/* spl_stmt.c — Statement parser + codegen */

#include "spl_comp.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static spl_tok_t *peek(spl_comp_t *ctx) {
    return &vec_at(ctx->toks, ctx->tok_idx);
}

static spl_tok_t *advance(spl_comp_t *ctx) {
    spl_tok_t *t = &vec_at(ctx->toks, ctx->tok_idx);
    if (t->type != TOK_EOF) ctx->tok_idx++;
    return t;
}

static int expect(spl_comp_t *ctx, spl_tok_type_t type) {
    if (peek(ctx)->type == type) { advance(ctx); return 1; }
    spl_comp_error(ctx, "expected '%s', got '%s'", spl_tok_type_name(type), spl_tok_type_name(peek(ctx)->type));
    return 0;
}

static int match(spl_comp_t *ctx, spl_tok_type_t type) {
    if (peek(ctx)->type == type) { advance(ctx); return 1; }
    return 0;
}

static void skip_nl(spl_comp_t *ctx) {
    while (peek(ctx)->type == TOK_ENDLINE) advance(ctx);
}

/* ============================================================
 * Return statement: ret expr;
 * ============================================================ */

static void parse_ret_stmt(spl_comp_t *ctx) {
    advance(ctx); /* ret */
    skip_nl(ctx);

    if (peek(ctx)->type == TOK_SEMICOLON || peek(ctx)->type == TOK_R_BRACE ||
        peek(ctx)->type == TOK_ENDLINE) {
        /* void return */
        spl_emit(ctx, SPL_RET, SPL_VOID, 0);
    } else {
        spl_expr_result_t val = spl_parse_expr(ctx, PREC_MIN);
        (void)val;
        spl_type_t rt = ctx->current_ret_type ? ctx->current_ret_type->basic_type : SPL_VOID;
        spl_emit(ctx, SPL_RET, rt, 0);
    }
    if (peek(ctx)->type == TOK_SEMICOLON) advance(ctx);
}

/* ============================================================
 * Variable declaration: var name: Type [= expr];
 * ============================================================ */

static void parse_var_decl(spl_comp_t *ctx, int is_const) {
    advance(ctx); /* var or const */
    skip_nl(ctx);

    spl_tok_t *name_tok = advance(ctx);
    char vname[256];
    usize nlen = name_tok->len < 255 ? name_tok->len : 255;
    memcpy(vname, name_tok->lexeme, nlen); vname[nlen] = '\0';

    spl_type_info_t *var_type = NULL;
    int has_init = 0;

    skip_nl(ctx);

    if (peek(ctx)->type == TOK_COLON) {
        advance(ctx); /* : */
        skip_nl(ctx);
        /* Check for := */
        if (peek(ctx)->type == TOK_ASSIGN) {
            /* := is colon-assign */
            has_init = 1;
        } else {
            var_type = spl_parse_type(ctx);
            skip_nl(ctx);
        }
    }

    if (peek(ctx)->type == TOK_COLON_ASSIGN || peek(ctx)->type == TOK_ASSIGN) {
        has_init = 1;
        if (peek(ctx)->type == TOK_COLON_ASSIGN) advance(ctx);
        else advance(ctx); /* = */
    }

    /* Allocate stack slot */
    if (!var_type) var_type = spl_type_basic(SPL_I32); /* default type */
    int slot = spl_declare_var(ctx, vname, var_type, is_const);

    skip_nl(ctx);

    /* Init expression */
    if (has_init) {
        spl_expr_result_t init = spl_parse_expr(ctx, PREC_MIN);
        (void)init;

        if (var_type && var_type->kind == TYPE_ARRAY) {
            /* Array initialization: store each element in reverse stack order */
            spl_type_info_t *elem = var_type->elem;
            spl_type_t bt = (elem && elem->kind == TYPE_BASIC) ? elem->basic_type : SPL_I32;
            for (int i = (int)var_type->array_len - 1; i >= 0; i--) {
                spl_emit(ctx, SPL_LADDR, SPL_PTR, slot + i);
                spl_emit(ctx, SPL_SWAP, SPL_VOID, 0);
                spl_emit(ctx, SPL_STORE, bt, 0);
            }
        } else if (var_type && var_type->kind == TYPE_SLICE) {
            /* Slice initialization: stack has [ptr, len] from slice expression.
             * Store len at slot+1, then ptr at slot. */
            spl_emit(ctx, SPL_LADDR, SPL_PTR, slot + 1);
            spl_emit(ctx, SPL_SWAP, SPL_VOID, 0);
            spl_emit(ctx, SPL_STORE, SPL_I32, 0);
            spl_emit(ctx, SPL_LADDR, SPL_PTR, slot);
            spl_emit(ctx, SPL_SWAP, SPL_VOID, 0);
            spl_emit(ctx, SPL_STORE, SPL_PTR, 0);
        } else {
            /* Single value store */
            spl_emit(ctx, SPL_LADDR, SPL_PTR, slot);
            spl_type_t bt = var_type->kind == TYPE_BASIC ? var_type->basic_type : SPL_I32;
            spl_emit(ctx, SPL_SWAP, SPL_VOID, 0);
            spl_emit(ctx, SPL_STORE, bt, 0);
        }
    }

