//! NativeContext 临时根、委托、观察依赖与完整签名的公开 API 回归；测试仍遵守远程执行约定。
//! Remote-only regression coverage. Do not execute locally.
use endor_core::{
    ChangeKey, ContextNativeFunction, ExecutionLimits, NativeCallable, NativeContext, NativeResult,
    ObjectRef, Value, Vm, VmError,
};

#[derive(Debug)]
/// bool 控制是否故意失败，两个临时分配用于观察成功/失败清理差异。
struct Allocate(bool);
impl NativeCallable for Allocate {
    /// VM 在 NativeContext 内调用此测试分派器，临时分配与输入由上下文保活，返回/委托后移交输出根。
    fn invoke(&self, cx: &mut NativeContext<'_>, _args: &[Value]) -> Result<NativeResult, VmError> {
        // 分配一份上下文临时根，成功返回时仅输出另取根移交，其余根由 Drop 归还。
        let value = cx.new_object()?;
        cx.set_attr(value, "label", Value::Text("scoped".into()))?;
        // 故意创建不返回对象，验证正常/报错都不会泄漏临时根。
        let _temporary = cx.new_object()?;
        // 故意在完成分配后报错，检验 RAII 不依赖回调正常返回。
        if self.0 {
            return Err(VmError::InvalidArgument("intentional failure"));
        }
        Ok(NativeResult::Return(Value::Object(value)))
    }
}

#[test]
/// 验证成功只移交一个结果根，未返回临时对象及错误路径分配全部回收。
fn scoped_allocations_return_one_root_and_clean_up_errors() {
    // 独立 VM 隔离测试对象图，所有结果根由场景显式归还。
    let mut vm = Vm::new().unwrap();
    // 分配上下文函数载荷，captures 管理显式托管边，分派器 Arc 不代替它们。
    let function = vm
        .allocate(ContextNativeFunction::new(
            "allocate",
            Allocate(false),
            vec![],
        ))
        .unwrap();
    // VM 调用已完成根移交，返回对象应只有一份调用者根。
    let value = vm.call(function, &[]).unwrap();
    // 解构返回值只复制身份，不增加引用计数。
    let Value::Object(object) = value else {
        panic!("expected object")
    };
    assert_eq!(vm.ref_count(object).unwrap(), 1);
    assert_eq!(vm.object_count(), 2);
    // 归还成功结果，之后只剩函数载荷，临时对象应已自动清理。
    vm.release_value(value).unwrap();
    vm.replace_payload(
        function,
        ContextNativeFunction::new("fail", Allocate(true), vec![]),
    )
    .unwrap();
    assert!(vm.call(function, &[]).is_err());
    assert_eq!(vm.object_count(), 1);
    vm.release(function).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[derive(Debug)]
/// 返回目标借用身份，由包装载荷 captures 保活，NativeContext 为 Invoke 输出取得拥有根。
struct Delegate(ObjectRef);
impl NativeCallable for Delegate {
    /// VM 在 NativeContext 内调用此测试分派器，临时分配与输入由上下文保活，返回/委托后移交输出根。
    fn invoke(&self, _cx: &mut NativeContext<'_>, args: &[Value]) -> Result<NativeResult, VmError> {
        Ok(NativeResult::Invoke {
            function: self.0,
            arguments: args.to_vec(),
        })
    }
}

#[test]
/// 验证 intrinsic 检查读取当前载荷的真实 Rust 实现，不能仅按不变函数身份推断。
fn native_implementation_inspection_follows_payload_replacement() {
    // 独立 VM 隔离测试对象图，所有结果根由场景显式归还。
    let mut vm = Vm::new().unwrap();
    // 分配上下文函数载荷，captures 管理显式托管边，分派器 Arc 不代替它们。
    let function = vm
        .allocate(ContextNativeFunction::new(
            "allocate",
            Allocate(false),
            vec![],
        ))
        .unwrap();
    // 借用当前 ContextNativeFunction 载荷，下转型检查不分配对象或执行回调。
    let payload = vm
        .payload::<ContextNativeFunction>(function, "native")
        .unwrap();
    assert!(payload.implementation::<Allocate>().is_some());
    assert!(payload.implementation::<Delegate>().is_none());
    // 记录更新前版本，替换实现后身份不变但版本必须增加。
    let version = vm.change_version(function).unwrap();
    // 委托目标有测试根，也会由 Delegate 包装载荷显式 captures 保留。
    let target = vm
        .allocate(ContextNativeFunction::new(
            "target",
            Allocate(false),
            vec![],
