// Package handler provides HTTP handlers for various endpoints.
package handler

import (
	"context"
	"fmt"
	"net/http"
	"sort"
	"strconv"
	"time"

	"modelRT/constants"
	"modelRT/diagram"
	"modelRT/logger"
	"modelRT/model"
	"modelRT/network"
	"modelRT/util"

	"github.com/gin-gonic/gin"
	"github.com/gorilla/websocket"
)

var pullUpgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
	CheckOrigin: func(_ *http.Request) bool {
		return true
	},
}

// PullRealTimeDataHandler define real time data pull API
// @Summary 实时数据拉取 websocket api
// @Description 根据用户输入的clientID拉取对应的实时数据
// @Tags RealTime Component Websocket
// @Router /monitors/data/realtime/stream/:clientID [get]
func PullRealTimeDataHandler(c *gin.Context) {
	clientID := c.Param("clientID")
	if clientID == "" {
		err := fmt.Errorf("clientID is missing from the path")
		logger.Error(c, "query clientID from path failed", "error", err, "url", c.Request.RequestURI)
		c.JSON(http.StatusOK, network.FailureResponse{
			Code: http.StatusBadRequest,
			Msg:  err.Error(),
		})
		return
	}

	conn, err := pullUpgrader.Upgrade(c.Writer, c.Request, nil)
	if err != nil {
		logger.Error(c, "upgrade http protocol to websocket protocal failed", "error", err)
		c.JSON(http.StatusOK, network.FailureResponse{
			Code: http.StatusBadRequest,
			Msg:  err.Error(),
		})
		return
	}
	defer conn.Close()

	ctx, cancel := context.WithCancel(c.Request.Context())
	defer cancel()

	// TODO[BACKPRESSURE-ISSUE] 先期使用固定大容量对扇入模型进行定义 #1
	fanInChan := make(chan network.RealTimePullTarget, 10000)
	go processTargetPolling(ctx, globalSubState, clientID, fanInChan)
	go readClientMessages(ctx, conn, clientID, cancel)

	bufferMaxSize := constants.SendMaxBatchSize
	sendMaxInterval := constants.SendMaxBatchInterval
	buffer := make([]network.RealTimePullTarget, 0, bufferMaxSize)
	ticker := time.NewTicker(sendMaxInterval)
	defer ticker.Stop()

	for {
		select {
		case targetData, ok := <-fanInChan:
			if !ok {
				logger.Error(ctx, "fanInChan closed unexpectedly", "client_id", clientID)
				return
			}
			buffer = append(buffer, targetData)

			if len(buffer) >= bufferMaxSize {
				// buffer is full, send immediately
				if err := sendAggregateRealTimeDataStream(conn, buffer); err != nil {
					logger.Error(ctx, "when buffer is full, send the real time aggregate data failed", "client_id", clientID, "buffer", buffer, "error", err)
					return
				}
				// reset buffer
				buffer = make([]network.RealTimePullTarget, 0, bufferMaxSize)
				// reset the ticker to prevent it from triggering immediately after the ticker is sent
				ticker.Reset(sendMaxInterval)
			}
		case <-ticker.C:
			if len(buffer) > 0 {
				// when the ticker is triggered, all data in the send buffer is sent
				if err := sendAggregateRealTimeDataStream(conn, buffer); err != nil {
					logger.Error(ctx, "when the ticker is triggered, send the real time aggregate data failed", "client_id", clientID, "buffer", buffer, "error", err)
					return
				}
				// reset buffer
				buffer = make([]network.RealTimePullTarget, 0, bufferMaxSize)
			}
		case <-ctx.Done():
			// send the last remaining data
			if err := sendAggregateRealTimeDataStream(conn, buffer); err != nil {
				logger.Error(ctx, "send the last remaining data failed", "client_id", clientID, "buffer", buffer, "error", err)
			}
			logger.Info(ctx, "PullRealTimeDataHandler exiting as context is done.", "client_id", clientID)
			return
		}
	}
}

