#![allow(clippy::arc_with_non_send_sync)]

use std::sync::Arc;

use oxide_compiler::module::CompiledModule;
use oxide_compiler::opcode::{self, OpCode};
use smallvec::SmallVec;

pub use crate::bindings::init_kernel_builtins;
use crate::coercion;
use crate::native::{NativeFn, NativeResult};
use oxide_kernel::kernel::OxideKernel;
use oxide_kernel::shape_forge::EMPTY_SHAPE_ID;
use oxide_types::error::{JsError, JsErrorKind};
use oxide_types::mem::{Epoch, P};
use oxide_types::object::{JsObject, NativeFnPtr};
use oxide_types::value::JsValue;

/// Convert a `NativeFnPtr` to a callable `NativeFn`.
///
/// # Safety
/// The pointer stored in `ptr` must have been created from a valid `NativeFn` fn-item.
/// This is the single point in the codebase where `NativeFnPtr → NativeFn` coercion happens.
#[inline(always)]
pub(crate) unsafe fn native_fn_ptr_to_fn(ptr: NativeFnPtr) -> NativeFn {
    std::mem::transmute::<*const (), NativeFn>(ptr.as_ptr())
}

fn js_error_kind(kind: &'static str) -> JsErrorKind {
    match kind {
        "TypeError" => JsErrorKind::TypeError,
        "RangeError" => JsErrorKind::RangeError,
        "ReferenceError" => JsErrorKind::ReferenceError,
        "SyntaxError" => JsErrorKind::SyntaxError,
        "URIError" => JsErrorKind::URIError,
        "EvalError" => JsErrorKind::EvalError,
        _ => JsErrorKind::Error,
    }
}

fn js_error_kind_name(kind: JsErrorKind) -> &'static str {
    match kind {
        JsErrorKind::TypeError => "TypeError",
        JsErrorKind::RangeError => "RangeError",
        JsErrorKind::ReferenceError => "ReferenceError",
        JsErrorKind::SyntaxError => "SyntaxError",
        JsErrorKind::Error => "Error",
        JsErrorKind::URIError => "URIError",
        JsErrorKind::EvalError => "EvalError",
    }
}

#[allow(unused_macros)]
macro_rules! throw_err {
    ($self:ident, $kind:ident, $msg:expr) => {{
        match $self.raise_error_kind(stringify!($kind), $msg) {
            Ok(()) => continue,
            Err(e) => return Err(e),
        }
    }};
}

macro_rules! binary_arith {
    ($self:ident, $a:expr, $b:expr, $rd:expr, $op:tt) => {{
        let l = coercion::to_number($self.regs[$a], $self.kernel.string_forge().as_ref());
        let r = coercion::to_number($self.regs[$b], $self.kernel.string_forge().as_ref());
        $self.regs[$rd] = JsValue::float(l $op r);
    }}
}

macro_rules! compound_arith {
    ($self:ident, $rd:expr, $a:expr, $op:tt) => {{
        let l = coercion::to_number($self.regs[$rd], $self.kernel.string_forge().as_ref());
        let r = coercion::to_number($self.regs[$a], $self.kernel.string_forge().as_ref());
        $self.regs[$rd] = JsValue::float(l $op r);
    }}
}

#[derive(Debug, Clone, Copy)]
pub enum FrameContinuation {
    None,
    AccessorGet { target_reg: u8 },
    AccessorSet,
}

pub struct CallFrame {
    pub return_addr: usize,
    pub function_name: u32,
    pub caller_reg_limit: u8,
    pub saved_regs: Box<[JsValue]>,
    pub saved_this: JsValue,
    pub saved_new_target: JsValue,
    pub callee: JsValue,
    pub construct_result_reg: Option<u8>,
    pub constructed_this: Option<JsValue>,
    pub is_derived_constructor: bool,
    pub continuation: FrameContinuation,
}

pub struct ForInIter<'bump> {
    pub keys: bumpalo::collections::Vec<'bump, JsValue>,
    pub index: usize,
}

pub struct TryHandler {
    pub catch_pc: Option<usize>,
    pub finally_pc: Option<usize>,
    pub frame_depth: usize,
}

/// Heap-allocated snapshot used by `call_bytecode_function_inline`.
/// Keeping it on the heap prevents Rust stack overflow when JS code
/// chains multiple sync bytecode calls (e.g. sort comparator, accessor).
pub(crate) struct InlineSyncState {
    pub(crate) regs: Box<[JsValue; 256]>,
    pub(crate) pc: usize,
    pub(crate) bytecode: Vec<opcode::Instr>,
    pub(crate) constants: Vec<JsValue>,
    pub(crate) active_reg_limit: u8,
    pub(crate) root_reg_limit: u8,
    pub(crate) try_stack: Vec<TryHandler>,
    pub(crate) frames: SmallVec<[CallFrame; 16]>,
    pub(crate) exception_value: Option<JsValue>,
    pub(crate) pending_exception: Option<JsValue>,
    pub(crate) pending_error_kind: Option<&'static str>,
    pub(crate) for_in_iters: Vec<*mut ForInIter<'static>>,
    pub(crate) saved_bytecode_stack: Vec<Vec<opcode::Instr>>,
    pub(crate) saved_constants_stack: Vec<Vec<JsValue>>,
}

pub struct Vm {
    pub(crate) regs: [JsValue; 256],
    pub(crate) pc: usize,
    pub(crate) bytecode: Vec<opcode::Instr>,
    pub(crate) constants: Vec<JsValue>,
    pub(crate) frames: SmallVec<[CallFrame; 16]>,
    pub for_in_iters: Vec<*mut ForInIter<'static>>,
    pub(crate) kernel: Arc<OxideKernel>,
    pub(crate) interned_strings: Vec<u32>,
    pub epoch: Epoch,
    pub object_prototype: P<JsObject>,
    pub math_rng_state: u64,
    pub(crate) sub_modules: Vec<CompiledModule>,
    pub(crate) sub_module_constants: Vec<Vec<JsValue>>,
    pub(crate) saved_bytecode_stack: Vec<Vec<opcode::Instr>>,
    pub(crate) saved_constants_stack: Vec<Vec<JsValue>>,
    pub(crate) try_stack: Vec<TryHandler>,
    pub(crate) exception_value: Option<JsValue>,
    pub(crate) pending_exception: Option<JsValue>,
    pub(crate) pending_error_kind: Option<&'static str>,
    pub(crate) symbol_counter: u32,
    pub(crate) symbol_descriptions: Vec<String>,
    #[allow(dead_code)]
    pub(crate) for_of_iters: Vec<*mut u8>,
    pub(crate) root_reg_limit: u8,
    pub(crate) active_reg_limit: u8,
    pub(crate) native_call_depth: usize,
    /// Set to Some(target_reg) when `ordinary_get` pushes a bytecode accessor frame.
    /// The dispatch loop checks this flag and skips writing `regs[target_reg]` from the
    /// call result — the value will be delivered by the RETURN handler instead.
    pub(crate) accessor_frame_target_reg: Option<u8>,
}