        ))
        .unwrap();
    vm.replace_payload(
        function,
        ContextNativeFunction::new("delegate", Delegate(target), vec![target]),
    )
    .unwrap();
    // 借用当前 ContextNativeFunction 载荷，下转型检查不分配对象或执行回调。
    let payload = vm
        .payload::<ContextNativeFunction>(function, "native")
        .unwrap();
    assert!(payload.implementation::<Allocate>().is_none());
    assert_eq!(payload.implementation::<Delegate>().unwrap().0, target);
    assert!(vm.change_version(function).unwrap() > version);
    // 逐项归还测试拥有根，包装载荷内部捕获边由 Heap 自动释放。
    for object in [function, target] {
        vm.release(object).unwrap();
    }
    assert_eq!(vm.object_count(), 0);
}

#[test]
/// 验证原生委托与目标共享累计预算，预算失败后目标/参数临时根计数恢复。
fn native_delegation_shares_budget_and_cleans_owned_arguments() {
    // 独立 VM 隔离测试对象图，所有结果根由场景显式归还。
    let mut vm = Vm::new().unwrap();
    // 委托目标有测试根，也会由 Delegate 包装载荷显式 captures 保留。
    let target = vm
        .allocate(ContextNativeFunction::new(
            "target",
            Allocate(false),
            vec![],
        ))
        .unwrap();
    // Delegate 返回 Invoke 而不是递归 vm.call，让外层共享预算与清理流程。
    let delegate = vm
        .allocate(ContextNativeFunction::new(
            "delegate",
            Delegate(target),
            vec![target],
        ))
        .unwrap();
    // 额外对象参数用于观察失败委托是否遗留执行根。
    let arg = vm.new_object().unwrap();
    assert!(
        vm.call_with_limits(
            delegate,
            &[Value::Object(arg)],
            ExecutionLimits {
                max_frames: 1,
                max_instructions: 1
            }
        )
        .is_err()
    );
    assert_eq!(vm.ref_count(arg).unwrap(), 1);
    assert_eq!(vm.ref_count(target).unwrap(), 2);
    // VM 调用已完成根移交，返回对象应只有一份调用者根。
    let value = vm.call(delegate, &[]).unwrap();
    // 归还成功结果，之后只剩函数载荷，临时对象应已自动清理。
    vm.release_value(value).unwrap();
    vm.release(delegate).unwrap();
    vm.release(target).unwrap();
    vm.release(arg).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
/// 弱句柄不持根；升级产生根，原对象释放后槽复用也不复活旧弱身份。
fn weak_references_expire_without_retaining_reused_slots() {
    // 独立 VM 隔离测试对象图，所有结果根由场景显式归还。
    let mut vm = Vm::new().unwrap();
    // 原始对象有一份分配根，弱身份或通知记录都不应额外持有它。
    let object = vm.new_object().unwrap();
    // downgrade 只形成借用弱身份，不延长对象寿命。
    let weak = vm.downgrade(object).unwrap();
    // 成功升级才取得一份独立外部根，随后必须归还。
    let upgraded = vm.upgrade(weak).unwrap().unwrap();
    vm.release(upgraded).unwrap();
    vm.release(object).unwrap();
    // 新对象可能复用同槽，但代际不同不能复活 weak。
    let replacement = vm.new_object().unwrap();
    assert!(vm.upgrade(weak).unwrap().is_none());
    // 另一堆升级旧身份应明确报 ForeignHandle，而不是过期 None。
    let mut foreign = Vm::new().unwrap();
    assert_eq!(foreign.upgrade(weak), Err(VmError::ForeignHandle));
    vm.release(replacement).unwrap();
}

#[test]
/// 同对象/字段通知合并最新版本，容器更新发 Contents，通知不充当 GC 根。
fn changes_coalesce_cover_containers_and_do_not_keep_sources_alive() {
    // 独立 VM 隔离测试对象图，所有结果根由场景显式归还。
    let mut vm = Vm::new().unwrap();
    // 原始对象有一份分配根，弱身份或通知记录都不应额外持有它。
    let object = vm.new_object().unwrap();
    vm.set_attr(object, "value", Value::Bool(false)).unwrap();
    vm.set_attr(object, "value", Value::Bool(true)).unwrap();
    // 两次同名写入的最终版本应出现在合并通知中。
    let version = vm.change_version(object).unwrap();
    // 取走通知批次同时重置缓存，数据中的源身份不 retain。
    let changes = vm.take_changes();
    assert!(!changes.rescan_required);
