// // RichTextParser.swift // RichTextView // // Created by Ahmed Elkady on 2018-11-08. // Copyright © 2018 Top Hat. All rights reserved. // import Down import UIKit class RichTextParser { // MARK: - Constants enum ParserConstants { static let mathTagName = "math" static let interactiveElementTagName = "interactive-element" static let highlightedElementTagName = "highlighted-element" static let latexRegex = "\\[\(ParserConstants.mathTagName)\\](.*?)\\[\\/\(ParserConstants.mathTagName)\\]" static let latexRegexCaptureGroupIndex = 0 static let interactiveElementRegex = """ \\[\(ParserConstants.interactiveElementTagName)\\sid=.+?\\].*?\\[\\/\(ParserConstants.interactiveElementTagName)\\] """ static let highlightedElementRegex = """ \\[\(ParserConstants.highlightedElementTagName)\\sid=.+?\\].*?\\[\\/\(ParserConstants.highlightedElementTagName)\\] """ private static let tAPlaceholderPrefix = "{RichTextView-TextAttachmentPosition" private static let tAPlaceholderSuffix = "}" static let textAttachmentPlaceholderAssigner = "=" static let textAttachmentPlaceholderRegex = "\\\(ParserConstants.tAPlaceholderPrefix)\(ParserConstants.textAttachmentPlaceholderAssigner)[0-9]+?\\\(ParserConstants.tAPlaceholderSuffix)" static let textAttachmentPlaceholder = "\(ParserConstants.tAPlaceholderPrefix)\(ParserConstants.textAttachmentPlaceholderAssigner)%d\(ParserConstants.tAPlaceholderSuffix)" typealias RichTextWithErrors = (output: NSAttributedString, errors: [ParsingError]?) static let bulletString = "•" static let listOpeningHTMLString = " [RichDataType] { if input.isEmpty { return [RichDataType.text(richText: NSAttributedString(string: ""), font: self.font, errors: nil)] } var errors: [ParsingError]? return self.splitInputOnVideoPortions(input).compactMap { input -> RichDataType in if self.isStringAVideoTag(input) { return RichDataType.video(tag: input, error: nil) } let results = self.getRichTextWithErrors(from: input) if errors == nil { errors = results.errors } else if let resultErrors = results.errors { errors?.append(contentsOf: resultErrors) } return RichDataType.text(richText: results.output, font: self.font, errors: errors) } } func getRichTextWithErrors(from input: String) -> ParserConstants.RichTextWithErrors { let input = self.stripCodeTagsIfNecessary(from: input) let inputAsMutableAttributedString = NSMutableAttributedString(string: input) let richTextWithSpecialDataTypesHandled = self.getRichTextWithSpecialDataTypesHandled( fromString: inputAsMutableAttributedString ) let textAttachmentAttributesInRichText = self.extractTextAttachmentAttributesInOrder(fromAttributedString: richTextWithSpecialDataTypesHandled.output) let richTextWithHTMLAndMarkdownHandled = self.getRichTextWithHTMLAndMarkdownHandled( fromString: self.replaceTextAttachmentsWithPlaceHolderInfo(inAttributedString: richTextWithSpecialDataTypesHandled.output) ) let outputRichText = self.mergeSpecialDataAndHTMLMarkdownAttribute( htmlMarkdownString: NSMutableAttributedString(attributedString: richTextWithHTMLAndMarkdownHandled.output), specialDataTypesString: richTextWithSpecialDataTypesHandled.output, textAttachmentAttributes: textAttachmentAttributesInRichText ).trimmingTrailingNewlinesAndWhitespaces() outputRichText.replaceFont(with: self.font) outputRichText.replaceColor(with: self.textColor) if richTextWithSpecialDataTypesHandled.errors == nil, richTextWithHTMLAndMarkdownHandled.errors == nil { return (outputRichText, nil) } let outputErrors = (richTextWithSpecialDataTypesHandled.errors ?? [ParsingError]()) + (richTextWithHTMLAndMarkdownHandled.errors ?? [ParsingError]()) return (outputRichText, outputErrors) } private func mergeSpecialDataAndHTMLMarkdownAttribute(htmlMarkdownString: NSMutableAttributedString, specialDataTypesString: NSAttributedString, textAttachmentAttributes: [[NSAttributedString.Key: Any]]) -> NSMutableAttributedString { let outputString = self.mergeTextAttachmentsAndHTMLMarkdownAttributes( htmlMarkdownString: htmlMarkdownString, textAttachmentAttributes: textAttachmentAttributes ) let rangeOfSpecialDataString = NSRange(location: 0, length: specialDataTypesString.length) specialDataTypesString.enumerateAttributes(in: rangeOfSpecialDataString) { (attributes, range, _) in if attributes.isEmpty || attributes[.attachment] != nil { return } let specialDataSubstring = specialDataTypesString.string[ max(range.lowerBound, 0).. outputString.length { return } let newOutuptSubstring = NSMutableAttributedString(attributedString: outputString.attributedSubstring(from: rangeOfSubstringInOutputString)) newOutuptSubstring.addAttributes(attributes, range: NSRange(location: 0, length: newOutuptSubstring.length)) newOutuptSubstring.replaceCharacters(in: NSRange(location: 0, length: newOutuptSubstring.length), with: specialDataSubstring) outputString.replaceCharacters(in: rangeOfSubstringInOutputString, with: newOutuptSubstring) } return outputString } private func mergeTextAttachmentsAndHTMLMarkdownAttributes(htmlMarkdownString: NSMutableAttributedString, textAttachmentAttributes: [[NSAttributedString.Key: Any]]) -> NSMutableAttributedString { let textAttachmentRegex = try? NSRegularExpression(pattern: ParserConstants.textAttachmentPlaceholderRegex, options: []) let inputRange = NSRange(location: 0, length: htmlMarkdownString.length) guard let textAttachmentMatches = textAttachmentRegex?.matches(in: htmlMarkdownString.string, options: [], range: inputRange) else { return htmlMarkdownString } for match in textAttachmentMatches.reversed() { let matchedSubstring = htmlMarkdownString.attributedSubstring(from: match.range).string let matchedComponentsSeparatedByAssigner = matchedSubstring.components( separatedBy: ParserConstants.textAttachmentPlaceholderAssigner ) let decimalCharacters = CharacterSet.decimalDigits.inverted guard let textAttachmentPositionAsSubstring = matchedComponentsSeparatedByAssigner.last?.components(separatedBy: decimalCharacters).joined(), let textAttachmentPosition = Int(textAttachmentPositionAsSubstring), textAttachmentAttributes.indices.contains(textAttachmentPosition) else { continue } let textAttachmentAttributes = textAttachmentAttributes[textAttachmentPosition] guard let textAttachment = textAttachmentAttributes[.attachment] as? NSTextAttachment else { continue } let textAttachmentAttributedString = NSMutableAttributedString(attachment: textAttachment) textAttachmentAttributedString.addAttributes( textAttachmentAttributes, range: NSRange(location: 0, length: textAttachmentAttributedString.length) ) htmlMarkdownString.replaceCharacters(in: match.range, with: textAttachmentAttributedString) } return htmlMarkdownString } // MARK: - Boolean Checkers func isTextLatex(_ text: String) -> Bool { return !self.getLatexRanges(inText: text).isEmpty } func isTextInteractiveElement(_ text: String) -> Bool { return text.ranges(of: ParserConstants.interactiveElementRegex, options: .regularExpression).count != 0 } func isTextHighlightedElement(_ text: String) -> Bool { return text.ranges(of: ParserConstants.highlightedElementRegex, options: .regularExpression).count != 0 } private func isStringAVideoTag(_ input: String) -> Bool { return input.range(of: RichTextViewConstants.videoTagRegex, options: .regularExpression, range: nil, locale: nil) != nil } // MARK: - Video Functions private func splitInputOnVideoPortions(_ input: String) -> [String] { return input.getComponents(separatedBy: RichTextViewConstants.videoTagRegex) } // MARK: - HTML/Markdown Helpers private func getRichTextWithHTMLAndMarkdownHandled(fromString mutableAttributedString: NSMutableAttributedString) -> ParserConstants.RichTextWithErrors { let inputString = mutableAttributedString.string let inputStringWithoutBreakingSpaces = inputString.replaceTrailingWhiteSpaceWithNonBreakingSpace().replaceLeadingWhiteSpaceWithNonBreakingSpace() let inputStringWithoutCommonEditorTags = self.removeCommonEditorTags(from: inputStringWithoutBreakingSpaces) guard let inputAsHTMLString = try? Down(markdownString: inputStringWithoutCommonEditorTags).toHTML([.unsafe, .hardBreaks]), let inputAsHTMLWithZeroWidthSpaceRemoved = inputAsHTMLString.replaceAppropiateZeroWidthSpaces(), let htmlData = unescapeHTML(from: inputAsHTMLWithZeroWidthSpaceRemoved).data(using: .utf8) else { return (mutableAttributedString.trimmingTrailingNewlinesAndWhitespaces(), [ParsingError.attributedTextGeneration(text: inputString)]) } let parsedAttributedString = self.getParsedHTMLAttributedString(fromData: htmlData) guard let parsedHTMLAttributedString = parsedAttributedString else { return (mutableAttributedString.trimmingTrailingNewlinesAndWhitespaces(), [ParsingError.attributedTextGeneration(text: inputString)]) } let parsedMutableAttributedString = NSMutableAttributedString(attributedString: parsedHTMLAttributedString) let finalOutputString = self.addCustomStylingToBulletPointsIfNecessary(parsedMutableAttributedString) return (finalOutputString, nil) } private func getParsedHTMLAttributedString(fromData data: Data) -> NSAttributedString? { var attributedString: NSAttributedString? let options: [NSAttributedString.DocumentReadingOptionKey: Any] = [ .documentType: NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue ] if Thread.isMainThread { attributedString = try? NSAttributedString(data: data, options: options, documentAttributes: nil) } else { DispatchQueue.main.sync { attributedString = try? NSAttributedString(data: data, options: options, documentAttributes: nil) } } return attributedString } private func addCustomStylingToBulletPointsIfNecessary(_ input: NSMutableAttributedString) -> NSMutableAttributedString { guard let customBulletAttributes = self.customAdditionalAttributes?[ParserConstants.bulletCustomAttributeIdentifier], let bulletPointRegex = try? NSRegularExpression(pattern: ParserConstants.bulletString, options: []) else { return input } let bulletPointMatches = bulletPointRegex.matches( in: input.string, options: [], range: NSRange(location: 0, length: input.string.count) ) let output = input bulletPointMatches.reversed().forEach { match in output.addAttributes(customBulletAttributes, range: match.range) } return output } private func stripCodeTagsIfNecessary(from input: String) -> String { return input.replacingOccurrences(of: "[code]", with: "`").replacingOccurrences(of: "[/code]", with: "`") } private func removeCommonEditorTags(from input: String) -> String { return input.replacingOccurrences(of: "

", with: "").replacingOccurrences(of: "

", with: "") } private func unescapeHTML(from input: String) -> String { return input.replacingOccurrences(of: "&", with: "&") .replacingOccurrences(of: "<", with: "<") .replacingOccurrences(of: ">", with: ">") .replacingOccurrences(of: """, with: "\"") .replacingOccurrences(of: "'", with: "'") .replacingOccurrences(of: " ", with: " ") } // MARK: - String Helpers private func split(mutableAttributedString: NSMutableAttributedString, onPositions positions: [String.Index]) -> [NSAttributedString] { let splitStrings = mutableAttributedString.string.split(atPositions: positions) var output = [NSAttributedString]() for string in splitStrings { let range = (mutableAttributedString.string as NSString).range(of: string) let attributedString = mutableAttributedString.attributedSubstring(from: range) output.append(attributedString) } return output } private func extractPositions(fromRanges ranges: [Range]) -> [String.Index] { return ranges.flatMap { [$0.lowerBound, $0.upperBound] }.sorted() } // MARK: - Text Attachment Functions private func extractTextAttachmentAttributesInOrder(fromAttributedString input: NSAttributedString) -> [[NSAttributedString.Key: Any]] { var output = [[NSAttributedString.Key: Any]]() let range = NSRange(location: 0, length: input.length) input.enumerateAttributes(in: range, options: [.reverse]) { (attributes, _, _) in guard attributes.keys.contains(.attachment) else { return } output.append(attributes) } return output } private func replaceTextAttachmentsWithPlaceHolderInfo(inAttributedString input: NSAttributedString) -> NSMutableAttributedString { let output = NSMutableAttributedString(attributedString: input) let range = NSRange(location: 0, length: input.length) var position = 0 input.enumerateAttributes(in: range, options: [.reverse]) { (attributes, range, _) in guard attributes.keys.contains(.attachment) else { return } output.replaceCharacters(in: range, with: String(format: ParserConstants.textAttachmentPlaceholder, position)) position += 1 } return output } // MARK: - Special Data Type Helpers private func getLatexRanges(inText text: String) -> [Range] { guard let regex = try? NSRegularExpression(pattern: ParserConstants.latexRegex, options: [.caseInsensitive, .dotMatchesLineSeparators]) else { return [] } let range = NSRange(location: 0, length: text.count) let matches = regex.matches(in: text, range: range) return matches.compactMap { match in return Range(match.range(at: ParserConstants.latexRegexCaptureGroupIndex), in: text) } } private func calculateContentHeight() -> CGFloat { let frame = NSString(string: "").boundingRect( with: CGSize(width: 0, height: .max), options: [.usesFontLeading, .usesLineFragmentOrigin], attributes: [.font: self.font], context: nil ) return frame.size.height } private func getRichTextWithSpecialDataTypesHandled(fromString mutableAttributedString: NSMutableAttributedString) -> ParserConstants.RichTextWithErrors { let interactiveElementPositions = self.extractPositions( fromRanges: mutableAttributedString.string.ranges(of: ParserConstants.interactiveElementRegex, options: .regularExpression) ) let highlightedElementPositions = self.extractPositions( fromRanges: mutableAttributedString.string.ranges(of: ParserConstants.highlightedElementRegex, options: .regularExpression) ) let latexPositions = self.extractPositions(fromRanges: self.getLatexRanges(inText: mutableAttributedString.string)) let splitPositions = interactiveElementPositions + latexPositions + highlightedElementPositions if splitPositions.isEmpty { return (mutableAttributedString.trimmingTrailingNewlinesAndWhitespaces(), nil) } return self.mergeSpecialDataComponentsAndReturnRichText( self.split(mutableAttributedString: mutableAttributedString, onPositions: splitPositions) ) } private func mergeSpecialDataComponentsAndReturnRichText(_ components: [NSAttributedString]) -> ParserConstants.RichTextWithErrors { let output = NSMutableAttributedString() var parsingErrors: [ParsingError]? components.forEach { attributedString in if self.isTextInteractiveElement(attributedString.string) { output.append(self.extractInteractiveElement(from: attributedString)) return } if self.isTextHighlightedElement(attributedString.string) { output.append(self.extractHighlightedElement(from: attributedString)) return } if self.isTextLatex(attributedString.string) { if let attributedLatexString = self.extractLatex(from: attributedString.string) { output.append(attributedLatexString) return } if parsingErrors == nil { parsingErrors = [ParsingError]() } output.append(attributedString) parsingErrors?.append(ParsingError.latexGeneration(text: attributedString.string)) return } output.append(attributedString) } return (output.trimmingTrailingNewlinesAndWhitespaces(), parsingErrors) } func extractLatex(from input: String) -> NSAttributedString? { return self.latexParser.extractLatex( from: input, textColor: self.textColor, baselineOffset: self.latexTextBaselineOffset, fontSize: self.font.pointSize, height: self.calculateContentHeight() ) } func extractInteractiveElement(from input: NSAttributedString) -> NSMutableAttributedString { let interactiveElementTagName = ParserConstants.interactiveElementTagName let interactiveElementID = input.string.getSubstring(inBetween: "[\(interactiveElementTagName) id=", and: "]") ?? input.string let interactiveElementText = input.string.getSubstring(inBetween: "]", and: "[/\(interactiveElementTagName)]") ?? input.string let attributes: [NSAttributedString.Key: Any] = [.link: interactiveElementID].merging(input.attributes(at: 0, effectiveRange: nil)) { (current, _) in current } let mutableAttributedInput = NSMutableAttributedString(string: interactiveElementText, attributes: attributes) return mutableAttributedInput } func extractHighlightedElement(from input: NSAttributedString) -> NSMutableAttributedString { let highlightedElementTagName = ParserConstants.highlightedElementTagName let highlightedElementID = input.string.getSubstring(inBetween: "[\(highlightedElementTagName) id=", and: "]") ?? input.string let highlightedElementText = input.string.getSubstring(inBetween: "]", and: "[/\(highlightedElementTagName)]") ?? input.string guard let richTextAttributes = self.customAdditionalAttributes?[highlightedElementID] else { return NSMutableAttributedString(string: highlightedElementText) } let attributes: [NSAttributedString.Key: Any] = [.highlight: highlightedElementID] .merging(input.attributes(at: 0, effectiveRange: nil)) { (current, _) in current } .merging(richTextAttributes) { (current, _) in current } let mutableAttributedInput = NSMutableAttributedString(string: highlightedElementText, attributes: attributes) return mutableAttributedInput } }