//! Phase 27-shortterm S-4: JoinIR → Rust VM Bridge
//!
//! 目的: JoinIR（正規化された IR）を Rust VM で実行するブリッジ層
//!
//! ## Architecture
//! ```text
//! JoinIR (normalized) → MirModule → Rust VM → Result
//!       ↑                 ↑          ↑
//!   PHI bugs         VM input    Execution
//!   eliminated         format    (GC, plugins)
//! ```
//!
//! ## Design Principles
//! - JoinIR の正規化構造を保持したまま VM に渡す
//! - マッピングだけで済ませる（JoinIR でやった正規化は消えない）
//! - VM の機能（GC、プラグイン、エラーハンドリング）を活用
//!
//! ## Minimal Instruction Set (S-4.3)
//! - **Compute**: Const, BinOp, Compare
//! - **BoxCall**: StringBox メソッド呼び出し
//! - **Call/Jump/Ret**: 制御フロー
//!
//! Phase 27-shortterm scope: skip_ws で green 化できれば成功

use crate::backend::{MirInterpreter, VMError, VMValue};
use crate::config::env::joinir_vm_bridge_debug;
use crate::mir::join_ir::{
    BinOpKind, CompareOp, ConstValue, JoinFuncId, JoinInst, JoinModule, MirLikeInst,
};
use crate::mir::join_ir_ops::JoinValue;
use crate::ast::Span;
use crate::mir::{
    BasicBlockId, BinaryOp, CompareOp as MirCompareOp, ConstValue as MirConstValue, EffectMask,
    FunctionSignature, MirFunction, MirInstruction, MirModule, MirType, ValueId,
};

/// 条件付きデバッグ出力マクロ（NYASH_JOINIR_VM_BRIDGE_DEBUG=1 で有効）
macro_rules! debug_log {
    ($($arg:tt)*) => {
        if joinir_vm_bridge_debug() {
            eprintln!($($arg)*);
        }
    };
}

/// Phase 27-shortterm S-4 エラー型
#[derive(Debug, Clone)]
pub struct JoinIrVmBridgeError {
    pub message: String,
}

impl JoinIrVmBridgeError {
    pub fn new(msg: impl Into<String>) -> Self {
        Self {
            message: msg.into(),
        }
    }
}

impl From<VMError> for JoinIrVmBridgeError {
    fn from(err: VMError) -> Self {
        JoinIrVmBridgeError::new(format!("VM error: {:?}", err))
    }
}

/// ブロックを確定する（instructions + spans + terminator を設定）
fn finalize_block(
    mir_func: &mut MirFunction,
    block_id: BasicBlockId,
    instructions: Vec<MirInstruction>,
    terminator: MirInstruction,
) {
    if let Some(block) = mir_func.blocks.get_mut(&block_id) {
        let inst_count = instructions.len();
        block.instructions = instructions;
        block.instruction_spans = vec![Span::unknown(); inst_count];
        block.terminator = Some(terminator);
    }
}

/// JoinFuncId から MIR 用の関数名を生成
fn join_func_name(id: JoinFuncId) -> String {
    format!("join_func_{}", id.0)
}

/// Phase 27-shortterm S-4.3: JoinIR → VM 実行のエントリーポイント
///
/// ## Arguments
/// - `join_module`: JoinIR モジュール（正規化済み）
/// - `entry_func`: エントリーポイント関数ID
/// - `args`: 初期引数（JoinValue 形式）
///
/// ## Returns
/// - `Ok(JoinValue)`: 実行結果
/// - `Err(JoinIrVmBridgeError)`: 変換エラーまたは実行エラー
///
/// ## Example
/// ```ignore
/// let join_module = lower_skip_ws_to_joinir(&mir_module)?;
/// let result = run_joinir_via_vm(
///     &join_module,
///     JoinFuncId::new(0),
///     &[JoinValue::Str("  hello".to_string()), JoinValue::Int(7)]
/// )?;
/// assert_eq!(result, JoinValue::Int(2));
/// ```
pub fn run_joinir_via_vm(
    join_module: &JoinModule,
    entry_func: JoinFuncId,
    args: &[JoinValue],
) -> Result<JoinValue, JoinIrVmBridgeError> {
    debug_log!("[joinir_vm_bridge] Phase 27-shortterm S-4.3");
    debug_log!("[joinir_vm_bridge] Converting JoinIR to MIR for VM execution");