impl Vm {
    pub(crate) fn checked_object_ptr(
        &mut self, val: JsValue, error_msg: &str,
    ) -> Result<Option<*mut JsObject>, String> {
        if !val.is_object() {
            self.raise_type_error(error_msg)?;
            return Ok(None);
        }
        let ptr = val.as_js_object_ptr();
        let addr = ptr as usize;
        if ptr.is_null() || addr < 0x10000 || addr % std::mem::align_of::<JsObject>() != 0 {
            self.raise_type_error(error_msg)?;
            return Ok(None);
        }
        Ok(Some(ptr))
    }

    pub(crate) fn raise_error_kind(&mut self, kind: &'static str, msg: &str) -> Result<(), String> {
        self.raise_js_error(JsError::new(js_error_kind(kind), msg))
    }

    pub(crate) fn raise_js_error(&mut self, err: JsError) -> Result<(), String> {
        let kind = js_error_kind_name(err.kind);
        let error = match kind {
            "TypeError" => crate::builtins::error::create_type_error(self, &err.message),
            "ReferenceError" => crate::builtins::error::create_reference_error(self, &err.message),
            "SyntaxError" => crate::builtins::error::create_syntax_error(self, &err.message),
            _ => crate::builtins::error::create_error(self, &err.message),
        };
        self.exception_value = Some(error);
        self.pending_error_kind = Some(kind);
        self.unwind()
    }

    pub(crate) fn raise_type_error(&mut self, msg: &str) -> Result<(), String> {
        self.raise_error_kind("TypeError", msg)
    }

    pub fn step_rng(&mut self) {
        if self.math_rng_state == 0 {
            self.math_rng_state = std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap_or_default()
                .as_nanos() as u64;
        }
        self.math_rng_state = self
            .math_rng_state
            .wrapping_mul(6364136223846793005)
            .wrapping_add(1442695040888963407);
    }

    pub fn math_rng_value(&self) -> f64 {
        (self.math_rng_state >> 33) as f64 / (1u64 << 31) as f64
    }

    pub fn kernel(&self) -> &Arc<OxideKernel> {
        &self.kernel
    }

    pub(crate) fn is_object_prototype(&self, ptr: *const JsObject) -> bool {
        let proto_ptr = self.kernel.builtin_world().object_proto.as_ptr();
        std::ptr::eq(ptr, proto_ptr)
    }

    pub fn reg(&self, idx: u8) -> JsValue {
        self.regs[idx as usize]
    }

    pub fn set_reg(&mut self, idx: u8, val: JsValue) {
        self.regs[idx as usize] = val;
    }

    pub fn regs_mut(&mut self) -> &mut [JsValue; 256] {
        &mut self.regs
    }

    pub fn epoch_mut(&mut self) -> &mut Epoch {
        &mut self.epoch
    }

    pub fn epoch(&self) -> &Epoch {
        &self.epoch
    }

    pub fn lookup_str(&self, val: JsValue) -> Option<String> {
        if !val.is_string() {
            return None;
        }
        self.kernel.string_forge().lookup(val.as_string_index())
    }

    pub(crate) fn thrown_error_kind(&self, val: JsValue) -> &'static str {
        if !val.is_object() {
            return "Error";
        }
        let name_si = self.kernel.string_forge().intern("name").0;
        let obj = unsafe { &*val.as_js_object_ptr() };
        let Some(name_val) = self.resolve_property(obj, name_si) else {
            return "Error";
        };
        let Some(name) = self.lookup_str(name_val) else {
            return "Error";
        };
        match name.as_str() {
            "TypeError" => "TypeError",
            "ReferenceError" => "ReferenceError",
            "RangeError" => "RangeError",
            "SyntaxError" => "SyntaxError",
            "URIError" => "URIError",
            "EvalError" => "EvalError",
            "Error" => "Error",
            _ => "Error",
        }
    }

    pub(crate) fn property_key_si(&mut self, val: JsValue) -> u32 {
        if val.is_string() {
            return val.as_string_index();
        }
        let key = coercion::to_string(self.kernel.string_forge().as_ref(), val);
        self.kernel.string_forge().intern(&key).0
    }

    pub(crate) fn resolve_property(&self, obj: &JsObject, prop_name_si: u32) -> Option<JsValue> {
        let length_si = self.kernel.string_forge().intern("length").0;
        if obj.is_array() && prop_name_si == length_si {
            return Some(JsValue::int(obj.prop_count() as i32));
        }
        if let Some(pos) = self.kernel.shape_forge().lookup_position(obj.shape_id(), prop_name_si) {
            let val = obj.get_prop_at(pos);
            if !val.is_undefined() || obj.prop_vec_len() > pos as usize {
                return Some(val);
            }
        }
        let mut proto = obj.proto();
        while proto.is_object() {
            let proto_obj = unsafe { &*proto.as_js_object_ptr() };
            if let Some(pos) = self.kernel.shape_forge().lookup_position(proto_obj.shape_id(), prop_name_si) {
                let val = proto_obj.get_prop_at(pos);
                if !val.is_undefined() || proto_obj.prop_vec_len() > pos as usize {
                    return Some(val);
                }
            }
            proto = proto_obj.proto();
        }
        None
    }

    pub(crate) fn get_own_property_slot(&self, obj: &JsObject, prop_name_si: u32) -> Option<u32> {
        let length_si = self.kernel.string_forge().intern("length").0;
        if obj.is_array() && prop_name_si == length_si {
            return None;
        }
        self.kernel
            .shape_forge()
            .lookup_position(obj.shape_id(), prop_name_si)
            .and_then(|pos| {
                let val = obj.get_prop_at(pos);
                if !val.is_undefined() || obj.prop_vec_len() > pos as usize {
                    Some(pos)
                } else {
                    None
                }
            })
    }

    pub(crate) fn call_function_sync(
        &mut self, callee: JsValue, receiver: JsValue, args: &[JsValue],
    ) -> Result<JsValue, String> {
        if !callee.is_object() {
            return Err("TypeError: accessor is not callable".into());
        }
        let callee_obj = unsafe { &*callee.as_js_object_ptr() };
        if !callee_obj.is_function() {
            return Err("TypeError: accessor is not callable".into());
        }

