Fix text editing issues on characters added right after mention link

Changelog-Fixed: Fix text editing issues on characters added right after mention link
Closes: https://github.com/damus-io/damus/issues/1375
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
Tested-by: William Casarin <jb55@jb55.com>
Signed-off-by: William Casarin <jb55@jb55.com>

damus.xcodeproj/project.pbxproj

@@ -383,6 +383,7 @@
 		BA693074295D649800ADDB87 /* UserSettingsStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = BA693073295D649800ADDB87 /* UserSettingsStore.swift */; };
 		BAB68BED29543FA3007BA466 /* SelectWalletView.swift in Sources */ = {isa = PBXBuildFile; fileRef = BAB68BEC29543FA3007BA466 /* SelectWalletView.swift */; };
 		D2277EEA2A089BD5006C3807 /* Router.swift in Sources */ = {isa = PBXBuildFile; fileRef = D2277EE92A089BD5006C3807 /* Router.swift */; };
+		D71DC1EC2A9129C3006E207C /* PostViewTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D71DC1EB2A9129C3006E207C /* PostViewTests.swift */; };
 		D78525252A7B2EA4002FA637 /* NoteContentViewTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D78525242A7B2EA4002FA637 /* NoteContentViewTests.swift */; };
 		D7DEEF2F2A8C021E00E0C99F /* NostrEventTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D7DEEF2E2A8C021E00E0C99F /* NostrEventTests.swift */; };
 		E4FA1C032A24BB7F00482697 /* SearchSettingsView.swift in Sources */ = {isa = PBXBuildFile; fileRef = E4FA1C022A24BB7F00482697 /* SearchSettingsView.swift */; };
@@ -936,6 +937,7 @@
 		BA693073295D649800ADDB87 /* UserSettingsStore.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UserSettingsStore.swift; sourceTree = "<group>"; };
 		BAB68BEC29543FA3007BA466 /* SelectWalletView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SelectWalletView.swift; sourceTree = "<group>"; };
 		D2277EE92A089BD5006C3807 /* Router.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Router.swift; sourceTree = "<group>"; };
+		D71DC1EB2A9129C3006E207C /* PostViewTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PostViewTests.swift; sourceTree = "<group>"; };
 		D78525242A7B2EA4002FA637 /* NoteContentViewTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NoteContentViewTests.swift; sourceTree = "<group>"; };
 		D7DEEF2E2A8C021E00E0C99F /* NostrEventTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NostrEventTests.swift; sourceTree = "<group>"; };
 		E4FA1C022A24BB7F00482697 /* SearchSettingsView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SearchSettingsView.swift; sourceTree = "<group>"; };
@@ -1751,6 +1753,7 @@
 				4C684A542A7E91FE005E6031 /* LongPostTests.swift */,
 				4C684A562A7FFAE6005E6031 /* UrlTests.swift */,
 				D7DEEF2E2A8C021E00E0C99F /* NostrEventTests.swift */,
+				D71DC1EB2A9129C3006E207C /* PostViewTests.swift */,
 			);
 			path = damusTests;
 			sourceTree = "<group>";
@@ -2457,6 +2460,7 @@
 				4C9B0DEE2A65A75F00CBDA21 /* AttrStringTestExtensions.swift in Sources */,
 				4C19AE552A5D977400C90DB7 /* HashtagTests.swift in Sources */,
 				3A3040ED29A5CB86008A0F29 /* ReplyDescriptionTests.swift in Sources */,
+				D71DC1EC2A9129C3006E207C /* PostViewTests.swift in Sources */,
 				3AAC7A022A60FE72002B50DF /* LocalizationUtilTests.swift in Sources */,
 				D7DEEF2F2A8C021E00E0C99F /* NostrEventTests.swift in Sources */,
 				4C8D00D429E3C5D40036AF10 /* NIP19Tests.swift in Sources */,

