/*
 * 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 <nanowasm/nw.h>
#include <nw/opcodes.h>
#include <nw/interp.h>
#include <nw/sections.h>
#include <nw/types.h>
#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>

static int run(FILE *const f, const varuint32 idx, struct nw_interp *const in)
{
    return -1;
}

static int check_body(FILE *const f, const unsigned long n)
{
    unsigned long rem = n;

    while (rem)
    {
        const long before = ftell(f);
        uint8_t byte;

        if (before < 0)
        {
            LOG("%s: ftell(3) before: %s\n", __func__, strerror(errno));
            return -1;
        }
        else if (!fread(&byte, sizeof byte, 1, f))
        {
            LOG("%s: fread(3) failed, feof=%d, ferror=%d\n",
                __func__, feof(f), ferror(f));
            return -1;
        }
        else if (rem == 1 && byte != OP_END)
        {
            LOG("%s: unexpected opcode %#" PRIx8 " at body end\n",
                __func__, byte);
            return -1;
        }
        else if (interp_check_opcode(byte, f))
        {
            LOG("%s: interp_check_opcode failed\n", __func__);
            return -1;
        }

        const long after = ftell(f);

        if (after < 0)
        {
            LOG("%s: ftell(3) after: %s\n", __func__, strerror(errno));
            return -1;
        }

        rem -= after - before;
    }

    return 0;
}

static int push_i32(struct nw_interp *const i)
{
    const int32_t value = 0;

    return interp_stack_push(i, &value, sizeof value);
}

static int push_i64(struct nw_interp *const i)
{
    const int64_t value = 0;

    return interp_stack_push(i, &value, sizeof value);
}

static int push_f32(struct nw_interp *const i)
{
    const float value = 0;

    return interp_stack_push(i, &value, sizeof value);
}

static int push_f64(struct nw_interp *const i)
{
    const double value = 0;

    return interp_stack_push(i, &value, sizeof value);
}

static int push_locals(struct nw_interp *const in, const varuint32 count,
    const varint7 type)
{
    enum value_type vtype;

    if (get_value_type(type, &vtype))
    {
        LOG("%s: get_value_type failed\n", __func__);
        return -1;
    }

    static int (*const f[])(struct nw_interp *) =
    {
        [VALUE_TYPE_I32] = push_i32,
        [VALUE_TYPE_I64] = push_i64,
        [VALUE_TYPE_F32] = push_f32,
        [VALUE_TYPE_F64] = push_f64
    };

    for (varuint32 i = 0; i < count; i++)
        if (f[vtype](in))
        {
            LOG("%s: local variable push failed, type=%s, index=%lu\n",
                __func__, value_type_tostr(vtype), (unsigned long)i);
            return -1;
        }

    return 0;
}

static int check_local_group(FILE *const f, struct nw_interp *const i)
{
    varuint32 count;
    varint7 type;

    if (varuint32_read(f, &count))
    {
        LOG("%s: varuint32_read failed\n", __func__);
        return -1;
    }
    else if (varint7_read(f, &type))
    {
        LOG("%s: varint7_read failed\n", __func__);
        return -1;
    }
    else if (i && push_locals(i, count, type))
    {
        LOG("%s: push_locals failed\n", __func__);
        return -1;
    }

    return 0;
}

#if 0
static int run(FILE *const f, struct nw_interp *const in)
{
    varuint32 local_count;

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

    for (varuint32 i = 0; i < local_count; i++)
        if (check_local_group(f, in))
        {
            LOG("%s: check_local failed\n", __func__);
            return -1;
        }

    return 0;
}
#endif

static int push_frame(struct nw_interp *const i,
    const struct nw_frame *const src)
{
    struct nw_frame *const dst = interp_stackptr(i);

    if (interp_stack_push(i, src, sizeof (*src)))
    {
        LOG("%s: interp_stack_push failed\n", __func__);
        return -1;
    }
    else if (i->fp)
        i->fp->next = dst;

    i->fp = dst;
    return 0;
}

static int check_function_body(FILE *const f, long *const out)
{
    varuint32 body_size;

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

    const long start = ftell(f);

    if (start < 0)
    {
        LOG("%s: ftell(3) start: %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (run(f, 0, NULL))
    {
        LOG("%s: check_local_groups failed\n", __func__);
        return -1;
    }

    const long end = ftell(f);

    if (end < 0)
    {
        LOG("%s: ftell(3) end: %s\n", __func__, strerror(errno));
        return -1;
    }

    const unsigned long consumed = end - start;

    if (consumed > body_size)
    {
        LOG("%s: exceeded function body size\n", __func__);
        return -1;
    }
    else if (check_body(f, body_size - consumed))
    {
        LOG("%s: check_body failed\n", __func__);
        return -1;
    }

    *out = start;
    return 0;
}

int section_code_check(const struct section *const s, struct nw_mod *const m,
    const unsigned long len)
{
    FILE *const f = s->f;

    if (m->sections.code)
    {
        LOG("%s: ignoring duplicate section\n", __func__);
        return fseek(f, len, SEEK_CUR);
    }

    const long start = ftell(f);

    if (start < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (run(f, 0, NULL))
    {
        LOG("%s: run failed\n", __func__);
        return -1;
    }

    const long end = ftell(f);

    if (end < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    const unsigned long size = end - start;

    if (size != len)
    {
        LOG("%s: size exceeded (%lu expected, got %lu)\n",
                __func__, len, size);
        return -1;
    }

    m->sections.code = start;
    return 0;
}

#if 0
static int run(FILE *const f, const varuint32 idx, struct nw_interp *const in)
{
    varuint32 count;

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

    for (varuint32 i = 0; i < count; i++)
    {
        long start;

        if (check_function_body(f, &start))
        {
            LOG("%s: check_function_body failed\n", __func__);
            return -1;
        }
        else if (out && i == idx)
        {
            out->start = start;
            return 0;
        }
    }

    return 0;
}
#endif

int section_code(const struct section *const s, const struct nw_mod *const m,
    const varuint32 idx, struct section_code *const out)
{
    const long offset = m->sections.code;

    if (offset <= 0)
    {
        LOG("%s: code section not found", __func__);
        return -1;
    }
    else if (fseek(s->f, offset, SEEK_SET))
    {
        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    return run(s->f, idx, out);
}

int section_code_push(FILE *const f, struct nw_interp *const i)
{
#if 0
    return run(f, i);
#else
    return run(f, 0, i);
#endif
}