0,
        identity: format!("{namespace}@{submission}"),
    };
    let mut children = Vec::new();
    for root in plan.roots() {
        match root {
            AstRoot::Module(program) => children.extend(
                program
                    .declarations
                    .iter()
                    .map(|decl| tree.declaration(decl)),
            ),
            AstRoot::Interactive(input) => {
                children.extend(input.statements.iter().map(|stmt| tree.statement(stmt)))
            }
            AstRoot::Expression(expression) => children.push(tree.expression(expression)),
        }
    }
    let roots = plan.roots();
    let span = Span::new(
        roots.first().map_or(0, |root| root.span().start),
        roots.last().map_or(0, |root| root.span().end),
    );
    let kind = if matches!(plan, SourcePlan::Module(_)) {
        "module"
    } else {
        "script"
    };
    tree.node(namespace.to_owned(), kind, span, children)
}

fn line_starts(source: &str) -> Vec<usize> {
    let bytes = source.as_bytes();
    let mut starts = vec![0];
    for (offset, byte) in bytes.iter().enumerate() {
        if *byte == b'\n' || (*byte == b'\r' && bytes.get(offset + 1) != Some(&b'\n')) {
            starts.push(offset + 1);
        }
    }
    starts
}

struct Architecture {
    line_starts: Vec<usize>,
    next_id: usize,
    identity: String,
}

impl Architecture {
    fn node(&mut self, name: String, kind: &str, span: Span, children: Vec<CodeNode>) -> CodeNode {
        let id = self.next_id;
        self.next_id += 1;
        let line = |offset| self.line_starts.partition_point(|start| *start <= offset);
        CodeNode {
            id: format!("{}:ast-{id}", self.identity),
            name,
            kind: kind.into(),
            start_line: line(span.start),
            end_line: line(span.end.saturating_sub(1).max(span.start)),
            children,
        }
    }

    fn declaration(&mut self, declaration: &Decl) -> CodeNode {
        match &declaration.kind {
            DeclKind::Function(function) => self.function(function),
            DeclKind::Class(class) => {
                let mut children: Vec<_> = class
                    .fields
                    .iter()
                    .map(|field| self.node(field.name.text.clone(), "field", field.span, vec![]))
                    .collect();
                children.extend(class.methods.iter().map(|method| self.function(method)));
                self.node(class.name.text.clone(), "class", class.span, children)
            }
        }
    }

    fn function(&mut self, function: &frontend::ast::Function) -> CodeNode {
        let children = function
            .body
            .statements
            .iter()
            .map(|stmt| self.statement(stmt))
            .collect();
        self.node(
            function.name.text.clone(),
            "function",
            function.span,
            children,
        )
    }

    fn statement(&mut self, statement: &Stmt) -> CodeNode {
        match &statement.kind {
            StmtKind::MemberAssignment(assignment) => {
                let object = self.expression(&assignment.object);
                let value = self.expression(&assignment.value);
                self.node(
                    assignment.name.text.clone(),
                    "member-assign",
                    statement.span,
                    vec![object, value],
                )
            }
            StmtKind::Binding(binding) => {
                let child = self.expression(&binding.value);
                self.node(
                    binding.name.text.clone(),
                    "let",
                    statement.span,
                    vec![child],
                )
            }
            StmtKind::Assignment(assignment) => {
                let child = self.expression(&assignment.value);
                self.node(
                    assignment.name.text.clone(),
                    "assign",
                    statement.span,
                    vec![child],
                )
            }
            StmtKind::Return(returned) => {
                let children = returned
                    .value
                    .iter()
                    .map(|expr| self.expression(expr))
                    .collect();
                self.node("return".into(), "return", statement.span, children)
            }
            StmtKind::Expression(expr) => self.expression(expr),
            StmtKind::Declaration(decl) => self.declaration(decl),
        }
    }

    fn expression(&mut self, expr: &Expr) -> CodeNode {
        let (name, kind, children) = match &expr.kind {
            ExprKind::Name(name) => (name.clone(), "name", vec![]),
            ExprKind::Number(value) => (value.clone(), "number", vec![]),
            ExprKind::String(value) => (value.chars().take(40).collect(), "string", vec![]),
            ExprKind::Symbol(name) => (name.text.clone(), "symbol", vec![]),
            ExprKind::Unary { operand, .. } => {
                ("negate".into(), "unary", vec![self.expression(operand)])
            }
            ExprKind::Binary { left, right, .. } => (
                "binary".into(),
                "binary",
                vec![self.expression(left), self.expression(right)],
            ),
            ExprKind::Member { object, name } => {
                (name.text.clone(), "member", vec![self.expression(object)])
            }
            ExprKind::Call { callee, arguments } => {
                let mut children = vec![self.expression(callee)];
                children.extend(arguments.iter().map(|expr| self.expression(expr)));
                ("call".into(), "call", children)
            }
        };
        self.node(name, kind, expr.span, children)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::document::{NamespaceState, RenderCommand};

    const EXAMPLE: &str = include_str!("../examples/hello.endor");
    const PAGE: &str = include_str!("../examples/page.endor");

    #[test]
    fn managed_window_requests_are_coalesced_and_failed_input_discards_pending_requests() {
        let mut session = ReplSession::new(111).unwrap();
        session
            .execute(
                r#"window = ui.window()
        window.resize(900,600)
        window.resize(1000,700)
        window.setTitle("Endor")
        window.focus()"#,
                "app.main",
            )
            .unwrap();
        let requests = session.take_window_commands().unwrap();
        assert_eq!(requests.len(), 3);
        assert!(matches!(
            requests[0].action,
            crate::window::Action::Resize {
                width: 1000.0,
                height: 700.0
            }
        ));
        assert!(
            matches!(&requests[1].action,crate::window::Action::SetTitle(title) if title=="Endor")
        );
        assert!(session.take_window_commands().unwrap().is_empty());
        assert!(
            session
                .execute("window.resize(1400,900)\nwindow.resize(0,600)", "app.main")
                .is_err()
        );
        assert!(session.take_window_commands().unwrap().is_empty());
        assert!(session.execute("window.resize(0,600)", "app.main").is_err());
        assert!(session.take_window_commands().unwrap().is_empty());
    }

    #[test]
    fn window_page_roots_follow_open_close_and_creation_order() {
        let source = r#"first = Page()
        second = Page()
        first.render(TextBlock("first"))
        second.render(TextBlock("second"))
        window = ui.window()"#;
        let (mut session, _) = ReplSession::load(source, "app.main", 112, 1).unwrap();
        assert_eq!(
            session
                .execute("window.pages().count", "app.main")
                .unwrap()
                .value,
            "2"
        );
        let first = session.execute("first.window()", "app.main").unwrap().value;
        assert_eq!(
            first,
            session
                .execute("second.window()", "app.main")
                .unwrap()
                .value
        );
        session.execute("first.close()", "app.main").unwrap();
        assert_eq!(
            session.execute("first.window()", "app.main").unwrap().value,
            "nil"
        );
        assert_eq!(
            session
                .execute("window.pages().count", "app.main")
                .unwrap()
                .value,
            "1"
        );
        session.execute("first.open(window)", "app.main").unwrap();
        assert_eq!(
            session
                .execute("window.pages().count", "app.main")
                .unwrap()
                .value,
            "2"
        );
        assert_eq!(
            session
                .execute("window.pages().at(0)", "app.main")
                .unwrap()
                .value,
            session.execute("second", "app.main").unwrap().value
        );
        assert!(session.execute("first.open(Object())", "app.main").is_err());
    }

