#include <sections.h>
#include <interp.h>
#include <wasm_types.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

struct global_type
{
    varint7 value_type;
    varuint1 mutability;
};

static int check_global_type(FILE *const f, struct global_type *const g)
{
    if (varint7_read(f, &g->value_type))
    {
        fprintf(stderr, "%s: varint7_read failed\n", __func__);
        return -1;
    }
    else if (varuint1_read(f, &g->mutability))
    {
        fprintf(stderr, "%s: varuint1_read failed\n", __func__);
        return -1;
    }

    return 0;
}

static int check(FILE *const f, const unsigned long len)
{
    int ret = -1;
    struct global_type g;
    struct interp *i = NULL;
    const long start = ftell(f);
    const struct interp_cfg cfg =
    {
        .f = f
    };

    if (start < 0)
    {
        fprintf(stderr, "%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (check_global_type(f, &g))
    {
        fprintf(stderr, "%s: check_global_type\n", __func__);
        goto end;
    }
    else if (!(i = interp_alloc(&cfg)))
    {
        fprintf(stderr, "%s: interp_alloc failed\n", __func__);
        goto end;
    }
    else if (interp_run_limited(i, &interp_initexpr_set))
    {
        fprintf(stderr, "%s: interp_run failed\n", __func__);
        goto end;
    }

    const long end = ftell(f);

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

    const unsigned long size = end - start;

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

    ret = 0;

end:
    interp_free(i);
    return ret;
}

int section_global(struct wasmfs *const w, FILE *const f,
    const unsigned long len)
{
    if (w->sections.global)
    {
        fprintf(stderr, "%s: ignoring duplicate section\n", __func__);
        return 0;
    }

    const long offset = ftell(f);

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

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