package main

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"github.com/confluentinc/confluent-kafka-go/kafka"
	"github.com/go-redis/redis/v8"
	"github.com/gorilla/mux"
	"gopkg.in/yaml.v2"
	"log"
	"net/http"
	"os"
	"time"
)

type Message struct {
	Id        string `json:"Id"`
	Name      string `json:"Name"`
	Image     string `json:"Image"`
	Status    string `json:"Status"`
	Timestamp string `json:"Timestamp"`
}

type Config struct {
	Redis struct {
		Host string `yaml:"host"`
		Port string `yaml:"port"`
	}
	Kafka struct {
		Host  string `yaml:"host"`
		Port  string `yaml:"port"`
		Topic string `yaml:"topic"`
	}
}

func getConfig(configPath string) (*Config, error) {
	// Create config structure
	config := &Config{}

	// Open config file
	file, err := os.Open(configPath)
	if err != nil {
		return nil, err
	}
	defer func(file *os.File) {
		err := file.Close()
		if err != nil {

		}
	}(file)

	// Init new YAML decode
	d := yaml.NewDecoder(file)

	// Start YAML decoding from file
	if err := d.Decode(&config); err != nil {
		return nil, err
	}

	return config, nil
}

func loadConfig() *Config {
	cfg, err := getConfig("config.yaml")
	if err != nil {
		log.Fatal(err)
	}
	return cfg
}

func initRedis(cfg Config, ctx context.Context) *redis.Client {
	redisClient := redis.NewClient(&redis.Options{
		Addr: cfg.Redis.Host + ":" + cfg.Redis.Port,
	})
	_, err := redisClient.Do(context.Background(), "CONFIG", "SET", "notify-keyspace-events", "KEA").Result()
	if err != nil {
		fmt.Printf("unable to set keyspace events %v", err.Error())
		os.Exit(1)
	}
	redisClient.ConfigSet(ctx, "notify-keyspace-events", "Ex")
	return redisClient
}

func initKafka(cfg Config) *kafka.Producer {
	p, err := kafka.NewProducer(&kafka.ConfigMap{
		"bootstrap.servers": cfg.Kafka.Host + ":" + cfg.Kafka.Port,
		"client.id":         "myProducer",
		"message.max.bytes": 15728640,
		"acks":              "all"})

	if err != nil {
		fmt.Printf("Failed to create producer: %s\n", err)
		os.Exit(1)
	}
	return p
}

func listenForExpirationEvents(redisClient *redis.Client, kafkaClient *kafka.Producer, ctx context.Context, config Config) {
	ps := redisClient.PSubscribe(ctx, "__keyevent@0__:expired")
	defer func(ps *redis.PubSub) {
		err := ps.Close()
		if err != nil {

		}
	}(ps)

	for exp := range ps.Channel() {
		//Print expired payload ID
		fmt.Println(exp.Payload)
		// Broadcast expiration event
		msg := Message{}
		broadcastRecord(kafkaClient, msg, config.Kafka.Topic)
		fmt.Printf("Done Broadcasting Expiration\n")
	}
}

func broadcastRecord(kafkaClient *kafka.Producer, msg Message, topic string) {
	var msgJSON, err = json.Marshal(msg)
	if err != nil {
		log.Println("Error marshalling json:", err)
		return
	}
	err = kafkaClient.Produce(&kafka.Message{
		TopicPartition: kafka.TopicPartition{Topic: &topic, Partition: kafka.PartitionAny},
		Value:          msgJSON},
		nil, // delivery channel
	)
	if err != nil {
		log.Println("Error publishing message:", err)
		return
	}
	for e := range kafkaClient.Events() {
		switch ev := e.(type) {
		case *kafka.Message:
			if ev.TopicPartition.Error != nil {
				fmt.Printf("Failed to deliver message: %v\n", ev.TopicPartition)
			} else {
				fmt.Printf("Successfully produced record to topic %s partition [%d] @ offset %v\n",
					*ev.TopicPartition.Topic, ev.TopicPartition.Partition, ev.TopicPartition.Offset)
			}
		}
	}
}

func fetchAllRecords(redisClient *redis.Client, ctx context.Context) (map[string]string, error) {
	allKeys, err := redisClient.Keys(ctx, "*").Result()
	if err != nil {
		return nil, fmt.Errorf("could not fetch keys: %v", err)
	}

	records := make(map[string]string)
	for _, key := range allKeys {
		value, err := redisClient.Get(ctx, key).Result()
		if errors.Is(err, redis.Nil) {
			continue // skip if key does not exist
		} else if err != nil {
			return nil, fmt.Errorf("could not fetch value for key %s: %v", key, err)
		}
		records[key] = value
	}

	return records, nil
}

func getStatus(w http.ResponseWriter, r *http.Request, redisClient *redis.Client, ctx context.Context) {
	if r.Method != http.MethodPost {
		http.Error(w, "Only POST method is allowed", http.StatusMethodNotAllowed)
		return
	}
	fmt.Println("Checking Status")
	var request struct {
		Id string `json:"Id"`
	}
	err := json.NewDecoder(r.Body).Decode(&request)
	if err != nil {
		fmt.Println("Invalid JSON format")
		fmt.Println(r.Body)
		http.Error(w, "Invalid JSON format", http.StatusBadRequest)
		return
	}