    #[test]
    fn closed_page_is_not_kept_alive_by_window_page_order() {
        let (mut session, _) = ReplSession::load(
            "page = Page()\npage.render(TextBlock(\"page\"))",
            "app.main",
            113,
            1,
        )
        .unwrap();
        let globals = session.candidate.globals.unwrap();
        let Value::Object(page) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text("page".into()))
            .unwrap()
            .unwrap()
        else {
            panic!("Page")
        };
        let weak = session.candidate.vm.downgrade(page).unwrap();
        session.execute("page.close()", "app.main").unwrap();
        session
            .candidate
            .vm
            .dict_delete(globals, &Value::Text("page".into()))
            .unwrap();
        session.candidate.vm.collect_cycles();
        assert!(session.candidate.vm.upgrade(weak).unwrap().is_none());
    }

    #[test]
    fn rendering_cannot_enqueue_native_window_side_effects() {
        let source = r##"class BadRect: RectBlock {
            function measure(self: BadRect, mount: Mount, constraints: Constraints): MeasureResult {
                ui.window().resize(900,600)
                return MeasureResult(80,20)
            }
        }
        page = Page()
        page.render(BadRect(80,20,0,"#DDEEFF"))"##;
        let error = ReplSession::load(source, "app.main", 114, 1).err().unwrap();
        assert!(
            error
                .to_string()
                .contains("window operations are forbidden")
        );
    }

    fn source_measure_stat(session: &mut ReplSession, name: &str) -> i64 {
        let Value::Object(function) = session
            .candidate
            .vm
            .get_attr(session.bridge.ui, "stats")
            .unwrap()
        else {
            panic!("stats function")
        };
        let Value::Object(stats) = session.candidate.vm.call(function, &[]).unwrap() else {
            panic!("stats")
        };
        let Value::Number(value) = session.candidate.vm.get_attr(stats, name).unwrap() else {
            panic!("stat number")
        };
        session.candidate.vm.release(stats).unwrap();
        value.as_i64().unwrap()
    }
    fn click_named(
        session: &mut ReplSession,
        document: &RenderDocument,
        name: &str,
    ) -> RenderDocument {
        let globals = session.candidate.globals.unwrap();
        let Value::Object(block) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text(name.into()))
            .unwrap()
            .unwrap()
        else {
            panic!("Block")
        };
        let mount = document
            .frame
            .mounts
            .iter()
            .find(|mount| mount.block_id == block.to_string())
            .unwrap();
        session
            .dispatch(&crate::events::Input {
                session: session.id,
                layout_version: document.frame.layout_version,
                mount: mount.id,
                kind: "click".into(),
                point: None,
                press_point: None,
            })
            .unwrap()
            .document
            .unwrap()
    }

    #[test]
    fn source_measure_cache_reuses_independent_results_and_invalidates_model_changes() {
        let (mut session, initial) = ReplSession::load_with_viewport(
            include_str!("../examples/layout-cache.endor"),
            "app.main",
            101,
            1,
            Some(crate::layout::Size {
                width: 800.0,
                height: 600.0,
            }),
        )
        .unwrap();
        assert_eq!(source_measure_stat(&mut session, "sourceMeasureMisses"), 2);
        let painted = click_named(&mut session, &initial, "blue");
        assert!(painted.frame.commands.iter().any(
            |command| matches!(command,RenderCommand::RoundedRect {color,..} if color=="#526AC7")
        ));
        assert_eq!(source_measure_stat(&mut session, "sourceMeasureHits"), 2);
        assert_eq!(source_measure_stat(&mut session, "measured"), 0);
        let resized = click_named(&mut session, &painted, "expand");
        assert!(
            resized
                .frame
                .mounts
                .iter()
                .any(|mount| mount.width == 260.0 && mount.height == 60.0)
        );
        assert_eq!(source_measure_stat(&mut session, "sourceMeasureHits"), 1);
        assert_eq!(source_measure_stat(&mut session, "sourceMeasureMisses"), 1);
    }

    #[test]
    fn viewport_updates_in_a_fresh_console_do_not_replace_the_preserved_page() {
        let mut session = ReplSession::new_with_viewport(
            104,
            Some(crate::layout::Size {
                width: 800.0,
                height: 600.0,
            }),
        )
        .unwrap();
        assert!(
            session
                .execute("42", "app.main")
                .unwrap()
                .document
                .is_none()
        );
        assert!(
            session
                .resize(Some(crate::layout::Size {
                    width: 360.0,
                    height: 240.0
                }))
                .unwrap()
                .is_none()
        );
        let result = session.execute("ui.viewport().width", "app.main").unwrap();
        assert_eq!(result.value, "360");
        assert!(result.document.is_none());
    }

    #[test]
    fn source_measure_cache_tracks_fields_of_an_existing_returned_result() {
        let source = r##"class HeldRect: RectBlock {
            result: MeasureResult
            function measure(self: HeldRect, mount: Mount, constraints: Constraints): MeasureResult { return self.result }
        }
        result = MeasureResult(80,20)
        rect = HeldRect(80,20,0,"#DDEEFF",result)
        page = Page()
        page.render(rect)"##;
        let (mut session, initial) = ReplSession::load(source, "app.main", 103, 1).unwrap();
        let id = initial
            .frame
            .mounts
            .iter()
            .find(|mount| mount.width == 80.0)
            .unwrap()
            .id;
        let globals = session.candidate.globals.unwrap();
        let Value::Object(result) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text("result".into()))
            .unwrap()
            .unwrap()
        else {
            panic!("result")
        };
        session
            .candidate
            .vm
            .set_attr(result, "width", Value::Number(140.into()))
            .unwrap();
        let next = session.refresh_document().unwrap().unwrap();
        assert!(
            next.frame
                .mounts
                .iter()
                .any(|mount| mount.id == id && mount.width == 140.0)
        );
        assert_eq!(source_measure_stat(&mut session, "sourceMeasureMisses"), 1);
        assert!(session.refresh_document().unwrap().is_none());
    }

    #[test]
    fn viewport_resize_changes_constraints_and_preserves_mount_identity_without_source_input() {
        let (mut session, initial) = ReplSession::load_with_viewport(
            include_str!("../examples/layout-cache.endor"),
            "app.main",
            102,
            1,
            Some(crate::layout::Size {
                width: 800.0,
                height: 600.0,
            }),
        )
        .unwrap();
        let ids: Vec<_> = initial.frame.mounts.iter().map(|mount| mount.id).collect();
        let document = session
            .resize(Some(crate::layout::Size {
                width: 360.0,
                height: 240.0,
            }))
            .unwrap()
            .unwrap();
        assert_eq!(
            ids,
            document
                .frame
                .mounts
                .iter()
                .map(|mount| mount.id)
                .collect::<Vec<_>>()
        );
        assert!(
            document
                .frame
                .mounts
                .iter()
                .any(|mount| mount.width == 312.0 && mount.height == 24.0)
        );
        assert_eq!(session.inputs, 0);
        assert!(
            session
                .resize(Some(crate::layout::Size {
                    width: 360.0,
                    height: 240.0
                }))
                .unwrap()
                .is_none()
        );
        assert!(
            session
                .resize(Some(crate::layout::Size {
                    width: f32::NAN,
                    height: 240.0
                }))
                .is_err()
        );
        assert!(!session.is_faulted());
    }

    const SOURCE_LAYOUT: &str = include_str!("../examples/source-layout.endor");

    #[test]
    fn source_layout_uses_initial_mount_links_child_measurements_and_model_dependencies() {
        let (mut session, initial) = ReplSession::load(SOURCE_LAYOUT, "app.main", 91, 1).unwrap();
        let rect = initial
            .frame
            .mounts
            .iter()
            .find(|mount| mount.width == 200.0 && mount.height == 60.0)
            .unwrap();
        assert_eq!((rect.x, rect.y), (44.0, 24.0));
        let id = rect.id;
        assert!(initial.frame.commands.iter().any(|command| matches!(command,RenderCommand::Text { value,y,.. } if value.starts_with("尺寸来自") && *y == 100.0)));
        let globals = session.candidate.globals.unwrap();
        let Value::Object(metrics) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text("metrics".into()))
            .unwrap()
            .unwrap()
        else {
            panic!("Metrics")
        };
        session
            .candidate
            .vm
            .set_attr(metrics, "width", Value::Number(260.into()))
            .unwrap();
        let next = session.refresh_document().unwrap().unwrap();
        let rect = next
            .frame
            .mounts
            .iter()
            .find(|mount| mount.id == id)
            .unwrap();
        assert_eq!((rect.x, rect.width), (44.0, 260.0));
        assert!(session.refresh_document().unwrap().is_none());
    }