    // Step 1: JoinIR → MIR 変換
    let mir_module = convert_joinir_to_mir(join_module)?;

    debug_log!(
        "[joinir_vm_bridge] Converted {} JoinIR functions to MIR",
        join_module.functions.len()
    );

    // Step 2: VM 実行
    let mut vm = MirInterpreter::new();

    debug_log!(
        "[joinir_vm_bridge] Executing via VM with {} arguments",
        args.len()
    );

    // Convert JoinValue → VMValue (BoxRef 含む)
    let vm_args: Vec<VMValue> = args.iter().cloned().map(|v| v.into_vm_value()).collect();

    let entry_name = join_func_name(entry_func);
    let result = vm.execute_function_with_args(&mir_module, &entry_name, &vm_args)?;

    // Step 3: VMValue → JoinValue 変換
    let join_result = JoinValue::from_vm_value(&result)
        .map_err(|e| JoinIrVmBridgeError::new(format!("Result conversion error: {}", e.message)))?;

    debug_log!("[joinir_vm_bridge] Execution succeeded: {:?}", join_result);

    Ok(join_result)
}

/// Phase 30.x: JoinIR → MIR 変換器
///
/// Phase 32 L-2.2 Step-3: テストから呼び出し可能に `pub(crate)` 化
pub(crate) fn convert_joinir_to_mir(join_module: &JoinModule) -> Result<MirModule, JoinIrVmBridgeError> {
    let mut mir_module = MirModule::new("joinir_bridge".to_string());

    // Convert all JoinIR functions to MIR (entry function becomes "skip" or similar)
    for (func_id, join_func) in &join_module.functions {
        debug_log!(
            "[joinir_vm_bridge] Converting JoinFunction {} ({})",
            func_id.0, join_func.name
        );

        let mir_func = convert_join_function_to_mir(join_func)?;

        // Use actual function name (not "main") since we'll create a wrapper
        mir_module.functions.insert(join_func_name(*func_id), mir_func);
    }

    Ok(mir_module)
}

/// JoinFunction → MirFunction 変換
fn convert_join_function_to_mir(
    join_func: &crate::mir::join_ir::JoinFunction,
) -> Result<MirFunction, JoinIrVmBridgeError> {
    // Phase 27-shortterm S-4.4: skip_ws パターン対応版
    // - Call (tail call): MIR Call に変換
    // - Jump (conditional exit): Branch + Return に変換
    let entry_block = BasicBlockId(0);

    // Create minimal FunctionSignature for JoinIR function
    // Phase 27-shortterm: すべて MirType::Unknown として扱う（型情報は JoinIR に無いため）
    let param_types = join_func
        .params
        .iter()
        .map(|_| MirType::Unknown)
        .collect::<Vec<_>>();

    let signature = FunctionSignature {
        name: join_func.name.clone(),
        params: param_types,
        return_type: MirType::Unknown,
        effects: EffectMask::PURE,
    };

    let mut mir_func = MirFunction::new(signature, entry_block);

    // Phase 30.x: Set parameter ValueIds from JoinIR function
    // JoinIR's VarId is an alias for ValueId, so direct copy works
    mir_func.params = join_func.params.clone();

