Interactively autoincrement list when commenting

MessageViewController.xcodeproj/project.pbxproj

@@ -25,6 +25,8 @@
 		29CC29491FF81F1F006B6DE7 /* String+WordAtRange.swift in Sources */ = {isa = PBXBuildFile; fileRef = 29CC29451FF42687006B6DE7 /* String+WordAtRange.swift */; };
 		38199E112022792600ADFE76 /* NSAttributedString+ReplaceRange.swift in Sources */ = {isa = PBXBuildFile; fileRef = 38199E102022792600ADFE76 /* NSAttributedString+ReplaceRange.swift */; };
 		38D26FB12023D01900B2B7B5 /* NSAttributedString+HighlightingTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 38D26FB02023D01900B2B7B5 /* NSAttributedString+HighlightingTests.swift */; };
+		6ED7A797206FD89E00B11C0E /* InteractiveTextFormatter.swift in Sources */ = {isa = PBXBuildFile; fileRef = 6ED7A796206FD89E00B11C0E /* InteractiveTextFormatter.swift */; };
+		6ED7A799206FD8F600B11C0E /* InteractiveTextFormatterTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 6ED7A798206FD8F600B11C0E /* InteractiveTextFormatterTests.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -58,6 +60,8 @@
 		29CC29461FF42687006B6DE7 /* UIView+iOS11.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "UIView+iOS11.swift"; sourceTree = "<group>"; };
 		38199E102022792600ADFE76 /* NSAttributedString+ReplaceRange.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "NSAttributedString+ReplaceRange.swift"; sourceTree = "<group>"; };
 		38D26FB02023D01900B2B7B5 /* NSAttributedString+HighlightingTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "NSAttributedString+HighlightingTests.swift"; sourceTree = "<group>"; };
+		6ED7A796206FD89E00B11C0E /* InteractiveTextFormatter.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = InteractiveTextFormatter.swift; sourceTree = "<group>"; };
+		6ED7A798206FD8F600B11C0E /* InteractiveTextFormatterTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = InteractiveTextFormatterTests.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -114,6 +118,7 @@
 				2904821E1FED90340053978C /* UITextView+Prefixes.swift */,
 				38199E102022792600ADFE76 /* NSAttributedString+ReplaceRange.swift */,
 				29CC29461FF42687006B6DE7 /* UIView+iOS11.swift */,
+				6ED7A796206FD89E00B11C0E /* InteractiveTextFormatter.swift */,
 			);
 			path = MessageViewController;
 			sourceTree = "<group>";
@@ -125,6 +130,7 @@
 				29CC293A1FF4266D006B6DE7 /* MessageViewControllerTests.swift */,
 				29CC29431FF4267F006B6DE7 /* String+WordAtRangeTests.swift */,
 				38D26FB02023D01900B2B7B5 /* NSAttributedString+HighlightingTests.swift */,
+				6ED7A798206FD8F600B11C0E /* InteractiveTextFormatterTests.swift */,
 			);
 			path = MessageViewControllerTests;
 			sourceTree = "<group>";
@@ -246,6 +252,7 @@
 				290482261FED90340053978C /* UIButton+BottomHeightOffset.swift in Sources */,
 				290482251FED90340053978C /* MessageViewDelegate.swift in Sources */,
 				290482201FED90340053978C /* MessageViewController.swift in Sources */,
+				6ED7A797206FD89E00B11C0E /* InteractiveTextFormatter.swift in Sources */,
 				29CC29481FF42687006B6DE7 /* UIView+iOS11.swift in Sources */,
 				29792B151FFAE7FC007A0C57 /* MessageAutocompleteController.swift in Sources */,
 				38199E112022792600ADFE76 /* NSAttributedString+ReplaceRange.swift in Sources */,
@@ -261,6 +268,7 @@
 			files = (
 				29CC293B1FF4266D006B6DE7 /* MessageViewControllerTests.swift in Sources */,
 				38D26FB12023D01900B2B7B5 /* NSAttributedString+HighlightingTests.swift in Sources */,
+				6ED7A799206FD8F600B11C0E /* InteractiveTextFormatterTests.swift in Sources */,
 				29CC29441FF4267F006B6DE7 /* String+WordAtRangeTests.swift in Sources */,
 				29CC29491FF81F1F006B6DE7 /* String+WordAtRange.swift in Sources */,
 			);