        if let Some(native_fn) = callee_obj.native_fn() {
            if self.native_call_depth >= self.kernel.config.max_call_depth {
                return Err("RangeError: Maximum call stack size exceeded".into());
            }
            let saved_regs = self.regs;
            let saved_this = self.regs[254];
            let saved_callee = self.regs[253];
            self.regs[253] = receiver;
            self.regs[254] = callee;
            for (idx, arg) in args.iter().enumerate() {
                self.regs[240 + idx] = *arg;
            }
            let mut arg_regs = [0u8; 17];
            arg_regs[0] = 253;
            for idx in 0..args.len().min(16) {
                arg_regs[idx + 1] = 240 + idx as u8;
            }
            // SAFETY: native_fn was set via set_native_fn with a valid NativeFn pointer;
            // native_fn_ptr_to_fn is the single coercion point for NativeFnPtr → NativeFn.
            let func: NativeFn = unsafe { native_fn_ptr_to_fn(native_fn) };
            self.native_call_depth += 1;
            let result = func(self, &arg_regs[..args.len().min(16) + 1]);
            self.native_call_depth -= 1;
            self.regs = saved_regs;
            self.regs[254] = saved_this;
            self.regs[253] = saved_callee;
            return match result {
                NativeResult::Ok(val) => Ok(val),
                NativeResult::Err(err) => Err(self.error_text(err)),
                NativeResult::TailCall { callee, this, args } => self.call_function_sync(callee, this, &args),
            };
        }

        // Run bytecode function inline on self (same epoch) to prevent use-after-free.
        // A separate sub-VM would own a different epoch; returning a JsValue that contains
        // a pointer into the sub-VM epoch and then dropping the sub-VM causes a dangling
        // pointer / access violation in release builds.
        self.call_bytecode_function_inline(callee, callee_obj, receiver, args)
    }

    #[allow(clippy::too_many_arguments)]
    pub(crate) fn push_bytecode_frame(
        &mut self, callee: JsValue, this_value: JsValue, args: &[JsValue], construct_result_reg: Option<u8>,
        constructed_this: Option<JsValue>, new_target: JsValue, continuation: FrameContinuation,
    ) -> Result<(), String> {
        if !callee.is_object() {
            return Err("TypeError: CALL target is not callable".into());
        }
        let obj = unsafe { &*callee.as_js_object_ptr() };
        if !obj.is_function() || obj.sub_module_index() == 0 {
            return Err("TypeError: CALL target is not callable".into());
        }
        let sub_idx = obj.sub_module_index() as usize - 1;
        if sub_idx >= self.sub_modules.len() {
            return Err(format!(
                "CALL: sub_module_index {} out of bounds (max {})",
                sub_idx,
                self.sub_modules.len()
            ));
        }
        if self.frames.len() >= self.kernel.config.max_call_depth {
            return Err("RangeError: Maximum call stack size exceeded".into());
        }

        let sub_bytecode = self.sub_modules[sub_idx].bytecode.clone();
        let sub_n_args = self.sub_modules[sub_idx].n_args as usize;
        let sub_n_registers = self.sub_modules[sub_idx].n_registers;
        let sub_constants = self.sub_modules[sub_idx].constants.clone();
        let sub_param_base = self.sub_modules[sub_idx].param_base as usize;
        let sub_is_arrow = self.sub_modules[sub_idx].is_arrow;
        let caller_reg_limit = self.active_reg_limit.max(1);
        let saved_regs = self.regs[..caller_reg_limit as usize].to_vec().into_boxed_slice();
        let saved_this = self.regs[254];
        let saved_new_target = self.regs[255];

        for i in 0..sub_n_args {
            self.regs[sub_param_base + i] = args.get(i).copied().unwrap_or(JsValue::undefined());
        }
        self.regs[254] = if sub_is_arrow { obj.captured_this() } else { this_value };
        self.regs[255] = new_target;

        let converted_sub_constants = self.convert_constants(&sub_constants).map_err(String::from)?;
        self.saved_bytecode_stack.push(std::mem::take(&mut self.bytecode));
        self.saved_constants_stack.push(std::mem::take(&mut self.constants));

        let function_name = self.sub_modules[sub_idx]
            .function_name
            .as_deref()
            .map(|name| self.kernel.string_forge().intern(name).0)
            .unwrap_or(0);

        self.frames.push(CallFrame {
            return_addr: self.pc,
            function_name,
            caller_reg_limit,
            saved_regs,
            saved_this,
            saved_new_target,
            callee,
            construct_result_reg,
            constructed_this,
            is_derived_constructor: obj.is_derived_constructor(),
            continuation,
        });

        self.bytecode = sub_bytecode;
        self.constants = converted_sub_constants;
        for (name, reg) in &self.sub_modules[sub_idx].builtin_reg_map.clone() {
            let si = self.kernel.string_forge().intern(name.as_str()).0;
            let global = self.kernel.global_object();
            if let Some(pos) = self.kernel.shape_forge().lookup_position(global.shape_id(), si) {
                self.regs[*reg as usize] = global.get_prop_at(pos);
            }
        }

        self.active_reg_limit = sub_n_registers.max(1);
        self.pc = 0;
        Ok(())
    }

    pub(crate) fn dispatch(&mut self) -> Result<JsValue, String> {
        let mut steps: u64 = 0;
        loop {
            steps += 1;
            if let Some(max_steps) = self.kernel.config.max_steps {
                if steps > max_steps {
                    return Err(format!("VM step limit exceeded at pc={}", self.pc));
                }
            }
            if self.pc >= self.bytecode.len() {
                return Err("program counter out of bounds".into());
            }

            let instr = self.bytecode[self.pc];
            let op = opcode::opcode(instr);
            let rd = opcode::rd(instr) as usize;
            let a = opcode::a(instr) as usize;
            let b = opcode::b(instr) as usize;
            self.pc += 1;

            match op {
                OpCode::NOP => {}

                OpCode::HALT => return Ok(self.regs[0]),

                OpCode::LOAD_CONST => {
                    self.dispatch_load_const(rd, instr)?;
                }

                OpCode::ADD => {
                    self.dispatch_add(rd, a, b);
                }

                OpCode::SUB => {
                    binary_arith!(self, a, b, rd, -);
                }

                OpCode::MUL => {
                    binary_arith!(self, a, b, rd, *);
                }

                OpCode::DIV => {
                    binary_arith!(self, a, b, rd, /);
                }

                OpCode::MOD => {
                    binary_arith!(self, a, b, rd, %);
                }

                OpCode::NEG => {
                    let v = coercion::to_number(self.regs[a], self.kernel.string_forge().as_ref());
                    self.regs[rd] = JsValue::float(-v);
                }

                OpCode::BIT_AND => {
                    self.dispatch_bit_and(rd, a, b);
                }

                OpCode::BIT_OR => {
                    self.dispatch_bit_or(rd, a, b);
                }

