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README.md

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+# To-Do App
+
+This is a sample to-do application for use in the PXL containers course.
+
+## Tech Stack
+
+The stack represents a combination of a JavaScript-based backend (Node.js with Express), a modern frontend framework (React), database technologies (SQLite and MySQL), and containerization (Docker), making it a comprehensive example for full-stack development and deployment.
+
+The technology stack includes:
+
+- __Node.js__: The backend application is built using Node.js, a JavaScript runtime environment that executes JavaScript code outside a web browser.
+
+- __Express.js__: This is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It is used to create the server and handle HTTP requests.
+
+- __React.js__: The frontend is built using React, a JavaScript library for building user interfaces. It is used to create the interactive UI components for the application.
+
+- __SQLite__: This is a C-language library that implements a small, fast, self-contained, high-reliability, full-featured, SQL database engine. SQLite is used as one of the database options for the application.
+
+- __MySQL__: This is a popular open-source relational database management system. In this application, MySQL is used as an alternative database option to SQLite.
+
+- __Docker__: The application is designed to be containerized using Docker, which allows for isolating the application in containers to simplify deployment and scalability.
+
+- __Bootstrap & Font Awesome__: For styling, the application uses Bootstrap, a front-end framework for developing responsive and mobile-first websites, and Font Awesome for icons.
+
+- __Jest__: This is a JavaScript testing framework used for writing tests for the application.
+
+- __Prettier__ & __ESLint__: These are code formatting and linting tools to ensure code quality and consistency.
+
+## Components
+
+- `package.json`: Defines the Node.js application's dependencies, scripts, and other configuration details.
+- `src/index.js`: The main entry point for the Node.js application. It sets up an Express server, initializes database connections, and defines routes for CRUD operations on 'todo' items.
+- Persistence Layer (`src/persistence`):
+  - `index.js`: Determines whether to use MySQL or SQLite based on the environment configuration.
+  - `mysql.js` & `sqlite.js`: Implement database operations for MySQL and SQLite, respectively.
+- Routes (`src/routes`): Contains Express route handlers for adding, deleting, retrieving, and updating 'todo' items.
+- Frontend (`src/static`):
+  - index.html: The main HTML file for the frontend.
+  - app.js: A React-based frontend script that interacts with the backend to display and manage 'todo' items.
+
+This application serves as a practical example for Docker users to understand how to containerize a simple web application using Docker.
+
+## Persistence Layer
+
+### Current Implementation in `index.js`
+
+The `index.js` file in the `src/persistence` directory currently checks for the presence of a MySQL configuration in the environment variables. If MySQL-related environment variables are set, it uses MySQL; otherwise, it defaults to SQLite. The relevant code is:
+
+```javascript
+if (process.env.MYSQL_HOST) module.exports = require('./mysql');
+else module.exports = require('./sqlite');
+```
+
+### Adaptations You Might Need
+
+1. **Environment Variables**: Ensure that the environment variables for MySQL (like `MYSQL_HOST`, `MYSQL_USER`, `MYSQL_PASSWORD`, etc.) are correctly set in your deployment environment when you want to use MySQL. If these variables are not set, the application will default to using SQLite.
+
+2. **Database Configuration Files**: The `mysql.js` and `sqlite.js` files contain the specific configurations and initialization code for each database.
+
+By adapting these aspects of the `index.js` file and related configurations, you can control which database the application uses based on your deployment environment or other conditions.

package.json

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+{
+  "name": "101-app",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "scripts": {
+    "prettify": "prettier -l --write \"**/*.js\"",
+    "test": "jest",
+    "dev": "nodemon -L src/index.js"
+  },
+  "dependencies": {
+    "express": "^4.18.2",
+    "mysql2": "^2.3.3",
+    "sqlite3": "^5.1.2",
+    "uuid": "^9.0.0",
+    "wait-port": "^1.0.4"
+  },
+  "resolutions": {
+    "ansi-regex": "5.0.1"
+  },
+  "prettier": {
+    "trailingComma": "all",
+    "tabWidth": 4,
+    "useTabs": false,
+    "semi": true,
+    "singleQuote": true
+  },
+  "devDependencies": {
+    "jest": "^29.3.1",
+    "nodemon": "^2.0.20",
+    "prettier": "^2.7.1"
+  }
+}

spec/persistence/sqlite.spec.js

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+const db = require('../../src/persistence/sqlite');
+const fs = require('fs');
+const location = process.env.SQLITE_DB_LOCATION || '/etc/todos/todo.db';
+
+const ITEM = {
+    id: '7aef3d7c-d301-4846-8358-2a91ec9d6be3',
+    name: 'Test',
+    completed: false,
+};
+
+beforeEach(() => {
+    if (fs.existsSync(location)) {
+        fs.unlinkSync(location);
+    }
+});
+
+test('it initializes correctly', async () => {
+    await db.init();
+});
+
+test('it can store and retrieve items', async () => {
+    await db.init();
+
+    await db.storeItem(ITEM);
+
+    const items = await db.getItems();
+    expect(items.length).toBe(1);
+    expect(items[0]).toEqual(ITEM);
+});
+
+test('it can update an existing item', async () => {
+    await db.init();
+
+    const initialItems = await db.getItems();
+    expect(initialItems.length).toBe(0);
+
+    await db.storeItem(ITEM);
+
+    await db.updateItem(
+        ITEM.id,
+        Object.assign({}, ITEM, { completed: !ITEM.completed }),
+    );
+
+    const items = await db.getItems();
+    expect(items.length).toBe(1);
+    expect(items[0].completed).toBe(!ITEM.completed);
+});
+
+test('it can remove an existing item', async () => {
+    await db.init();
+    await db.storeItem(ITEM);
+
+    await db.removeItem(ITEM.id);
+
+    const items = await db.getItems();
+    expect(items.length).toBe(0);
+});
+
+test('it can get a single item', async () => {
+    await db.init();
+    await db.storeItem(ITEM);
+
+    const item = await db.getItem(ITEM.id);
+    expect(item).toEqual(ITEM);
+});

