use std::any::Any;
use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};

use endor_core::{
    CodeLayout, CompareOp, EndorCode, EndorCodeObject, EndorFunctionObject,
    EndorNativeFunctionObject, ExecutionLimits, Instruction, ObjectPayload, ObjectRef, Opcode,
    Value, Vm, VmError,
};

fn op(opcode: Opcode, argument: u32) -> Instruction {
    Instruction::new(opcode, argument)
}
fn simple(opcode: Opcode) -> Instruction {
    Instruction::simple(opcode)
}
fn text(value: &str) -> Value {
    Value::Text(value.into())
}
fn make_code(
    vm: &mut Vm,
    instructions: &[Instruction],
    constants: Vec<Value>,
    layout: CodeLayout,
) -> ObjectRef {
    vm.new_code(EndorCode::from_instructions(instructions, constants, layout).unwrap())
        .unwrap()
}
fn return_constant(vm: &mut Vm, value: Value) -> ObjectRef {
    make_code(
        vm,
        &[op(Opcode::LoadConst, 0), simple(Opcode::ReturnValue)],
        vec![value],
        CodeLayout::default(),
    )
}

#[derive(Debug)]
struct SharedReference(AtomicUsize);
impl ObjectPayload for SharedReference {
    fn as_any(&self) -> &dyn Any {
        self
    }
    fn kind_name(&self) -> &'static str {
        "shared-reference"
    }
    fn assign_from(&self, source: &dyn ObjectPayload) -> Result<bool, VmError> {
        let Some(source) = source.as_any().downcast_ref::<Self>() else {
            return Ok(false);
        };
        let value = source.0.load(Ordering::SeqCst);
        if value == 99 {
            return Err(VmError::InvalidArgument("rejected replacement"));
        }
        self.0.store(value, Ordering::SeqCst);
        Ok(true)
    }
}

#[test]
fn opt_in_assignment_keeps_alias_identity_ordinary_values_and_root_accounting() {
    for local in [false, true] {
        let mut vm = Vm::new().unwrap();
        let old = vm.allocate(SharedReference(AtomicUsize::new(1))).unwrap();
        let new = vm.allocate(SharedReference(AtomicUsize::new(2))).unwrap();
        let globals = vm.new_dict().unwrap();
        vm.dict_set(globals, text("alias"), Value::Object(old))
            .unwrap();
        let (store, load) = if local {
            (Opcode::StoreFast, Opcode::LoadFast)
        } else {
            (Opcode::StoreGlobal, Opcode::LoadGlobal)
        };
        let code = make_code(
            &mut vm,
            &[
                op(Opcode::LoadConst, 0),
                op(store, 0),
                op(Opcode::LoadConst, 1),
                op(store, 0),
                op(load, 0),
                simple(Opcode::ReturnValue),
            ],
            vec![Value::Object(old), Value::Object(new)],
            if local {
                CodeLayout {
                    locals: vec!["value".into()],
                    ..CodeLayout::default()
                }
            } else {
                CodeLayout {
                    names: vec!["value".into()],
                    ..CodeLayout::default()
                }
            },
        );
        let value = vm.execute(code, globals).unwrap();
        assert_eq!(value, Value::Object(old));
        assert_eq!(
            vm.dict_get(globals, &text("alias")).unwrap(),
            Some(Value::Object(old))
        );
        assert_eq!(
            vm.payload::<SharedReference>(old, "shared-reference")
                .unwrap()
                .0
                .load(Ordering::SeqCst),
            2
        );
        vm.release_value(value).unwrap();
        vm.release(code).unwrap();
        vm.dict_clear(globals).unwrap();
        vm.release(globals).unwrap();
        vm.release(old).unwrap();
        vm.release(new).unwrap();
        assert_eq!(vm.object_count(), 0);
    }
}

#[test]
fn failed_opt_in_assignment_preserves_target_and_cleans_execution_roots() {
    let mut vm = Vm::new().unwrap();
    let old = vm.allocate(SharedReference(AtomicUsize::new(1))).unwrap();
    let rejected = vm.allocate(SharedReference(AtomicUsize::new(99))).unwrap();
    let globals = vm.new_dict().unwrap();
    vm.dict_set(globals, text("value"), Value::Object(old))
        .unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::StoreGlobal, 0),
            op(Opcode::LoadConst, 1),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Object(rejected), Value::Nil],
        CodeLayout {
            names: vec!["value".into()],
            ..CodeLayout::default()
        },
    );
    assert!(vm.execute(code, globals).is_err());
    assert_eq!(
        vm.payload::<SharedReference>(old, "shared-reference")
            .unwrap()
            .0
            .load(Ordering::SeqCst),
        1
    );
    assert_eq!(
        vm.dict_get(globals, &text("value")).unwrap(),
        Some(Value::Object(old))
    );
    vm.release(code).unwrap();
    vm.dict_clear(globals).unwrap();
    vm.release(globals).unwrap();
    vm.release(old).unwrap();
    vm.release(rejected).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn wordcode_extended_operands_decode_and_execute_without_truncation() {
    let encoded = Instruction::encode_all(&[op(Opcode::LoadConst, 0x01020304)]).unwrap();
    assert_eq!(encoded, vec![255, 1, 255, 2, 255, 3, 1, 4]);
    let mut vm = Vm::new().unwrap();
    let mut constants = vec![Value::Nil; 257];
    constants[256] = text("extended");
    let code = make_code(
        &mut vm,
        &[op(Opcode::LoadConst, 256), simple(Opcode::ReturnValue)],
        constants,
        CodeLayout::default(),
    );
    let executable = vm.payload::<EndorCodeObject>(code, "code").unwrap().code();
    assert_eq!(executable.instructions()[0].offset, 0);
    assert_eq!(executable.instructions()[0].next_offset, 2);
    assert_eq!(executable.stack_size(), 1);
    let globals = vm.new_dict().unwrap();
    assert_eq!(vm.execute(code, globals).unwrap(), text("extended"));
}

#[test]
fn malformed_wordcode_and_unaligned_jumps_are_rejected_at_construction() {
    for bytes in [
        vec![],
        vec![0],
        vec![254, 0],
        vec![255, 1],
        vec![255, 1, 255, 1, 255, 1, 255, 1, 1, 0],
        vec![13, 1],
    ] {
        assert!(matches!(
            EndorCode::new(bytes, vec![Value::Nil], vec![], vec![]),
            Err(VmError::InvalidBytecode { .. })
        ));
    }
    // Jump target 2 is inside a prefixed LOAD_CONST starting at code unit 1.
    let bytes = vec![14, 1, 255, 1, 1, 0, 13, 0];
    assert!(EndorCode::new(bytes, vec![Value::Nil; 257], vec![], vec![]).is_err());
    assert!(
        EndorCode::from_instructions(
            &[op(Opcode::LoadConst, 1), simple(Opcode::ReturnValue)],
            vec![Value::Nil],
            CodeLayout::default()
        )
        .is_err()
    );
}

