#include "ccc.h"
#include "ast.h"
#include <stdlib.h>
#include <stdio.h>

static void emit_stmt(FILE* outfile, const struct stmt_node* node);
static void emit_expr(
    FILE* outfile,
    const struct expr_node* node,
    const char* reg);

static void emit_int_lit(
    FILE* outfile,
    const struct int_lit_node* node,
    const char* reg
) {
   fprintf(outfile, "\tmov %s, %lld\n", reg, node->val); 
}

static void emit_expr(
    FILE* outfile,
    const struct expr_node* node,
    const char* reg
) {
    switch (node->type) {
        case EXPR_EMPTY:
            break;
        case EXPR_INT_LIT:
            emit_int_lit(outfile, &node->as._int_lit, reg);
            break;
    }
}

static void emit_var_decl(FILE* outfile, const struct var_decl_node* node) {
    /* TODO: make do smth */
}

static void emit_return(FILE* outfile, const struct return_node* node) {
    if (node->ret_val != NULL) emit_expr(outfile, node->ret_val, "rax");
    fprintf(outfile, "\tret\n");
}

static void emit_group(FILE* outfile, const struct group_node* node) {
    const struct stmt_node* body_node = node->body_head;
    while (body_node != NULL) {
        emit_stmt(outfile, body_node);
        body_node = body_node->next;
    }
}

static void emit_stmt(FILE* outfile, const struct stmt_node* node) {
    switch (node->type) {
        case STMT_VAR_DECL:
            emit_var_decl(outfile, &node->as._var_decl);
            break;
        case STMT_RETURN:
            emit_return(outfile, &node->as._return);
            break;
        case STMT_EXPR:
            emit_expr(outfile, &node->as._expr, NULL);
            break;
        case STMT_GROUP:
            emit_group(outfile, &node->as._group);
            break;
    }
}

static void emit_fn_decl(FILE* outfile, const struct fn_decl_node* node) {
    fprintf(outfile, "%s:\n", node->name);
    /* TODO: probably something to map the args to temporaries lol */
    emit_group(outfile, &node->body);
}

static void emit_root_node(FILE* outfile, const struct root_node* node) {
    switch (node->type) {
        case ROOT_FN_DECL:
            emit_fn_decl(outfile, &node->as._fn_decl);
            break;
    }
}

void emit_code(const struct root_node* ast, const char* path) {
    FILE* outfile = fopen(path, "w");
    if (outfile == NULL) CCC_PANIC;

    fprintf(outfile, "section .text\n");

    /* output all non-static function declarations as globals */
    const struct root_node* node = ast;
    while (node != NULL) {
        if (node->type == ROOT_FN_DECL)
            fprintf(outfile, "global %s\n", node->as._fn_decl.name);

        node = node->next;
    }

    fprintf(outfile, "\n");

    /* actual code body */
    node = ast;
    while (node != NULL) {
        emit_root_node(outfile, node);
        fprintf(outfile, "\n");
        node = node->next;
    }

    fclose(outfile);
}