    // Phase 27-shortterm S-4.4: Multi-block conversion for Jump instructions
    // Strategy:
    // - Accumulate Compute instructions in current block
    // - On Jump: emit Branch + create exit block with Return
    // - On Call: emit Call in current block
    let mut current_block_id = entry_block;
    let mut current_instructions = Vec::new();
    let mut next_block_id = 1u32; // for creating new blocks

    for join_inst in &join_func.body {
        match join_inst {
            JoinInst::Compute(mir_like) => {
                let mir_inst = convert_mir_like_inst(mir_like)?;
                current_instructions.push(mir_inst);
            }
            JoinInst::MethodCall { dst, receiver, method, args } => {
                // Phase 34-6: MethodCall → MIR BoxCall 変換
                // receiver.method(args...) を BoxCall(receiver, method, args) に変換
                let mir_inst = MirInstruction::BoxCall {
                    dst: Some(*dst),
                    box_val: *receiver,
                    method: method.clone(),
                    method_id: None,
                    args: args.clone(),
                    effects: EffectMask::PURE,
                };
                current_instructions.push(mir_inst);
            }
            JoinInst::Call {
                func,
                args,
                dst,
                k_next,
            } => {
                // Phase 30.x: Support both tail calls and non-tail calls
                // - dst=None, k_next=None: Tail call → call + return
                // - dst=Some(id), k_next=None: Non-tail call → call + store + continue
                // - k_next=Some: Not yet supported

                if k_next.is_some() {
                    let call_target_name = join_func_name(*func);
                    return Err(JoinIrVmBridgeError::new(format!(
                        "Call with k_next is not yet supported\n\
\n\
Current function: {}\n\
Call target: {} (JoinFuncId: {:?})\n\
Arguments: {} args\n\
k_next: {:?}\n\
\n\
💡 Fix: Change `k_next: Some(...)` to `k_next: None`\n\
💡 Note: Phase 31 and Phase 34 both use k_next=None (bridge limitation)\n\
\n\
Example:\n\
Call {{\n\
    func: loop_step_id,\n\
    args: vec![i_next, acc_next, n],\n\
    k_next: None,  // ⚠️ Must be None\n\
    dst: Some(result),\n\
}}",
                        join_func.name,
                        call_target_name,
                        func,
                        args.len(),
                        k_next,
                    )));
                }

                // Convert JoinFuncId to function name
                let func_name = join_func_name(*func);

                // Create temporary ValueId for function name
                let func_name_id = ValueId(99990 + next_block_id);
                next_block_id += 1;

                // Add Const instruction for function name
                current_instructions.push(MirInstruction::Const {
                    dst: func_name_id,
                    value: MirConstValue::String(func_name),
                });

                match dst {
                    Some(result_dst) => {
                        // Non-tail call: store result in dst and continue
                        current_instructions.push(MirInstruction::Call {
                            dst: Some(*result_dst),
                            func: func_name_id,
                            callee: None,
                            args: args.clone(),
                            effects: EffectMask::PURE,
                        });
                        // Continue to next instruction (no block termination)
                    }
                    None => {
                        // Tail call: call + return result
                        let call_result_id = ValueId(99991);
                        current_instructions.push(MirInstruction::Call {
                            dst: Some(call_result_id),
                            func: func_name_id,
                            callee: None,
                            args: args.clone(),
                            effects: EffectMask::PURE,
                        });

                        // Return the result of the tail call
                        let terminator = MirInstruction::Return { value: Some(call_result_id) };
                        finalize_block(&mut mir_func, current_block_id, current_instructions, terminator);
                        current_instructions = Vec::new();
                    }
                }
            }
            JoinInst::Jump { cont, args, cond } => {
                // Phase 27-shortterm S-4.4-A: Jump with condition → Branch + Return
                // Jump represents an exit continuation (k_exit) in skip_ws pattern

                debug_log!(
                    "[joinir_vm_bridge] Converting Jump to cont={:?}, args={:?}, cond={:?}",
                    cont, args, cond
                );

                match cond {
                    Some(cond_var) => {
                        // Conditional jump: Branch to exit block
                        let exit_block_id = BasicBlockId(next_block_id);
                        next_block_id += 1;
                        let continue_block_id = BasicBlockId(next_block_id);
                        next_block_id += 1;

                        // Phase 30.x: Branch terminator (separate from instructions)
                        let branch_terminator = MirInstruction::Branch {
                            condition: *cond_var,
                            then_bb: exit_block_id,
                            else_bb: continue_block_id,
                        };

                        // Finalize current block with Branch terminator
                        finalize_block(&mut mir_func, current_block_id, current_instructions, branch_terminator);