damus/Views/PostView.swift

@@ -204,6 +204,8 @@ struct PostView: View {
             TextViewWrapper(attributedText: $post, postTextViewCanScroll: $postTextViewCanScroll, cursorIndex: newCursorIndex, getFocusWordForMention: { word, range in
                 focusWordAttributes = (word, range)
                 self.newCursorIndex = nil
+            }, updateCursorPosition: { newCursorIndex in
+                self.newCursorIndex = newCursorIndex
             })
                 .environmentObject(tagModel)
                 .focused($focus)

damus/Views/TextViewWrapper.swift

@@ -14,6 +14,7 @@ struct TextViewWrapper: UIViewRepresentable {
     
     let cursorIndex: Int?
     var getFocusWordForMention: ((String?, NSRange?) -> Void)? = nil
+    let updateCursorPosition: ((Int) -> Void)
     
     func makeUIView(context: Context) -> UITextView {
         let textView = UITextView()
@@ -34,11 +35,11 @@ struct TextViewWrapper: UIViewRepresentable {
 
     func updateUIView(_ uiView: UITextView, context: Context) {
         uiView.isScrollEnabled = postTextViewCanScroll
-        let range = uiView.selectedRange
         uiView.attributedText = attributedText
 
         TextViewWrapper.setTextProperties(uiView)
         setCursorPosition(textView: uiView)
+        let range = uiView.selectedRange
 
         uiView.selectedRange = NSRange(location: range.location + tagModel.diff, length: range.length)
         tagModel.diff = 0
@@ -52,16 +53,18 @@ struct TextViewWrapper: UIViewRepresentable {
     }
 
     func makeCoordinator() -> Coordinator {
-        Coordinator(attributedText: $attributedText, getFocusWordForMention: getFocusWordForMention)
+        Coordinator(attributedText: $attributedText, getFocusWordForMention: getFocusWordForMention, updateCursorPosition: updateCursorPosition)
     }
 
     class Coordinator: NSObject, UITextViewDelegate {
         @Binding var attributedText: NSMutableAttributedString
         var getFocusWordForMention: ((String?, NSRange?) -> Void)? = nil
+        let updateCursorPosition: ((Int) -> Void)
 
-        init(attributedText: Binding<NSMutableAttributedString>, getFocusWordForMention: ((String?, NSRange?) -> Void)?) {
+        init(attributedText: Binding<NSMutableAttributedString>, getFocusWordForMention: ((String?, NSRange?) -> Void)?, updateCursorPosition: @escaping ((Int) -> Void)) {
             _attributedText = attributedText
             self.getFocusWordForMention = getFocusWordForMention
+            self.updateCursorPosition = updateCursorPosition
         }
 
         func textViewDidChange(_ textView: UITextView) {
@@ -96,6 +99,65 @@ struct TextViewWrapper: UIViewRepresentable {
             }
             return NSRange(location: startOffset, length: length)
         }
+
+        // This `UITextViewDelegate` method is automatically called by the editor when edits occur, to check whether a change should occur
+        // We will use this method to manually handle edits concerning mention ("@") links, to avoid manual text edits to attributed mention links
+        func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
+            guard let attributedString = textView.attributedText else {
+                return true     // If we cannot get an attributed string, just fail gracefully and allow changes
+            }
+            var mutable = NSMutableAttributedString(attributedString: attributedString)
+            
+            let entireRange = NSRange(location: 0, length: attributedString.length)
+            var shouldAllowChange = true
+            var performEditActionManually = false
+
+            attributedString.enumerateAttribute(.link, in: entireRange, options: []) { (value, linkRange, stop) in
+                guard value != nil else {
+                    return  // This range is not a link. Skip checking.
+                }
+                
+                if range.contains(linkRange.upperBound) && range.contains(linkRange.lowerBound) {
+                    // Edit range engulfs all of this link's range.
+                    // This link will naturally disappear, so no work needs to be done in this range.
+                    return
+                }
+                else if linkRange.intersection(range) != nil {
+                    // If user tries to change an existing link directly, remove the link attribute
+                    mutable.removeAttribute(.link, range: linkRange)
+                    // Perform action manually to flush above changes to the view, and to prevent the character being added from having an attributed link property
+                    performEditActionManually = true
+                    return
+                }
+                else if range.location == linkRange.location + linkRange.length && range.length == 0 {
+                    // If we are inserting a character at the right edge of a link, UITextInput tends to include the new character inside the link.
+                    // Therefore, we need to manually append that character outside of the link
+                    performEditActionManually = true
+                    return
+                }
+            }
+            
+            if performEditActionManually {
+                shouldAllowChange = false
+                addUnattributedText(text, to: &mutable, inRange: range)
+                attributedText = mutable
+                
+                // Move caret to the end of the newly changed text.
+                updateCursorPosition(range.location + text.count)
+            }
+
+            return shouldAllowChange
+        }
+
+        func addUnattributedText(_ text: String, to attributedString: inout NSMutableAttributedString, inRange range: NSRange) {
+            if range.length == 0 {
+                attributedString.insert(NSAttributedString(string: text, attributes: nil), at: range.location)
+            }
+            else {
+                attributedString.replaceCharacters(in: range, with: text)
+            }
+        }
+        
     }
 }
 

