feat(database): add database initialization and seeding functionality

- Implemented DatabaseService to initialize tables and seed data
- Added seedTables method to load and execute SQL seed data from a file
- Enhanced ConnectionPool to handle database creation if it doesn't exist
- Improved error handling in the connection process using custom decorators

Author: m-mdy-m

src/database/ConnectionPool.ts

@@ -0,0 +1,62 @@
+import { Pool, PoolClient } from 'pg';
+import Config from '../config';
+import { Catch } from '../decorators/ErrorHandlingDecorator';
+export class ConnectionPool {
+  private _pool: Pool;
+  constructor() {
+    const connectionString = this.getConnectionString();
+    this._pool = new Pool({
+      connectionString,
+    });
+  }
+  @Catch({
+    message: 'Failed to connect to the database. Please check your credentials or network connection.',
+    statusCode: 500,
+    category: 'ConnectionPool',
+  })
+  async connect(): Promise<void> {
+    try {
+      await this._pool.connect();
+    } catch (error: any) {
+      console.log('error:', error.code);
+
+      if (error.code === '3D000') {
+        console.log(`Database does not exist. Creating database ${Config.database.databaseName}...`);
+        await this.createDatabase();
+        await this._pool.end(); // End the current pool connection
+        const newConnectionString = this.getConnectionString();
+        this._pool = new Pool({
+          connectionString: newConnectionString,
+        });
+        await this._pool.connect();
+      }
+    }
+  }
+  @Catch({
+    message: 'Failed to create the database. Please check the connection or permissions.',
+    statusCode: 500,
+    category: 'ConnectionPool',
+  })
+  private async createDatabase(): Promise<void> {
+    const { user, host, password, port, databaseName } = Config.database;
+    const client = new Pool({
+      user,
+      host,
+      password,
+      port,
+      database: 'postgres',
+    });
+    await client.query(`CREATE DATABASE ${databaseName}`);
+  }
+  private getConnectionString(): string {
+    const { user, host, databaseName, password, port, url } = Config.database;
+    return url || `postgresql://${user}:${password}@${host}:${port}/${databaseName}`;
+  }
+  async getClient(): Promise<PoolClient> {
+    return this._pool.connect();
+  }
+
+  async close(): Promise<void> {
+    await this._pool.end();
+  }
+}

src/database/index.ts

@@ -0,0 +1,34 @@
+import { ConnectionPool } from './ConnectionPool';
+import * as fs from 'fs/promises';
+import * as path from 'path';
+export class DatabaseService {
+  private _connectionPool: ConnectionPool;
+
+  constructor() {
+    this._connectionPool = new ConnectionPool();
+  }
+
+  async initialize() {
+    await this._connectionPool.connect();
+    await this.setupInitialTables();
+    await this.seedTables();
+  }
+
+  private async setupInitialTables() {
+    const client = await this._connectionPool.getClient();
+    const sqlFilePath = path.join(__dirname, './tables/Tables.sql');
+    const sql = await fs.readFile(sqlFilePath, 'utf-8');
+    await client.query(sql);
+    console.log('Initial tables have been set up successfully.');
+  }
+  private async seedTables() {
+    const client = await this._connectionPool.getClient();
+    // Define the path where seed files are stored
+    const sqlFilePath = path.join(__dirname, './seed/SeedDataTables.sql');
+
+    // Get all seed files
+    const sql = await fs.readFile(sqlFilePath, 'utf-8');
+    await client.query(sql);
+    console.log('All tables have been seeded successfully.');
+  }
+}