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

static enum nw_state tell(struct nw_interp *const i)
{
    long offset;
    struct nw_i_sm_b *const b = &i->sm.bytecode;
    static const char *const exc = "invalid opcode";
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const enum nw_state n = cfg->tell(&offset, cfg->user);

    if (n)
        return n;

    offset -= sizeof b->op;

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

static enum nw_state get_bytecode(struct nw_interp *const i)
{
    struct nw_i_sm_b *const b = &i->sm.bytecode;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const enum nw_state n = nwp_io_read(cfg, &b->io, cfg->user);

    if (n)
        return n;
    else if (b->op >= nwp_ops.n || !(b->f = nwp_ops.ops[b->op]))
    {
        i->next = tell;
        return NW_AGAIN;
    }

    i->next = nwp_execute;
    return NW_AGAIN;
}

void nwp_interp_full(struct nw_interp *const i)
{
    struct nw_i_sm_b *const pb = &i->sm.bytecode, b = {0};

    b.io.buf = &pb->op;
    b.io.n = sizeof pb->op;
    *pb = b;
    i->next = get_bytecode;
}