/*
 * 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/log.h>
#include <nw/routines.h>
#include <nw/stack.h>
#include <nw/types.h>
#include <limits.h>

static enum nw_state read_meta(struct nw_interp *const i)
{
    struct nw_find_local *const f = i->state;
    const struct nw_local_meta *const m = &f->meta;
    const nw_varuint32 index = f->index - f->entry_i;
    const enum nw_state n = nwp_stack_read(i, &f->io, f->addr);
    size_t sz;
    nw_varuint32 count;

    if (n)
        return n;

    f->addr += sizeof f->meta;
    count = m->entry_count;

    if (nwp_type_sz(m->type, &sz))
    {
        static const char *const exc = "invalid type";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s: %#x\n", exc, (unsigned)m->type);
#endif
        return NW_FATAL;
    }
    else if (index < count)
    {
        const size_t offset = sz * index;

        if (f->addr > ULONG_MAX - offset)
        {
            static const char *const exc = "out-of-bounds access to local";

            i->exception = exc;
#ifdef NW_LOG
            nwp_log("%s: addr: %lu, offset: %lu\n", exc,
                (unsigned long)f->addr, (unsigned long)offset);
#endif
            return NW_FATAL;
        }
        else if ((f->addr += offset) >= i->fr.local_end)
        {
            static const char *const exc = "invalid local index";

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

        i->next = f->next;
    }
    else
    {
        const size_t offset = sz * count;

        f->entry_i += count;

        if (f->addr > ULONG_MAX - offset)
        {
            static const char *const exc = "out-of-bounds access to local";

            i->exception = exc;
#ifdef NW_LOG
            nwp_log("%s: addr: %lu, offset: %lu\n", exc,
                (unsigned long)f->addr, (unsigned long)offset);
#endif
            return NW_FATAL;
        }
        else if ((f->addr += offset) >= i->fr.local_end)
        {
            static const char *const exc = "invalid local index";

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

            io.buf = &f->meta;
            io.n = sizeof f->meta;
            f->io = io;
        }
    }

    return NW_AGAIN;
}

void nwp_find_local(struct nw_interp *const i, struct nw_find_local *const f,
    const nw_varuint32 index, enum nw_state (*const next)(struct nw_interp *),
    void *const args)
{
    const struct nw_find_local fl = {0};

    *f = fl;
    f->index = index;
    f->next = next;
    f->addr = i->fr.local_start;
    f->io.buf = &f->meta;
    f->io.n = sizeof f->meta;
    i->state = f;
    i->args = args;
    i->next = read_meta;
}