use serde::{Deserialize, Serialize};
use crate::mir::{
    MirModule, MirFunction, FunctionSignature, BasicBlockId, MirInstruction,
    ConstValue, BinaryOp, MirType, EffectMask, MirPrinter, ValueId,
};

#[derive(Debug, Deserialize, Serialize)]
struct ProgramV0 {
    version: i32,
    kind: String,
    body: Vec<StmtV0>,
}

#[derive(Debug, Deserialize, Serialize)]
#[serde(tag = "type")]
enum StmtV0 {
    Return { expr: ExprV0 },
    Extern { iface: String, method: String, args: Vec<ExprV0> },
    // Optional: expression statement (side effects only)
    Expr { expr: ExprV0 },
    // Optional: local binding (Stage-2)
    Local { name: String, expr: ExprV0 },
    // Optional: if/else (Stage-2)
    If { cond: ExprV0, then: Vec<StmtV0>, #[serde(rename="else", default)] r#else: Option<Vec<StmtV0>> },
    // Optional: loop (Stage-2)
    Loop { cond: ExprV0, body: Vec<StmtV0> },
    Break,
    Continue,
    Try { #[serde(rename="try")] try_body: Vec<StmtV0>, #[serde(default)] catches: Vec<CatchV0>, #[serde(default)] finally: Vec<StmtV0> },
}

#[derive(Debug, Deserialize, Serialize, Clone, Default)]
struct CatchV0 {
    #[serde(rename="param", default)]
    param: Option<String>,
    #[serde(rename="typeHint", default)]
    type_hint: Option<String>,
    #[serde(default)]
    body: Vec<StmtV0>,
}

#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(tag = "type")]
enum ExprV0 {
    Int { value: serde_json::Value },
    Str { value: String },
    Bool { value: bool },
    Binary { op: String, lhs: Box<ExprV0>, rhs: Box<ExprV0> },
    Extern { iface: String, method: String, args: Vec<ExprV0> },
    Compare { op: String, lhs: Box<ExprV0>, rhs: Box<ExprV0> },
    Logical { op: String, lhs: Box<ExprV0>, rhs: Box<ExprV0> }, // short-circuit: &&, || (or: "and"/"or")
    // Stage-2 additions (optional):
    Call { name: String, args: Vec<ExprV0> },
    Method { recv: Box<ExprV0>, method: String, args: Vec<ExprV0> },
    New { class: String, args: Vec<ExprV0> },
    Var { name: String },
    Throw { expr: Box<ExprV0> },
}

pub fn parse_json_v0_to_module(json: &str) -> Result<MirModule, String> {
    let prog: ProgramV0 = serde_json::from_str(json).map_err(|e| format!("invalid JSON v0: {}", e))?;
    if prog.version != 0 || prog.kind != "Program" {
        return Err("unsupported IR: expected {version:0, kind:\"Program\"}".into());
    }
    // Create module and main function
    let mut module = MirModule::new("ny_json_v0".into());
    let sig = FunctionSignature { name: "main".into(), params: vec![], return_type: MirType::Integer, effects: EffectMask::PURE };
    let entry = BasicBlockId::new(0);
    let mut f = MirFunction::new(sig, entry);
    
    if prog.body.is_empty() { return Err("empty body".into()); }

    // Variable map for simple locals (Stage-2; currently minimal)
    let mut var_map: std::collections::HashMap<String, crate::mir::ValueId> = std::collections::HashMap::new();
    let start_bb = f.entry_block;
    let end_bb = lower_stmt_list_with_vars(&mut f, start_bb, &prog.body, &mut var_map)?;
    // Ensure function terminates: add `ret 0` to last un-terminated block (prefer end_bb else entry)
    let need_default_ret = f.blocks.iter().any(|(_k,b)| !b.is_terminated());
    if need_default_ret {
        let target_bb = end_bb;
        let dst_id = f.next_value_id();
        if let Some(bb) = f.get_block_mut(target_bb) {
            if !bb.is_terminated() {
                bb.add_instruction(MirInstruction::Const { dst: dst_id, value: ConstValue::Integer(0) });
                bb.set_terminator(MirInstruction::Return { value: Some(dst_id) });
            }
        }
    }
    // Keep return type unknown to allow dynamic display (VM/Interpreter)
    f.signature.return_type = MirType::Unknown;
    module.add_function(f);
    Ok(module)
}

fn next_block_id(f: &MirFunction) -> BasicBlockId {
    let mut mx = 0u32;
    for k in f.blocks.keys() { if k.0 >= mx { mx = k.0 + 1; } }
    BasicBlockId::new(mx)
}

