Reimplemented ObjC attributed string handling in swift.

ElementX/Sources/Other/HTMLParsing/AttributedStringBuilder.swift

@@ -11,20 +11,53 @@ import DTCoreText
 
 struct AttributedStringBuilder: AttributedStringBuilderProtocol {
     
-    private var defaultCSS: String {
-        AttributedStringBuilderUtils.cssToMarkBlockquotes() +
-"""
-        pre,code {
-            background-color: #F5F7FA;
-            display: inline;
-            font-family: monospace;
-            white-space: pre;
-            -coretext-fontname: Menlo-Regular;
+    private let temporaryBlockquoteMarkingColor = UIColor.magenta
+    private let linkColor = UIColor.blue
+    
+    private let userIdDetector: NSRegularExpression
+    private let roomIdDetector: NSRegularExpression
+    private let eventIdDetector: NSRegularExpression
+    private let groupIdDetector: NSRegularExpression
+    private let roomAliasDetector: NSRegularExpression
+    private let linkDetector: NSDataDetector
+    
+    init() {
+        do {
+            userIdDetector = try NSRegularExpression(pattern: MatrixEntityRegex.userId.rawValue, options: .caseInsensitive)
+            roomIdDetector = try NSRegularExpression(pattern: MatrixEntityRegex.roomId.rawValue, options: .caseInsensitive)
+            eventIdDetector = try NSRegularExpression(pattern: MatrixEntityRegex.eventId.rawValue, options: .caseInsensitive)
+            groupIdDetector = try NSRegularExpression(pattern: MatrixEntityRegex.groupId.rawValue, options: .caseInsensitive)
+            roomAliasDetector = try NSRegularExpression(pattern: MatrixEntityRegex.roomAlias.rawValue, options: .caseInsensitive)
+            linkDetector = try NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue)
+        } catch {
+            fatalError()
         }
-        h1,h2,h3 {
-            font-size: 1.2em;
+    }
+    
+    func fromPlain(_ string: String?) -> AttributedString? {
+        guard let string = string else {
+            return nil
         }
-"""
+
+        let mutableAttributedString = NSMutableAttributedString(string: string)
+        
+        addLinkAttributesToAttributedString(mutableAttributedString)
+        
+        return try? AttributedString(mutableAttributedString, including: \.elementX)
+    }
+    
+    func fromMarkdown(_ string: String?) -> AttributedString? {
+        guard let string = string else {
+            return nil
+        }
+
+        guard let mutableAttributedString = try? NSMutableAttributedString(markdown: string) else {
+            return nil
+        }
+        
+        addLinkAttributesToAttributedString(mutableAttributedString)
+        
+        return try? AttributedString(mutableAttributedString, including: \.elementX)
     }
     
     // Do not use the default HTML renderer of NSAttributedString because this method
@@ -49,6 +82,7 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
             DTDefaultFontName: defaultFont.fontName,
             DTDefaultFontSize: defaultFont.pointSize,
             DTDefaultTextColor: defaultColor,
+            DTDefaultLinkColor: linkColor,
             DTDefaultStyleSheet: DTCSSStylesheet(styleBlock: self.defaultCSS) as Any
         ]
         
@@ -60,17 +94,19 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
             element?.sanitize(font: defaultFont)
         }
             
-        guard var nsAttributedString = builder.generatedAttributedString() else {
+        guard let attributedString = builder.generatedAttributedString() else {
             return nil
         }
         
-        nsAttributedString = AttributedStringBuilderUtils.removeDTCoreTextArtifacts(nsAttributedString)
+        let mutableAttributedString = NSMutableAttributedString(attributedString: attributedString)
         
-        nsAttributedString = AttributedStringBuilderUtils.removeMarkedBlockquotesArtifacts(nsAttributedString)
+        removeDTCoreTextArtifactsFromAttributedString(mutableAttributedString)
         
-        nsAttributedString = AttributedStringBuilderUtils.createLinks(nsAttributedString)
+        replaceMarkedBlockquotes(mutableAttributedString)
         
