code improvements

Author: LabyStudio

src/main/java/de/labystudio/spotifyapi/open/OpenSpotifyAPI.java

@@ -61,6 +61,11 @@ private void generateAccessTokenAsync(Consumer<AccessTokenResponse> callback) {
         });
     }
 
+    /**
+     * Request server time of Spotify for time-based one time password
+     *
+     * @return server time in seconds
+     */
     public long requestServerTime() throws IOException {
         // Get server time
         URL url = new URL(URL_API_SERVER_TIME);
@@ -78,22 +83,33 @@ public long requestServerTime() throws IOException {
         return obj.get("serverTime").getAsLong();
     }
 
+    /**
+     * Generate time-based one time password
+     *
+     * @param serverTime server time in seconds
+     * @return 6 digits one time password
+     */
     public String generateTotp(long serverTime) {
+        // Convert secret numbers to xor results
         StringBuilder xorResults = new StringBuilder();
         for (int i = 0; i < TOTP_SECRET.length; i++) {
             int result = TOTP_SECRET[i] ^ (i % 33 + 9);
             xorResults.append(result);
         }
+
+        // Convert xor results to hex
         StringBuilder hexResult = new StringBuilder();
         for (int i = 0; i < xorResults.length(); i++) {
             hexResult.append(String.format("%02x", (int) xorResults.charAt(i)));
         }
+
+        // Convert hex to byte array
         byte[] byteArray = new byte[hexResult.length() / 2];
         for (int i = 0; i < hexResult.length(); i += 2) {
             int byteValue = Integer.parseInt(hexResult.substring(i, i + 2), 16);
             byteArray[i / 2] = (byte) byteValue;
         }
-        return TOTP.generateOtp(byteArray, serverTime);
+        return TOTP.generateOtp(byteArray, serverTime, 30, 6);
     }
 
     /**
@@ -116,10 +132,6 @@ private AccessTokenResponse generateAccessToken() throws IOException {
         return response;
     }
 
-    private boolean hasValidAccessToken(AccessTokenResponse response) {
-        return response != null && response.accessToken != null && !response.accessToken.isEmpty();
-    }
-
     /**
      * Retrieve access token using totp
      */
@@ -377,6 +389,10 @@ public <T> T request(String url, Class<?> clazz, boolean canGenerateNewAccessTok
         return GSON.fromJson(reader, clazz);
     }
 
+    private boolean hasValidAccessToken(AccessTokenResponse response) {
+        return response != null && response.accessToken != null && !response.accessToken.isEmpty();
+    }
+
     public Cache<BufferedImage> getImageCache() {
         return this.imageCache;
     }

src/main/java/de/labystudio/spotifyapi/open/util/Base32.java

@@ -11,11 +11,17 @@ public class TOTP {
 
     private static final String DEFAULT_ALGORITHM = "HmacSHA1";
 
-    private static final int DEFAULT_DIGITS = 6;
-    private static final int DEFAULT_PERIOD = 30;
-
-    public static String generateOtp(byte[] secret, long time) {
-        long counter = time / DEFAULT_PERIOD;
+    /**
+     * Generate a TOTP (Time-based One-Time Password) using the given secret, time, period, and number of digits.
+     *
+     * @param secret The secret key
+     * @param time   The time in milliseconds
+     * @param period The period in seconds
+     * @param digits The number of digits
+     * @return The generated TOTP
+     */
+    public static String generateOtp(byte[] secret, long time, int period, int digits) {
+        long counter = time / period;
 
 
         // Convert counter to byte array (Big Endian)
@@ -38,10 +44,10 @@ public static String generateOtp(byte[] secret, long time) {
                     (hmac[offset + 3] & 0xFF);
 
             // Compute OTP
-            int otp = binary % ((int) Math.pow(10, DEFAULT_DIGITS));
+            int otp = binary % ((int) Math.pow(10, digits));
 
             // Return zero-padded OTP
-            return String.format("%0" + DEFAULT_DIGITS + "d", otp);
+            return String.format("%0" + digits + "d", otp);
         } catch (NoSuchAlgorithmException | InvalidKeyException e) {
             throw new IllegalStateException("Failed to generate TOTP", e);
         }