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import Foundation
import HTMLEntities
// Given a track, attempts to fetch the lyrics from lyricswiki
class LyricsEngine {
// URL of the API endpoint to use
private let apiURL = "https://lyrics.wikia.com/api.php?action=lyrics&func=getSong&fmt=realjson"
// Method used to call the API
private let apiMethod = "GET"
// Regular expxression used to find the lyrics in the lyricswiki HTML
private let lyricsMatcher = "class='lyricbox'>(.+)<div"
// 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: String = track.name.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) {
if let url = URL(string: "\(apiURL)&artist=\(artist)&song=\(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
fetchLyricsFromAPI(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 fetchLyricsFromAPI(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 lyricsUrlString = jsonResponse["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) {
// Look for the lyrics lightbox
if let regex = try? NSRegularExpression(pattern: lyricsMatcher) {
let matches = regex.matches(in: body, range: NSRange(location: 0, length: body.characters.count))
for match in matches {
let nsBody = body as NSString
let range = match.rangeAt(1)
let encodedLyrics = nsBody.substring(with: range)
let decodedLyrics = decodeLyrics(encodedLyrics)
completionHandler(decodedLyrics)
return
}
}
completionHandler(nil)
}
// Escapes the HTML entities
private func decodeLyrics(_ lyrics: String) -> String {
let unescapedLyrics = lyrics.htmlUnescape()
return unescapedLyrics.replacingOccurrences(of: "<br />", with: "\n")
}
}
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