Make system messages deletable

// FREEBIE

Signal/src/ViewControllers/ConversationView/MessagesViewController.m

@@ -2671,6 +2671,22 @@ typedef enum : NSUInteger {
     }
 }
 
+- (void)didLongPressSystemMessageCell:(OWSSystemMessageCell *)systemMessageCell;
+{
+    OWSAssert([NSThread isMainThread]);
+    OWSAssert(systemMessageCell);
+    OWSAssert(systemMessageCell.interaction);
+
+    DDLogDebug(@"%@ long pressed system message cell: %@", self.tag, systemMessageCell);
+
+    [systemMessageCell becomeFirstResponder];
+
+    UIMenuController *theMenu = [UIMenuController sharedMenuController];
+
+    [theMenu setTargetRect:systemMessageCell.titleLabel.frame inView:systemMessageCell];
+    [theMenu setMenuVisible:YES animated:YES];
+}
+
 #pragma mark - ContactEditingDelegate
 
 - (void)didFinishEditingContact

Signal/src/views/OWSSystemMessageCell.h

@@ -8,10 +8,12 @@
 NS_ASSUME_NONNULL_BEGIN
 
 @class TSInteraction;
+@class OWSSystemMessageCell;
 
 @protocol OWSSystemMessageCellDelegate <NSObject>
 
 - (void)didTapSystemMessageWithInteraction:(TSInteraction *)interaction;
+- (void)didLongPressSystemMessageCell:(OWSSystemMessageCell *)systemMessageCell;
 
 @end
 
@@ -21,6 +23,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (nonatomic, weak) id<OWSSystemMessageCellDelegate> systemMessageCellDelegate;
 
+@property (nonatomic, readonly) UILabel *titleLabel;
 @property (nonatomic, nullable, readonly) TSInteraction *interaction;
 
 - (void)configureWithInteraction:(TSInteraction *)interaction;

Signal/src/views/OWSSystemMessageCell.m

@@ -72,6 +72,10 @@ NS_ASSUME_NONNULL_BEGIN
     UITapGestureRecognizer *tap =
         [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTapGesture:)];
     [self addGestureRecognizer:tap];
+
+    UILongPressGestureRecognizer *longpress =
+        [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongpressGesture:)];
+    [self addGestureRecognizer:longpress];
 }
 
 + (NSString *)cellReuseIdentifier
@@ -290,6 +294,21 @@ NS_ASSUME_NONNULL_BEGIN
     self.interaction = nil;
 }
 
+#pragma mark - editing
+
+- (BOOL)canBecomeFirstResponder
+{
+    return YES;
+}
+
+- (void)delete:(nullable id)sender
+{
+    DDLogInfo(@"%@ chose delete", self.logTag);
+    OWSAssert(self.interaction);
+
+    [self.interaction remove];
+}
+
 #pragma mark - Gesture recognizers
 
 - (void)handleTapGesture:(UITapGestureRecognizer *)tap
@@ -299,6 +318,26 @@ NS_ASSUME_NONNULL_BEGIN
     [self.systemMessageCellDelegate didTapSystemMessageWithInteraction:self.interaction];
 }
 
+- (void)handleLongpressGesture:(UILongPressGestureRecognizer *)longpress
+{
+    OWSAssert(self.interaction);
+    if (longpress.state == UIGestureRecognizerStateBegan) {
+        [self.systemMessageCellDelegate didLongPressSystemMessageCell:self];
+    }
+}
+
+#pragma mark - Logging
+
++ (NSString *)logTag
+{
+    return [NSString stringWithFormat:@"[%@]", self.class];
+}
+
+- (NSString *)logTag
+{
+    return self.class.logTag;
+}
+
 @end
 
 NS_ASSUME_NONNULL_END