    #[test]
    fn shared_block_source_measurements_belong_to_each_occurrence() {
        let source = SOURCE_LAYOUT.replace(
            "page.render(root)",
            r#"otherMetrics = Metrics(140, 12)
        other = OffsetColumn(24, 16, rect, otherMetrics)
        page.render(Row(0, 0, root, other))"#,
        );
        let (mut session, initial) = ReplSession::load(&source, "app.main", 92, 1).unwrap();
        let globals = session.candidate.globals.unwrap();
        let Value::Object(rect) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text("rect".into()))
            .unwrap()
            .unwrap()
        else {
            panic!("Rect")
        };
        let widths: Vec<_> = initial
            .frame
            .mounts
            .iter()
            .filter(|mount| mount.block_id == rect.to_string())
            .map(|mount| mount.width)
            .collect();
        assert_eq!(widths, vec![200.0, 140.0]);
        assert!(session.refresh_document().unwrap().is_none());
    }

    #[test]
    fn layout_dependencies_changed_by_mount_hook_are_measured_again_before_publication() {
        let source = r##"class Metrics { width: Number }
        class InitialRect: RectBlock {
            metrics: Metrics
            function measure(self: InitialRect, mount: Mount, constraints: Constraints): MeasureResult {
                return MeasureResult(self.metrics.width, 20)
            }
            function onMount(self: InitialRect, mount: Mount): Unit { self.metrics.width = 140 }
        }
        metrics = Metrics(80)
        rect = InitialRect(80,20,0,"#DDEEFF",metrics)
        page = Page()
        page.render(rect)"##;
        let (mut session, document) = ReplSession::load(source, "app.main", 93, 1).unwrap();
        assert!(
            document
                .frame
                .mounts
                .iter()
                .any(|mount| mount.width == 140.0 && mount.height == 20.0)
        );
        assert!(session.refresh_document().unwrap().is_none());
    }

    #[test]
    fn source_layout_rejects_premature_geometry_writes_wrong_types_and_foreign_slots() {
        for (before, after, message) in [
            (
                "return MeasureResult(parent.block.metrics.width, 60)",
                "return mount.bounds()",
                "geometry is unavailable during measurement",
            ),
            (
                "return MeasureResult(parent.block.metrics.width, 60)",
                "parent.block.metrics.width = 260\nreturn MeasureResult(260,60)",
                "read-only",
            ),
            (
                "return MeasureResult(parent.block.metrics.width, 60)",
                "return Point(0,0)",
                "wrong result type",
            ),
            (
                "positions.children.at(0).x = self.metrics.left",
                "positions.children.at(0).slot = 999999",
                "foreign child slot",
            ),
        ] {
            let source = SOURCE_LAYOUT.replace(before, after);
            let error = ReplSession::load(&source, "app.main", 94, 1).err().unwrap();
            assert!(error.to_string().contains(message), "{error}");
        }
    }

    #[test]
    fn source_hit_filters_shape_falls_back_and_requires_matching_press_release() {
        for (press, release, expected_hits, expected_background) in [
            ([64.0, 64.0], [64.0, 64.0], "1", "0"),
            ([144.0, 64.0], [144.0, 64.0], "0", "1"),
            ([64.0, 64.0], [144.0, 64.0], "0", "0"),
            ([9999.0, 9999.0], [9999.0, 9999.0], "0", "0"),
        ] {
            let (mut session, initial) = ReplSession::load(
                include_str!("../examples/source-hit.endor"),
                "app.main",
                81,
                1,
            )
            .unwrap();
            let circle = initial
                .frame
                .mounts
                .iter()
                .find(|mount| mount.interactive && mount.width == 160.0)
                .unwrap();
            session
                .dispatch(&crate::events::Input {
                    session: 81,
                    layout_version: initial.frame.layout_version,
                    mount: circle.id,
                    kind: "click".into(),
                    point: Some(release),
                    press_point: Some(press),
                })
                .unwrap();
            assert_eq!(
                session.execute("hits.value", "app.main").unwrap().value,
                expected_hits
            );
            assert_eq!(
                session
                    .execute("background.value", "app.main")
                    .unwrap()
                    .value,
                expected_background
            );
        }
    }

    #[test]
    fn source_hit_rejects_wrong_result_and_business_writes_before_callbacks() {
        for (body, message) in [
            ("return 1", "hitTest must return Bool"),
            (
                "self.hits.increment()\nreturn point.inCircle(40, 40, 40)",
                "read-only",
            ),
        ] {
            let source = include_str!("../examples/source-hit.endor")
                .replace("return point.inCircle(40, 40, 40)", body);
            let (mut session, initial) = ReplSession::load(&source, "app.main", 82, 1).unwrap();
            let circle = initial
                .frame
                .mounts
                .iter()
                .find(|mount| mount.interactive && mount.width == 160.0)
                .unwrap();
            let error = session
                .dispatch(&crate::events::Input {
                    session: 82,
                    layout_version: initial.frame.layout_version,
                    mount: circle.id,
                    kind: "click".into(),
                    point: Some([64.0, 64.0]),
                    press_point: Some([64.0, 64.0]),
                })
                .err()
                .unwrap();
            assert!(error.to_string().contains(message), "{error}");
            assert!(session.is_faulted());
            let globals = session.candidate.globals.unwrap();
            let Value::Object(hits) = session
                .candidate
                .vm
                .dict_get(globals, &Value::Text("hits".into()))
                .unwrap()
                .unwrap()
            else {
                panic!("state")
            };
            assert_eq!(
                session.candidate.vm.get_attr(hits, "value").unwrap(),
                Value::Number(0.into())
            );
        }
    }

    #[test]
    fn ordinary_block_subscription_updates_interactivity_after_disconnect() {
        let source = r##"hits = ui.state(0)
        rect = RectBlock(80, 40, 0, "#DDEEFF")
        token = rect.on("click", hits.increment)
        page = Page()
        page.render(rect)"##;
        let (mut session, initial) = ReplSession::load(source, "app.main", 83, 1).unwrap();
        assert!(initial.frame.mounts.iter().any(|mount| mount.interactive));
        let result = session.execute("token.disconnect()", "app.main").unwrap();
        assert!(
            result
                .document
                .unwrap()
                .frame
                .mounts
                .iter()
                .all(|mount| !mount.interactive)
        );
    }

    #[test]
    fn source_paint_can_rebind_old_plain_reference_to_new_result_without_mutating_it() {
        let source = r##"class ReboundRect: RectBlock {
            previous: ObjectList
            function paint(self: ReboundRect, mount: Mount, geometry: Bounds): DisplayList {
                drawing = self.previous
                drawing = RectBlock.paint(self, mount, geometry)
                return drawing
            }
        }
        previous = ObjectList()
        rect = ReboundRect(80, 40, 0, "#DDEEFF", previous)
        page = Page()
        page.render(rect)"##;
        let (mut session, document) = ReplSession::load(source, "app.main", 75, 1).unwrap();
        assert_eq!(document.frame.commands.len(), 1);
        assert_eq!(
            session.execute("previous.count", "app.main").unwrap().value,
            "0"
        );
    }

