session-ios/Session/Utilities/MentionUtilities.swift

// Copyright © 2022 Rangeproof Pty Ltd. All rights reserved.

import Foundation
import GRDB
import SessionUIKit
import SessionMessagingKit
import SessionUtilitiesKit

public enum MentionUtilities {
    public enum MentionLocation {
        case incomingMessage
        case outgoingMessage
        case incomingQuote
        case outgoingQuote
        case quoteDraft
        case styleFree
    }
    
    public static func highlightMentionsNoAttributes(
        in string: String,
        threadVariant: SessionThread.Variant,
        currentUserSessionId: String,
        currentUserBlinded15SessionId: String?,
        currentUserBlinded25SessionId: String?,
        using dependencies: Dependencies
    ) -> String {
        /// **Note:** We are returning the string here so the 'textColor' and 'primaryColor' values are irrelevant
        return highlightMentions(
            in: string,
            threadVariant: threadVariant,
            currentUserSessionId: currentUserSessionId,
            currentUserBlinded15SessionId: currentUserBlinded15SessionId,
            currentUserBlinded25SessionId: currentUserBlinded25SessionId,
            location: .styleFree,
            textColor: .black,
            theme: .classicDark,
            primaryColor: Theme.PrimaryColor.green,
            attributes: [:],
            using: dependencies
        )
        .string
        .deformatted()
    }

    public static func highlightMentions(
        in string: String,
        threadVariant: SessionThread.Variant,
        currentUserSessionId: String?,
        currentUserBlinded15SessionId: String?,
        currentUserBlinded25SessionId: String?,
        location: MentionLocation,
        textColor: UIColor,
        theme: Theme,
        primaryColor: Theme.PrimaryColor,
        attributes: [NSAttributedString.Key: Any],
        using dependencies: Dependencies
    ) -> NSAttributedString {
        guard
            let regex: NSRegularExpression = try? NSRegularExpression(pattern: "@[0-9a-fA-F]{66}", options: [])
        else {
            return NSAttributedString(string: string)
        }
        
        var string = string
        var lastMatchEnd: Int = 0
        var mentions: [(range: NSRange, isCurrentUser: Bool)] = []
        let currentUserSessionIds: Set<String> = [
            currentUserSessionId,
            currentUserBlinded15SessionId,
            currentUserBlinded25SessionId
        ]
        .compactMap { $0 }
        .asSet()
        
        while let match: NSTextCheckingResult = regex.firstMatch(
            in: string,
            options: .withoutAnchoringBounds,
            range: NSRange(location: lastMatchEnd, length: string.utf16.count - lastMatchEnd)
        ) {
            guard let range: Range = Range(match.range, in: string) else { break }
            
            let sessionId: String = String(string[range].dropFirst()) // Drop the @
            let isCurrentUser: Bool = currentUserSessionIds.contains(sessionId)
            
            guard let targetString: String = {
                guard !isCurrentUser else { return "you".localized() }
                // FIXME: This does a database query and is happening when populating UI - should try to refactor it somehow (ideally resolve a set of mentioned profiles as part of the database query)
                guard let displayName: String = Profile.displayNameNoFallback(id: sessionId, threadVariant: threadVariant, using: dependencies) else {
                    lastMatchEnd = (match.range.location + match.range.length)
                    return nil
                }
                
                return displayName
            }()
            else { continue }
            
            string = string.replacingCharacters(in: range, with: "@\(targetString)")    // stringlint:ignore
            lastMatchEnd = (match.range.location + targetString.utf16.count)
            
            mentions.append((
                // + 1 to include the @
                range: NSRange(location: match.range.location, length: targetString.utf16.count + 1),
                isCurrentUser: isCurrentUser
            ))
        }
        
        let sizeDiff: CGFloat = (Values.smallFontSize / Values.mediumFontSize)
        let result: NSMutableAttributedString = NSMutableAttributedString(string: string, attributes: attributes)
        mentions.forEach { mention in
            result.addAttribute(.font, value: UIFont.boldSystemFont(ofSize: Values.smallFontSize), range: mention.range)
            
            if mention.isCurrentUser && location == .incomingMessage {
                // Note: The designs don't match with the dynamic sizing so these values need to be calculated
                // to maintain a "rounded rect" effect rather than a "pill" effect
                result.addAttribute(.currentUserMentionBackgroundCornerRadius, value: (8 * sizeDiff), range: mention.range)
                result.addAttribute(.currentUserMentionBackgroundPadding, value: (3 * sizeDiff), range: mention.range)
                result.addAttribute(.currentUserMentionBackgroundColor, value: primaryColor.color, range: mention.range)
                result.addAttribute(.kern, value: (3 * sizeDiff), range: NSRange(location: mention.range.upperBound, length: 1))
            }
            
            switch (location, mention.isCurrentUser, theme.interfaceStyle) {
                // 1 - Incoming messages where the mention is for the current user
                case (.incomingMessage, true, .dark): result.addAttribute(.foregroundColor, value: UIColor.black, range: mention.range)
                case (.incomingMessage, true, _): result.addAttribute(.foregroundColor, value: textColor, range: mention.range)
                
                // 2 - Incoming messages where the mention is for another user
                case (.incomingMessage, false, .dark): result.addAttribute(.foregroundColor, value: primaryColor.color, range: mention.range)
                case (.incomingMessage, false, _): result.addAttribute(.foregroundColor, value: textColor, range: mention.range)
                    
                // 3 - Outgoing messages
                case (.outgoingMessage, _, .dark): result.addAttribute(.foregroundColor, value: UIColor.black, range: mention.range)
                case (.outgoingMessage, _, _): result.addAttribute(.foregroundColor, value: textColor, range: mention.range)
                
                // 4 - Mentions in quotes
                case (.outgoingQuote, _, .dark): result.addAttribute(.foregroundColor, value: UIColor.black, range: mention.range)
                case (.outgoingQuote, _, _): result.addAttribute(.foregroundColor, value: textColor, range: mention.range)
                case (.incomingQuote, _, .dark): result.addAttribute(.foregroundColor, value: primaryColor.color, range: mention.range)
                case (.incomingQuote, _, _): result.addAttribute(.foregroundColor, value: textColor, range: mention.range)
                    
                // 5 - Mentions in quote drafts
                case (.quoteDraft, _, _), (.styleFree, _, _):
                    result.addAttribute(.foregroundColor, value: textColor, range: mention.range)
            }
        }
        
        return result
    }
}