Tusker/Tusker/Views/StatusTableViewCell.swift

//
//  StatusTableViewCell.swift
//  Tusker
//
//  Created by Shadowfacts on 8/16/18.
//  Copyright © 2018 Shadowfacts. All rights reserved.
//

import UIKit
import MastodonKit
import SwiftSoup

class StatusTableViewCell: UITableViewCell {

    @IBOutlet weak var displayNameLabel: UILabel!
    @IBOutlet weak var usernameLabel: UILabel!
    @IBOutlet weak var contentLabel: UILabel!
    @IBOutlet weak var avatarImageView: UIImageView!
    
    var status: Status!
    
    var avatarURL: URL?
    
    var layoutManager: NSLayoutManager!
    var textContainer: NSTextContainer!
    var textStorage: NSTextStorage!
    
    var links: [NSRange: URL] = [:]
    
    func updateUI(for status: Status) {
        self.status = status
        
        let account: Account
        if let reblog = status.reblog {
            account = reblog.account
        } else {
            account = status.account
        }
        displayNameLabel.text = account.displayName
        usernameLabel.text = "@\(account.acct)"
        avatarImageView.layer.cornerRadius = 5
        avatarImageView.layer.masksToBounds = true
        avatarImageView.image = nil
        if let url = URL(string: account.avatar) {
            AvatarCache.shared.get(url) { image in
                DispatchQueue.main.async {
                    self.avatarImageView.image = image
                }
            }
        }
        
        
        let doc = try! SwiftSoup.parse(status.content)
        let body = doc.body()!
//        print("---")
//        print(status.content)
//        print("---")
        
        let (text, links) = attributedTextForNode(body)
        self.links = links
        contentLabel.attributedText = text
        contentLabel.isUserInteractionEnabled = true
        contentLabel.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(handleTapOnContentLabel(_:))))
        
        // https://stackoverflow.com/a/28519273/4731558
        layoutManager = NSLayoutManager()
        textContainer = NSTextContainer(size: .zero)
        textStorage = NSTextStorage(attributedString: text)
        
        layoutManager.addTextContainer(textContainer)
        textStorage.addLayoutManager(layoutManager)
        
        textContainer.lineFragmentPadding = 0
        textContainer.lineBreakMode = contentLabel.lineBreakMode
        textContainer.maximumNumberOfLines = contentLabel.numberOfLines
    }

    func attributedTextForNode(_ 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()
            node.getChildNodes().forEach { child in
                let (text, childLinks) = attributedTextForNode(child)
                childLinks.forEach { range, url in
                    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) {
                    let linkRange = NSRange(location: 0, length: attributed.length)
                    let linkAttributes: [NSAttributedString.Key: Any] = [
                        .foregroundColor: UIColor.blue
                    ]
                    attributed.setAttributes(linkAttributes, range: linkRange)
                    
                    links[linkRange] = url
                }
            default:
                break
            }
            
            return (attributed, links)
        default:
            fatalError("Unexpected node type: \(type(of: node))")
        }
    }
    
    @objc func handleTapOnContentLabel(_ tapGesture: UITapGestureRecognizer) {
        guard let view = tapGesture.view else { fatalError() }
        
        let locationOfTouchInLabel = tapGesture.location(in: view)
        let labelSize = view.bounds.size
        let textBoundingBox = layoutManager.usedRect(for: textContainer)
        let textContainerOffset = CGPoint(x: (labelSize.width - textBoundingBox.size.width) * 0.5 - textBoundingBox.origin.x,
                                          y: (labelSize.height - textBoundingBox.size.height) * 0.5 - textBoundingBox.origin.y)
        let locationOfTouchInTextContainer = CGPoint(x: locationOfTouchInLabel.x - textContainerOffset.x,
                                                     y: locationOfTouchInLabel.y - textContainerOffset.y)
        let indexOfCharacter = layoutManager.characterIndex(for: locationOfTouchInTextContainer, in: textContainer, fractionOfDistanceBetweenInsertionPoints: nil)
        
        let link = links.first { (range, _) -> Bool in
            range.contains(indexOfCharacter)
        }
        
        if let (_, url) = link {
            print("Open URL: \(url)")
        }
    }
    
    override func prepareForReuse() {
        if let url = avatarURL {
            AvatarCache.shared.cancel(url)
        }
    }

}