                OpCode::BIT_XOR => {
                    self.dispatch_bit_xor(rd, a, b);
                }

                OpCode::SHL => {
                    self.dispatch_shl(rd, a, b);
                }

                OpCode::SHR => {
                    self.dispatch_shr(rd, a, b);
                }

                OpCode::USHR => {
                    self.dispatch_ushr(rd, a, b);
                }

                OpCode::BIT_NOT => {
                    self.dispatch_bit_not(rd, a);
                }

                OpCode::EQ => {
                    self.dispatch_eq(rd, a, b);
                }

                OpCode::NEQ => {
                    self.dispatch_neq(rd, a, b);
                }

                OpCode::LT => {
                    self.dispatch_lt(rd, a, b);
                }

                OpCode::GT => {
                    self.dispatch_gt(rd, a, b);
                }

                OpCode::LTE => {
                    self.dispatch_lte(rd, a, b);
                }

                OpCode::GTE => {
                    self.dispatch_gte(rd, a, b);
                }

                OpCode::STRICT_EQ => {
                    self.dispatch_strict_eq(rd, a, b);
                }

                OpCode::STRICT_NEQ => {
                    self.dispatch_strict_neq(rd, a, b);
                }

                OpCode::UNARY_PLUS => {
                    let v = coercion::to_number(self.regs[a], self.kernel.string_forge().as_ref());
                    self.regs[rd] = JsValue::float(v);
                }

                OpCode::JMP => {
                    let offset = opcode::offset16(instr) as isize;
                    self.pc = ((self.pc as isize) + offset - 1) as usize;
                }

                OpCode::JMP_IF_FALSE => {
                    let cond = coercion::to_boolean(self.regs[rd], self.kernel.string_forge().as_ref());
                    if !cond {
                        let offset = opcode::offset16(instr) as isize;
                        self.pc = ((self.pc as isize) + offset - 1) as usize;
                    }
                }

                OpCode::JMP_IF_TRUE => {
                    let cond = coercion::to_boolean(self.regs[rd], self.kernel.string_forge().as_ref());
                    if cond {
                        let offset = opcode::offset16(instr) as isize;
                        self.pc = ((self.pc as isize) + offset - 1) as usize;
                    }
                }

                OpCode::LOAD_VAR => {
                    if a == 254
                        && self.frames.last().map(|frame| frame.is_derived_constructor).unwrap_or(false)
                        && self.regs[a].is_undefined()
                    {
                        throw_err!(self, ReferenceError, "must call super constructor before using 'this'");
                    }
                    self.regs[rd] = self.regs[a];
                }

                OpCode::STORE_VAR => {
                    if b != 0 {
                        // const guard: check if already initialized
                        if !self.regs[rd].is_undefined() {
                            throw_err!(self, TypeError, "Assignment to constant variable");
                        }
                    }
                    self.regs[rd] = self.regs[a];
                }

                OpCode::CALL => match self.dispatch_call(rd, a, b) {
                    Ok(true) => continue,
                    Ok(false) => {}
                    Err(e) => return Err(e),
                },

                OpCode::CALL_NATIVE => {
                    self.dispatch_call_native(rd, a, b)?;
                }

                OpCode::NEW_EXPRESSION => match self.dispatch_new_expression(rd, a, b) {
                    Ok(true) => continue,
                    Ok(false) => {}
                    Err(e) => return Err(e),
                },

                OpCode::SUPER_CALL => {
                    let first_arg_reg = a as u8;
                    let ext = self.bytecode[self.pc];
                    self.pc += 1;
                    let arg_count = (ext & 0xFF) as usize;

                    let Some(frame) = self.frames.last() else {
                        throw_err!(self, ReferenceError, "super() used outside class constructor");
                    };
                    if !frame.is_derived_constructor {
                        throw_err!(self, ReferenceError, "super() used outside derived constructor");
                    }
                    if !self.regs[254].is_undefined() {
                        throw_err!(self, ReferenceError, "super() called more than once");
                    }
                    let Some(derived_this) = frame.constructed_this else {
                        throw_err!(self, ReferenceError, "super() without derived this");
                    };

                    let new_target = self.regs[255];
                    if !new_target.is_object() {
                        throw_err!(self, TypeError, "super() new.target is not an object");
                    }
                    let new_target_obj = unsafe { &*new_target.as_js_object_ptr() };
                    let super_ctor = new_target_obj.proto();
                    if !super_ctor.is_object() {
                        throw_err!(self, TypeError, "super constructor is not an object");
                    }
                    let super_obj = unsafe { &*super_ctor.as_js_object_ptr() };
                    if !super_obj.is_function() {
                        throw_err!(self, TypeError, "super constructor is not a function");
                    }

                    if super_obj.native_fn().is_some() {
                        self.regs[253] = derived_this;
                        self.regs[254] = super_ctor; // bind_dispatcher reads regs[254] as the wrapper callee
                        let (args_buf, len) = Self::build_native_args(first_arg_reg, arg_count, 253);
                        // SAFETY: native_fn was set via set_native_fn with a valid NativeFn pointer;
                        // native_fn_ptr_to_fn is the single coercion point for NativeFnPtr → NativeFn.
                        let func: NativeFn = unsafe { native_fn_ptr_to_fn(super_obj.native_fn().unwrap()) };
                        match func(self, &args_buf[..len]) {
                            NativeResult::Ok(val) => {
                                self.regs[254] = if val.is_object() { val } else { derived_this };
                                self.regs[rd] = self.regs[254];
                            }
                            NativeResult::Err(err_val) => {
                                self.exception_value = Some(err_val);
                                self.pending_error_kind = Some("Error");
                                match self.unwind() {
                                    Ok(()) => continue,
                                    Err(e) => return Err(e),
                                }
                            }
                            NativeResult::TailCall { callee, this, args } => {
                                // e.g. bound function: resolve the tail call, use its return
                                // value as the constructed instance (or fall back to derived_this).
                                match self.call_function_sync(callee, this, &args) {
                                    Ok(val) => {
                                        self.regs[254] = if val.is_object() { val } else { derived_this };
                                        self.regs[rd] = self.regs[254];
                                    }
                                    Err(e) => return Err(e),
                                }
                            }
                        }
                    } else if super_obj.sub_module_index() > 0 {
                        let sub_idx = super_obj.sub_module_index() as usize - 1;
                        if sub_idx >= self.sub_modules.len() {
                            return Err(format!(
                                "SUPER_CALL: sub_module_index {} out of bounds (max {})",
                                sub_idx,
                                self.sub_modules.len()
                            ));
                        }
                        if self.frames.len() >= self.kernel.config.max_call_depth {
                            return Err("RangeError: Maximum call stack size exceeded".into());
                        }

