/*!
 * VM Instruction Handlers - Extracted from execute_instruction for better modularity
 */

use crate::mir::{ConstValue, BinaryOp, CompareOp, UnaryOp, ValueId, BasicBlockId, TypeOpKind, MirType};
use crate::box_trait::{NyashBox, BoolBox, VoidBox};
use crate::boxes::ArrayBox;
use std::sync::Arc;
use super::{VM, VMValue, VMError};
use super::vm::ControlFlow;

impl VM {
    /// Execute a constant instruction
    pub(super) fn execute_const(&mut self, dst: ValueId, value: &ConstValue) -> Result<ControlFlow, VMError> {
        let vm_value = VMValue::from(value);
        self.set_value(dst, vm_value);
        Ok(ControlFlow::Continue)
    }

    /// Execute a binary operation instruction
    pub(super) fn execute_binop(&mut self, dst: ValueId, op: &BinaryOp, lhs: ValueId, rhs: ValueId) -> Result<ControlFlow, VMError> {
        let left = self.get_value(lhs)?;
        let right = self.get_value(rhs)?;
        let result = self.execute_binary_op(op, &left, &right)?;
        self.set_value(dst, result);
        Ok(ControlFlow::Continue)
    }

    /// Execute a unary operation instruction
    pub(super) fn execute_unaryop(&mut self, dst: ValueId, op: &UnaryOp, operand: ValueId) -> Result<ControlFlow, VMError> {
        let operand_val = self.get_value(operand)?;
        let result = self.execute_unary_op(op, &operand_val)?;
        self.set_value(dst, result);
        Ok(ControlFlow::Continue)
    }

    /// Execute a comparison instruction
    pub(super) fn execute_compare(&mut self, dst: ValueId, op: &CompareOp, lhs: ValueId, rhs: ValueId) -> Result<ControlFlow, VMError> {
        let left = self.get_value(lhs)?;
        let right = self.get_value(rhs)?;
        let result = self.execute_compare_op(op, &left, &right)?;
        self.set_value(dst, VMValue::Bool(result));
        Ok(ControlFlow::Continue)
    }

    /// Execute a print instruction
    pub(super) fn execute_print(&self, value: ValueId) -> Result<ControlFlow, VMError> {
        let val = self.get_value(value)?;
        println!("{}", val.to_string());
        Ok(ControlFlow::Continue)
    }

    /// Execute control flow instructions (Jump, Branch, Return)
    pub(super) fn execute_jump(&self, target: BasicBlockId) -> Result<ControlFlow, VMError> {
        Ok(ControlFlow::Jump(target))
    }

    pub(super) fn execute_branch(&self, condition: ValueId, then_bb: BasicBlockId, else_bb: BasicBlockId) -> Result<ControlFlow, VMError> {
        let cond_val = self.get_value(condition)?;
        let should_branch = match &cond_val {
            VMValue::Bool(b) => *b,
            VMValue::Void => false,
            VMValue::Integer(i) => *i != 0,
            VMValue::BoxRef(b) => {
                if let Some(bool_box) = b.as_any().downcast_ref::<BoolBox>() {
                    bool_box.value
                } else if b.as_any().downcast_ref::<VoidBox>().is_some() {
                    false
                } else {
                    return Err(VMError::TypeError(
                        format!("Branch condition must be bool, void, or integer, got BoxRef({})", b.type_name())
                    ));
                }
            }
            _ => return Err(VMError::TypeError(
                format!("Branch condition must be bool, void, or integer, got {:?}", cond_val)
            )),
        };
        
        Ok(ControlFlow::Jump(if should_branch { then_bb } else { else_bb }))
    }

    pub(super) fn execute_return(&self, value: Option<ValueId>) -> Result<ControlFlow, VMError> {
        if let Some(val_id) = value {
            let return_val = self.get_value(val_id)?;
            Ok(ControlFlow::Return(return_val))
        } else {
            Ok(ControlFlow::Return(VMValue::Void))
        }
    }