// readClientMessages 负责持续监听客户端发送的消息（例如 Ping/Pong, Close Frame, 或控制命令）
func readClientMessages(ctx context.Context, conn *websocket.Conn, clientID string, cancel context.CancelFunc) {
	// conn.SetReadLimit(512)
	for {
		msgType, msgBytes, err := conn.ReadMessage()
		if err != nil {
			if websocket.IsCloseError(err, websocket.CloseNormalClosure) {
				logger.Info(ctx, "client actively and normally closed the connection", "client_id", clientID)
			} else if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
				logger.Error(ctx, "an unexpected error occurred while reading the webSocket connection", "client_id", clientID, "error", err)
			} else {
				// handle other read errors (eg, I/O errors)
				logger.Error(ctx, "an error occurred while reading the webSocket connection", "client_id", clientID, "error", err)
			}
			cancel()
			break
		}

		// process normal message from client
		if msgType == websocket.TextMessage || msgType == websocket.BinaryMessage {
			logger.Info(ctx, "read normal message from client", "client_id", clientID, "content", string(msgBytes))
		}
	}
}

// sendAggregateRealTimeDataStream define func to responsible for continuously pushing aggregate real-time data to the client
func sendAggregateRealTimeDataStream(conn *websocket.Conn, targetsData []network.RealTimePullTarget) error {
	if len(targetsData) == 0 {
		return nil
	}
	response := network.SuccessResponse{
		Code: 200,
		Msg:  "success",
		Payload: network.RealTimePullPayload{
			Targets: targetsData,
		},
	}
	return conn.WriteJSON(response)
}

// processTargetPolling define function to process target in subscription map and data is continuously retrieved from redis based on the target
func processTargetPolling(ctx context.Context, s *SharedSubState, clientID string, fanInChan chan network.RealTimePullTarget) {
	// ensure the fanInChan will not leak
	defer close(fanInChan)
	logger.Info(ctx, fmt.Sprintf("start processing real time data polling for clientID:%s", clientID))
	stopChanMap := make(map[string]chan struct{})
	s.globalMutex.RLock()
	config, confExist := s.subMap[clientID]
	if !confExist {
		logger.Error(ctx, "can not found config into local stored map by clientID", "clientID", clientID)
		s.globalMutex.RUnlock()
		return
	}
	s.globalMutex.RUnlock()

	// TODO 测试log
	fmt.Printf("found subscription config for clientID:%s, start initial polling goroutines, config: %+v\n", clientID, config.components)
	logger.Info(ctx, fmt.Sprintf("found subscription config for clientID:%s, start initial polling goroutines", clientID), "components len", config.components)

	config.mutex.RLock()
	for interval, measurementTargets := range config.measurements {
		for _, target := range measurementTargets {
			// add a secondary check to prevent the target from already existing in the stopChanMap
			if _, exists := stopChanMap[target]; exists {
				logger.Warn(ctx, "target already exists in polling map, skipping start-up", "target", target)
				continue
			}

			targetContext, exist := config.targetContext[target]
			if !exist {
				logger.Error(ctx, "can not found subscription node param into param map", "target", target)
				continue
			}
			measurementInfo := targetContext.measurement

			queryGStopChan := make(chan struct{})
			// store stop channel with target into map
			stopChanMap[target] = queryGStopChan
			queryKey, err := model.GenerateMeasureIdentifier(measurementInfo.DataSource)
			if err != nil {
				logger.Error(ctx, "generate measurement indentifier by data_source field failed", "data_source", measurementInfo.DataSource, "error", err)
				continue
			}

			pollingConfig := redisPollingConfig{
				targetID: target,
				queryKey: queryKey,
				interval: interval,
				dataSize: int64(measurementInfo.Size),
			}
			go realTimeDataQueryFromRedis(ctx, pollingConfig, fanInChan, queryGStopChan)
		}
	}
	config.mutex.RUnlock()