                        let sub_bytecode = self.sub_modules[sub_idx].bytecode.clone();
                        let sub_n_args = self.sub_modules[sub_idx].n_args as usize;
                        let sub_n_registers = self.sub_modules[sub_idx].n_registers;
                        let sub_constants = self.sub_modules[sub_idx].constants.clone();
                        let sub_param_base = self.sub_modules[sub_idx].param_base as usize;
                        let caller_reg_limit = self.active_reg_limit.max(1);
                        let saved_regs = self.regs[..caller_reg_limit as usize].to_vec().into_boxed_slice();
                        let saved_this = self.regs[254];
                        let saved_new_target = self.regs[255];

                        for i in 0..sub_n_args {
                            let src_reg = first_arg_reg.wrapping_add(i as u8) as usize;
                            self.regs[sub_param_base + i] = self.regs[src_reg];
                        }
                        self.regs[254] = derived_this;
                        self.regs[255] = new_target;

                        let converted_sub_constants = self.convert_constants(&sub_constants)?;
                        self.saved_bytecode_stack.push(std::mem::take(&mut self.bytecode));
                        self.saved_constants_stack.push(std::mem::take(&mut self.constants));
                        self.frames.push(CallFrame {
                            return_addr: self.pc,
                            function_name: self.sub_modules[sub_idx]
                                .function_name
                                .as_deref()
                                .map(|name| self.kernel.string_forge().intern(name).0)
                                .unwrap_or(0),
                            caller_reg_limit,
                            saved_regs,
                            saved_this,
                            saved_new_target,
                            callee: super_ctor,
                            construct_result_reg: Some(254),
                            constructed_this: Some(derived_this),
                            is_derived_constructor: super_obj.is_derived_constructor(),
                            continuation: FrameContinuation::None,
                        });

                        self.bytecode = sub_bytecode;
                        self.constants = converted_sub_constants;
                        for (name, reg) in &self.sub_modules[sub_idx].builtin_reg_map {
                            let si = self.kernel.string_forge().intern(name.as_str()).0;
                            let global = self.kernel.global_object();
                            if let Some(pos) = self.kernel.shape_forge().lookup_position(global.shape_id(), si) {
                                self.regs[*reg as usize] = global.get_prop_at(pos);
                            }
                        }
                        self.active_reg_limit = sub_n_registers.max(1);
                        self.pc = 0;
                        continue;
                    } else {
                        throw_err!(self, TypeError, "super constructor is not callable");
                    }
                }

                OpCode::SUPER_GET_PROP | OpCode::SUPER_STATIC_GET_PROP => {
                    let key_val = self.regs[b];
                    let prop_name_si = self.property_key_si(key_val);
                    let Some(frame) = self.frames.last() else {
                        throw_err!(self, ReferenceError, "super property used outside function");
                    };
                    if !frame.callee.is_object() {
                        throw_err!(self, ReferenceError, "super property has no home object");
                    }
                    let callee_obj = unsafe { &*frame.callee.as_js_object_ptr() };
                    let home_object = callee_obj.home_object();
                    if !home_object.is_object() {
                        throw_err!(self, ReferenceError, "super property has no home object");
                    }
                    let home_obj = unsafe { &*home_object.as_js_object_ptr() };
                    let super_base = home_obj.proto();
                    if !super_base.is_object() {
                        self.regs[rd] = JsValue::undefined();
                    } else {
                        let super_obj = unsafe { &*super_base.as_js_object_ptr() };
                        let val = self.ordinary_get_with_target(super_obj, prop_name_si, self.regs[a], rd as u8)?;
                        if self.accessor_frame_target_reg.take().is_none() {
                            self.regs[rd] = val;
                        }
                    }
                }

                OpCode::SET_HOME_OBJECT => {
                    let func_val = self.regs[rd];
                    let home_val = self.regs[a];
                    if !func_val.is_object() || !home_val.is_object() {
                        throw_err!(self, TypeError, "SET_HOME_OBJECT expects function and object");
                    }
                    let func_obj = unsafe { &mut *func_val.as_js_object_ptr() };
                    if !func_obj.is_function() {
                        throw_err!(self, TypeError, "SET_HOME_OBJECT target is not a function");
                    }
                    func_obj.set_home_object(home_val);
                }

                OpCode::DEFINE_ACCESSOR => {
                    self.dispatch_define_accessor(rd, a, b)?;
                }

                OpCode::RETURN => match self.dispatch_return(rd) {
                    Ok(Some(result)) => return Ok(result),
                    Ok(None) => {}
                    Err(e) => return Err(e),
                },

                OpCode::IC_GET_PROP
                | OpCode::IC_SET_PROP
                | OpCode::GET_PROP
                | OpCode::SET_PROP
                | OpCode::GET_PROP_DYNAMIC
                | OpCode::SET_PROP_DYNAMIC
                | OpCode::SET_ELEM => {
                    self.dispatch_property_op(op, rd, a, b)?;
                }

                OpCode::NEW_OBJECT => {
                    let proto_ptr = &*self.object_prototype as *const JsObject as *mut JsObject;
                    let obj = self
                        .epoch
                        .alloc(JsObject::new_empty(EMPTY_SHAPE_ID, JsValue::from_js_object(proto_ptr)));
                    self.regs[rd] = JsValue::object(obj as *mut u8);
                }

                OpCode::NEW_ARRAY => {
                    let proto_ptr = self.kernel.builtin_world().array_proto.as_ptr() as *mut JsObject;
                    let n = opcode::imm16(instr) as usize;
                    let bump = self.epoch.bump();
                    let obj = self.epoch.alloc(JsObject::new_array(
                        EMPTY_SHAPE_ID,
                        JsValue::from_js_object(proto_ptr),
                        n,
                        bump,
                    ));
                    self.regs[rd] = JsValue::object(obj as *mut u8);
                }

                OpCode::COMPOUND_ADD => {
                    let lhs = self.regs[rd];
                    let rhs = self.regs[a];
                    if lhs.is_string() || rhs.is_string() {
                        let ls = coercion::to_string(self.kernel.string_forge().as_ref(), lhs);
                        let rs = coercion::to_string(self.kernel.string_forge().as_ref(), rhs);
                        let concat = format!("{ls}{rs}");
                        self.regs[rd] = self.intern(&concat);
                    } else {
                        let ln = coercion::to_number(lhs, self.kernel.string_forge().as_ref());
                        let rn = coercion::to_number(rhs, self.kernel.string_forge().as_ref());
                        self.regs[rd] = JsValue::float(ln + rn);
                    }
                }

                OpCode::COMPOUND_SUB => {
                    compound_arith!(self, rd, a, -);
                }

