#include <time.h>
#include <string.h>

#include "log.h"
#include "utils.h"
#include "stellar.h"
#include "snowflake.h"

#define snowflake_LOG_ERROR(format, ...) LOG_ERROR("snowflake", format, ##__VA_ARGS__)
#define snowflake_LOG_DEBUG(format, ...) LOG_DEBUG("snowflake", format, ##__VA_ARGS__)

struct snowflake
{
    uint8_t snowflake_base;   // 5bit  [0, 31]
    uint8_t snowflake_offset; // 7bit  [0, 127]
    uint64_t device_id;       // 12bit [0, 4095] ( base << 7 | offset )
    uint64_t thread[MAX_THREAD_NUM];
};

struct snowflake g_snowflake = {};

// return  0: success
// return -1: failed
int snowflake_id_init(const struct snowflake_options *opts)
{
    memset(&g_snowflake, 0, sizeof(struct snowflake));

    if (opts == NULL)
    {
        snowflake_LOG_ERROR("opts is NULL");
        return -1;
    }

    if (opts->snowflake_base > 31)
    {
        snowflake_LOG_ERROR("snowflake_base %u is invalid, range [0, 31]", opts->snowflake_base);
        return -1;
    }

    if (opts->snowflake_offset > 127)
    {
        snowflake_LOG_ERROR("snowflake_offset %u is invalid, range [0, 127]", opts->snowflake_offset);
        return -1;
    }

    g_snowflake.snowflake_base = opts->snowflake_base;
    g_snowflake.snowflake_offset = opts->snowflake_offset;
    g_snowflake.device_id = ((g_snowflake.snowflake_base << 7) | g_snowflake.snowflake_offset) & 0xFFF;

    snowflake_LOG_DEBUG("snowflake_base: %u, snowflake_offset: %u, device_id: %u",
                        g_snowflake.snowflake_base,
                        g_snowflake.snowflake_offset,
                        g_snowflake.device_id);
    return 0;
}

/*
 * high -> low
 *
 * +------+------------------+----------------+------------------------+---------------------------+
 * | 1bit |  12bit device_id | 8bit thread_id | 28bit timestamp in sec | 15bit sequence per thread |
 * +------+------------------+----------------+------------------------+---------------------------+
 */
uint64_t snowflake_id_generate(uint64_t now_sec)
{
#define MAX_ID_PER_THREAD (32768)
#define MAX_ID_BASE_TIME (268435456L)

    uint64_t thr_idx = (uint16_t)stellar_get_current_thread_index();

    uint64_t global_id = 0;
    uint64_t id_per_thread = (g_snowflake.thread[thr_idx]++) % MAX_ID_PER_THREAD;
    uint64_t id_base_time = now_sec % MAX_ID_BASE_TIME;
    global_id = (g_snowflake.device_id << 51) |
                (thr_idx << 43) |
                (id_base_time << 15) |
                (id_per_thread);

    return global_id;
}