// Copyright (c) 2016 Florian Fischer. All rights reserved.
// Use of this source code is governed by a MIT license found in the LICENSE file.

package net

import (
	"bufio"
	"encoding/json"
	"errors"
	"fmt"
	"net"
	"strconv"
	"strings"
	"sync"

	"muhq.space/go/muhq/goffel/logic"
)

var (
	// 0-9 Misc
	// 10-19 Sucess
	// 20-29 IO Errors
	// 30 Command Errors
	// 90-99 Session Responses
	responsePlain = map[int]string{
		0:  "Success: ",
		1:  "Welcome ",
		2:  "Sessions:",
		11: "Help:\r\n",
		12: "Score:\r\n",
		13: "Dice: ",
		14: "Insert: ",
		15: "Cancel: ",
		16: "Reroll: ",
		20: "I/O Error: ",
		21: "Json Decoding Error: ",
		30: "Invalid Command: ",
		31: "Insert Error: ",
		32: "Cancel Error: ",
		33: "Reroll Error: ",
		90: "Connected To: ",
		91: "To Many Players: ",
		92: "New Players: ",
		93: "Starting Game: ",
		94: "Round: ",
		95: "", // Used to forward results of other players
		96: "Remove Client: ",
		97: "Winners: ",
	}
)

// Internal structure representing a server response
type sMsg struct {
	Response int
	Payload  interface{}
}

func (msg sMsg) String() string {
	response := responsePlain[msg.Response]
	payload := msg.Payload
	res := ""
	if msg.Response == 2 {
		sessionsptr, _ := msg.Payload.(*map[string]*session)
		sessions := *sessionsptr
		s := ""
		for name, session := range sessions {
			s += fmt.Sprintf("\r\n%s: %v", name, session)
		}
		payload = s
	}
	if msg.Response == 11 {
		a, _ := msg.Payload.([]string)
		payload = strings.Join(a, "\r\n")
	}
	if msg.Response == 95 {
		a, _ := msg.Payload.([]interface{})
		res, _ = a[0].(string)
		msg, _ = a[1].(sMsg)
		res += " " + responsePlain[msg.Response]
	}
	if msg.Response == 14 {
		a, _ := msg.Payload.([]interface{})
		c, _ := a[0].(logic.Cmd)
		payload = fmt.Sprintf("%d -> %v", a[1], logic.ScoreNames[c.Argv[0]])
	} else if msg.Response == 15 {
		a, _ := msg.Payload.([]interface{})
		c, _ := a[0].(logic.Cmd)
		payload = fmt.Sprintf("%v", logic.ScoreNames[c.Argv[0]])
	}
	return fmt.Sprintf("%s%s%v", response, res, payload)
}

type client struct {
	sock     net.Conn
	reader   *bufio.Reader
	writer   *bufio.Writer
	encoder  *json.Encoder
	decoder  *json.Decoder
	encoding string
	players  []logic.Player
	results  chan sMsg
}

func (c *client) send(msg sMsg) error {
	var err error
	if c.encoding == "plain" {
		_, err = c.writer.WriteString(fmt.Sprintf("%v\r\n", msg))
		if err == nil {
			err = c.writer.Flush()
		}
	} else {
		err = c.encoder.Encode(msg)
	}
	return err
}

func (c *client) fail(res int, pl interface{}) {
	c.send(sMsg{res, pl})
	c.sock.Close()
}

func (c *client) recvCmd() (logic.Cmd, error) {
	var err error
	var cmd logic.Cmd
	if c.encoding == "plain" {
		input := ""
		input, err = c.reader.ReadString('\n')
		if err != nil {
			return cmd, err
		}
		cmd, err = logic.ParseCmd(input)
	} else {
		err = c.decoder.Decode(&cmd)
	}
	return cmd, err
}

func (c *client) round(round int, wg *sync.WaitGroup) {
	dice := logic.Dice{}
	var msg sMsg

