/*
 * 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 <nanowasm/types.h>
#include <nw/linear.h>
#include <nw/interp.h>
#include <nw/io.h>
#include <nw/log.h>
#include <nw/routines.h>
#include <nw/stack.h>
#include <nw/types.h>

static enum nw_state get_index(struct nw_inst *);
static enum nw_state get_byte(struct nw_inst *);

static enum nw_state store_byte(struct nw_inst *const inst)
{
    struct nw_inst_sm_d *const d = &inst->sm.data;
    struct nw_interp *const i = &inst->interp;
    const unsigned long offset = d->offset + d->bytes_i;
    const enum nw_state n = nwp_linear_store(i, &d->io, offset);

    if (n)
        return n;
    else if (++d->bytes_i >= d->size)
        inst->next = ++d->entry_i >= d->count ? d->next : get_index;
    else
        inst->next = get_byte;

    return NW_AGAIN;
}

static enum nw_state get_byte(struct nw_inst *const inst)
{
    struct nw_inst_sm_d *const d = &inst->sm.data;
    struct nw_interp *const i = &inst->interp;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    struct nw_sm_io io = {0};
    enum nw_state n;

    io.buf = &d->b;
    io.n = sizeof d->b;

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

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

    inst->next = store_byte;
    return NW_AGAIN;
}

static enum nw_state get_size(struct nw_inst *const inst)
{
    struct nw_inst_sm_d *const d = &inst->sm.data;
    struct nw_sm_leb128 *const l = &d->leb128;
    struct nw_interp *const i = &inst->interp;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const enum nw_state n = nwp_varuint32(cfg, l, &d->size, cfg->user);

    if (n)
        return n;

    d->bytes_i = 0;
    inst->next = get_byte;
    return NW_AGAIN;
}

static enum nw_state pop(struct nw_inst *const inst)
{
    struct nw_inst_sm_d *const d = &inst->sm.data;
    const enum nw_state n = nwp_stack_pop(&inst->interp, &d->io);

    if (n)
        return n;

    inst->next = get_size;
    return NW_AGAIN;
}

static enum nw_state loop(struct nw_inst *const inst)
{
    struct nw_inst_sm_d *const d = &inst->sm.data;
    const enum nw_state n = nwp_interp_run(&inst->interp);
    struct nw_sm_io io = {0};

    if (n)
        return n;

    io.buf = &d->offset;
    io.n = sizeof d->offset;
    d->io = io;
    inst->next = pop;
    return NW_AGAIN;
}

static enum nw_state setup_initexpr(struct nw_inst *const inst)
{
    struct nw_interp *const i = &inst->interp;
    const struct nw_interp_cfg icfg = i->cfg;

    if (nwp_interp_start(i, &icfg, &nwp_interp_data_set))
    {
#ifdef NW_LOG
        nwp_log("nw_interp_start failed\n");
#endif
        return NW_FATAL;
    }

    inst->next = loop;
    return NW_AGAIN;
}

static enum nw_state get_index(struct nw_inst *const inst)
{
    struct nw_inst_sm_d *const d = &inst->sm.data;
    struct nw_sm_leb128 *const l = &d->leb128;
    struct nw_interp *const i = &inst->interp;
    const struct nw_io_cfg *const cfg = &i->cfg.io;
    const enum nw_state n = nwp_varuint32(cfg, l, &d->index, cfg->user);

    if (n)
        return n;

    return setup_initexpr(inst);
}

static enum nw_state get_count(struct nw_inst *const i)
{
    struct nw_inst_sm_d *const d = &i->sm.data;
    struct nw_sm_leb128 *const l = &d->leb128;
    const struct nw_interp_cfg *const icfg = &i->interp.cfg;
    const struct nw_io_cfg *const cfg = &icfg->io;
    const nw_varuint32 expected = icfg->m->data_count;
    const enum nw_state n = nwp_varuint32(cfg, l, &d->count, cfg->user);

    if (n)
        return n;
    else if (d->count != expected)
    {
#ifdef NW_LOG
        static const char *const exc = "data count mismatch";

        nwp_log("%s, expected %lu, got %lu\n", exc,
            (unsigned long)expected, (unsigned long)d->count);
#endif
        return NW_FATAL;
    }

    i->next = d->count ? get_index : d->next;
    return NW_AGAIN;
}

static enum nw_state seek_data(struct nw_inst *const i)
{
    struct nw_inst_sm_gl *const d = &i->sm.global;
    const struct nw_interp_cfg *const icfg = &i->interp.cfg;
    const struct nw_io_cfg *const cfg = &icfg->io;
    const long offset = icfg->m->sections[NW_SECTION_DATA];
    enum nw_state n;

    if (!offset)
    {
        i->next = d->next;
        return NW_AGAIN;
    }
    else if ((n = cfg->seek(offset, cfg->user)))
        return n;

    i->next = get_count;
    return NW_AGAIN;
}

void nwp_init_data(struct nw_inst *const i,
    enum nw_state (*const next)(struct nw_inst *))
{
    const struct nw_inst_sm_d d = {0};
    struct nw_inst_sm_d *const p = &i->sm.data;

    *p = d;
    p->next = next;
    i->next = seek_data;
}