Limit caption length

// FREEBIE

Signal/src/ViewControllers/ConversationView/ConversationViewController.m

@@ -4165,6 +4165,9 @@ typedef enum : NSUInteger {
         DataSource *_Nullable dataSource = [DataSourceValue dataSourceWithOversizeText:text];
         SignalAttachment *attachment =
             [SignalAttachment attachmentWithDataSource:dataSource dataUTI:kOversizeTextAttachmentUTI];
+        // TODO we should redundantly send the first n chars in the body field so it can be viewed
+        // on clients that don't support oversized text messgaes, (and potentially generate a preview
+        // before the attachment is downloaded)
         message = [ThreadUtil sendMessageWithAttachment:attachment
                                                inThread:self.thread
                                        quotedReplyModel:self.inputToolbar.quotedReply

SignalMessaging/attachments/AttachmentApprovalViewController.swift

@@ -609,19 +609,26 @@ class CaptioningToolbar: UIView, UITextViewDelegate {
     // MARK: - UITextViewDelegate
 
     public func textViewDidChange(_ textView: UITextView) {
-        // compute new height assuming width is unchanged
-        let currentSize = textView.frame.size
-        let newHeight = clampedTextViewHeight(fixedWidth: currentSize.width)
-
-        if newHeight != self.textViewHeight {
-            Logger.debug("\(self.logTag) TextView height changed: \(self.textViewHeight) -> \(newHeight)")
-            self.textViewHeight = newHeight
-            self.textViewHeightConstraint?.constant = textViewHeight
-            self.invalidateIntrinsicContentSize()
-        }
+        updateHeight(textView: textView)
     }
 
     public func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
+
+        // Limit caption character count. We do this in characters, not bytes.
+        // This character limit will be safely below our byte limit (16k) for almost all uses.
+        // Because the captioning interface doesn't allow newlines, in practice design pressures users to leave relatively short captions.
+        let maxCharacterCount = 2000
+        guard textView.text.count + text.count - range.length <= maxCharacterCount else {
+            // Accept as much of the input as we can
+            let remainingSpace = maxCharacterCount - textView.text.count
+            if (remainingSpace) > 0 {
+                let acceptableAddition = text.substring(to: text.startIndex.advanced(by: remainingSpace))
+                textView.text = "\(textView.text ?? "")\(acceptableAddition)"
+                updateHeight(textView: textView)
+            }
+            return false
+        }
+
         // Though we can wrap the text, we don't want to encourage multline captions, plus a "done" button
         // allows the user to get the keyboard out of the way while in the attachment approval view.
         if text == "\n" {
@@ -642,6 +649,19 @@ class CaptioningToolbar: UIView, UITextViewDelegate {
 
     // MARK: - Helpers
 
+    private func updateHeight(textView: UITextView) {
+        // compute new height assuming width is unchanged
+        let currentSize = textView.frame.size
+        let newHeight = clampedTextViewHeight(fixedWidth: currentSize.width)
+
+        if newHeight != self.textViewHeight {
+            Logger.debug("\(self.logTag) TextView height changed: \(self.textViewHeight) -> \(newHeight)")
+            self.textViewHeight = newHeight
+            self.textViewHeightConstraint?.constant = textViewHeight
+            self.invalidateIntrinsicContentSize()
+        }
+    }
+
     private func clampedTextViewHeight(fixedWidth: CGFloat) -> CGFloat {
         let contentSize = textView.sizeThatFits(CGSize(width: fixedWidth, height: CGFloat.greatestFiniteMagnitude))
         return Clamp(contentSize.height, kMinTextViewHeight, maxTextViewHeight)

SignalServiceKit/src/Messages/Interactions/TSOutgoingMessage.m

@@ -4,6 +4,7 @@
 
 #import "TSOutgoingMessage.h"
 #import "NSDate+OWS.h"
+#import "OWSMessageSender.h"
 #import "OWSOutgoingSyncMessage.h"
 #import "OWSSignalServiceProtos.pb.h"
 #import "ProtoBuf+OWS.h"
@@ -415,7 +416,19 @@ NSString *const kTSOutgoingMessageSentRecipientAll = @"kTSOutgoingMessageSentRec
     
     OWSSignalServiceProtosDataMessageBuilder *builder = [OWSSignalServiceProtosDataMessageBuilder new];
     [builder setTimestamp:self.timestamp];
-    [builder setBody:self.body];
+    
+    
+    if ([self.body lengthOfBytesUsingEncoding:NSUTF8StringEncoding] <= kOversizeTextMessageSizeThreshold) {
+        [builder setBody:self.body];
+    } else {
+        OWSFail(@"%@ message body length too long.", self.logTag);
+        NSMutableString *truncatedBody = [self.body mutableCopy];
+        while ([truncatedBody lengthOfBytesUsingEncoding:NSUTF8StringEncoding] > kOversizeTextMessageSizeThreshold) {
+            DDLogError(@"%@ truncating body which is too long: %tu", self.logTag, [truncatedBody lengthOfBytesUsingEncoding:NSUTF8StringEncoding]);
+            truncatedBody = [truncatedBody substringToIndex:truncatedBody.length / 2];
+        }
+        [builder setBody:truncatedBody];
+    }
     [builder setExpireTimer:self.expiresInSeconds];
     
     // Group Messages