	for _, p := range c.players {
		fin := false
		dice.Roll(nil)
		cmd := logic.Cmd{}
		var err error
		rerolls := 0
		err = c.send(sMsg{94, []interface{}{round, p.Name, dice}})
		if err != nil {
			fin = true
		}
		for !fin {
			// clear message
			msg = sMsg{}
			cmd, err = c.recvCmd()
			if err != nil {
				msg.Response = 30
				msg.Payload = err
			}

			switch cmd.Cmd {
			case "h":
				msg.Response = 11
				msg.Payload = logic.CmdHelp(cmd.Argv[0])
			case "p":
				msg.Response = 12
				msg.Payload = p.Score
			case "d":
				msg.Response = 13
				msg.Payload = dice
			case "q":
				//client quits
				err = errors.New("Quit")
				c.sock.Close()
			case "i":
				i, err := p.Score.Insert(dice, cmd.Argv[0])
				if err != nil {
					msg.Response = 31
					msg.Payload = err
				} else {
					msg.Response = 14
					msg.Payload = []interface{}{cmd, i, p.Score}
					fin = true
				}
			case "c":
				err := p.Score.Cancel(cmd.Argv[0])
				if err != nil {
					msg.Response = 32
					msg.Payload = err
				} else {
					msg.Response = 15
					msg.Payload = []interface{}{cmd, p.Score}
					fin = true
				}
			case "r":
				var err error
				if rerolls < 2 {
					err = dice.Roll(cmd.Argv)
				} else {
					err = errors.New("Only two rerolls are allowed.")
				}
				if err != nil {
					msg.Response = 33
					msg.Payload = err
				} else {
					msg.Response = 16
					msg.Payload = dice
					rerolls++
				}
			default:
			}
			if err = c.send(msg); err != nil {
				fin = true
			}
		}
		if err != nil {
			msg = sMsg{96, err}
		} else {
			msg = sMsg{95, []interface{}{p.Name, msg}}
		}
		c.results <- msg
	}
	wg.Done()
}

type session struct {
	clients    []*client
	maxPlayers int
	curPlayers int
	status     string
}

func (s session) String() (ret string) {
	ret += s.status
	ret += " max:"
	ret += strconv.Itoa(s.maxPlayers)
	ret += " p:"
	names := make([]string, 0, s.maxPlayers)
	for _, c := range s.clients {
		for _, p := range c.players {
			names = append(names, p.Name)
		}
	}
	return fmt.Sprintf("%s%v", ret, names)
}

func (s *session) terminate(reason sMsg) {
	for _, c := range s.clients {
		noreason := sMsg{}
		if reason != noreason {
			c.send(reason)
		}
		c.sock.Close()
	}
	s.status = "TERMINATED"
}

func (s *session) addClient(c *client) {
	newNames := make([]string, 0, len(c.players))
	for _, n := range c.players {
		newNames = append(newNames, n.Name)
	}
	okClients := make([]*client, 0, len(c.players))
	for _, other := range s.clients {
		err := other.send(sMsg{92, newNames})
		if err == nil {
			okClients = append(okClients, other)
		} else {
			s.curPlayers--
		}
	}
	s.clients = okClients
	s.clients = append(s.clients, c)
	s.curPlayers += len(c.players)
	if s.curPlayers == s.maxPlayers {
		go s.play()
	}
}