    assert_eq!(changes.changes.len(), 1);
    assert_eq!(changes.changes[0].key, ChangeKey::Attribute("value".into()));
    assert_eq!(changes.changes[0].version, version);
    // Cell 更新/清空使用载荷替换，通知键为 Contents，不是普通字段。
    let cell = vm.new_cell(None).unwrap();
    vm.cell_set(cell, Value::Object(object)).unwrap();
    vm.cell_clear(cell).unwrap();
    assert_eq!(vm.take_changes().changes[0].key, ChangeKey::Contents);
    vm.set_attr(object, "self", Value::Object(object)).unwrap();
    vm.release(object).unwrap();
    assert_eq!(vm.collect_cycles(), 1);
    vm.release(cell).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
/// 超过通知唯一键上限清空精确条目并标记重扫，取走批次后新通知正常开始。
fn notification_overflow_requires_rescan_instead_of_losing_changes_silently() {
    // 独立 VM 隔离测试对象图，所有结果根由场景显式归还。
    let mut vm = Vm::new().unwrap();
    // 原始对象有一份分配根，弱身份或通知记录都不应额外持有它。
    let object = vm.new_object().unwrap();
    // 制造超过 4096 个不同字段键，重复同键不足以触发通知溢出。
    for index in 0..4100 {
        vm.set_attr(object, index.to_string(), Value::Nil).unwrap();
    }
    // 取走通知批次同时重置缓存，数据中的源身份不 retain。
    let changes = vm.take_changes();
    assert!(changes.rescan_required);
    assert!(changes.changes.is_empty());
    vm.set_attr(object, "after", Value::Nil).unwrap();
    assert_eq!(vm.take_changes().changes.len(), 1);
    vm.release(object).unwrap();
}

#[derive(Debug)]
struct ReadResult {
    /// 输入借用身份，包装载荷 captures 负责保活。
    source: ObjectRef,
    /// 是否故意写旧输入，触发只读保护错误。
    mutate: bool,
}
impl NativeCallable for ReadResult {
    /// VM 在 NativeContext 内调用此测试分派器，临时分配与输入由上下文保活，返回/委托后移交输出根。
    fn invoke(&self, cx: &mut NativeContext<'_>, _: &[Value]) -> Result<NativeResult, VmError> {
        // 借用读取 source 的输入字段，读取路径纳入当前只读依赖收集。
        let value = cx.store().get_attr(self.source, "value")?;
        // 非法分支试图修改进入只读前已存在的 source，应在写屏障处失败。
        if self.mutate {
            cx.set_attr(self.source, "value", Value::Number(99_i64.into()))?;
        }
        // 新结果不在进入只读时的保护快照内，允许初始化 copied 字段。
        let result = cx.new_object()?;
        cx.set_attr(result, "copied", value)?;
        Ok(NativeResult::Return(Value::Object(result)))
    }
}

#[test]
/// 只读调用记录输入观察并允许构造新结果，非法改旧对象报错后作用域必须恢复。
fn read_only_calls_track_borrowed_dependencies_allow_results_and_restore_after_error() {
    // 独立 VM 隔离测试对象图，所有结果根由场景显式归还。
    let mut vm = Vm::new().unwrap();
    // 输入源在调用前创建并初始化，是只读保护与读取依赖的对象。
    let source = vm.new_object().unwrap();
    vm.set_attr(source, "value", Value::Number(7_i64.into()))
        .unwrap();
    // 分配上下文函数载荷，captures 管理显式托管边，分派器 Arc 不代替它们。
    let function = vm
        .allocate(ContextNativeFunction::new(
            "read result",
            ReadResult {
                source,
                mutate: false,
            },
            vec![source],
        ))
        .unwrap();
    // 丢弃场景初始化通知，只检查本次只读派生构造是否发布了输入变更。
    vm.take_changes();
    // 结果是拥有值，reads 是借用观察集合，两个所有权语义不能混同。
    let (value, reads) = vm
        .call_read_only_with_limits(function, &[], ExecutionLimits::default())
        .unwrap();
    assert!(reads.contains(&source));
    assert!(vm.take_changes().changes.is_empty());
    // 检查新结果 copied 值后归还结果根，不能 release 读取依赖句柄。
    let Value::Object(result) = value else {
        panic!("result")
    };
    assert_eq!(
        vm.get_attr(result, "copied").unwrap(),
        Value::Number(7_i64.into())
    );
    vm.release(result).unwrap();
    vm.replace_payload(
        function,
        ContextNativeFunction::new(