                OpCode::COMPOUND_MUL => {
                    compound_arith!(self, rd, a, *);
                }

                OpCode::COMPOUND_DIV => {
                    compound_arith!(self, rd, a, /);
                }

                OpCode::COMPOUND_MOD => {
                    compound_arith!(self, rd, a, %);
                }

                OpCode::COMPOUND_EXP => {
                    let l = coercion::to_number(self.regs[rd], self.kernel.string_forge().as_ref());
                    let r = coercion::to_number(self.regs[a], self.kernel.string_forge().as_ref());
                    self.regs[rd] = JsValue::float(l.powf(r));
                }

                OpCode::COMPOUND_AND => {
                    self.dispatch_compound_bit_and(rd, a);
                }

                OpCode::COMPOUND_OR => {
                    self.dispatch_compound_bit_or(rd, a);
                }

                OpCode::COMPOUND_XOR => {
                    self.dispatch_compound_bit_xor(rd, a);
                }

                OpCode::COMPOUND_SHL => {
                    self.dispatch_compound_shl(rd, a);
                }

                OpCode::COMPOUND_SHR => {
                    self.dispatch_compound_shr(rd, a);
                }

                OpCode::COMPOUND_USHR => {
                    self.dispatch_compound_ushr(rd, a);
                }

                OpCode::TYPEOF => {
                    self.dispatch_typeof(rd, a);
                }

                OpCode::VOID => {
                    self.regs[rd] = JsValue::undefined();
                }

                OpCode::TEMPLATE_STR => {
                    self.dispatch_template_str(rd);
                }

                OpCode::DELETE_PROP_STATIC => {
                    let _ = self.bytecode[self.pc];
                    self.pc += 1;
                    throw_err!(self, TypeError, "property deletion not supported");
                }

                OpCode::DELETE_PROP_DYNAMIC => {
                    let _ = self.regs[a];
                    let _ = self.regs[b];
                    throw_err!(self, TypeError, "property deletion not supported");
                }

                OpCode::INSTANCEOF => {
                    self.dispatch_instanceof(rd, a, b)?;
                }

                OpCode::IN => {
                    self.dispatch_in(rd, a, b)?;
                }

                OpCode::NOT => {
                    self.dispatch_not(rd, a);
                }

                OpCode::AND => {
                    self.dispatch_and(rd, a, b);
                }

                OpCode::OR => {
                    self.dispatch_or(rd, a, b);
                }

                OpCode::INC_PRE => {
                    let n = coercion::to_number(self.regs[rd], self.kernel.string_forge().as_ref());
                    let result = JsValue::float(n + 1.0);
                    self.regs[rd] = result;
                    self.regs[a] = result;
                }

                OpCode::INC_POST => {
                    let n = coercion::to_number(self.regs[rd], self.kernel.string_forge().as_ref());
                    self.regs[a] = JsValue::float(n);
                    self.regs[rd] = JsValue::float(n + 1.0);
                }

                OpCode::DEC_PRE => {
                    let n = coercion::to_number(self.regs[rd], self.kernel.string_forge().as_ref());
                    let result = JsValue::float(n - 1.0);
                    self.regs[rd] = result;
                    self.regs[a] = result;
                }

                OpCode::DEC_POST => {
                    let n = coercion::to_number(self.regs[rd], self.kernel.string_forge().as_ref());
                    self.regs[a] = JsValue::float(n);
                    self.regs[rd] = JsValue::float(n - 1.0);
                }

                OpCode::MEMBER_INC
                | OpCode::MEMBER_DEC
                | OpCode::DYN_MEMBER_INC
                | OpCode::DYN_MEMBER_DEC
                | OpCode::COMPOUND_MEMBER_ADD
                | OpCode::COMPOUND_MEMBER_SUB
                | OpCode::COMPOUND_MEMBER_MUL
                | OpCode::COMPOUND_MEMBER_DIV
                | OpCode::COMPOUND_MEMBER_MOD
                | OpCode::COMPOUND_MEMBER_EXP => {
                    self.dispatch_member_op(op, rd, a, b)?;
                }

                OpCode::FOR_IN_INIT => {
                    self.dispatch_for_in_init(a)?;
                }

                OpCode::FOR_IN_NEXT => {
                    self.dispatch_for_in_next(rd)?;
                }

                OpCode::FOR_IN_DONE => {
                    self.dispatch_for_in_done(rd);
                }

                OpCode::FOR_IN_CLEANUP => {
                    self.dispatch_for_in_cleanup();
                }

                OpCode::FOR_OF_INIT => {
                    return Err("opcode FOR_OF_INIT not yet implemented".into());
                }

                OpCode::FOR_OF_NEXT => {
                    return Err("opcode FOR_OF_NEXT not yet implemented".into());
                }

                OpCode::FOR_OF_DONE => {
                    return Err("opcode FOR_OF_DONE not yet implemented".into());
                }

                OpCode::FOR_OF_CLOSE => {
                    return Err("opcode FOR_OF_CLOSE not yet implemented".into());
                }

                OpCode::THROW => match self.dispatch_throw(rd) {
                    Ok(true) => continue,
                    Ok(false) => {}
                    Err(e) => return Err(e),
                },

                OpCode::TRY_BEGIN => {
                    self.dispatch_try_begin(instr);
                }

                OpCode::TRY_END => {
                    self.dispatch_try_end();
                }

                OpCode::TRY_FINALLY_BEGIN => {
                    self.dispatch_try_finally_begin(instr);
                }

                OpCode::TRY_FINALLY_END => match self.dispatch_try_finally_end() {
                    Ok(true) => continue,
                    Ok(false) => {}
                    Err(e) => return Err(e),
                },

                _ => {
                    return Err(format!("opcode {op} not yet implemented"));
                }
            }
        }
    }
}

impl Default for Vm {
    fn default() -> Self {
        Self::new()
    }
}

#[cfg(test)]
mod tests {
    use super::{opcode, JsValue, TryHandler, Vm};
    use crate::native::NativeResult;
    use oxide_compiler::module::{CompiledModule, Constant};
    use oxide_types::object::NativeFnPtr;
    use oxide_types::object::{JsObject, PropAttributes};

    fn native_return_7(_vm: &mut Vm, _args: &[u8]) -> NativeResult {
        NativeResult::Ok(JsValue::int(7))
    }

    fn native_get_marker(vm: &mut Vm, args: &[u8]) -> NativeResult {
        let this_val = vm.reg(args[0]);
        if !this_val.is_object() {
            return NativeResult::Ok(JsValue::undefined());
        }
        let marker_si = vm.kernel.string_forge().intern("marker").0;
        let obj = unsafe { &*this_val.as_js_object_ptr() };
        NativeResult::Ok(vm.resolve_property(obj, marker_si).unwrap_or(JsValue::undefined()))
    }

