/*
 * 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/stack.h>
#include <nw/types.h>

static enum nw_state pop(struct nw_interp *const i)
{
    struct nw_i_sm_drop *const d = &i->sm.drop;
    const enum nw_state n = nwp_stack_pop(i, &d->io);

    if (n)
        return n;

    nwp_interp_resume(i);
    return NW_AGAIN;
}

static enum nw_state check(struct nw_interp *const i)
{
    struct nw_i_sm_drop *const d = &i->sm.drop;
    const struct nw_frame *const fr = &i->fr;
    const struct nw_return *const r = &fr->prev_ret;
    const unsigned char prev = fr->prev_op;
    size_t sz;

    if (prev != OP_CALL && prev != OP_CALL_INDIRECT)
    {
        static const char *const exc =
            "expected call or call_indirect before drop";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s, got: %#x\n", exc, (unsigned)prev);
#endif
        return NW_FATAL;
    }
    else if (!r->count)
    {
        static const char *const exc =
            "called drop from function without return value";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s\n", exc);
#endif
        return NW_FATAL;
    }
    else if (r->type != i->push_type)
    {
        static const char *const exc =
            "mismatch between return type and last push type";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s, expected: %#hhx, got: %#hhx\n", exc,
            (unsigned char)i->push_type, (unsigned char)r->type);
#endif
        return NW_FATAL;
    }
    else if (nwp_type_sz(r->type, &sz))
    {
        static const char *const exc = "invalid return type";

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

        io.buf = &d->value;
        io.n = sz;
        d->io = io;
        i->next = pop;
    }

    return NW_AGAIN;
}

void nwp_op_drop(struct nw_interp *const i)
{
    const struct nw_i_sm_drop d = {{0}};

    i->sm.drop = d;
    i->next = check;
}