            "illegal write",
            ReadResult {
                source,
                mutate: true,
            },
            vec![source],
        ),
    )
    .unwrap();
    assert!(
        vm.call_read_only_with_limits(function, &[], ExecutionLimits::default())
            .is_err()
    );
    assert_eq!(
        vm.get_attr(source, "value").unwrap(),
        Value::Number(7_i64.into())
    );
    vm.set_attr(source, "value", Value::Number(8_i64.into()))
        .unwrap();
    vm.release(function).unwrap();
    vm.release(source).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
/// 注解验证也记录依赖，但单独标为非内容读取；同对象普通读取随后提升为内容读取。
fn annotation_reads_remain_dependencies_without_becoming_program_content_reads() {
    use endor_core::AnnotationType;
    // 本测试直接使用 Store 精确分类入口，不需要执行器帧。
    let mut store = objects::ObjectStore::new().unwrap();
    // 普通 Record 不符合 Number，但有效对象应符合 Any。
    let object = store.new_object().unwrap();
    store
        .set_attr(object, "value", Value::Number(1.into()))
        .unwrap();
    // 只读范围收集整体观察，子区间分类不会清空外层依赖。
    let scope = store.begin_read_only();
    // 每个子区间重新开始收集，按 LIFO 结束；重复读取也要在新区域出现。
    let token = store.begin_read_tracking().unwrap();
    assert!(
        store
            .matches_annotation(&Value::Object(object), AnnotationType::Any)
            .unwrap()
    );
    // 返回 ReadAccess 区分 content_read，句柄仍不拥有根。
    let reads = store.end_read_tracking_details(token).unwrap();
    assert!(
        reads
            .iter()
            .any(|read| read.object == object && !read.content_read)
    );
    // 每个子区间重新开始收集，按 LIFO 结束；重复读取也要在新区域出现。
    let token = store.begin_read_tracking().unwrap();
    assert!(
        !store
            .matches_annotation(&Value::Object(object), AnnotationType::Number)
            .unwrap()
    );
    // 异堆对象即使匹配 Any 也先拒绝无效归属。
    let mut foreign = objects::ObjectStore::new().unwrap();
    // 有效但异堆的测试输入，用于排除 Any 跳过句柄校验的错误实现。
    let alien = foreign.new_object().unwrap();
    assert!(matches!(
        store.matches_annotation(&Value::Object(alien), AnnotationType::Any),
        Err(VmError::ForeignHandle)
    ));
    foreign.release(alien).unwrap();
    // 补一次普通字段读取，与前面的验证读取合并时 content_read 必须为 true。
    store.get_attr(object, "value").unwrap();
    // 返回 ReadAccess 区分 content_read，句柄仍不拥有根。
    let reads = store.end_read_tracking_details(token).unwrap();
    assert!(
        reads
            .iter()
            .any(|read| read.object == object && read.content_read)
    );
    assert!(store.end_read_only(scope).unwrap().contains(&object));
    store.release(object).unwrap();
    assert_eq!(store.object_count(), 0);
}

#[derive(Debug)]
struct TypedNative {
    signature: endor_core::CallSignature,
    calls: std::sync::Arc<std::sync::atomic::AtomicUsize>,
    delegate: Option<ObjectRef>,
    allocate_result: bool,
}
impl NativeCallable for TypedNative {
    fn signature(&self) -> Option<endor_core::CallSignature> {
        Some(self.signature.clone())
    }
    fn invoke(&self, cx: &mut NativeContext<'_>, args: &[Value]) -> Result<NativeResult, VmError> {
        self.calls.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
        if let Some(function) = self.delegate {
            return Ok(NativeResult::Invoke {
                function,
                arguments: args.to_vec(),
            });
        }
        Ok(NativeResult::Return(if self.allocate_result {
            Value::Object(cx.new_object()?)
