package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net"
	"sync"
	"time"
)

func readRequest(conn net.Conn) (Message, error) {
	// 1 мегабайт
	var maxBodySize uint32 = 1048576

	var message Message
	var err error

	buf := make([]byte, 4096)
	_, err = conn.Read(buf)
	if err != nil {
		return message, err
	}

	size := fromBytes(buf[:4])
	if size > maxBodySize {
		resp, _ := json.Marshal(Response{
			Status: FAILURE,
			Data:   "Превышен максимальный размер запроса",
		})

		_ = sendMessage(conn, resp)
		return message, errors.New("body size exceeded")
	}

	rawMessage := buf[4 : size+4]
	return parseMessage(rawMessage)
}

func handleAuthentication(conn net.Conn) bool {
	maxAuthAttempts := 5
	authAttempts := 0
	authenticated := false

	for {
		if authAttempts >= maxAuthAttempts {
			resp, _ := json.Marshal(Response{
				Status: FAILURE,
				Data:   "Превышено количество неавторизованных запросов",
			})

			_ = sendMessage(conn, resp)
			break
		}

		message, err := readRequest(conn)
		if err != nil {
			break
		}
		authAttempts += 1

		if message.Type == AUTHENTICATE {
			// TODO(andrew): Добавить процесс аутентификации
			if true {
				authenticated = true
				resp, _ := json.Marshal(Response{
					Status: SUCCESS,
					Data:   "Аутентификация прошла успешно",
				})
				_ = sendMessage(conn, resp)
				break
			} else {
				resp, _ := json.Marshal(Response{
					Status: FAILURE,
					Data:   "При аутентификации произошла ошибка",
				})
				_ = sendMessage(conn, resp)
			}
			continue
		}

		resp, _ := json.Marshal(Response{
			Status: FAILURE,
			Data:   "Для работы с сервером необходима аутентификация",
		})

		err = sendMessage(conn, resp)
		if err != nil {
			break
		}
	}
	return authenticated
}

func handleConnection(conn net.Conn, c chan Message) {
	defer conn.Close()

	authenticated := handleAuthentication(conn)
	if authenticated {
		for {
			message, err := readRequest(conn)
			if err != nil {
				break
			}

			channelLock.Lock()
			c <- message

			if message.Data == "exit" {
				break
			}

			resp, _ := json.Marshal(Response{
				Status: SUCCESS,
				Data:   "some data",
			})
			err = sendMessage(conn, resp)
			if err != nil {
				break
			}
		}
	}
	fmt.Println("Closed connection (receiver handler)")
	received.RLock()
	sz := len(received.data)
	received.RUnlock()
	fmt.Printf("There is %d messages in storage\n", sz)
}

func reader(c chan Message) {
	//const maxMessages uint64 = 65536
	//var count uint64 = 0
	for {
		//fmt.Println("Waiting for message")
		data := <-c
		channelLock.Unlock()
		//fmt.Println("Received message:", data.Data)

		received.Lock()
		//fmt.Println("Locked received")
		//if count >= maxMessages {
		//	received.data = []Message{data}
		//	received.messageShift += maxMessages
		//} else {
		//	received.data = append(received.data, data)
		//	count += 1
		//}
		received.data = append(received.data, data)
		received.Unlock()
		//fmt.Println("Unlocked received")
	}
}

func handleSender(conn net.Conn) {
	defer conn.Close()

	authenticated := handleAuthentication(conn)
	if !authenticated {
		fmt.Println("Sender is not authenticated")
		return
	}
	fmt.Println("Sender is authenticated")
	lastIndex := 0

	for {
		var message Message
		idx := uint64(lastIndex)
		if idx < uint64(len(received.data)) {
			received.RLock()
			message = received.data[idx]
			received.RUnlock()

			resp, _ := json.Marshal(Response{
				Status: SUCCESS,
				Data:   message.serialize(),
			})
			err := sendMessage(conn, resp)
			if err != nil {
				fmt.Printf("Failed to send %d: %s\n", idx, err)
				break
			} else {
				message, err := readRequest(conn)
				if err != nil {
					break
				}
				if message.Data == SUCCESS {
					lastIndex += 1
				}
			}
		} else {
			time.Sleep(100 * time.Millisecond)
			continue
		}
	}
}

var received struct {
	sync.RWMutex
	data []Message
}

var channelLock sync.Mutex

func main() {
	var wg sync.WaitGroup

	c := make(chan Message)
	go reader(c)

	sock, err := net.Listen("tcp", "localhost:8080")
	handleError(err)
	defer sock.Close()
	wg.Add(1)
	go func(sock net.Listener) {
		for {
			conn, err := sock.Accept()
			if err == nil {
				go handleConnection(conn, c)
			} else {
				break
			}
		}
		wg.Done()
	}(sock)

	senderSock, err := net.Listen("tcp", "localhost:8081")
	handleError(err)
	defer senderSock.Close()
	wg.Add(1)
	go func(sock net.Listener) {
		for {
			conn, err := sock.Accept()
			if err == nil {
				go handleSender(conn)
			} else {
				break
			}
		}
		wg.Done()
	}(senderSock)

	wg.Wait()
}

func handleError(err error) {
	if err != nil {
		log.Fatal(err)
	}
}