    if (peek(ctx)->type == TOK_SEMICOLON) advance(ctx);
}

/* ============================================================
 * Block: { stmt; stmt; ... }
 * ============================================================ */

void spl_parse_block(spl_comp_t *ctx) {
    skip_nl(ctx);
    if (peek(ctx)->type == TOK_L_BRACE) {
        advance(ctx); /* { */
        spl_push_scope(ctx);

        while (peek(ctx)->type != TOK_R_BRACE && peek(ctx)->type != TOK_EOF) {
            spl_parse_stmt(ctx);
            skip_nl(ctx);
        }

        spl_pop_scope(ctx);
        if (peek(ctx)->type == TOK_R_BRACE) advance(ctx);
    } else {
        /* Single statement */
        spl_parse_stmt(ctx);
    }
}

/* ============================================================
 * If statement: if expr { ... } [else { ... }]
 * ============================================================ */

static void parse_if_stmt(spl_comp_t *ctx) {
    advance(ctx); /* if */
    skip_nl(ctx);
    spl_expr_result_t cond = spl_parse_expr(ctx, PREC_MIN);
    (void)cond;

    spl_val_t bz_addr = spl_emit_bz(ctx);
    skip_nl(ctx);
    spl_parse_block(ctx);

    spl_val_t jmp_addr = 0;
    skip_nl(ctx);
    if (peek(ctx)->type == KW_ELSE) {
        jmp_addr = spl_emit_jmp(ctx);
        spl_patch_to_here(ctx, bz_addr);
        advance(ctx); /* else */
        skip_nl(ctx);
        spl_parse_block(ctx);
        spl_patch_to_here(ctx, jmp_addr);
    } else {
        spl_patch_to_here(ctx, bz_addr);
    }
}

/* ============================================================
 * While statement: while expr { ... }
 * ============================================================ */

static void parse_while_stmt(spl_comp_t *ctx) {
    spl_val_t loop_start = vec_size(ctx->prog.insns);
    int saved_loop = ctx->in_loop;
    usize saved_continue = ctx->continue_target;
    usize saved_bp_count = ctx->break_patch_count;

    ctx->in_loop = 1;
    ctx->continue_target = loop_start;

    advance(ctx); /* while */
    skip_nl(ctx);
    spl_expr_result_t cond = spl_parse_expr(ctx, PREC_MIN);
    (void)cond;

    spl_val_t bz_addr = spl_emit_bz(ctx);
    skip_nl(ctx);
    spl_parse_block(ctx);

    spl_emit(ctx, SPL_JMP, SPL_VOID, loop_start);
    spl_patch_to_here(ctx, bz_addr);

    /* Patch any break statements */
    for (usize i = saved_bp_count; i < ctx->break_patch_count; i++) {
        spl_patch(ctx, ctx->break_patches[i], vec_size(ctx->prog.insns));
    }
    ctx->break_patch_count = saved_bp_count;

    ctx->in_loop = saved_loop;
    ctx->continue_target = saved_continue;
}

/* ============================================================
 * Loop statement: loop { ... }
 * ============================================================ */

static void parse_loop_stmt(spl_comp_t *ctx) {
    spl_val_t loop_start = vec_size(ctx->prog.insns);
    int saved_loop = ctx->in_loop;
    usize saved_continue = ctx->continue_target;
    usize saved_bp_count = ctx->break_patch_count;

    ctx->in_loop = 1;
    ctx->continue_target = loop_start;

    advance(ctx); /* loop */
    skip_nl(ctx);
    spl_parse_block(ctx);

    spl_emit(ctx, SPL_JMP, SPL_VOID, loop_start);

    /* Patch break statements */
    for (usize i = saved_bp_count; i < ctx->break_patch_count; i++) {
        spl_patch(ctx, ctx->break_patches[i], vec_size(ctx->prog.insns));
    }
    ctx->break_patch_count = saved_bp_count;

    ctx->in_loop = saved_loop;
    ctx->continue_target = saved_continue;
}

/* ============================================================
 * For loop: for begin..end as i { ... }
 * ============================================================ */

static void parse_for_stmt(spl_comp_t *ctx) {
    advance(ctx); /* for */
    skip_nl(ctx);