    #[test]
    fn source_paint_overrides_native_commands_and_reacts_to_heap_field_writes() {
        let (mut session, initial) = ReplSession::load(
            include_str!("../examples/source-paint.endor"),
            "app.main",
            71,
            1,
        )
        .unwrap();
        initial.validate().unwrap();
        assert_eq!(initial.frame.commands.iter().filter(|command| matches!(command, RenderCommand::RoundedRect { color, .. } if color == "#ED6A5A")).count(), 2);
        assert!(initial.frame.commands.iter().any(
            |command| matches!(command, RenderCommand::Text { color, .. } if color == "#FFFFFF")
        ));
        let globals = session.candidate.globals.unwrap();
        let Value::Object(rect) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text("rect".into()))
            .unwrap()
            .unwrap()
        else {
            panic!("Block")
        };
        // No Console/global binding writes or focus changes: only the property
        // read by paint changes, proving the paint dependency is sufficient.
        session
            .candidate
            .vm
            .set_attr(rect, "tint", Value::Text("#526AC7".into()))
            .unwrap();
        let updated = session.refresh_document().unwrap().unwrap();
        assert_eq!(updated.frame.commands.iter().filter(|command| matches!(command, RenderCommand::RoundedRect { color, .. } if color == "#526AC7")).count(), 2);
        assert!(session.refresh_document().unwrap().is_none());
    }

    #[test]
    fn source_paint_rejects_business_mutation_before_it_happens_and_restores_scope() {
        let source = r##"class BadPaint: RectBlock {
            tint: String
            function paint(self: BadPaint, mount: Mount, geometry: Bounds): DisplayList {
                self.tint = "#000000"
                return RectBlock.paint(self, mount, geometry)
            }
        }
        rect = BadPaint(100, 40, 0, "#DDEEFF", "#FF0000")
        page = Page()
        page.render(rect)"##;
        let mut session = ReplSession::new(72).unwrap();
        assert!(
            session
                .execute(source, "app.main")
                .err()
                .unwrap()
                .to_string()
                .contains("read-only")
        );
        assert!(session.is_faulted());
        let globals = session.candidate.globals.unwrap();
        let Value::Object(rect) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text("rect".into()))
            .unwrap()
            .unwrap()
        else {
            panic!("Block")
        };
        assert_eq!(
            session.candidate.vm.get_attr(rect, "tint").unwrap(),
            Value::Text("#FF0000".into())
        );
        session
            .candidate
            .vm
            .set_attr(rect, "tint", Value::Text("#526AC7".into()))
            .unwrap();
        let bad_color =
            include_str!("../examples/source-paint.endor").replace("#ED6A5A", "invalid color");
        assert!(ReplSession::load(&bad_color, "app.main", 73, 1).is_err());
    }

    #[test]
    fn source_paint_is_stable_when_mount_notifications_overflow_the_change_batch() {
        let fixture = include_str!("../examples/source-paint.endor");
        let mut source = fixture[..fixture.find("root = Column").unwrap()].to_owned();
        source.push_str("root = Column(0, 0");
        for _ in 0..1100 {
            source.push_str(", rect");
        }
        source.push_str(")\npage = Page()\npage.render(root)");
        let (mut session, document) = ReplSession::load(&source, "app.main", 74, 1).unwrap();
        assert_eq!(document.frame.commands.len(), 1100);
        assert!(session.refresh_document().unwrap().is_none());
    }

    #[test]
    fn native_visual_methods_use_managed_values_and_match_real_geometry() {
        let (mut session, initial) = ReplSession::load(
            include_str!("../examples/visual-protocols.endor"),
            "app.main",
            61,
            1,
        )
        .unwrap();
        initial.validate().unwrap();
        for (expression, expected) in [
            ("results.width", "120"),
            ("results.height", "60"),
            ("results.childX", "44"),
            ("results.childY", "54"),
            ("results.color", "\"#DDEEFF\""),
        ] {
            assert_eq!(
                session.execute(expression, "app.main").unwrap().value,
                expected
            );
        }
        assert!(initial.frame.commands.iter().any(|command| matches!(command, RenderCommand::RoundedRect { width: 200.0, height: 60.0, color, .. } if color == "#DDEEFF")));
        session
            .execute("context = rect.mounts().at(0)", "app.main")
            .unwrap();
        assert_eq!(
            session
                .execute("rect.hitTest(context, Point(1, 1))", "app.main")
                .unwrap()
                .value,
            "true"
        );
        assert_eq!(
            session
                .execute("rect.hitTest(context, Point(-1, 1))", "app.main")
                .unwrap()
                .value,
            "false"
        );
        assert!(
            session
                .execute(
                    "rect.measure(context, Constraints(200, 0, 100, 100))",
                    "app.main"
                )
                .is_err()
        );
        assert!(
            session
                .execute("root.paint(context, Bounds(0, 0, 10, 10))", "app.main")
                .is_err()
        );
        session.execute("page.close()", "app.main").unwrap();
        assert!(
            session
                .execute("rect.paint(context, Bounds(0, 0, 10, 10))", "app.main")
                .is_err()
        );
    }

    #[test]
    fn explicit_invalidation_publishes_once_preserves_mount_and_remeasures_only_when_requested() {
        let (mut session, _) = ReplSession::load(
            include_str!("../examples/visual-protocols.endor"),
            "app.main",
            62,
            1,
        )
        .unwrap();
        session
            .execute("context = rect.mounts().at(0)", "app.main")
            .unwrap();
        let original = session.execute("context", "app.main").unwrap().value;
        let update = session
            .execute("rect.invalidate(\"paint\")", "app.main")
            .unwrap()
            .document
            .unwrap();
        update.validate().unwrap();
        assert_eq!(
            session
                .execute("ui.stats().measured", "app.main")
                .unwrap()
                .value,
            "0"
        );
        assert!(
            session
                .execute("rect.invalidate(\"layout\")", "app.main")
                .unwrap()
                .document
                .is_some()
        );
        assert_eq!(
            session
                .execute("ui.stats().measured", "app.main")
                .unwrap()
                .value,
            "1"
        );
        assert_eq!(
            session
                .execute("rect.mounts().at(0)", "app.main")
                .unwrap()
                .value,
            original
        );
        assert!(
            session
                .execute("results.width", "app.main")
                .unwrap()
                .document
                .is_none()
        );
        assert!(
            session
                .execute("rect.invalidate(\"unknown\")", "app.main")
                .is_err()
        );
    }

    #[test]
    fn mount_hooks_run_per_occurrence_settle_and_unmount_before_parent() {
        let (mut session, initial) = ReplSession::load(
            include_str!("../examples/mount-lifecycle.endor"),
            "app.main",
            51,
            1,
        )
        .unwrap();
        initial.validate().unwrap();
        for (expression, expected) in [
            ("log.mounted.value", "2"),
            ("log.parentMounted", "1"),
            ("log.childMounted", "3"),
        ] {
            assert_eq!(
                session.execute(expression, "app.main").unwrap().value,
                expected
            );
        }
        session
            .execute(
                "saved = child.mounts().at(0)\nchild.setColor(\"#237A45\")",
                "app.main",
            )
            .unwrap();
        assert_eq!(
            session
                .execute("log.mounted.value", "app.main")
                .unwrap()
                .value,
            "2"
        );
        let closed = session
            .execute("page.close()", "app.main")
            .unwrap()
            .document
            .unwrap();
        assert!(closed.frame.mounts.is_empty());
        assert_eq!(
            session
                .execute("log.unmounted.value", "app.main")
                .unwrap()
                .value,
            "2"
        );
        assert_eq!(
            session
                .execute("log.childUnmounted", "app.main")
                .unwrap()
                .value,
            "5"
        );
        assert_eq!(
            session
                .execute("log.parentUnmounted", "app.main")
                .unwrap()
                .value,
            "6"
        );
        assert_eq!(
            session.execute("saved.mounted", "app.main").unwrap().value,
            "false"
        );
        assert!(session.execute("saved.bounds()", "app.main").is_err());
        session.execute("page.open()", "app.main").unwrap();
        assert_eq!(
            session
                .execute("log.mounted.value", "app.main")
                .unwrap()
                .value,
            "4"
        );
        assert_eq!(
            session.execute("saved.mounted", "app.main").unwrap().value,
            "false"
        );
    }

