package storage

import (
	"bufio"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sync"
	"time"

	"git.pyer.club/kingecg/gotidb/pkg/model"
)

// Persister 持久化接口
type Persister interface {
	// Write 写入数据
	Write(id model.DataPointID, value model.DataValue) error
	// Close 关闭持久化器
	Close() error
}

// WALEntry WAL日志条目
type WALEntry struct {
	Timestamp  time.Time         `json:"timestamp"`
	DeviceID   string            `json:"device_id"`
	MetricCode string            `json:"metric_code"`
	Labels     map[string]string `json:"labels"`
	Value      interface{}       `json:"value"`
}

// WALPersister WAL持久化器
type WALPersister struct {
	directory string   // WAL日志目录
	file      *os.File // 当前WAL文件
	writer    *bufio.Writer
	mutex     sync.Mutex
	syncEvery int // 每写入多少条数据同步一次
	count     int // 当前写入计数
}

// NewWALPersister 创建一个新的WAL持久化器
func NewWALPersister(directory string, syncEvery int) (*WALPersister, error) {
	// 确保目录存在
	if err := os.MkdirAll(directory, 0755); err != nil {
		return nil, fmt.Errorf("failed to create WAL directory: %v", err)
	}

	// 创建新的WAL文件
	filename := filepath.Join(directory, fmt.Sprintf("wal-%d.wal", time.Now().UnixNano()))
	file, err := os.OpenFile(filename, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		return nil, fmt.Errorf("failed to create WAL file: %v", err)
	}

	return &WALPersister{
		directory: directory,
		file:      file,
		writer:    bufio.NewWriter(file),
		syncEvery: syncEvery,
	}, nil
}

// Write 写入数据到WAL日志
func (w *WALPersister) Write(id model.DataPointID, value model.DataValue) error {
	w.mutex.Lock()
	defer w.mutex.Unlock()

	// 创建WAL条目
	entry := WALEntry{
		Timestamp:  value.Timestamp,
		DeviceID:   id.DeviceID,
		MetricCode: id.MetricCode,
		Labels:     id.Labels,
		Value:      value.Value,
	}

	// 序列化为JSON
	data, err := json.Marshal(entry)
	if err != nil {
		return fmt.Errorf("failed to marshal WAL entry: %v", err)
	}

	// 写入数据
	if _, err := w.writer.Write(data); err != nil {
		return fmt.Errorf("failed to write WAL entry: %v", err)
	}
	if err := w.writer.WriteByte('\n'); err != nil {
		return fmt.Errorf("failed to write newline: %v", err)
	}

	// 增加计数
	w.count++

	// 检查是否需要同步
	if w.count >= w.syncEvery {
		if err := w.sync(); err != nil {
			return fmt.Errorf("failed to sync WAL: %v", err)
		}
		w.count = 0
	}

	return nil
}

// sync 同步WAL日志到磁盘
func (w *WALPersister) sync() error {
	if err := w.writer.Flush(); err != nil {
		return err
	}
	return w.file.Sync()
}

// Close 关闭WAL持久化器
func (w *WALPersister) Close() error {
	w.mutex.Lock()
	defer w.mutex.Unlock()

	// 刷新缓冲区
	if err := w.writer.Flush(); err != nil {
		return fmt.Errorf("failed to flush WAL buffer: %v", err)
	}

	// 同步到磁盘
	if err := w.file.Sync(); err != nil {
		return fmt.Errorf("failed to sync WAL file: %v", err)
	}

	// 关闭文件
	return w.file.Close()
}

// LoadWAL 从WAL日志恢复数据
func LoadWAL(directory string) ([]WALEntry, error) {
	var entries []WALEntry

	// 获取所有WAL文件
	files, err := filepath.Glob(filepath.Join(directory, "wal-*.wal"))
	if err != nil {
		return nil, fmt.Errorf("failed to list WAL files: %v", err)
	}

	// 按文件名排序（文件名包含时间戳）
	// TODO: 实现文件排序

	// 读取每个文件
	for _, file := range files {
		f, err := os.Open(file)
		if err != nil {
			return nil, fmt.Errorf("failed to open WAL file %s: %v", file, err)
		}
		defer f.Close()

		scanner := bufio.NewScanner(f)
		for scanner.Scan() {
			var entry WALEntry
			if err := json.Unmarshal(scanner.Bytes(), &entry); err != nil {
				return nil, fmt.Errorf("failed to unmarshal WAL entry: %v", err)
			}
			entries = append(entries, entry)
		}

		if err := scanner.Err(); err != nil {
			return nil, fmt.Errorf("failed to scan WAL file %s: %v", file, err)
		}
	}

	return entries, nil
}