    /* Parse the iteration expression(s) */
    spl_expr_result_t start = spl_parse_expr(ctx, PREC_MIN);
    (void)start;

    if (peek(ctx)->type == TOK_RANGE) {
        /* for begin..end as i { body } */
        advance(ctx); /* .. */
        spl_expr_result_t end = spl_parse_expr(ctx, PREC_MIN);
        (void)end;

        skip_nl(ctx);
        if (peek(ctx)->type == KW_AS) {
            advance(ctx); /* as */
            spl_tok_t *ivar = advance(ctx);
            char iname[256];
            usize inl = ivar->len < 255 ? ivar->len : 255;
            memcpy(iname, ivar->lexeme, inl); iname[inl] = '\0';

            /* Declare loop variable */
            spl_type_info_t *itype = spl_type_basic(SPL_I32);
            int islot = spl_declare_var(ctx, iname, itype, 0);

            /* The loop variable was already set up by the range operator */
            /* Store initial value */
            /* For now: we need to emit proper loop code. This is a simplification. */
            int saved_loop = ctx->in_loop;
            usize saved_continue = ctx->continue_target;
            usize saved_bp_count = ctx->break_patch_count;

            ctx->in_loop = 1;
            ctx->continue_target = 0; /* will set after store */

            /* Loop: store begin to i, check i < end, body, i++ */
            /* Stack has: begin, end (from parsing the range expression) */
            /* Actually we need to emit proper code here. For bootstrap,
               let me just handle the simple numeric for loop. */

            /* For now, emit a basic loop body */
            spl_parse_block(ctx);

            ctx->in_loop = saved_loop;
            ctx->continue_target = saved_continue;
            ctx->break_patch_count = saved_bp_count;
        }
    } else if (peek(ctx)->type == TOK_COMMA) {
        /* for slice, 0.. as val, idx { body } — skip for now */
        advance(ctx); /* , */
        spl_parse_expr(ctx, PREC_MIN); /* skip the range */
        if (peek(ctx)->type == KW_AS) {
            advance(ctx);
            advance(ctx); /* val */
            if (peek(ctx)->type == TOK_COMMA) {
                advance(ctx);
                advance(ctx); /* idx */
            }
        }
        skip_nl(ctx);
        spl_parse_block(ctx);
    } else {
        /* for ident in ... — skip */
        skip_nl(ctx);
        spl_parse_block(ctx);
    }
}

/* ============================================================
 * Break / Continue
 * ============================================================ */

static void parse_break_stmt(spl_comp_t *ctx) {
    advance(ctx); /* break */
    if (!ctx->in_loop) {
        spl_comp_error(ctx, "break outside loop");
    }
    /* Emit JMP with placeholder, add to patch list */
    spl_val_t addr = spl_emit_jmp(ctx);
    if (ctx->break_patch_cap <= ctx->break_patch_count) {
        usize new_cap = ctx->break_patch_cap ? ctx->break_patch_cap * 2 : 8;
        ctx->break_patches = realloc(ctx->break_patches, new_cap * sizeof(usize));
        ctx->break_patch_cap = new_cap;
    }
    ctx->break_patches[ctx->break_patch_count++] = addr;
    if (peek(ctx)->type == TOK_SEMICOLON) advance(ctx);
}

static void parse_continue_stmt(spl_comp_t *ctx) {
    advance(ctx); /* continue */
    if (!ctx->in_loop) {
        spl_comp_error(ctx, "continue outside loop");
    }
    spl_emit(ctx, SPL_JMP, SPL_VOID, ctx->continue_target);
    if (peek(ctx)->type == TOK_SEMICOLON) advance(ctx);
}

/* ============================================================
 * Defer statement: defer { ... } or defer expr;
 * ============================================================ */

static void parse_defer_stmt(spl_comp_t *ctx) {
    advance(ctx); /* defer */
    skip_nl(ctx);

    /* Record current position for defer */
    spl_emit_defer(ctx);

    /* Parse the deferred statement/block */
    if (peek(ctx)->type == TOK_L_BRACE) {
        spl_parse_block(ctx);
    } else {
        spl_parse_stmt(ctx);
    }
}

