package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/go-mysql-org/go-mysql/mysql"
	"github.com/go-mysql-org/go-mysql/replication"
)

// SQLWriter 用于异步输出SQL语句
type SQLWriter struct {
	sqlCh chan string
}

func NewSQLWriter() *SQLWriter {
	return &SQLWriter{
		sqlCh: make(chan string, 1000), // 缓冲通道
	}
}

// Start 启动异步SQL写入器
func (w *SQLWriter) Start() {
	go func() {
		for sql := range w.sqlCh {
			// 这里可以替换为实际写入文件、发送到消息队列等操作
			fmt.Printf("[%s] %s\n", time.Now().Format("2006-01-02 15:04:05"), sql)
		}
	}()
}

// Write 异步写入SQL
func (w *SQLWriter) Write(sql string) {
	select {
	case w.sqlCh <- sql:
		// 成功写入通道
	default:
		log.Println("警告: SQL通道拥堵，丢弃SQL语句:", sql)
	}
}

// Stop 停止写入器
func (w *SQLWriter) Stop() {
	close(w.sqlCh)
}

type PositionManager struct {
	filePath string
}

func (pm *PositionManager) Save(pos mysql.Position) error {
	data, _ := json.Marshal(pos)
	return os.WriteFile(pm.filePath, data, 0644)
}

func (pm *PositionManager) Load() (mysql.Position, error) {
	data, err := os.ReadFile(pm.filePath)
	if err != nil {
		return mysql.Position{}, err
	}

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

// 程序启动参数
var user = flag.String("user", "root", "MySQL user, must have replication privilege")
var password = flag.String("password", "****", "MySQL password")

// 从 arg参数中获取配置信息
func main() {
	flag.Parse()

	// 创建SQL写入器
	sqlWriter := NewSQLWriter()
	sqlWriter.Start()
	defer sqlWriter.Stop()

	// 配置Binlog同步器
	cfg := replication.BinlogSyncerConfig{
		ServerID: 100, // 唯一的ServerID
		Flavor:   "mysql",
		Host:     "localhost",
		Port:     3306,
		User:     *user,
		Password: *password,
		Charset:  "utf8mb4",
	}

	syncer := replication.NewBinlogSyncer(cfg)
	defer syncer.Close()

	// 获取当前Binlog位置（可选）
	// 也可以从指定的位置开始，如 mysql.Position{Name: "mysql-bin.000001", Pos: 4}
	position := mysql.Position{Name: "", Pos: 4}

	streamer, err := syncer.StartSync(position)
	if err != nil {
		log.Fatalf("Failed to start sync: %v", err)
	}

	log.Println("开始监听MySQL Binlog...")

	// 处理优雅退出
	signalCh := make(chan os.Signal, 1)
	signal.Notify(signalCh, syscall.SIGINT, syscall.SIGTERM)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	// 启动事件处理循环
	go eventLoop(ctx, streamer, sqlWriter)

	<-signalCh
	log.Println("收到退出信号，停止监听...")
}

// 事件处理循环
func eventLoop(ctx context.Context, streamer *replication.BinlogStreamer, writer *SQLWriter) {
	for {
		select {
		case <-ctx.Done():
			return
		default:
			ev, err := streamer.GetEvent(ctx)
			if err != nil {
				if err == context.Canceled {
					return
				}
				log.Printf("获取Binlog事件错误: %v", err)
				continue
			}

			// 解析Binlog事件
			if err := parseBinlogEvent(ev, writer); err != nil {
				log.Printf("解析Binlog事件错误: %v", err)
			}
		}
	}
}

// 解析Binlog事件并生成SQL语句
func parseBinlogEvent(ev *replication.BinlogEvent, writer *SQLWriter) error {
	event := ev.Header.EventType

	switch event {
	case replication.WRITE_ROWS_EVENTv1, replication.WRITE_ROWS_EVENTv2:
		return handleWriteRows(ev, writer)
	case replication.DELETE_ROWS_EVENTv1, replication.DELETE_ROWS_EVENTv2:
		return handleDeleteRows(ev, writer)
	case replication.UPDATE_ROWS_EVENTv1, replication.UPDATE_ROWS_EVENTv2:
		return handleUpdateRows(ev, writer)
	case replication.QUERY_EVENT:
		return handleQueryEvent(ev, writer)
	}

	return nil
}

// 处理INSERT事件
func handleWriteRows(ev *replication.BinlogEvent, writer *SQLWriter) error {
	rowsEvent, ok := ev.Event.(*replication.RowsEvent)
	if !ok {
		return fmt.Errorf("类型断言失败: 期望*replication.RowsEvent")
	}

	tableName := string(rowsEvent.Table.Table)
	schemaName := string(rowsEvent.Table.Schema)

	for _, row := range rowsEvent.Rows {
		columns := make([]string, len(row))
		values := make([]interface{}, len(row))

