/*
 * nanowasm, a tiny WebAssembly/Wasm interpreter
 * Copyright (C) 2023-2024  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/log.h>
#include <nw/sections.h>
#include <nanowasm/nw.h>
#include <nw/interp.h>
#include <nw/types.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

struct global_type
{
    bool mutable;
    enum value_type type;

    union global_value
    {
        int32_t i32;
        int64_t i64;
        float f32;
        double f64;
    } value;
};

static int get_global(struct nw_interp *const i, void *const dst,
    const size_t n)
{
    if (i->stack_i != n)
    {
        LOG("%s: expected %zu used stack bytes, got %zu\n",
            __func__, i->stack_i, n);
        i->exception = "unexpected stack consumption";
        return -1;
    }

    return interp_global_pop(i, dst, n);
}

static int get_i32(struct nw_interp *const i, union global_value *const value)
{
    return get_global(i, &value->i32, sizeof value->i32);
}

static int get_i64(struct nw_interp *const i, union global_value *const value)
{
    return get_global(i, &value->i64, sizeof value->i64);
}

static int get_f32(struct nw_interp *const i, union global_value *const value)
{
    return get_global(i, &value->f32, sizeof value->f32);
}

static int get_f64(struct nw_interp *const i, union global_value *const value)
{
    return get_global(i, &value->f64, sizeof value->f64);
}

static int get_value(struct nw_interp *const i, const enum value_type type,
    union global_value *const value)
{
    static int (*const get[])(struct nw_interp *, union global_value *) =
    {
        [VALUE_TYPE_I32] = get_i32,
        [VALUE_TYPE_I64] = get_i64,
        [VALUE_TYPE_F32] = get_f32,
        [VALUE_TYPE_F64] = get_f64
    };

    if (get[type](i, value))
    {
        LOG("%s: get failed with type %d\n", __func__, type);
        return -1;
    }

    return 0;
}

static int check_global_type(FILE *const f, struct global_type *const g)
{
    const struct nw_interp_cfg cfg =
    {
        .stack = NW_BUF(sizeof (union global_value))
    };

    struct nw_interp i;
    enum value_type vtype;
    varint7 content_type;
    varuint1 mutability;
    union global_value value;

    if (varint7_read(f, &content_type))
    {
        LOG("%s: varint7_read failed\n", __func__);
        return -1;
    }
    else if (get_value_type(content_type, &vtype))
    {
        LOG("%s: get_value_type failed\n", __func__);
        return -1;
    }
    else if (varuint1_read(f, &mutability))
    {
        LOG("%s: varuint1_read failed\n", __func__);
        return -1;
    }
    else if (interp_start(&cfg, f, &i))
    {
        LOG("%s: interp_start failed\n", __func__);
        return -1;
    }
    else if (interp_run_limited(&i, &interp_initexpr_set))
    {
        LOG("%s: interp_run failed\n", __func__);
        return -1;
    }
    else if (get_value(&i, vtype, &value))
    {
        LOG("%s: get_value failed\n", __func__);
        return -1;
    }

    *g = (const struct global_type)
    {
        .mutable = mutability,
        .type = vtype,
        .value = value
    };

    return 0;
}

static int set_i32(struct nw_interp *const i, void *const dst,
    const struct global_type *const g)
{
    const int32_t value = g->value.i32;

    return interp_global_push(i, &value, sizeof value);
}

static int set_i64(struct nw_interp *const i, void *const dst,
    const struct global_type *const g)
{
    const int64_t value = g->value.i64;

    return interp_global_push(i, &value, sizeof value);
}

static int set_f32(struct nw_interp *const i, void *const dst,
    const struct global_type *const g)
{
    const float value = g->value.f32;

    return interp_global_push(i, &value, sizeof value);
}

static int set_f64(struct nw_interp *const i, void *const dst,
    const struct global_type *const g)
{
    const double value = g->value.f64;

    return interp_global_push(i, &value, sizeof value);
}

static int add_global(struct nw_interp *const i,
    const struct global_type *const g)
{
    const struct nw_gframe f =
    {
        .mutable = g->mutable,
        .type = g->type
    };

    struct nw_gframe *const dst = interp_globalptr(i);;

    if (interp_global_push(i, &f, sizeof f))
    {
        LOG("%s: interp_global_push failed\n", __func__);
        return -1;
    }

    static int (*const set[])(struct nw_interp *, void *,
        const struct global_type *) =
    {
        [VALUE_TYPE_I32] = set_i32,
        [VALUE_TYPE_I64] = set_i64,
        [VALUE_TYPE_F32] = set_f32,
        [VALUE_TYPE_F64] = set_f64
    };

    if (set[g->type](i, dst + 1, g))
    {
        LOG("%s: set failed with type %s\n", __func__,
            value_type_tostr(g->type));
        return -1;
    }

    if (i->gfp)
        i->gfp->next = dst;

    i->gfp = dst;
    return 0;
}

static int check_global_types(FILE *const f,
    struct nw_interp *const in)
{
    varuint32 count;

    if (varuint32_read(f, &count))
    {
        LOG("%s: varuint32_read failed\n", __func__);
        return -1;
    }

    for (varuint32 i = 0; i < count; i++)
    {
        struct global_type g;

        if (check_global_type(f, &g))
        {
            LOG("%s: check_global_type\n", __func__);
            return -1;
        }
        else if (in && add_global(in, &g))
        {
            LOG("%s: add_global failed\n", __func__);
            return -1;
        }
    }

    return 0;
}

static int check(FILE *const f, const unsigned long len)
{
    const long start = ftell(f);

    if (start < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (check_global_types(f, NULL))
    {
        LOG("%s: check_global_types failed\n", __func__);
        return -1;
    }

    const long end = ftell(f);

    if (end < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    const unsigned long size = end - start;

    if (size != len)
    {
        LOG("%s: size exceeded (%lu expected, got %lu)\n",
            __func__, len, size);
        return -1;
    }

    return 0;
}

int section_global_check(const struct section *const s, struct nw_mod *const m,
    const unsigned long len)
{
    FILE *const f = s->f;

    if (m->sections.global)
    {
        LOG("%s: ignoring duplicate section\n", __func__);
        return fseek(f, len, SEEK_CUR);
    }

    const long offset = ftell(f);

    if (offset < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (check(f, len))
    {
        LOG("%s: check failed\n", __func__);
        return -1;
    }

    m->sections.global = offset;
    return 0;
}

int section_global_push(FILE *const f, const struct nw_mod *const m,
    struct nw_interp *const i)
{
    if (fseek(f, m->sections.global, SEEK_SET))
    {
        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (check_global_types(f, i))
    {
        LOG("%s: check_global_types failed\n", __func__);
        return -1;
    }

    return 0;
}