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[rbdr/lyricli] / Sources / lyrics_engine.swift
1 import Foundation
2 import HTMLEntities
3
4 // Given a track, attempts to fetch the lyrics from lyricswiki
5 class LyricsEngine {
6
7 // URL of the API endpoint to use
8 private let apiURL = "https://lyrics.wikia.com/api.php?action=lyrics&func=getSong&fmt=realjson"
9
10 // Method used to call the API
11 private let apiMethod = "GET"
12
13 // Regular expxression used to find the lyrics in the lyricswiki HTML
14 private let lyricsMatcher = "class='lyricbox'>(.+)<div"
15
16 // The track we'll be looking for
17 private let track: Track
18
19 // Fetches the lyrics and returns if found
20 var lyrics: String? {
21
22 var lyrics: String?
23
24 // Encode the track artist and name and finish building the API call URL
25
26 if let artist = track.artist.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) {
27 if let name: String = track.name.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) {
28 if let url = URL(string: "\(apiURL)&artist=\(artist)&song=\(name)") {
29
30 // We'll lock until the async call is finished
31
32 var requestFinished = false
33 let asyncLock = NSCondition()
34 asyncLock.lock()
35
36 // Call the API and unlock when you're done
37
38 fetchLyricsFromAPI(withURL: url, completionHandler: {lyricsResult -> Void in
39 lyrics = lyricsResult
40 requestFinished = true
41 asyncLock.signal()
42 })
43
44 while !requestFinished {
45 asyncLock.wait()
46 }
47 asyncLock.unlock()
48 }
49 }
50 }
51
52 return lyrics
53 }
54
55 // Initializes with a track
56 init(withTrack targetTrack: Track) {
57
58 track = targetTrack
59 }
60
61 // Fetch the lyrics URL from the API, triggers the request to fetch the
62 // lyrics page
63 private func fetchLyricsFromAPI(withURL url: URL, completionHandler: @escaping (String?) -> Void) {
64
65 var apiRequest = URLRequest(url: url)
66 apiRequest.httpMethod = "GET"
67
68 let task = URLSession.shared.dataTask(with: apiRequest, completionHandler: {data, _, _ -> Void in
69
70 // If the response is parseable JSON, and has a url, we'll look for
71 // the lyrics in there
72
73 if let data = data {
74 if let jsonResponse = try? JSONSerialization.jsonObject(with: data) {
75 if let jsonResponse = jsonResponse as? [String: Any] {
76 if let lyricsUrlString = jsonResponse["url"] as? String {
77 if let lyricsUrl = URL(string: lyricsUrlString) {
78
79 // At this point we have a valid wiki url
80 self.fetchLyricsFromPage(withURL: lyricsUrl, completionHandler: completionHandler)
81 return
82 }
83 }
84 }
85 }
86 }
87
88 completionHandler(nil)
89 })
90 task.resume()
91 }
92
93 // Fetch the lyrics from the page and send it to the parser
94 private func fetchLyricsFromPage(withURL url: URL, completionHandler: @escaping (String?) -> Void) {
95
96 var pageRequest = URLRequest(url: url)
97 pageRequest.httpMethod = "GET"
98
99 let task = URLSession.shared.dataTask(with: pageRequest, completionHandler: {data, _, _ -> Void in
100
101 // If the response is parseable JSON, and has a url, we'll look for
102 // the lyrics in there
103
104 if let data = data {
105 if let htmlBody = String(data: data, encoding: String.Encoding.utf8) {
106 self.parseHtmlBody(htmlBody, completionHandler: completionHandler)
107 return
108 }
109 }
110
111 completionHandler(nil)
112 })
113 task.resume()
114 }
115
116 // Parses the wiki to find the lyrics, decodes the lyrics object
117 private func parseHtmlBody(_ body: String, completionHandler: @escaping (String?) -> Void) {
118
119 // Look for the lyrics lightbox
120
121 if let regex = try? NSRegularExpression(pattern: lyricsMatcher) {
122 let matches = regex.matches(in: body, range: NSRange(location: 0, length: body.characters.count))
123
124 for match in matches {
125
126 let nsBody = body as NSString
127 let range = match.rangeAt(1)
128 let encodedLyrics = nsBody.substring(with: range)
129
130 let decodedLyrics = decodeLyrics(encodedLyrics)
131
132 completionHandler(decodedLyrics)
133 return
134 }
135 }
136
137 completionHandler(nil)
138 }
139
140 // Escapes the HTML entities
141 private func decodeLyrics(_ lyrics: String) -> String {
142
143 let unescapedLyrics = lyrics.htmlUnescape()
144 return unescapedLyrics.replacingOccurrences(of: "<br />", with: "\n")
145 }
146 }