package snakegame

import (
	"encoding/json"
	"net/http"
	"strconv"
	"sync"

	"github.com/alexedwards/scs/v2"
	"github.com/go-chi/chi/v5"
	"github.com/nats-io/nats.go"
	"github.com/starfederation/datastar-go/datastar"

	"github.com/ryanhamamura/c4/features/snakegame/components"
	"github.com/ryanhamamura/c4/features/snakegame/pages"
	"github.com/ryanhamamura/c4/game"
	"github.com/ryanhamamura/c4/snake"
)

func getPlayerID(sessions *scs.SessionManager, r *http.Request) snake.PlayerID {
	pid := sessions.GetString(r.Context(), "player_id")
	if pid == "" {
		pid = game.GenerateID(8)
		sessions.Put(r.Context(), "player_id", pid)
	}
	userID := sessions.GetString(r.Context(), "user_id")
	if userID != "" {
		return snake.PlayerID(userID)
	}
	return snake.PlayerID(pid)
}

func HandleSnakePage(snakeStore *snake.SnakeStore, sessions *scs.SessionManager) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		gameID := chi.URLParam(r, "id")
		si, ok := snakeStore.Get(gameID)
		if !ok {
			http.Redirect(w, r, "/", http.StatusSeeOther)
			return
		}

		playerID := getPlayerID(sessions, r)
		nickname := sessions.GetString(r.Context(), "nickname")
		userID := sessions.GetString(r.Context(), "user_id")

		// Auto-join if nickname exists and not already in game
		if nickname != "" && si.GetPlayerSlot(playerID) < 0 {
			player := &snake.Player{
				ID:       playerID,
				Nickname: nickname,
			}
			if userID != "" {
				player.UserID = &userID
			}
			si.Join(player)
		}

		mySlot := si.GetPlayerSlot(playerID)

		if mySlot < 0 {
			// Not in game yet
			isGuest := r.URL.Query().Get("guest") == "1"
			if userID == "" && !isGuest {
				if err := pages.JoinPage(gameID).Render(r.Context(), w); err != nil {
					http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
				}
				return
			}
			if err := pages.NicknamePage(gameID).Render(r.Context(), w); err != nil {
				http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
			}
			return
		}

		sg := si.GetGame()
		if err := pages.GamePage(sg, mySlot, nil, gameID).Render(r.Context(), w); err != nil {
			http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
		}
	}
}

func HandleSnakeEvents(snakeStore *snake.SnakeStore, nc *nats.Conn, sessions *scs.SessionManager) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		gameID := chi.URLParam(r, "id")
		si, ok := snakeStore.Get(gameID)
		if !ok {
			http.Error(w, "game not found", http.StatusNotFound)
			return
		}

		playerID := getPlayerID(sessions, r)
		mySlot := si.GetPlayerSlot(playerID)

		sse := datastar.NewSSE(w, r, datastar.WithCompression(
			datastar.WithBrotli(datastar.WithBrotliLevel(5)),
		))

		// Send initial render
		sg := si.GetGame()
		sse.PatchElementTempl(components.Board(sg))                        //nolint:errcheck
		sse.PatchElementTempl(components.StatusBanner(sg, mySlot, gameID)) //nolint:errcheck
		sse.PatchElementTempl(components.PlayerList(sg, mySlot))           //nolint:errcheck
		if sg.Mode == snake.ModeMultiplayer {
			sse.PatchElementTempl(components.Chat(nil, gameID)) //nolint:errcheck
			if sg.Status == snake.StatusWaitingForPlayers || sg.Status == snake.StatusCountdown {
				sse.PatchElementTempl(components.InviteLink(gameID)) //nolint:errcheck
			}
		}

		// Subscribe to game updates via NATS
		gameCh := make(chan *nats.Msg, 64)
		gameSub, err := nc.ChanSubscribe("snake."+gameID, gameCh)
		if err != nil {
			return
		}
		defer gameSub.Unsubscribe() //nolint:errcheck

		// Chat subscription (multiplayer only)
		var chatCh chan *nats.Msg
		var chatSub *nats.Subscription
		var chatMessages []components.ChatMessage
		var chatMu sync.Mutex

		if sg.Mode == snake.ModeMultiplayer {
			chatCh = make(chan *nats.Msg, 64)
			chatSub, err = nc.ChanSubscribe("snake.chat."+gameID, chatCh)
			if err != nil {
				return
			}
			defer chatSub.Unsubscribe() //nolint:errcheck
		}

