#include "ogg_demux.h"

static uint32_t le32(const uint8_t* p)
{
    return (uint32_t)p[0]
         | ((uint32_t)p[1] << 8)
         | ((uint32_t)p[2] << 16)
         | ((uint32_t)p[3] << 24);
}

int ogg_parse_page(const uint8_t* buf, int buf_len, ogg_page_t* page)
{
    if (buf_len < 27)
        return -1;

    /* 校验 "OggS" */
    if (buf[0] != 'O' || buf[1] != 'g' || buf[2] != 'g' || buf[3] != 'S')
        return -2;

    /* 拷贝页头 */
    for (int i = 0; i < 27; ++i)
        page->header[i] = buf[i];

    page->seg_count = buf[26];

    if (buf_len < 27 + page->seg_count)
        return -3;

    /* 读取 segment table */
    for (int i = 0; i < page->seg_count; ++i)
        page->seg_table[i] = buf[27 + i];

    /* 计算 body 大小 */
    uint32_t body_size = 0;
    for (int i = 0; i < page->seg_count; ++i)
        body_size += page->seg_table[i];

    page->body_size = body_size;

    if (buf_len < 27 + page->seg_count + body_size)
        return -4;

    return (int)body_size;
}

int ogg_extract_packet(const uint8_t* body, const ogg_page_t* page,
                       uint8_t* packet, int packet_buf_size)
{
    /* 极简版：假设一个页里只有一个完整 packet（常见于 OpusHead / OpusTags） */
    uint32_t total = page->body_size;
    if (total > (uint32_t)packet_buf_size)
        return -1;

    for (uint32_t i = 0; i < total; ++i)
        packet[i] = body[i];

    return (int)total;
}