399 lines
16 KiB
Swift
399 lines
16 KiB
Swift
//
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// Copyright 2025 New Vector Ltd.
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//
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// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
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// Please see LICENSE files in the repository root for full details.
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//
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import Compound
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import DTCoreText
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import LRUCache
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import MatrixRustSDK
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import UIKit
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struct AttributedStringBuilderV1: AttributedStringBuilderProtocol {
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private let cacheKey: String
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private let temporaryBlockquoteMarkingColor = UIColor.magenta
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private let temporaryCodeBlockMarkingColor = UIColor.cyan
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private let mentionBuilder: MentionBuilderProtocol
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private static let cacheDispatchQueue = DispatchQueue(label: "io.element.elementx.attributed_string_builder_cache")
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private static var caches: [String: LRUCache<String, AttributedString>] = [:]
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static func invalidateCaches() {
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caches.removeAll()
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}
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init(cacheKey: String, mentionBuilder: MentionBuilderProtocol) {
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self.cacheKey = cacheKey
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self.mentionBuilder = mentionBuilder
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}
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func fromPlain(_ string: String?) -> AttributedString? {
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guard let string else {
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return nil
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}
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if let cached = Self.cachedValue(forKey: string, cacheKey: cacheKey) {
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return cached
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}
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let mutableAttributedString = NSMutableAttributedString(string: string)
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removeDefaultForegroundColors(mutableAttributedString)
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addLinksAndMentions(mutableAttributedString)
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addMatrixEntityPermalinkAttributesTo(mutableAttributedString)
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let result = try? AttributedString(mutableAttributedString, including: \.elementX)
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Self.cacheValue(result, forKey: string, cacheKey: cacheKey)
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return result
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}
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// Do not use the default HTML renderer of NSAttributedString because this method
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// runs on the UI thread which we want to avoid because renderHTMLString is called
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// most of the time from a background thread.
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// Use DTCoreText HTML renderer instead.
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// Using DTCoreText, which renders static string, helps to avoid code injection attacks
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// that could happen with the default HTML renderer of NSAttributedString which is a
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// webview.
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func fromHTML(_ htmlString: String?) -> AttributedString? {
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guard let originalHTMLString = htmlString else {
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return nil
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}
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if let cached = Self.cachedValue(forKey: originalHTMLString, cacheKey: cacheKey) {
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return cached
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}
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let htmlString = originalHTMLString.replacingHtmlBreaksOccurrences()
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guard let data = htmlString.data(using: .utf8) else {
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return nil
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}
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let defaultFont = UIFont.preferredFont(forTextStyle: .body)
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let parsingOptions: [String: Any] = [
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DTUseiOS6Attributes: true,
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DTDefaultFontFamily: defaultFont.familyName,
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DTDefaultFontName: defaultFont.fontName,
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DTDefaultFontSize: defaultFont.pointSize,
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DTDefaultStyleSheet: DTCSSStylesheet(styleBlock: defaultCSS) as Any,
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DTDefaultLinkDecoration: false
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]
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guard let builder = DTHTMLAttributedStringBuilder(html: data, options: parsingOptions, documentAttributes: nil) else {
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return nil
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}
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builder.willFlushCallback = { element in
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element?.sanitize(font: defaultFont)
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}
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guard let attributedString = builder.generatedAttributedString() else {
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return nil
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}
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let mutableAttributedString = NSMutableAttributedString(attributedString: attributedString)
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removeDefaultForegroundColors(mutableAttributedString)
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detectPhishingAttempts(mutableAttributedString)
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addLinksAndMentions(mutableAttributedString)
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replaceMarkedBlockquotes(mutableAttributedString)
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replaceMarkedCodeBlocks(mutableAttributedString)
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addMatrixEntityPermalinkAttributesTo(mutableAttributedString)
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removeDTCoreTextArtifacts(mutableAttributedString)
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let result = try? AttributedString(mutableAttributedString, including: \.elementX)
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Self.cacheValue(result, forKey: htmlString, cacheKey: cacheKey)
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return result
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}
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// MARK: - Private
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private static func cacheValue(_ value: AttributedString?, forKey key: String, cacheKey: String) {
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cacheDispatchQueue.sync {
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if caches[cacheKey] == nil {
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caches[cacheKey] = LRUCache<String, AttributedString>(countLimit: 1000)
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}
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caches[cacheKey]?.setValue(value, forKey: key)
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}
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}
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private static func cachedValue(forKey key: String, cacheKey: String) -> AttributedString? {
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var result: AttributedString?
