Durable Objects の SQLite で座席予約アプリを作る

import { DurableObject } from "cloudflare:workers";

export class Flight extends DurableObject {
	sql = this.ctx.storage.sql;

	constructor(ctx: DurableObjectState, env: Env) {
		super(ctx, env);
		this.initializeSeats();
	}

	private initializeSeats() {
		const cursor = this.sql.exec(`PRAGMA table_list`);

		// Check if a table exists.
		if ([...cursor].find((t) => t.name === "seats")) {
			console.log("Table already exists");
			return;
		}

		this.sql.exec(`
				  CREATE TABLE IF NOT EXISTS seats (
					seatId TEXT PRIMARY KEY,
					occupant TEXT
				  )
				`);

		// For this demo, we populate the table with 60 seats.
		// Since SQLite in DOs is fast, we can do a query per INSERT instead of batching them in a transaction.
		for (let row = 1; row <= 10; row++) {
			for (let col = 0; col < 6; col++) {
				const seatNumber = `${row}${String.fromCharCode(65 + col)}`;
				this.sql.exec(`INSERT INTO seats VALUES (?, null)`, seatNumber);
			}
		}
	}
}

import { DurableObject } from "cloudflare:workers";

export class Flight extends DurableObject {
  ...
  async fetch(request: Request): Promise<Response> {
    return new Response("Hello from Durable Object!", { status: 200 });
  }
}

export default {
	async fetch(request, env, ctx): Promise<Response> {
		// Get flight id from the query parameter
		const url = new URL(request.url);
		const flightId = url.searchParams.get("flightId");

		if (!flightId) {
			return new Response(
				"Flight ID not found. Provide flightId in the query parameter",
				{ status: 404 },
			);
		}

		const stub = env.FLIGHT.getByName(flightId);
		return stub.fetch(request);
	},
} satisfies ExportedHandler<Env>;

import { DurableObject } from "cloudflare:workers";

export class Flight extends DurableObject {
    ...

	private initializeSeats() {
		...
	}

	// Get all seats.
	getSeats() {
		let results = [];

		// Query returns a cursor.
		let cursor = this.sql.exec(`SELECT seatId, occupant FROM seats`);

		// Cursors are iterable.
		for (let row of cursor) {
			// Each row is an object with a property for each column.
			results.push({ seatNumber: row.seatId, occupant: row.occupant });
		}

		return results;
	}
}

import { DurableObject } from "cloudflare:workers";

export class Flight extends DurableObject {
	...

	private initializeSeats() {
		...
	}

	// Get all seats.
	getSeats() {
		...
	}

	// Assign a seat to a passenger.
	assignSeat(seatId: string, occupant: string) {
		// Check that seat isn't occupied.
		let cursor = this.sql.exec(
			`SELECT occupant FROM seats WHERE seatId = ?`,
			seatId,
		);
		let result = cursor.toArray()[0]; // Get the first result from the cursor.

		if (!result) {
			return {message: 'Seat not available',  status: 400 };
		}
		if (result.occupant !== null) {
			return {message: 'Seat not available',  status: 400 };
		}

		// If the occupant is already in a different seat, remove them.
		this.sql.exec(
			`UPDATE seats SET occupant = null WHERE occupant = ?`,
			occupant,
		);

		// Assign the seat. Note: We don't have to worry that a concurrent request may
		// have grabbed the seat between the two queries, because the code is synchronous
		// (no `await`s) and the database is private to this Durable Object. Nothing else
		// could have changed since we checked that the seat was available earlier!
		this.sql.exec(
			`UPDATE seats SET occupant = ? WHERE seatId = ?`,
			occupant,
			seatId,
		);

		// Broadcast the updated seats.
		this.broadcastSeats();
		return {message: `Seat ${seatId} booked successfully`, status: 200 };
	}
}

import { DurableObject } from "cloudflare:workers";

export class Flight extends DurableObject {
	...

	private initializeSeats() {
		...
	}

	// Get all seats.
	getSeats() {
		...
	}

	// Assign a seat to a passenger.
	assignSeat(seatId: string, occupant: string) {
		...
	}

  private handleWebSocket(request: Request) {
		console.log('WebSocket connection requested');
		const [client, server] = Object.values(new WebSocketPair());

		this.ctx.acceptWebSocket(server);
		console.log('WebSocket connection established');

		return new Response(null, { status: 101, webSocket: client });
	}
}

import { DurableObject } from "cloudflare:workers";

export class Flight extends DurableObject {
	...

	private initializeSeats() {
		...
	}

	// Get all seats.
	getSeats() {
		...
	}

	// Assign a seat to a passenger.
	assignSeat(seatId: string, occupant: string) {
		...
	}

  private handleWebSocket(request: Request) {
		...
	}

  private broadcastSeats() {
		this.ctx.getWebSockets().forEach((ws) => ws.send(this.getSeats()));
	}
}

import { DurableObject } from "cloudflare:workers";

export class Flight extends DurableObject {
	...

	private initializeSeats() {
		...
	}

	// Get all seats.
	getSeats() {
		...
	}

	// Assign a seat to a passenger.
	assignSeat(seatId: string, occupant: string) {
		...
	}

  private handleWebSocket(request: Request) {
		...
	}

  private broadcastSeats() {
		...
	}

  async fetch(request: Request) {
		return this.handleWebSocket(request);
	}
}

export default {
	...

	async fetch(request, env, ctx): Promise<Response> {
		// Get flight id from the query parameter
		...

		if (request.method === "GET" && url.pathname === "/seats") {
			return new Response(JSON.stringify(await stub.getSeats()), {
				headers: { 'Content-Type': 'application/json' },
			});
		} else if (request.method === "POST" && url.pathname === "/book-seat") {
			const { seatNumber, name } = (await request.json()) as {
				seatNumber: string;
				name: string;
			};
			const result = await stub.assignSeat(seatNumber, name);
			return new Response(JSON.stringify(result));
		} else if (request.headers.get("Upgrade") === "websocket") {
			return stub.fetch(request);
		}

		return new Response("Not found", { status: 404 });
	},
} satisfies ExportedHandler<Env>;