Merge pull request #187 from atsign-foundation/exception_handling_cha…

…nges

Add AtExceptionStack

at_commons/lib/at_commons.dart

@@ -5,6 +5,9 @@ export 'package:at_commons/src/at_message.dart';
 export 'package:at_commons/src/buffer/at_buffer.dart';
 export 'package:at_commons/src/buffer/at_buffer_impl.dart';
 export 'package:at_commons/src/compaction/at_compaction_config.dart';
+export 'package:at_commons/src/exception/at_client_exceptions.dart';
+export 'package:at_commons/src/exception/at_exception_manager.dart';
+export 'package:at_commons/src/exception/at_exception_stack.dart';
 export 'package:at_commons/src/exception/at_exception_utils.dart';
 export 'package:at_commons/src/exception/at_exceptions.dart'
     hide

at_commons/lib/src/exception/at_client_exceptions.dart

@@ -5,29 +5,65 @@ class AtClientException extends AtException {
   AtClientException(errorCode, message) : super(message);
 
   /// The named constructor that takes only message
-  AtClientException.message(message) : super(message);
+  AtClientException.message(message,
+      {Intent? intent, ExceptionScenario? exceptionScenario})
+      : super(message, intent: intent, exceptionScenario: exceptionScenario);
 }
 
 class AtKeyException extends AtClientException {
-  AtKeyException(message) : super.message(message);
+  AtKeyException(message,
+      {Intent? intent, ExceptionScenario? exceptionScenario})
+      : super.message(message,
+            intent: intent, exceptionScenario: exceptionScenario);
 }
 
 class AtValueException extends AtClientException {
-  AtValueException(message) : super.message(message);
+  AtValueException(message,
+      {Intent? intent, ExceptionScenario? exceptionScenario})
+      : super.message(message,
+            intent: intent, exceptionScenario: exceptionScenario);
 }
 
 class AtEncryptionException extends AtClientException {
-  AtEncryptionException(message) : super.message(message);
+  AtEncryptionException(message,
+      {Intent? intent, ExceptionScenario? exceptionScenario})
+      : super.message(message,
+            intent: intent, exceptionScenario: exceptionScenario);
 }
 
 class AtPublicKeyChangeException extends AtEncryptionException {
-  AtPublicKeyChangeException(message) : super(message);
+  AtPublicKeyChangeException(message,
+      {Intent? intent, ExceptionScenario? exceptionScenario})
+      : super(message, intent: intent, exceptionScenario: exceptionScenario);
 }
 
 class AtPublicKeyNotFoundException extends AtEncryptionException {
-  AtPublicKeyNotFoundException(message) : super(message);
+  AtPublicKeyNotFoundException(message,
+      {Intent? intent, ExceptionScenario? exceptionScenario})
+      : super(message, intent: intent, exceptionScenario: exceptionScenario);
 }
 
 class AtDecryptionException extends AtClientException {
-  AtDecryptionException(message) : super.message(message);
+  AtDecryptionException(message,
+      {Intent? intent, ExceptionScenario? exceptionScenario})
+      : super.message(message,
+            intent: intent, exceptionScenario: exceptionScenario);
+}
+
+class AtPrivateKeyNotFoundException extends AtDecryptionException {
+  AtPrivateKeyNotFoundException(message,
+      {Intent? intent, ExceptionScenario? exceptionScenario})
+      : super(message, intent: intent, exceptionScenario: exceptionScenario);
+}
+
+class SharedKeyNotFoundException extends AtDecryptionException {
+  SharedKeyNotFoundException(message,
+      {Intent? intent, ExceptionScenario? exceptionScenario})
+      : super(message, intent: intent, exceptionScenario: exceptionScenario);
+}
+
+class SelfKeyNotFoundException extends AtDecryptionException {
+  SelfKeyNotFoundException(message,
+      {Intent? intent, ExceptionScenario? exceptionScenario})
+      : super(message, intent: intent, exceptionScenario: exceptionScenario);
 }

at_commons/lib/src/exception/at_exception_manager.dart

@@ -0,0 +1,15 @@
+import 'package:at_commons/at_commons.dart';
+
+/// AtExceptionManager is responsible for creating instances of the appropriate exception
+/// classes for a given exception scenario.
+class AtExceptionManager {
+  static AtException createException(AtException atException) {
+    // If the instance of atException is AtClientException. return as is.
+    if (atException is AtClientException) {
+      return atException;
+    }
+    // Else wrap the atException into AtClientException and return.
+    return (AtClientException.message(atException.message))..fromException(atException);
+
+  }
+}