        } else {
            args.last().cloned().unwrap_or(Value::Nil)
        }))
    }
}

#[test]
fn native_types_preflight_arguments_and_clean_wrong_result_roots() {
    use endor_core::{AnnotationType as T, CallEffect, CallSignature};
    use std::sync::{
        Arc,
        atomic::{AtomicUsize, Ordering},
    };
    let mut vm = Vm::new().unwrap();
    let calls = Arc::new(AtomicUsize::new(0));
    let function = vm
        .allocate(ContextNativeFunction::new(
            "typed",
            TypedNative {
                signature: CallSignature::exact(vec![T::Number], T::Number, CallEffect::ReadOnly),
                calls: calls.clone(),
                delegate: None,
                allocate_result: true,
            },
            vec![],
        ))
        .unwrap();
    assert!(
        matches!(vm.call(function, &[Value::Text("bad".into())]), Err(VmError::TypeMismatch { position, .. }) if position == "parameter 1")
    );
    assert_eq!(calls.load(Ordering::SeqCst), 0);
    assert!(
        matches!(vm.call(function, &[Value::Number(7.into())]), Err(VmError::TypeMismatch { position, .. }) if position == "return")
    );
    assert_eq!(calls.load(Ordering::SeqCst), 1);
    assert_eq!(vm.object_count(), 1);
    vm.release(function).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn delegated_source_results_obey_every_native_contract_without_extra_frames() {
    use endor_core::{
        AnnotationType as T, CallEffect, CallSignature, CodeLayout, EndorCode, Instruction, Opcode,
    };
    use std::sync::{Arc, atomic::AtomicUsize};
    let mut vm = Vm::new().unwrap();
    let code = EndorCode::from_instructions(
        &[
            Instruction::new(Opcode::LoadConst, 0),
            Instruction::simple(Opcode::ReturnValue),
        ],
        vec![Value::Text("source result".into())],
        CodeLayout::default(),
    )
    .unwrap();
    let code = vm.new_code(code).unwrap();
    let globals = vm.new_dict().unwrap();
    let source = vm
        .new_function("source", code, globals, vec![], vec![])
        .unwrap();
    let calls = Arc::new(AtomicUsize::new(0));
    let inner = vm
        .allocate(ContextNativeFunction::new(
            "inner",
            TypedNative {
                signature: CallSignature::exact(vec![], T::String, CallEffect::ReadOnly),
                calls: calls.clone(),
                delegate: Some(source),
                allocate_result: false,
            },
            vec![source],
        ))
        .unwrap();
    let outer = vm
        .allocate(ContextNativeFunction::new(
            "outer",
            TypedNative {
                signature: CallSignature::exact(vec![], T::Number, CallEffect::ReadOnly),
                calls,
                delegate: Some(inner),
                allocate_result: false,
            },
            vec![inner],
        ))
        .unwrap();
    let limits = ExecutionLimits {
        max_frames: 1,
        max_instructions: 100,
    };
    assert_eq!(
        vm.call_with_limits(inner, &[], limits).unwrap(),
        Value::Text("source result".into())
    );
    assert!(
        matches!(vm.call_with_limits(outer, &[], limits), Err(VmError::TypeMismatch { function, position, .. }) if function == "outer" && position == "return")
    );
    assert!(matches!(
        vm.call_with_limits(
            outer,
            &[],
            ExecutionLimits {
                max_frames: 0,
                ..limits
            }
        ),
        Err(VmError::ExecutionLimit("frames"))
    ));
    for object in [outer, inner, source, globals, code] {
        vm.release(object).unwrap();
    }
    vm.collect_cycles();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn signatures_trace_nominal_types_and_bound_receivers_use_the_actual_contract() {
    use endor_core::{AnnotationType as T, CallEffect, CallSignature, TypeConstructor};
    use std::sync::{
        Arc,
        atomic::{AtomicUsize, Ordering},
    };
    let mut vm = Vm::new().unwrap();
    let roots = vm.bootstrap_types().unwrap();
    let definition = vm
        .new_type("Receiver", roots.object, TypeConstructor::Record)
        .unwrap();
    let calls = Arc::new(AtomicUsize::new(0));
    let function = vm
        .allocate(ContextNativeFunction::new(
            "echo",
            TypedNative {
                signature: CallSignature::exact(
                    vec![T::Nominal(definition), T::Number],
                    T::Number,
                    CallEffect::ReadOnly,
                ),
                calls: calls.clone(),
                delegate: None,
                allocate_result: false,
            },
            vec![],
        ))
        .unwrap(); // Metadata alone traces the definition.