                        // Create exit block with Return terminator
                        let exit_value = args.first().copied();
                        let mut exit_block = crate::mir::BasicBlock::new(exit_block_id);
                        exit_block.terminator = Some(MirInstruction::Return { value: exit_value });
                        mir_func.blocks.insert(exit_block_id, exit_block);

                        // Create continue block (will be populated by subsequent instructions)
                        let continue_block = crate::mir::BasicBlock::new(continue_block_id);
                        mir_func.blocks.insert(continue_block_id, continue_block);

                        // Continue in the next block
                        current_block_id = continue_block_id;
                        current_instructions = Vec::new();
                    }
                    None => {
                        // Unconditional jump: direct Return terminator
                        let exit_value = args.first().copied();
                        let return_terminator = MirInstruction::Return { value: exit_value };

                        // Finalize current block with Return terminator
                        finalize_block(&mut mir_func, current_block_id, current_instructions, return_terminator);

                        // No continuation after unconditional return
                        current_instructions = Vec::new();
                    }
                }
            }
            // Phase 33: Select instruction conversion to MIR
            JoinInst::Select { dst, cond, then_val, else_val } => {
                // Phase 33-2: Select を MIR の if/phi に変換
                // 最小実装: cond/then/else/merge の 4 ブロック構造

                debug_log!(
                    "[joinir_vm_bridge] Converting Select: dst={:?}, cond={:?}, then={:?}, else={:?}",
                    dst, cond, then_val, else_val
                );

                // 1. cond ブロック（現在のブロック）
                let cond_block = current_block_id;

                // 2. then ブロック作成
                let then_block = BasicBlockId(next_block_id);
                next_block_id += 1;

                // 3. else ブロック作成
                let else_block = BasicBlockId(next_block_id);
                next_block_id += 1;

                // 4. merge ブロック作成
                let merge_block = BasicBlockId(next_block_id);
                next_block_id += 1;

                // 5. cond ブロックで分岐
                let branch_terminator = MirInstruction::Branch {
                    condition: *cond,
                    then_bb: then_block,
                    else_bb: else_block,
                };
                finalize_block(&mut mir_func, cond_block, current_instructions, branch_terminator);

                // 6. then ブロック: dst = then_val; jump merge
                let mut then_block_obj = crate::mir::BasicBlock::new(then_block);
                then_block_obj.instructions.push(MirInstruction::Copy {
                    dst: *dst,
                    src: *then_val,
                });
                then_block_obj.instruction_spans.push(Span::unknown());
                then_block_obj.terminator = Some(MirInstruction::Jump { target: merge_block });
                mir_func.blocks.insert(then_block, then_block_obj);

                // 7. else ブロック: dst = else_val; jump merge
                let mut else_block_obj = crate::mir::BasicBlock::new(else_block);
                else_block_obj.instructions.push(MirInstruction::Copy {
                    dst: *dst,
                    src: *else_val,
                });
                else_block_obj.instruction_spans.push(Span::unknown());
                else_block_obj.terminator = Some(MirInstruction::Jump { target: merge_block });
                mir_func.blocks.insert(else_block, else_block_obj);

                // 8. merge ブロック作成（空）
                let merge_block_obj = crate::mir::BasicBlock::new(merge_block);
                mir_func.blocks.insert(merge_block, merge_block_obj);

                // 9. merge ブロックに移動
                current_block_id = merge_block;
                current_instructions = Vec::new();
            }
            // Phase 33-6: IfMerge instruction conversion to MIR
            JoinInst::IfMerge { cond, merges, k_next } => {
                // Phase 33-6: IfMerge を MIR の if/phi に変換
                // Select と同じ 4 ブロック構造だが、複数の Copy を生成

                // Phase 33-6 最小実装: k_next は None のみサポート
                if k_next.is_some() {
                    return Err(JoinIrVmBridgeError::new(
                        "IfMerge: k_next continuation is not yet supported (Phase 33-6 minimal)".to_string(),
                    ));
                }

                debug_log!(
                    "[joinir_vm_bridge] Converting IfMerge: cond={:?}, merges.len()={}",
                    cond, merges.len()
                );

