Add the ability to merge attributed strings

VinCloudKit/Sources/VinCloudKit/VCKModel.swift

@@ -12,7 +12,7 @@ import OrderedCollections
 enum VCKMergeScenario {
 	case clientWins
 	case serverWins
-	case merge
+	case threeWayMerge
 
 	static func evaluate<T>(client: T?, ancestor: T?, server: T?) -> Self where T:Equatable {
 		if let ancestor {
@@ -23,7 +23,7 @@ enum VCKMergeScenario {
 			guard client != nil else { return .serverWins }
 
 			// We have all 3 values and need to do a 3 way merge
-			return .merge
+			return .threeWayMerge
 		} else {
 			if server == nil {
 				return .clientWins
@@ -54,10 +54,45 @@ public extension VCKModel {
 			return client
 		case .serverWins:
 			return server
-		case .merge:
-			#warning("This should be changed to be smart enough to merge Strings and AttributedStrings")
-			// It should be possible to merge using the raw strings and iterating over the diffs to select the attributes
-			// to create a merged NSAttributedString
+		case .threeWayMerge:
+			return client
+		}
+	}
+
+	func merge(client: Data?, ancestor: Data?, server: Data?) -> Data? {
+		switch VCKMergeScenario.evaluate(client: client, ancestor: ancestor, server: server) {
+		case .clientWins:
+			return client
+		case .serverWins:
+			return server
+		case .threeWayMerge:
+			guard let clientAttrString = client?.toAttributedString(),
+				  let serverAttrString = server?.toAttributedString(),
+				  let ancestorAttrString = ancestor?.toAttributedString() else {
+				fatalError("We should always have all 3 values for a 3 way merge.")
+			}
+
+			let diff = serverAttrString.string.difference(from: ancestorAttrString.string).inferringMoves()
+			if !diff.isEmpty {
+				let merged = NSMutableAttributedString(attributedString: clientAttrString)
+
+				for change in diff {
+					switch change {
+					case .insert(let offset, _, let associated):
+						guard offset < clientAttrString.length else { continue }
+						let serverAttrString = serverAttrString.attributedSubstring(from: NSRange(location: associated ?? offset, length: 1))
+						merged.insert(serverAttrString, at: offset)
+					case .remove(let offset, _, _):
+						guard offset < clientAttrString.length else { continue }
+						merged.deleteCharacters(in: NSRange(location: offset, length: 1))
+					}
+				}
+
+				return merged.toData()
+			} else {
+				// TODO: Merge attributes only...
+			}
+
 			return client
 		}
 	}
@@ -78,9 +113,9 @@ public extension VCKModel {
 			return client
 		case .serverWins:
 			return server
-		case .merge:
-			guard let client, let server else { fatalError("We should always have both a server or client if we are merging") }
-			let diff = server.difference(from: ancestor ?? [])
+		case .threeWayMerge:
+			guard let client, let server, let ancestor else { fatalError("We should always have all 3 values for a 3 way merge.") }
+			let diff = server.difference(from: ancestor)
 			guard let merged = client.applying(diff) else {
 				return client
 			}

VinOutlineKit/Sources/VinOutlineKit/Row.swift

@@ -173,9 +173,7 @@ public final class Row: NSObject, NSCopying, RowContainer, Codable, Identifiable
 		get {
 			guard let topic = topicData else { return nil }
 			if topicCache == nil {
-				topicCache = try? NSAttributedString(data: topic,
-													 options: [.documentType: NSAttributedString.DocumentType.rtf, .characterEncoding: String.Encoding.utf8.rawValue],
-													 documentAttributes: nil)
+				topicCache = topic.toAttributedString()
 				topicCache = replaceImages(attrString: topicCache, isNotes: false)
 			}
 			return topicCache
@@ -184,8 +182,7 @@ public final class Row: NSObject, NSCopying, RowContainer, Codable, Identifiable
 			if let attrText = newValue {
 				let (cleanAttrText, newImages) = splitOffImages(attrString: attrText, isNotes: false)
 				cleanAttrText.trimCharacters(in: .whitespaces)
-
-				topicData = try? cleanAttrText.data(from: .init(location: 0, length: cleanAttrText.length), documentAttributes: [.documentType: NSAttributedString.DocumentType.rtf])
+				topicData = cleanAttrText.toData()
 
