feat: implement database module and service with PostgreSQL integration and migrations support

backend/src/database/database.module.ts

@@ -0,0 +1,10 @@
+import { Module } from "@nestjs/common";
+import { ConfigModule } from "@nestjs/config";
+import { DatabaseService } from "./database.service";
+
+@Module({
+	imports: [ConfigModule],
+	providers: [DatabaseService],
+	exports: [DatabaseService],
+})
+export class DatabaseModule {}

backend/src/database/database.service.ts

@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) 2025 Yidhra Studio. - All Rights Reserved
+ * Updated : 25/04/2025 10:52
+ *
+ * Unauthorized copying or redistribution of this file in source and binary forms via any medium
+ * is strictly prohibited.
+ */
+
+import {Injectable, Logger, OnModuleDestroy, OnModuleInit} from "@nestjs/common";
+import { ConfigService } from "@nestjs/config";
+import { drizzle } from "drizzle-orm/node-postgres";
+import { migrate } from "drizzle-orm/node-postgres/migrator";
+import * as schema from "./schemas";
+import {Pool} from "pg";
+
+@Injectable()
+export class DatabaseService implements OnModuleInit, OnModuleDestroy {
+	private readonly logger = new Logger(DatabaseService.name);
+	private readonly pool!: Pool
+	public readonly db: ReturnType<typeof drizzle>;
+
+	constructor(
+		private configService: ConfigService
+	) {
+		// Create the PostgreSQL client
+		const connectionString = this.getDatabaseConnectionString();
+		this.pool = new Pool({ connectionString });
+    	// Recreate drizzle with initialized pool
+    	this.db = drizzle(this.pool, { schema });
+
+	}
+
+	async onModuleInit() {
+		try {
+			// Run migrations if in production mode
+			if (this.configService.get("NODE_ENV") === "production") {
+				this.logger.log("Running database migrations...");
+				await migrate(this.db, { migrationsFolder: ".migrations" });
+				this.logger.log("Database migrations completed successfully");
+			} else {
+				this.logger.debug("Skipping migrations in non-production environment");
+			}
+			this.logger.log("Database connection established successfully");
+		} catch (error) {
+			this.logger.error("Failed to initialize database connection", error);
+			throw error;
+		}
+	}
+
+	async onModuleDestroy() {
+		try {
+			// Close the database connection
+			await this.pool.end();
+			this.logger.log("Database connection closed successfully");
+		} catch (error) {
+			this.logger.error("Error closing database connection", error);
+		}
+	}
+
+	// Get the database connection string from environment variables
+	private getDatabaseConnectionString(): string {
+		this.logger.debug('Getting database connection string from environment variables');
+
+		const password = this.configService.get<string>("POSTGRES_PASSWORD");
+		const username = this.configService.get<string>("POSTGRES_USER");
+		const host = this.configService.get<string>("POSTGRES_HOST");
+		const port = this.configService.get<string>("POSTGRES_PORT");
+		const database = this.configService.get<string>("POSTGRES_DB");
+
+		const missingVars: string[] = [];
+		if (!password) missingVars.push("POSTGRES_PASSWORD");
+		if (!username) missingVars.push("POSTGRES_USER");
+		if (!host) missingVars.push("POSTGRES_HOST");
+		if (!port) missingVars.push("POSTGRES_PORT");
+		if (!database) missingVars.push("POSTGRES_DB");
+
+		if (missingVars.length > 0) {
+			const errorMessage = `Database configuration is missing. Missing variables: ${missingVars.join(", ")}. Please check your .env file.`;
+			this.logger.error(errorMessage);
+			throw new Error(errorMessage);
+		}
+
+		this.logger.debug(`Database connection configured for ${username}@${host}:${port}/${database}`);
+		return `postgres://${username}:${password}@${host}:${port}/${database}`;
+	}
+}