package snowflake

import (
    "sync"
    "time"
)

type Generator interface {
    // NextID 生成一个唯一ID
    NextID() int64
}

const sleepDuration = 200 * time.Millisecond

var (
    mutex             sync.Mutex
    snowflakeInstance Generator
)

func GetDefaultInstance() Generator {
    if snowflakeInstance == nil {
        mutex.Lock()
        snowflakeInstance = NewSnowWorkerOffset(nil)
        time.Sleep(sleepDuration)
        mutex.Unlock()
    }
    return snowflakeInstance
}

func SetSnowflake(options *Options) {
    snowflakeInstance = NewSnowflake(options)
}

func NewSnowflake(options *Options) Generator {
    mutex.Lock()
    defer mutex.Unlock()

    var snowflakeInstance Generator

    switch options.Method {
    case MethodSnowflakeOffset:
        snowflakeInstance = NewSnowWorkerOffset(options)
        time.Sleep(sleepDuration)
    case MethodSnowflake:
        fallthrough
    default:
        snowflakeInstance = NewSnowWorker(options)
    }

    return snowflakeInstance
}