damusTests/PostViewTests.swift

@@ -0,0 +1,143 @@
+//
+//  PostViewTests.swift
+//  damusTests
+//
+//  Created by Daniel D’Aquino on 2023-08-19.
+//
+import Foundation
+import XCTest
+@testable import damus
+import SwiftUI
+
+final class PostViewTests: XCTestCase {
+    
+    override func setUpWithError() throws {
+        // Put setup code here. This method is called before the invocation of each test method in the class.
+    }
+    
+    override func tearDownWithError() throws {
+        // Put teardown code here. This method is called after the invocation of each test method in the class.
+    }
+    
+    /// Based on https://github.com/damus-io/damus/issues/1375
+    /// Tests whether the editor properly handles mention links after they have been added, to avoid manual editing of attributed links
+    func testMentionLinkEditorHandling() throws {
+        var content: NSMutableAttributedString
+
+        // Test normal insertion
+        checkMentionLinkEditorHandling(content: NSMutableAttributedString(string: "Hello"), replacementText: "@", replacementRange: NSRange(location: 0, length: 0), shouldBeAbleToChangeAutomatically: true)
+        checkMentionLinkEditorHandling(content: NSMutableAttributedString(string: "Hello "), replacementText: "@", replacementRange: NSRange(location: 6, length: 0), shouldBeAbleToChangeAutomatically: true)
+        checkMentionLinkEditorHandling(content: NSMutableAttributedString(string: "Helo "), replacementText: "l", replacementRange: NSRange(location: 3, length: 0), shouldBeAbleToChangeAutomatically: true)
+        
+        // Test normal backspacing
+        checkMentionLinkEditorHandling(content: NSMutableAttributedString(string: "Hello"), replacementText: "", replacementRange: NSRange(location: 5, length: 1), shouldBeAbleToChangeAutomatically: true)
+        checkMentionLinkEditorHandling(content: NSMutableAttributedString(string: "Hello "), replacementText: "", replacementRange: NSRange(location: 6, length: 1), shouldBeAbleToChangeAutomatically: true)
+        checkMentionLinkEditorHandling(content: NSMutableAttributedString(string: "Helo "), replacementText: "", replacementRange: NSRange(location: 3, length: 1), shouldBeAbleToChangeAutomatically: true)
+
+        // Test normal insertion after mention link
+        content = NSMutableAttributedString(string: "Hello @user ")
+        content.addAttribute(.link, value: "damus:1234", range: NSRange(location: 6, length: 5))
+        checkMentionLinkEditorHandling(content: content, replacementText: "a", replacementRange: NSRange(location: 12, length: 0), shouldBeAbleToChangeAutomatically: true)
+
+        // Test insertion right at the end of a mention link, at the end of the text
+        content = NSMutableAttributedString(string: "Hello @user")
+        content.addAttribute(.link, value: "damus:1234", range: NSRange(location: 6, length: 5))
+        checkMentionLinkEditorHandling(content: content, replacementText: ",", replacementRange: NSRange(location: 11, length: 0), shouldBeAbleToChangeAutomatically: false, expectedNewCursorIndex: 12, handleNewContent: { newManuallyEditedContent in
+            XCTAssertEqual(newManuallyEditedContent.string, "Hello @user,")
+            XCTAssertNil(newManuallyEditedContent.attribute(.link, at: 11, effectiveRange: nil))
+        })
+
+        // Test insertion right at the end of a mention link, in the middle of the text
+        content = NSMutableAttributedString(string: "Hello @user how are you?")