#[test]
fn verifier_rejects_underflow_fallthrough_bad_cells_and_inconsistent_stack_joins() {
    let cases = [
        vec![simple(Opcode::PopTop), simple(Opcode::ReturnValue)],
        vec![op(Opcode::LoadConst, 0)],
        vec![op(Opcode::LoadConst, 0), op(Opcode::JumpBackward, 2)],
        vec![op(Opcode::LoadDeref, 0), simple(Opcode::ReturnValue)],
        vec![
            op(Opcode::LoadConst, 0),
            op(Opcode::PopJumpIfFalse, 2),
            op(Opcode::LoadConst, 0),
            op(Opcode::JumpForward, 1),
            simple(Opcode::Nop),
            op(Opcode::LoadConst, 0),
            simple(Opcode::ReturnValue),
        ],
    ];
    for instructions in cases {
        assert!(
            EndorCode::from_instructions(&instructions, vec![Value::Nil], CodeLayout::default())
                .is_err()
        );
    }
    let layout = CodeLayout {
        locals: vec!["captured".into()],
        cell_variables: vec!["captured".into()],
        ..CodeLayout::default()
    };
    assert!(
        EndorCode::from_instructions(
            &[op(Opcode::LoadFast, 0), simple(Opcode::ReturnValue)],
            vec![],
            layout
        )
        .is_err()
    );
}

#[test]
fn execute_moves_values_between_constants_local_slots_and_globals() {
    let mut vm = Vm::new().unwrap();
    assert_eq!(vm.object_count(), 0);
    let globals = vm.new_dict().unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::StoreFast, 0),
            op(Opcode::LoadFast, 0),
            op(Opcode::StoreGlobal, 0),
            op(Opcode::LoadGlobal, 0),
            simple(Opcode::ReturnValue),
        ],
        vec![text("hello")],
        CodeLayout {
            locals: vec!["local".into()],
            names: vec!["saved".into()],
            ..CodeLayout::default()
        },
    );
    assert_eq!(vm.execute(code, globals).unwrap(), text("hello"));
    assert_eq!(
        vm.dict_get(globals, &text("saved")).unwrap(),
        Some(text("hello"))
    );
    assert!(vm.last_traceback().is_empty());
    vm.release(code).unwrap();
    vm.release(globals).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[derive(Debug)]
struct Tick(Arc<AtomicUsize>);
impl ObjectPayload for Tick {
    fn as_any(&self) -> &dyn Any {
        self
    }
    fn kind_name(&self) -> &'static str {
        "tick"
    }
    fn call(&self, arguments: &[Value]) -> Result<Value, VmError> {
        assert!(arguments.is_empty());
        Ok(Value::Bool(self.0.fetch_add(1, Ordering::SeqCst) < 3))
    }
}

#[test]
fn relative_branches_and_back_edges_execute_a_loop() {
    let mut vm = Vm::new().unwrap();
    let count = Arc::new(AtomicUsize::new(0));
    let tick = vm.allocate(Tick(count.clone())).unwrap();
    let globals = vm.new_dict().unwrap();
    vm.dict_set(globals, text("tick"), Value::Object(tick))
        .unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadGlobal, 0),
            simple(Opcode::PushNull),
            op(Opcode::Call, 0),
            op(Opcode::PopJumpIfFalse, 1),
            op(Opcode::JumpBackward, 5),
            op(Opcode::LoadConst, 0),
            simple(Opcode::ReturnValue),
        ],
        vec![text("done")],
        CodeLayout {
            names: vec!["tick".into()],
            ..CodeLayout::default()
        },
    );
    assert_eq!(vm.execute(code, globals).unwrap(), text("done"));
    assert_eq!(count.load(Ordering::SeqCst), 4);
}

#[test]
fn nested_language_calls_bind_defaults_and_return_owned_argument_objects() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let identity = make_code(
        &mut vm,
        &[op(Opcode::LoadFast, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            parameters: vec!["value".into()],
            locals: vec!["value".into()],
            ..CodeLayout::default()
        },
    );
    let default = vm.new_string("default").unwrap();
    let function = vm
        .new_function(
            "identity",
            identity,
            globals,
            vec![Value::Object(default)],
            vec![],
        )
        .unwrap();
    let before = vm.ref_count(default).unwrap();
    let returned = vm.call(function, &[]).unwrap();
    assert_eq!(returned, Value::Object(default));
    assert_eq!(vm.ref_count(default).unwrap(), before + 1);
    vm.release_value(returned).unwrap();
    assert_eq!(vm.ref_count(default).unwrap(), before);
    vm.dict_set(globals, text("identity"), Value::Object(function))
        .unwrap();
    let argument = vm.new_string("argument").unwrap();
    let wrapper = make_code(
        &mut vm,
        &[
            op(Opcode::LoadGlobal, 0),
            simple(Opcode::PushNull),
            op(Opcode::LoadConst, 0),
            op(Opcode::Call, 1),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Object(argument)],
        CodeLayout {
            names: vec!["identity".into()],
            ..CodeLayout::default()
        },
    );
    let before = vm.ref_count(argument).unwrap();
    let returned = vm.execute(wrapper, globals).unwrap();
    assert_eq!(returned, Value::Object(argument));
    assert_eq!(vm.ref_count(argument).unwrap(), before + 1);
    vm.release_value(returned).unwrap();
    assert_eq!(vm.ref_count(argument).unwrap(), before);
}

#[test]
fn argument_count_and_foreign_argument_failures_do_not_retain_inputs() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let code = make_code(
        &mut vm,
        &[op(Opcode::LoadFast, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            parameters: vec!["value".into()],
            locals: vec!["value".into()],
            ..CodeLayout::default()
        },
    );
    let function = vm
        .new_function("identity", code, globals, vec![], vec![])
        .unwrap();
    assert!(matches!(
        vm.call(function, &[]),
        Err(VmError::ArgumentCount {
            required: 1,
            provided: 0,
            ..
        })
    ));
    assert!(matches!(
        vm.call(function, &[Value::Nil, Value::Nil]),
        Err(VmError::ArgumentCount {
            maximum: 1,
            provided: 2,
            ..
        })
    ));
    let mut other = Vm::new().unwrap();
    let foreign = other.new_object().unwrap();
    let before = vm.ref_count(function).unwrap();
    assert_eq!(
        vm.call(function, &[Value::Object(foreign)]),
        Err(VmError::ForeignHandle)
    );
    assert_eq!(vm.ref_count(function).unwrap(), before);
}