fn lower_expr(f: &mut MirFunction, cur_bb: BasicBlockId, e: &ExprV0) -> Result<(crate::mir::ValueId, BasicBlockId), String> {
    match e {
        ExprV0::Int { value } => {
            // Accept number or stringified digits
            let ival: i64 = if let Some(n) = value.as_i64() {
                n
            } else if let Some(s) = value.as_str() { s.parse().map_err(|_| "invalid int literal")? } else {
                return Err("invalid int literal".into());
            };
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur_bb) {
                bb.add_instruction(MirInstruction::Const { dst, value: ConstValue::Integer(ival) });
            }
            Ok((dst, cur_bb))
        }
        ExprV0::Str { value } => {
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur_bb) {
                bb.add_instruction(MirInstruction::Const { dst, value: ConstValue::String(value.clone()) });
            }
            Ok((dst, cur_bb))
        }
        ExprV0::Bool { value } => {
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur_bb) {
                bb.add_instruction(MirInstruction::Const { dst, value: ConstValue::Bool(*value) });
            }
            Ok((dst, cur_bb))
        }
        ExprV0::Binary { op, lhs, rhs } => {
            let (l, cur_after_l) = lower_expr(f, cur_bb, lhs)?;
            let (r, cur_after_r) = lower_expr(f, cur_after_l, rhs)?;
            let bop = match op.as_str() { "+" => BinaryOp::Add, "-" => BinaryOp::Sub, "*" => BinaryOp::Mul, "/" => BinaryOp::Div, _ => return Err("unsupported op".into()) };
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur_after_r) {
                bb.add_instruction(MirInstruction::BinOp { dst, op: bop, lhs: l, rhs: r });
            }
            Ok((dst, cur_after_r))
        }
        ExprV0::Extern { iface, method, args } => {
            let (arg_ids, cur2) = lower_args(f, cur_bb, args)?;
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur2) {
                bb.add_instruction(MirInstruction::ExternCall { dst: Some(dst), iface_name: iface.clone(), method_name: method.clone(), args: arg_ids, effects: EffectMask::IO });
            }
            Ok((dst, cur2))
        }
        ExprV0::Compare { op, lhs, rhs } => {
            let (l, cur_after_l) = lower_expr(f, cur_bb, lhs)?;
            let (r, cur_after_r) = lower_expr(f, cur_after_l, rhs)?;
            let cop = match op.as_str() {
                "==" => crate::mir::CompareOp::Eq,
                "!=" => crate::mir::CompareOp::Ne,
                "<"  => crate::mir::CompareOp::Lt,
                "<=" => crate::mir::CompareOp::Le,
                ">"  => crate::mir::CompareOp::Gt,
                ">=" => crate::mir::CompareOp::Ge,
                _ => return Err("unsupported compare op".into()),
            };
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur_after_r) {
                bb.add_instruction(MirInstruction::Compare { dst, op: cop, lhs: l, rhs: r });
            }
            Ok((dst, cur_after_r))
        }
        ExprV0::Logical { op, lhs, rhs } => {
            // Short-circuit boolean logic with branches + phi
            let (l, cur_after_l) = lower_expr(f, cur_bb, lhs)?;
            let rhs_bb = next_block_id(f);
            let fall_bb = BasicBlockId::new(rhs_bb.0 + 1);
            let merge_bb = BasicBlockId::new(rhs_bb.0 + 2);
            f.add_block(crate::mir::BasicBlock::new(rhs_bb));
            f.add_block(crate::mir::BasicBlock::new(fall_bb));
            f.add_block(crate::mir::BasicBlock::new(merge_bb));
            // Branch depending on op
            let is_and = matches!(op.as_str(), "&&" | "and");
            if let Some(bb) = f.get_block_mut(cur_after_l) {
                if is_and {
                    bb.set_terminator(MirInstruction::Branch { condition: l, then_bb: rhs_bb, else_bb: fall_bb });
                } else {
                    // OR: if lhs true, go to fall_bb (true path), else evaluate rhs
                    bb.set_terminator(MirInstruction::Branch { condition: l, then_bb: fall_bb, else_bb: rhs_bb });
                }
            }
            // Telemetry: note short-circuit lowering
            crate::jit::events::emit_lower(
                serde_json::json!({
                    "id": "shortcircuit",
                    "op": if is_and { "and" } else { "or" },
                    "rhs_bb": rhs_bb.0,
                    "fall_bb": fall_bb.0,
                    "merge_bb": merge_bb.0
                }),
                "shortcircuit",
                "<json_v0>"
            );
            if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") { eprintln!("[bridge/logical] op={} rhs_bb={} fall_bb={} merge_bb={}", if is_and {"and"} else {"or"}, rhs_bb.0, fall_bb.0, merge_bb.0); }
            // false/true constant in fall_bb depending on op
            let cdst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(fall_bb) {
                let cval = if is_and { ConstValue::Bool(false) } else { ConstValue::Bool(true) };
                bb.add_instruction(MirInstruction::Const { dst: cdst, value: cval });
                bb.set_terminator(MirInstruction::Jump { target: merge_bb });
            }
            // evaluate rhs starting at rhs_bb and ensure the terminal block jumps to merge
            let (rval, rhs_end) = lower_expr(f, rhs_bb, rhs)?;
            if let Some(bb) = f.get_block_mut(rhs_end) {
                if !bb.is_terminated() { bb.set_terminator(MirInstruction::Jump { target: merge_bb }); }
            }
            if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") { eprintln!("[bridge/logical] rhs_end={} jump->merge_bb={}", rhs_end.0, merge_bb.0); }