    let weak = vm.downgrade(definition).unwrap();
    vm.define_method(definition, "echo", function).unwrap();
    let receiver = vm.new_object().unwrap();
    vm.attach_type(receiver, definition).unwrap();
    vm.release(definition).unwrap();
    let Value::Object(bound) = vm.bind_attr(receiver, "echo").unwrap() else {
        panic!("bound method")
    };
    assert_eq!(
        vm.call_arity(bound).unwrap(),
        Some(endor_core::CallArity::exact(1))
    );
    assert!(vm.call(bound, &[Value::Bool(true)]).is_err());
    assert_eq!(calls.load(Ordering::SeqCst), 0);
    assert_eq!(
        vm.call(bound, &[Value::Number(9.into())]).unwrap(),
        Value::Number(9.into())
    );
    for object in [bound, receiver, function, roots.object, roots.type_type] {
        vm.release(object).unwrap();
    }
    vm.collect_cycles();
    assert!(vm.upgrade(weak).unwrap().is_none());
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn declared_host_effects_are_rejected_before_read_only_dispatch() {
    use endor_core::{AnnotationType as T, CallEffect, CallSignature};
    use std::sync::{
        Arc,
        atomic::{AtomicUsize, Ordering},
    };
    for effect in [CallEffect::Mutating, CallEffect::External] {
        let mut vm = Vm::new().unwrap();
        let calls = Arc::new(AtomicUsize::new(0));
        let function = vm
            .allocate(ContextNativeFunction::new(
                "effect",
                TypedNative {
                    signature: CallSignature::exact(vec![], T::Unit, effect),
                    calls: calls.clone(),
                    delegate: None,
                    allocate_result: false,
                },
                vec![],
            ))
            .unwrap();
        assert!(
            vm.call_read_only_with_limits(function, &[], ExecutionLimits::default())
                .is_err()
        );
        assert_eq!(calls.load(Ordering::SeqCst), 0);
        assert_eq!(vm.call(function, &[]).unwrap(), Value::Nil);
        vm.release(function).unwrap();
        assert_eq!(vm.object_count(), 0);
    }
}

#[test]
fn legacy_native_signatures_check_optional_variadic_types_and_metadata() {
    use endor_core::{AnnotationType as T, CallArity, CallEffect, CallSignature, NativeFunction};
    fn echo(args: &[Value]) -> Result<Value, VmError> {
        Ok(args.last().cloned().unwrap_or(Value::Nil))
    }
    let mut vm = Vm::new().unwrap();
    let function = vm
        .allocate(
            NativeFunction::new("legacy", echo).with_signature(CallSignature {
                arity: CallArity::range(0, usize::MAX),
                parameters: vec![],
                variadic: Some(T::Number.into()),
                returns: T::Number.into(),
                effect: CallEffect::ReadOnly,
            }),
        )
        .unwrap();
    assert_eq!(
        vm.call(
            function,
            &[Value::Number(1.into()), Value::Number(2.into())]
        )
        .unwrap(),
        Value::Number(2.into())
    );
    assert!(vm.call(function, &[Value::Bool(true)]).is_err());
    assert!(
        matches!(vm.call(function, &[]), Err(VmError::TypeMismatch { position, .. }) if position == "return")
    );
    let invalid = vm
        .allocate(
            NativeFunction::new("invalid", echo)
                .with_signature(CallSignature::exact(
                    vec![T::Number],
                    T::Number,
                    CallEffect::ReadOnly,
                ))
                .with_arity(CallArity::exact(0)),
        )
        .unwrap();
    assert!(vm.call_arity(invalid).is_err());
    assert!(vm.call(invalid, &[]).is_err());
    vm.release(invalid).unwrap();
    vm.release(function).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[derive(Debug)]
struct EraseThenDelegate {
    signature: endor_core::CallSignature,
    target: ObjectRef,
}
impl NativeCallable for EraseThenDelegate {
    fn signature(&self) -> Option<endor_core::CallSignature> {
        Some(self.signature.clone())
    }
    fn invoke(&self, cx: &mut NativeContext<'_>, _: &[Value]) -> Result<NativeResult, VmError> {
        cx.replace_payload(cx.callee(), endor_core::Record)?;
        Ok(NativeResult::Invoke {
