package main
 
import (
	"bufio"
	"fmt"
	"log"
	"net"
)
 
type Client struct {
	id      string
	conn    *net.Conn
	message chan string
}
 
type Hub struct {
	clients  map[*Client]bool
	entering chan *Client
	leaving  chan *Client
	messages chan string
}
 
func main() {
	hub := &Hub{
		clients:  make(map[*Client]bool),
		entering: make(chan *Client),
		leaving:  make(chan *Client),
		messages: make(chan string),
	}
 
	listener, err := net.Listen("tcp", ":8000")
	if err != nil {
		log.Fatal(err)
	}
	go hub.broadcaster()
	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Println(err)
			continue
		}
		go hub.handleConn(conn)
	}
}
 
func (hub *Hub) broadcaster() {
	for {
		select {
		case msg := <-hub.messages:
			for cli := range hub.clients {
				cli.message <- msg
			}
		case cli := <-hub.entering:
			hub.clients[cli] = true
		case cli := <-hub.leaving:
			delete(hub.clients, cli)
		}
	}
}
 
func (hub *Hub) handleConn(conn net.Conn) {
	defer conn.Close()
	ch := make(chan string)
	who := conn.RemoteAddr().String()
	client := &Client{who, &conn, ch}
 
	go hub.writeLoop(client)
	ch <- "welcome " + client.id
 
	hub.messages <- client.id + " join chat"
	hub.entering <- client
	hub.readLoop(client)
	hub.messages <- client.id + " has left"
	hub.leaving <- client
}
 
func (hub *Hub) writeLoop(client *Client) {
	for msg := range client.message {
		fmt.Fprintf(*client.conn, "%s\n", msg)
	}
}
 
func (hub *Hub) readLoop(client *Client) {
	input := bufio.NewScanner(*client.conn)
	for input.Scan() {
		hub.messages <- client.id + ": " + input.Text()
	}
}