    #[test]
    fn page_switch_replaces_mount_context_even_for_shared_root() {
        let (mut session, _) = ReplSession::load(
            include_str!("../examples/mount-lifecycle.endor"),
            "app.main",
            52,
            1,
        )
        .unwrap();
        session
            .execute(
                "saved = child.mounts().at(0)\nsecond = Page()\nsecond.render(root)",
                "app.main",
            )
            .unwrap();
        assert_eq!(
            session
                .execute("log.mounted.value", "app.main")
                .unwrap()
                .value,
            "4"
        );
        assert_eq!(
            session
                .execute("log.unmounted.value", "app.main")
                .unwrap()
                .value,
            "2"
        );
        assert_eq!(
            session.execute("saved.mounted", "app.main").unwrap().value,
            "false"
        );
        assert_eq!(
            session
                .execute("child.mounts().at(0).page()", "app.main")
                .unwrap()
                .value,
            session.execute("second", "app.main").unwrap().value
        );
        session.execute("page.activate()", "app.main").unwrap();
        assert_eq!(
            session
                .execute("log.mounted.value", "app.main")
                .unwrap()
                .value,
            "6"
        );
    }

    #[test]
    fn lifecycle_hook_can_edit_container_without_session_lock_and_failure_stops_domain() {
        let source = r#"class GrowingColumn: Column {
            function onMount(self: GrowingColumn, mount: Mount): Unit { self.append(TextBlock("from hook")) }
        }
        root = GrowingColumn(0, 0)
        page = Page()
        page.render(root)"#;
        let (_, document) = ReplSession::load(source, "app.main", 53, 1).unwrap();
        assert!(document.frame.commands.iter().any(
            |command| matches!(command, RenderCommand::Text { value, .. } if value == "from hook")
        ));
        let mut session = ReplSession::new(54).unwrap();
        let source = r#"class BrokenText: TextBlock {
            function onMount(self: BrokenText, mount: Mount): Unit { self.setText(1) }
        }
        page = Page()
        page.render(BrokenText("x"))"#;
        assert!(session.execute(source, "app.main").is_err());
        assert!(session.is_faulted());
    }

    fn event_session(extra: &str) -> (ReplSession, RenderDocument) {
        let source = format!("{}\n{}", include_str!("../examples/events.endor"), extra);
        ReplSession::load(&source, "app.main", 41, 1).unwrap()
    }

    fn click_document(session: &mut ReplSession, document: &RenderDocument) -> RenderDocument {
        let globals = session.candidate.globals.unwrap();
        let Value::Object(button) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text("button".into()))
            .unwrap()
            .unwrap()
        else {
            panic!("Button")
        };
        let mount = document
            .frame
            .mounts
            .iter()
            .find(|mount| mount.interactive && mount.block_id == button.to_string())
            .unwrap();
        session
            .dispatch(&crate::events::Input {
                session: 41,
                layout_version: document.frame.layout_version,
                mount: mount.id,
                kind: "click".into(),
                point: None,
                press_point: None,
            })
            .unwrap()
            .document
            .unwrap()
    }

    #[test]
    fn managed_event_route_orders_capture_method_listeners_and_bubble() {
        let (mut session, initial) = event_session("");
        click_document(&mut session, &initial).validate().unwrap();
        for (field, expected) in [
            ("captureStep", "1"),
            ("methodStep", "2"),
            ("targetStep", "3"),
            ("bubbleStep", "4"),
        ] {
            assert_eq!(
                session
                    .execute(&format!("model.{field}"), "app.main")
                    .unwrap()
                    .value,
                expected
            );
        }
        assert_eq!(
            session.execute("model.phase", "app.main").unwrap().value,
            "\"bubble\""
        );
        assert_eq!(
            session
                .execute("target.isConnected()", "app.main")
                .unwrap()
                .value,
            "true"
        );
    }

    #[test]
    fn disconnect_during_capture_skips_pending_listener_and_stop_preserves_current_group() {
        let (mut session, initial) = event_session(
            "function cancel(event: Event): Unit { target.disconnect() }\nconnection = root.on(\"click\", cancel, \"capture\")",
        );
        click_document(&mut session, &initial);
        assert_eq!(
            session
                .execute("model.targetStep", "app.main")
                .unwrap()
                .value,
            "0"
        );
        assert_eq!(
            session
                .execute("model.bubbleStep", "app.main")
                .unwrap()
                .value,
            "3"
        );
        assert_eq!(
            session
                .execute("target.isConnected()", "app.main")
                .unwrap()
                .value,
            "false"
        );
        let (mut session, initial) = event_session(
            "function stop(event: Event): Unit { event.stopPropagation() }\nconnection = button.on(\"click\", stop, \"capture\")",
        );
        click_document(&mut session, &initial);
        assert_eq!(
            session
                .execute("model.targetStep", "app.main")
                .unwrap()
                .value,
            "3"
        );
        assert_eq!(
            session
                .execute("model.bubbleStep", "app.main")
                .unwrap()
                .value,
            "0"
        );
    }

    #[test]
    fn immediate_stop_skips_target_method_and_code_dispatch_returns_cancelled_event() {
        let (mut session, initial) = event_session(
            "function stop(event: Event): Unit { event.stopImmediatePropagation() }\nconnection = button.on(\"click\", stop, \"capture\")",
        );
        click_document(&mut session, &initial);
        assert_eq!(
            session
                .execute("model.count.value", "app.main")
                .unwrap()
                .value,
            "1"
        );
        let (mut session, _) = event_session(
            "function prevent(event: Event): Unit { event.preventDefault() }\nconnection = button.on(\"custom\", prevent)\nresult = button.dispatch(Event(\"custom\"))",
        );
        assert_eq!(
            session
                .execute("result.isDefaultPrevented()", "app.main")
                .unwrap()
                .value,
            "true"
        );
        assert_eq!(
            session.execute("result.phase", "app.main").unwrap().value,
            "\"none\""
        );
        // Reusing a completed event is legal; its previous dispatch has no live guard.
        session
            .execute("button.dispatch(result)", "app.main")
            .unwrap();
    }

    #[test]
    fn event_failure_releases_dispatch_guard_and_token_does_not_retain_target() {
        let (mut session, _) = event_session("");
        session.execute("function fail(event: Event): Unit { page.render(1) }\nfailing = button.on(\"failure\", fail)\nfailedEvent = Event(\"failure\")", "app.main").unwrap();
        assert!(
            session
                .execute("button.dispatch(failedEvent)", "app.main")
                .is_err()
        );
        session
            .execute(
                "failing.disconnect()\nbutton.dispatch(failedEvent)",
                "app.main",
            )
            .unwrap();
        session
            .execute(
                "orphan = Button(\"unmounted\")\ntoken = orphan.on(\"click\", model.target)",
                "app.main",
            )
            .unwrap();
        let globals = session.candidate.globals.unwrap();
        let Value::Object(orphan) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text("orphan".into()))
            .unwrap()
            .unwrap()
        else {
            panic!("Block expected")
        };
        let weak = session.candidate.vm.downgrade(orphan).unwrap();
        session
            .candidate
            .vm
            .dict_delete(globals, &Value::Text("orphan".into()))
            .unwrap();
        session
            .bridge
            .reclaim(&mut session.candidate.vm, &mut session.candidate.roots)
            .unwrap();
        assert!(session.candidate.vm.upgrade(weak).unwrap().is_none());
        assert_eq!(
            session
                .execute("token.isConnected()", "app.main")
                .unwrap()
                .value,
            "false"
        );
    }

