/*
 * nanowasm, a tiny WebAssembly/Wasm interpreter
 * Copyright (C) 2023-2025  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 <nanowasm/nw.h>
#include <nanowasm/types.h>
#include <nw/interp.h>
#include <nw/io.h>
#include <nw/log.h>
#include <nw/routines.h>
#include <string.h>

static enum nw_state entry_loop(struct nw_interp *i);

static enum nw_state get_index(struct nw_interp *const i)
{
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    struct nw_i_sm_exp *const e = &i->sm.export;
    struct nw_sm_leb128 *const l = &e->leb128;
    const enum nw_state n = nwp_varuint32(cfg, l, &e->index, cfg->user);

    if (n)
        return n;

    i->next = e->next;
    return NW_AGAIN;
}

static enum nw_state get_kind(struct nw_interp *const i)
{
    unsigned char kind;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    struct nw_i_sm_exp *const e = &i->sm.export;
    struct nw_sm_io io = {0};
    enum nw_state n;

    io.buf = &kind;
    io.n = sizeof kind;

    if ((n = nwp_io_read(cfg, &io, cfg->user)))
        return n;
    else if (kind >= NW_KINDS)
    {
        static const char *const exc = "invalid export kind";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s: %#x\n", exc, (unsigned)kind);
#endif
        return NW_FATAL;
    }

    e->kind = kind;
    i->next = get_index;
    return NW_AGAIN;
}

static enum nw_state skip_index(struct nw_interp *const i)
{
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    struct nw_i_sm_exp *const e = &i->sm.export;
    struct nw_sm_leb128 *const l = &e->leb128;
    nw_varuint32 index;
    const enum nw_state n = nwp_varuint32(cfg, l, &index, cfg->user);

    if (n)
        return n;

    e->entry_i++;
    i->next = entry_loop;
    return NW_AGAIN;
}

static enum nw_state skip_kind(struct nw_interp *const i)
{
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    unsigned char b;
    struct nw_sm_io io = {0};
    enum nw_state n;

    io.buf = &b;
    io.n = sizeof b;

    if ((n = nwp_io_read(cfg, &io, cfg->user)))
        return n;

    i->next = skip_index;
    return NW_AGAIN;
}

static enum nw_state skip_field_str(struct nw_interp *const i)
{
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const struct nw_i_sm_exp *const e = &i->sm.export;
    const long offset = e->offset + (e->len - e->len_i);
    const enum nw_state n = cfg->seek(offset, cfg->user);

    if (n)
        return n;

    i->next = skip_kind;
    return NW_AGAIN;
}

static enum nw_state tell(struct nw_interp *const i)
{
    struct nw_i_sm_exp *const e = &i->sm.export;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const enum nw_state n = cfg->tell(&e->offset, cfg->user);

    if (n)
        return n;

    i->next = skip_field_str;
    return NW_AGAIN;
}

static enum nw_state compare(struct nw_interp *const i)
{
    unsigned char b;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    struct nw_i_sm_exp *const e = &i->sm.export;
    struct nw_sm_io io = {0};
    enum nw_state n;

    io.buf = &b;
    io.n = sizeof b;

    if ((n = nwp_io_read(cfg, &io, cfg->user)))
        return n;
    else if (b != e->sym[e->len_i++])
        i->next = tell;
    else if (e->len_i >= e->len)
        i->next = get_kind;

    return NW_AGAIN;
}

static enum nw_state get_len(struct nw_interp *const i)
{
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    struct nw_i_sm_exp *const e = &i->sm.export;
    struct nw_sm_leb128 *const l = &e->leb128;
    const enum nw_state n = nwp_varuint32(cfg, l, &e->len, cfg->user);

    if (n)
        return n;
    else if (e->len != strlen(e->sym))
        i->next = skip_field_str;
    else
        i->next = compare;

    return NW_AGAIN;
}

static enum nw_state entry_loop(struct nw_interp *const i)
{
    struct nw_i_sm_exp *const e = &i->sm.export;

    if (e->entry_i >= e->count)
    {
        static const char *const exc = "failed to find symbol";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s: %s\n", exc, e->sym);
#endif
        return NW_FATAL;
    }

    e->len_i = 0;
    i->next = get_len;
    return NW_AGAIN;
}

static enum nw_state get_count(struct nw_interp *const i)
{
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    struct nw_i_sm_exp *const e = &i->sm.export;
    struct nw_sm_leb128 *const l = &e->leb128;
    const enum nw_state n = nwp_varuint32(cfg, l, &e->count, cfg->user);

    if (n)
        return n;

    i->next = entry_loop;
    return NW_AGAIN;
}

static enum nw_state seek(struct nw_interp *const i)
{
    const struct nw_mod *const m = i->cfg.m;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const long offset = m->sections[NW_SECTION_EXPORT];
    enum nw_state n;

    if (!offset)
    {
        static const char *const exc = "section not found";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s: %s\n", exc, "export");
#endif
        return NW_FATAL;
    }
    else if ((n = cfg->seek(offset, cfg->user)))
        return n;

    i->next = get_count;
    return NW_AGAIN;
}

void nwp_find_export(struct nw_interp *const i, const char *const sym,
    enum nw_state (*const next)(struct nw_interp *))
{
    const struct nw_i_sm_exp e = {0};
    struct nw_i_sm_exp *const pe = &i->sm.export;

    *pe = e;
    pe->sym = sym;
    pe->next = next;
    i->next = seek;
}