package gametable

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"golang.org/x/time/rate"
	"hacklab.nilfm.cc/felt/admin"
	"hacklab.nilfm.cc/felt/models"
	"hacklab.nilfm.cc/felt/mongodb"
	"hacklab.nilfm.cc/quartzgun/auth"
	"hacklab.nilfm.cc/quartzgun/renderer"
	"io/ioutil"
	"log"
	"net/http"
	"nhooyr.io/websocket"
	"strings"
	"sync"
	"time"
)

type Subscriber struct {
	msgs      chan []byte
	closeSlow func()
}

type GameTableServer struct {
	subscribeMessageBuffer int
	publishLimiter         *rate.Limiter
	logf                   func(f string, v ...interface{})
	serveMux               http.ServeMux
	subscribersLock        sync.Mutex
	subscribers            map[*Subscriber]models.TableKey
	dbAdapter              mongodb.DbAdapter
}

func New(adapter mongodb.DbAdapter, udb auth.UserStore) *GameTableServer {
	srvr := &GameTableServer{
		subscribeMessageBuffer: 16,
		logf:                   log.Printf,
		subscribers:            make(map[*Subscriber]models.TableKey),
		publishLimiter:         rate.NewLimiter(rate.Every(time.Millisecond*100), 8),
		dbAdapter:              adapter,
	}
	srvr.serveMux.Handle("/table/", http.StripPrefix("/table/", renderer.Subtree("./static")))
	srvr.serveMux.Handle("/admin/", http.StripPrefix("/admin", admin.CreateAdminInterface(udb, adapter)))
	srvr.serveMux.HandleFunc("/subscribe", srvr.subscribeHandler)
	srvr.serveMux.HandleFunc("/publish", srvr.publishHandler)

	return srvr
}

func (self *GameTableServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	self.serveMux.ServeHTTP(w, r)
}

func (self *GameTableServer) subscribeHandler(w http.ResponseWriter, r *http.Request) {
	protocols, err := self.dbAdapter.GetProtocols()
	if err != nil {
		self.logf("%v", err)
		return
	}

	c, err := websocket.Accept(w, r, &websocket.AcceptOptions{
		Subprotocols: protocols,
	})
	if err != nil {
		self.logf("%v", err)
		return
	}
	defer c.Close(websocket.StatusInternalError, "")

	err = self.subscribe(r, c)
	if errors.Is(err, context.Canceled) {
		return
	}
	if websocket.CloseStatus(err) == websocket.StatusNormalClosure ||
		websocket.CloseStatus(err) == websocket.StatusGoingAway {
		return
	}
	if err != nil {
		self.logf("%v", err)
		return
	}
}

func (self *GameTableServer) subscribe(r *http.Request, c *websocket.Conn) error {
	ctx := r.Context()
	ctx = c.CloseRead(ctx)

	s := &Subscriber{
		msgs: make(chan []byte, self.subscribeMessageBuffer),
		closeSlow: func() {
			c.Close(websocket.StatusPolicyViolation, "connection too slow to keep up with messages")
		},
	}
	subprotoParts := strings.Split(c.Subprotocol(), ".")
	if len(subprotoParts) != 2 {
		return errors.New("Couldn't decode subprotocol")
	}
	tableKey := models.TableKey{
		Name:     subprotoParts[0],
		Passcode: subprotoParts[1],
	}

	// subprotocol is guaranteed to be an existing table, but maybe just leave this here
	if !self.dbAdapter.CheckTable(tableKey) {
		return errors.New("Table with matching key was not found on this server")
	}

	self.addSubscriber(s, tableKey)

	defer self.deleteSubscriber(s)
	select {
	case s.msgs <- self.getCurrentState(tableKey):
	default:
		go s.closeSlow()
	}

	for {
		select {
		case msg := <-s.msgs:
			err := writeTimeout(ctx, time.Second*5, c, msg)
			if err != nil {
				return err
			}
		case <-ctx.Done():
			return ctx.Err()
		}
	}
}

func (self *GameTableServer) publishHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		http.Error(w, http.StatusText(http.StatusMethodNotAllowed), http.StatusMethodNotAllowed)
		return
	}
	body := http.MaxBytesReader(w, r.Body, 8192)
	msg, err := ioutil.ReadAll(body)
	if err != nil {
		http.Error(w, http.StatusText(http.StatusRequestEntityTooLarge), http.StatusRequestEntityTooLarge)
		return
	}

	self.publish(msg)

	w.WriteHeader(http.StatusAccepted)
}

func (self *GameTableServer) publish(msg []byte) {
	self.subscribersLock.Lock()
	defer self.subscribersLock.Unlock()

	// decode message and store in DB
	tableMsg := models.TableMessage{}
	err := json.NewDecoder(bytes.NewReader(msg)).Decode(&tableMsg)
	if err != nil {
		fmt.Println(err.Error())
		return
	}

	self.writeToDB(tableMsg)

	self.publishLimiter.Wait(context.Background())

	for s, k := range self.subscribers {
		if k == *tableMsg.Key {
			select {
			case s.msgs <- msg:
			default:
				go s.closeSlow()
			}
		}
	}
}

func (self *GameTableServer) getCurrentState(tableKey models.TableKey) []byte {
	// get diceroll log, map, and token state
	if self.dbAdapter.CheckTable(tableKey) {
		mapUrl, _ := self.dbAdapter.GetMapImageUrl(tableKey)
		auxMessage, _ := self.dbAdapter.GetAuxMessage(tableKey)
		availableTokens, _ := self.dbAdapter.GetTokens(tableKey, true)
		activeTokens, _ := self.dbAdapter.GetTokens(tableKey, false)
		diceRolls, _ := self.dbAdapter.GetDiceRolls(tableKey)

		table := models.Table{
			Name:            tableKey.Name,
			Passcode:        tableKey.Passcode,
			DiceRolls:       diceRolls,
			MapImageUrl:     mapUrl,
			Tokens:          activeTokens,
			AvailableTokens: availableTokens,
			AuxMessage:      auxMessage,
		}
		data, err := json.Marshal(table)
		if err != nil {
			return []byte("{\"error\": \"" + err.Error() + "\"}")
		} else {
			return data
		}
	}
	return []byte("{\"error\": \"table not found\"}")
}

func (self *GameTableServer) writeToDB(tableMsg models.TableMessage) error {
	key := *tableMsg.Key
	if tableMsg.DiceRoll != nil {
		err := self.dbAdapter.InsertDiceRoll(key, *tableMsg.DiceRoll)
		if err != nil {
			fmt.Println(err.Error())
		}
	}
	return nil
}

func (self *GameTableServer) addSubscriber(s *Subscriber, k models.TableKey) {
	self.subscribersLock.Lock()
	self.subscribers[s] = k
	self.subscribersLock.Unlock()
}

func (self *GameTableServer) deleteSubscriber(s *Subscriber) {
	self.subscribersLock.Lock()
	delete(self.subscribers, s)
	self.subscribersLock.Unlock()
}

func writeTimeout(ctx context.Context, timeout time.Duration, c *websocket.Conn, msg []byte) error {
	ctx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	return c.Write(ctx, websocket.MessageText, msg)
}