at_commons/lib/src/exception/at_exception_stack.dart

@@ -0,0 +1,63 @@
+import 'dart:collection';
+
+import 'package:at_commons/src/exception/at_exceptions.dart';
+
+/// Class to maintain stack of exceptions to form a chained exception.
+class AtExceptionStack implements Comparable<AtChainedException> {
+  final _exceptionList = Queue<AtChainedException>();
+
+  void add(AtChainedException atChainedException) {
+    if (compareTo(atChainedException) == 0) {
+      return;
+    }
+    _exceptionList.addFirst(atChainedException);
+  }
+
+  /// Concatenate the error messages in the exceptionList and returns a trace message
+  String getTraceMessage() {
+    var size = _exceptionList.length;
+    String fullMessage = '';
+    fullMessage =
+        '${getIntentMessage(_exceptionList.first.intent)} caused by\n';
+    for (AtChainedException element in _exceptionList) {
+      size--;
+      fullMessage += element.message;
+      if (size != 0) {
+        fullMessage += ' caused by\n';
+      }
+    }
+    return fullMessage;
+  }
+
+  /// Accepts the Intent and returns a message
+  String getIntentMessage(Intent intent) {
+    if (intent == Intent.fetchData) {
+      return 'Failed to fetch data';
+    }
+    if (intent == Intent.shareData) {
+      return 'Failed to share data';
+    }
+    if(intent == Intent.decryptData) {
+      return 'Failed to decrypt the data';
+    }
+    return 'Failed to notify data';
+  }
+
+  @override
+  int compareTo(AtChainedException atChainedException) {
+    for (var element in _exceptionList) {
+      if (element.message == atChainedException.message) {
+        return 0;
+      }
+    }
+    return 1;
+  }
+}
+
+class AtChainedException {
+  late Intent intent;
+  late ExceptionScenario exceptionScenario;
+  late String message;
+
+  AtChainedException(this.intent, this.exceptionScenario, this.message);
+}

at_commons/lib/src/exception/at_exceptions.dart

@@ -1,3 +1,4 @@
+import 'package:at_commons/src/exception/at_exception_stack.dart';
 import 'package:at_commons/src/keystore/at_key.dart';
 
 /// The class [AtException] and its subclasses represents various exceptions that can arise
@@ -7,12 +8,35 @@ class AtException implements Exception {
   /// Represents error message that details the cause of the exception
   var message;
 
-  AtException(this.message);
+  Intent? intent;
+
+  ExceptionScenario? exceptionScenario;
+
+  AtExceptionStack _traceStack = AtExceptionStack();
+
+  AtException(this.message, {this.intent, this.exceptionScenario}) {
+    if (intent != null && exceptionScenario != null) {
+      _traceStack.add(AtChainedException(intent!, exceptionScenario!, message));
+    }
+  }
+
+  AtException fromException(AtException atException) {
+    _traceStack = atException._traceStack;
+    return atException;
+  }
 
   @override
   String toString() {
     return 'Exception: $message';
   }
+
+  void stack(AtChainedException atChainedException) {
+    _traceStack.add(atChainedException);
+  }
+
+  String getTraceMessage() {
+    return _traceStack.getTraceMessage();
+  }
 }
 
 /// The class [AtConnectException] and its subclasses represent any issues that prevents an connection to the root or the secondary server
@@ -157,3 +181,35 @@ class InvalidRequestException extends AtException {
 class InvalidResponseException extends AtException {
   InvalidResponseException(message) : super(message);
 }
+
+enum ExceptionScenario {
+  noNetworkConnectivity,
+  rootServerNotReachable,
+  secondaryServerNotReachable,
+  invalidValueProvided,
+  valueExceedingBufferLimit,
+  noNamespaceProvided,
+  invalidKeyFormed,
+  invalidMetadataProvided,
+  keyNotFound,
+  encryptionFailed,
+  decryptionFailed,
+  remoteVerbExecutionFailed,
+  localVerbExecutionFailed,
+  atSignDoesNotExist,
+  fetchEncryptionKeys
+}
+
+enum Intent {
+  shareData,
+  fetchData,
+  validateKey,
+  validateAtSign,
+  remoteVerbExecution,
+  notifyData,
+  decryptData,
+  fetchEncryptionPublicKey,
+  fetchEncryptionPrivateKey,
+  fetchEncryptionSharedKey,
+  fetchSelfEncryptionKey
+}

at_commons/lib/src/validators/at_key_validation_impl.dart

@@ -198,7 +198,7 @@ class KeyOwnershipValidation extends Validation {
     if ((type != KeyType.cachedPublicKey && type != KeyType.cachedSharedKey) &&
         owner != atSign) {
       return ValidationResult(
-          'Owner of the key $owner should be same as current @sign atSign');
+          'Owner of the key $owner should be same as current @sign $atSign');
     }
     return ValidationResult.noFailure();
   }