    /// Execute TypeOp instruction
    pub(super) fn execute_typeop(&mut self, dst: ValueId, op: &TypeOpKind, value: ValueId, ty: &MirType) -> Result<ControlFlow, VMError> {
        let val = self.get_value(value)?;
        
        match op {
            TypeOpKind::Check => {
                let is_type = match (&val, ty) {
                    (VMValue::Integer(_), MirType::Integer) => true,
                    (VMValue::Float(_), MirType::Float) => true,
                    (VMValue::Bool(_), MirType::Bool) => true,
                    (VMValue::String(_), MirType::String) => true,
                    (VMValue::Void, MirType::Void) => true,
                    (VMValue::BoxRef(arc_box), MirType::Box(box_name)) => {
                        arc_box.type_name() == box_name
                    }
                    _ => false,
                };
                self.set_value(dst, VMValue::Bool(is_type));
                Ok(ControlFlow::Continue)
            }
            TypeOpKind::Cast => {
                let result = match (&val, ty) {
                    // Integer to Float
                    (VMValue::Integer(i), MirType::Float) => VMValue::Float(*i as f64),
                    // Float to Integer
                    (VMValue::Float(f), MirType::Integer) => VMValue::Integer(*f as i64),
                    // Identity casts
                    (VMValue::Integer(_), MirType::Integer) => val.clone(),
                    (VMValue::Float(_), MirType::Float) => val.clone(),
                    (VMValue::Bool(_), MirType::Bool) => val.clone(),
                    (VMValue::String(_), MirType::String) => val.clone(),
                    // BoxRef identity cast
                    (VMValue::BoxRef(arc_box), MirType::Box(box_name)) if arc_box.type_name() == box_name => {
                        val.clone()
                    }
                    // Invalid cast
                    _ => {
                        return Err(VMError::TypeError(
                            format!("Cannot cast {:?} to {:?}", val, ty)
                        ));
                    }
                };
                self.set_value(dst, result);
                Ok(ControlFlow::Continue)
            }
        }
    }

    /// Execute Phi instruction
    pub(super) fn execute_phi(&mut self, dst: ValueId, inputs: &[(BasicBlockId, ValueId)]) -> Result<ControlFlow, VMError> {
        // For now, just use the first input since we don't track previous BB in this refactored version
        // TODO: Track previous basic block for proper phi node resolution
        if let Some((_, val_id)) = inputs.first() {
            let value = self.get_value(*val_id)?;
            self.set_value(dst, value);
            Ok(ControlFlow::Continue)
        } else {
            Err(VMError::InvalidInstruction("Phi node has no inputs".to_string()))
        }
    }

    /// Execute Load/Store instructions
    pub(super) fn execute_load(&mut self, dst: ValueId, ptr: ValueId) -> Result<ControlFlow, VMError> {
        let loaded_value = self.get_value(ptr)?;
        self.set_value(dst, loaded_value);
        Ok(ControlFlow::Continue)
    }

    pub(super) fn execute_store(&mut self, value: ValueId, ptr: ValueId) -> Result<ControlFlow, VMError> {
        let val = self.get_value(value)?;
        self.set_value(ptr, val);
        Ok(ControlFlow::Continue)
    }

    /// Execute Copy instruction
    pub(super) fn execute_copy(&mut self, dst: ValueId, src: ValueId) -> Result<ControlFlow, VMError> {
        let value = self.get_value(src)?;
        let cloned = match &value {
            VMValue::BoxRef(arc_box) => {
                // Use clone_or_share to handle cloning properly
                let cloned_box = arc_box.clone_or_share();
                VMValue::BoxRef(Arc::from(cloned_box))
            }
            other => other.clone(),
        };
        self.set_value(dst, cloned);
        Ok(ControlFlow::Continue)
    }

    /// Execute Call instruction
    pub(super) fn execute_call(&mut self, dst: Option<ValueId>, func: ValueId, args: &[ValueId]) -> Result<ControlFlow, VMError> {
        // Get the function name from the ValueId
        let func_name = match self.get_value(func)? {
            VMValue::String(s) => s,
            _ => return Err(VMError::TypeError("Function name must be a string".to_string())),
        };
        
        let arg_values: Vec<VMValue> = args.iter()
            .map(|arg| self.get_value(*arg))
            .collect::<Result<Vec<_>, _>>()?;
        
        let result = self.call_function_by_name(&func_name, arg_values)?;
        
        if let Some(dst_id) = dst {
            self.set_value(dst_id, result);
        }
        