MessageViewController/InteractiveTextFormatter.swift

@@ -0,0 +1,44 @@
+//
+//  InteractiveTextFormatter.swift
+//  MessageViewController
+//
+//  Created by Viktoras Laukevičius on 31/03/2018.
+//  Copyright © 2018 Ryan Nystrom. All rights reserved.
+//
+
+import Foundation
+
+private extension NSAttributedString {
+    func replacingCharactersWithReplacementsBeginning(in range: NSRange, with: String, attributes: [NSAttributedStringKey : Any]) -> (NSAttributedString, Int) {
+        let attrStr = self.replacingCharacters(in: range, with: NSAttributedString(string: with, attributes: attributes))
+        return (attrStr, range.upperBound + with.count)
+    }
+}
+
+internal final class InteractiveTextFormatter {
+
+    func applying(change: String, in attrText: NSAttributedString, in range: NSRange) -> (NSAttributedString, Int)? {
+        // currently supports only if a single (new line) character is typed
+        guard change == "\n" else { return nil }
+
+        let rangeBegin = attrText.string.index(attrText.string.startIndex, offsetBy: range.lowerBound)
+        let textUpToChangeLoc = attrText.string.prefix(upTo: rangeBegin)
+        guard let lastLine = textUpToChangeLoc.components(separatedBy: "\n").last, lastLine.count != 0 else { return nil }
+
+        // it's safe to get attributes of text at specified location because
+        // not empty components list ensures that the text is not empty
+        let textAttrs = attrText.attributes(at: range.lowerBound - 1, effectiveRange: nil)
+
+        if let unorderedPrefix = ["* ", "- ", "+ "].first(where: lastLine.starts) {
+            return attrText.replacingCharactersWithReplacementsBeginning(in: range, with: "\n\(unorderedPrefix)", attributes: textAttrs)
+        } else if let candidate = lastLine.components(separatedBy: " ").first, candidate.hasSuffix("."), let intVal = Int(candidate.prefix(candidate.count - 1)) {
+            guard intVal &+ 1 > intVal else {
+                // wow, someone created a really long list
+                return nil
+            }
+            return attrText.replacingCharactersWithReplacementsBeginning(in: range, with: "\n\(intVal + 1). ", attributes: textAttrs)
+        } else {
+            return nil
+        }
+    }
+}

MessageViewController/MessageTextView.swift

@@ -19,6 +19,8 @@ open class MessageTextView: UITextView, UITextViewDelegate {
 
     private var listeners: NSHashTable<AnyObject> = NSHashTable.weakObjects()
 
+    private let interactiveFormatter = InteractiveTextFormatter()
+
     open override var delegate: UITextViewDelegate? {
         get { return self }
         set {}
@@ -135,7 +137,15 @@ open class MessageTextView: UITextView, UITextViewDelegate {
 
     public func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
         enumerateListeners { $0.willChangeRange(textView: self, to: range) }
-        return true
+
+        if let (newAttrText, insertionEnd) = interactiveFormatter.applying(change: text, in: textView.attributedText, in: range) {
+            textView.attributedText = newAttrText
+            let selectionPos = textView.position(from: textView.beginningOfDocument, offset: insertionEnd) ?? textView.beginningOfDocument
+            textView.selectedTextRange = textView.textRange(from: selectionPos, to: selectionPos)
+            return false
+        } else {
+            return true
+        }
     }
 