	for {
		select {
		case transportTargets, ok := <-config.noticeChan:
			if !ok {
				logger.Error(ctx, "notice channel was closed unexpectedly", "clientID", clientID)
				stopAllPolling(ctx, stopChanMap)
				return
			}
			config.mutex.Lock()
			switch transportTargets.OperationType {
			case constants.OpAppend:
				appendTargets(ctx, config, stopChanMap, fanInChan, transportTargets.Targets)
			case constants.OpRemove:
				removeTargets(ctx, config, stopChanMap, transportTargets.Targets)
			}
			config.mutex.Unlock()
		case <-ctx.Done():
			logger.Info(ctx, fmt.Sprintf("stop all data retrieval goroutines under this clientID:%s", clientID))
			stopAllPolling(ctx, stopChanMap)
			return
		}
	}
}

// appendTargets starts new polling goroutines for targets that were just added
func appendTargets(ctx context.Context, config *RealTimeSubConfig, stopChanMap map[string]chan struct{}, fanInChan chan network.RealTimePullTarget, appendTargets []string) {
	appendTargetsSet := make(map[string]struct{}, len(appendTargets))
	for _, target := range appendTargets {
		appendTargetsSet[target] = struct{}{}
	}

	for _, target := range appendTargets {
		targetContext, exists := config.targetContext[target]
		if exists {
			logger.Warn(ctx, "the append target already exists in the real time data fetch process,skipping the startup step", "target", target)
			continue
		}

		if _, exists := stopChanMap[target]; exists {
			logger.Warn(ctx, "the append target already has a stop channel, skipping the startup step", "target", target)
			continue
		}

		queryGStopChan := make(chan struct{})
		stopChanMap[target] = queryGStopChan

		interval := targetContext.interval
		measurementTargets, ok := config.measurements[interval]
		if !ok {
			logger.Error(ctx, "targetContext exists but measurements is missing, cannot update config", "target", target, "interval", interval)
			continue
		}
		measurementTargets = append(measurementTargets, target)
		config.targetContext[target] = targetContext
		delete(appendTargetsSet, target)

		queryKey, err := model.GenerateMeasureIdentifier(targetContext.measurement.DataSource)
		if err != nil {
			logger.Error(ctx, "the append target generate redis query key identifier failed", "target", target, "error", err)
			continue
		}
		pollingConfig := redisPollingConfig{
			targetID: target,
			queryKey: queryKey,
			interval: targetContext.interval,
			dataSize: int64(targetContext.measurement.Size),
		}
		go realTimeDataQueryFromRedis(ctx, pollingConfig, fanInChan, queryGStopChan)

		logger.Info(ctx, "started new polling goroutine for appended target", "target", target, "interval", targetContext.interval)
	}

	allKeys := util.GetKeysFromSet(appendTargetsSet)
	if len(allKeys) > 0 {
		logger.Warn(ctx, fmt.Sprintf("the following targets:%v start up fetch real time data process goroutine not started", allKeys))
		clear(appendTargetsSet)
	}
}

// removeTargets define func to stops running polling goroutines for targets that were removed
func removeTargets(ctx context.Context, config *RealTimeSubConfig, stopChanMap map[string]chan struct{}, removeTargets []string) {
	for _, target := range removeTargets {
		targetContext, exist := config.targetContext[target]
		if !exist {
			logger.Warn(ctx, "removeTarget does not exist in targetContext map, skipping remove operation", "target", target)
			continue
		}

		stopChan, exists := stopChanMap[target]
		if !exists {
			logger.Warn(ctx, "removeTarget was not running, skipping remove operation", "target", target)
			continue
		}

		close(stopChan)
		delete(stopChanMap, target)
		delete(config.targetContext, target)

		interval := targetContext.interval
		measurementTargets, mesExist := config.measurements[interval]
		if !mesExist {
			logger.Warn(ctx, "targetContext exists but measurements is missing, cannot perform remove operation", "interval", interval, "target", target)
			continue
		}
		measurementTargets = util.RemoveTargetsFromSliceSimple(measurementTargets, []string{target})
		config.measurements[interval] = measurementTargets

		logger.Info(ctx, "stopped polling goroutine for removed target", "target", target)
	}
}