#[test]
fn freshly_built_maps_and_their_children_survive_frame_cleanup() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let child = vm.new_string("owned by result").unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::LoadConst, 1),
            op(Opcode::BuildMap, 1),
            simple(Opcode::ReturnValue),
        ],
        vec![text("child"), Value::Object(child)],
        CodeLayout::default(),
    );
    vm.release(child).unwrap();
    let result = vm.execute(code, globals).unwrap();
    vm.release(code).unwrap();
    vm.release(globals).unwrap();
    let Value::Object(dictionary) = result else {
        panic!("expected a map");
    };
    assert_eq!(vm.ref_count(dictionary).unwrap(), 1);
    assert_eq!(
        vm.dict_get(dictionary, &text("child")).unwrap(),
        Some(Value::Object(child))
    );
    assert_eq!(vm.str(child).unwrap(), "owned by result");
    vm.release(dictionary).unwrap();
    assert_eq!(vm.object_count(), 0);
}

fn echo(arguments: &[Value]) -> Result<Value, VmError> {
    arguments
        .first()
        .cloned()
        .ok_or(VmError::InvalidArgument("expected an argument"))
}

#[test]
fn native_return_of_a_temporary_argument_is_retained_before_inputs_are_popped() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let function = vm
        .allocate(EndorNativeFunctionObject::new("echo", echo))
        .unwrap();
    vm.dict_set(globals, text("echo"), Value::Object(function))
        .unwrap();
    vm.release(function).unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadGlobal, 0),
            simple(Opcode::PushNull),
            op(Opcode::BuildMap, 0),
            op(Opcode::Call, 1),
            simple(Opcode::ReturnValue),
        ],
        vec![],
        CodeLayout {
            names: vec!["echo".into()],
            ..CodeLayout::default()
        },
    );
    let result = vm.execute(code, globals).unwrap();
    vm.release(code).unwrap();
    vm.release(globals).unwrap();
    assert_eq!(vm.object_count(), 1);
    vm.release_value(result).unwrap();
    assert_eq!(vm.object_count(), 0);
}

fn fail(_arguments: &[Value]) -> Result<Value, VmError> {
    Err(VmError::InvalidArgument("host failure"))
}

#[test]
fn native_failure_unwinds_temporary_roots_and_keeps_execution_locations() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let function = vm
        .allocate(EndorNativeFunctionObject::new("fail", fail))
        .unwrap();
    vm.dict_set(globals, text("fail"), Value::Object(function))
        .unwrap();
    let code = EndorCode::from_instructions(
        &[
            op(Opcode::LoadGlobal, 0),
            simple(Opcode::PushNull),
            op(Opcode::BuildMap, 0),
            op(Opcode::Call, 1),
            simple(Opcode::ReturnValue),
        ],
        vec![],
        CodeLayout {
            names: vec!["fail".into()],
            ..CodeLayout::default()
        },
    )
    .unwrap()
    .with_location("outer", "demo.endor", 12);
    let code = vm.new_code(code).unwrap();
    let before = vm.object_count();
    assert_eq!(
        vm.execute(code, globals),
        Err(VmError::InvalidArgument("host failure"))
    );
    assert_eq!(vm.object_count(), before);
    assert_eq!(vm.last_traceback()[0].function, "outer");
    assert_eq!(vm.last_traceback()[0].instruction_offset, 3);
    assert_eq!(vm.last_traceback()[0].filename, "demo.endor");
    assert_eq!(vm.last_traceback()[0].first_line, 12);
}

#[test]
fn recursion_uses_explicit_frames_and_unwinds_at_the_frame_limit() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadGlobal, 0),
            simple(Opcode::PushNull),
            op(Opcode::Call, 0),
            simple(Opcode::ReturnValue),
        ],
        vec![],
        CodeLayout {
            names: vec!["recurse".into()],
            ..CodeLayout::default()
        },
    );
    let function = vm
        .new_function("recurse", code, globals, vec![], vec![])
        .unwrap();
    vm.dict_set(globals, text("recurse"), Value::Object(function))
        .unwrap();
    let roots = vm.ref_count(function).unwrap();
    assert_eq!(
        vm.call_with_limits(
            function,
            &[],
            ExecutionLimits {
                max_frames: 64,
                max_instructions: 1000
            }
        ),
        Err(VmError::ExecutionLimit("frames"))
    );
    assert_eq!(vm.last_traceback().len(), 64);
    assert_eq!(vm.ref_count(function).unwrap(), roots);
    vm.release(function).unwrap();
    vm.release(code).unwrap();
    vm.release(globals).unwrap();
    assert_eq!(vm.collect_cycles(), 3);
}

#[test]
fn instruction_limit_stops_a_valid_infinite_loop_without_leaking_frames() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let code = make_code(
        &mut vm,
        &[op(Opcode::JumpBackward, 1)],
        vec![],
        CodeLayout::default(),
    );
    let before = vm.object_count();
    assert_eq!(
        vm.execute_with_limits(
            code,
            globals,
            ExecutionLimits {
                max_frames: 8,
                max_instructions: 3
            }
        ),
        Err(VmError::ExecutionLimit("instructions"))
    );
    assert_eq!(vm.object_count(), before);
    assert_eq!(vm.last_traceback().len(), 1);
}

#[test]
fn function_globals_shadow_builtins_and_capture_the_original_builtins_dictionary() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let builtins = vm.new_dict().unwrap();
    vm.dict_set(builtins, text("answer"), text("builtin"))
        .unwrap();
    vm.dict_set(globals, text("__builtins__"), Value::Object(builtins))
        .unwrap();
    let code = make_code(
        &mut vm,
        &[op(Opcode::LoadGlobal, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            names: vec!["answer".into()],
            ..CodeLayout::default()
        },
    );
    let function = vm
        .new_function("read", code, globals, vec![], vec![])
        .unwrap();
    let replacement = vm.new_dict().unwrap();
    vm.dict_set(globals, text("__builtins__"), Value::Object(replacement))
        .unwrap();
    vm.release(builtins).unwrap();
    assert_eq!(vm.call(function, &[]).unwrap(), text("builtin"));
    vm.dict_set(globals, text("answer"), text("global"))
        .unwrap();
    assert_eq!(vm.call(function, &[]).unwrap(), text("global"));
}

#[test]
fn shared_free_variable_cells_are_read_written_and_deleted_by_bytecode() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let cell = vm.new_cell(Some(text("first"))).unwrap();
    let read_code = make_code(
        &mut vm,
        &[op(Opcode::LoadDeref, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            free_variables: vec!["x".into()],
            ..CodeLayout::default()
        },
    );
    let write_code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadFast, 0),
            op(Opcode::StoreDeref, 1),
            op(Opcode::LoadConst, 0),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Nil],
        CodeLayout {
            parameters: vec!["value".into()],
            locals: vec!["value".into()],
            free_variables: vec!["x".into()],
            ..CodeLayout::default()
        },
    );
    let clear_code = make_code(
        &mut vm,
        &[
            op(Opcode::DeleteDeref, 0),
            op(Opcode::LoadConst, 0),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Nil],
        CodeLayout {
            free_variables: vec!["x".into()],
            ..CodeLayout::default()
        },
    );
    let read = vm
        .new_function("read", read_code, globals, vec![], vec![cell])
        .unwrap();
    let write = vm
        .new_function("write", write_code, globals, vec![], vec![cell])
        .unwrap();
    let clear = vm
        .new_function("clear", clear_code, globals, vec![], vec![cell])
        .unwrap();
    assert_eq!(vm.call(read, &[]).unwrap(), text("first"));
    vm.call(write, &[text("updated")]).unwrap();
    assert_eq!(vm.call(read, &[]).unwrap(), text("updated"));
    vm.call(clear, &[]).unwrap();
    assert_eq!(vm.call(read, &[]), Err(VmError::UnboundLocal("x".into())));
}

