refactor(deriv_env): make package independent of env file (#318)

* get the env file content from outside

* make Env class not being singleton

* create EnvLoader class

* fix the tests

* bring back the removed test case

* update the initialize doc

* export classes need to be used by outside

* export BaseEnv class as well

* format deriv_env.dart

* swape names for Env and EnvLoader to reduce the amount of change in the apps using this packagew

* handle exception in bool type

* remove duplicate lint rules

* define common values as variable in env_test.dart

* update README.md file

* remove breaking change by making the laod method deprecated

* Update CHANGELOG.md

* udpate README.md file

* refactor: Improve flexibility by removing dependency to env file
- **Deprecation:** The `load` method is deprecated; it is recommended to use the new `initialize` method for improved flexibility. The `load` method will still function but may be removed in future releases.
- Introduced a new method `initialize` to handle initialization without requiring an env file directly.
- Improved package flexibility by removing the strict dependency on an env file for test environments.

packages/deriv_env/README.md

@@ -31,12 +31,12 @@ You can check if the environment variable is initialized using the `isInitialize
 bool isInitialized = Env().isInitialized;
 ```
 
-### Loading environment variables
+### Initializing the Env 
 
-Before using any environment variables, you need to load them from a file. The `load` method loads the variables from a file with the specified filename (default is `.env`).
+Before using any environment variables, you need to intialize the `Env` class and pass it an instnace of the EnvLoader and the path to the file. The `initialize` method loads the variables from a file with the specified filename (default is `.env`).
 