            // merge with phi (use actual predecessors rhs_end and fall_bb)
            let out = f.next_value_id();
            if let Some(bb) = f.get_block_mut(merge_bb) {
                let mut inputs: Vec<(BasicBlockId, ValueId)> = vec![(fall_bb, cdst)];
                if rhs_end != fall_bb {
                    inputs.push((rhs_end, rval));
                } else {
                    // Degenerate case: RHS ended in fall_bb (e.g., constant expression).
                    // Reuse the constant to keep PHI well-formed.
                    inputs.push((fall_bb, rval));
                }
                inputs.sort_by_key(|(bbid, _)| bbid.0);
                bb.insert_instruction_after_phis(MirInstruction::Phi { dst: out, inputs });
            }
            Ok((out, merge_bb))
        }
        ExprV0::Call { name, args } => {
            // Special: array literal lowering — Call{name:"array.of", args:[...]} → new ArrayBox(); push(...); result=array
            if name == "array.of" {
                // Create array first
                let arr = f.next_value_id();
                if let Some(bb) = f.get_block_mut(cur_bb) {
                    bb.add_instruction(MirInstruction::NewBox { dst: arr, box_type: "ArrayBox".into(), args: vec![] });
                }
                // For each element: eval then push
                let mut cur = cur_bb;
                for e in args {
                    let (v, c) = lower_expr(f, cur, e)?; cur = c;
                    let tmp = f.next_value_id();
                    if let Some(bb) = f.get_block_mut(cur) {
                        bb.add_instruction(MirInstruction::BoxCall { dst: Some(tmp), box_val: arr, method: "push".into(), method_id: None, args: vec![v], effects: EffectMask::READ });
                    }
                }
                return Ok((arr, cur));
            }
            // Special: map literal lowering — Call{name:"map.of", args:[k1, v1, k2, v2, ...]} → new MapBox(); set(k,v)...; result=map
            if name == "map.of" {
                let mapv = f.next_value_id();
                if let Some(bb) = f.get_block_mut(cur_bb) {
                    bb.add_instruction(MirInstruction::NewBox { dst: mapv, box_type: "MapBox".into(), args: vec![] });
                }
                let mut cur = cur_bb;
                let mut it = args.iter();
                while let Some(k) = it.next() {
                    if let Some(v) = it.next() {
                        let (kv, cur2) = lower_expr(f, cur, k)?; cur = cur2;
                        let (vv, cur3) = lower_expr(f, cur, v)?; cur = cur3;
                        let tmp = f.next_value_id();
                        if let Some(bb) = f.get_block_mut(cur) {
                            bb.add_instruction(MirInstruction::BoxCall { dst: Some(tmp), box_val: mapv, method: "set".into(), method_id: None, args: vec![kv, vv], effects: EffectMask::READ });
                        }
                    } else { break; }
                }
                return Ok((mapv, cur));
            }
            // Fallback: treat as normal dynamic call
            let (arg_ids, cur) = lower_args(f, cur_bb, args)?;
            let fun_val = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur) {
                bb.add_instruction(MirInstruction::Const { dst: fun_val, value: ConstValue::String(name.clone()) });
            }
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur) {
                bb.add_instruction(MirInstruction::Call { dst: Some(dst), func: fun_val, args: arg_ids, effects: EffectMask::READ });
            }
            Ok((dst, cur))
        }
        ExprV0::Method { recv, method, args } => {
            // Heuristic: new ConsoleBox().println(x) → externcall env.console.log(x)
            let recv_is_console_new = matches!(&**recv, ExprV0::New { class, .. } if class == "ConsoleBox");
            if recv_is_console_new && (method == "println" || method == "print" || method == "log") {
                let (arg_ids, cur2) = lower_args(f, cur_bb, args)?;
                let dst = f.next_value_id();
                if let Some(bb) = f.get_block_mut(cur2) {
                    bb.add_instruction(MirInstruction::ExternCall { dst: Some(dst), iface_name: "env.console".into(), method_name: "log".into(), args: arg_ids, effects: EffectMask::READ });
                }
                return Ok((dst, cur2));
            }
            let (recv_v, cur) = lower_expr(f, cur_bb, recv)?;
            let (arg_ids, cur2) = lower_args(f, cur, args)?;
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur2) {
                bb.add_instruction(MirInstruction::BoxCall { dst: Some(dst), box_val: recv_v, method: method.clone(), method_id: None, args: arg_ids, effects: EffectMask::READ });
            }
            Ok((dst, cur2))
        }
        ExprV0::New { class, args } => {
            let (arg_ids, cur) = lower_args(f, cur_bb, args)?;
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur) {
                bb.add_instruction(MirInstruction::NewBox { dst, box_type: class.clone(), args: arg_ids });
            }
            Ok((dst, cur))
        }
        ExprV0::Var { name } => Err(format!("undefined variable in this context: {}", name)),
        ExprV0::Throw { expr } => {
            let (_ignored, cur) = lower_expr(f, cur_bb, expr)?;
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur) {
                bb.add_instruction(MirInstruction::Const { dst, value: ConstValue::Integer(0) });
            }
            Ok((dst, cur))
        }
    }
}

