feat(database): implement DatabaseService class for database operations

- Add a `DatabaseService` class to manage database interactions using `pg`'s `PoolClient`.
- Implement a `query` method to execute raw SQL queries with parameters.
- Add an `insert` method for creating new records, with support for specifying columns to return.
- Add an `update` method to modify existing records, with customizable return columns.
- Add a `delete` method to remove records, optionally returning the deleted rows.

This provides a reusable and structured way to perform database operations with enhanced maintainability and type safety.

Author: m-mdy-m

src/database/service/Databas.ts

@@ -0,0 +1,60 @@
+import { PoolClient, QueryResult, QueryResultRow } from 'pg';
+
+export class DatabaseService {
+  constructor(private _client: PoolClient) {}
+
+  /**
+   * Runs a query with parameters and returns the result.
+   */
+  async query<T extends QueryResultRow>(sql: string, params: any[] = []): Promise<QueryResult<T>> {
+    try {
+      return await this._client.query<T>(sql, params);
+    } catch (error) {
+      console.error('Database query error:', error);
+      throw error;
+    }
+  }
+
+  /**
+   * Inserts a new record and returns the inserted row.
+   */
+  async insert<T extends QueryResultRow>(tableName: string, data: Record<string, any>, returning: string[] = ['*']): Promise<T> {
+    const columns = Object.keys(data).join(', ');
+    const values = Object.values(data);
+    const placeholders = values.map((_, i) => `$${i + 1}`).join(', ');
+    const sql = `INSERT INTO "${tableName}" (${columns}) VALUES (${placeholders}) RETURNING ${returning.join(', ')};`;
+
+    const result = await this.query<T>(sql, values);
+    return result.rows[0];
+  }
+
+  /**
+   * Updates a record and returns the updated row.
+   */
+  async update<T extends QueryResultRow>(tableName: string, data: Record<string, any>, condition: Record<string, any>, returning: string[] = ['*']): Promise<T> {
+    const setClauses = Object.keys(data)
+      .map((key, i) => `"${key}" = $${i + 1}`)
+      .join(', ');
+    const whereClauses = Object.keys(condition)
+      .map((key, i) => `"${key}" = $${i + Object.keys(data).length + 1}`)
+      .join(' AND ');
+
+    const values = [...Object.values(data), ...Object.values(condition)];
+    const sql = `UPDATE "${tableName}" SET ${setClauses} WHERE ${whereClauses} RETURNING ${returning.join(', ')};`;
+    const result = await this.query<T>(sql, values);
+    return result.rows[0];
+  }
+
+  /**
+   * Deletes records and optionally returns the deleted rows.
+   */
+  async delete<T extends QueryResultRow>(tableName: string, condition: Record<string, any>, returning: string[] = ['*']): Promise<T[]> {
+    const whereClauses = Object.keys(condition)
+      .map((key, i) => `"${key}" = $${i + 1}`)
+      .join(' AND ');
+    const values = Object.values(condition);
+    const sql = `DELETE FROM "${tableName}" WHERE ${whereClauses} RETURNING ${returning.join(', ')};`;
+    const result = await this.query<T>(sql, values);
+    return result.rows;
+  }
+}