"""
Return instruction lowering
Handles void and value returns
"""

import llvmlite.ir as ir
from typing import Dict, Optional, Any

def lower_return(
    builder: ir.IRBuilder,
    value_id: Optional[int],
    vmap: Dict[int, ir.Value],
    return_type: ir.Type,
    resolver=None,
    preds=None,
    block_end_values=None,
    bb_map=None,
    ctx: Optional[Any] = None,
) -> None:
    """
    Lower MIR Return instruction
    
    Args:
        builder: Current LLVM IR builder
        value_id: Optional return value ID
        vmap: Value map
        return_type: Expected return type
    """
    # Prefer BuildCtx maps if provided
    if ctx is not None:
        try:
            if getattr(ctx, 'resolver', None) is not None:
                resolver = ctx.resolver
            if getattr(ctx, 'preds', None) is not None and preds is None:
                preds = ctx.preds
            if getattr(ctx, 'block_end_values', None) is not None and block_end_values is None:
                block_end_values = ctx.block_end_values
            if getattr(ctx, 'bb_map', None) is not None and bb_map is None:
                bb_map = ctx.bb_map
        except Exception:
            pass
    if value_id is None:
        # Void return
        builder.ret_void()
    else:
        # Get return value (prefer resolver)
        ret_val = None
        if resolver is not None and preds is not None and block_end_values is not None and bb_map is not None:
            try:
                # If this block has a declared PHI for the return value, force using the
                # local PHI placeholder to ensure dominance and let finalize_phis wire it.
                try:
                    block_name = builder.block.name
                    cur_bid = int(str(block_name).replace('bb',''))
                except Exception:
                    cur_bid = -1
                try:
                    bm = getattr(resolver, 'block_phi_incomings', {}) or {}
                except Exception:
                    bm = {}
                if isinstance(value_id, int) and isinstance(bm.get(cur_bid), dict) and value_id in bm.get(cur_bid):
                    # Reuse predeclared ret-phi when available
                    cur = None
                    try:
                        rp = getattr(resolver, 'ret_phi_map', {}) or {}
                        key = (int(cur_bid), int(value_id))
                        if key in rp:
                            cur = rp[key]
                    except Exception:
                        cur = None
                    if cur is None:
                        btop = ir.IRBuilder(builder.block)
                        try:
                            btop.position_at_start(builder.block)
                        except Exception:
                            pass
                        # Reuse existing local phi if present; otherwise create
                        cur = vmap.get(value_id)
                        need_new = True
                        try:
                            need_new = not (cur is not None and hasattr(cur, 'add_incoming') and getattr(getattr(cur, 'basic_block', None), 'name', None) == builder.block.name)
                        except Exception:
                            need_new = True
                        if need_new:
                            cur = btop.phi(ir.IntType(64), name=f"phi_ret_{value_id}")
                    # Bind to maps
                    vmap[value_id] = cur
                    try:
                        if hasattr(resolver, 'global_vmap') and isinstance(resolver.global_vmap, dict):
                            resolver.global_vmap[value_id] = cur
                    except Exception:
                        pass
                    ret_val = cur
                if ret_val is not None:
                    builder.ret(ret_val)
                    return
                if isinstance(return_type, ir.PointerType):
                    ret_val = resolver.resolve_ptr(value_id, builder.block, preds, block_end_values, vmap)
                else:
                    # Prefer pointer→handle reboxing for string-ish returns even if function return type is i64
                    is_stringish = False
                    if hasattr(resolver, 'is_stringish'):
                        try:
                            is_stringish = resolver.is_stringish(int(value_id))
                        except Exception:
                            is_stringish = False
                    if is_stringish and hasattr(resolver, 'string_ptrs') and int(value_id) in getattr(resolver, 'string_ptrs'):
                        # Re-box known string pointer to handle
                        p = resolver.string_ptrs[int(value_id)]
                        i8p = ir.IntType(8).as_pointer()
                        i64 = ir.IntType(64)
                        boxer = None
                        for f in builder.module.functions:
                            if f.name == 'nyash.box.from_i8_string':
                                boxer = f; break
                        if boxer is None:
                            boxer = ir.Function(builder.module, ir.FunctionType(i64, [i8p]), name='nyash.box.from_i8_string')
                        ret_val = builder.call(boxer, [p], name='ret_ptr2h')
                    else:
                        ret_val = resolver.resolve_i64(value_id, builder.block, preds, block_end_values, vmap, bb_map)
            except Exception:
                ret_val = None
        if ret_val is None:
            ret_val = vmap.get(value_id)
        if not ret_val:
            # Default based on return type
            if isinstance(return_type, ir.IntType):
                ret_val = ir.Constant(return_type, 0)
            elif isinstance(return_type, ir.DoubleType):
                ret_val = ir.Constant(return_type, 0.0)
            else:
                # Pointer type - null
                ret_val = ir.Constant(return_type, None)
        
        # Type adjustment if needed
        if hasattr(ret_val, 'type') and ret_val.type != return_type:
            if isinstance(return_type, ir.IntType) and ret_val.type.is_pointer:
                # ptr to int
                ret_val = builder.ptrtoint(ret_val, return_type, name="ret_p2i")
            elif isinstance(return_type, ir.PointerType) and isinstance(ret_val.type, ir.IntType):
                # int to ptr
                ret_val = builder.inttoptr(ret_val, return_type, name="ret_i2p")
            elif isinstance(return_type, ir.IntType) and isinstance(ret_val.type, ir.IntType):
                # int to int conversion
                if return_type.width < ret_val.type.width:
                    # Truncate
                    ret_val = builder.trunc(ret_val, return_type)
                elif return_type.width > ret_val.type.width:
                    # Zero extend
                    ret_val = builder.zext(ret_val, return_type)
        
        builder.ret(ret_val)