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cacheDispatchQueue.sync {
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result = caches[cacheKey]?.value(forKey: key)
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}
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return result
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}
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private func removeDefaultForegroundColors(_ attributedString: NSMutableAttributedString) {
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attributedString.removeAttribute(.foregroundColor, range: .init(location: 0, length: attributedString.length))
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}
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// swiftlint:disable:next cyclomatic_complexity
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private func addLinksAndMentions(_ attributedString: NSMutableAttributedString) {
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let string = attributedString.string
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// Event identifiers and room aliases and identifiers detected in plain text are techincally incomplete
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// without via parameters and we won't bother detecting them
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var matches: [TextParsingMatch] = MatrixEntityRegex.userIdentifierRegex.matches(in: string).compactMap { match in
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guard let matchRange = Range(match.range, in: string) else {
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return nil
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}
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let identifier = String(string[matchRange])
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return TextParsingMatch(type: .userID(identifier: identifier), range: match.range)
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}
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matches.append(contentsOf: MatrixEntityRegex.roomAliasRegex.matches(in: string).compactMap { match in
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guard let matchRange = Range(match.range, in: string) else {
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return nil
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}
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let alias = String(string[matchRange])
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return TextParsingMatch(type: .roomAlias(alias: alias), range: match.range)
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})
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matches.append(contentsOf: MatrixEntityRegex.uriRegex.matches(in: string).compactMap { match in
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guard let matchRange = Range(match.range, in: string) else {
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return nil
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}
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let uri = String(string[matchRange])
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return TextParsingMatch(type: .matrixURI(uri: uri), range: match.range)
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})
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matches.append(contentsOf: MatrixEntityRegex.linkRegex.matches(in: string).compactMap { match in
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guard let matchRange = Range(match.range, in: string) else {
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return nil
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}
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let link = String(string[matchRange]).asSanitizedLink
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return TextParsingMatch(type: .link(urlString: link), range: match.range)
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})
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matches.append(contentsOf: MatrixEntityRegex.allUsersRegex.matches(in: attributedString.string).map { match in
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TextParsingMatch(type: .atRoom, range: match.range)
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})
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guard matches.count > 0 else {
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return
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}
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// Sort the links by length so the longest one always takes priority
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matches.sorted { $0.range.length > $1.range.length }.forEach { [attributedString] match in
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var hasLink = false
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attributedString.enumerateAttribute(.link, in: match.range, options: []) { value, _, stop in
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if value != nil {
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hasLink = true
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stop.pointee = true
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}
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}
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if hasLink {
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return
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}
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// Don't add any extra attributes within codeblocks
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if attributedString.attribute(.backgroundColor, at: match.range.location, effectiveRange: nil) as? UIColor == temporaryCodeBlockMarkingColor {
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return
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}
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switch match.type {
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case .atRoom:
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attributedString.addAttribute(.MatrixAllUsersMention, value: true, range: match.range)
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case .roomAlias(let alias):
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if let urlString = try? matrixToRoomAliasPermalink(roomAlias: alias),
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let url = URL(string: urlString) {
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attributedString.addAttribute(.link, value: url, range: match.range)
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}
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case .matrixURI(let uri):
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if let url = URL(string: uri) {
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attributedString.addAttribute(.link, value: url, range: match.range)
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}
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case .userID, .link:
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if let url = match.link {
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attributedString.addAttribute(.link, value: url, range: match.range)
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}
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}
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}
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}
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private func replaceMarkedBlockquotes(_ attributedString: NSMutableAttributedString) {
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// According to blockquotes in the string, DTCoreText can apply 2 policies:
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// - define a `DTTextBlocksAttribute` attribute on a <blockquote> block
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// - or, just define a `NSBackgroundColorAttributeName` attribute
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attributedString.enumerateAttribute(.DTTextBlocks, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
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guard let value = value as? NSArray,
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let dtTextBlock = value.firstObject as? DTTextBlock,
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dtTextBlock.backgroundColor == temporaryBlockquoteMarkingColor else {
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return
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}
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attributedString.addAttribute(.MatrixBlockquote, value: true, range: range)
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}
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attributedString.enumerateAttribute(.backgroundColor, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
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guard let value = value as? UIColor,
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value == temporaryBlockquoteMarkingColor else {
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return
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}
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attributedString.removeAttribute(.backgroundColor, range: range)
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attributedString.addAttribute(.MatrixBlockquote, value: true, range: range)
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}
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}
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private func replaceMarkedCodeBlocks(_ attributedString: NSMutableAttributedString) {
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attributedString.enumerateAttribute(.backgroundColor, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
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if let value = value as? UIColor,
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value == temporaryCodeBlockMarkingColor {
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attributedString.addAttribute(.backgroundColor, value: UIColor.compound._bgCodeBlock as Any, range: range)
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attributedString.removeAttribute(.link, range: range)
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}
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}