spec/routes/addItem.spec.js

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+const db = require('../../src/persistence');
+const addItem = require('../../src/routes/addItem');
+const ITEM = { id: 12345 };
+const {v4 : uuid} = require('uuid');
+
+jest.mock('uuid', () => ({ v4: jest.fn() }));
+
+jest.mock('../../src/persistence', () => ({
+    removeItem: jest.fn(),
+    storeItem: jest.fn(),
+    getItem: jest.fn(),
+}));
+
+test('it stores item correctly', async () => {
+    const id = 'something-not-a-uuid';
+    const name = 'A sample item';
+    const req = { body: { name } };
+    const res = { send: jest.fn() };
+
+    uuid.mockReturnValue(id);
+
+    await addItem(req, res);
+
+    const expectedItem = { id, name, completed: false };
+
+    expect(db.storeItem.mock.calls.length).toBe(1);
+    expect(db.storeItem.mock.calls[0][0]).toEqual(expectedItem);
+    expect(res.send.mock.calls[0].length).toBe(1);
+    expect(res.send.mock.calls[0][0]).toEqual(expectedItem);
+});

spec/routes/deleteItem.spec.js

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+const db = require('../../src/persistence');
+const deleteItem = require('../../src/routes/deleteItem');
+const ITEM = { id: 12345 };
+
+jest.mock('../../src/persistence', () => ({
+    removeItem: jest.fn(),
+    getItem: jest.fn(),
+}));
+
+test('it removes item correctly', async () => {
+    const req = { params: { id: 12345 } };
+    const res = { sendStatus: jest.fn() };
+
+    await deleteItem(req, res);
+
+    expect(db.removeItem.mock.calls.length).toBe(1);
+    expect(db.removeItem.mock.calls[0][0]).toBe(req.params.id);
+    expect(res.sendStatus.mock.calls[0].length).toBe(1);
+    expect(res.sendStatus.mock.calls[0][0]).toBe(200);
+});

spec/routes/getItems.spec.js

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+const db = require('../../src/persistence');
+const getItems = require('../../src/routes/getItems');
+const ITEMS = [{ id: 12345 }];
+
+jest.mock('../../src/persistence', () => ({
+    getItems: jest.fn(),
+}));
+
+test('it gets items correctly', async () => {
+    const req = {};
+    const res = { send: jest.fn() };
+    db.getItems.mockReturnValue(Promise.resolve(ITEMS));
+
+    await getItems(req, res);
+
+    expect(db.getItems.mock.calls.length).toBe(1);
+    expect(res.send.mock.calls[0].length).toBe(1);
+    expect(res.send.mock.calls[0][0]).toEqual(ITEMS);
+});

spec/routes/updateItem.spec.js

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+const db = require('../../src/persistence');
+const updateItem = require('../../src/routes/updateItem');
+const ITEM = { id: 12345 };
+
+jest.mock('../../src/persistence', () => ({
+    getItem: jest.fn(),
+    updateItem: jest.fn(),
+}));
+
+test('it updates items correctly', async () => {
+    const req = {
+        params: { id: 1234 },
+        body: { name: 'New title', completed: false },
+    };
+    const res = { send: jest.fn() };
+
+    db.getItem.mockReturnValue(Promise.resolve(ITEM));
+
+    await updateItem(req, res);
+
+    expect(db.updateItem.mock.calls.length).toBe(1);
+    expect(db.updateItem.mock.calls[0][0]).toBe(req.params.id);
+    expect(db.updateItem.mock.calls[0][1]).toEqual({
+        name: 'New title',
+        completed: false,
+    });
+
+    expect(db.getItem.mock.calls.length).toBe(1);
+    expect(db.getItem.mock.calls[0][0]).toBe(req.params.id);
+
+    expect(res.send.mock.calls[0].length).toBe(1);
+    expect(res.send.mock.calls[0][0]).toEqual(ITEM);
+});

src/index.js

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+const express = require('express');
+const app = express();
+const db = require('./persistence');
+const getItems = require('./routes/getItems');
+const addItem = require('./routes/addItem');
+const updateItem = require('./routes/updateItem');
+const deleteItem = require('./routes/deleteItem');
+
+app.use(express.json());
+app.use(express.static(__dirname + '/static'));
+
+app.get('/items', getItems);
+app.post('/items', addItem);
+app.put('/items/:id', updateItem);
+app.delete('/items/:id', deleteItem);
+
+db.init().then(() => {
+    app.listen(3000, () => console.log('Listening on port 3000'));
+}).catch((err) => {
+    console.error(err);
+    process.exit(1);
+});
+
+const gracefulShutdown = () => {
+    db.teardown()
+        .catch(() => {})
+        .then(() => process.exit());
+};
+
+process.on('SIGINT', gracefulShutdown);
+process.on('SIGTERM', gracefulShutdown);
+process.on('SIGUSR2', gracefulShutdown); // Sent by nodemon

src/persistence/index.js

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+if (process.env.MYSQL_HOST) module.exports = require('./mysql');
+else module.exports = require('./sqlite');