refactor(api): handle error cases

apps/api/src/players/gateways/players.gateway.ts

@@ -17,7 +17,6 @@ import {
 	SOCKET_MOVE_PERFORMED_TOKEN,
 	type GameUpdatedPayload
 } from "@chess-d/shared";
-import { validateFen } from "chess.js";
 
 @WebSocketGateway({
 	cors: {
@@ -33,21 +32,25 @@ export class PlayersGateway
 
 	constructor(private readonly playersService: PlayersService) {}
 
-	handleConnection(@ConnectedSocket() socket: Socket) {
+	private handleError(socket: Socket, error: Error): void {
+		this.handleDisconnect(socket);
+
+		this.server.to(socket.id).emit("error", {
+			message: error.message,
+			cause: error.cause
+		});
+
+		console.warn("Error occurred:", error.message, `<${error.cause}>`);
+	}
+
+	handleConnection(@ConnectedSocket() socket: Socket): void {
 		const data = this.playersService.register(socket);
-		if (data instanceof Error) {
-			this.server
-				.to(socket.id)
-				.emit("error", { message: data.message, cause: data.cause });
-			socket.disconnect();
-			console.log(`Auto player "${socket.id}" disconnection:`, data.message);
-			return;
-		}
+		if (data instanceof Error) return this.handleError(socket, data);
 
 		const { player, roomID, room } = data;
 
 		console.log(
-			"=========/ Player connected /=========\n",
+			"\n=========/ Player connected /=========\n",
 			player,
 			`\n\nRoom "${roomID}" has ${room?.players.length} player(s).`,
 			`\nGame status "${room.fen}".`,
@@ -63,10 +66,16 @@ export class PlayersGateway
 			);
 	}
 
-	handleDisconnect(socket: Socket) {
-		const { player, room } = this.playersService.unregister(socket);
+	handleDisconnect(socket: Socket): void {
+		const unregisterRes = this.playersService.unregister(socket);
+
+		if (unregisterRes instanceof Error) return;
+
+		const { player, roomID, room } = unregisterRes;
+
+		this.server.to(player.id).disconnectSockets();
 		console.log(
-			`\nPlayer left.\nID: ${player?.id}\nTotal in rooms: ${room?.players.length ?? 0}\n`
+			`\nPlayer "${player?.id}" left room "${roomID}".\nTotal in rooms: ${room?.players.length ?? 0}`
 		);
 	}
 
@@ -75,12 +84,14 @@ export class PlayersGateway
 		@ConnectedSocket() socket: Socket,
 		@MessageBody() payload: GameUpdatedPayload
 	): void {
-		console.log("Move performed by", socket.id, payload);
+		const data = this.playersService.handleMove(socket, payload.move);
 
-		if (this.playersService.handleMove(socket, payload.move))
-			this.server
-				.in(socket.data?.roomID)
-				.except(socket.id)
-				.emit(SOCKET_MOVE_PERFORMED_TOKEN, payload);
+		if (data instanceof Error) return this.handleError(socket, data);
+
+		console.log("\nMove performed by", socket.id, payload);
+		this.server
+			.in(socket.data?.roomID)
+			.except(socket.id)
+			.emit(SOCKET_MOVE_PERFORMED_TOKEN, payload);
 	}
 }

apps/api/src/players/services/players.service.ts

@@ -3,7 +3,8 @@ import {
 	ColorSide,
 	DEFAULT_FEN,
 	getOppositeColorSide,
-	PlayerEntity
+	PlayerEntity,
+	SocketAuthInterface
 } from "@chess-d/shared";
 import { randomUUID, UUID } from "crypto";
 import { validateFen, type Move } from "chess.js";
@@ -23,15 +24,23 @@ export class PlayersService {
 				room: PlayersService["rooms"][UUID];
 		  }
 		| Error {
-		const { roomID: queryRoomID, side: colorSide } = socket.handshake.auth;
+		const {
+			roomID: queryRoomID,
+			side: colorSide,
+			fen: authFen
+		} = socket.handshake.auth as SocketAuthInterface;
+		const fen =
+			typeof authFen === "string" && validateFen(authFen)
+				? authFen
+				: DEFAULT_FEN;
 
