//! 一个原生窗口对应一份 Presentation：独立视口、Mount、测量缓存、焦点与依赖记录。
//! 多个窗口仍使用同一个 VM 和共享业务对象。读取版本失效时只标记相关展示需要刷新，不能因此复制一份业务状态。
//!
//! Per-window rendering state. Business objects and code remain in one VM.
//! Registries and caches borrow checked identities; the managed desktop owns
//! presentation roots through its pending/mount dictionaries.
use crate::ui_bridge::UiNode;
use endor_core::{ChangeBatch, NativeContext, ObjectRef, Vm, VmError, WeakObjectRef};
use std::sync::Arc;

#[derive(Debug)]
/// 一个窗口独立的展示状态：活动页面、待提交请求、Mount、布局与源读取缓存；共享 VM 的业务状态不放在这里复制。
pub(crate) struct Presentation {
    // 所属托管桌面身份；此结构借用身份，真正的展示根由托管桌面字典维持。
    pub desktop: ObjectRef,
    pub closing: bool,
    pub tabs: ObjectRef,
    pub active: Option<ObjectRef>,
    // 双层 Option 区分三态：None 无请求，Some(None) 请求清空，Some(Some(page)) 请求切页。
    pub pending: Option<Option<ObjectRef>>,
    pub last_snapshot: Option<Arc<UiNode>>,
    // 弱身份到原生稳定标签 ID 的映射；不能因为标签历史而保活已经关闭的页面。
    pub tab_ids: Vec<(WeakObjectRef, u64)>,
    pub next_tab: u64,
    pub last_tabs: Vec<crate::tabs::Tab>,
    pub surface: crate::page::Surface,
    pub render_cache: crate::snapshot::RenderCache,
    pub layout: crate::layout::LayoutRuntime,
    pub mounts: crate::mount::MountTable,
    pub published_version: u64,
    // 即使根快照身份未变也要求重新发布一帧，例如源绘制读取的数据发生变化时。
    pub force_frame: bool,
    // 精确名称/字典种类依赖，与下面按整个对象版本记录的 reads 分开检查。
    pub paint_names: Vec<endor_core::ReadDependency>,
    pub layout_names: Vec<endor_core::ReadDependency>,
    pub paint_reads: std::collections::BTreeMap<ObjectRef, u64>,
    pub dependency_invalidations: usize,
    pub last_invalid_dependency: String,
    pub layout_reads: std::collections::BTreeMap<ObjectRef, u64>,
    pub measure_cache: crate::source_layout::Cache,
    pub snapshot_visited: usize,
    pub snapshot_reused: usize,
}

impl Presentation {
    /// 比较布局/绘制读取版本和名称依赖，标记需要刷新并通知快照缓存。
    pub fn observe_changes(&mut self, vm: &Vm, changes: &ChangeBatch) {
        // 先检查粗粒度对象版本，layout 优先于 paint；每类只记录第一个失效项用于诊断。
        // 对象已经释放时版本查询失败，也视作失效，而非继续使用旧缓存。
        if let Some((phase, object, version)) = self
            .layout_reads
            .iter()
            .map(|(object, version)| ("layout", object, version))
            .chain(
                self.paint_reads
                    .iter()
                    .map(|(object, version)| ("paint", object, version)),
            )
            .find(|(_, object, version)| vm.change_version(**object).ok() != Some(**version))
        {
            self.force_frame = true;
            self.dependency_invalidations = self.dependency_invalidations.saturating_add(1);
            let kind = vm
                .object(*object)
                .map(|value| value.payload().kind_name())
                .unwrap_or("released");
            self.last_invalid_dependency = format!(
                "{phase} {kind} {object}: {version} -> {:?}",
                vm.change_version(*object).ok()
            );
        }
        // 再核对名称级依赖，避免仅凭对象版本漏掉名称解析路径上的变化。
        // 两个检查独立执行，因此同次观察可能分别增加计数，后者诊断可覆盖前者。
        if let Some((phase, dependency)) = self
            .layout_names
            .iter()
            .map(|dependency| ("layout", dependency))
            .chain(
                self.paint_names
                    .iter()
                    .map(|dependency| ("paint", dependency)),
            )
            .find(|(_, dependency)| !vm.object_store().read_dependency_valid(dependency))
        {
            self.force_frame = true;
            self.dependency_invalidations = self.dependency_invalidations.saturating_add(1);
            let name = match dependency {
                endor_core::ReadDependency::Name { name, .. } => name.as_str(),
                _ => "<dictionary kind>",
            };
            self.last_invalid_dependency = format!("{phase} name {}:{name}", dependency.object());
        }
        // 把同一批 VM 写入交给视觉快照缓存，源布局/绘制依赖与原生快照依赖分别维护。
        self.render_cache.invalidate(ChangeBatch {
            changes: changes.changes.clone(),
            rescan_required: changes.rescan_required,
        });
    }

    /// 按尺寸、内容或绘制失效原因清理对应缓存，避免把所有变化都当成相同重建。
    pub fn invalidate(
        &mut self,
        cx: &mut NativeContext<'_>,
        affected: &std::collections::HashSet<ObjectRef>,
        reason: &str,
    ) -> Result<(), VmError> {
        // 仅绘制失效不影响测量；其余原因清除测量结果并按 Block ID 使布局缓存失效。
        if reason != "paint" {
            self.measure_cache.invalidate(affected);
            for block in affected {
                self.layout.invalidate(&block.to_string());
            }
        }
        // 内容变化还可能改变组成结构，因此显式失效视觉快照及其父链；其他原因不额外做此传播。
        if reason == "content" {
            self.render_cache
                .invalidate_objects(affected.iter().copied());
        }
        // 仅当受影响 Block 在该窗口有活动出现时强制刷新，避免无关窗口重复发帧。
        for weak in self.mounts.active.values() {
            if let Some(mount) = cx.upgrade(*weak)?
                && affected.contains(
                    &cx.store()
                        .payload::<crate::mount::Mount>(mount, "Mount")?
                        .block,
                )
            {
                self.force_frame = true;
            }
        }
        Ok(())
    }