		ctx := r.Context()
		for {
			select {
			case <-ctx.Done():
				return

			case <-gameCh:
				// Drain backed-up game updates
				for {
					select {
					case <-gameCh:
					default:
						goto drained
					}
				}
			drained:
				si, ok = snakeStore.Get(gameID)
				if !ok {
					return
				}
				mySlot = si.GetPlayerSlot(playerID)
				sg = si.GetGame()
				if err := sse.PatchElementTempl(components.Board(sg)); err != nil {
					return
				}
				if err := sse.PatchElementTempl(components.StatusBanner(sg, mySlot, gameID)); err != nil {
					return
				}
				if err := sse.PatchElementTempl(components.PlayerList(sg, mySlot)); err != nil {
					return
				}

			case msg := <-chatCh:
				if msg == nil {
					continue
				}
				var cm components.ChatMessage
				if err := json.Unmarshal(msg.Data, &cm); err != nil {
					continue
				}
				chatMu.Lock()
				chatMessages = append(chatMessages, cm)
				if len(chatMessages) > 50 {
					chatMessages = chatMessages[len(chatMessages)-50:]
				}
				msgs := make([]components.ChatMessage, len(chatMessages))
				copy(msgs, chatMessages)
				chatMu.Unlock()

				if err := sse.PatchElementTempl(components.Chat(msgs, gameID)); err != nil {
					return
				}
			}
		}
	}
}

func HandleSetDirection(snakeStore *snake.SnakeStore, sessions *scs.SessionManager) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		gameID := chi.URLParam(r, "id")
		si, ok := snakeStore.Get(gameID)
		if !ok {
			http.Error(w, "game not found", http.StatusNotFound)
			return
		}

		playerID := getPlayerID(sessions, r)
		slot := si.GetPlayerSlot(playerID)
		if slot < 0 {
			http.Error(w, "not in game", http.StatusForbidden)
			return
		}

		dStr := r.URL.Query().Get("d")
		d, err := strconv.Atoi(dStr)
		if err != nil || d < 0 || d > 3 {
			http.Error(w, "invalid direction", http.StatusBadRequest)
			return
		}

		si.SetDirection(slot, snake.Direction(d))
		w.WriteHeader(http.StatusOK)
	}
}

type chatSignals struct {
	ChatMsg string `json:"chatMsg"`
}

func HandleSendChat(snakeStore *snake.SnakeStore, nc *nats.Conn, sessions *scs.SessionManager) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		gameID := chi.URLParam(r, "id")
		si, ok := snakeStore.Get(gameID)
		if !ok {
			http.Error(w, "game not found", http.StatusNotFound)
			return
		}

		var signals chatSignals
		if err := datastar.ReadSignals(r, &signals); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}

		if signals.ChatMsg == "" {
			return
		}

		playerID := getPlayerID(sessions, r)
		slot := si.GetPlayerSlot(playerID)
		if slot < 0 {
			http.Error(w, "not in game", http.StatusForbidden)
			return
		}

		sg := si.GetGame()
		cm := components.ChatMessage{
			Nickname: sg.Players[slot].Nickname,
			Slot:     slot,
			Message:  signals.ChatMsg,
		}
		data, err := json.Marshal(cm)
		if err != nil {
			return
		}
		nc.Publish("snake.chat."+gameID, data) //nolint:errcheck

		sse := datastar.NewSSE(w, r)
		sse.MarshalAndPatchSignals(map[string]any{"chatMsg": ""}) //nolint:errcheck
	}
}

type nicknameSignals struct {
	Nickname string `json:"nickname"`
}

func HandleSetNickname(snakeStore *snake.SnakeStore, sessions *scs.SessionManager) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		gameID := chi.URLParam(r, "id")
		si, ok := snakeStore.Get(gameID)
		if !ok {
			http.Error(w, "game not found", http.StatusNotFound)
			return
		}

		var signals nicknameSignals
		if err := datastar.ReadSignals(r, &signals); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}

		if signals.Nickname == "" {
			return
		}

		sessions.Put(r.Context(), "nickname", signals.Nickname)

		playerID := getPlayerID(sessions, r)
		userID := sessions.GetString(r.Context(), "user_id")

		if si.GetPlayerSlot(playerID) < 0 {
			player := &snake.Player{
				ID:       playerID,
				Nickname: signals.Nickname,
			}
			if userID != "" {
				player.UserID = &userID
			}
			si.Join(player)
		}

		sse := datastar.NewSSE(w, r)
		sse.Redirect("/snake/" + gameID) //nolint:errcheck
	}
}

func HandleRematch(snakeStore *snake.SnakeStore, sessions *scs.SessionManager) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		gameID := chi.URLParam(r, "id")
		si, ok := snakeStore.Get(gameID)
		if !ok {
			http.Error(w, "game not found", http.StatusNotFound)
			return
		}

		newSI := si.CreateRematch()
		sse := datastar.NewSSE(w, r)
		if newSI != nil {
			sse.Redirect("/snake/" + newSI.ID()) //nolint:errcheck
		}
	}
}