                // 1. cond ブロック（現在のブロック）
                let cond_block = current_block_id;

                // 2. then ブロック作成
                let then_block = BasicBlockId(next_block_id);
                next_block_id += 1;

                // 3. else ブロック作成
                let else_block = BasicBlockId(next_block_id);
                next_block_id += 1;

                // 4. merge ブロック作成
                let merge_block = BasicBlockId(next_block_id);
                next_block_id += 1;

                // 5. cond ブロックで分岐
                let branch_terminator = MirInstruction::Branch {
                    condition: *cond,
                    then_bb: then_block,
                    else_bb: else_block,
                };
                finalize_block(&mut mir_func, cond_block, current_instructions, branch_terminator);

                // 6. then ブロック: 各 merge について dst = then_val; jump merge
                let mut then_block_obj = crate::mir::BasicBlock::new(then_block);
                for merge in merges {
                    then_block_obj.instructions.push(MirInstruction::Copy {
                        dst: merge.dst,
                        src: merge.then_val,
                    });
                    then_block_obj.instruction_spans.push(Span::unknown());
                }
                then_block_obj.terminator = Some(MirInstruction::Jump { target: merge_block });
                mir_func.blocks.insert(then_block, then_block_obj);

                // 7. else ブロック: 各 merge について dst = else_val; jump merge
                let mut else_block_obj = crate::mir::BasicBlock::new(else_block);
                for merge in merges {
                    else_block_obj.instructions.push(MirInstruction::Copy {
                        dst: merge.dst,
                        src: merge.else_val,
                    });
                    else_block_obj.instruction_spans.push(Span::unknown());
                }
                else_block_obj.terminator = Some(MirInstruction::Jump { target: merge_block });
                mir_func.blocks.insert(else_block, else_block_obj);

                // 8. merge ブロック作成（空）
                let merge_block_obj = crate::mir::BasicBlock::new(merge_block);
                mir_func.blocks.insert(merge_block, merge_block_obj);

                // 9. merge ブロックに移動
                current_block_id = merge_block;
                current_instructions = Vec::new();
            }
            JoinInst::Ret { value } => {
                // Phase 30.x: Return terminator (separate from instructions)
                let return_terminator = MirInstruction::Return { value: *value };

                // Finalize current block with Return terminator
                finalize_block(&mut mir_func, current_block_id, current_instructions, return_terminator);

                current_instructions = Vec::new();
            }
        }
    }

    // Finalize any remaining instructions in the last block
    if !current_instructions.is_empty() {
        debug_log!(
            "[joinir_vm_bridge] Final block {:?} has {} remaining instructions",
            current_block_id,
            current_instructions.len()
        );
        if let Some(block) = mir_func.blocks.get_mut(&current_block_id) {
            // Phase 30.x: VM requires instruction_spans to match instructions length
            let inst_count = current_instructions.len();
            block.instructions = current_instructions;
            block.instruction_spans = vec![Span::unknown(); inst_count];
        }
    }

    // Debug: print all blocks and their instruction counts + terminators
    debug_log!(
        "[joinir_vm_bridge] Function '{}' has {} blocks:",
        mir_func.signature.name,
        mir_func.blocks.len()
    );
    for (block_id, block) in &mir_func.blocks {
        debug_log!(
            "  Block {:?}: {} instructions, terminator={:?}",
            block_id,
            block.instructions.len(),
            block.terminator
        );
    }