    #[test]
    fn source_native_subclasses_share_live_fields_and_release_replaced_storage() {
        let (mut session, initial) = ReplSession::load(
            include_str!("../examples/native-subclasses.endor"),
            "app.main",
            31,
            1,
        )
        .unwrap();
        initial.validate().unwrap();
        assert_eq!(
            session
                .execute("isInstance(label, TextBlock)", "app.main")
                .unwrap()
                .value,
            "true"
        );
        assert_eq!(
            session
                .execute("isInstance(page, Page)", "app.main")
                .unwrap()
                .value,
            "true"
        );
        session.execute("alias = label", "app.main").unwrap();
        let globals = session.candidate.globals.unwrap();
        let Value::Object(label) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text("label".into()))
            .unwrap()
            .unwrap()
        else {
            panic!("Block expected")
        };
        let path = session
            .candidate
            .vm
            .object_store()
            .attribute_path(label)
            .unwrap();
        let previous = session
            .candidate
            .vm
            .downgrade(*path.last().unwrap())
            .unwrap();
        let updated = session
            .execute(
                r##"label = CustomStatus("replacement", 2, "#242422", "#237A45", "new field")"##,
                "app.main",
            )
            .unwrap()
            .document
            .unwrap();
        assert!(updated.frame.commands.iter().any(
            |command| matches!(command, RenderCommand::Text { value, .. } if value == "new field")
        ));
        session
            .bridge
            .reclaim(&mut session.candidate.vm, &mut session.candidate.roots)
            .unwrap();
        assert!(session.candidate.vm.upgrade(previous).unwrap().is_none());
        assert_eq!(
            session.execute("alias.message", "app.main").unwrap().value,
            "\"new field\""
        );
        let updated = session
            .execute("button.click()", "app.main")
            .unwrap()
            .document
            .unwrap();
        assert_eq!(updated.frame.commands.iter().filter(|command| matches!(command, RenderCommand::Text { value, .. } if value == "new field")).count(), 3);
        let updated = session
            .execute("alias.message = \"changed field\"", "app.main")
            .unwrap()
            .document
            .unwrap();
        assert!(updated.frame.commands.iter().any(|command| matches!(command, RenderCommand::Text { value, .. } if value == "changed field")));
    }

    #[test]
    fn loaded_program_console_and_native_events_share_unique_source_ids() {
        let (mut session, initial) = ReplSession::load(
            include_str!("../examples/managed-types.endor"),
            "app.main",
            1,
            1,
        )
        .unwrap();
        initial.validate().unwrap();
        assert_eq!(
            session
                .execute("isInstance(page, Block)", "app.main")
                .unwrap()
                .value,
            "true"
        );
        let mount = initial
            .frame
            .mounts
            .iter()
            .find(|mount| mount.interactive)
            .unwrap();
        let event = crate::events::Input {
            session: 1,
            layout_version: initial.frame.layout_version,
            mount: mount.id,
            kind: "click".into(),
            point: None,
            press_point: None,
        };
        let updated = session.dispatch(&event).unwrap().document.unwrap();
        updated.validate().unwrap();
        assert_eq!(
            updated
                .frame
                .commands
                .iter()
                .filter(|command| matches!(command,
                    RenderCommand::Text { value, .. } if value == "10"
                ))
                .count(),
            2
        );
        assert!(!session.is_faulted());
    }

    #[test]
    fn native_method_callbacks_update_two_explicit_bindings() {
        let mut session = ReplSession::new(21).unwrap();
        session.execute("counter = ui.state(9)\nfirst = ui.textOf(counter, \"value\")\nsecond = ui.textOf(counter, \"value\")\nbutton = ui.button(\"increment\")\nfunction increment(): Unit { counter.increment() }\nbutton.onClick(increment)\npage = ui.page()\npage.render(ui.row(0, 8, first, second, button))", "app.main").unwrap();
        let updated = session
            .execute("button.click()", "app.main")
            .unwrap()
            .document
            .unwrap();
        let texts: Vec<_> = updated
            .frame
            .commands
            .iter()
            .filter_map(|command| match command {
                RenderCommand::Text { value, .. } => Some(value.as_str()),
                _ => None,
            })
            .collect();
        assert_eq!(&texts[..2], &["10", "10"]);
    }

    #[test]
    fn closing_a_page_releases_its_root_without_retaining_it_through_shared_content() {
        let mut session = ReplSession::new(22).unwrap();
        session
            .execute(
                "card = ui.rect(10, 20)\npage = ui.page()\npage.render(card)",
                "app.main",
            )
            .unwrap();
        let globals = session.candidate.globals.unwrap();
        let Value::Object(page) = session
            .candidate
            .vm
            .dict_get(globals, &Value::Text("page".into()))
            .unwrap()
            .unwrap()
        else {
            panic!("expected Page")
        };
        let weak = session.candidate.vm.downgrade(page).unwrap();
        session.execute("page.close()", "app.main").unwrap();
        session
            .execute("card.setColor(\"#FFEEDD\")", "app.main")
            .unwrap();
        assert!(
            session
                .execute("page.open()", "app.main")
                .unwrap()
                .document
                .is_some()
        );
        session.execute("page.close()", "app.main").unwrap();
        session
            .candidate
            .vm
            .dict_delete(globals, &Value::Text("page".into()))
            .unwrap();
        session
            .bridge
            .reclaim(&mut session.candidate.vm, &mut session.candidate.roots)
            .unwrap();
        assert!(session.candidate.vm.upgrade(weak).unwrap().is_none());
        assert!(
            session
                .candidate
                .vm
                .dict_get(globals, &Value::Text("card".into()))
                .unwrap()
                .is_some()
        );
    }

    #[test]
    fn mounted_aliases_update_nested_positions_unmount_and_reject_cycles() {
        let mut session = ReplSession::new(10).unwrap();
        session.execute("card = ui.rect(10, 20)\nother = card\ncontainer = ui.column(0, 0, other)\npage = ui.page()\npage.render(container)", "app.main").unwrap();
        let identity = session.execute("other", "app.main").unwrap().value;
        let updated = session
            .execute("card = ui.rect(640, 200, 32)", "app.main")
            .unwrap();
        assert_eq!(updated.value, identity);
        assert_eq!(
            session.execute("other", "app.main").unwrap().value,
            identity
        );
        let frame = updated.document.unwrap().frame;
        assert!(matches!(
            frame.commands[0],
            RenderCommand::RoundedRect {
                width: 640.0,
                height: 200.0,
                ..
            }
        ));
        assert!(
            session
                .execute("card = ui.column(0, 0, other)", "app.main")
                .is_err()
        );
        assert!(
            session
                .execute("other", "app.main")
                .unwrap()
                .document
                .is_none()
        );
        let unmounted = session
            .execute("page.unmount()", "app.main")
            .unwrap()
            .document
            .unwrap();
        assert!(unmounted.frame.commands.is_empty());
        assert!(
            session
                .execute("card = ui.rect(80, 50)", "app.main")
                .unwrap()
                .document
                .is_none()
        );
        let remounted = session
            .execute("page.render(other)", "app.main")
            .unwrap()
            .document
            .unwrap();
        assert!(matches!(
            remounted.frame.commands[0],
            RenderCommand::RoundedRect {
                width: 80.0,
                height: 50.0,
                ..
            }
        ));
    }

    #[test]
    fn live_session_retains_objects_and_updates_only_after_mounting() {
        let mut session = ReplSession::new(7).unwrap();
        let created = session
            .execute(
                r##"title = ui.text("你好，Tessera", 2, "#243047")"##,
                "app.main",
            )
            .unwrap();
        assert!(created.document.is_none());
        assert_eq!(
            session.execute("title", "app.main").unwrap().value,
            created.value
        );
        assert_eq!(
            session.execute("_", "app.main").unwrap().value,
            created.value
        );
        let rendered = session
            .execute("page = ui.page()\npage.render(title)", "app.main")
            .unwrap()
            .document
            .unwrap();
        assert!(
            matches!(&rendered.frame.commands[0], RenderCommand::Text { value, .. } if value == "你好，Tessera")
        );
        assert_eq!(rendered.root.as_ref().unwrap().kind, "repl-session");
        assert!(
            session
                .execute(r#"title = ui.text("changed")"#, "app.main")
                .unwrap()
                .document
                .is_some()
        );
        let updated = session
            .execute("page.render(title)", "app.main")
            .unwrap()
            .document
            .unwrap();
        assert!(
            matches!(&updated.frame.commands[0], RenderCommand::Text { value, .. } if value == "changed")
        );
        assert!(updated.source.contains("// Console input 6"));
        assert!(
            session
                .execute("title", "app.main")
                .unwrap()
                .document
                .is_none()
        );
    }

