/*
 * 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>

static enum nw_state seek_code(struct nw_interp *const i)
{
    const struct nw_i_sm_ffn *const f = &i->sm.ffn;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const unsigned long fbo = nwp_leuint32(&f->fbo);
    const enum nw_state n = cfg->seek(fbo, cfg->user);

    if (n)
        return n;

    f->next(i);
    return NW_AGAIN;
}

static enum nw_state get_fbo(struct nw_interp *const i)
{
    struct nw_i_sm_ffn *const f = &i->sm.ffn;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const enum nw_state n = nwp_io_read(cfg, &f->io, cfg->user);

    if (n)
        return n;

    i->next = seek_code;
    return NW_AGAIN;
}

static enum nw_state seek_fbo(struct nw_interp *const i)
{
    struct nw_i_sm_ffn *const f = &i->sm.ffn;
    const struct nw_mod *const m = i->cfg.m;
    long offset = m->c_sections[NW_CUSTOM_FBO];
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    enum nw_state n;

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

#ifdef NW_LOG
        nwp_log("%s\n", exc);
#endif
        i->exception = exc;
        return NW_FATAL;
    }
    else if (f->fn.index < m->import_count)
    {
        static const char *const exc = "invalid function index";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s: %lu\n", exc, (unsigned long)f->fn.index);
#endif
        return NW_FATAL;
    }

    offset += sizeof f->fbo * (f->fn.index - m->import_count);

    if ((n = cfg->seek(offset, cfg->user)))
        return n;
    else
    {
        struct nw_sm_io io = {0};

        io.buf = &f->fbo;
        io.n = sizeof f->fbo;
        f->io = io;
        i->next = get_fbo;
    }

    return NW_AGAIN;
}

void nwp_find_function(struct nw_interp *const i, const struct nw_fn *const fn,
    void (*const next)(struct nw_interp *))
{
    const struct nw_i_sm_ffn f = {0};
    struct nw_i_sm_ffn *const pf = &i->sm.ffn;

    *pf = f;
    pf->fn = *fn;
    pf->next = next;
    i->next = seek_fbo;
}