        Ok(ControlFlow::Continue)
    }

    /// Execute NewBox instruction
    pub(super) fn execute_newbox(&mut self, dst: ValueId, box_type: &str, args: &[ValueId]) -> Result<ControlFlow, VMError> {
        // Convert args to NyashBox values
        let arg_values: Vec<Box<dyn NyashBox>> = args.iter()
            .map(|arg| {
                let val = self.get_value(*arg)?;
                Ok(val.to_nyash_box())
            })
            .collect::<Result<Vec<_>, VMError>>()?;

        // Create new box using runtime's registry
        let new_box = {
            let registry = self.runtime.box_registry.lock()
                .map_err(|_| VMError::InvalidInstruction("Failed to lock box registry".to_string()))?;
            registry.create_box(box_type, &arg_values)
                .map_err(|e| VMError::InvalidInstruction(format!("Failed to create {}: {}", box_type, e)))?
        };
        
        self.set_value(dst, VMValue::BoxRef(Arc::from(new_box)));
        Ok(ControlFlow::Continue)
    }

    /// Execute ArrayGet instruction
    pub(super) fn execute_array_get(&mut self, dst: ValueId, array: ValueId, index: ValueId) -> Result<ControlFlow, VMError> {
        let array_val = self.get_value(array)?;
        let index_val = self.get_value(index)?;
        
        if let VMValue::BoxRef(array_box) = &array_val {
            if let Some(array) = array_box.as_any().downcast_ref::<ArrayBox>() {
                // ArrayBox expects Box<dyn NyashBox> for index
                let index_box = index_val.to_nyash_box();
                let result = array.get(index_box);
                self.set_value(dst, VMValue::BoxRef(Arc::from(result)));
                Ok(ControlFlow::Continue)
            } else {
                Err(VMError::TypeError("ArrayGet requires an ArrayBox".to_string()))
            }
        } else {
            Err(VMError::TypeError("ArrayGet requires array and integer index".to_string()))
        }
    }

    /// Execute ArraySet instruction
    pub(super) fn execute_array_set(&mut self, array: ValueId, index: ValueId, value: ValueId) -> Result<ControlFlow, VMError> {
        let array_val = self.get_value(array)?;
        let index_val = self.get_value(index)?;
        let value_val = self.get_value(value)?;
        
        if let VMValue::BoxRef(array_box) = &array_val {
            if let Some(array) = array_box.as_any().downcast_ref::<ArrayBox>() {
                // ArrayBox expects Box<dyn NyashBox> for index
                let index_box = index_val.to_nyash_box();
                let box_value = value_val.to_nyash_box();
                array.set(index_box, box_value);
                Ok(ControlFlow::Continue)
            } else {
                Err(VMError::TypeError("ArraySet requires an ArrayBox".to_string()))
            }
        } else {
            Err(VMError::TypeError("ArraySet requires array and integer index".to_string()))
        }
    }

    /// Execute RefNew instruction
    pub(super) fn execute_ref_new(&mut self, dst: ValueId, box_val: ValueId) -> Result<ControlFlow, VMError> {
        // For now, a reference is just the same as the box value
        // In a real implementation, this would create a proper reference
        let box_value = self.get_value(box_val)?;
        self.set_value(dst, box_value);
        Ok(ControlFlow::Continue)
    }