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}
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func addMatrixEntityPermalinkAttributesTo(_ attributedString: NSMutableAttributedString) {
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attributedString.enumerateAttribute(.link, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
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if value != nil {
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if let url = value as? URL,
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let matrixEntity = parseMatrixEntityFrom(uri: url.absoluteString) {
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switch matrixEntity.id {
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case .user(let userID):
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mentionBuilder.handleUserMention(for: attributedString, in: range, url: url, userID: userID, userDisplayName: nil)
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case .room(let roomID):
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mentionBuilder.handleRoomIDMention(for: attributedString, in: range, url: url, roomID: roomID)
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case .roomAlias(let alias):
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mentionBuilder.handleRoomAliasMention(for: attributedString, in: range, url: url, roomAlias: alias, roomDisplayName: nil)
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case .eventOnRoomId(let roomID, let eventID):
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mentionBuilder.handleEventOnRoomIDMention(for: attributedString, in: range, url: url, eventID: eventID, roomID: roomID)
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case .eventOnRoomAlias(let alias, let eventID):
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mentionBuilder.handleEventOnRoomAliasMention(for: attributedString, in: range, url: url, eventID: eventID, roomAlias: alias)
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}
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}
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}
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}
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attributedString.enumerateAttribute(.MatrixAllUsersMention, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
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if let value = value as? Bool,
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value {
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mentionBuilder.handleAllUsersMention(for: attributedString, in: range)
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}
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}
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}
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private func detectPhishingAttempts(_ attributedString: NSMutableAttributedString) {
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attributedString.enumerateAttribute(.link, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
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guard value != nil, let internalURL = value as? URL else {
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return
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}
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let displayString = attributedString.attributedSubstring(from: range).string
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guard PhishingDetector.isPhishingAttempt(displayString: displayString, internalURL: internalURL) else {
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return
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}
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handlePhishingAttempt(for: attributedString, in: range, internalURL: internalURL, displayString: displayString)
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}
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}
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private func handlePhishingAttempt(for attributedString: NSMutableAttributedString,
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in range: NSRange,
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internalURL: URL,
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displayString: String) {
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// Let's remove the existing link attribute
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attributedString.removeAttribute(.link, range: range)
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var urlComponents = URLComponents()
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urlComponents.scheme = URL.confirmationScheme
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urlComponents.host = ""
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let parameters = ConfirmURLParameters(internalURL: internalURL, displayString: displayString)
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urlComponents.queryItems = parameters.urlQueryItems
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guard let finalURL = urlComponents.url else {
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return
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}
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attributedString.addAttribute(.link, value: finalURL, range: range)
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}
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private func removeDTCoreTextArtifacts(_ attributedString: NSMutableAttributedString) {
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guard attributedString.length > 0 else {
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return
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}
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// DTCoreText adds a newline at the end of plain text ( https://github.com/Cocoanetics/DTCoreText/issues/779 )
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// or after a blockquote section.
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// Trim trailing whitespace and newlines in the string content
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while (attributedString.string as NSString).hasSuffixCharacter(from: .whitespacesAndNewlines) {
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attributedString.deleteCharacters(in: .init(location: attributedString.length - 1, length: 1))
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}
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}
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private var defaultCSS: String {
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"""
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blockquote {
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background: \(temporaryBlockquoteMarkingColor.toHexString());
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display: block;
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}
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pre,code {
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background-color: \(temporaryCodeBlockMarkingColor.toHexString());
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display: inline;
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white-space: pre;
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font-size: 0.9em;
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-coretext-fontname: .AppleSystemUIFontMonospaced-Regular;
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}
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h1,h2,h3 {
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font-size: 1.2em;
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}
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"""
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}
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}
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private extension UIColor {
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func toHexString() -> String {
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var red: CGFloat = 0.0
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var green: CGFloat = 0.0
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var blue: CGFloat = 0.0
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var alpha: CGFloat = 0.0
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getRed(&red, green: &green, blue: &blue, alpha: &alpha)
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let rgb = Int(red * 255) << 16 | Int(green * 255) << 8 | Int(blue * 255) << 0
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return NSString(format: "#%06x", rgb) as String
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}
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}
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private struct TextParsingMatch {
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enum MatchType {
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case userID(identifier: String)
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case roomAlias(alias: String)
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case matrixURI(uri: String)
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case link(urlString: String)
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case atRoom
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}
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let type: MatchType
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let range: NSRange
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var link: URL? {
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switch type {
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case .userID(let identifier):
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return try? URL(string: matrixToUserPermalink(userId: identifier))
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case .link(let urlString):
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return URL(string: urlString)
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default:
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return nil
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}
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}
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}
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