 				var notesImages = images?.filter { $0.isInNotes ?? false } ?? [Image]()
 				notesImages.append(contentsOf: newImages)
@@ -208,9 +205,7 @@ public final class Row: NSObject, NSCopying, RowContainer, Codable, Identifiable
 		get {
 			guard let note = noteData else { return nil }
 			if noteCache == nil {
-				noteCache = try? NSAttributedString(data: note,
-													options: [.documentType: NSAttributedString.DocumentType.rtf, .characterEncoding: String.Encoding.utf8.rawValue],
-													documentAttributes: nil)
+				noteCache = note.toAttributedString()
 				noteCache = replaceImages(attrString: noteCache, isNotes: true)
 			}
 			return noteCache
@@ -219,8 +214,7 @@ public final class Row: NSObject, NSCopying, RowContainer, Codable, Identifiable
 			if let attrText = newValue {
 				let (cleanAttrText, newImages) = splitOffImages(attrString: attrText, isNotes: true)
 				cleanAttrText.trimCharacters(in: .whitespaces)
-
-				noteData = try? cleanAttrText.data(from: .init(location: 0, length: cleanAttrText.length), documentAttributes: [.documentType: NSAttributedString.DocumentType.rtf])
+				noteData = cleanAttrText.toData()
 
 				var topicImages = images?.filter { !($0.isInNotes ?? false) } ?? [Image]()
 				topicImages.append(contentsOf: newImages)

VinUtility/Sources/VinUtility/Data+VU.swift

@@ -1,8 +1,15 @@
-//
-//  File.swift
-//  
-//
+///
 //  Created by Maurice Parker on 12/4/23.
 //
 
 import Foundation
+
+public extension Data {
+
+	func toAttributedString() -> NSAttributedString? {
+		return try? NSAttributedString(data: self,
+									   options: [.documentType: NSAttributedString.DocumentType.rtf, .characterEncoding: String.Encoding.utf8.rawValue],
+									   documentAttributes: nil)
+	}
+
+}

VinUtility/Sources/VinUtility/NSAttributedString+VU.swift

@@ -4,18 +4,18 @@
 
 import Foundation
 
-extension NSAttributedString {
+public extension NSAttributedString {
 
     #if canImport(UIKit)
-	public convenience init(linkText: String, linkURL: URL) {
+	convenience init(linkText: String, linkURL: URL) {
 		let attrString = NSMutableAttributedString(string: linkText)
 		let range = NSRange(location: 0, length: attrString.length)
 		attrString.addAttribute(.link, value: linkURL, range: range)
 		self.init(attributedString: attrString)
 	}
     #endif
 
-	public static func isOptionalStringsEqual(lhs: NSAttributedString?, rhs: NSAttributedString?) -> Bool {
+	static func isOptionalStringsEqual(lhs: NSAttributedString?, rhs: NSAttributedString?) -> Bool {
 		if lhs == nil && rhs == nil {
 			return true
 		}
@@ -28,10 +28,13 @@ extension NSAttributedString {
         return lhs!.isEqual(to: rhs!)
 	}
 
-	public func trimmingCharacters(in charSet: CharacterSet) -> NSAttributedString {
+	func trimmingCharacters(in charSet: CharacterSet) -> NSAttributedString {
 		let modifiedString = NSMutableAttributedString(attributedString: self)
 	   modifiedString.trimCharacters(in: charSet)
 		return NSAttributedString(attributedString: modifiedString)
 	}
-
+
+	func toData() -> Data? {
+		return try? self.data(from: .init(location: 0, length: self.length), documentAttributes: [.documentType: NSAttributedString.DocumentType.rtf])
+	}
 }