session-ios/SignalMessaging/utils/DisplayableText.swift

//
//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
//

import Foundation

extension UnicodeScalar {
    class EmojiRange {
        // rangeStart and rangeEnd are inclusive.
        let rangeStart: UInt32
        let rangeEnd: UInt32

        // MARK: Initializers

        init(rangeStart: UInt32, rangeEnd: UInt32) {
            self.rangeStart = rangeStart
            self.rangeEnd = rangeEnd
        }
    }

    // From:
    // https://www.unicode.org/Public/emoji/
    // Current Version:
    // https://www.unicode.org/Public/emoji/6.0/emoji-data.txt
    //
    // These ranges can be code-generated using:
    //
    // * Scripts/emoji-data.txt 
    // * Scripts/emoji_ranges.py
    static let kEmojiRanges = [
        // NOTE: Don't treat Pound Sign # as Jumbomoji.
        //        EmojiRange(rangeStart:0x23, rangeEnd:0x23),
        // NOTE: Don't treat Asterisk * as Jumbomoji.
        //        EmojiRange(rangeStart:0x2A, rangeEnd:0x2A),
        // NOTE: Don't treat Digits 0..9 as Jumbomoji.
        //        EmojiRange(rangeStart:0x30, rangeEnd:0x39),
        // NOTE: Don't treat Copyright Symbol © as Jumbomoji.
        //        EmojiRange(rangeStart:0xA9, rangeEnd:0xA9),
        // NOTE: Don't treat Trademark Sign ® as Jumbomoji.
        //        EmojiRange(rangeStart:0xAE, rangeEnd:0xAE),
        EmojiRange(rangeStart: 0x200D, rangeEnd: 0x200D),
        EmojiRange(rangeStart: 0x203C, rangeEnd: 0x203C),
        EmojiRange(rangeStart: 0x2049, rangeEnd: 0x2049),
        EmojiRange(rangeStart: 0x20D0, rangeEnd: 0x20FF),
        EmojiRange(rangeStart: 0x2122, rangeEnd: 0x2122),
        EmojiRange(rangeStart: 0x2139, rangeEnd: 0x2139),
        EmojiRange(rangeStart: 0x2194, rangeEnd: 0x2199),
        EmojiRange(rangeStart: 0x21A9, rangeEnd: 0x21AA),
        EmojiRange(rangeStart: 0x231A, rangeEnd: 0x231B),
        EmojiRange(rangeStart: 0x2328, rangeEnd: 0x2328),
        EmojiRange(rangeStart: 0x2388, rangeEnd: 0x2388),
        EmojiRange(rangeStart: 0x23CF, rangeEnd: 0x23CF),
        EmojiRange(rangeStart: 0x23E9, rangeEnd: 0x23F3),
        EmojiRange(rangeStart: 0x23F8, rangeEnd: 0x23FA),
        EmojiRange(rangeStart: 0x24C2, rangeEnd: 0x24C2),
        EmojiRange(rangeStart: 0x25AA, rangeEnd: 0x25AB),
        EmojiRange(rangeStart: 0x25B6, rangeEnd: 0x25B6),
        EmojiRange(rangeStart: 0x25C0, rangeEnd: 0x25C0),
        EmojiRange(rangeStart: 0x25FB, rangeEnd: 0x25FE),
        EmojiRange(rangeStart: 0x2600, rangeEnd: 0x27BF),
        EmojiRange(rangeStart: 0x2934, rangeEnd: 0x2935),
        EmojiRange(rangeStart: 0x2B05, rangeEnd: 0x2B07),
        EmojiRange(rangeStart: 0x2B1B, rangeEnd: 0x2B1C),
        EmojiRange(rangeStart: 0x2B50, rangeEnd: 0x2B50),
        EmojiRange(rangeStart: 0x2B55, rangeEnd: 0x2B55),
        EmojiRange(rangeStart: 0x3030, rangeEnd: 0x3030),
        EmojiRange(rangeStart: 0x303D, rangeEnd: 0x303D),
        EmojiRange(rangeStart: 0x3297, rangeEnd: 0x3297),
        EmojiRange(rangeStart: 0x3299, rangeEnd: 0x3299),
        EmojiRange(rangeStart: 0xFE00, rangeEnd: 0xFE0F),
        EmojiRange(rangeStart: 0x1F000, rangeEnd: 0x1F0FF),
        EmojiRange(rangeStart: 0x1F10D, rangeEnd: 0x1F10F),
        EmojiRange(rangeStart: 0x1F12F, rangeEnd: 0x1F12F),
        EmojiRange(rangeStart: 0x1F16C, rangeEnd: 0x1F171),
        EmojiRange(rangeStart: 0x1F17E, rangeEnd: 0x1F17F),
        EmojiRange(rangeStart: 0x1F18E, rangeEnd: 0x1F18E),
        EmojiRange(rangeStart: 0x1F191, rangeEnd: 0x1F19A),
        EmojiRange(rangeStart: 0x1F1AD, rangeEnd: 0x1F1FF),
        EmojiRange(rangeStart: 0x1F201, rangeEnd: 0x1F20F),
        EmojiRange(rangeStart: 0x1F21A, rangeEnd: 0x1F21A),
        EmojiRange(rangeStart: 0x1F22F, rangeEnd: 0x1F22F),
        EmojiRange(rangeStart: 0x1F232, rangeEnd: 0x1F23A),
        EmojiRange(rangeStart: 0x1F23C, rangeEnd: 0x1F23F),
        EmojiRange(rangeStart: 0x1F249, rangeEnd: 0x1F64F),
        EmojiRange(rangeStart: 0x1F680, rangeEnd: 0x1F6FF),
        EmojiRange(rangeStart: 0x1F774, rangeEnd: 0x1F77F),
        EmojiRange(rangeStart: 0x1F7D5, rangeEnd: 0x1F7FF),
        EmojiRange(rangeStart: 0x1F80C, rangeEnd: 0x1F80F),
        EmojiRange(rangeStart: 0x1F848, rangeEnd: 0x1F84F),
        EmojiRange(rangeStart: 0x1F85A, rangeEnd: 0x1F85F),
        EmojiRange(rangeStart: 0x1F888, rangeEnd: 0x1F88F),
        EmojiRange(rangeStart: 0x1F8AE, rangeEnd: 0x1FFFD),
        EmojiRange(rangeStart: 0xE0020, rangeEnd: 0xE007F)
    ]