// stopAllPolling stops all running query goroutines for a specific client
func stopAllPolling(ctx context.Context, stopChanMap map[string]chan struct{}) {
	for target, stopChan := range stopChanMap {
		logger.Info(ctx, fmt.Sprintf("stop the data fetching behavior for the corresponding target:%s", target))
		close(stopChan)
	}
	clear(stopChanMap)
	return
}

// redisPollingConfig define struct for param which query real time data from redis
type redisPollingConfig struct {
	targetID string
	queryKey string
	interval string
	dataSize int64
}

func realTimeDataQueryFromRedis(ctx context.Context, config redisPollingConfig, fanInChan chan network.RealTimePullTarget, stopChan chan struct{}) {
	// TODO 测试log，后续可删除
	logger.Info(ctx, "start a redis query goroutine for real time data pulling", "targetID", config.targetID, "queryKey", config.queryKey, "interval", config.interval, "dataSize", config.dataSize)
	duration, err := time.ParseDuration(config.interval)
	if err != nil {
		logger.Error(ctx, "failed to parse the time string", "interval", config.interval, "error", err)
		return
	}
	ticker := time.NewTicker(duration)
	defer ticker.Stop()

	client := diagram.NewRedisClient()
	startTimestamp := util.GenNanoTsStr()

	fmt.Printf("realTimeDataQueryFromRedis duration:%+v\n:", duration)
	fmt.Printf("realTimeDataQueryFromRedis ticker:%+v\n:", ticker)
	fmt.Printf("realTimeDataQueryFromRedis startTimestamp:%s\n", startTimestamp)
	needPerformQuery := true
	for {
		if needPerformQuery {
			performQuery(ctx, client, config, fanInChan)
			needPerformQuery = false
		}

		select {
		case <-ticker.C:
			needPerformQuery = true
		case <-stopChan:
			logger.Info(ctx, "stop the redis query goroutine via a singal")
			return
		}
	}
}

func performQuery(ctx context.Context, client *diagram.RedisClient, config redisPollingConfig, fanInChan chan network.RealTimePullTarget) {
	members, err := client.QueryByZRangeByLex(ctx, config.queryKey, config.dataSize)
	if err != nil {
		logger.Error(ctx, "query real time data from redis failed", "key", config.queryKey, "error", err)
		return
	}

	pullDatas := make([]network.RealTimePullData, 0, len(members))
	for _, member := range members {
		pullDatas = append(pullDatas, network.RealTimePullData{
			Time:  member.Member.(string),
			Value: member.Score,
		})
	}
	sortPullDataByTimeAscending(ctx, pullDatas)
	targetData := network.RealTimePullTarget{
		ID:    config.targetID,
		Datas: pullDatas,
	}

	select {
	case fanInChan <- targetData:
	default:
		// TODO[BACKPRESSURE-ISSUE] 考虑 fanInChan 阻塞，当出现大量数据阻塞查询循环并丢弃时,采取背压方式解决问题 #1
		logger.Warn(ctx, "fanInChan is full, dropping real-time data frame", "key", config.queryKey, "data_size", len(members))
	}
}

func sortPullDataByTimeAscending(ctx context.Context, data []network.RealTimePullData) {
	sort.Slice(data, func(i, j int) bool {
		t1, err1 := strconv.ParseInt(data[i].Time, 10, 64)
		if err1 != nil {
			logger.Error(ctx, "parsing real time data timestamp failed", "index", i, "time", data[i].Time, "error", err1)
			return false
		}

		t2, err2 := strconv.ParseInt(data[j].Time, 10, 64)
		if err2 != nil {
			logger.Error(ctx, "parsing real time data timestamp failed", "index", j, "time", data[j].Time, "error", err2)
			return true
		}
		return t1 < t2
	})
}