dotenv multi logic

src/index.ts

@@ -1,4 +1,69 @@
-export function config(): Record<string, string> {
-  console.log("TEST config");
-  return { test: 'test' };
+import * as fs from 'fs';
+import * as path from 'path';
+
+import * as dotenv from 'dotenv';
+import * as dotenvExpand from 'dotenv-expand';
+import * as yn from 'yn';
+
+export interface ConfigOptions {
+  convertToBooleanPredicate?: (variable: string) => boolean;
+  convertToBoolean?: string | string[];
+  debug?: boolean;
+}
+
+export function config(options: ConfigOptions = {}): void {
+  const log = options.debug ? console.log : (() => {});
+
+  // Same logic as create-react-app for resolving env files
+  // https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/config/env.js
+  const NODE_ENV = (process.env.NODE_ENV || 'unknown').toLowerCase();
+  const appDirectory = fs.realpathSync(process.cwd());
+  const dotenvFilePath: string = path.resolve(appDirectory, '.env');
+
+  const dotenvFiles = [
+    `${ dotenvFilePath }.${ NODE_ENV }.local`,
+    `${ dotenvFilePath }.${ NODE_ENV }`,
+    NODE_ENV !== 'test' && `${ dotenvFilePath }.local`,
+    dotenvFilePath,
+  ].filter(i => i) as string[]; // this cast is safe due to the identity filter
+
+  log('Environment files to check:', dotenvFiles.join());
+
+  const propsConfigured = {};
+  dotenvFiles.forEach((dotenvFile) => {
+    if (fs.existsSync(dotenvFile)) {
+      const {parsed} = dotenvExpand(dotenv.config({path: dotenvFile, debug: options.debug || undefined }));
+      Object.assign(propsConfigured, parsed);
+    }
+  });
+
+  log('Environment variables loaded from dotenvs:', Object.keys(propsConfigured).length);
+  log('\t', propsConfigured);
+
+  const runBoolConverter: boolean = (options.convertToBooleanPredicate || options.convertToBoolean);
+  log('Environment variable boolean converter will run:', runBoolConverter());
+  if (runBoolConverter) {
+    const convertPredicate = (key: string): boolean => {
+      if (key) {
+        if (Array.isArray(options.convertToBoolean)) {
+          if (options.convertToBoolean.includes(key)) {
+            return true;
+          }
+        } else if (options.convertToBoolean === key) {
+          return true;
+        }
+        if (typeof options.convertToBooleanPredicate === 'function' && options.convertToBooleanPredicate(key)) {
+          return true;
+        }
+      }
+      return false;
+    }
+    Object.entries(process.env).forEach(([key, value]) => {
+      if (convertPredicate(key)) {
+        const boolValue = yn(value) ? 'true' : '';
+        process.env[key] = boolValue;
+        log('Environment variable converted into string boolean value:', key, "original:", value, 'newValue:', boolValue);
+      }
+    });
+  }
 }