package main

import (
	"fmt"
	"log"
	"net"
	"strings"
	"time"
)

func handshakee(handshakerAddress, localAddress string, name, target string) {

	// Get our address as a usable UDPAddr.
	remoteAddr, _ := net.ResolveUDPAddr("udp", handshakerAddress)

	// Get a random local port.
	localAddr, _ := net.ResolveUDPAddr("udp", localAddress)
	log.Printf("Attempting to listen on %s\n", localAddr.String())

	// Start listening!
	localConn, err := net.ListenUDP("udp", localAddr)
	if err != nil {
		log.Fatal(err)
	}

	go func() {
		log.Println("Sending REG")
		_, err := localConn.WriteTo([]byte(fmt.Sprintf("REG %s", name)), remoteAddr)
		if err != nil {
			panic(err)
		}

		if target != "" {
			log.Printf("Sending AWAIT for %s\n", target)
			_, err := localConn.WriteTo([]byte(fmt.Sprintf("AWAIT %s", target)), remoteAddr)
			if err != nil {
				panic(err)
			}
		}
	}()

	listen(localConn, name)
}

func listen(conn *net.UDPConn, name string) {
	log.Printf("Listening on %s\n", conn.LocalAddr().String())
	for {
		buffer := make([]byte, 1024)
		bytesRead, fromAddr, err := conn.ReadFromUDP(buffer)
		if err != nil {
			fmt.Println("[ERROR]", err)
			continue
		}
		msg := string(buffer[0:bytesRead])
		parts := strings.Split(msg, " ")
		if parts[0] == "ARRIVED" {
			log.Printf("recv ARRIVED for %s\n", parts[1])
			otherAddr, _ := net.ResolveUDPAddr("udp", parts[1])
			conn.WriteTo([]byte(fmt.Sprintf("HELLO %s", name)), otherAddr)
			go chatWith(conn, name, parts[1])
		} else if parts[0] == "HELLO" {
			log.Printf("recv HELLO from %s\n", fromAddr.String())
			go chatWith(conn, name, fromAddr.String())
		} else {
			fmt.Printf("Unhandled: %+v\n", parts)
		}
	}

}

func chatWith(conn *net.UDPConn, name string, otherClient string) {
	log.Printf("Beginning chat with %s\n", otherClient)
	otherAddr, _ := net.ResolveUDPAddr("udp", otherClient)
	for {
		log.Println("Sending hello...")
		bytesWritten, err := conn.WriteTo([]byte(fmt.Sprintf("Hello from %s", name)), otherAddr)
		if err != nil {
			log.Printf("err: %s\n", err)
		} else {
			log.Printf("... wrote %d bytes.\n", bytesWritten)
		}
		time.Sleep(5 * time.Second)
	}
}