+        content.addAttribute(.link, value: "damus:1234", range: NSRange(location: 6, length: 5))
+        checkMentionLinkEditorHandling(content: content, replacementText: ",", replacementRange: NSRange(location: 11, length: 0), shouldBeAbleToChangeAutomatically: false, expectedNewCursorIndex: 12, handleNewContent: { newManuallyEditedContent in
+            XCTAssertEqual(newManuallyEditedContent.string, "Hello @user, how are you?")
+            XCTAssertNil(newManuallyEditedContent.attribute(.link, at: 11, effectiveRange: nil))
+        })
+
+        // Test insertion in the middle of a mention link to check if the link is removed
+        content = NSMutableAttributedString(string: "Hello @user how are you?")
+        content.addAttribute(.link, value: "damus:1234", range: NSRange(location: 6, length: 5))
+        checkMentionLinkEditorHandling(content: content, replacementText: "a", replacementRange: NSRange(location: 8, length: 0), shouldBeAbleToChangeAutomatically: false, expectedNewCursorIndex: 9, handleNewContent: { newManuallyEditedContent in
+            XCTAssertEqual(newManuallyEditedContent.string, "Hello @uaser how are you?")
+            XCTAssertNil(newManuallyEditedContent.attribute(.link, at: 8, effectiveRange: nil))
+        })
+
+        // Test insertion in the middle of a mention link to check if the link is removed, at the end of the text
+        content = NSMutableAttributedString(string: "Hello @user")
+        content.addAttribute(.link, value: "damus:1234", range: NSRange(location: 6, length: 5))
+        checkMentionLinkEditorHandling(content: content, replacementText: "a", replacementRange: NSRange(location: 8, length: 0), shouldBeAbleToChangeAutomatically: false, expectedNewCursorIndex: 9, handleNewContent: { newManuallyEditedContent in
+            XCTAssertEqual(newManuallyEditedContent.string, "Hello @uaser")
+            XCTAssertNil(newManuallyEditedContent.attribute(.link, at: 8, effectiveRange: nil))
+        })
+
+        // Test backspacing right at the end of a mention link, at the end of the text
+        content = NSMutableAttributedString(string: "Hello @user")
+        content.addAttribute(.link, value: "damus:1234", range: NSRange(location: 6, length: 5))
+        checkMentionLinkEditorHandling(content: content, replacementText: "", replacementRange: NSRange(location: 10, length: 1), shouldBeAbleToChangeAutomatically: false, expectedNewCursorIndex: 10, handleNewContent: { newManuallyEditedContent in
+            XCTAssertEqual(newManuallyEditedContent.string, "Hello @use")
+            XCTAssertNil(newManuallyEditedContent.attribute(.link, at: 6, effectiveRange: nil))
+        })
+
+        // Test adding text right at the start of a mention link, to check that the link is removed
+        content = NSMutableAttributedString(string: "Hello @user")
+        content.addAttribute(.link, value: "damus:1234", range: NSRange(location: 6, length: 5))
+        checkMentionLinkEditorHandling(content: content, replacementText: "a", replacementRange: NSRange(location: 6, length: 0), shouldBeAbleToChangeAutomatically: false, expectedNewCursorIndex: 7, handleNewContent: { newManuallyEditedContent in
+            XCTAssertEqual(newManuallyEditedContent.string, "Hello a@user")
+            XCTAssertNil(newManuallyEditedContent.attribute(.link, at: 7, effectiveRange: nil))
+        })
+
+        // Test that removing one link does not affect the other