    fn native_set_marker(vm: &mut Vm, args: &[u8]) -> NativeResult {
        let this_val = vm.reg(args[0]);
        let value = vm.reg(args[1]);
        if !this_val.is_object() {
            return NativeResult::Ok(JsValue::undefined());
        }
        let marker_si = vm.kernel.string_forge().intern("marker").0;
        let obj = unsafe { &mut *this_val.as_js_object_ptr() };
        vm.set_or_create_prop_value(obj, marker_si, value);
        NativeResult::Ok(JsValue::undefined())
    }

    fn native_function(vm: &mut Vm, f: crate::native::NativeFn) -> JsValue {
        let proto = vm.kernel.builtin_world().function_proto.as_ptr() as *mut JsObject;
        let mut obj = JsObject::new_empty(oxide_kernel::shape_forge::EMPTY_SHAPE_ID, JsValue::from_js_object(proto));
        obj.set_function(true);
        // SAFETY: f is a NativeFn fn-item; valid to store as NativeFnPtr.
        obj.set_native_fn(Some(unsafe { NativeFnPtr::from_raw(f as *const ()) }));
        JsValue::object(vm.epoch.alloc(obj) as *mut u8)
    }

    fn plain_object(vm: &mut Vm) -> JsValue {
        let proto = vm.kernel.builtin_world().object_proto.as_ptr() as *mut JsObject;
        let obj = JsObject::new_empty(oxide_kernel::shape_forge::EMPTY_SHAPE_ID, JsValue::from_js_object(proto));
        JsValue::object(vm.epoch.alloc(obj) as *mut u8)
    }

    fn add_accessor(vm: &mut Vm, obj_val: JsValue, name: &str, get: JsValue, set: JsValue) {
        let si = vm.kernel.string_forge().intern(name).0;
        let obj = unsafe { &mut *obj_val.as_js_object_ptr() };
        let shape_id = vm.kernel.shape_forge().make_shape(obj.shape_id(), si);
        obj.set_shape_id(shape_id);
        let pos = obj.push_prop(JsValue::undefined());
        obj.set_accessor_meta(pos, get, set, PropAttributes::DEFAULT_DATA);
        obj.bump_generation();
    }

    fn set_data(vm: &mut Vm, obj_val: JsValue, name: &str, val: JsValue) {
        let si = vm.kernel.string_forge().intern(name).0;
        let obj = unsafe { &mut *obj_val.as_js_object_ptr() };
        vm.set_or_create_prop_value(obj, si, val);
    }

    #[test]
    fn reset_clears_runtime_state_like_rerun() {
        let mut vm = Vm::new();
        vm.regs[1] = JsValue::int(7);
        vm.pc = 3;
        vm.frames.push(super::CallFrame {
            return_addr: 1,
            function_name: 0,
            caller_reg_limit: 2,
            saved_regs: vec![JsValue::undefined()].into_boxed_slice(),
            saved_this: JsValue::undefined(),
            saved_new_target: JsValue::undefined(),
            callee: JsValue::undefined(),
            construct_result_reg: None,
            constructed_this: None,
            is_derived_constructor: false,
            continuation: super::FrameContinuation::None,
        });
        vm.for_in_iters.push(std::ptr::dangling_mut::<super::ForInIter<'static>>());
        vm.for_of_iters.push(std::ptr::dangling_mut::<u8>());
        vm.saved_bytecode_stack
            .push(vec![opcode::encode(opcode::OpCode::HALT, 0, 0, 0)]);
        vm.saved_constants_stack.push(vec![JsValue::int(1)]);
        vm.try_stack.push(TryHandler {
            catch_pc: Some(1),
            finally_pc: None,
            frame_depth: 0,
        });
        vm.exception_value = Some(JsValue::int(2));
        vm.pending_exception = Some(JsValue::int(3));
        vm.pending_error_kind = Some("TypeError");

        vm.reset();

        assert_eq!(vm.pc, 0);
        assert!(vm.frames.is_empty());
        assert!(vm.for_in_iters.is_empty());
        assert!(vm.for_of_iters.is_empty());
        assert!(vm.saved_bytecode_stack.is_empty());
        assert!(vm.saved_constants_stack.is_empty());
        assert!(vm.try_stack.is_empty());
        assert!(vm.exception_value.is_none());
        assert!(vm.pending_exception.is_none());
        assert!(vm.pending_error_kind.is_none());
        assert!(vm.bytecode.is_empty());
        assert!(vm.constants.is_empty());
    }

    #[test]
    fn for_of_opcodes_fail_explicitly() {
        for (op, expected) in [
            (opcode::OpCode::FOR_OF_INIT, "opcode FOR_OF_INIT not yet implemented"),
            (opcode::OpCode::FOR_OF_NEXT, "opcode FOR_OF_NEXT not yet implemented"),
            (opcode::OpCode::FOR_OF_DONE, "opcode FOR_OF_DONE not yet implemented"),
            (opcode::OpCode::FOR_OF_CLOSE, "opcode FOR_OF_CLOSE not yet implemented"),
        ] {
            let module = CompiledModule {
                bytecode: vec![opcode::encode(op, 0, 0, 0), opcode::encode(opcode::OpCode::HALT, 0, 0, 0)],
                n_registers: 1,
                ..CompiledModule::new()
            };
            let mut vm = Vm::new();
            let err = vm.run(&module).expect_err("FOR_OF opcode should fail explicitly");
            assert_eq!(err, expected);
        }
    }

    #[test]
    fn invalid_regexp_constant_fails_explicitly() {
        let module = CompiledModule {
            constants: vec![Constant::RegExp("[".into(), "".into())],
            bytecode: vec![opcode::encode(opcode::OpCode::HALT, 0, 0, 0)],
            n_registers: 1,
            ..CompiledModule::new()
        };
        let mut vm = Vm::new();
        let err = vm.run(&module).expect_err("invalid RegExp constant should fail explicitly");
        assert!(err.contains("SyntaxError: Invalid regular expression"), "unexpected error: {err}");
    }