 		let roomID: UUID | undefined;
 
 		if (
 			typeof queryRoomID === "string" &&
 			!Array.isArray(this.rooms[queryRoomID]?.players)
 		)
-			return new Error("Invalid room ID.");
+			return new Error("Invalid room ID.", { cause: "ROOM_NOT_FOUND" });
 
 		const player: PlayerEntity = {
 			id: socket.id,
@@ -42,7 +51,13 @@ export class PlayersService {
 
 		if (typeof queryRoomID === "string") {
 			if (this.rooms[queryRoomID]?.players?.length !== 1)
-				return new Error("Unable to join a room without a player or full.");
+				return new Error("Unable to join a room without a player or full.", {
+					cause: this.rooms[queryRoomID]
+						? this.rooms[queryRoomID].players.length > 1
+							? "ROOM_FULL"
+							: "ROOM_EMPTY"
+						: "ROOM_NOT_FOUND"
+				});
 
 			player.color = getOppositeColorSide(
 				this.rooms[queryRoomID].players[0].color
@@ -55,17 +70,24 @@ export class PlayersService {
 
 		if (!roomID) {
 			roomID = randomUUID();
-			this.rooms[roomID] = { fen: DEFAULT_FEN, players: [player] };
+			this.rooms[roomID] = { fen, players: [player] };
 		}
 
 		socket.data = { roomID };
 		return { player, roomID, room: this.rooms[roomID] };
 	}
 
-	unregister(socket: Socket) {
+	unregister(socket: Socket):
+		| {
+				roomID: string;
+				room: PlayersService["rooms"][UUID];
+				player: PlayerEntity;
+		  }
+		| Error {
 		const { roomID } = socket.data;
 		const room = this.rooms[roomID];
-		if (!room) return {};
+
+		if (!room) return new Error("Room not found.", { cause: "ROOM_NOT_FOUND" });
 
 		let player: PlayerEntity | undefined;
 
@@ -87,11 +109,18 @@ export class PlayersService {
 		return { roomID, room, player };
 	}
 
-	handleMove(socket: Socket, move?: Move): string | null {
+	handleMove(socket: Socket, move?: Move): string | Error {
 		if (typeof move?.after !== "string" || !validateFen(move.after))
-			return null;
+			return new Error("Invalid move.", { cause: "INVALID_MOVE" });
 
 		const roomID = socket.data?.roomID;
+		const room = this.rooms[roomID];
+
+		if (!room || room.fen !== move.before)
+			return new Error("Move desynchronized with the room fen.", {
+				cause: "DESYNCHRONIZED"
+			});
+
 		this.rooms[roomID].fen = move.after;
 
 		return this.rooms[roomID].fen;

apps/web/src/shared/hooks/use-socket.hook.ts

@@ -2,8 +2,10 @@ import { useCallback, useEffect, useMemo, useState } from "react";
 import { io, Socket } from "socket.io-client";
 import {
 	ColorSide,
+	DEFAULT_FEN,
 	PlayerEntity,
-	SOCKET_MOVE_PERFORMED_TOKEN
+	SOCKET_MOVE_PERFORMED_TOKEN,
+	SocketAuthInterface
 } from "@chess-d/shared";
 
 export const useSocket = (): {
@@ -84,8 +86,10 @@ export const useSocket = (): {
 	]);
 
 	socket.auth = {
-		roomID: new URLSearchParams(location.search).get("roomID")
-	};
+		roomID: new URLSearchParams(location.search).get("roomID"),
+		side: ColorSide.black,
+		fen: DEFAULT_FEN
+	} satisfies SocketAuthInterface;
 
 	return {
 		socket,

packages/shared/src/interfaces/index.ts

@@ -1,3 +1,4 @@
 export * from "./board.interface";
 export * from "./chess.interface";
 export * from "./reactive.interface";
+export * from "./socket.interface";

packages/shared/src/interfaces/socket.interface.ts

@@ -0,0 +1,7 @@
+import { ColorSide } from "src/enums";
+
+export interface SocketAuthInterface {
+	roomID?: string | null;
+	side?: ColorSide | null;
+	fen?: string | null;
+}