+        content = NSMutableAttributedString(string: "Hello @user1 @user2")
+        content.addAttribute(.link, value: "damus:1234", range: NSRange(location: 6, length: 6))
+        content.addAttribute(.link, value: "damus:5678", range: NSRange(location: 13, length: 6))
+        checkMentionLinkEditorHandling(content: content, replacementText: "", replacementRange: NSRange(location: 18, length: 1), shouldBeAbleToChangeAutomatically: false, expectedNewCursorIndex: 18, handleNewContent: { newManuallyEditedContent in
+            XCTAssertEqual(newManuallyEditedContent.string, "Hello @user1 @user")
+            XCTAssertNil(newManuallyEditedContent.attribute(.link, at: 13, effectiveRange: nil))
+            XCTAssertNotNil(newManuallyEditedContent.attribute(.link, at: 6, effectiveRange: nil))
+        })
+
+        // Test that replacing a whole range intersecting with two links removes both links
+        content = NSMutableAttributedString(string: "Hello @user1 @user2")
+        content.addAttribute(.link, value: "damus:1234", range: NSRange(location: 6, length: 6))
+        content.addAttribute(.link, value: "damus:5678", range: NSRange(location: 13, length: 6))
+        checkMentionLinkEditorHandling(content: content, replacementText: "a", replacementRange: NSRange(location: 10, length: 4), shouldBeAbleToChangeAutomatically: false, expectedNewCursorIndex: 11, handleNewContent: { newManuallyEditedContent in
+            XCTAssertEqual(newManuallyEditedContent.string, "Hello @useauser2")
+            XCTAssertNil(newManuallyEditedContent.attribute(.link, at: 6, effectiveRange: nil))
+            XCTAssertNil(newManuallyEditedContent.attribute(.link, at: 11, effectiveRange: nil))
+        })
+
+        // Test that replacing a whole range including two links removes both links naturally
+        content = NSMutableAttributedString(string: "Hello @user1 @user2, how are you?")
+        content.addAttribute(.link, value: "damus:1234", range: NSRange(location: 6, length: 6))
+        content.addAttribute(.link, value: "damus:5678", range: NSRange(location: 13, length: 6))
+        checkMentionLinkEditorHandling(content: content, replacementText: "", replacementRange: NSRange(location: 5, length: 28), shouldBeAbleToChangeAutomatically: true)
+        
+    }
+}
+
+func checkMentionLinkEditorHandling(
+    content: NSMutableAttributedString,
+    replacementText: String,
+    replacementRange: NSRange,
+    shouldBeAbleToChangeAutomatically: Bool,
+    expectedNewCursorIndex: Int? = nil,
+    handleNewContent: ((NSMutableAttributedString) -> Void)? = nil) {
+        let bindingContent: Binding<NSMutableAttributedString> = Binding(get: {
+            return content
+        }, set: { newValue in
+            handleNewContent?(newValue)
+        })
+        let coordinator: TextViewWrapper.Coordinator = TextViewWrapper.Coordinator(attributedText: bindingContent, getFocusWordForMention: nil, updateCursorPosition: { newCursorIndex in
+            if let expectedNewCursorIndex {
+                XCTAssertEqual(newCursorIndex, expectedNewCursorIndex)
+            }
+        })
+        let textView = UITextView()
+        textView.attributedText = content
+
+        XCTAssertEqual(coordinator.textView(textView, shouldChangeTextIn: replacementRange, replacementText: replacementText), shouldBeAbleToChangeAutomatically, "Expected shouldChangeTextIn to return \(shouldBeAbleToChangeAutomatically), but was \(!shouldBeAbleToChangeAutomatically)")
+}
+
+
+