    /// Execute RefGet instruction
    pub(super) fn execute_ref_get(&mut self, dst: ValueId, reference: ValueId, field: &str) -> Result<ControlFlow, VMError> {
        // Visibility check (if class known and visibility declared). Skip for internal refs.
        let is_internal = self.object_internal.contains(&reference);
        if !is_internal {
            if let Some(class_name) = self.object_class.get(&reference) {
                if let Ok(decls) = self.runtime.box_declarations.read() {
                    if let Some(decl) = decls.get(class_name) {
                        let has_vis = !decl.public_fields.is_empty() || !decl.private_fields.is_empty();
                        if has_vis && !decl.public_fields.iter().any(|f| f == field) {
                            return Err(VMError::TypeError(format!("Field '{}' is private in {}", field, class_name)));
                        }
                    }
                }
            }
        }
        // Get field value from object
        let field_value = if let Some(fields) = self.object_fields.get(&reference) {
            if let Some(value) = fields.get(field) {
                value.clone()
            } else {
                // Field not set yet, return default
                VMValue::Integer(0)
            }
        } else {
            // Object has no fields yet, return default
            VMValue::Integer(0)
        };
        
        self.set_value(dst, field_value);
        Ok(ControlFlow::Continue)
    }

    /// Execute RefSet instruction
    pub(super) fn execute_ref_set(&mut self, reference: ValueId, field: &str, value: ValueId) -> Result<ControlFlow, VMError> {
        // Get the value to set
        let new_value = self.get_value(value)?;
        // Visibility check (Skip for internal refs; otherwise enforce public)
        let is_internal = self.object_internal.contains(&reference);
        if !is_internal {
            if let Some(class_name) = self.object_class.get(&reference) {
                if let Ok(decls) = self.runtime.box_declarations.read() {
                    if let Some(decl) = decls.get(class_name) {
                        let has_vis = !decl.public_fields.is_empty() || !decl.private_fields.is_empty();
                        if has_vis && !decl.public_fields.iter().any(|f| f == field) {
                            return Err(VMError::TypeError(format!("Field '{}' is private in {}", field, class_name)));
                        }
                    }
                }
            }
        }
        
        // Ensure object has field storage
        if !self.object_fields.contains_key(&reference) {
            self.object_fields.insert(reference, std::collections::HashMap::new());
        }
        
        // Set the field
        if let Some(fields) = self.object_fields.get_mut(&reference) {
            fields.insert(field.to_string(), new_value);
        }
        
        Ok(ControlFlow::Continue)
    }

    /// Execute WeakNew instruction
    pub(super) fn execute_weak_new(&mut self, dst: ValueId, box_val: ValueId) -> Result<ControlFlow, VMError> {
        // For now, a weak reference is just a copy of the value
        // In a real implementation, this would create a proper weak reference
        let box_value = self.get_value(box_val)?;
        self.set_value(dst, box_value);
        Ok(ControlFlow::Continue)
    }

    /// Execute WeakLoad instruction
    pub(super) fn execute_weak_load(&mut self, dst: ValueId, weak_ref: ValueId) -> Result<ControlFlow, VMError> {
        // For now, loading from weak ref is the same as getting the value
        // In a real implementation, this would check if the weak ref is still valid
        let weak_value = self.get_value(weak_ref)?;
        self.set_value(dst, weak_value);
        Ok(ControlFlow::Continue)
    }

    /// Execute BarrierRead instruction
    pub(super) fn execute_barrier_read(&mut self, dst: ValueId, value: ValueId) -> Result<ControlFlow, VMError> {
        // Memory barrier read is currently a simple value copy
        // In a real implementation, this would ensure memory ordering
        let val = self.get_value(value)?;
        self.set_value(dst, val);
        Ok(ControlFlow::Continue)
    }

    /// Execute BarrierWrite instruction
    pub(super) fn execute_barrier_write(&mut self, _value: ValueId) -> Result<ControlFlow, VMError> {
        // Memory barrier write is a no-op for now
        // In a real implementation, this would ensure memory ordering
        Ok(ControlFlow::Continue)
    }

    /// Execute Throw instruction
    pub(super) fn execute_throw(&mut self, exception: ValueId) -> Result<ControlFlow, VMError> {
        let exc_value = self.get_value(exception)?;
        Err(VMError::InvalidInstruction(format!("Exception thrown: {:?}", exc_value)))
    }