#[test]
fn captured_argument_cells_keep_their_contents_after_the_frame_returns() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let code = make_code(
        &mut vm,
        &[op(Opcode::LoadClosure, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            parameters: vec!["x".into()],
            locals: vec!["x".into()],
            cell_variables: vec!["x".into()],
            ..CodeLayout::default()
        },
    );
    let function = vm
        .new_function("capture", code, globals, vec![], vec![])
        .unwrap();
    let value = vm.new_string("captured").unwrap();
    let returned = vm.call(function, &[Value::Object(value)]).unwrap();
    vm.release(value).unwrap();
    let Value::Object(cell) = returned else {
        panic!("expected cell");
    };
    assert_eq!(vm.cell_get(cell).unwrap(), Value::Object(value));
    assert_eq!(vm.str(value).unwrap(), "captured");
    vm.release(cell).unwrap();
    assert!(matches!(vm.object(value), Err(VmError::InvalidHandle)));
}

#[test]
fn attribute_operations_and_stack_copies_transfer_roots_without_leaks() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadFast, 1),
            op(Opcode::LoadFast, 0),
            op(Opcode::StoreAttr, 0),
            op(Opcode::LoadFast, 0),
            op(Opcode::LoadAttr, 0),
            op(Opcode::Copy, 1),
            op(Opcode::Swap, 2),
            simple(Opcode::PopTop),
            simple(Opcode::ReturnValue),
        ],
        vec![],
        CodeLayout {
            parameters: vec!["record".into(), "value".into()],
            locals: vec!["record".into(), "value".into()],
            names: vec!["x".into()],
            ..CodeLayout::default()
        },
    );
    let function = vm
        .new_function("assign", code, globals, vec![], vec![])
        .unwrap();
    let record = vm.new_object().unwrap();
    let value = vm.new_string("value").unwrap();
    let returned = vm
        .call(function, &[Value::Object(record), Value::Object(value)])
        .unwrap();
    assert_eq!(vm.ref_count(value).unwrap(), 3); // host, attribute, return value
    vm.release_value(returned).unwrap();
    vm.release(record).unwrap();
    assert_eq!(vm.ref_count(value).unwrap(), 1);
}

#[test]
fn comparison_truth_and_forward_conditionals_use_runtime_values() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::LoadConst, 1),
            Instruction::compare(CompareOp::Lt),
            simple(Opcode::ToBool),
            simple(Opcode::UnaryNot),
            op(Opcode::PopJumpIfTrue, 2),
            op(Opcode::LoadConst, 2),
            simple(Opcode::ReturnValue),
            op(Opcode::LoadConst, 3),
            simple(Opcode::ReturnValue),
        ],
        vec![text("a"), text("b"), text("less"), text("other")],
        CodeLayout::default(),
    );
    assert_eq!(vm.execute(code, globals).unwrap(), text("less"));
}

#[test]
fn unbound_names_deleted_locals_and_invalid_null_values_fail_cleanly() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let missing = make_code(
        &mut vm,
        &[op(Opcode::LoadGlobal, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            names: vec!["missing".into()],
            ..CodeLayout::default()
        },
    );
    assert_eq!(
        vm.execute(missing, globals),
        Err(VmError::NameNotFound("missing".into()))
    );
    let deleted = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::StoreFast, 0),
            op(Opcode::DeleteFast, 0),
            op(Opcode::LoadFast, 0),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Nil],
        CodeLayout {
            locals: vec!["x".into()],
            ..CodeLayout::default()
        },
    );
    assert_eq!(
        vm.execute(deleted, globals),
        Err(VmError::UnboundLocal("x".into()))
    );
    let null = make_code(
        &mut vm,
        &[simple(Opcode::PushNull), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout::default(),
    );
    assert!(matches!(
        vm.execute(null, globals),
        Err(VmError::InvalidBytecode { .. })
    ));
    let success = return_constant(&mut vm, Value::Nil);
    assert_eq!(vm.execute(success, globals).unwrap(), Value::Nil);
    assert!(vm.last_traceback().is_empty());
}

#[test]
fn failed_map_construction_cleans_both_partial_map_and_temporary_input() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::BuildMap, 0),
            op(Opcode::BuildMap, 1),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Number(1_i64.into())],
        CodeLayout::default(),
    );
    let before = vm.object_count();
    assert_eq!(
        vm.execute(code, globals),
        Err(VmError::UnsupportedOperation("numeric hash"))
    );
    assert_eq!(vm.object_count(), before);
}

#[test]
fn implicit_receiver_slot_is_distinct_from_the_null_call_marker() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let function = vm
        .allocate(EndorNativeFunctionObject::new("echo", echo))
        .unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::LoadConst, 1),
            op(Opcode::Call, 0),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Object(function), Value::Nil],
        CodeLayout::default(),
    );
    // Nil is an actual implicit argument here, not the internal NULL marker.
    assert_eq!(vm.execute(code, globals).unwrap(), Value::Nil);
}

#[test]
fn function_creation_operands_round_trip_and_require_all_inputs() {
    assert_eq!(
        Instruction::encode_all(&[Instruction::make_function(1, 1)]).unwrap(),
        vec![255, 1, 255, 0, 28, 1]
    );
    assert_eq!(
        Instruction::encode_all(&[Instruction::make_function(u16::MAX, u16::MAX)]).unwrap(),
        vec![255, 255, 255, 255, 255, 255, 28, 255]
    );
    let code = EndorCode::from_instructions(
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::LoadConst, 0),
            op(Opcode::LoadConst, 0),
            Instruction::make_function(1, 1),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Nil],
        CodeLayout::default(),
    )
    .unwrap();
    assert_eq!(
        code.instructions()[3].instruction,
        Instruction::make_function(1, 1)
    );
    assert_eq!(code.instructions()[3].next_offset, 6);
    assert_eq!(code.stack_size(), 3);
    for (defaults, closure) in [(0, 0), (1, 0), (0, 1), (1, 1), (u16::MAX, u16::MAX)] {
        assert!(matches!(
            EndorCode::from_instructions(
                &[
                    Instruction::make_function(defaults, closure),
                    simple(Opcode::ReturnValue)
                ],
                vec![],
                CodeLayout::default(),
            ),
            Err(VmError::InvalidBytecode { .. })
        ));
    }
    for creation in [
        Instruction::make_function(1, 0),
        Instruction::make_function(0, 1),
    ] {
        assert!(
            EndorCode::from_instructions(
                &[
                    op(Opcode::LoadConst, 0),
                    creation,
                    simple(Opcode::ReturnValue)
                ],
                vec![Value::Nil],
                CodeLayout::default(),
            )
            .is_err()
        );
    }
}