fn lower_expr_with_vars(
    f: &mut MirFunction,
    cur_bb: BasicBlockId,
    e: &ExprV0,
    vars: &mut std::collections::HashMap<String, crate::mir::ValueId>,
) -> Result<(crate::mir::ValueId, BasicBlockId), String> {
    match e {
        ExprV0::Var { name } => {
            if let Some(&vid) = vars.get(name) {
                return Ok((vid, cur_bb));
            }
            if name == "me" {
                // Optional gate: allow a dummy 'me' instance for Stage-2 JSON smoke
                if std::env::var("NYASH_BRIDGE_ME_DUMMY").ok().as_deref() == Some("1") {
                    let class = std::env::var("NYASH_BRIDGE_ME_CLASS").unwrap_or_else(|_| "Main".to_string());
                    let dst = f.next_value_id();
                    if let Some(bb) = f.get_block_mut(cur_bb) {
                        bb.add_instruction(MirInstruction::NewBox { dst, box_type: class, args: vec![] });
                    }
                    vars.insert("me".to_string(), dst);
                    return Ok((dst, cur_bb));
                } else {
                    return Err("undefined 'me' outside box context (set NYASH_BRIDGE_ME_DUMMY=1 to inject placeholder)".into());
                }
            }
            Err(format!("undefined variable: {}", name))
        }
        ExprV0::Throw { expr } => {
            let (_ignored, cur) = lower_expr_with_vars(f, cur_bb, expr, vars)?;
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur) {
                bb.add_instruction(MirInstruction::Const { dst, value: ConstValue::Integer(0) });
            }
            Ok((dst, cur))
        }
        ExprV0::Call { name, args } => {
            // Special: array literal lowering in vars context
            if name == "array.of" {
                let arr = f.next_value_id();
                if let Some(bb) = f.get_block_mut(cur_bb) {
                    bb.add_instruction(MirInstruction::NewBox { dst: arr, box_type: "ArrayBox".into(), args: vec![] });
                }
                let mut cur = cur_bb;
                for e in args {
                    let (v, c) = lower_expr_with_vars(f, cur, e, vars)?; cur = c;
                    let tmp = f.next_value_id();
                    if let Some(bb) = f.get_block_mut(cur) {
                        bb.add_instruction(MirInstruction::BoxCall { dst: Some(tmp), box_val: arr, method: "push".into(), method_id: None, args: vec![v], effects: EffectMask::READ });
                    }
                }
                return Ok((arr, cur));
            }
            // Special: map literal lowering in vars context
            if name == "map.of" {
                let mapv = f.next_value_id();
                if let Some(bb) = f.get_block_mut(cur_bb) {
                    bb.add_instruction(MirInstruction::NewBox { dst: mapv, box_type: "MapBox".into(), args: vec![] });
                }
                let mut cur = cur_bb;
                let mut it = args.iter();
                while let Some(k) = it.next() {
                    if let Some(v) = it.next() {
                        let (kv, cur2) = lower_expr_with_vars(f, cur, k, vars)?; cur = cur2;
                        let (vv, cur3) = lower_expr_with_vars(f, cur, v, vars)?; cur = cur3;
                        let tmp = f.next_value_id();
                        if let Some(bb) = f.get_block_mut(cur) {
                            bb.add_instruction(MirInstruction::BoxCall { dst: Some(tmp), box_val: mapv, method: "set".into(), method_id: None, args: vec![kv, vv], effects: EffectMask::READ });
                        }
                    } else { break; }
                }
                return Ok((mapv, cur));
            }
            // Lower args
            let (arg_ids, cur) = lower_args_with_vars(f, cur_bb, args, vars)?;
            // Encode as: const fun_name; call
            let fun_val = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur) {
                bb.add_instruction(MirInstruction::Const { dst: fun_val, value: ConstValue::String(name.clone()) });
            }
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur) {
                bb.add_instruction(MirInstruction::Call { dst: Some(dst), func: fun_val, args: arg_ids, effects: EffectMask::READ });
            }
            Ok((dst, cur))
        }
        ExprV0::Method { recv, method, args } => {
            let recv_is_console_new = matches!(&**recv, ExprV0::New { class, .. } if class == "ConsoleBox");
            if recv_is_console_new && (method == "println" || method == "print" || method == "log") {
                let (arg_ids, cur2) = lower_args_with_vars(f, cur_bb, args, vars)?;
                let dst = f.next_value_id();
                if let Some(bb) = f.get_block_mut(cur2) {
                    bb.add_instruction(MirInstruction::ExternCall { dst: Some(dst), iface_name: "env.console".into(), method_name: "log".into(), args: arg_ids, effects: EffectMask::READ });
                }
                return Ok((dst, cur2));
            }
            let (recv_v, cur) = lower_expr_with_vars(f, cur_bb, recv, vars)?;
            let (arg_ids, cur2) = lower_args_with_vars(f, cur, args, vars)?;
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur2) {
                bb.add_instruction(MirInstruction::BoxCall { dst: Some(dst), box_val: recv_v, method: method.clone(), method_id: None, args: arg_ids, effects: EffectMask::READ });
            }
            Ok((dst, cur2))
        }
        ExprV0::New { class, args } => {
            let (arg_ids, cur) = lower_args_with_vars(f, cur_bb, args, vars)?;
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur) {
                bb.add_instruction(MirInstruction::NewBox { dst, box_type: class.clone(), args: arg_ids });
            }
            Ok((dst, cur))
        }
        ExprV0::Binary { op, lhs, rhs } => {
            let (l, cur_after_l) = lower_expr_with_vars(f, cur_bb, lhs, vars)?;
            let (r, cur_after_r) = lower_expr_with_vars(f, cur_after_l, rhs, vars)?;
            let bop = match op.as_str() { "+" => BinaryOp::Add, "-" => BinaryOp::Sub, "*" => BinaryOp::Mul, "/" => BinaryOp::Div, _ => return Err("unsupported op".into()) };
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur_after_r) {
                bb.add_instruction(MirInstruction::BinOp { dst, op: bop, lhs: l, rhs: r });
            }
            Ok((dst, cur_after_r))
        }
        ExprV0::Compare { op, lhs, rhs } => {
            let (l, cur_after_l) = lower_expr_with_vars(f, cur_bb, lhs, vars)?;
            let (r, cur_after_r) = lower_expr_with_vars(f, cur_after_l, rhs, vars)?;
            let cop = match op.as_str() {
                "==" => crate::mir::CompareOp::Eq,
                "!=" => crate::mir::CompareOp::Ne,
                "<"  => crate::mir::CompareOp::Lt,
                "<=" => crate::mir::CompareOp::Le,
                ">"  => crate::mir::CompareOp::Gt,
                ">=" => crate::mir::CompareOp::Ge,
                _ => return Err("unsupported compare op".into()),
            };
            let dst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(cur_after_r) {
                bb.add_instruction(MirInstruction::Compare { dst, op: cop, lhs: l, rhs: r });
            }
            Ok((dst, cur_after_r))
        }
        ExprV0::Logical { op, lhs, rhs } => {
            let (l, cur_after_l) = lower_expr_with_vars(f, cur_bb, lhs, vars)?;
            let rhs_bb = next_block_id(f);
            let fall_bb = BasicBlockId::new(rhs_bb.0 + 1);
            let merge_bb = BasicBlockId::new(rhs_bb.0 + 2);
            f.add_block(crate::mir::BasicBlock::new(rhs_bb));
            f.add_block(crate::mir::BasicBlock::new(fall_bb));
            f.add_block(crate::mir::BasicBlock::new(merge_bb));
            let is_and = matches!(op.as_str(), "&&" | "and");
            if let Some(bb) = f.get_block_mut(cur_after_l) {
                if is_and {
                    bb.set_terminator(MirInstruction::Branch { condition: l, then_bb: rhs_bb, else_bb: fall_bb });
                } else {
                    bb.set_terminator(MirInstruction::Branch { condition: l, then_bb: fall_bb, else_bb: rhs_bb });
                }
            }
            let cdst = f.next_value_id();
            if let Some(bb) = f.get_block_mut(fall_bb) {
                let cval = if is_and { ConstValue::Bool(false) } else { ConstValue::Bool(true) };
                bb.add_instruction(MirInstruction::Const { dst: cdst, value: cval });
                bb.set_terminator(MirInstruction::Jump { target: merge_bb });
            }
            let (rval, rhs_end) = lower_expr_with_vars(f, rhs_bb, rhs, vars)?;
            if let Some(bb) = f.get_block_mut(rhs_end) { if !bb.is_terminated() { bb.set_terminator(MirInstruction::Jump { target: merge_bb }); } }
            let out = f.next_value_id();
            if let Some(bb) = f.get_block_mut(merge_bb) { bb.insert_instruction_after_phis(MirInstruction::Phi { dst: out, inputs: vec![(rhs_end, rval), (fall_bb, cdst)] }); }
            Ok((out, merge_bb))
        }
        _ => lower_expr(f, cur_bb, e),
    }
}

