Tusker/Tusker/Views/ContentLabel.swift

//
//  ContentLabel.swift
//  Tusker
//
//  Created by Shadowfacts on 10/1/18.
//  Copyright © 2018 Shadowfacts. All rights reserved.
//

import UIKit
import SafariServices
import Pachyderm
import SwiftSoup

class ContentLabel: LinkLabel {
    
    private static let emojiRegex = try! NSRegularExpression(pattern: ":(\\w+):", options: [])
    
    var navigationDelegate: TuskerNavigationDelegate?
    
    // MARK: - Emojis
    func setEmojis(_ emojis: [Emoji]) {
        guard !emojis.isEmpty else { return }
        
        let group = DispatchGroup()

        let mutAttrString = NSMutableAttributedString(attributedString: self.attributedText!)
        let string = mutAttrString.string
        let matches = ContentLabel.emojiRegex.matches(in: string, options: [], range: NSRange(location: 0, length: mutAttrString.length))
        for match in matches.reversed() {
            let shortcode = (string as NSString).substring(with: match.range(at: 1))
            guard let emoji = emojis.first(where: { $0.shortcode == shortcode }) else {
                continue
            }

            group.enter()
            ImageCache.emojis.get(emoji.url) { (data) in
                guard let data = data, let image = UIImage(data: data) else {
                    group.leave()
                    return
                }
                DispatchQueue.main.async {
                    let attachment = self.createEmojiTextAttachment(image: image, index: match.range.location)
                    mutAttrString.replaceCharacters(in: match.range, with: NSAttributedString(attachment: attachment))
                    
                    group.leave()
                }
            }
        }

        group.notify(queue: .main) {
            self.attributedText = mutAttrString
            self.setNeedsLayout()
            self.setNeedsDisplay()
        }
    }
    
    // Based on https://github.com/ReticentJohn/Amaroq/blob/7c5b7088eb9fd1611dcb0f47d43bf8df093e142c/DireFloof/InlineImageHelpers.m
    func createEmojiTextAttachment(image: UIImage, index: Int) -> NSTextAttachment {
        let font = self.font!
        
        let adjustedCapHeight = font.capHeight - 1
        var imageSizeMatchingFontSize = CGSize(width: image.size.width * (adjustedCapHeight / image.size.height), height: adjustedCapHeight)
        
        let defaultScale: CGFloat = 1.4
        imageSizeMatchingFontSize = CGSize(width: imageSizeMatchingFontSize.width * defaultScale, height: imageSizeMatchingFontSize.height * defaultScale)
        let textColor = self.textColor!
        
        UIGraphicsBeginImageContextWithOptions(imageSizeMatchingFontSize, false, 0.0)
        textColor.set()
        image.draw(in: CGRect(origin: .zero, size: imageSizeMatchingFontSize))
        let attachmentImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        let attachment = NSTextAttachment()
        attachment.image = attachmentImage
        return attachment
    }
    
    // MARK: - HTML Parsing
    func setTextFromHtml(_ html: String) {
        let doc = try! SwiftSoup.parse(html)
        let body = doc.body()!
        
        let (attributedText, links) = attributedTextForHTMLNode(body)
        let mutAttrString = NSMutableAttributedString(attributedString: attributedText)
        
        // only trailing whitespace can be trimmed here
        // when posting an attachment without any text, pleromafe includes U+200B ZERO WIDTH SPACE at the beginning
        // this would get trimmed and cause range out of bounds crashes
        mutAttrString.trimTrailingCharactersInSet(.whitespacesAndNewlines)
        
        self.links = []
        let linkAttributes: [NSAttributedString.Key: Any] = [
            .foregroundColor: UIColor.systemBlue,
        ]
        for (range, url) in links {
            mutAttrString.addAttributes(linkAttributes, range: range)
            self.links.append(Link(range: range, url: url))
        }
        
        self.attributedText = mutAttrString
    }
    
    private func attributedTextForHTMLNode(_ node: Node) -> (NSAttributedString, [NSRange: URL]) {
        switch node {
        case let node as TextNode:
            return (NSAttributedString(string: node.text()), [:])
        case let node as Element:
            var links = [NSRange: URL]()
            let attributed = NSMutableAttributedString()
            for child in node.getChildNodes() {
                let (text, childLinks) = attributedTextForHTMLNode(child)
                for (range, url) in childLinks {
                    let newRange = NSRange(location: range.location + attributed.length, length: range.length)
                    links[newRange] = url
                }
                attributed.append(text)
            }
            
