Build layered dinosaur database API

lecture_5/.prettierrc.json

@@ -1,5 +0,0 @@
-{
-   "endOfLine": "lf",
-   "useTabs": true,
-   "printWidth": 120
-}

lecture_5/dinosaurs/.env.example

@@ -0,0 +1,6 @@
+PGHOST="localhost"
+PGPORT="5432"
+PGDATABASE="rg_academy_dev"
+PGUSER="rg_academy"
+PGPASSWORD="rg_academy"
+PORT="3000"

lecture_5/dinosaurs/.prettierrc.json

@@ -0,0 +1,5 @@
+{
+	"endOfLine": "lf",
+	"useTabs": true,
+	"printWidth": 120
+}

lecture_5/dinosaurs/dinosaurs.http

@@ -0,0 +1,11 @@
+### List all dinosaurs
+GET http://localhost:3000/dinosaurs
+
+### Get one dinosaur
+GET http://localhost:3000/dinosaurs/1
+
+### Invalid dinosaur ID
+GET http://localhost:3000/dinosaurs/not-a-number
+
+### Missing dinosaur
+GET http://localhost:3000/dinosaurs/999999

lecture_5/dinosaurs/eslint.config.js

@@ -15,6 +15,7 @@ export default defineConfig([
 		rules: {
 			indent: ["error", "tab"],
 			"linebreak-style": ["error", "unix"],
+			"no-unused-vars": ["error", { argsIgnorePattern: "^_" }],
 			quotes: ["error", "double"],
 			semi: ["error", "always"],
 		},

lecture_5/dinosaurs/old-index.js

@@ -0,0 +1,39 @@
+import "dotenv/config";
+import express from "express";
+import { Client } from "pg";
+
+// Legacy single-file implementation kept for comparison with the layered src/ structure.
+const client = new Client({
+	host: process.env.PGHOST,
+	port: Number(process.env.PGPORT),
+	database: process.env.PGDATABASE,
+	user: process.env.PGUSER,
+	password: process.env.PGPASSWORD,
+});
+
+const app = express();
+
+app.get("/dinosaurs", async (request, response) => {
+	const result = await client.query("SELECT * FROM dinosaur ORDER BY id");
+	const dinosaurs = result.rows.map((row) => ({
+		id: row.id,
+		name: row.name,
+		description: row.description,
+		period: row.period,
+		wikipediaAddress: row.wikipedia_address,
+	}));
+	response.json(dinosaurs);
+});
+
+await client.connect();
+console.log("Connected to database");
+
+app.listen(3000, () => {
+	console.log("Server running on port 3000");
+});
+
+process.on("SIGINT", async () => {
+	console.log("Shutting down...");
+	await client.end();
+	process.exit(0);
+});

lecture_5/dinosaurs/package.json

@@ -0,0 +1,23 @@
+{
+	"name": "dinosaurs",
+	"version": "1.0.0",
+	"type": "module",
+	"scripts": {
+		"start": "node src/index.js",
+		"lint": "eslint .",
+		"format": "prettier --write .",
+		"check": "npm run lint && prettier --check ."
+	},
+	"dependencies": {
+		"dotenv": "^17.4.2",
+		"express": "^5.1.0",
+		"pg": "^8.11.3"
+	},
+	"devDependencies": {
+		"@eslint/js": "^10.0.1",
+		"@eslint/json": "^1.2.0",
+		"eslint": "^10.0.0",
+		"globals": "^17.4.0",
+		"prettier": "^3.0.0"
+	}
+}

lecture_5/dinosaurs/schema.sql

@@ -1,13 +1,13 @@
 -- Dinosaur table
 CREATE TABLE dinosaur (
 	id SERIAL PRIMARY KEY,
-	name VARCHAR(256) NOT NULL,
+	name VARCHAR(256) NOT NULL UNIQUE,
 	description VARCHAR(4096) NOT NULL,
 	period VARCHAR(32) NOT NULL,
 	wikipedia_address VARCHAR(4096) NOT NULL
 );
 