		for i, value := range row {
			columns[i] = fmt.Sprintf("column%d", i)
			values[i] = value
		}

		sql := generateInsertSQL(schemaName, tableName, columns, values)
		writer.Write(sql)
	}

	return nil
}

// 处理DELETE事件
func handleDeleteRows(ev *replication.BinlogEvent, writer *SQLWriter) error {
	rowsEvent, ok := ev.Event.(*replication.RowsEvent)
	if !ok {
		return fmt.Errorf("类型断言失败: 期望*replication.RowsEvent")
	}

	tableName := string(rowsEvent.Table.Table)
	schemaName := string(rowsEvent.Table.Schema)

	for _, row := range rowsEvent.Rows {
		whereClause := generateWhereClause(row)
		sql := fmt.Sprintf("DELETE FROM `%s`.`%s` WHERE %s", schemaName, tableName, whereClause)
		writer.Write(sql)
	}

	return nil
}

// 处理UPDATE事件
func handleUpdateRows(ev *replication.BinlogEvent, writer *SQLWriter) error {
	rowsEvent, ok := ev.Event.(*replication.RowsEvent)
	if !ok {
		return fmt.Errorf("类型断言失败: 期望*replication.RowsEvent")
	}

	tableName := string(rowsEvent.Table.Table)
	schemaName := string(rowsEvent.Table.Schema)

	// Rows是成对出现的: [旧值, 新值]
	for i := 0; i < len(rowsEvent.Rows); i += 2 {
		if i+1 >= len(rowsEvent.Rows) {
			break
		}

		oldRow := rowsEvent.Rows[i]
		newRow := rowsEvent.Rows[i+1]

		setClause := generateSetClause(oldRow, newRow)
		whereClause := generateWhereClause(oldRow)

		sql := fmt.Sprintf("UPDATE `%s`.`%s` SET %s WHERE %s",
			schemaName, tableName, setClause, whereClause)
		writer.Write(sql)
	}

	return nil
}

// 处理QUERY事件（DDL语句）
func handleQueryEvent(ev *replication.BinlogEvent, writer *SQLWriter) error {
	queryEvent, ok := ev.Event.(*replication.QueryEvent)
	if !ok {
		return fmt.Errorf("类型断言失败: 期望*replication.QueryEvent")
	}

	sql := string(queryEvent.Query)
	writer.Write("-- DDL操作: " + sql)

	return nil
}

// 生成INSERT SQL语句
func generateInsertSQL(schema, table string, columns []string, values []interface{}) string {
	valueStrs := make([]string, len(values))
	for i, v := range values {
		valueStrs[i] = formatValue(v)
	}

	return fmt.Sprintf("INSERT INTO `%s`.`%s` VALUES (%s);",
		schema, table, joinValues(valueStrs))
}

// 生成WHERE子句
func generateWhereClause(row []interface{}) string {
	parts := make([]string, len(row))
	for i, value := range row {
		parts[i] = fmt.Sprintf("column%d = %s", i, formatValue(value))
	}
	return joinValues(parts)
}

// 生成SET子句
func generateSetClause(oldRow, newRow []interface{}) string {
	parts := make([]string, len(newRow))
	for i, newValue := range newRow {
		oldValue := oldRow[i]
		// 只更新有变化的字段
		if fmt.Sprintf("%v", oldValue) != fmt.Sprintf("%v", newValue) {
			parts[i] = fmt.Sprintf("column%d = %s", i, formatValue(newValue))
		}
	}

	// 过滤空值
	var nonEmptyParts []string
	for _, part := range parts {
		if part != "" {
			nonEmptyParts = append(nonEmptyParts, part)
		}
	}

	return joinValues(nonEmptyParts)
}

// 格式化值
func formatValue(value interface{}) string {
	if value == nil {
		return "NULL"
	}

	switch v := value.(type) {
	case string:
		return fmt.Sprintf("'%s'", escapeString(v))
	case []byte:
		return fmt.Sprintf("'%s'", escapeString(string(v)))
	default:
		return fmt.Sprintf("%v", v)
	}
}

// 转义字符串
func escapeString(s string) string {
	// 简单的转义，实际应用中可能需要更完整的实现
	return s
}

// 连接值
func joinValues(values []string) string {
	if len(values) == 0 {
		return ""
	}

	result := values[0]
	for i := 1; i < len(values); i++ {
		result += ", " + values[i]
	}
	return result
}

// withRetry 重试操作直到成功或超过最大重试次数
func withRetry(operation func() error, maxRetries int) error {
	var err error
	for i := 0; i < maxRetries; i++ {
		if err = operation(); err == nil {
			return nil
		}
		log.Printf("操作失败，尝试重连 (%d/%d): %v", i+1, maxRetries, err)
		time.Sleep(time.Duration(i+1) * time.Second)
	}
	return fmt.Errorf("超过最大重试次数: %v", err)
}