            switch node.tagName() {
            case "br":
                attributed.append(NSAttributedString(string: "\n"))
            case "a":
                if let link = try? node.attr("href"),
                    let url = URL(string: link) {
                    links[attributed.fullRange] = url
                }
            case "p":
                attributed.append(NSAttributedString(string: "\n\n"))
            case "em", "i":
                let currentFont: UIFont = attributed.attribute(.font, at: 0, effectiveRange: nil) as? UIFont ?? self.font
                attributed.addAttribute(.font, value: currentFont.addingTraits(.traitItalic), range: attributed.fullRange)
            case "strong", "b":
                let currentFont: UIFont = attributed.attribute(.font, at: 0, effectiveRange: nil) as? UIFont ?? self.font
                attributed.addAttribute(.font, value: currentFont.addingTraits(.traitBold), range: attributed.fullRange)
            case "del":
                attributed.addAttribute(.strikethroughStyle, value: NSUnderlineStyle.single.rawValue, range: attributed.fullRange)
            case "code":
                attributed.addAttribute(.font, value: UIFont(name: "Menlo", size: font!.pointSize)!, range: attributed.fullRange)
            case "pre":
                attributed.addAttribute(.font, value: UIFont(name: "Menlo", size: font!.pointSize)!, range: attributed.fullRange)
                attributed.append(NSAttributedString(string: "\n\n"))
            case "ol", "ul":
                attributed.trimLeadingCharactersInSet(.whitespacesAndNewlines)
                attributed.append(NSAttributedString(string: "\n"))
                break
            case "li":
                let parentEl = node.parent()!
                let parentTag = parentEl.tagName()
                let bullet: NSAttributedString
                if parentTag == "ol" {
                    let index = (try? node.elementSiblingIndex()) ?? 0
                    // we use the monospace digit font so that the periods of all the list items line up
                    bullet = NSAttributedString(string: "\(index + 1).\t", attributes: [.font: UIFont.monospacedDigitSystemFont(ofSize: font!.pointSize, weight: .regular)])
                } else if parentTag == "ul" {
                    bullet = NSAttributedString(string: "\u{2022}\t")
                } else {
                    bullet = NSAttributedString(string: "")
                }
                // inserting bullets at the beginning of the string shifts all the links down, so we adjust the link ranges
                for (range, url) in links {
                    let newRange = NSRange(location: range.location + bullet.length - 1, length: range.length)
                    links[newRange] = url
                    links.removeValue(forKey: range)
                }
                attributed.insert(bullet, at: 0)
                attributed.append(NSAttributedString(string: "\n"))
            default:
                break
            }
            
            return (attributed, links)
        default:
            fatalError("Unexpected node type: \(type(of: node))")
        }
    }
    
    func getViewController(forLink url: URL, inRange range: NSRange) -> UIViewController {
        let text = (self.text! as NSString).substring(with: range)
        
        if let mention = getMention(for: url, text: text) {
            return ProfileTableViewController(accountID: mention.id)
        } else if let tag = getHashtag(for: url, text: text) {
            return TimelineTableViewController(for: .tag(hashtag: tag.name))
        } else {
            return SFSafariViewController(url: url)
        }
    }
    
    func getViewController(forLinkAt point: CGPoint) -> UIViewController? {
        guard let link = getLink(atPoint: point) else {
            return nil
        }
        return getViewController(forLink: link.url, inRange: link.range)
    }
    
    // MARK: - Interaction
    
    override func linkTapped(_ link: LinkLabel.Link) {
        let text = (self.text! as NSString).substring(with: link.range)
        
        if let mention = getMention(for: link.url, text: text) {
            navigationDelegate?.selected(mention: mention)
        } else if let tag = getHashtag(for: link.url, text: text) {
            navigationDelegate?.selected(tag: tag)
        } else {
            navigationDelegate?.selected(url: link.url)
        }
    }
    
    override func linkLongPressed(_ link: LinkLabel.Link) {
        navigationDelegate?.showMoreOptions(forURL: link.url)
    }
    
    // MARK: - Navigation
    func getMention(for url: URL, text: String) -> Mention? {
        return nil
    }
    
    func getHashtag(for url: URL, text: String) -> Hashtag? {
        if text.starts(with: "#") {
            let tag = String(text.dropFirst())
            return Hashtag(name: tag, url: url)
        } else {
            return nil
        }
    }
    
}