/*
 * 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/routines.h>

static enum nw_state get_pc(struct nw_interp *);

static enum nw_state seek_dst(struct nw_interp *const i)
{
    const struct nw_i_sm_break *const b = &i->sm.brk;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const unsigned long dst = nwp_leuint32(&b->dst);
    const enum nw_state n = cfg->seek(dst, cfg->user);

    if (n)
        return n;

    nwp_interp_resume(i);
    return NW_AGAIN;
}

static enum nw_state skip(struct nw_interp *const i)
{
    struct nw_i_sm_break *const b = &i->sm.brk;
    const unsigned long n_labels = nwp_leuint32(&b->n);

    if (++b->label_i >= n_labels)
    {
        static const char *const exc = "no label found";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s, offset: %#lx\n", exc, b->pc);
#endif
        return NW_FATAL;
    }
    else
    {
        struct nw_sm_io io = {0};

        io.buf = &b->lpc;
        io.n = sizeof b->lpc;
        b->io = io;
        i->next = get_pc;
    }

    return NW_AGAIN;
}

static enum nw_state get_dst(struct nw_interp *const i)
{
    struct nw_i_sm_break *const b = &i->sm.brk;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const unsigned long pc = nwp_leuint32(&b->lpc);
    const enum nw_state n = nwp_io_read(cfg, &b->io, cfg->user);

    if (n)
        return n;
    else if (pc == b->pc && b->toffset_i++ >= b->table_offset)
        i->next = seek_dst;
    else
        return skip(i);

    return NW_AGAIN;
}

static enum nw_state get_pc(struct nw_interp *const i)
{
    struct nw_i_sm_break *const b = &i->sm.brk;
    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
    {
        struct nw_sm_io io = {0};

        io.buf = &b->dst;
        io.n = sizeof b->dst;
        b->io = io;
        i->next = get_dst;
    }

    return NW_AGAIN;
}

static enum nw_state get_n(struct nw_interp *const i)
{
    struct nw_i_sm_break *const b = &i->sm.brk;
    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 (!nwp_leuint32(&b->n))
    {
        static const char *const exc = "function has no labels";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s\n", exc);
#endif
        return NW_FATAL;
    }
    else
    {
        struct nw_sm_io io = {0};

        io.buf = &b->lpc;
        io.n = sizeof b->lpc;
        b->io = io;
    }

    i->next = get_pc;
    return NW_AGAIN;
}

static enum nw_state seek_start(struct nw_interp *const i)
{
    struct nw_i_sm_break *const b = &i->sm.brk;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const unsigned long offset = nwp_leuint32(&b->offset);
    const enum nw_state n = cfg->seek(offset, cfg->user);

    if (n)
        return n;
    else
    {
        struct nw_sm_io io = {0};

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

    return NW_AGAIN;
}

static enum nw_state get_start(struct nw_interp *const i)
{
    struct nw_i_sm_break *const b = &i->sm.brk;
    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;

    i->next = seek_start;
    return NW_AGAIN;
}

static enum nw_state seek_lo(struct nw_interp *const i)
{
    const struct nw_mod *const m = i->cfg.m;
    struct nw_i_sm_break *const b = &i->sm.brk;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    long offset = m->c_sections[NW_CUSTOM_LO];
    enum nw_state n;

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

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s\n", exc);
#endif
        return NW_FATAL;
    }
    else if (i->fr.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)i->fr.fn.index);
#endif
        return NW_FATAL;
    }

    offset += sizeof b->offset * (i->fr.fn.index - m->import_count);

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

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

    return NW_AGAIN;
}

static enum nw_state tell(struct nw_interp *const i)
{
    struct nw_i_sm_break *const b = &i->sm.brk;
    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;
    else if (i->fr.block_i < b->relative_depth)
    {
        static const char *const exc = "relative depth exceeds block level";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s, rdepth: %lu, blvl: %lu\n", exc,
            (unsigned long)i->fr.block_i, (unsigned long)b->relative_depth);
#endif
        return NW_FATAL;
    }

    i->fr.block_i -= b->relative_depth;
    i->next = seek_lo;
    return NW_AGAIN;
}

void nwp_break(struct nw_interp *const i, const nw_varuint32 relative_depth,
    const nw_varuint32 table_offset)
{
    const struct nw_i_sm_break b = {0};
    struct nw_i_sm_break *const pb = &i->sm.brk;

    *pb = b;
    pb->relative_depth = relative_depth;
    pb->table_offset = table_offset;
    i->next = tell;
}