#[test]
fn bytecode_defines_global_functions_and_calls_them_with_defaults() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let inner = EndorCode::from_instructions(
        &[op(Opcode::LoadFast, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            parameters: vec!["value".into()],
            locals: vec!["value".into()],
            ..CodeLayout::default()
        },
    )
    .unwrap()
    .with_location("identity", "functions.endor", 2);
    let inner = vm.new_code(inner).unwrap();
    let module = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::LoadConst, 1),
            Instruction::make_function(1, 0),
            op(Opcode::StoreGlobal, 0),
            op(Opcode::LoadGlobal, 0),
            simple(Opcode::PushNull),
            op(Opcode::Call, 0),
            simple(Opcode::ReturnValue),
        ],
        vec![text("default"), Value::Object(inner)],
        CodeLayout {
            names: vec!["identity".into()],
            ..CodeLayout::default()
        },
    );
    vm.release(inner).unwrap();
    assert_eq!(vm.execute(module, globals).unwrap(), text("default"));
    let Some(Value::Object(first)) = vm.dict_get(globals, &text("identity")).unwrap() else {
        panic!("expected a function");
    };
    vm.retain(first).unwrap();
    let data = vm
        .payload::<EndorFunctionObject>(first, "function")
        .unwrap();
    assert_eq!(data.name(), "identity");
    assert_eq!(data.code(), inner);
    assert_eq!(data.globals(), globals);
    assert_eq!(
        vm.call(first, &[text("explicit")]).unwrap(),
        text("explicit")
    );
    assert_eq!(vm.execute(module, globals).unwrap(), text("default"));
    let Some(Value::Object(second)) = vm.dict_get(globals, &text("identity")).unwrap() else {
        panic!("expected a second function");
    };
    assert_ne!(first, second);
    assert_eq!(
        vm.payload::<EndorFunctionObject>(second, "function")
            .unwrap()
            .code(),
        inner
    );
    vm.release(first).unwrap();
    vm.release(module).unwrap();
    vm.release(globals).unwrap();
    // The global function, its code and its globals form a collectible cycle.
    assert_eq!(vm.collect_cycles(), 3);
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn bytecode_function_defaults_keep_temporary_objects_alive_after_factory_returns() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let inner = make_code(
        &mut vm,
        &[op(Opcode::LoadFast, 1), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            parameters: vec!["required".into(), "defaulted".into(), "tag".into()],
            locals: vec!["required".into(), "defaulted".into(), "tag".into()],
            ..CodeLayout::default()
        },
    );
    let factory = make_code(
        &mut vm,
        &[
            op(Opcode::BuildMap, 0),
            op(Opcode::LoadConst, 1),
            op(Opcode::LoadConst, 0),
            Instruction::make_function(2, 0),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Object(inner), text("tag")],
        CodeLayout::default(),
    );
    vm.release(inner).unwrap();
    let Value::Object(function) = vm.execute(factory, globals).unwrap() else {
        panic!("expected a function");
    };
    vm.release(factory).unwrap();
    vm.release(globals).unwrap();
    assert!(matches!(
        vm.call(function, &[]),
        Err(VmError::ArgumentCount { required: 1, .. })
    ));
    let first = vm.call(function, &[Value::Nil]).unwrap();
    let second = vm.call(function, &[Value::Nil]).unwrap();
    assert_eq!(first, second); // Defaults are evaluated once per creation.
    let Value::Object(default) = first else {
        panic!("expected a default map");
    };
    assert_eq!(vm.ref_count(default).unwrap(), 3); // Function and two results.
    vm.release(function).unwrap();
    vm.release_value(first).unwrap();
    assert_eq!(vm.ref_count(default).unwrap(), 1);
    vm.release_value(second).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn bytecode_nested_functions_share_cells_and_bind_defaults_after_outer_returns() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let read = make_code(
        &mut vm,
        &[op(Opcode::LoadDeref, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            free_variables: vec!["x".into(), "sentinel".into()],
            ..CodeLayout::default()
        },
    );
    let write = make_code(
        &mut vm,
        &[
            op(Opcode::LoadFast, 0),
            op(Opcode::StoreDeref, 1),
            op(Opcode::LoadDeref, 1),
            simple(Opcode::ReturnValue),
        ],
        vec![],
        CodeLayout {
            parameters: vec!["value".into()],
            locals: vec!["value".into()],
            free_variables: vec!["x".into(), "sentinel".into()],
            ..CodeLayout::default()
        },
    );
    let outer = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::LoadClosure, 0),
            op(Opcode::LoadClosure, 1),
            op(Opcode::LoadConst, 1),
            Instruction::make_function(0, 2),
            op(Opcode::LoadConst, 2),
            op(Opcode::LoadConst, 3),
            op(Opcode::LoadClosure, 0),
            op(Opcode::LoadClosure, 1),
            op(Opcode::LoadConst, 4),
            Instruction::make_function(1, 2),
            op(Opcode::BuildMap, 2),
            simple(Opcode::ReturnValue),
        ],
        vec![
            text("read"),
            Value::Object(read),
            text("write"),
            text("default"),
            Value::Object(write),
        ],
        CodeLayout {