    /// Execute Catch instruction
    pub(super) fn execute_catch(&mut self, exception_value: ValueId) -> Result<ControlFlow, VMError> {
        // For now, catch is a no-op
        // In a real implementation, this would handle exception catching
        self.set_value(exception_value, VMValue::Void);
        Ok(ControlFlow::Continue)
    }

    /// Execute Await instruction
    pub(super) fn execute_await(&mut self, dst: ValueId, future: ValueId) -> Result<ControlFlow, VMError> {
        let future_val = self.get_value(future)?;
        
        if let VMValue::Future(ref future_box) = future_val {
            // This blocks until the future is ready
            let result = future_box.get();
            // Convert NyashBox back to VMValue
            let vm_value = VMValue::from_nyash_box(result);
            self.set_value(dst, vm_value);
            Ok(ControlFlow::Continue)
        } else {
            Err(VMError::TypeError(format!("Expected Future, got {:?}", future_val)))
        }
    }

    /// Execute ExternCall instruction
    pub(super) fn execute_extern_call(&mut self, dst: Option<ValueId>, iface_name: &str, method_name: &str, args: &[ValueId]) -> Result<ControlFlow, VMError> {
        
        // Evaluate arguments as NyashBox for loader
        let mut nyash_args: Vec<Box<dyn NyashBox>> = Vec::new();
        for arg_id in args {
            let arg_value = self.get_value(*arg_id)?;
            nyash_args.push(arg_value.to_nyash_box());
        }
        
        // Route through plugin loader v2 (also handles env.* stubs)
        let loader = crate::runtime::get_global_loader_v2();
        let loader = loader.read().map_err(|_| VMError::InvalidInstruction("Plugin loader lock poisoned".into()))?;
        match loader.extern_call(iface_name, method_name, &nyash_args) {
            Ok(Some(result_box)) => {
                if let Some(dst_id) = dst {
                    self.set_value(dst_id, VMValue::from_nyash_box(result_box));
                }
            }
            Ok(None) => {
                if let Some(dst_id) = dst {
                    self.set_value(dst_id, VMValue::Void);
                }
            }
            Err(_) => {
                return Err(VMError::InvalidInstruction(format!("ExternCall failed: {}.{}", iface_name, method_name)));
            }
        }
        Ok(ControlFlow::Continue)
    }

    /// Execute BoxCall instruction
    pub(super) fn execute_boxcall(&mut self, dst: Option<ValueId>, box_val: ValueId, method: &str, args: &[ValueId]) -> Result<ControlFlow, VMError> {
        let recv = self.get_value(box_val)?;
        
        // Debug logging if enabled
        let debug_boxcall = std::env::var("NYASH_VM_DEBUG_BOXCALL").is_ok();
        
        // Convert args to NyashBox
        let nyash_args: Vec<Box<dyn NyashBox>> = args.iter()
            .map(|arg| {
                let val = self.get_value(*arg)?;
                Ok(val.to_nyash_box())
            })
            .collect::<Result<Vec<_>, VMError>>()?;
        
        if debug_boxcall {
            self.debug_log_boxcall(&recv, method, &nyash_args, "START", None);
        }
        
        // Call the method based on receiver type
        let result = match &recv {
            VMValue::BoxRef(arc_box) => {
                // Direct box method call
                if debug_boxcall {
                    eprintln!("[BoxCall] Taking BoxRef path for method '{}'", method);
                }
                
                let cloned_box = arc_box.share_box();
                self.call_box_method(cloned_box, method, nyash_args)?
            }
            _ => {
                // Convert primitive to box and call
                if debug_boxcall {
                    eprintln!("[BoxCall] Converting primitive to box for method '{}'", method);
                }
                
                let box_value = recv.to_nyash_box();
                self.call_box_method(box_value, method, nyash_args)?
            }
        };
        
        // Convert result back to VMValue
        let result_val = VMValue::from_nyash_box(result);
        
        if debug_boxcall {
            self.debug_log_boxcall(&recv, method, &[], "END", Some(&result_val));
        }
        
        if let Some(dst_id) = dst {
            self.set_value(dst_id, result_val);
        }
        
        Ok(ControlFlow::Continue)
    }
}