fn lower_stmt_with_vars(
    f: &mut MirFunction,
    cur_bb: BasicBlockId,
    s: &StmtV0,
    vars: &mut std::collections::HashMap<String, crate::mir::ValueId>,
) -> Result<BasicBlockId, String> {
    match s {
        StmtV0::Return { expr } => {
            let (v, cur) = lower_expr_with_vars(f, cur_bb, expr, vars)?;
            if let Some(bb) = f.get_block_mut(cur) { bb.set_terminator(MirInstruction::Return { value: Some(v) }); }
            Ok(cur)
        }
        StmtV0::Extern { iface, method, args } => {
            let (arg_ids, cur) = lower_args_with_vars(f, cur_bb, args, vars)?;
            if let Some(bb) = f.get_block_mut(cur) { bb.add_instruction(MirInstruction::ExternCall { dst: None, iface_name: iface.clone(), method_name: method.clone(), args: arg_ids, effects: EffectMask::IO }); }
            Ok(cur)
        }
        StmtV0::Expr { expr } => {
            let (_v, cur) = lower_expr_with_vars(f, cur_bb, expr, vars)?; Ok(cur)
        }
        StmtV0::Local { name, expr } => {
            let (v, cur) = lower_expr_with_vars(f, cur_bb, expr, vars)?; vars.insert(name.clone(), v); Ok(cur)
        }
        StmtV0::Break => {
            // Stage-3 placeholder: no-op until loop lowering supports break
            Ok(cur_bb)
        }
        StmtV0::Continue => {
            // Stage-3 placeholder: no-op until loop lowering supports continue
            Ok(cur_bb)
        }
        StmtV0::Try { try_body, .. } => {
            // Stage-3 placeholder: lower try body sequentially, ignore catches/finally for now
            let mut tmp_vars = vars.clone();
            let next_bb = lower_stmt_list_with_vars(f, cur_bb, try_body, &mut tmp_vars)?;
            *vars = tmp_vars;
            Ok(next_bb)
        }
        StmtV0::If { cond, then, r#else } => {
            // Lower condition first
            let (cval, cur) = lower_expr_with_vars(f, cur_bb, cond, vars)?;
            // Create then/else/merge blocks
            let then_bb = next_block_id(f);
            let else_bb = BasicBlockId::new(then_bb.0 + 1);
            let merge_bb = BasicBlockId::new(then_bb.0 + 2);
            f.add_block(crate::mir::BasicBlock::new(then_bb));
            f.add_block(crate::mir::BasicBlock::new(else_bb));
            f.add_block(crate::mir::BasicBlock::new(merge_bb));
            // Branch to then/else
            if let Some(bb) = f.get_block_mut(cur) {
                bb.set_terminator(MirInstruction::Branch { condition: cval, then_bb, else_bb });
            }