            function: self.target,
            arguments: vec![],
        })
    }
}

#[test]
fn delegated_return_type_survives_removal_of_the_original_signature_edges() {
    use endor_core::{
        AnnotationType as T, CallEffect, CallSignature, CodeLayout, EndorCode, Instruction, Opcode,
        TypeConstructor,
    };
    let mut vm = Vm::new().unwrap();
    let roots = vm.bootstrap_types().unwrap();
    let definition = vm
        .new_type("Transient", roots.object, TypeConstructor::Record)
        .unwrap();
    let weak = vm.downgrade(definition).unwrap();
    let code = EndorCode::from_instructions(
        &[
            Instruction::new(Opcode::LoadConst, 0),
            Instruction::simple(Opcode::ReturnValue),
        ],
        vec![Value::Nil],
        CodeLayout::default(),
    )
    .unwrap();
    let code = vm.new_code(code).unwrap();
    let globals = vm.new_dict().unwrap();
    let source = vm
        .new_function("source", code, globals, vec![], vec![])
        .unwrap();
    let mut signature = CallSignature::exact(vec![], T::Any, CallEffect::Mutating);
    signature.returns = endor_core::CallType::Union(vec![T::Nominal(definition), T::Number]);
    let wrapper = vm
        .allocate(ContextNativeFunction::new(
            "erased",
            EraseThenDelegate {
                signature,
                target: source,
            },
            vec![source],
        ))
        .unwrap();
    vm.release(definition).unwrap();
    assert!(
        matches!(vm.call(wrapper, &[]), Err(VmError::TypeMismatch { function, expected, .. }) if function == "erased" && expected == "Transient | Number")
    );
    assert!(vm.upgrade(weak).unwrap().is_none());
    for object in [
        wrapper,
        source,
        code,
        globals,
        roots.object,
        roots.type_type,
    ] {
        vm.release(object).unwrap();
    }
    vm.collect_cycles();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn native_union_and_nullable_contracts_accept_each_branch_and_reject_invalid_metadata() {
    use endor_core::{AnnotationType as T, CallEffect, CallSignature, CallType};
    use std::sync::{
        Arc,
        atomic::{AtomicUsize, Ordering},
    };
    let mut vm = Vm::new().unwrap();
    let calls = Arc::new(AtomicUsize::new(0));
    let mut signature = CallSignature::exact(vec![T::Any], T::Any, CallEffect::ReadOnly);
    signature.parameters[0] = CallType::Union(vec![T::String, T::Bool]);
    signature.returns = signature.parameters[0].clone();
    let function = vm
        .allocate(ContextNativeFunction::new(
            "union",
            TypedNative {
                signature,
                calls: calls.clone(),
                delegate: None,
                allocate_result: false,
            },
            vec![],
        ))
        .unwrap();
    for value in [
        Value::Text("capture".into()),
        Value::Bool(true),
        Value::Bool(false),
    ] {
        assert_eq!(
            vm.call(function, std::slice::from_ref(&value)).unwrap(),
            value
        );
    }
    assert!(
        matches!(vm.call(function, &[Value::Number(3.into())]), Err(VmError::TypeMismatch { expected, .. }) if expected == "String | Bool")
    );
    assert_eq!(calls.load(Ordering::SeqCst), 3);
    let mut signature = CallSignature::exact(vec![T::Any], T::Any, CallEffect::ReadOnly);
    signature.parameters[0] = CallType::nullable(T::Number);
    signature.returns = signature.parameters[0].clone();
    vm.replace_payload(
        function,
        ContextNativeFunction::new(
            "nullable",
            TypedNative {
                signature,
                calls: calls.clone(),
                delegate: None,
                allocate_result: false,
            },
            vec![],
        ),
    )
    .unwrap();
    for value in [Value::Nil, Value::Number(2.into())] {
        assert_eq!(
            vm.call(function, std::slice::from_ref(&value)).unwrap(),
            value
        );
    }
    let record = vm.new_object().unwrap();
    let mut signature = CallSignature::exact(vec![T::Any], T::Any, CallEffect::ReadOnly);
    // A matching first branch must not hide a later invalid nominal definition.