            parameters: vec!["x".into(), "sentinel".into()],
            locals: vec!["x".into(), "sentinel".into()],
            cell_variables: vec!["x".into(), "sentinel".into()],
            ..CodeLayout::default()
        },
    );
    let outer_function = vm
        .new_function("outer", outer, globals, vec![], vec![])
        .unwrap();
    let Value::Object(pair) = vm
        .call(outer_function, &[text("first"), text("sentinel")])
        .unwrap()
    else {
        panic!("expected a function pair");
    };
    for reference in [read, write, outer, outer_function, globals] {
        vm.release(reference).unwrap();
    }
    let Some(Value::Object(read)) = vm.dict_get(pair, &text("read")).unwrap() else {
        panic!("expected read");
    };
    let Some(Value::Object(write)) = vm.dict_get(pair, &text("write")).unwrap() else {
        panic!("expected write");
    };
    assert_eq!(
        vm.payload::<EndorFunctionObject>(read, "function")
            .unwrap()
            .closure(),
        vm.payload::<EndorFunctionObject>(write, "function")
            .unwrap()
            .closure(),
    );
    assert_eq!(vm.collect_cycles(), 0);
    assert_eq!(vm.call(read, &[]).unwrap(), text("first"));
    assert_eq!(vm.call(write, &[text("updated")]).unwrap(), text("updated"));
    assert_eq!(vm.call(read, &[]).unwrap(), text("updated"));
    assert_eq!(vm.call(write, &[]).unwrap(), text("default"));
    assert_eq!(vm.call(read, &[]).unwrap(), text("default"));
    vm.release(pair).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn bytecode_function_creation_rejects_bad_inputs_without_leaking_roots() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let plain = return_constant(&mut vm, Value::Nil);
    let captured = make_code(
        &mut vm,
        &[op(Opcode::LoadDeref, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            free_variables: vec!["x".into()],
            ..CodeLayout::default()
        },
    );
    let cell = vm.new_cell(None).unwrap();
    let mismatch = VmError::InvalidArgument("function defaults or closure do not match code");
    let cases = [
        (
            vec![op(Opcode::LoadConst, 0), Instruction::make_function(0, 0)],
            vec![Value::Nil],
            VmError::ObjectKindMismatch("code"),
        ),
        (
            vec![op(Opcode::BuildMap, 0), Instruction::make_function(0, 0)],
            vec![],
            VmError::ObjectKindMismatch("code"),
        ),
        (
            vec![simple(Opcode::PushNull), Instruction::make_function(0, 0)],
            vec![],
            invalid_null(),
        ),
        (
            vec![
                op(Opcode::BuildMap, 0),
                op(Opcode::LoadConst, 0),
                Instruction::make_function(1, 0),
            ],
            vec![Value::Object(plain)],
            mismatch.clone(),
        ),
        (
            vec![op(Opcode::LoadConst, 0), Instruction::make_function(0, 0)],
            vec![Value::Object(captured)],
            mismatch.clone(),
        ),
        (
            vec![
                op(Opcode::LoadConst, 0),
                op(Opcode::LoadConst, 1),
                Instruction::make_function(0, 1),
            ],
            vec![Value::Object(cell), Value::Object(plain)],
            mismatch,
        ),
        (
            vec![
                op(Opcode::LoadConst, 0),
                op(Opcode::LoadConst, 1),
                Instruction::make_function(0, 1),
            ],
            vec![Value::Nil, Value::Object(captured)],
            VmError::ObjectKindMismatch("cell"),
        ),
        (
            vec![
                op(Opcode::BuildMap, 0),
                op(Opcode::LoadConst, 0),
                Instruction::make_function(0, 1),
            ],
            vec![Value::Object(captured)],
            VmError::ObjectKindMismatch("cell"),
        ),
        (
            vec![
                simple(Opcode::PushNull),
                op(Opcode::LoadConst, 0),
                Instruction::make_function(0, 1),
            ],
            vec![Value::Object(captured)],
            invalid_null(),
        ),
        (
            vec![
                simple(Opcode::PushNull),
                op(Opcode::LoadConst, 0),
                Instruction::make_function(1, 0),
            ],
            vec![Value::Object(plain)],
            invalid_null(),
        ),
    ];
    for (mut instructions, constants, expected) in cases {
        instructions.push(simple(Opcode::ReturnValue));
        let code = make_code(&mut vm, &instructions, constants, CodeLayout::default());
        let count = vm.object_count();
        let roots =
            [plain, captured, cell, globals].map(|reference| vm.ref_count(reference).unwrap());
        let error = vm.execute(code, globals).unwrap_err();
        if matches!(expected, VmError::InvalidBytecode { .. }) {
            assert!(matches!(
                error,
                VmError::InvalidBytecode {
                    reason: "NULL call marker used as a value",
                    ..
                }
            ));
        } else {
            assert_eq!(error, expected);
        }
        assert_eq!(vm.object_count(), count);
        assert_eq!(
            [plain, captured, cell, globals].map(|reference| vm.ref_count(reference).unwrap()),
            roots
        );
        vm.release(code).unwrap();
    }
    for reference in [plain, captured, cell, globals] {
        vm.release(reference).unwrap();
    }
    assert_eq!(vm.object_count(), 0);
}