            // Clone current vars as branch-local maps
            let base_vars = vars.clone();
            let mut then_vars = base_vars.clone();
            let tend = lower_stmt_list_with_vars(f, then_bb, then, &mut then_vars)?;
            if let Some(bb) = f.get_block_mut(tend) {
                if !bb.is_terminated() { bb.set_terminator(MirInstruction::Jump { target: merge_bb }); }
            }

            let (else_end_pred, else_vars) = if let Some(elses) = r#else {
                let mut ev = base_vars.clone();
                let eend = lower_stmt_list_with_vars(f, else_bb, elses, &mut ev)?;
                if let Some(bb) = f.get_block_mut(eend) {
                    if !bb.is_terminated() { bb.set_terminator(MirInstruction::Jump { target: merge_bb }); }
                }
                (eend, ev)
            } else {
                // No else: empty path falls through with base vars
                if let Some(bb) = f.get_block_mut(else_bb) {
                    bb.set_terminator(MirInstruction::Jump { target: merge_bb });
                }
                (else_bb, base_vars.clone())
            };

            // PHI merge at merge_bb
            use std::collections::HashSet;
            let mut names: HashSet<String> = base_vars.keys().cloned().collect();
            // Also merge variables newly defined on both sides
            for k in then_vars.keys() { names.insert(k.clone()); }
            for k in else_vars.keys() { names.insert(k.clone()); }

            for name in names {
                let tv = then_vars.get(&name).copied();
                let ev = else_vars.get(&name).copied();
                // Only propagate if variable exists on both paths or existed before
                let exists_base = base_vars.contains_key(&name);
                match (tv, ev, exists_base) {
                    (Some(tval), Some( eval), _) => {
                        let merged = if tval == eval {
                            tval
                        } else {
                            let dst = f.next_value_id();
                            if let Some(bb) = f.get_block_mut(merge_bb) {
                                bb.insert_instruction_after_phis(MirInstruction::Phi { dst, inputs: vec![(tend, tval), (else_end_pred, eval)] });
                            }
                            dst
                        };
                        vars.insert(name, merged);
                    }
                    (Some(tval), None, true) => {
                        // Else path inherits base; merge then vs base
                        if let Some(&bval) = base_vars.get(&name) {
                            let merged = if tval == bval { tval } else {
                                let dst = f.next_value_id();
                                if let Some(bb) = f.get_block_mut(merge_bb) {
                                    bb.insert_instruction_after_phis(MirInstruction::Phi { dst, inputs: vec![(tend, tval), (else_end_pred, bval)] });
                                }
                                dst
                            };
                            vars.insert(name, merged);
                        }
                    }
                    (None, Some(eval), true) => {
                        // Then path inherits base; merge else vs base
                        if let Some(&bval) = base_vars.get(&name) {
                            let merged = if eval == bval { eval } else {
                                let dst = f.next_value_id();
                                if let Some(bb) = f.get_block_mut(merge_bb) {
                                    bb.insert_instruction_after_phis(MirInstruction::Phi { dst, inputs: vec![(tend, bval), (else_end_pred, eval)] });
                                }
                                dst
                            };
                            vars.insert(name, merged);
                        }
                    }
                    // If neither side has it, or only one side has it without base, skip (out-of-scope new var)
                    _ => {}
                }
            }

