package messaging

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"time"

	"github.com/nats-io/nats.go"
	"github.com/nats-io/nats.go/jetstream"

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

const (
	// DefaultStreamName 默认流名称
	DefaultStreamName = "GOTIDB_DATA"

	// DefaultSubject 默认主题
	DefaultSubject = "gotidb.data.>"
)

// DataMessage 数据消息
type DataMessage struct {
	DeviceID   string            `json:"device_id"`
	MetricCode string            `json:"metric_code"`
	Labels     map[string]string `json:"labels"`
	Timestamp  time.Time         `json:"timestamp"`
	Value      interface{}       `json:"value"`
}

// MessageHandler 消息处理函数类型
type MessageHandler func(msg DataMessage) error

// NATSMessaging NATS消息系统
type NATSMessaging struct {
	conn       *nats.Conn
	js         jetstream.JetStream
	stream     jetstream.Stream
	consumer   jetstream.Consumer
	handlers   []MessageHandler
	subContext context.Context
	subCancel  context.CancelFunc
}

// NATSConfig NATS配置
type NATSConfig struct {
	URL        string
	StreamName string
	Subject    string
}

// NewNATSMessaging 创建一个新的NATS消息系统
func NewNATSMessaging(config NATSConfig) (*NATSMessaging, error) {
	// 使用默认值
	if config.StreamName == "" {
		config.StreamName = DefaultStreamName
	}
	if config.Subject == "" {
		config.Subject = DefaultSubject
	}

	// 连接NATS服务器
	conn, err := nats.Connect(config.URL)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to NATS: %v", err)
	}

	// 创建JetStream上下文
	js, err := jetstream.New(conn)
	if err != nil {
		conn.Close()
		return nil, fmt.Errorf("failed to create JetStream context: %v", err)
	}

	// 创建或获取流
	stream, err := js.Stream(context.Background(), config.StreamName)
	if err != nil {
		// 如果流不存在，创建一个新的流
		cfg := jetstream.StreamConfig{
			Name:     config.StreamName,
			Subjects: []string{config.Subject},
		}
		stream, err = js.CreateStream(context.Background(), cfg)
		if err != nil {
			conn.Close()
			return nil, fmt.Errorf("failed to create stream: %v", err)
		}
	}

	return &NATSMessaging{
		conn:     conn,
		js:       js,
		stream:   stream,
		handlers: make([]MessageHandler, 0),
	}, nil
}

// Publish 发布消息
func (n *NATSMessaging) Publish(ctx context.Context, id model.DataPointID, value model.DataValue) error {
	// 创建消息
	msg := DataMessage{
		DeviceID:   id.DeviceID,
		MetricCode: id.MetricCode,
		Labels:     id.Labels,
		Timestamp:  value.Timestamp,
		Value:      value.Value,
	}

	// 序列化消息
	data, err := json.Marshal(msg)
	if err != nil {
		return fmt.Errorf("failed to marshal message: %v", err)
	}

	// 构建主题
	subject := fmt.Sprintf("gotidb.data.%s.%s", id.DeviceID, id.MetricCode)

	// 发布消息
	_, err = n.js.Publish(ctx, subject, data)
	if err != nil {
		return fmt.Errorf("failed to publish message: %v", err)
	}

	return nil
}

// BatchPublish 批量发布消息
func (n *NATSMessaging) BatchPublish(ctx context.Context, batch []struct {
	ID    model.DataPointID
	Value model.DataValue
}) error {
	for _, item := range batch {
		if err := n.Publish(ctx, item.ID, item.Value); err != nil {
			return err
		}
	}
	return nil
}

// Subscribe 订阅消息
func (n *NATSMessaging) Subscribe(handler MessageHandler) error {
	// 添加处理函数
	n.handlers = append(n.handlers, handler)

	// 如果已经有订阅，不需要重新订阅
	if n.subContext != nil {
		return nil
	}

	// 创建消费者
	consumerConfig := jetstream.ConsumerConfig{
		Durable:       "gotidb-consumer",
		AckPolicy:     jetstream.AckExplicitPolicy,
		DeliverPolicy: jetstream.DeliverAllPolicy,
	}

	var err error
	n.consumer, err = n.stream.CreateOrUpdateConsumer(context.Background(), consumerConfig)
	if err != nil {
		return fmt.Errorf("failed to create consumer: %v", err)
	}

	// 创建可取消的上下文
	n.subContext, n.subCancel = context.WithCancel(context.Background())

	// 开始消费消息
	go n.consumeMessages()

	return nil
}

// consumeMessages 消费消息
func (n *NATSMessaging) consumeMessages() {
	// 创建消费迭代器
	iter, err := n.consumer.Messages()
	if err != nil {
		log.Printf("Failed to create message iterator: %v", err)
		return
	}

	// 消费消息
	for {
		select {
		case <-n.subContext.Done():
			return
		default:
			msg, err := iter.Next()
			if err != nil {
				log.Printf("Failed to get next message: %v", err)
				continue
			}

			// 解析消息
			var dataMsg DataMessage
			if err := json.Unmarshal(msg.Data(), &dataMsg); err != nil {
				log.Printf("Failed to unmarshal message: %v", err)
				msg.Ack()
				continue
			}

			// 调用所有处理函数
			for _, handler := range n.handlers {
				if err := handler(dataMsg); err != nil {
					log.Printf("Failed to handle message: %v", err)
				}
			}

			// 确认消息
			msg.Ack()
		}
	}
}

// Unsubscribe 取消订阅
func (n *NATSMessaging) Unsubscribe() {
	if n.subCancel != nil {
		n.subCancel()
		n.subContext = nil
		n.subCancel = nil
	}
}

// Close 关闭连接
func (n *NATSMessaging) Close() error {
	// 取消订阅
	n.Unsubscribe()

	// 关闭连接
	n.conn.Close()

	return nil
}