// Package realtimedata define real time data operation functions
package realtimedata

import (
	"context"
	"encoding/json"
	"sync"
	"time"

	"modelRT/constants"
	"modelRT/database"
	"modelRT/logger"
	"modelRT/network"

	"github.com/confluentinc/confluent-kafka-go/kafka"
	"github.com/gofrs/uuid"
	"gorm.io/gorm"
)

// CacheManager define structure for managing cache items
type CacheManager struct {
	mutex         sync.RWMutex
	store         sync.Map
	pool          sync.Pool
	dbClient      *gorm.DB
	kafkaConsumer *kafka.Consumer
	ttl           time.Duration
}

// NewCacheManager define func to create new cache manager
func NewCacheManager(db *gorm.DB, kf *kafka.Consumer, ttl time.Duration) *CacheManager {
	cm := &CacheManager{
		dbClient:      db,
		kafkaConsumer: kf,
		ttl:           ttl,
	}
	cm.pool.New = func() any {
		item := &CacheItem{}
		return item
	}
	return cm
}

// RealTimeComponentMonitor define func to continuously processing component info and build real time component data monitor from kafka specified topic
func (cm *CacheManager) RealTimeComponentMonitor(ctx context.Context, topic string, duration string) {
	// context for graceful shutdown
	cancelCtx, cancel := context.WithCancel(ctx)
	defer cancel()

	monitorConsumer := cm.kafkaConsumer

	// subscribe the monitor topic
	err := monitorConsumer.SubscribeTopics([]string{topic}, nil)
	if err != nil {
		logger.Error(ctx, "subscribe to the monitor topic failed", "topic", topic, "error", err)
		return
	}
	defer monitorConsumer.Close()

	timeoutDuration, err := time.ParseDuration(duration)
	if err != nil {
		logger.Error(ctx, "parse duration failed", "duration", duration, "error", err)
		return
	}

	// continuously read messages from kafka
	for {
		select {
		case <-cancelCtx.Done():
			logger.Info(ctx, "context canceled, stopping read loop")
			return
		default:
			msg, err := monitorConsumer.ReadMessage(timeoutDuration)
			if err != nil {
				if err.(kafka.Error).Code() == kafka.ErrTimedOut {
					continue
				}
				logger.Error(ctx, "consumer read message failed", "error", err)
				continue
			}

			var realTimeData network.RealTimeDataReceiveRequest
			if err := json.Unmarshal(msg.Value, &realTimeData); err != nil {
				logger.Error(ctx, "unmarshal kafka message failed", "message", string(msg.Value), "error", err)
				continue
			}

			key := realTimeData.PayLoad.ComponentUUID
			_, err = cm.StoreIntoCache(ctx, key)
			if err != nil {
				logger.Error(ctx, "store into cache failed", "key", key, "error", err)
				continue
			}

			_, err = monitorConsumer.CommitMessage(msg)
			if err != nil {
				logger.Error(ctx, "manual submission information failed", "message", msg, "error", err)
			}
		}
	}
}

// GetCacheItemFromPool define func to get a cache item from the pool
func (cm *CacheManager) GetCacheItemFromPool() *CacheItem {
	item := cm.pool.Get().(*CacheItem)
	item.Reset()
	return item
}

// PutCacheItemToPool define func to put a cache item back to the pool
func (cm *CacheManager) PutCacheItemToPool(item *CacheItem) {
	if item != nil {
		item.Reset()
		cm.pool.Put(item)
	}
}

// StoreIntoCache define func to store data into cache, if the key already exists and is not expired, return the existing item
func (cm *CacheManager) StoreIntoCache(ctx context.Context, key string) (*CacheItem, error) {
	cm.mutex.Lock()
	defer cm.mutex.Unlock()

	if cachedItemRaw, ok := cm.store.Load(key); ok {
		cachedItem := cachedItemRaw.(*CacheItem)
		if !cachedItem.IsExpired(cm.ttl) {
			cachedItem.lastAccessed = time.Now()
			return cachedItem, nil
		}
		cm.PutCacheItemToPool(cachedItem)
		cm.store.Delete(key)
	}

	uuid, err := uuid.FromString(key)
	if err != nil {
		logger.Error(ctx, "format key to UUID failed", "key", key, "error", err)
		return nil, constants.ErrFormatUUID
	}

	componentInfo, err := database.QueryComponentByUUID(ctx, cm.dbClient, uuid)
	if err != nil {
		logger.Error(ctx, "query component from db failed by uuid", "component_uuid", key, "error", err)
		return nil, constants.ErrQueryComponentByUUID
	}
	newItem := cm.GetCacheItemFromPool()
	newItem.key = key
	newItem.value = []any{componentInfo.Context}
	// newItem.calculatorFunc = componentInfo.CalculatorFunc
	newItem.lastAccessed = time.Now()

	// 在存储前启动goroutine
	if newItem.calculatorFunc != nil {
		newCtx, newCancel := context.WithCancel(ctx)
		newItem.cancelFunc = newCancel
		go newItem.calculatorFunc(newCtx, newItem.topic, newItem.value)
	}

	cm.store.Store(key, newItem)
	return newItem, nil
}

// UpdateCacheItem define func to update cache item with new data and trigger new calculation
func (cm *CacheManager) UpdateCacheItem(ctx context.Context, key string, newData any) error {
	cm.mutex.Lock()
	defer cm.mutex.Unlock()

	cache, existed := cm.store.Load(key)
	if !existed {
		return nil
	}

	cacheItem, ok := cache.(*CacheItem)
	if !ok {
		return constants.ErrFormatCache
	}

	// stop old calculation goroutine
	if cacheItem.cancelFunc != nil {
		cacheItem.cancelFunc()
	}

	oldValue := cacheItem.value
	cacheItem.value = []any{newData}
	cacheItem.lastAccessed = time.Now()

	newCtx, newCancel := context.WithCancel(ctx)
	cacheItem.cancelFunc = newCancel

	swapped := cm.store.CompareAndSwap(key, oldValue, cacheItem)
	if !swapped {
		cacheValue, _ := cm.store.Load(key)
		logger.Error(ctx, "store new value into cache failed,existed concurrent modification risk", "key", key, "old_value", oldValue, "cache_value", cacheValue, "store_value", cacheItem.value)
		return constants.ErrConcurrentModify
	}

	// start new calculation goroutine
	if cacheItem.calculatorFunc != nil {
		go cacheItem.calculatorFunc(newCtx, cacheItem.topic, cacheItem.value)
	}
	return nil
}