Simplify some more older mail error handling code

Summary: Ref T4371. We can reuse more code for this "your stuff is empty" error, now, and benefit from global rate limiting and being able to reply to arbitrary addresses.

Test Plan: Sent valid, empty, and empty-ignored email via `mail_handler.php`, got appropriate actions/errors/states.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4371

Differential Revision: https://secure.phabricator.com/D8701

src/applications/metamta/constants/MetaMTAReceivedMailStatus.php

@@ -15,6 +15,8 @@ final class MetaMTAReceivedMailStatus
   const STATUS_NO_SUCH_OBJECT       = 'err:not-found';
   const STATUS_HASH_MISMATCH        = 'err:bad-hash';
   const STATUS_UNHANDLED_EXCEPTION  = 'err:exception';
+  const STATUS_EMPTY                = 'err:empty';
+  const STATUS_EMPTY_IGNORED        = 'err:empty-ignored';
 
   public static function getHumanReadableName($status) {
     $map = array(
@@ -30,6 +32,8 @@ final class MetaMTAReceivedMailStatus
       self::STATUS_NO_SUCH_OBJECT => pht('No Such Object'),
       self::STATUS_HASH_MISMATCH => pht('Bad Address'),
       self::STATUS_UNHANDLED_EXCEPTION => pht('Unhandled Exception'),
+      self::STATUS_EMPTY => pht('Empty Mail'),
+      self::STATUS_EMPTY_IGNORED => pht('Ignored Empty Mail'),
     );
 
     return idx($map, $status, pht('Processing Exception'));

src/applications/metamta/replyhandler/PhabricatorMailReplyHandler.php

@@ -46,81 +46,38 @@ abstract class PhabricatorMailReplyHandler {
     PhabricatorMetaMTAReceivedMail $mail);
 
   public function processEmail(PhabricatorMetaMTAReceivedMail $mail) {
-    $error = $this->sanityCheckEmail($mail);
-
-    if ($error) {
-      if ($this->shouldSendErrorEmail($mail)) {
-        $this->sendErrorEmail($error, $mail);
-      }
-      return null;
-    }
+    $this->dropEmptyMail($mail);
 
     return $this->receiveEmail($mail);
   }
 
-  private function sanityCheckEmail(PhabricatorMetaMTAReceivedMail $mail) {
-    $body        = $mail->getCleanTextBody();
+  private function dropEmptyMail(PhabricatorMetaMTAReceivedMail $mail) {
+    $body = $mail->getCleanTextBody();
     $attachments = $mail->getAttachments();
 
-    if (empty($body) && empty($attachments)) {
-      return 'Empty email body. Email should begin with an !action and / or '.
-             'text to comment. Inline replies and signatures are ignored.';
+    if (strlen($body) || $attachments) {
+      return;
     }
 
-    return null;
-  }
+     // Only send an error email if the user is talking to just Phabricator.
+     // We can assume if there is only one "To" address it is a Phabricator
+     // address since this code is running and everything.
+    $is_direct_mail = (count($mail->getToAddresses()) == 1) &&
+                      (count($mail->getCCAddresses()) == 0);
 
-  /**
-   * Only send an error email if the user is talking to just Phabricator. We
-   * can assume if there is only one To address it is a Phabricator address
-   * since this code is running and everything.
-   */
-  private function shouldSendErrorEmail(PhabricatorMetaMTAReceivedMail $mail) {
-    return (count($mail->getToAddresses()) == 1) &&
-           (count($mail->getCCAddresses()) == 0);
-  }
-
-  private function sendErrorEmail($error,
-                                  PhabricatorMetaMTAReceivedMail $mail) {
-    $template = new PhabricatorMetaMTAMail();
-    $template->setSubject('Exception: unable to process your mail request');
-    $template->setBody($this->buildErrorMailBody($error, $mail));
-    $template->setRelatedPHID($mail->getRelatedPHID());
-    $phid = $this->getActor()->getPHID();
-    $handle = id(new PhabricatorHandleQuery())
-      ->setViewer($this->getActor())
-      ->withPHIDs(array($phid))
-      ->executeOne();
-    $tos = array($phid => $handle);
-    $mails = $this->multiplexMail($template, $tos, array());
-
-    foreach ($mails as $email) {
-      $email->saveAndSend();
+    if ($is_direct_mail) {
+      $status_code = MetaMTAReceivedMailStatus::STATUS_EMPTY;
+    } else {
+      $status_code = MetaMTAReceivedMailStatus::STATUS_EMPTY_IGNORED;
     }
 
-    return true;
-  }
-
-  private function buildErrorMailBody($error,
-                                      PhabricatorMetaMTAReceivedMail $mail) {
-    $original_body = $mail->getRawTextBody();
-
-    $main_body = <<<EOBODY
-Your request failed because an error was encoutered while processing it:
-
-  ERROR: {$error}
-
-  -- Original Body -------------------------------------------------------------
-
-  {$original_body}
-
-EOBODY;
-
-    $body = new PhabricatorMetaMTAMailBody();
-    $body->addRawSection($main_body);
-    $body->addReplySection($this->getReplyHandlerInstructions());
-
-    return $body->render();
+    throw new PhabricatorMetaMTAReceivedMailProcessingException(
+      $status_code,
+      pht(
+        'Your message does not contain any body text or attachments, so '.
+        'Phabricator can not do anything useful with it. Make sure comment '.
+        'text appears at the top of your message: quoted replies, inline '.
+        'text, and signatures are discarded and ignored.'));
   }
 
   public function supportsPrivateReplies() {

src/applications/metamta/storage/PhabricatorMetaMTAReceivedMail.php

@@ -108,6 +108,9 @@ final class PhabricatorMetaMTAReceivedMail extends PhabricatorMetaMTADAO {
           // Don't send an error email back in these cases, since they're
           // very unlikely to be the sender's fault.
           break;
+        case MetaMTAReceivedMailStatus::STATUS_EMPTY_IGNORED:
+          // This error is explicitly ignored.
+          break;
         default:
           $this->sendExceptionMail($ex);
           break;