--- Insert sample data into dinosaur table
+-- Seed records provide predictable data for the API exercises.
 INSERT INTO dinosaur (name, description, period, wikipedia_address)
 VALUES (
 	'Tyrannosaurus',

lecture_5/dinosaurs/src/app.js

@@ -0,0 +1,9 @@
+import express from "express";
+import { dinosaurRouter } from "./routes/dinosaurRoutes.js";
+
+const app = express();
+
+app.use(express.json());
+app.use(dinosaurRouter);
+
+export { app };

lecture_5/dinosaurs/src/db/client.js

@@ -0,0 +1,5 @@
+import "dotenv/config";
+import { Client } from "pg";
+
+// The pg client reads the standard PGHOST, PGPORT, PGDATABASE, PGUSER, and PGPASSWORD variables.
+export const client = new Client();

lecture_5/dinosaurs/src/index.js

@@ -0,0 +1,23 @@
+import { client } from "./db/client.js";
+import { app } from "./app.js";
+
+const port = Number(process.env.PORT ?? 3000);
+
+try {
+	await client.connect();
+	console.log("Connected to database");
+
+	app.listen(port, () => {
+		console.log(`Server running on http://localhost:${port}`);
+	});
+} catch (error) {
+	console.error("Failed to start the server:", error.message);
+	process.exitCode = 1;
+}
+
+// Close the database connection when the process is stopped from the terminal.
+process.on("SIGINT", async () => {
+	console.log("Shutting down...");
+	await client.end();
+	process.exit(0);
+});

lecture_5/dinosaurs/src/repositories/dinosaurRepository.js

@@ -0,0 +1,58 @@
+import { client } from "../db/client.js";
+
+/**
+ * @typedef {Object} DinosaurWithoutId
+ * @property {string} name
+ * @property {string} description
+ * @property {string} period
+ * @property {string} wikipediaAddress
+ */
+
+/**
+ * @typedef {DinosaurWithoutId} Dinosaur
+ * @property {number} id
+ */
+
+/**
+ * Converts a database row representing a dinosaur into a `Dinosaur` object.
+ *
+ * @param {Object} row
+ * @returns {Dinosaur}
+ */
+const mapRowToDinosaurDto = (row) => {
+	return {
+		id: row.id,
+		name: row.name,
+		description: row.description,
+		period: row.period,
+		wikipediaAddress: row.wikipedia_address,
+	};
+};
+
+export const dinosaurRepository = {
+	/**
+	 * Obtains all dinosaurs, ordered by ID.
+	 *
+	 * @returns {Promise<Dinosaur[]>}
+	 */
+	async listDinosaurs() {
+		const result = await client.query("SELECT * FROM dinosaur ORDER BY id");
+		return result.rows.map(mapRowToDinosaurDto);
+	},
+
+	/**
+	 * Obtains one dinosaur by its ID.
+	 *
+	 * @param {number} id
+	 * @returns {Promise<Dinosaur | null>}
+	 */
+	async getDinosaurById(id) {
+		const result = await client.query("SELECT * FROM dinosaur WHERE id = $1", [id]);
+
+		if (result.rowCount === 0) {
+			return null;
+		}
+
+		return mapRowToDinosaurDto(result.rows[0]);
+	},
+};

lecture_5/dinosaurs/src/routes/dinosaurRoutes.js

@@ -0,0 +1,31 @@
+import express from "express";
+import { dinosaurRepository } from "../repositories/dinosaurRepository.js";
+
+export const dinosaurRouter = express.Router();
+
+// Return all dinosaurs through the repository abstraction.
+dinosaurRouter.get("/dinosaurs", async (_request, response) => {
+	const dinosaurs = await dinosaurRepository.listDinosaurs();
+	response.json(dinosaurs);
+});
+
+// Return one dinosaur identified by a positive integer ID.
+dinosaurRouter.get("/dinosaurs/:id", async (request, response) => {
+	const id = Number(request.params.id);
+
+	if (!Number.isInteger(id) || id <= 0) {
+		return response.status(400).json({
+			message: "Dinosaur ID must be a positive integer",
+		});
+	}
+
+	const dinosaur = await dinosaurRepository.getDinosaurById(id);
+
+	if (dinosaur === null) {
+		return response.status(404).json({
+			message: "Dinosaur not found",
+		});
+	}
+
+	response.json(dinosaur);
+});

lecture_5/package.json

@@ -1,20 +0,0 @@
-{
-    "name": "dinosaurs",
-    "version": "1.0.0",
-    "type": "module",
-    "scripts": {
-        "start": "node index.js"
-    },
-    "dependencies": {
-        "dotenv": "^17.4.2",
-        "express": "^5.1.0",
-        "pg": "^8.11.3"
-    },
-    "devDependencies": {
-        "@eslint/js": "^10.0.1",
-        "@eslint/json": "^1.2.0",
-        "eslint": "^10.0.0",
-        "globals": "^17.4.0",
-        "prettier": "^3.0.0"
-    }
-}