    #[test]
    fn invalid_regexp_constant_in_submodule_fails_explicitly() {
        let submodule = CompiledModule {
            constants: vec![Constant::RegExp("[".into(), "".into())],
            bytecode: vec![opcode::encode(opcode::OpCode::RETURN, 0, 0, 0)],
            n_registers: 1,
            ..CompiledModule::new()
        };
        let module = CompiledModule {
            constants: vec![Constant::BytecodeFunc(1), Constant::Undefined],
            bytecode: vec![
                opcode::encode(opcode::OpCode::LOAD_CONST, 0, 0, 0),
                opcode::encode(opcode::OpCode::LOAD_CONST, 1, 1, 0),
                opcode::encode(opcode::OpCode::CALL, 0, 1, 0),
                0,
                opcode::encode(opcode::OpCode::HALT, 0, 0, 0),
            ],
            n_registers: 2,
            sub_modules: vec![submodule],
            ..CompiledModule::new()
        };
        let mut vm = Vm::new();
        let err = vm
            .run(&module)
            .expect_err("invalid submodule RegExp constant should fail explicitly");
        assert!(err.contains("SyntaxError: Invalid regular expression"), "unexpected error: {err}");
    }

    #[test]
    fn write_ic_back_updates_three_extension_words() {
        let mut vm = Vm::new();
        vm.bytecode = vec![0, 0, 0];
        vm.pc = 3;
        vm.write_ic_back(0x1234_5678, 7);
        assert_eq!(vm.bytecode[0], 0x0034_5678);
        assert_eq!(vm.bytecode[1], 7);
        assert_eq!(vm.bytecode[2], 0);
    }

    #[test]
    fn unimplemented_profile_opcode_fails_explicitly() {
        let module = CompiledModule {
            bytecode: vec![
                opcode::encode(opcode::OpCode::PROFILE_TYPE, 0, 0, 0),
                opcode::encode(opcode::OpCode::HALT, 0, 0, 0),
            ],
            n_registers: 1,
            ..CompiledModule::new()
        };
        let mut vm = Vm::new();
        let err = vm.run(&module).expect_err("unimplemented opcode should fail explicitly");
        assert_eq!(err, "opcode PROFILE_TYPE not yet implemented");
    }

    #[test]
    fn ordinary_get_calls_own_native_getter() {
        let mut vm = Vm::new();
        let obj_val = plain_object(&mut vm);
        let getter = native_function(&mut vm, native_return_7);
        add_accessor(&mut vm, obj_val, "x", getter, JsValue::undefined());

        let x_si = vm.kernel.string_forge().intern("x").0;
        let obj = unsafe { &*obj_val.as_js_object_ptr() };
        let value = vm.ordinary_get(obj, x_si, obj_val).expect("getter");
        assert_eq!(value, JsValue::int(7));
    }

    #[test]
    fn ordinary_set_calls_own_native_setter() {
        let mut vm = Vm::new();
        let obj_val = plain_object(&mut vm);
        let setter = native_function(&mut vm, native_set_marker);
        add_accessor(&mut vm, obj_val, "x", JsValue::undefined(), setter);

        let x_si = vm.kernel.string_forge().intern("x").0;
        let obj = unsafe { &mut *obj_val.as_js_object_ptr() };
        vm.ordinary_set(obj, x_si, JsValue::int(9), obj_val).expect("setter");

        let marker_si = vm.kernel.string_forge().intern("marker").0;
        let obj = unsafe { &*obj_val.as_js_object_ptr() };
        assert_eq!(vm.resolve_property(obj, marker_si), Some(JsValue::int(9)));
    }

    #[test]
    fn inherited_getter_uses_original_receiver() {
        let mut vm = Vm::new();
        let proto_val = plain_object(&mut vm);
        let child_val = plain_object(&mut vm);
        let getter = native_function(&mut vm, native_get_marker);
        add_accessor(&mut vm, proto_val, "x", getter, JsValue::undefined());
        set_data(&mut vm, child_val, "marker", JsValue::int(42));
        unsafe {
            (*child_val.as_js_object_ptr()).set_proto(proto_val).expect("proto");
        }

        let x_si = vm.kernel.string_forge().intern("x").0;
        let child = unsafe { &*child_val.as_js_object_ptr() };
        let value = vm.ordinary_get(child, x_si, child_val).expect("getter");
        assert_eq!(value, JsValue::int(42));
    }

    #[test]
    fn inherited_setter_uses_original_receiver() {
        let mut vm = Vm::new();
        let proto_val = plain_object(&mut vm);
        let child_val = plain_object(&mut vm);
        let setter = native_function(&mut vm, native_set_marker);
        add_accessor(&mut vm, proto_val, "x", JsValue::undefined(), setter);
        unsafe {
            (*child_val.as_js_object_ptr()).set_proto(proto_val).expect("proto");
        }

        let x_si = vm.kernel.string_forge().intern("x").0;
        let child = unsafe { &mut *child_val.as_js_object_ptr() };
        vm.ordinary_set(child, x_si, JsValue::int(12), child_val).expect("setter");

        let marker_si = vm.kernel.string_forge().intern("marker").0;
        let child = unsafe { &*child_val.as_js_object_ptr() };
        let proto = unsafe { &*proto_val.as_js_object_ptr() };
        assert_eq!(vm.resolve_property(child, marker_si), Some(JsValue::int(12)));
        assert_eq!(vm.resolve_property(proto, marker_si), None);
    }

    #[test]
    fn deep_inherited_setter_uses_original_receiver() {
        let mut vm = Vm::new();
        let grand_proto_val = plain_object(&mut vm);
        let proto_val = plain_object(&mut vm);
        let child_val = plain_object(&mut vm);
        let setter = native_function(&mut vm, native_set_marker);
        add_accessor(&mut vm, grand_proto_val, "x", JsValue::undefined(), setter);
        unsafe {
            (*proto_val.as_js_object_ptr()).set_proto(grand_proto_val).expect("proto");
            (*child_val.as_js_object_ptr()).set_proto(proto_val).expect("proto");
        }

        let x_si = vm.kernel.string_forge().intern("x").0;
        let child = unsafe { &mut *child_val.as_js_object_ptr() };
        vm.ordinary_set(child, x_si, JsValue::int(15), child_val).expect("setter");

        let marker_si = vm.kernel.string_forge().intern("marker").0;
        let child = unsafe { &*child_val.as_js_object_ptr() };
        assert_eq!(vm.resolve_property(child, marker_si), Some(JsValue::int(15)));
    }

    #[test]
    fn ordinary_data_property_still_reads_and_writes_without_meta() {
        let mut vm = Vm::new();
        let obj_val = plain_object(&mut vm);
        set_data(&mut vm, obj_val, "x", JsValue::int(1));

        let x_si = vm.kernel.string_forge().intern("x").0;
        let obj = unsafe { &mut *obj_val.as_js_object_ptr() };
        assert!(!obj.has_prop_meta());
        assert_eq!(vm.ordinary_get(obj, x_si, obj_val).expect("get"), JsValue::int(1));
        vm.ordinary_set(obj, x_si, JsValue::int(2), obj_val).expect("set");
        assert_eq!(vm.ordinary_get(obj, x_si, obj_val).expect("get"), JsValue::int(2));
    }
}