-        return try? AttributedString(nsAttributedString, including: \.elementX)
+        addLinkAttributesToAttributedString(mutableAttributedString)
+        
+        return try? AttributedString(mutableAttributedString, including: \.elementX)
     }
     
     func blockquoteCoalescedComponentsFrom(_ attributedString: AttributedString?) -> [AttributedStringBuilderComponent]? {
@@ -83,4 +119,116 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
                                              isBlockquote: value != nil)
         }
     }
+    
+    // MARK: - Private
+    
+    private func replaceMarkedBlockquotes(_ attributedString: NSMutableAttributedString) {
+        // Enumerate all sections marked thanks to `cssToMarkBlockquotes`
+        // and apply our own attribute instead.
+        
+        // According to blockquotes in the string, DTCoreText can apply 2 policies:
+        //     - define a `DTTextBlocksAttribute` attribute on a <blockquote> block
+        //     - or, just define a `NSBackgroundColorAttributeName` attribute
+        
+        attributedString.enumerateAttribute(.DTTextBlocks, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
+            guard let value = value as? NSArray,
+                  let dtTextBlock = value.firstObject as? DTTextBlock,
+                  dtTextBlock.backgroundColor == temporaryBlockquoteMarkingColor else {
+                      return
+                  }
+            
+            attributedString.addAttribute(.MXBlockquote, value: true, range: range)
+        }
+        
+        attributedString.enumerateAttribute(.backgroundColor, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
+            guard let value = value as? UIColor,
+                  value == temporaryBlockquoteMarkingColor else {
+                      return
+                  }
+            
+            attributedString.removeAttribute(.backgroundColor, range: range)
+            attributedString.addAttribute(.MXBlockquote, value: true, range: range)
+        }
+    }
+    
+    private func removeDTCoreTextArtifactsFromAttributedString(_ attributedString: NSMutableAttributedString) {
+        guard attributedString.length > 0 else {
+            return
+        }
+        
+        // DTCoreText adds a newline at the end of plain text ( https://github.com/Cocoanetics/DTCoreText/issues/779 )
+        // or after a blockquote section.
+        // Trim trailing whitespace and newlines in the string content
+        while (attributedString.string as NSString).hasSuffixCharacter(from: .whitespacesAndNewlines) {
+            attributedString.deleteCharacters(in: .init(location: attributedString.length - 1, length: 1))
+        }
+    }
+    
+    private func addLinkAttributesToAttributedString(_ attributedString: NSMutableAttributedString) {
+        
+        let string = attributedString.string
+        let range = NSRange(location: 0, length: attributedString.string.count)
+        
+        var matches = userIdDetector.matches(in: string, options: [], range: range)
+        matches.append(contentsOf: roomIdDetector.matches(in: string, options: [], range: range))
+        matches.append(contentsOf: eventIdDetector.matches(in: string, options: [], range: range))
+        matches.append(contentsOf: groupIdDetector.matches(in: string, options: [], range: range))
+        matches.append(contentsOf: roomAliasDetector.matches(in: string, options: [], range: range))
+        matches.append(contentsOf: linkDetector.matches(in: string, options: [], range: range))
+        
+        guard matches.count > 0 else {
+            return
+        }
+        
+        matches.forEach { match in
+            guard let matchRange = Range(match.range, in: string) else {
+                return
+            }
+            
+            let link = string[matchRange].addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)
+            attributedString.addAttributes([NSAttributedString.Key.link: link as Any,
+                                                   NSAttributedString.Key.foregroundColor: linkColor],
+                                                  range: match.range)
+        }
+    }
+    
+    private var cssToMarkBlockquotes: String {
+        return "blockquote {background: \(temporaryBlockquoteMarkingColor.toHexString()); display: block;}"
+    }
+    
+    private var defaultCSS: String {
+        cssToMarkBlockquotes +
+"""
+        pre,code {
+            background-color: #F5F7FA;
+            display: inline;
+            font-family: monospace;
+            white-space: pre;
+            -coretext-fontname: Menlo-Regular;
+        }
+        h1,h2,h3 {
+            font-size: 1.2em;
+        }
+"""
+    }
+}
+
+extension UIColor {
+    func toHexString() -> String {
+        var red: CGFloat = 0.0
+        var green: CGFloat = 0.0
+        var blue: CGFloat = 0.0
+        var alpha: CGFloat = 0.0
+        
+        getRed(&red, green: &green, blue: &blue, alpha: &alpha)
+        
+        let rgb: Int = (Int)(red*255)<<16 | (Int)(green*255)<<8 | (Int)(blue*255)<<0
+        
+        return NSString(format: "#%06x", rgb) as String
+    }
+}
+
+extension NSAttributedString.Key {
+    static let DTTextBlocks: NSAttributedString.Key = .init(rawValue: DTTextBlocksAttribute)
+    static let MXBlockquote: NSAttributedString.Key = .init(rawValue: BlockquoteAttribute.name)
 }