    #[test]
    fn live_session_compiles_before_execution_and_discards_failed_render() {
        let mut session = ReplSession::new(8).unwrap();
        session
            .execute("value = 1\npage = ui.page()", "app.main")
            .unwrap();
        assert!(session.execute("value = 2\nmissing", "app.main").is_err());
        assert_eq!(session.execute("value", "app.main").unwrap().value, "1");
        assert!(
            session
                .execute(
                    "value = 3\npage.render(ui.text(\"discarded\"))\nui.rect(-1, 1, 0)",
                    "app.main"
                )
                .is_err()
        );
        let retained = session.execute("value", "app.main").unwrap();
        assert_eq!(retained.value, "3");
        assert!(retained.document.is_none());
        session.execute("function local(value: Number): Number { result = value result = 42 return result }", "app.main").unwrap();
        assert_eq!(
            session.execute("local(40)", "app.main").unwrap().value,
            "42"
        );
    }

    #[test]
    fn top_level_goal_script_renders_without_a_main_or_synthetic_wrapper() {
        let document = compile(PAGE, "app.main", 9).unwrap();
        assert_eq!(document.source, PAGE);
        let tree = document.root.as_ref().unwrap();
        assert_eq!(tree.kind, "script");
        assert_eq!(tree.children.len(), 4);
        assert_eq!(tree.children[0].name, "heading");
        assert_eq!(tree.children[1].name, "rectangle");
        assert_eq!(tree.children[2].name, "myui");
        assert_eq!(tree.children[2].start_line, 3);
        assert_eq!(tree.children[3].start_line, 4);
        assert!(tree.id.contains("app.main@9"));
        assert_eq!(document.frame.commands.len(), 2);
        assert!(
            matches!(&document.frame.commands[0], RenderCommand::Text { value, size: 2, x: 24.0, y: 24.0, .. } if value == "Hello Endor")
        );
        assert!(
            matches!(&document.frame.commands[1], RenderCommand::RoundedRect { x: 24.0, y: 76.0, width: 240.0, height: 80.0, radius: 12.0, color } if color == "#DCE8FF")
        );
        assert_eq!(document.display_list(2.0).unwrap().commands().len(), 3);
        let wrapped = compile(include_str!("../examples/main.endor"), "app.main", 10).unwrap();
        assert_eq!(
            serde_json::to_value(&document.frame.commands).unwrap(),
            serde_json::to_value(&wrapped.frame.commands).unwrap()
        );
        // Separate VM instances render the same commands with independent
        // managed object identities and presentation contexts.
        assert_ne!(
            document.frame.mounts[0].block_id,
            wrapped.frame.mounts[0].block_id
        );
    }

    #[test]
    fn script_helpers_multiline_bindings_calls_and_member_continuations_use_aster() {
        let source = r##"let color = "#242422" // comment with ( and )
function greeting(): Text {
    return "Hello Endor"
}
function heading(value: Text): View {
    return ui.text(value, 2, color)
}
let title =
    heading(greeting())
let rectangle = ui.rect(
    240, 80, 12,
    "#DCE8FF"
)
let page = ui
    .page()
page
    .render(ui.column(24, 12, title, rectangle))
"##;
        let document = compile(source, "app.main", 2).unwrap();
        assert_eq!(document.frame.commands.len(), 2);
        let tree = document.root.unwrap();
        assert_eq!(tree.children[1].name, "greeting");
        assert_eq!(tree.children[1].start_line, 2);
        assert_eq!(tree.children[2].name, "heading");
        assert_eq!(tree.children[2].start_line, 5);
        assert_eq!(tree.children[3].start_line, 8);
        assert_eq!(tree.children[3].end_line, 9);
        assert_eq!(tree.children.last().unwrap().end_line, 17);
    }

    #[test]
    fn script_diagnostics_refer_to_original_unicode_source_and_byte_ranges() {
        for ending in ["\n", "\r\n", "\r"] {
            let source = format!(
                "let title = ui.text(\"中文\"){ending}// comment{ending}let broken = missing{ending}ui.page().render(title)"
            );
            let error = compile(&source, "app.main", 27).unwrap_err();
            let diagnostic = error.downcast_ref::<frontend::SourceDiagnostic>().unwrap();
            assert_eq!(diagnostic.location.line, 3);
            assert_eq!(diagnostic.location.column, 14);
            assert_eq!(diagnostic.diagnostic.span.slice(&source), Some("missing"));
            assert!(diagnostic.origin.to_string().contains("submission 27"));
        }
        let error = compile("let page = ui.page()\npage.render(,)", "app.main", 1).unwrap_err();
        let diagnostic = error.downcast_ref::<frontend::SourceDiagnostic>().unwrap();
        assert_eq!(diagnostic.location.line, 2);
    }

    #[test]
    fn pages_bind_render_methods_and_last_render_selects_the_snapshot() {
        let source = r#"let first = ui.page()
let second = ui.page()
first.render(ui.text("first"))
second.render(ui.text("second"))
let paint = first.render
paint(ui.text("last"))"#;
        let document = compile(source, "app.main", 1).unwrap();
        assert_eq!(document.frame.commands.len(), 1);
        assert!(
            matches!(&document.frame.commands[0], RenderCommand::Text { value, .. } if value == "last")
        );
    }

    #[test]
    fn page_api_errors_and_late_failures_do_not_publish_partial_snapshots() {
        let mut state = NamespaceState {
            submission: 1,
            ..NamespaceState::default()
        };
        state
            .commit(1, compile(PAGE, "app.main", 1).unwrap())
            .unwrap();
        for source in [
            "ui.page()",
            "let title = ui.text(\"no render\")",
            "let page = ui.page(1)\npage.render(ui.text(\"x\"))",
            "let page = ui.page()\npage.render()",
            "let page = ui.page()\npage.render(\"not a node\")",
            "let page = ui.page()\npage.render(ui.text(\"partial\"))\nui.missing()",
        ] {
            state.submission = state.next_submission().unwrap();
            assert!(
                compile(source, "app.main", state.submission).is_err(),
                "{source}"
            );
            assert_eq!(state.document.source, PAGE);
            assert_eq!(state.revision, 1);
        }
    }

    #[test]
    fn page_creation_has_a_separate_live_object_budget() {
        let mut source = String::new();
        for index in 0..=ui_bridge::MAX_PAGES {
            source.push_str(&format!("let page{index} = ui.page()\n"));
        }
        source.push_str("page0.render(ui.text(\"x\"))");
        let error = compile(&source, "app.main", 1).unwrap_err();
        assert!(error.to_string().contains("64 page budget"), "{error:#}");
    }

    #[test]
    fn script_execution_is_limited_even_without_creating_ui_nodes() {
        let mut source = "function text0(): Text { return \"Hello Endor\" }\n".to_owned();
        for index in 1..=16 {
            source.push_str(&format!(
                "function text{index}(): Text {{ let unused = text{}() return text{}() }}\n",
                index - 1,
                index - 1
            ));
        }
        source.push_str("let title = ui.text(text16())\nui.page().render(title)");
        let error = compile(&source, "app.main", 1).unwrap_err();
        assert!(
            error
                .to_string()
                .contains("execution limit reached: instructions"),
            "{error:#}"
        );
    }

    #[test]
    fn literal_string_return_from_aster_can_be_displayed_by_the_host() {
        let source = "function main(): Text { return \"Hello Endor\" }\nlet title = ui.text(main())\nui.page().render(title)";
        let document = compile(source, "app.main", 1).unwrap();
        assert!(
            matches!(&document.frame.commands[0], RenderCommand::Text { value, .. } if value == "Hello Endor")
        );
    }

