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[rbdr/lyricli] / Sources / lyricli / lyrics_engine.swift

import Foundation
import SwiftSoup

// Given a track, attempts to fetch the lyrics from lyricswiki
class LyricsEngine {

    private let clientToken = <GENIUS_CLIENT_TOKEN>

    // URL of the API endpoint to use
    private let apiURL = "https://api.genius.com/search"

    // Method used to call the API
    private let apiMethod = "GET"

    // The track we'll be looking for
    private let track: Track

    // Fetches the lyrics and returns if found
    var lyrics: String? {

        var lyrics: String?

        // Encode the track artist and name and finish building the API call URL

        if let artist = track.artist.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) {
            if let name = track.name.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) {

                if let url = URL(string: "\(apiURL)?access_token=\(clientToken)&q=\(artist)%20\(name)") {

                    // We'll lock until the async call is finished

                    var requestFinished = false
                    let asyncLock = NSCondition()
                    asyncLock.lock()

                    // Call the API and unlock when you're done

                    searchLyricsUsingAPI(withURL: url, completionHandler: {lyricsResult -> Void in
                        lyrics = lyricsResult
                        requestFinished = true
                        asyncLock.signal()
                    })

                    while !requestFinished {
                        asyncLock.wait()
                    }
                    asyncLock.unlock()
                }
            }
        }

        return lyrics
    }

    // Initializes with a track
    init(withTrack targetTrack: Track) {

        track = targetTrack
    }

    // Fetch the lyrics URL from the API, triggers the request to fetch the
    // lyrics page
    private func searchLyricsUsingAPI(withURL url: URL, completionHandler: @escaping (String?) -> Void) {

        var apiRequest = URLRequest(url: url)
        apiRequest.httpMethod = "GET"

        let task = URLSession.shared.dataTask(with: apiRequest, completionHandler: {data, _, _ -> Void in

            // If the response is parseable JSON, and has a url, we'll look for
            // the lyrics in there

            if let data = data {
                if let jsonResponse = try? JSONSerialization.jsonObject(with: data) {
                    if let jsonResponse = jsonResponse as? [String: Any] {
                        if let response = jsonResponse["response"] as? [String: Any] {
                            if let hits = response["hits"] as? [[String: Any]] {
                                let filteredHits = hits.filter { $0["type"] as? String == "song" }
                                if filteredHits.count > 0 {
                                    let firstHit = hits[0]
                                    if let firstHitData = firstHit["result"] as? [String: Any] {
                                        if let lyricsUrlString = firstHitData["url"] as? String {
                                            if let lyricsUrl = URL(string: lyricsUrlString) {

                                                // At this point we have a valid wiki url
                                                self.fetchLyricsFromPage(
                                                    withURL: lyricsUrl,
                                                    completionHandler: completionHandler
                                                )
                                                return
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }

            completionHandler(nil)
        })
        task.resume()
    }

    // Fetch the lyrics from the page and send it to the parser
    private func fetchLyricsFromPage(withURL url: URL, completionHandler: @escaping (String?) -> Void) {

        var pageRequest = URLRequest(url: url)
        pageRequest.httpMethod = "GET"

        let task = URLSession.shared.dataTask(with: pageRequest, completionHandler: {data, _, _ -> Void in

            // If the response is parseable JSON, and has a url, we'll look for
            // the lyrics in there

            if let data = data {
                if let htmlBody = String(data: data, encoding: String.Encoding.utf8) {
                    self.parseHtmlBody(htmlBody, completionHandler: completionHandler)
                    return
                }
            }

            completionHandler(nil)
        })
        task.resume()
    }

    // Parses the wiki to find the lyrics, decodes the lyrics object
    private func parseHtmlBody(_ body: String, completionHandler: @escaping (String?) -> Void) {

        do {
            let document: Document = try SwiftSoup.parse(body)
            let lyricsBox = try document.select("div[data-lyrics-container=\"true\"]")
            try lyricsBox.select("br").after("\\n")
            let lyrics = try lyricsBox.text()
            completionHandler(lyrics.replacingOccurrences(of: "\\n", with: "\r\n"))
        } catch {
            completionHandler(nil)
        }
    }
}