    signature.parameters[0] = CallType::Union(vec![T::Any, T::Nominal(record)]);
    vm.replace_payload(
        function,
        ContextNativeFunction::new(
            "invalid union",
            TypedNative {
                signature,
                calls: calls.clone(),
                delegate: None,
                allocate_result: false,
            },
            vec![],
        ),
    )
    .unwrap();
    assert!(vm.call(function, &[Value::Nil]).is_err());
    assert_eq!(calls.load(Ordering::SeqCst), 5);
    let mut signature = CallSignature::exact(vec![], T::Any, CallEffect::ReadOnly);
    signature.returns = CallType::Union(vec![]);
    vm.replace_payload(
        function,
        ContextNativeFunction::new(
            "empty union",
            TypedNative {
                signature,
                calls: calls.clone(),
                delegate: None,
                allocate_result: false,
            },
            vec![],
        ),
    )
    .unwrap();
    assert!(vm.call(function, &[]).is_err());
    assert_eq!(calls.load(Ordering::SeqCst), 5);
    vm.release(record).unwrap();
    vm.release(function).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn delegated_effects_keep_the_original_read_only_scope_and_check_the_actual_target() {
    use endor_core::{AnnotationType as T, CallEffect, CallSignature};
    use std::sync::{
        Arc,
        atomic::{AtomicUsize, Ordering},
    };
    let mut vm = Vm::new().unwrap();
    let calls = Arc::new(AtomicUsize::new(0));
    let target_calls = Arc::new(AtomicUsize::new(0));
    let target = vm
        .allocate(ContextNativeFunction::new(
            "target",
            TypedNative {
                signature: CallSignature::exact(vec![], T::Unit, CallEffect::Mutating),
                calls: target_calls.clone(),
                delegate: None,
                allocate_result: false,
            },
            vec![],
        ))
        .unwrap();
    let wrapper = vm
        .allocate(ContextNativeFunction::new(
            "wrapper",
            TypedNative {
                signature: CallSignature::exact(vec![], T::Unit, CallEffect::Delegated),
                calls: calls.clone(),
                delegate: Some(target),
                allocate_result: false,
            },
            vec![target],
        ))
        .unwrap();
    assert!(
        vm.call_read_only_with_limits(wrapper, &[], ExecutionLimits::default())
            .is_err()
    );
    assert_eq!(calls.load(Ordering::SeqCst), 1);
    assert_eq!(target_calls.load(Ordering::SeqCst), 0);
    assert_eq!(vm.call(wrapper, &[]).unwrap(), Value::Nil);
    vm.replace_payload(
        target,
        ContextNativeFunction::new(
            "pure",
            TypedNative {
                signature: CallSignature::exact(vec![], T::Unit, CallEffect::ReadOnly),
                calls: target_calls.clone(),
                delegate: None,
                allocate_result: false,
            },
            vec![],
        ),
    )
    .unwrap();
    assert_eq!(
        vm.call_read_only_with_limits(wrapper, &[], ExecutionLimits::default())
            .unwrap()
            .0,
        Value::Nil
    );
    for object in [wrapper, target] {
        vm.release(object).unwrap();
    }
    assert_eq!(vm.object_count(), 0);
}