    Ok(mir_func)
}

/// MirLikeInst → MirInstruction 変換
fn convert_mir_like_inst(mir_like: &MirLikeInst) -> Result<MirInstruction, JoinIrVmBridgeError> {
    match mir_like {
        MirLikeInst::Const { dst, value } => {
            let mir_const = match value {
                ConstValue::Integer(i) => MirConstValue::Integer(*i),
                ConstValue::Bool(b) => MirConstValue::Bool(*b),
                ConstValue::String(s) => MirConstValue::String(s.clone()),
                ConstValue::Null => MirConstValue::Null,
            };
            Ok(MirInstruction::Const {
                dst: *dst,
                value: mir_const,
            })
        }
        MirLikeInst::BinOp { dst, op, lhs, rhs } => {
            let mir_op = match op {
                BinOpKind::Add => BinaryOp::Add,
                BinOpKind::Sub => BinaryOp::Sub,
                BinOpKind::Mul => BinaryOp::Mul,
                BinOpKind::Div => BinaryOp::Div,
                BinOpKind::Or => BinaryOp::Or,
                BinOpKind::And => BinaryOp::And,
            };
            Ok(MirInstruction::BinOp {
                dst: *dst,
                op: mir_op,
                lhs: *lhs,
                rhs: *rhs,
            })
        }
        MirLikeInst::Compare { dst, op, lhs, rhs } => {
            let mir_cmp = match op {
                CompareOp::Lt => MirCompareOp::Lt,
                CompareOp::Le => MirCompareOp::Le,
                CompareOp::Gt => MirCompareOp::Gt,
                CompareOp::Ge => MirCompareOp::Ge,
                CompareOp::Eq => MirCompareOp::Eq,
                CompareOp::Ne => MirCompareOp::Ne,
            };
            Ok(MirInstruction::Compare {
                dst: *dst,
                op: mir_cmp,
                lhs: *lhs,
                rhs: *rhs,
            })
        }
        MirLikeInst::BoxCall {
            dst,
            box_name,
            method,
            args,
        } => {
            // Phase 27-shortterm S-4.3: BoxCall → MIR BoxCall
            // box_name は JoinIR で保持しているが、MIR BoxCall には receiver ValueId のみ
            // 暫定: args[0] を receiver として扱う
            if args.is_empty() {
                return Err(JoinIrVmBridgeError::new(format!(
                    "BoxCall requires at least one argument (receiver), got: box_name={}, method={}",
                    box_name, method
                )));
            }

            let receiver = args[0];
            let method_args = args[1..].to_vec();

            Ok(MirInstruction::BoxCall {
                dst: *dst,
                box_val: receiver,
                method: method.clone(),
                method_id: None, // Phase 27-shortterm: no method ID resolution
                args: method_args,
                effects: EffectMask::PURE, // Phase 27-shortterm: assume pure
            })
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_convert_const_inst() {
        let join_const = MirLikeInst::Const {
            dst: ValueId(10),
            value: ConstValue::Integer(42),
        };

        let mir_inst = convert_mir_like_inst(&join_const).unwrap();

        match mir_inst {
            MirInstruction::Const { dst, value } => {
                assert_eq!(dst, ValueId(10));
                assert!(matches!(value, MirConstValue::Integer(42)));
            }
            _ => panic!("Expected Const instruction"),
        }
    }

    #[test]
    fn test_convert_binop_inst() {
        let join_binop = MirLikeInst::BinOp {
            dst: ValueId(20),
            op: BinOpKind::Add,
            lhs: ValueId(10),
            rhs: ValueId(11),
        };

        let mir_inst = convert_mir_like_inst(&join_binop).unwrap();

        match mir_inst {
            MirInstruction::BinOp { dst, op, lhs, rhs } => {
                assert_eq!(dst, ValueId(20));
                assert_eq!(op, BinaryOp::Add);
                assert_eq!(lhs, ValueId(10));
                assert_eq!(rhs, ValueId(11));
            }
            _ => panic!("Expected BinOp instruction"),
        }
    }

    #[test]
    fn test_convert_compare_inst() {
        let join_cmp = MirLikeInst::Compare {
            dst: ValueId(30),
            op: CompareOp::Ge,
            lhs: ValueId(10),
            rhs: ValueId(11),
        };

        let mir_inst = convert_mir_like_inst(&join_cmp).unwrap();

        match mir_inst {
            MirInstruction::Compare { dst, op, lhs, rhs } => {
                assert_eq!(dst, ValueId(30));
                assert_eq!(op, MirCompareOp::Ge);
                assert_eq!(lhs, ValueId(10));
                assert_eq!(rhs, ValueId(11));
            }
            _ => panic!("Expected Compare instruction"),
        }
    }
}