Add configurable with functions

Add more tests for call functions and fixed

example/example.dart

@@ -1,3 +1,15 @@
+import 'package:configurable/dotenv_configuration_provider.dart';
+import 'package:configurable/simple_configuration_provider.dart';
+
 void main() {
-  print('Example');
+  var key = 'app.name';
+  var value = 'CUBETIQ Solution';
+
+  // in-memory provider (built-in)
+  var simpleProvider = SimpleConfigurationProvider();
+
+  // dotenv provider (from file .env)
+  var dotenvProvider = DotenvConfigurationProvider();
+
+  
 }

lib/configurable.dart

@@ -0,0 +1,9 @@
+library configurable;
+
+import 'package:configurable/system_config.dart';
+
+String? getConfigOrNull(String key, {String? defaultValue}) =>
+    SystemConfig.getOrNull(key, defaultValue: defaultValue);
+String getConfig(String key, {String? defaultValue}) =>
+    SystemConfig.get(key, defaultValue: defaultValue);
+bool hasConfigkey(String key) => SystemConfig.containsKey(key);

lib/dotenv/dotenv.dart

@@ -1,52 +1,33 @@
-/// Loads environment variables from a `.env` file.
-///
-/// ## usage
-///
-/// Once you call [load], the top-level [env] map is available.
-/// You may wish to prefix the import.
-///
-///     import 'package:dotenv/dotenv.dart' show load, env;
-///
-///     void main() {
-///       load();
-///       var x = env['foo'];
-///       // ...
-///     }
-///
-/// Verify required variables are present:
-///
-///     const _requiredEnvVars = const ['host', 'port'];
-///     bool get hasEnv => isEveryDefined(_requiredEnvVars);
 library dotenv;
 
 import 'dart:io';
 
 import 'package:meta/meta.dart';
 
-part 'parser.dart';
+// load functions from parser
+part 'dotenv_parser.dart';
 
+// create in-memory variables store
 var _env = Map<String, String>.from(Platform.environment);
 
-/// A copy of [Platform.environment](dart:io) including variables loaded at runtime from a file.
+// move from platforms env with default vars
 Map<String, String> get env => _env;
 
-/// Overwrite [env] with a new writable copy of [Platform.environment](dart:io).
+// clean the env and set default from platform environment
 Map clean() => _env = Map.from(Platform.environment);
 
-/// True if all supplied variables have nonempty value; false otherwise.
-/// Differs from [containsKey](dart:core) by excluding null values.
-/// Note [load] should be called first.
+// check the variables that defined in .env or platform env
 bool isEveryDefined(Iterable<String> vars) =>
     vars.every((k) => _env[k] != null && (_env[k]?.isNotEmpty ?? false));
 
-/// Read environment variables from [filename] and add them to [env].
-/// Logs to [stderr] if [filename] does not exist.
-void load([String filename = '.env', Parser psr = const Parser()]) {
+// load file .env from project root
+void load([String filename = '.env', DotenvParser psr = const DotenvParser()]) {
   var file = File.fromUri(Uri.file(filename));
   var lines = _verify(file);
   _env.addAll(psr.parse(lines));
 }
 
+// verify file .env
 List<String> _verify(File file) {
   if (file.existsSync()) return file.readAsLinesSync();
   stderr.writeln('[dotenv] Load failed: file not found: $file');

lib/dotenv/dotenv_parser.dart

@@ -1,8 +1,6 @@
 part of dotenv;
 
-/// Creates key-value pairs from strings formatted as environment
-/// variable definitions.
-class Parser {
+class DotenvParser {
   static const _singleQuot = "'";
   static const _keyword = 'export';
 
@@ -10,11 +8,9 @@ class Parser {
   static final _surroundQuotes = RegExp(r'''^(['"])(.*)\1$''');
   static final _bashVar = RegExp(r'(?:\\)?(\$)(?:{)?([a-zA-Z_][\w]*)+(?:})?');
 
-  /// [Parser] methods are pure functions.
-  const Parser();
+  // constructor for parser
+  const DotenvParser();
 
-  /// Creates a [Map](dart:core) suitable for merging into [Platform.environment](dart:io).
-  /// Duplicate keys are silently discarded.
   Map<String, String> parse(Iterable<String> lines) {
     var out = <String, String>{};
     lines.forEach((line) {
@@ -79,7 +75,6 @@ class Parser {
 
   bool _isValid(String s) => s.isNotEmpty && s.contains('=');
 
-  /// [null] is a valid value in a Dart map, but the env var representation is empty string, not the string 'null'
   bool _has(Map<String, String> map, String key) =>
       map.containsKey(key) && map[key] != null;
 

lib/dotenv_configuration_provider.dart

@@ -1,7 +1,11 @@
 import 'package:configurable/configuration_provider.dart';
-import 'package:configurable/dotenv/dotenv.dart' show env;
+import 'package:configurable/dotenv/dotenv.dart' show env, load;
 
 class DotenvConfigurationProvider implements ConfigurationProvider {
+  DotenvConfigurationProvider() {
+    load();
+  }
+
   @override
   bool containsKey(String key) {
     return env.containsKey(key);

lib/system_config.dart

@@ -23,4 +23,6 @@ class SystemConfig {
   static String? getOrNull(String key, {String? defaultValue}) {
     return getProvider().getOrNull(key, defaultValue: defaultValue);
   }
+
+  static bool containsKey(String key) => getProvider().containsKey(key);
 }

test/config_test.dart

@@ -1,3 +1,5 @@
+import 'package:configurable/configurable.dart' show getConfigOrNull;
+import 'package:configurable/dotenv_configuration_provider.dart';
 import 'package:configurable/system_config.dart';
 import 'package:test/test.dart';
 
@@ -11,4 +13,26 @@ void main() {
     expect(value, equals(SystemConfig.getOrNull(key)));
   });
 
+  test('get system config by key with dotenv provider', () {
+    var key = 'app.name';
+    var value = 'CUBETIQ Solution';
+
+    // set dotenv provider
+    SystemConfig.setProvider(DotenvConfigurationProvider());
+
+    var result = SystemConfig.getOrNull(key);
+
+    expect(value, equals(result));
+    expect(value, equals(SystemConfig.getOrNull(key)));
+  });
+
+  test('get config by key with function', () {
+    var key = 'app.name';
+    var value = 'CUBETIQ Solution';
+
+    var result = getConfigOrNull(key, defaultValue: value);
+
+    expect(value, equals(result));
+    expect(value, equals(getConfigOrNull(key)));
+  });
 }