/*
 * 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 execute(struct nw_interp *const i)
{
    struct nw_i_sm_b *const b = &i->sm.bytecode;
    const unsigned char op = b->op;

#ifdef NW_LOG
    nwp_log("opcode: %s, pc=%#lx\n", nwp_op_tostr(op), b->pc);
#endif
    i->fr.op = op;
    b->f(i);
    return NW_AGAIN;
}

static enum nw_state repeat(struct nw_interp *const i)
{
    struct nw_i_sm_b *const b = &i->sm.bytecode;
    struct nw_next *const next = &b->next;
    const enum nw_state n = next->fn(next->user, next);

    if (n == NW_FATAL)
    {
        static const char *const exc = "pc callback failed";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s, pc: %ld\n", exc, b->pc);
#endif
        return NW_FATAL;
    }
    else if (n)
        return n;

    return execute(i);
}

static enum nw_state exec_pc(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 long pc = b->pc;

    if (cfg->pc)
    {
        const enum nw_state n = cfg->pc(pc, &b->next, cfg->user);

        if (n == NW_FATAL)
        {
            static const char *const exc = "pc callback failed";

            i->exception = exc;
#ifdef NW_LOG
            nwp_log("%s, pc: %ld\n", exc, pc);
#endif
            return NW_FATAL;
        }
        else if (n)
        {
            i->next = repeat;
            return n;
        }
    }

    return execute(i);
}

enum nw_state nwp_execute(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 = cfg->tell(&b->pc, cfg->user);

    if (n)
        return n;

    b->pc -= sizeof b->op;
    i->next = exec_pc;
    return NW_AGAIN;
}