    #[test]
    fn developer_selection_resets_to_the_new_source_snapshot() {
        let first = compile(PAGE, "app.main", 1).unwrap();
        let second = compile(PAGE, "app.main", 2).unwrap();
        let mut tools = crate::developer_tools::DeveloperToolsState::default();
        tools.open = true;
        tools.selected_node_id = Some(first.root.as_ref().unwrap().children[0].id.clone());
        tools.document_updated(&second);
        assert_eq!(
            tools.selected_node_id.as_deref(),
            Some(second.root.as_ref().unwrap().id.as_str())
        );
    }

    #[test]
    fn executes_aster_functions_and_renders_after_vm_cleanup() {
        let document = compile(EXAMPLE, "app.main", 1).unwrap();
        assert_eq!(document.source, EXAMPLE);
        let tree = document.root.as_ref().unwrap();
        assert_eq!(tree.kind, "module");
        assert_eq!(tree.name, "app.main");
        assert_eq!(tree.children[0].name, "heading");
        assert_eq!(tree.children[1].name, "main");
        assert_eq!(tree.children[1].start_line, 5);
        assert_eq!(document.frame.commands.len(), 4);
        assert!(
            matches!(&document.frame.commands[0], RenderCommand::Text { value, size: 2, x: 24.0, y: 24.0, .. } if value == "Hello Endor")
        );
        assert!(matches!(
            &document.frame.commands[1],
            RenderCommand::RoundedRect {
                x: 24.0,
                y: 76.0,
                width: 240.0,
                height: 80.0,
                ..
            }
        ));
        let first_width = crate::text::measure("Aster VM", crate::text::TextStyle::ui(1)).width;
        assert!(matches!(
            &document.frame.commands[3],
            RenderCommand::Text { x, y: 168.0, .. } if (*x - (24.0 + first_width + 12.0 + 8.0 + 12.0)).abs() < 0.01
        ));
        // Candidate::close already proved zero remaining VM objects. Both
        // redraws must still work from native data at different display scales.
        assert_eq!(document.display_list(1.0).unwrap().commands().len(), 5);
        assert_eq!(document.display_list(2.0).unwrap().commands().len(), 5);
    }

    #[test]
    fn borrowed_ui_handles_survive_variables_helpers_and_reused_children() {
        let source = r#"function wrap(child: View): View { return ui.row(4, 8, child, child) }
function main(): View { let child = ui.text("shared") return wrap(child) }"#;
        let document = compile(source, "arbitrary.namespace", 3).unwrap();
        assert_eq!(document.frame.commands.len(), 2);
        assert!(matches!(
            &document.frame.commands[0],
            RenderCommand::Text { x: 4.0, y: 4.0, .. }
        ));
        let width = crate::text::measure("shared", crate::text::TextStyle::ui(1)).width;
        assert!(matches!(
            &document.frame.commands[1],
            RenderCommand::Text { x, y: 4.0, .. } if (*x - (4.0 + width + 8.0)).abs() < 0.01
        ));
    }

    #[test]
    fn architecture_ranges_follow_crlf_and_cr_source_snapshots() {
        for ending in ["\r\n", "\r"] {
            let source = EXAMPLE.replace('\n', ending);
            let document = compile(&source, "app.main", 1).unwrap();
            assert_eq!(document.source, source);
            assert_eq!(document.root.unwrap().children[1].start_line, 5);
        }
    }

    #[test]
    fn rejects_invalid_entry_objects_arguments_and_old_syntax() {
        for source in [
            "namespace app.main export scene Main { render { Text(\"old\") } }",
            "function helper(): View { return ui.text(\"missing main\") }",
            "function main(value: View): View { return value }",
            "function main(): View { return \"wrong root\" }",
            "function main(): View { return main }",
            "function main(): View { return ui.text(1) }",
            "function main(): View { return ui.text(\"x\", 1.0) }",
            "function main(): View { return ui.text(\"x\", 9) }",
            "function main(): View { return ui.rect(-1, 1) }",
            "function main(): View { return ui.rect(1000001, 1) }",
            "function main(): View { return ui.rect(1, 1, 0, \"#中中\") }",
            "function main(): View { return ui.column(0, 0, ui.text) }",
            "function main(): View { return unknown(1) }",
            "function main(): View { return ui.missing() }",
        ] {
            assert!(
                compile(source, "app.main", 1).is_err(),
                "accepted: {source}"
            );
        }
    }

    #[test]
    fn source_diagnostics_keep_unicode_locations_and_submission_origin() {
        let error = compile(
            "function main(): View {\n    let title = ui.text(\"中文\")\n    return missing\n}",
            "app.main",
            17,
        )
        .unwrap_err();
        let error = error.downcast_ref::<frontend::SourceDiagnostic>().unwrap();
        assert_eq!(error.location.line, 3);
        assert!(error.origin.to_string().contains("submission 17"));
    }

    #[test]
    fn recursive_program_stops_at_the_vm_frame_limit() {
        let error = compile("function main(): View { return main() }", "app.main", 1).unwrap_err();
        assert!(
            error
                .to_string()
                .contains("execution limit reached: frames")
        );
    }

    fn nested_functions(levels: usize, shared: bool) -> String {
        let mut source = "function node0(): View { return ui.text(\"x\") }\n".to_owned();
        for index in 1..=levels {
            let previous = index - 1;
            if shared {
                source.push_str(&format!("function node{index}(): View {{ let child = node{previous}() return ui.column(0, 0, child, child) }}\n"));
            } else {
                source.push_str(&format!("function node{index}(): View {{ return ui.column(0, 0, node{previous}(), node{previous}()) }}\n"));
            }
        }
        source.push_str(&format!(
            "function main(): View {{ return node{levels}() }}"
        ));
        source
    }

    #[test]
    fn construction_and_expanded_layout_have_separate_budgets() {
        let error = compile(&nested_functions(12, false), "app.main", 1).unwrap_err();
        assert!(error.to_string().contains("4096 node budget"), "{error:#}");
        let error = compile(&nested_functions(14, true), "app.main", 2).unwrap_err();
        assert!(
            error.to_string().contains("expanded Block graph"),
            "{error:#}"
        );
    }

    #[test]
    fn managed_ui_depth_is_not_truncated_at_64_levels() {
        let mut source = "function node0(): View { return ui.text(\"x\") }\n".to_owned();
        for index in 1..=64 {
            source.push_str(&format!(
                "function node{index}(): View {{ return ui.column(0, 0, node{}()) }}\n",
                index - 1
            ));
        }
        source.push_str("function main(): View { return node64() }");
        let document = compile(&source, "app.main", 1).unwrap();
        assert_eq!(document.frame.commands.len(), 1);
    }

    #[test]
    fn failed_updates_preserve_success_and_delete_invalidates_inflight_work() {
        let mut state = NamespaceState::default();
        state.submission = state.next_submission().unwrap();
        assert_eq!(
            state
                .commit(state.submission, compile(EXAMPLE, "app.main", 1).unwrap())
                .unwrap(),
            Some(1)
        );
        state.submission = state.next_submission().unwrap();
        assert!(compile("invalid", "app.main", state.submission).is_err());
        assert_eq!(state.revision, 1);
        assert_eq!(state.document.source, EXAMPLE);
        let stale = state.submission;
        let candidate = compile(EXAMPLE, "app.main", stale).unwrap();
        state.submission = state.next_submission().unwrap();
        assert!(state.commit(stale, candidate.clone()).unwrap().is_none());
        let deleted = state.clear().unwrap();
        assert!(state.commit(stale, candidate).unwrap().is_none());
        assert_eq!(state.revision, deleted);
        assert!(state.document.source.is_empty());
        state.submission = state.next_submission().unwrap();
        let candidate = compile(EXAMPLE, "app.main", state.submission).unwrap();
        assert_eq!(
            state.commit(state.submission, candidate).unwrap(),
            Some(deleted + 1)
        );
    }
}