feat: Support data: URIs as config values (#202)

Adds support for automatic decoding of `data:` URIs as a means of making encoded data and `.env` unfriendly values easier to work with.

packages/celest/lib/celest.dart

@@ -14,7 +14,7 @@ export 'src/auth/auth.dart';
 export 'src/auth/auth_provider.dart';
 
 /// Config
-export 'src/config/env.dart';
+export 'src/config/config_values.dart';
 
 /// Core
 export 'src/core/annotations.dart';

packages/celest/lib/src/auth/auth_provider.dart

@@ -1,4 +1,4 @@
-import 'package:celest/src/config/env.dart';
+import 'package:celest/src/config/config_values.dart';
 
 /// {@template celest.auth.auth_provider}
 /// An authentication provider which can be used to sign in to Celest.

packages/celest/lib/src/config/env.dart → packages/celest/lib/src/config/config_values.dart

@@ -7,9 +7,37 @@ sealed class ConfigurationValue implements ContextKey<String> {
   /// The name of the configuration value in the environment.
   final String name;
 
+  String _decodeValue(String value) {
+    if (!value.startsWith('data:')) {
+      return value;
+    }
+    final data = UriData.parse(value);
+    if (data.isBase64) {
+      return data.contentText;
+    } else {
+      return data.contentAsString();
+    }
+  }
+
   @override
   String? read(Context context) {
-    return context[this] as String? ?? context.platform.environment[name];
+    if (rawValue(context) case final rawValue?) {
+      return _decodeValue(rawValue);
+    }
+    return null;
+  }
+
+  /// Reads the raw value for `this` from the given [context].
+  ///
+  /// Unlike [read], this will not decode `data:` URIs.
+  String? rawValue(Context context) {
+    if (context[this] case final value?) {
+      return value as String;
+    }
+    if (context.platform.environment[name] case final platformValue?) {
+      return platformValue;
+    }
+    return null;
   }
 
   @override

packages/celest/lib/src/core/context.dart

@@ -1,7 +1,7 @@
 import 'dart:async';
 import 'dart:io' show HandshakeException, HttpClient, SocketException;
 
-import 'package:celest/src/config/env.dart';
+import 'package:celest/src/config/config_values.dart';
 import 'package:celest/src/core/environment.dart';
 import 'package:celest/src/runtime/gcp/gcp.dart';
 import 'package:celest_core/_internal.dart';

packages/celest/lib/src/runtime/http/environment.dart

@@ -1,7 +1,7 @@
 import 'dart:convert';
 import 'dart:io';
 
-import 'package:celest/src/config/env.dart';
+import 'package:celest/src/config/config_values.dart';
 import 'package:celest/src/core/context.dart';
 import 'package:celest_core/_internal.dart';
 import 'package:logging/logging.dart';

packages/celest/test/config/config_values_test.dart

@@ -0,0 +1,80 @@
+import 'package:celest/src/config/config_values.dart';
+import 'package:celest/src/core/context.dart';
+import 'package:platform/platform.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('ConfigurationValue', () {
+    const key = env('ENV_VAR');
+
+    test('from platform', () {
+      context.put(
+        ContextKey.platform,
+        FakePlatform(
+          environment: {
+            'ENV_VAR': 'value',
+          },
+        ),
+      );
+      expect(context.get(key), 'value');
+      expect(key.rawValue(context), 'value');
+    });
+
+    test('from runtime', () {
+      const value = 'Hello World';
+      context.put(key, value);
+      expect(context.get(key), value);
+    });
+
+    group('data URIs', () {
+      test('plaintext', () {
+        context.put(
+          ContextKey.platform,
+          FakePlatform(
+            environment: {
+              'ENV_VAR': 'data:,Hello%20World',
+            },
+          ),
+        );
+        expect(context.get(key), 'Hello World');
+        expect(
+          key.rawValue(context),
+          'data:,Hello%20World',
+          reason: 'rawValue does not decode data URIs',
+        );
+      });
+
+      test('base64', () {
+        context.put(
+          ContextKey.platform,
+          FakePlatform(
+            environment: {
+              'ENV_VAR': 'data:text/plain;base64,SGVsbG8gV29ybGQ=',
+            },
+          ),
+        );
+        expect(
+          context.get(key),
+          'SGVsbG8gV29ybGQ=',
+          reason: 'base64-encoded values are not decoded',
+        );
+        expect(
+          key.rawValue(context),
+          'data:text/plain;base64,SGVsbG8gV29ybGQ=',
+          reason: 'rawValue does not decode data URIs',
+        );
+      });
+
+      test('can set at runtime', () {
+        final value = Uri.dataFromString('Hello World').toString();
+        context.put(key, value);
+        expect(context.get(key), 'Hello World');
+        expect(
+          key.rawValue(context),
+          value,
+          reason: 'rawValue does not decode data URIs',
+        );
+      });
+    });
+  });
+}