package storage

import (
	"encoding/json"
	"os"
	"sync"

	"github.com/go-mysql-org/go-mysql/mysql"
	"github.com/go-redis/redis/v8"
)

type PositionStorage interface {
	Save(position mysql.Position) error
	Load() (mysql.Position, error)
}

// 文件存储
type FileStorage struct {
	filePath string
	mutex    sync.RWMutex
}

// NewFileStorage 创建一个新的文件存储实例
// 1. filePath: 位置信息存储的文件路径
func NewFileStorage(filePath string) *FileStorage {
	return &FileStorage{filePath: filePath}
}

func (fs *FileStorage) Save(pos mysql.Position) error {
	fs.mutex.Lock()
	defer fs.mutex.Unlock()

	data, err := json.Marshal(pos)
	if err != nil {
		return err
	}

	return os.WriteFile(fs.filePath, data, 0644)
}

// Load 从文件加载位置信息
// 1. 如果文件不存在，返回空位置
// 2. 如果文件存在，解析JSON数据
func (fs *FileStorage) Load() (mysql.Position, error) {
	fs.mutex.RLock()
	defer fs.mutex.RUnlock()

	data, err := os.ReadFile(fs.filePath)
	if err != nil {
		if os.IsNotExist(err) {
			return mysql.Position{}, nil
		}
		return mysql.Position{}, err
	}

	var pos mysql.Position
	err = json.Unmarshal(data, &pos)
	return pos, err
}

// Redis存储
type RedisStorage struct {
	client *redis.Client
	key    string
}

func NewRedisStorage(redisURL, key string) (*RedisStorage, error) {
	opt, err := redis.ParseURL(redisURL)
	if err != nil {
		return nil, err
	}

	client := redis.NewClient(opt)
	return &RedisStorage{client: client, key: key}, nil
}

func (rs *RedisStorage) Save(pos mysql.Position) error {
	data, err := json.Marshal(pos)
	if err != nil {
		return err
	}

	return rs.client.Set(rs.client.Context(), rs.key, data, 0).Err()
}

func (rs *RedisStorage) Load() (mysql.Position, error) {
	data, err := rs.client.Get(rs.client.Context(), rs.key).Bytes()
	if err == redis.Nil {
		return mysql.Position{}, nil
	}
	if err != nil {
		return mysql.Position{}, err
	}

	var pos mysql.Position
	err = json.Unmarshal(data, &pos)
	return pos, err
}