    var isEmoji: Bool {

        // Binary search.
        var left: Int = 0
        var right = Int(UnicodeScalar.kEmojiRanges.count - 1)
        while true {
            let mid = (left + right) / 2
            let midRange = UnicodeScalar.kEmojiRanges[mid]
            if value < midRange.rangeStart {
                if mid == left {
                    return false
                }
                right = mid - 1
            } else if value > midRange.rangeEnd {
                if mid == right {
                    return false
                }
                left = mid + 1
            } else {
                return true
            }
        }
    }

    var isZeroWidthJoiner: Bool {

        return value == 8205
    }
}

extension String {

    var glyphCount: Int {
        let richText = NSAttributedString(string: self)
        let line = CTLineCreateWithAttributedString(richText)
        return CTLineGetGlyphCount(line)
    }

    var isSingleEmoji: Bool {
        return glyphCount == 1 && containsEmoji
    }

    var containsEmoji: Bool {
        return unicodeScalars.contains { $0.isEmoji }
    }

    var containsOnlyEmoji: Bool {
        return !isEmpty
            && !unicodeScalars.contains(where: {
                !$0.isEmoji
                    && !$0.isZeroWidthJoiner
            })
    }
}

@objc public class DisplayableText: NSObject {

    @objc public let fullText: String
    @objc public let displayText: String
    @objc public let isTextTruncated: Bool
    @objc public let jumbomojiCount: UInt

    @objc
    static let kMaxJumbomojiCount: UInt = 5
    // This value is a bit arbitrary since we don't need to be 100% correct about 
    // rendering "Jumbomoji".  It allows us to place an upper bound on worst-case
    // performacne.
    @objc
    static let kMaxCharactersPerEmojiCount: UInt = 10

    // MARK: Initializers

    @objc public init(fullText: String, displayText: String, isTextTruncated: Bool) {
        self.fullText = fullText
        self.displayText = displayText
        self.isTextTruncated = isTextTruncated
        self.jumbomojiCount = DisplayableText.jumbomojiCount(in: fullText)
    }

    // MARK: Emoji

    // If the string is...
    //
    // * Non-empty
    // * Only contains emoji
    // * Contains <= kMaxJumbomojiCount emoji
    //
    // ...return the number of emoji (to be treated as "Jumbomoji") in the string.
    private class func jumbomojiCount(in string: String) -> UInt {
        if string == "" {
            return 0
        }
        if string.count > Int(kMaxJumbomojiCount * kMaxCharactersPerEmojiCount) {
            return 0
        }
        guard string.containsOnlyEmoji else {
            return 0
        }
        let emojiCount = string.glyphCount
        if UInt(emojiCount) > kMaxJumbomojiCount {
            return 0
        }
        return UInt(emojiCount)
    }

    // MARK: Filter Methods

    @objc
    public class func filterNotificationText(_ text: String?) -> String? {
        guard let text = text?.filterStringForDisplay() else {
            return nil
        }

        // iOS strips anything that looks like a printf formatting character from
        // the notification body, so if we want to dispay a literal "%" in a notification
        // it must be escaped.
        // see https://developer.apple.com/documentation/uikit/uilocalnotification/1616646-alertbody
        // for more details.
        return text.replacingOccurrences(of: "%", with: "%%")
    }

    @objc
    public class func displayableText(_ rawText: String) -> DisplayableText {
        // Only show up to N characters of text.
        let kMaxTextDisplayLength = 512
        let fullText = rawText.filterStringForDisplay()
        var isTextTruncated = false
        var displayText = fullText
        if displayText.count > kMaxTextDisplayLength {
            // Trim whitespace before _AND_ after slicing the snipper from the string.
            let snippet = String(displayText.prefix(kMaxTextDisplayLength)).ows_stripped()
            displayText = String(format: NSLocalizedString("OVERSIZE_TEXT_DISPLAY_FORMAT", comment:
                "A display format for oversize text messages."),
                snippet)
            isTextTruncated = true
        }

        let displayableText = DisplayableText(fullText: fullText, displayText: displayText, isTextTruncated: isTextTruncated)
        return displayableText
    }
}