	if request.Id == "" {
		fmt.Println("Missing or empty Id field")
		http.Error(w, "Missing or empty Id field", http.StatusBadRequest)
		return
	}
	fmt.Println(request.Id)
	value, err := redisClient.Get(ctx, request.Id).Result()
	if errors.Is(err, redis.Nil) {
		message := Message{Id: request.Id, Status: "none", Timestamp: time.Now().Format(time.RFC3339)}
		w.Header().Set("Content-Type", "application/json")
		err := json.NewEncoder(w).Encode(message)
		if err != nil {
			return
		}
		return
	} else if err != nil {
		log.Printf("Redis error: %v", err)
		http.Error(w, "Error connecting to Redis", http.StatusInternalServerError)
		return
	}

	var message Message
	err = json.Unmarshal([]byte(value), &message)
	if err != nil {
		log.Printf("Failed to decode Redis data for Id: %s - %v", request.Id, err)
		http.Error(w, "Failed to parse data", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	err = json.NewEncoder(w).Encode(message)
	if err != nil {
		http.Error(w, "Failed to encode response", http.StatusInternalServerError)
	}
}

func setStatus(w http.ResponseWriter, r *http.Request, redisClient *redis.Client, kafkaClient *kafka.Producer, ctx context.Context, config Config) {
	if r.Method != http.MethodPost {
		http.Error(w, "Only POST method is allowed", http.StatusMethodNotAllowed)
		return
	}

	var msg Message
	err := json.NewDecoder(r.Body).Decode(&msg)
	if err != nil || msg.Id == "" || msg.Status == "" {
		http.Error(w, "Invalid request format", http.StatusBadRequest)
		return
	}

	if msg.Status == "none" {
		if err := redisClient.Del(ctx, msg.Id).Err(); err != nil {
			log.Printf("Error deleting key from Redis: %v", err)
			http.Error(w, "Failed to delete key from Redis", http.StatusInternalServerError)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
	} else {
		msgJSON, err := json.Marshal(msg)
		if err != nil {
			http.Error(w, "Failed to encode message", http.StatusInternalServerError)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}

		timeout := 20 * time.Second

		if err = redisClient.Set(ctx, msg.Id, msgJSON, timeout).Err(); err != nil {
			log.Printf("Failed to set key in Redis: %v", err)
			http.Error(w, "Failed to store data", http.StatusInternalServerError)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
	}
	broadcastRecord(kafkaClient, msg, config.Kafka.Topic)
	w.WriteHeader(http.StatusOK)
}

func updateMessages(w http.ResponseWriter, r *http.Request, redisClient *redis.Client, ctx context.Context) {
	if r.Method != http.MethodGet {
		http.Error(w, "Only GET method is allowed", http.StatusMethodNotAllowed)
		return
	}
	allRecords, err := fetchAllRecords(redisClient, ctx)
	if err != nil {
		log.Printf("Error fetching records: %v", err)
		http.Error(w, "Failed to fetch records", http.StatusInternalServerError)
		return
	}

	var messages []Message
	for _, record := range allRecords {
		var message Message
		err := json.Unmarshal([]byte(record), &message)
		if err != nil {
			log.Printf("Error unmarshalling record: %v", err)
			http.Error(w, "Failed to parse records", http.StatusInternalServerError)
			return
		}
		messages = append(messages, message)
	}

	w.Header().Set("Content-Type", "application/json")
	err = json.NewEncoder(w).Encode(messages)
	if err != nil {
		log.Printf("Error encoding response: %v", err)
		http.Error(w, "Failed to encode response", http.StatusInternalServerError)
	}
}

func enableCORS(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Access-Control-Allow-Origin", "*") // Allow all origins
		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")

		// Allow preflight requests for the OPTIONS method
		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusOK)
			return
		}
		next.ServeHTTP(w, r)
	})
}

func main() {
	log.Println("Starting Pogdark API")
	ctx := context.Background()
	config := loadConfig()
	redisClient := initRedis(*config, ctx)
	log.Println("Redis initiated")
	kafkaClient := initKafka(*config)
	log.Println("Kafka initiated")

	router := mux.NewRouter()

	// Register routes on the mux router
	router.HandleFunc("/getStatus", func(w http.ResponseWriter, r *http.Request) {
		getStatus(w, r, redisClient, ctx)
	}).Methods("POST")
	router.HandleFunc("/setStatus", func(w http.ResponseWriter, r *http.Request) {
		setStatus(w, r, redisClient, kafkaClient, ctx, *config)
	}).Methods("POST")
	router.HandleFunc("/updateMessages", func(w http.ResponseWriter, r *http.Request) {
		updateMessages(w, r, redisClient, ctx)
	}).Methods("GET")

	// Start server and other necessary goroutines
	go listenForExpirationEvents(redisClient, kafkaClient, ctx, *config)
	corsRouter := enableCORS(router)
	// Pass the mux router to ListenAndServe
	fmt.Println("Server started on :8080")
	err := http.ListenAndServe(":8080", corsRouter)
	if err != nil {
		fmt.Printf("Server error: %v\n", err)
	}
}