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 TTTAttributedLabel
import Pachyderm
import SwiftSoup

class ContentLabel: LinkLabel {
    
    var navigationDelegate: TuskerNavigationDelegate?
    
    // 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)
        
        mutAttrString.addAttribute(.font, value: font, range: NSRange(location: 0, length: mutAttrString.length))
        
        let linkAttributes: [NSAttributedString.Key: Any] = [
            .foregroundColor: UIColor.blue,
        ]
        
        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) {
                    let linkRange = NSRange(location: 0, length: attributed.length)
                    links[linkRange] = url
                }
            case "p":
                attributed.append(NSAttributedString(string: "\n\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
        }
    }
    
}