            Ok(merge_bb)
        }
        StmtV0::Loop { cond, body } => {
            // Create loop blocks
            let cond_bb = next_block_id(f);
            let body_bb = BasicBlockId::new(cond_bb.0 + 1);
            let exit_bb = BasicBlockId::new(cond_bb.0 + 2);
            f.add_block(crate::mir::BasicBlock::new(cond_bb));
            f.add_block(crate::mir::BasicBlock::new(body_bb));
            f.add_block(crate::mir::BasicBlock::new(exit_bb));

            // Preheader jump into cond
            if let Some(bb) = f.get_block_mut(cur_bb) {
                if !bb.is_terminated() { bb.add_instruction(MirInstruction::Jump { target: cond_bb }); }
            }

            // Snapshot base vars and set up PHI placeholders at cond for loop-carried vars
            let base_vars = vars.clone();
            let orig_names: Vec<String> = base_vars.keys().cloned().collect();
            let mut phi_map: std::collections::HashMap<String, crate::mir::ValueId> = std::collections::HashMap::new();
            for name in &orig_names {
                if let Some(&bval) = base_vars.get(name) {
                    let dst = f.next_value_id();
                    if let Some(bb) = f.get_block_mut(cond_bb) {
                        // Initial incoming from preheader
                        bb.insert_instruction_after_phis(MirInstruction::Phi { dst, inputs: vec![(cur_bb, bval)] });
                    }
                    phi_map.insert(name.clone(), dst);
                }
            }
            // Redirect current vars to PHIs for use in cond/body
            for (name, &phi) in &phi_map { vars.insert(name.clone(), phi); }

            // Lower condition using phi-backed vars
            let (cval, _cend) = lower_expr_with_vars(f, cond_bb, cond, vars)?;
            if let Some(bb) = f.get_block_mut(cond_bb) {
                bb.set_terminator(MirInstruction::Branch { condition: cval, then_bb: body_bb, else_bb: exit_bb });
            }

            // Lower body; record end block and body-out vars
            let mut body_vars = vars.clone();
            let bend = lower_stmt_list_with_vars(f, body_bb, body, &mut body_vars)?;
            if let Some(bb) = f.get_block_mut(bend) {
                if !bb.is_terminated() { bb.set_terminator(MirInstruction::Jump { target: cond_bb }); }
            }

            // Wire PHI second incoming from latch (body end)
            if let Some(bb) = f.get_block_mut(cond_bb) {
                for (name, &phi_dst) in &phi_map {
                    if let Some(&latch_val) = body_vars.get(name) {
                        for inst in &mut bb.instructions {
                            if let MirInstruction::Phi { dst, inputs } = inst {
                                if *dst == phi_dst {
                                    inputs.push((bend, latch_val));
                                    break;
                                }
                            }
                        }
                    }
                }
            }

            // After the loop, keep vars mapped to the PHI values (current loop state)
            for (name, &phi) in &phi_map { vars.insert(name.clone(), phi); }

            Ok(exit_bb)
        }
    }
}

fn lower_stmt_list_with_vars(
    f: &mut MirFunction,
    start_bb: BasicBlockId,
    stmts: &[StmtV0],
    vars: &mut std::collections::HashMap<String, crate::mir::ValueId>,
) -> Result<BasicBlockId, String> {
    let mut cur = start_bb;
    for s in stmts {
        cur = lower_stmt_with_vars(f, cur, s, vars)?;
        if let Some(bb) = f.blocks.get(&cur) { if bb.is_terminated() { break; } }
    }
    Ok(cur)
}
fn lower_args_with_vars(
    f: &mut MirFunction,
    cur_bb: BasicBlockId,
    args: &[ExprV0],
    vars: &mut std::collections::HashMap<String, crate::mir::ValueId>,
) -> Result<(Vec<crate::mir::ValueId>, BasicBlockId), String> {
    let mut out = Vec::with_capacity(args.len());
    let mut cur = cur_bb;
    for a in args {
        let (v, c) = lower_expr_with_vars(f, cur, a, vars)?; out.push(v); cur = c;
    }
    Ok((out, cur))
}

fn lower_args(f: &mut MirFunction, cur_bb: BasicBlockId, args: &[ExprV0]) -> Result<(Vec<crate::mir::ValueId>, BasicBlockId), String> {
    let mut out = Vec::with_capacity(args.len());
    let mut cur = cur_bb;
    for a in args {
        let (v, c) = lower_expr(f, cur, a)?; out.push(v); cur = c;
    }
    Ok((out, cur))
}

pub fn maybe_dump_mir(module: &MirModule) {
    if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
        let p = MirPrinter::new();
        println!("{}", p.print_module(module));
    }
}

