#include <assert.h>
#include <stdio.h>
#include <stdbool.h>
#include <string.h>

#include "apfl.h"

static bool
file_read(void *opaque, unsigned char *buf, size_t *len)
{
    FILE *f = opaque;

    size_t maxlen = *len;
    *len = fread(buf, 1, maxlen, f);
    if (*len == 0) {
        return feof(f);
    }

    return true;
}

struct apfl_io_reader
apfl_io_file_reader(FILE *f)
{
    return (struct apfl_io_reader) {
        .read = file_read,
        .opaque = f,
    };
}

static bool
string_reader_callback(void *opaque, unsigned char *buf, size_t *len)
{
    struct apfl_io_string_reader_data *ctx = opaque;

    size_t maxlen = *len;
    size_t remain_len = ctx->sv.len - ctx->off;
    *len = maxlen < remain_len ? maxlen : remain_len;
    memcpy(buf, ctx->sv.bytes + ctx->off, *len);
    ctx->off += *len;
    assert(ctx->off <= ctx->sv.len);

    return true;
}

struct apfl_io_string_reader_data
apfl_io_string_reader_create(struct apfl_string_view sv)
{
    return (struct apfl_io_string_reader_data) {
        .sv = sv,
        .off = 0,
    };
}

struct apfl_io_reader apfl_io_string_reader(struct apfl_io_string_reader_data *data)
{
    return (struct apfl_io_reader) {
        .read = string_reader_callback,
        .opaque = data,
    };
}

bool
apfl_io_read_bytes(struct apfl_io_reader r, unsigned char *buf, size_t *len)
{
    return r.read(r.opaque, buf, len);
}

bool
apfl_io_read_bytes_exact_size(struct apfl_io_reader r, unsigned char *buf, size_t want)
{
    while (want > 0) {
        size_t have = want;
        if (!apfl_io_read_bytes(r, buf, &have)) {
            return false;
        }
        if (have == 0) {
            return false;
        }
        want -= have;
        buf += have;
    }

    return true;
}

bool
apfl_io_read_byte(struct apfl_io_reader r, unsigned char *byte)
{
    return apfl_io_read_bytes_exact_size(r, byte, 1);
}