 ```dart
-await Env().load();
+await Env().initialize(EnvLoader(filePath: '.env'));
 ```
 
 The load method expects the file to contain key-value pairs separated by an equals sign (`=`) and each pair separated by a newline character (`\n`). Blank lines and comments (lines starting with a `#`) are ignored.

packages/deriv_env/analysis_options.yaml

@@ -58,12 +58,11 @@ linter:
     - flutter_style_todos
     - hash_and_equals
     - implementation_imports
-    - iterable_contains_unrelated_type
+    - collection_methods_unrelated_type
     - join_return_with_assignment
     - library_names
     - library_prefixes
     # - lines_longer_than_80_chars
-    - list_remove_unrelated_type
     - no_adjacent_strings_in_list
     - no_duplicate_case_values
     - no_leading_underscores_for_local_identifiers

packages/deriv_env/lib/base_env.dart → packages/deriv_env/lib/base_env_loader.dart

@@ -1,16 +1,19 @@
 /// Base class for retrieve environment variables providers.
-abstract class BaseEnv {
+abstract class BaseEnvLoader {
   /// Returns `true` if [Env] is initialized, otherwise `false`.
   bool get isInitialized;
 
   /// Returns all environment variables as a [Map].
   Map<String, dynamic> get entries;
 
-  /// Loads environment variables from a `.env` file.
-  ///
-  /// If [filename] is not provided, it will default to `.env`.
-  Future<void> load([String filename = '.env']);
+  /// Loads environment variables.
+  Future<void> loadEnvironment();
 
   /// Retrieves an environment variable value by key.
-  T get<T>(String key, {T? defaultValue});
+  T get<T>(
+    String key, {
+    T? defaultValue,
+    T Function(String value)? parser,
+    String decryptionKey = '',
+  });
 }

packages/deriv_env/lib/deriv_env.dart

@@ -0,0 +1,3 @@
+export 'env.dart';
+export 'env_loader.dart';
+export 'base_env_loader.dart';

packages/deriv_env/lib/env.dart

@@ -1,114 +1,56 @@
-import 'package:flutter/services.dart';
-
-import 'base_env.dart';
-import 'cipher.dart';
-
-/// [Env] class is a singleton class that provides access to environment variables.
-class Env extends BaseEnv {
-  /// Returns the singleton instance of [Env].
-  factory Env() => _instance;
-
-  Env._();
+import 'base_env_loader.dart';
+import 'env_loader.dart';
+
+/// This class is used to load environment variables from a .env file
+class Env {
+  /// The singleton instance of [EnvLoader].
+  factory Env() {
+    _instance ??= Env._internal();
+    return _instance!;
+  }
 
-  static final Env _instance = Env._();
+  Env._internal();
 
-  bool _isInitialized = false;
+  static Env? _instance;
 
-  final Map<String, dynamic> _entries = <String, dynamic>{};
+  /// The environment variables provider.
+  BaseEnvLoader? _env;
 
-  @override
-  bool get isInitialized => _isInitialized;
+  /// The instance of [BaseEnv].
+  BaseEnvLoader? get env => _env;
 
-  @override
-  Map<String, dynamic> get entries {
-    _checkInitialization();
+  /// Returns `true` if [Env] is initialized, otherwise `false`.
+  bool get isInitialized => _env?.isInitialized ?? false;
 
-    return _entries;
+  /// Initializes [EnvLoader] with an instance of [BaseEnv].
+  /// Loads environment variables from a `.env` file.
+  ///
+  /// If [filename] is not provided, it will default to `.env`.
+  Future<void> initialize(BaseEnvLoader env) async {
+    _env = env;
+    return _env!.loadEnvironment();
   }
 
-  @override
-  Future<void> load([String filename = '.env']) async {
-    _entries.clear();
-
-    final List<String> fileEntries = await _getEntriesFromFile(filename);
-
-    for (final String entry in fileEntries) {
-      final List<String> items = entry.split('=');
-
-      if (items.length > 1) {
-        _entries[items.first.trim()] = items.sublist(1).join('=').trim();
-      }
-    }
-
-    _isInitialized = true;
+  /// Loads environment variables from a `.env` file.
+  @Deprecated('Use initialize() method instead.')
+  Future<void> load([String filePath = '.env']) async {
+    _env ??= EnvLoader(filePath: filePath);
+    return _env!.loadEnvironment();
   }
 
-  @override
+  /// Retrieves an environment variable value by key.
   T get<T>(
     String key, {
     T? defaultValue,
     T Function(String value)? parser,
     String decryptionKey = '',
-  }) {
-    _checkInitialization();
-
-    if (!_entries.containsKey(key)) {
-      if (defaultValue == null) {
-        throw Exception('$runtimeType does not contain a value for key: $key.');
-      }
-
-      return defaultValue;
-    }
-
-    final String value = decryptionKey.isEmpty
-        ? _entries[key]
-        : Cipher().decrypt(message: _entries[key], key: decryptionKey);
-
-    if (parser != null) {
-      return parser(value);
-    }
-
-    switch (T) {
-      case int:
-        return int.tryParse(value) as T;
-      case double:
-        return double.tryParse(value) as T;
-      case bool:
-        return (value.toLowerCase() == 'true') as T;
-
-      default:
-        return value as T;
-    }
-  }
-
-  Future<List<String>> _getEntriesFromFile(String filename) async {
-    final String envFileContent = await rootBundle.loadString(filename);
-
-    if (envFileContent.isEmpty) {
-      throw Exception('$runtimeType: $filename is empty.');
-    }
-
-    final List<String> entries = <String>[];
-    final List<String> content = envFileContent.split('\n');
-
-    for (final String line in content) {
-      if (line.isEmpty || line.startsWith('#')) {
-        continue;
-      }
-
-      entries.add(line);
-    }
-
-    return entries;
-  }
-
-  void _checkInitialization() {
-    if (_isInitialized) {
-      return;
-    }
-
-    throw Exception(
-      '$runtimeType is not initialized, call load() method first.',
-    );
-  }
+  }) =>
+      isInitialized
+          ? _env!.get<T>(
+              key,
+              defaultValue: defaultValue,
+              parser: parser,
+              decryptionKey: decryptionKey,
+            )
+          : throw Exception('EnvLoader is not initialized.');
 }

packages/deriv_env/lib/env_loader.dart

@@ -0,0 +1,119 @@
+import 'package:flutter/services.dart';
+
+import 'base_env_loader.dart';
+import 'cipher.dart';
+
+/// [Env] class is a singleton class that provides access to environment variables.
+class EnvLoader extends BaseEnvLoader {
+  /// Creates a new instance of [EnvLoader].
+  EnvLoader({required this.filePath});
+
+  /// The path to the file.
+  final String filePath;
+
+  bool _isInitialized = false;
+
+  final Map<String, dynamic> _entries = <String, dynamic>{};
+
+  @override
+  bool get isInitialized => _isInitialized;
+
+  @override
+  Map<String, dynamic> get entries {
+    _checkInitialization();
+
+    return _entries;
+  }
+
+  @override
+  Future<void> loadEnvironment() async {
+    _entries.clear();
+
+    final List<String> fileEntries = await _getEntriesFromFile(filePath);
+
+    for (final String entry in fileEntries) {
+      final List<String> items = entry.split('=');
+
+      if (items.length > 1) {
+        _entries[items.first.trim()] = items.sublist(1).join('=').trim();
+      }
+    }
+
+    _isInitialized = true;
+  }
+
+  @override
+  T get<T>(
+    String key, {
+    T? defaultValue,
+    T Function(String value)? parser,
+    String decryptionKey = '',
+  }) {
+    _checkInitialization();
+
+    if (!_entries.containsKey(key)) {
+      if (defaultValue == null) {
+        throw Exception('$runtimeType does not contain a value for key: $key.');
+      }
+
+      return defaultValue;
+    }
+
+    final String value = decryptionKey.isEmpty
+        ? _entries[key]
+        : Cipher().decrypt(message: _entries[key], key: decryptionKey);
+
+    if (parser != null) {
+      return parser(value);
+    }
+
+    switch (T) {
+      case int:
+        return int.tryParse(value) as T;
+      case double:
+        return double.tryParse(value) as T;
+      case bool:
+        if (value.toLowerCase() == 'true') {
+          return true as T;
+        } else if (value.toLowerCase() == 'false') {
+          return false as T;
+        } else {
+          throw FormatException('Invalid boolean value: $value');
+        }
+
+      default:
+        return value as T;
+    }
+  }
+
+  Future<List<String>> _getEntriesFromFile(String filename) async {
+    final String envFileContent = await rootBundle.loadString(filename);
+
+    if (envFileContent.isEmpty) {
+      throw Exception('$runtimeType: $filename is empty.');
+    }
+
+    final List<String> entries = <String>[];
+    final List<String> content = envFileContent.split('\n');
+
+    for (final String line in content) {
+      if (line.isEmpty || line.startsWith('#')) {
+        continue;
+      }
+
+      entries.add(line);
+    }
+
+    return entries;
+  }
+
+  void _checkInitialization() {
+    if (_isInitialized) {
+      return;
+    }
+
+    throw Exception(
+      '$runtimeType is not initialized, call load() method first.',
+    );
+  }
+}