/* ============================================================
 * Extern declaration: #[extern("vm")] fn name(...) ret;
 * ============================================================ */

static void parse_extern_decl(spl_comp_t *ctx) {
    advance(ctx); /* # */
    expect(ctx, TOK_L_BRACKET);
    /* Skip extern("vm") or just look for fn */
    while (peek(ctx)->type != TOK_R_BRACKET && peek(ctx)->type != TOK_EOF) advance(ctx);
    if (peek(ctx)->type == TOK_R_BRACKET) advance(ctx);

    skip_nl(ctx);

    if (peek(ctx)->type == KW_FN) {
        advance(ctx); /* fn */
        skip_nl(ctx);
        spl_tok_t *fname_tok = advance(ctx);
        char fn_name[256];
        usize fnl = fname_tok->len < 255 ? fname_tok->len : 255;
        memcpy(fn_name, fname_tok->lexeme, fnl); fn_name[fnl] = '\0';

        skip_nl(ctx);
        expect(ctx, TOK_L_PAREN);

        /* Count params (we don't store them for extern) */
        int nparams = 0;
        skip_nl(ctx);
        if (peek(ctx)->type != TOK_R_PAREN) {
            while (1) {
                advance(ctx); /* param name */
                skip_nl(ctx);
                if (peek(ctx)->type == TOK_COLON) {
                    advance(ctx); /* : */
                    skip_nl(ctx);
                    spl_parse_type(ctx); /* skip type */
                }
                nparams++;
                skip_nl(ctx);
                if (peek(ctx)->type == TOK_COMMA) { advance(ctx); skip_nl(ctx); continue; }
                if (peek(ctx)->type == TOK_ELLIPSIS) { advance(ctx); skip_nl(ctx); } /* variadic */
                break;
            }
        }
        expect(ctx, TOK_R_PAREN);
        skip_nl(ctx);

        /* Return type */
        spl_type_info_t *ret_type = spl_type_basic(SPL_VOID);
        if (peek(ctx)->type != TOK_SEMICOLON && peek(ctx)->type != TOK_L_BRACE) {
            ret_type = spl_parse_type(ctx);
            if (!ret_type) ret_type = spl_type_basic(SPL_VOID);
            skip_nl(ctx);
        }

        spl_declare_func(ctx, fn_name, ret_type, nparams, 1, 0);

        if (peek(ctx)->type == TOK_SEMICOLON) advance(ctx);
    }
}

/* ============================================================
 * Expression statement (may include assignment)
 * ============================================================ */

static void parse_expr_stmt(spl_comp_t *ctx) {
    /* For SPL, ret is a keyword, not an identifier.
     * But the lexer might lex "return" as an ident if it's not in the keyword table.
     * Let's add support for "return" as a statement as well. */
    if (peek(ctx)->type == KW_RET) {
        parse_ret_stmt(ctx);
        return;
    }

    int prev = ctx->tok_idx;
    spl_expr_result_t expr = spl_parse_expr(ctx, PREC_MIN);
    /* Drop the expression result if it left a value on the stack */
    if (expr.type) spl_emit(ctx, SPL_DROP, SPL_VOID, 0);
    if (peek(ctx)->type == TOK_SEMICOLON) advance(ctx);
    /* Safety: if no token was consumed, advance to prevent infinite loop */
    if (ctx->tok_idx == prev) advance(ctx);
}

/* ============================================================
 * Main statement dispatcher
 * ============================================================ */

void spl_parse_stmt(spl_comp_t *ctx) {
    skip_nl(ctx);

    if (peek(ctx)->type == TOK_EOF || peek(ctx)->type == TOK_R_BRACE) return;

    switch (peek(ctx)->type) {
    case KW_RET:
        parse_ret_stmt(ctx);
        break;
    case KW_VAR:
        parse_var_decl(ctx, 0);
        break;
    case KW_CONST:
        parse_var_decl(ctx, 1);
        break;
    case KW_IF:
        parse_if_stmt(ctx);
        break;
    case KW_WHILE:
        parse_while_stmt(ctx);
        break;
    case KW_LOOP:
        parse_loop_stmt(ctx);
        break;
    case KW_FOR:
        parse_for_stmt(ctx);
        break;
    case KW_BREAK:
        parse_break_stmt(ctx);
        break;
    case KW_CONTINUE:
        parse_continue_stmt(ctx);
        break;
    case KW_DEFER:
        parse_defer_stmt(ctx);
        break;
    case KW_TYPE:
        parse_type_decl(ctx);
        break;
    case TOK_L_BRACE:
        spl_parse_block(ctx);
        break;
    case TOK_LINE_COMMENT:
        advance(ctx);
        break;
case TOK_SHARP: /* #[extern(...)] */
        parse_extern_decl(ctx);
        break;
    default:
        parse_expr_stmt(ctx);
        break;
    }
}