Implement the lyrics engine

1 files changed, 126 insertions, 4 deletions

diff --git a/Sources/lyrics_engine.swift b/Sources/lyrics_engine.swift
index 661ce86..d6b1985 100644
--- a/Sources/lyrics_engine.swift
+++ b/Sources/lyrics_engine.swift
@@ -1,15 +1,51 @@
+import Foundation
+import HTMLEntities
+
 /// Looks for lyrics on the internet
 class LyricsEngine {
 
-    let track: Track
+    private let apiURL = "https://lyrics.wikia.com/api.php?action=lyrics&func=getSong&fmt=realjson"
+    private let apiMethod = "GET"
+    private let lyricsMatcher = "class='lyricbox'>(.+)<div"
+
+    private let track: Track
+
+    // Fetches the lyrics and returns if found
 
     var lyrics: String? {
         get {
-            if track.artist == "test" && track.name == "test" {
-                return "Doo doo doo"
+
+            var lyrics: String?
+
+            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
+                            if let lyricsResult = lyricsResult {
+                                lyrics = lyricsResult
+                                requestFinished = true
+                                asyncLock.signal()
+                            }
+                        })
+
+                        while(!requestFinished) {
+                            asyncLock.wait()
+                        }
+                        asyncLock.unlock()
+                    }
+                }
             }
 
-            return nil
+            return lyrics
         }
     }
 
@@ -17,4 +53,90 @@ class LyricsEngine {
 
         track = targetTrack
     }
+
+    // Fetch the lyrics from the API and request / parse the 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, response, error -> Void in
+
+            // If the response is parseable JSON, and has a url, we'll look for
+            // the lyrics in there
+
+            if let data = data {
+                let jsonResponse = try? JSONSerialization.jsonObject(with: data) as! [String: Any]
+                if let jsonResponse = jsonResponse {
+                    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 parse the page
+
+    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, response, error -> 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 obtain the lyrics
+
+    private func parseHtmlBody(_ body: String, completionHandler: @escaping (String?) -> Void) {
+
+        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")
+    }
 }