fn invalid_null() -> VmError {
    VmError::InvalidBytecode {
        offset: 0,
        reason: "NULL call marker used as a value",
    }
}

#[test]
fn bytecode_functions_capture_builtins_at_creation_and_share_live_globals() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let original = vm.new_dict().unwrap();
    let replacement = vm.new_dict().unwrap();
    vm.dict_set(original, text("answer"), text("original"))
        .unwrap();
    vm.dict_set(replacement, text("answer"), text("replacement"))
        .unwrap();
    vm.dict_set(globals, text("__builtins__"), Value::Object(original))
        .unwrap();
    let inner = make_code(
        &mut vm,
        &[op(Opcode::LoadGlobal, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            names: vec!["answer".into()],
            ..CodeLayout::default()
        },
    );
    let factory = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            Instruction::make_function(0, 0),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Object(inner)],
        CodeLayout::default(),
    );
    let Value::Object(first) = vm.execute(factory, globals).unwrap() else {
        panic!("expected first function");
    };
    vm.dict_set(globals, text("__builtins__"), Value::Object(replacement))
        .unwrap();
    let Value::Object(second) = vm.execute(factory, globals).unwrap() else {
        panic!("expected second function");
    };
    for reference in [original, replacement, factory, inner, globals] {
        vm.release(reference).unwrap();
    }
    assert_eq!(vm.call(first, &[]).unwrap(), text("original"));
    assert_eq!(vm.call(second, &[]).unwrap(), text("replacement"));
    vm.dict_set(globals, text("answer"), text("global"))
        .unwrap();
    assert_eq!(vm.call(first, &[]).unwrap(), text("global"));
    assert_eq!(vm.call(second, &[]).unwrap(), text("global"));
    vm.release(first).unwrap();
    vm.release(second).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn later_execution_failure_releases_a_new_function_and_its_temporary_default() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let inner = make_code(
        &mut vm,
        &[op(Opcode::LoadFast, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            parameters: vec!["value".into()],
            locals: vec!["value".into()],
            ..CodeLayout::default()
        },
    );
    let fail = vm
        .allocate(EndorNativeFunctionObject::new("fail", fail))
        .unwrap();
    let factory = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            simple(Opcode::PushNull),
            op(Opcode::BuildMap, 0),
            op(Opcode::LoadConst, 1),
            Instruction::make_function(1, 0),
            op(Opcode::Call, 1),
            simple(Opcode::ReturnValue),
        ],
        vec![Value::Object(fail), Value::Object(inner)],
        CodeLayout::default(),
    );
    vm.release(fail).unwrap();
    vm.release(inner).unwrap();
    let count = vm.object_count();
    assert_eq!(
        vm.execute(factory, globals),
        Err(VmError::InvalidArgument("host failure"))
    );
    assert_eq!(vm.object_count(), count);
    vm.release(factory).unwrap();
    vm.release(globals).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn suspended_read_only_call_keeps_roots_and_releases_them_on_completion() {
    use endor_core::ExecutionProgress;
    let mut vm = Vm::new().unwrap();
    let shared = vm.new_object().unwrap();
    vm.set_attr(shared, "value", Value::Number(7_i64.into()))
        .unwrap();
    let globals = vm.new_dict().unwrap();
    let mut instructions = vec![simple(Opcode::Nop); 16];
    instructions.extend([op(Opcode::LoadConst, 0), simple(Opcode::ReturnValue)]);
    let code = make_code(
        &mut vm,
        &instructions,
        vec![Value::Object(shared)],
        CodeLayout::default(),
    );
    let function = vm
        .new_function("sliced", code, globals, vec![], vec![])
        .unwrap();
    let mut progress = vm
        .start_read_only_call(
            function,
            &[],
            ExecutionLimits {
                max_frames: 8,
                max_instructions: 100,
            },
            1,
        )
        .unwrap();
    assert!(matches!(
        progress,
        ExecutionProgress::Pending { instructions: 1 }
    ));
    assert!(
        vm.set_attr(shared, "value", Value::Number(8_i64.into()))
            .is_err()
    );
    assert!(vm.call(function, &[]).is_err());
    vm.release(function).unwrap();
    vm.release(code).unwrap();
    vm.release(globals).unwrap();
    vm.release(shared).unwrap();
    vm.collect_cycles();
    loop {
        match progress {
            ExecutionProgress::Pending { .. } => progress = vm.resume_read_only_call(2).unwrap(),
            ExecutionProgress::Complete {
                value,
                instructions,
                ..
            } => {
                assert_eq!(instructions, 18);
                assert_eq!(value, Value::Object(shared));
                assert_eq!(
                    vm.get_attr(shared, "value").unwrap(),
                    Value::Number(7_i64.into())
                );
                vm.release_value(value).unwrap();
                break;
            }
        }
    }
    assert!(!vm.has_suspended_call());
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn suspended_call_cancellation_and_total_budget_restore_read_only_state() {
    let mut vm = Vm::new().unwrap();
    let shared = vm.new_object().unwrap();
    let globals = vm.new_dict().unwrap();
    let mut instructions = vec![simple(Opcode::Nop); 8];
    instructions.extend([op(Opcode::LoadConst, 0), simple(Opcode::ReturnValue)]);
    let code = make_code(
        &mut vm,
        &instructions,
        vec![Value::Object(shared)],
        CodeLayout::default(),
    );
    let function = vm
        .new_function("budget", code, globals, vec![], vec![])
        .unwrap();
    let roots = vm.ref_count(function).unwrap();
    vm.start_read_only_call(
        function,
        &[],
        ExecutionLimits {
            max_frames: 8,
            max_instructions: 3,
        },
        1,
    )
    .unwrap();
    assert!(vm.resume_read_only_call(0).is_err());
    assert!(vm.has_suspended_call());
    vm.resume_read_only_call(1).unwrap();
    assert_eq!(
        vm.resume_read_only_call(1).unwrap_err(),
        VmError::ExecutionLimit("instructions")
    );
    assert!(!vm.has_suspended_call());
    assert_eq!(vm.ref_count(function).unwrap(), roots);
    vm.set_attr(shared, "after", Value::Bool(true)).unwrap();
    vm.start_read_only_call(function, &[], ExecutionLimits::default(), 1)
        .unwrap();
    assert!(vm.cancel_read_only_call().unwrap());
    assert!(!vm.cancel_read_only_call().unwrap());
    assert_eq!(vm.ref_count(function).unwrap(), roots);
    vm.set_attr(shared, "after", Value::Bool(false)).unwrap();
    vm.release(function).unwrap();
    vm.release(code).unwrap();
    vm.release(globals).unwrap();
    vm.release(shared).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn managed_coroutines_interleave_without_replaying_writes() {
    use endor_core::CoroutineProgress;
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::StoreGlobal, 0),
            op(Opcode::LoadConst, 1),
            op(Opcode::StoreGlobal, 1),
            op(Opcode::LoadConst, 2),
            simple(Opcode::ReturnValue),
        ],
        vec![text("first"), text("second"), Value::Nil],
        CodeLayout {
            names: vec!["x".into(), "y".into()],
            ..CodeLayout::default()
        },
    );
    let function = vm
        .new_function("work", code, globals, vec![], vec![])
        .unwrap();
    let first = vm
        .new_coroutine(function, &[], ExecutionLimits::default())
        .unwrap();
    let second = vm
        .new_coroutine(function, &[], ExecutionLimits::default())
        .unwrap();
    assert!(matches!(
        vm.resume_coroutine(first, 2).unwrap(),
        CoroutineProgress::Pending { instructions: 2 }
    ));
    assert!(matches!(
        vm.resume_coroutine(second, 2).unwrap(),
        CoroutineProgress::Pending { instructions: 2 }
    ));
    vm.dict_set(globals, text("x"), text("interleaved"))
        .unwrap();
    assert!(matches!(
        vm.resume_coroutine(first, 16).unwrap(),
        CoroutineProgress::Complete {
            value: Value::Nil,
            instructions: 6
        }
    ));
    assert_eq!(
        vm.dict_get(globals, &text("x")).unwrap(),
        Some(text("interleaved"))
    );
    assert_eq!(
        vm.dict_get(globals, &text("y")).unwrap(),
        Some(text("second"))
    );
    assert!(vm.cancel_coroutine(second).unwrap());
    assert!(!vm.cancel_coroutine(second).unwrap());
    assert!(vm.resume_coroutine(first, 1).is_err());
    for object in [first, second, function, code, globals] {
        vm.release(object).unwrap();
    }
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn parked_coroutine_cycles_are_collectable_without_cancellation() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let code = return_constant(&mut vm, Value::Nil);
    let function = vm
        .new_function("cycle", code, globals, vec![], vec![])
        .unwrap();
    let coroutine = vm
        .new_coroutine(function, &[], ExecutionLimits::default())
        .unwrap();
    vm.dict_set(globals, text("task"), Value::Object(coroutine))
        .unwrap();
    for object in [coroutine, function, code, globals] {
        vm.release(object).unwrap();
    }
    assert!(vm.collect_cycles() > 0);
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn managed_coroutine_hard_budget_accumulates_and_error_releases_frames() {
    use endor_core::CoroutineProgress;
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let code = return_constant(&mut vm, Value::Nil);
    let function = vm
        .new_function("limited", code, globals, vec![], vec![])
        .unwrap();
    let coroutine = vm
        .new_coroutine(
            function,
            &[],
            ExecutionLimits {
                max_frames: 4,
                max_instructions: 1,
            },
        )
        .unwrap();
    assert!(matches!(
        vm.resume_coroutine(coroutine, 1).unwrap(),
        CoroutineProgress::Pending { instructions: 1 }
    ));
    assert!(matches!(
        vm.resume_coroutine(coroutine, 1),
        Err(VmError::ExecutionLimit("instructions"))
    ));
    assert!(!vm.last_traceback().is_empty());
    assert!(!vm.cancel_coroutine(coroutine).unwrap());
    for object in [coroutine, function, code, globals] {
        vm.release(object).unwrap();
    }
    assert_eq!(vm.object_count(), 0);
}

