/*
 * 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 <nw/interp.h>
#include <nw/io.h>
#include <nw/log.h>
#include <nw/ops.h>
#include <nw/routines.h>
#include <nw/stack.h>
#include <nw/types.h>

static enum nw_state get_target(struct nw_interp *const i)
{
    nw_varuint32 target;
    struct nw_i_sm_br_table *const b = &i->sm.br_table;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const enum nw_state n = nwp_varuint32(cfg, &b->leb128, &target, cfg->user);

    if (n)
        return n;
    else if (b->target_i == b->offset
        || (!b->set && b->target_i >= b->target_count))
    {
        b->set = 1;
        b->relative_depth = target;
    }

    if (b->target_i >= b->target_count)
        nwp_break(i, b->relative_depth, b->offset);
    else
        b->target_i++;

    return NW_AGAIN;
}

static enum nw_state pop(struct nw_interp *const i)
{
    struct nw_i_sm_br_table *const b = &i->sm.br_table;
    const enum nw_state n = nwp_stack_pop(i, &b->io);

    if (n)
        return n;

    i->next = get_target;
    return NW_AGAIN;
}

static enum nw_state get_target_count(struct nw_interp *const i)
{
    struct nw_i_sm_br_table *const b = &i->sm.br_table;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const enum nw_state n = nwp_varuint32(cfg, &b->leb128,
        &b->target_count, cfg->user);
    const enum nw_type pt = i->push_type;

    if (n)
        return n;
    else if (pt != NW_TYPE_I32)
    {
        static const char *const exc = "expected i32 expression for br_table";
        const char *const stype = nwp_type_str(pt);

        i->exception = exc;
#ifdef NW_LOG
        if (stype)
            nwp_log("%s, got: %s\n", exc, stype);
        else
            nwp_log("%s, got: unknown (%#x)\n", exc, (unsigned)pt);
#endif
        return NW_FATAL;
    }
    else
    {
        struct nw_sm_io io = {0};

        io.buf = &b->offset;
        io.n = sizeof b->offset;
        b->io = io;
        i->next = pop;
    }

    return NW_AGAIN;
}

void nwp_op_br_table(struct nw_interp *const i)
{
    static const struct nw_i_sm_br_table b;

    i->next = get_target_count;
    i->sm.br_table = b;
}