config.service.ts

config.service.ts

import dotenv from 'dotenv';
import { DeepPartial } from 'typeorm';

type Join<K, P> = K extends string | number
  ? P extends string | number
    ? `${K}${'' extends P ? '' : '.'}${P}`
    : never
  : never;
type Prev = [never, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, ...0[]];
export type Paths<T, D extends number = 10> = [D] extends [never]
  ? never
  : T extends object
  ? {
      [K in keyof T]-?: K extends string | number ? `${K}` | Join<K, Paths<T[K], Prev[D]>> : never;
    }[keyof T]
  : '';

dotenv.config();

export class Configuration {
  jwtSecret: string;
  database: {
    password: string;
    username: string;
    name: string;
    host: string;
  };
  port?: number;
}

class ConfigService {
  private config: Configuration;

  constructor() {
    this.config = {
      jwtSecret: process.env.JWT_SECRET,
      database: {
        username: process.env.DATABASE_USER,
        name: process.env.DATABASE_NAME,
        password: process.env.DATABASE_PASSWORD,
        host: process.env.DATABASE_HOST || 'localhost',
      },
      port: Number.parseInt(process.env.PORT) || 5000,
    };
  }

  getValue(key: Paths<Configuration>) {
    const keys = key.split('.');
    if (keys.length > 1) {
      let nestedObj = this.config;
      for (let nestedKey of keys) {
        nestedObj = nestedObj[nestedKey];
      }
      return nestedObj;
    }
    return this.config[key];
  }
}

export const configService = new ConfigService();

example.ts

import { configService } from 'src/config';
import { Connection, createConnection } from 'typeorm';

export const getDatabaseConnection = async (): Promise<Connection> =>
  createConnection({
    type: 'postgres',
    synchronize: true,
    port: 5432,
    host: configService.getValue('database.host'),
    username: configService.getValue('database.username'),
    password: configService.getValue('database.password'),
    database: configService.getValue('database.name'),
    entities: ['src/entities/*.entity{.ts,.js}'],
  })