/*
 * nanowasm, a tiny WebAssembly/Wasm interpreter
 * Copyright (C) 2023-2024  Xavier Del Campo Romero
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

#include <nw/log.h>
#include <nw/ops.h>
#include <nanowasm/nw.h>
#include <nw/interp.h>
#include <nw/types.h>
#include <inttypes.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

/* Inspired by "INT32-C. Ensure that operations on signed integers do
 * not result in overflow". */
static bool signed_overflow(const int32_t a, const int32_t b)
{
    return (b > 0 && a < INT32_MIN + b)
        || (b < 0 && a > INT32_MAX + b);
}

int op_i32_sub(struct nw_interp *const i)
{
    int32_t op1, op2;

    if (interp_stack_pop(i, &op2, sizeof op2))
    {
        LOG("%s: interp_stack_pop %s failed\n", __func__, "op2");
        return -1;
    }
    else if (interp_stack_pop(i, &op1, sizeof op1))
    {
        LOG("%s: interp_stack_pop %s failed\n", __func__, "op1");
        return -1;
    }
    else if (signed_overflow(op2, op1))
    {
        LOG("%s: signed integer overflow (op1=%" PRIi32 ", op2=%" PRIi32 ")\n",
            __func__, op1, op2);
        i->exception = "signed integer overflow";
        return 1;
    }

    const int32_t result = op2 - op1;

    if (interp_stack_push(i, &result, sizeof result))
    {
        LOG("%s: interp_stack_push failed\n", __func__);
        return -1;
    }

    return 0;
}

int check_i32_sub(FILE *const f)
{
    return 0;
}