    /// 用桌面与标签注册表身份初始化窗口状态，布局和视觉缓存从空状态开始。
    // 这里只初始化窗口级缓存，不创建 VM、不复制业务对象；active/pending 留空等待窗口展示请求。
    pub fn new(desktop: ObjectRef, tabs: ObjectRef) -> Self {
        Self {
            desktop,
            closing: false,
            tabs,
            active: None,
            pending: None,
            last_snapshot: None,
            tab_ids: Vec::new(),
            next_tab: 0,
            last_tabs: Vec::new(),
            surface: crate::page::Surface::default(),
            render_cache: crate::snapshot::RenderCache::default(),
            layout: crate::layout::LayoutRuntime::default(),
            mounts: crate::mount::MountTable::default(),
            published_version: 0,
            force_frame: false,
            paint_names: Vec::new(),
            layout_names: Vec::new(),
            paint_reads: std::collections::BTreeMap::new(),
            dependency_invalidations: 0,
            last_invalid_dependency: String::new(),
            layout_reads: std::collections::BTreeMap::new(),
            measure_cache: crate::source_layout::Cache::default(),
            snapshot_visited: 0,
            snapshot_reused: 0,
        }
    }
}

/// 把读取记录拆成对象版本和精确名称依赖，便于按实际观察内容判断失效。
pub(crate) fn split_reads(
    reads: Vec<endor_core::ReadDependency>,
) -> (
    std::collections::BTreeMap<ObjectRef, u64>,
    Vec<endor_core::ReadDependency>,
) {
    let mut objects = std::collections::BTreeMap::new();
    let mut names = Vec::new();
    // 整对象依赖按身份收集到有序表，重复项以最后一次版本为准；其余精确依赖保持原记录。
    for dependency in reads {
        match dependency {
            endor_core::ReadDependency::Object { object, version } => {
                objects.insert(object, version);
            }
            dependency => names.push(dependency),
        }
    }
    (objects, names)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{layout::Size, ui_bridge::UiKind};
    #[test]
    /// 同VM中两Presentation分别布局共享树，尺寸/出现身份独立；读观察可追踪共享对象但不能增添GC根。
    fn independent_view_geometry_and_shared_vm_reads_do_not_add_roots() {
        // 测试在同一 VM 中建立两个 Presentation，验证各自布局尺寸/出现 ID 独立，读取依赖共享业务对象。
        let mut vm = Vm::new().unwrap();
        let mut left = Presentation::new(vm.new_object().unwrap(), vm.new_dict().unwrap());
        let mut right = Presentation::new(vm.new_object().unwrap(), vm.new_dict().unwrap());
        left.layout.viewport = Some(Size {
            width: 100.0,
            height: 80.0,
        });
        right.layout.viewport = Some(Size {
            width: 200.0,
            height: 160.0,
        });
        let root = UiNode {
            surface: None,
            flex: 0.0,
            flex_policy: crate::layout::FlexPolicy::default(),
            main_align: crate::layout::MainAlign::Start,
            cross_align: crate::layout::CrossAlign::Start,
            align_self: None,
            margin: crate::layout::Insets::default(),
            sizing: crate::box_model::Sizing::default(),
            padding_edges: [None; 4],
            border: crate::layout::Insets::default(),
            border_color: "#D8DCE2".into(),
            clip_children: false,
            block_id: "shared".into(),
            protocol_key: "rect".into(),
            slots: Vec::new(),
            interactive: false,
            pointer_events: false,
            kind: UiKind::Rect {
                width: 500.0,
                height: 500.0,
                radius: 0.0,
                color: "#237A45".into(),
            },
        };
        let left_frame = left.layout.frame(&root).unwrap();
        let right_frame = right.layout.frame(&root).unwrap();
        assert_eq!(left_frame.mounts[0].width, 100.0);
        assert_eq!(right_frame.mounts[0].width, 200.0);
        left.layout.clear_occurrences();
        let new_left = left.layout.frame(&root).unwrap();
        let same_right = right.layout.frame(&root).unwrap();
        assert_ne!(new_left.mounts[0].id, left_frame.mounts[0].id);
        assert_eq!(same_right.mounts[0].id, right_frame.mounts[0].id);
        let shared = vm.new_object().unwrap();
        let version = vm.change_version(shared).unwrap();
        left.paint_reads.insert(shared, version);
        right.layout_reads.insert(shared, version);
        vm.set_attr(shared, "value", endor_core::Value::Bool(true))
            .unwrap();
        let changes = vm.take_changes();
        left.observe_changes(&vm, &changes);
        right.observe_changes(&vm, &changes);
        assert!(left.force_frame && right.force_frame);
        // 最后释放业务对象并回收：两份读取记录都不应成为托管根，弱引用应升级失败。
        let weak = vm.downgrade(shared).unwrap();
        vm.release(shared).unwrap();
        vm.collect_cycles();
        assert!(vm.upgrade(weak).unwrap().is_none());
    }
}