func (s *session) play() {
	s.status = "PLAYING"
	msg := sMsg{93, ""}
	wg := sync.WaitGroup{}
	for _, c := range s.clients {
		c.send(msg)
	}
	var reason sMsg
	for round := 1; round < 14; round++ {
		wg.Add(len(s.clients))
		for _, c := range s.clients {
			go c.round(round, &wg)
		}
		// broadcast results
		wg.Wait()
		badClients := make(map[*client]bool)
		for i, c := range s.clients {
			for _, p := range c.players {
				res := <-c.results
				// collect broken clients
				if res.Response == 96 {
					badClients[c] = true
					res = sMsg{96, []interface{}{p.Name, res.Payload}}
				}
				for j, c2 := range s.clients {
					if i != j {
						// ignore error
						c2.send(res)
					}
				}
			}
		}
		// remove broken clients
		okClients := make([]*client, 0, len(s.clients)-len(badClients))
		for _, c := range s.clients {
			if _, bad := badClients[c]; bad == false {
				okClients = append(okClients, c)
			}
		}
		s.clients = okClients
	}
	best := make([]logic.Player, 0, len(s.clients))
	for _, c := range s.clients {
		b, _ := logic.FindBest(c.players)
		best = append(best, b...)
	}
	winners, max := logic.FindBest(best)
	msg = sMsg{97, []interface{}{max, winners}}
	for _, c := range s.clients {
		c.send(msg)
	}
	s.terminate(reason)
}

type Server struct {
	port     string
	greeting string
	sessions map[string]*session
}

func NewServer(port string, greeting string) Server {
	return Server{port, greeting, map[string]*session{}}
}

func (s *Server) Serve() error {
	ln, err := net.Listen("tcp", ":"+s.port)
	if err != nil {
		return err
	}
	sessionLock := sync.Mutex{}
	for {
		sock, err := ln.Accept()
		if err != nil {
			return err
		}
		go func() {
			reader := bufio.NewReader(sock)

			input, err := reader.ReadString('\n')
			if err != nil {
				sock.Close()
				return
			}
			c := client{}
			c.sock = sock

			// is HELO json encoded ?
			var helo struct {
				Cmd     string
				Players []string
			}
			err = json.Unmarshal([]byte(input), &helo)
			if err == nil {
				c.encoder = json.NewEncoder(sock)
				c.decoder = json.NewDecoder(sock)
				c.encoding = "json"
				if helo.Cmd != "HELO" {
					c.fail(30, "HELO expected")
					return
				}
			} else {
				c.reader = reader
				c.writer = bufio.NewWriter(sock)
				c.encoding = "plain"

				input = strings.TrimRight(input, " \r\n")
				line := strings.Split(input, " ")
				if line[0] != "HELO" {
					c.fail(30, "HELO expected")
					return
				} else if len(line) < 2 {
					c.fail(30, "player name expected")
					return
				}
				helo.Players = line[1:]
			}
			for _, name := range helo.Players {
				c.players = append(c.players, logic.NewPlayer(name))
			}
			c.results = make(chan sMsg, len(c.players))

			c.send(sMsg{1, s.greeting})
			//names := []string{}
			//for name := range s.session {
			//names = append(names, name)
			//}
			//c.send(2, names)
			sessionLock.Lock()
			c.send(sMsg{2, &s.sessions})
			sessionLock.Unlock()
			var reg struct {
				Name       string
				MaxPlayers int
			}
			if c.encoding == "json" {
				err = c.decoder.Decode(&reg)
				if err != nil {
					c.fail(21, err)
					return
				}
			} else {
				input, err = c.reader.ReadString('\n')
				if err != nil {
					c.fail(20, err)
					return
				}
				input = strings.TrimRight(input, " \r\n")
				line := strings.Split(input, " ")
				reg.Name = line[0]
				if len(line) > 1 {
					reg.MaxPlayers, err = strconv.Atoi(line[1])
					if err != nil {
						c.fail(30, err)
						return
					}
				}
			}
			if reg.Name == "" {
				c.fail(30, "Session name expected")
				return
			}
			if reg.MaxPlayers == 0 {
				reg.MaxPlayers = 2
			}

			sessionLock.Lock()
			defer sessionLock.Unlock()
			ses, exists := s.sessions[reg.Name]
			if !exists || ses.status == "TERMINATED" {
				ses = &session{[]*client{}, reg.MaxPlayers, 0, "OPEN"}
				s.sessions[reg.Name] = ses
			}
			if ses.curPlayers+len(c.players) > ses.maxPlayers {
				c.fail(91, ses.maxPlayers-ses.curPlayers)
				return
			}
			ses.addClient(&c)
		}()
	}
	return nil
}