/*
 * 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/search.h>
#include <nw/log.h>
#include <nw/fstring.h>
#include <nw/sections.h>
#include <nanowasm/nw.h>
#include <nw/types.h>
#include <errno.h>
#include <stdint.h>
#include <string.h>

static int ensure_export(const char *const fn,
    const struct nw_mod *const m, FILE *const f, varuint32 *const out)
{
    if (!m->sections.export)
    {
        LOG("%s: export section not found", __func__);
        return -1;
    }
    else if (fseek(f, m->sections.export, SEEK_SET))
    {
        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    varuint32 count;

    if (varuint32_read(f, &count))
    {
        LOG("%s: varuint32_read failed\n", __func__);
        return -1;
    }

    for (varuint32 i = 0; i < count; i++)
    {
        varuint32 len;
        bool found = false;

        if (varuint32_read(f, &len))
        {
            LOG("%s: varuint32_read failed\n", __func__);
            return -1;
        }
        else if (len != strlen(fn))
        {
            if (fseek(f, len, SEEK_CUR))
            {
                LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
                return -1;
            }
        }
        else if (!fstrcmp(fn, f, false))
            found = true;

        uint8_t kind;

        if (!fread(&kind, sizeof kind, 1, f))
        {
            LOG("%s: fread(3) failed: feof=%d, ferror=%d\n", __func__,
                feof(f), ferror(f));
            return -1;
        }

        varuint32 index;

        if (varuint32_read(f, &index))
        {
            LOG("%s: varuint32_read failed\n", __func__);
            return -1;
        }
        else if (found)
        {
            if (kind != NW_KIND_FUNCTION)
            {
                LOG("%s: expected kind %d, got %d\n", __func__,
                    NW_KIND_FUNCTION, kind);
                return -1;
            }

            *out = index;
            return 0;
        }
    }

    return -1;
}

static int get_function_index(const struct nw_mod *const m,
    const varuint32 index, varuint32 *const findex)
{
    const size_t n = m->cfg.n_imports;

    if (index < n)
    {
        LOG("%s: index (%lu) must be greater than number of imports (%zu)\n",
            __func__, (unsigned long)index, n);
        return -1;
    }

    *findex = index - n;
    return 0;
}

static int get_fn_start(const struct nw_mod *const m, FILE *const f,
    const varuint32 index, struct search_fn *const out)
{
    const struct section s =
    {
        .cfg = &m->cfg,
        .f = f
    };

    struct section_function sf;
    struct section_code c;

    if (section_function(&s, m, index, &sf))
    {
        LOG("%s: section_function failed\n", __func__);
        return -1;
    }
    else if (section_code(&s, m, index, &c))
    {
        LOG("%s: section_code failed\n", __func__);
        return -1;
    }

    out->start = c.start;
    out->index = index;
    return 0;
}

int search_exported_fn(const char *const fn, const struct nw_mod *const m,
    FILE *const f, struct search_fn *const out)
{
    varuint32 index, findex;

    if (ensure_export(fn, m, f, &index))
    {
        LOG("%s: %s not an exported function\n", __func__, fn);
        return -1;
    }
    else if (get_function_index(m, index, &findex))
    {
        LOG("%s: get_function_index failed\n", __func__);
        return -1;
    }
    else if (get_fn_start(m, f, findex, out))
    {
        LOG("%s: get_fn_start %s failed\n", __func__, fn);
        return -1;
    }

    return 0;
}

int search_fn(const varuint32 index, const struct nw_mod *const m,
    FILE *const f, struct search_fn *const out)
{
    varuint32 findex;

    if (get_function_index(m, index, &findex))
    {
        LOG("%s: get_function_index failed\n", __func__);
        return -1;
    }
    else if (get_fn_start(m, f, findex, out))
    {
        LOG("%s: get_fn_start failed\n", __func__);
        return -1;
    }

    return 0;
}