 }

MessageViewControllerTests/InteractiveTextFormatterTests.swift

@@ -0,0 +1,100 @@
+//
+//  InteractiveTextFormatterTests.swift
+//  MessageViewControllerTests
+//
+//  Created by Viktoras Laukevičius on 31/03/2018.
+//  Copyright © 2018 Ryan Nystrom. All rights reserved.
+//
+
+import XCTest
+@testable import MessageViewController
+
+private func generateList(withDelimiter d: String) -> String {
+    return "\(d) Item A\n\(d) Item B"
+}
+
+class InteractiveTextFormatterTests: XCTestCase {
+
+    var formatter: InteractiveTextFormatter!
+
+    override func setUp() {
+        super.setUp()
+        formatter = InteractiveTextFormatter()
+    }
+
+    override func tearDown() {
+        formatter = nil
+        super.tearDown()
+    }
+
+    func test_continuesNumberedList_whenAtTheEnd() {
+        let str = "1. Item A\n2. Item B"
+        let attrStr = NSAttributedString(string: str)
+        let text = formatter.applying(change: "\n", in: attrStr, in: NSRange(location: str.count, length: 0))?.0
+        XCTAssertEqual(text?.string, "\(str)\n3. ")
+    }
+
+    func test_ignoresIncrement_whenReallyLongList() {
+        let maxInt = Int.max
+        let str = "\(maxInt - 1). Item A \n\(maxInt). Item B"
+        let attrStr = NSAttributedString(string: str)
+        let text = formatter.applying(change: "\n", in: attrStr, in: NSRange(location: str.count, length: 0))?.0
+        XCTAssertNil(text)
+    }
+
+    func test_continuesNumberedList_whenInTheMiddle() {
+        let str1 = "1. Item A \n2. Item B"
+        let str2 = "\nContinues..."
+        let attrStr = NSAttributedString(string: "\(str1)\(str2)")
+        let text = formatter.applying(change: "\n", in: attrStr, in: NSRange(location: str1.count, length: 0))?.0
+        XCTAssertEqual(text?.string, "\(str1)\n3. \(str2)")
+    }
+
+    func test_continuesList_whenUsedAsterisks() {
+        let str = generateList(withDelimiter: "*")
+        let text = formatter.applying(change: "\n", in: NSAttributedString(string: str), in: NSRange(location: str.count, length: 0))?.0
+        XCTAssertEqual(text?.string, "\(str)\n* ")
+    }
+
+    func test_continuesList_whenUsedMinuses() {
+        let str = generateList(withDelimiter: "-")
+        let text = formatter.applying(change: "\n", in: NSAttributedString(string: str), in: NSRange(location: str.count, length: 0))?.0
+        XCTAssertEqual(text?.string, "\(str)\n- ")
+    }
+
+    func test_continuesList_whenUsedPuses() {
+        let str = generateList(withDelimiter: "+")
+        let text = formatter.applying(change: "\n", in: NSAttributedString(string: str), in: NSRange(location: str.count, length: 0))?.0
+        XCTAssertEqual(text?.string, "\(str)\n+ ")
+    }
+
+    func test_preservesAttributes_whenTextPrefilled() {
+        let str = generateList(withDelimiter: "-")
+        let attrs: [NSAttributedStringKey : AnyHashable] = [NSAttributedStringKey.baselineOffset : 3]
+        let attrStr = NSAttributedString(string: str, attributes: attrs)
+        let text = formatter.applying(change: "\n", in: attrStr, in: NSRange(location: str.count, length: 0))?.0
+        let resultAttrs = text?.attributes(at: str.count + 2, effectiveRange: nil) as? [NSAttributedStringKey : AnyHashable]
+        XCTAssertEqual(resultAttrs!, attrs)
+    }
+
+    func test_adjustsSelectionPosition_whenTextAppended() {
+        let str = generateList(withDelimiter: "-")
+        let selectionBeginning = formatter.applying(change: "\n", in: NSAttributedString(string: str), in: NSRange(location: str.count, length: 0))?.1
+        let appended = "\n- "
+        XCTAssertEqual(selectionBeginning, str.count + appended.count)
+    }
+
+    func test_adjustsSelectionPosition_whenTextInserted() {
+        let str1 = generateList(withDelimiter: "-")
+        let str2 = "\nContinues..."
+        let selectionBeginning = formatter.applying(change: "\n", in: NSAttributedString(string: "\(str1)\(str2)"), in: NSRange(location: str1.count, length: 0))?.1
+        let inserted = "\n- "
+        XCTAssertEqual(selectionBeginning, str1.count + inserted.count)
+    }
+
+    func test_notContinuesList_whenLineNotListItem() {
+        let str = generateList(withDelimiter: "-") + "\nContinues..."
+        let text = formatter.applying(change: "\n", in: NSAttributedString(string: str), in: NSRange(location: str.count, length: 0))?.0
+        XCTAssertNil(text)
+    }
+}