package snakegame

import (
	"fmt"
	"net/http"
	"strconv"

	"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/games/chat"
	chatcomponents "github.com/ryanhamamura/games/chat/components"
	"github.com/ryanhamamura/games/features/snakegame/pages"
	"github.com/ryanhamamura/games/sessions"
	"github.com/ryanhamamura/games/snake"
)

func snakeChatColor(slot int) string {
	if slot >= 0 && slot < len(snake.SnakeColors) {
		return snake.SnakeColors[slot]
	}
	return "#666"
}

func snakeChatConfig(gameID string) chatcomponents.Config {
	return chatcomponents.Config{
		CSSPrefix:          "snake",
		PostURL:            fmt.Sprintf("/snake/%s/chat", gameID),
		Color:              snakeChatColor,
		StopKeyPropagation: true,
	}
}

func HandleSnakePage(snakeStore *snake.SnakeStore, sm *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 := sessions.GetPlayerID(sm, r)
		nickname := sessions.GetNickname(sm, r)
		userID := sessions.GetUserID(sm, r)

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

		mySlot := si.GetPlayerSlot(playerID)

		if mySlot < 0 {
			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, snakeChatConfig(gameID), gameID).Render(r.Context(), w); err != nil {
			http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
		}
	}
}

func HandleSnakeEvents(snakeStore *snake.SnakeStore, nc *nats.Conn, sm *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 := sessions.GetPlayerID(sm, r)
		mySlot := si.GetPlayerSlot(playerID)

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

		chatCfg := snakeChatConfig(gameID)

		// Chat room (multiplayer only)
		var room *chat.Room
		sg := si.GetGame()
		if sg.Mode == snake.ModeMultiplayer {
			room = chat.NewRoom(nc, snake.ChatSubject(gameID))
		}

		chatMessages := func() []chat.Message {
			if room == nil {
				return nil
			}
			return room.Messages()
		}

		patchAll := func() error {
			si, ok = snakeStore.Get(gameID)
			if !ok {
				return fmt.Errorf("game not found")
			}
			mySlot = si.GetPlayerSlot(playerID)
			sg = si.GetGame()
			return sse.PatchElementTempl(pages.GameContent(sg, mySlot, chatMessages(), chatCfg, gameID))
		}

		// Send initial render
		if err := patchAll(); err != nil {
			return
		}

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

		// Chat subscription (multiplayer only)
		var chatCh <-chan chat.Message
		var cleanupChat func()

		if room != nil {
			chatCh, cleanupChat = room.Subscribe()
			defer cleanupChat()
		}

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

			case <-gameCh:
				// Drain backed-up game updates
				for {
					select {
					case <-gameCh:
					default:
						goto drained
					}
				}
			drained:
				if err := patchAll(); err != nil {
					return
				}

			case chatMsg, ok := <-chatCh:
				if !ok {
					continue
				}
				err := sse.PatchElementTempl(
					chatcomponents.ChatMessage(chatMsg, chatCfg),
					datastar.WithSelectorID("snake-chat-history"),
					datastar.WithModeAppend(),
				)
				if err != nil {
					return
				}
			}
		}
	}
}

func HandleSetDirection(snakeStore *snake.SnakeStore, sm *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 := sessions.GetPlayerID(sm, 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, sm *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 := sessions.GetPlayerID(sm, r)
		slot := si.GetPlayerSlot(playerID)
		if slot < 0 {
			http.Error(w, "not in game", http.StatusForbidden)
			return
		}

		sg := si.GetGame()
		msg := chat.Message{
			Nickname: sg.Players[slot].Nickname,
			Slot:     slot,
			Message:  signals.ChatMsg,
		}

		room := chat.NewRoom(nc, snake.ChatSubject(gameID))
		room.Send(msg)

		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, sm *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
		}

		sm.Put(r.Context(), sessions.KeyNickname, signals.Nickname)

		playerID := sessions.GetPlayerID(sm, r)
		userID := sessions.GetUserID(sm, r)

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

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

func HandleRematch(snakeStore *snake.SnakeStore, sm *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
		}
	}
}