// ========== Direct bridge (source → JSON v0 → MIR) ==========

#[derive(Clone, Debug)]
enum Tok {
    Return,
    Int(i64),
    Plus,
    Minus,
    Star,
    Slash,
    LParen,
    RParen,
    Eof,
}

fn lex(input: &str) -> Result<Vec<Tok>, String> {
    let bytes = input.as_bytes();
    let mut i = 0usize;
    let n = bytes.len();
    let mut toks = Vec::new();
    while i < n {
        let c = bytes[i] as char;
        // Treat semicolon as whitespace (Stage-1 minimal ASI: optional ';')
        if c.is_whitespace() || c == ';' { i += 1; continue; }
        match c {
            '+' => { toks.push(Tok::Plus); i+=1; }
            '-' => { toks.push(Tok::Minus); i+=1; }
            '*' => { toks.push(Tok::Star); i+=1; }
            '/' => { toks.push(Tok::Slash); i+=1; }
            '(' => { toks.push(Tok::LParen); i+=1; }
            ')' => { toks.push(Tok::RParen); i+=1; }
            '0'..='9' => {
                let start = i; while i<n { let cc = bytes[i] as char; if cc.is_ascii_digit() { i+=1; } else { break; } }
                let s = std::str::from_utf8(&bytes[start..i]).unwrap();
                let v: i64 = s.parse().map_err(|_| "invalid int")?;
                toks.push(Tok::Int(v));
            }
            'r' => {
                // return
                if i+6<=n && &input[i..i+6]=="return" { toks.push(Tok::Return); i+=6; } else { return Err("unexpected 'r'".into()); }
            }
            _ => return Err(format!("unexpected char '{}'", c)),
        }
    }
    toks.push(Tok::Eof);
    Ok(toks)
}

struct P { toks: Vec<Tok>, pos: usize }
impl P {
    fn new(toks: Vec<Tok>) -> Self { Self{ toks, pos:0 } }
    fn peek(&self) -> &Tok { self.toks.get(self.pos).unwrap() }
    fn next(&mut self) -> Tok { let t = self.toks.get(self.pos).unwrap().clone(); self.pos+=1; t }
    fn expect_return(&mut self) -> Result<(), String> { match self.next() { Tok::Return => Ok(()), _ => Err("expected 'return'".into()) } }
    fn parse_program(&mut self) -> Result<ExprV0, String> { self.expect_return()?; self.parse_expr() }
    fn parse_expr(&mut self) -> Result<ExprV0,String> {
        let mut left = self.parse_term()?;
        loop { match self.peek() { Tok::Plus => { self.next(); let r=self.parse_term()?; left = ExprV0::Binary{op:"+".into(), lhs:Box::new(left), rhs:Box::new(r)}; }, Tok::Minus => { self.next(); let r=self.parse_term()?; left = ExprV0::Binary{op:"-".into(), lhs:Box::new(left), rhs:Box::new(r)}; }, _ => break }
        }
        Ok(left)
    }
    fn parse_term(&mut self) -> Result<ExprV0,String> {
        let mut left = self.parse_factor()?;
        loop { match self.peek() { Tok::Star => { self.next(); let r=self.parse_factor()?; left = ExprV0::Binary{op:"*".into(), lhs:Box::new(left), rhs:Box::new(r)}; }, Tok::Slash => { self.next(); let r=self.parse_factor()?; left = ExprV0::Binary{op:"/".into(), lhs:Box::new(left), rhs:Box::new(r)}; }, _ => break }
        }
        Ok(left)
    }
    fn parse_factor(&mut self) -> Result<ExprV0,String> {
        match self.next() {
            Tok::Int(v) => Ok(ExprV0::Int{ value: serde_json::Value::from(v) }),
            Tok::LParen => { let e = self.parse_expr()?; match self.next() { Tok::RParen => Ok(e), _ => Err(") expected".into()) } }
            _ => Err("factor expected".into()),
        }
    }
}

pub fn parse_source_v0_to_json(input: &str) -> Result<String, String> {
    let toks = lex(input)?; let mut p = P::new(toks);
    let expr = p.parse_program()?;
    let prog = ProgramV0 { version:0, kind: "Program".into(), body: vec![StmtV0::Return{ expr }] };
    serde_json::to_string(&prog).map_err(|e| e.to_string())
}

pub fn parse_source_v0_to_module(input: &str) -> Result<MirModule, String> {
    let json = parse_source_v0_to_json(input)?;
    if std::env::var("NYASH_DUMP_JSON_IR").ok().as_deref() == Some("1") { println!("{}", json); }
    parse_json_v0_to_module(&json)
}