#[derive(Debug)]
struct AwaitGate {
    ready: Arc<std::sync::atomic::AtomicBool>,
    value: Value,
}
impl ObjectPayload for AwaitGate {
    fn as_any(&self) -> &dyn Any {
        self
    }
    fn kind_name(&self) -> &'static str {
        "await-gate"
    }
    fn trace(&self, visit: &mut dyn FnMut(ObjectRef)) {
        if let Value::Object(reference) = self.value {
            visit(reference);
        }
    }
    fn poll_await(&self) -> Result<endor_core::AwaitPoll, VmError> {
        Ok(if self.ready.load(Ordering::Acquire) {
            endor_core::AwaitPoll::Ready(self.value.clone())
        } else {
            endor_core::AwaitPoll::Pending
        })
    }
}

#[test]
fn await_keeps_operand_and_owned_object_result_without_replaying_prefix() {
    use endor_core::CoroutineProgress;
    let mut vm = Vm::new().unwrap();
    let ready = Arc::new(std::sync::atomic::AtomicBool::new(false));
    let value = vm.new_object().unwrap();
    vm.set_attr(value, "marker", text("kept")).unwrap();
    let gate = vm
        .allocate(AwaitGate {
            ready: ready.clone(),
            value: Value::Object(value),
        })
        .unwrap();
    let globals = vm.new_dict().unwrap();
    let code = make_code(
        &mut vm,
        &[
            op(Opcode::LoadConst, 0),
            op(Opcode::StoreGlobal, 0),
            op(Opcode::LoadConst, 1),
            simple(Opcode::Await),
            simple(Opcode::ReturnValue),
        ],
        vec![text("prefix"), Value::Object(gate)],
        CodeLayout {
            names: vec!["step".into()],
            ..CodeLayout::default()
        },
    );
    let function = vm
        .new_function("awaited", code, globals, vec![], vec![])
        .unwrap();
    let coroutine = vm
        .new_coroutine(function, &[], ExecutionLimits::default())
        .unwrap();
    assert!(
        matches!(vm.resume_coroutine(coroutine, 64).unwrap(), CoroutineProgress::Waiting { awaitable, .. } if awaitable == gate)
    );
    vm.release(value).unwrap();
    vm.release(gate).unwrap();
    vm.dict_set(globals, text("step"), text("interleaved"))
        .unwrap();
    vm.collect_cycles();
    ready.store(true, Ordering::Release);
    let CoroutineProgress::Complete { value: result, .. } =
        vm.resume_coroutine(coroutine, 64).unwrap()
    else {
        panic!("ready await must complete")
    };
    assert_eq!(
        vm.dict_get(globals, &text("step")).unwrap(),
        Some(text("interleaved"))
    );
    for object in [coroutine, function, code, globals] {
        vm.release(object).unwrap();
    }
    let Value::Object(reference) = result else {
        panic!("owned object result")
    };
    assert_eq!(vm.get_attr(reference, "marker").unwrap(), text("kept"));
    vm.release_value(result).unwrap();
    assert_eq!(vm.object_count(), 0);
}

#[test]
fn named_reads_ignore_unrelated_globals_but_track_missing_shadow_and_payload_kind() {
    let mut vm = Vm::new().unwrap();
    let globals = vm.new_dict().unwrap();
    let builtins = vm.new_dict().unwrap();
    vm.dict_set(builtins, text("name"), text("builtin"))
        .unwrap();
    vm.dict_set(globals, text("__builtins__"), Value::Object(builtins))
        .unwrap();
    let code = make_code(
        &mut vm,
        &[op(Opcode::LoadGlobal, 0), simple(Opcode::ReturnValue)],
        vec![],
        CodeLayout {
            names: vec!["name".into()],
            ..CodeLayout::default()
        },
    );
    let function = vm
        .new_function("read-name", code, globals, vec![], vec![])
        .unwrap();
    let endor_core::ExecutionProgress::Complete {
        value,
        reads,
        dependencies,
        ..
    } = vm
        .start_read_only_call(function, &[], ExecutionLimits::default(), 64)
        .unwrap()
    else {
        panic!("complete")
    };
    assert_eq!(value, text("builtin"));
    assert!(reads.contains(&globals) && reads.contains(&builtins));
    vm.release_value(value).unwrap();
    vm.dict_set(globals, text("_"), text("unrelated")).unwrap();
    assert!(
        dependencies
            .iter()
            .all(|dependency| vm.object_store().read_dependency_valid(dependency))
    );
    vm.dict_set(globals, text("name"), text("shadow")).unwrap();
    assert!(
        dependencies
            .iter()
            .any(|dependency| !vm.object_store().read_dependency_valid(dependency))
    );
    vm.dict_delete(globals, &text("name")).unwrap();
    assert!(
        dependencies
            .iter()
            .all(|dependency| vm.object_store().read_dependency_valid(dependency))
    );
    vm.dict_set(builtins, text("name"), text("changed"))
        .unwrap();
    assert!(
        dependencies
            .iter()
            .any(|dependency| !vm.object_store().read_dependency_valid(dependency))
    );
    for object in [function, code, globals, builtins] {
        vm.release(object).unwrap();
    }
    assert_eq!(vm.object_count(), 0);
    assert!(
        dependencies
            .iter()
            .any(|dependency| !vm.object_store().read_dependency_valid(dependency))
    );
}

#[test]
fn precise_nested_regions_replay_borrowed_dependencies_without_hiding_full_dict_reads() {
    let mut vm = endor_core::ObjectStore::new().unwrap();
    let globals = vm.new_dict().unwrap();
    vm.dict_set(globals, text("name"), text("value")).unwrap();
    let scope = vm.begin_read_only();
    let token = vm.begin_read_tracking().unwrap();
    vm.dict_get_name(globals, "name").unwrap();
    let tracked = vm.end_read_tracking_precise(token).unwrap();
    assert!(
        tracked
            .accesses
            .iter()
            .any(|access| access.object == globals)
    );
    for dependency in &tracked.dependencies {
        assert!(vm.read_dependency_valid(dependency));
    }
    let reads = vm.end_read_only_precise(scope).unwrap();
    vm.dict_set(globals, text("other"), Value::Nil).unwrap();
    assert!(
        reads
            .dependencies
            .iter()
            .all(|dependency| vm.read_dependency_valid(dependency))
    );
    let scope = vm.begin_read_only();
    vm.dict_items(globals).unwrap();
    let reads = vm.end_read_only_precise(scope).unwrap();
    vm.dict_set(globals, text("third"), Value::Nil).unwrap();
    assert!(
        reads
            .dependencies
            .iter()
            .any(|dependency| !vm.read_dependency_valid(dependency))
    );
    vm.release(globals).unwrap();
    assert_eq!(vm.object_count(), 0);
}