Merge pull request #14 from B00tLoad/documentation

Added documentation

src/main/java/de/b00tload/tools/lastfmtospotifyplaylist/LastFMToSpotify.java

@@ -38,9 +38,13 @@ public class LastFMToSpotify {
         configuration.put("requests.useragent", "LastFMToSpotify/1.0-Snapshot (" + System.getProperty("os.name") + "; " + System.getProperty("os.arch") + ") Java/" + System.getProperty("java.version"));
         configuration.put("playlist.name", "LastFMToSpotify@" + LocalDateTime.now(Clock.systemDefaultZone()).format(DateTimeFormatter.ISO_LOCAL_DATE_TIME));
         configuration.put("logging.level", "1");
+
+        //check whether all required arguments are set
         if (!ArgumentHandler.checkArguments(args)) {
             return;
         }
+
+        //check whether multiple arguments from an exclusive set are used
         if(!ArgumentHandler.checkExclusivity(args)){
             return;
         }
@@ -77,21 +81,29 @@ public class LastFMToSpotify {
             SpotifyApi api = build.build();
             AtomicBoolean waiting = new AtomicBoolean(true);
             if (configuration.containsKey("cache.crypto") && TokenHelper.existsTokens()) {
+                logLn("Cached credentials have been found.", 2);
+                logLn("Fetching old credentials, refreshing them and saving to cache", 2);
                 AuthorizationCodeCredentials oldcred = TokenHelper.fetchTokens();
-                AuthorizationCodeCredentials newcred = api.authorizationCodeRefresh(api.getClientId(), api.getClientSecret(), oldcred.getRefreshToken()).build().execute();
+                AuthorizationCodeCredentials newcred = api.authorizationCodeRefresh(api.getClientId(), api.getClientSecret(), oldcred.getRefreshToken()).setHeader("User-Agent", configuration.get("requests.useragent")).build().execute();
                 TokenHelper.saveTokens(newcred);
                 configuration.put("spotify.access", newcred.getAccessToken());
             } else {
                 try (Javalin webserver = Javalin.create().start(9876)) {
+                    if (configuration.containsKey("cache.crypto")) logLn("No cached credentials have been found.", 2);
+                    logLn("Starting webserver to initiate web based authentication.", 2);
                     Runtime.getRuntime().addShutdownHook(new Thread(webserver::stop));
 //                    webserver.exception(Exception.class, (exception, ctx) -> {
 //                        ctx.result(exception.getMessage());
 //                    });
                     webserver.get("/callback/spotify", ctx -> {
                         if(ctx.queryParamMap().containsKey("code")) {
-                            AuthorizationCodeCredentials cred = api.authorizationCode(ctx.queryParam("code")).build().execute();
+                            logLn("Received spotify authentication code. Requesting credentials.", 2);
+                            AuthorizationCodeCredentials cred = api.authorizationCode(ctx.queryParam("code")).setHeader("User-Agent", configuration.get("requests.useragent")).build().execute();
                             configuration.put("spotify.access", cred.getAccessToken());
-                            if(configuration.containsKey("cache.crypto")) TokenHelper.saveTokens(cred);
+                            if(configuration.containsKey("cache.crypto")) {
+                                logLn("Saving credentials to cache.", 2);
+                                TokenHelper.saveTokens(cred);
+                            }
                             ctx.result("success. <script>let win = window.open(null, '_self');win.close();</script>").contentType(ContentType.TEXT_HTML).status(HttpStatus.OK);
                             waiting.set(false);
                         } else {
@@ -111,12 +123,14 @@ public class LastFMToSpotify {
             logLn("Reading from LastFM...", 1);
             Collection<Track> tracks = User.getTopTracks(configuration.get("lastfm.user"), PeriodHelper.getPeriodByString(configuration.get("lastfm.period")), configuration.get("lastfm.apikey"));
             logLn("Creating Playlist...", 1);
+            logLn("... with custom playlistname (if set) and access modifiers (if set).", 2);
             api.setAccessToken(configuration.get("spotify.access"));
             Playlist list = api.createPlaylist(api.getCurrentUsersProfile().build().execute().getId(), configuration.get("playlist.name")).public_(configuration.containsKey("playlist.public")).collaborative(configuration.containsKey("playlist.collab")).setHeader("User-Agent", configuration.get("requests.useragent")).build().execute();
             List<String> adders = new LinkedList<>();
-            String charsToReplace = "[\"']"; //regex for " and '
+            String charsToReplace = "[\"']"; //regex removing " and ' because of issues with spotify search
+            logLn("Searching tracks from LastFM data on Spotify.", 2);
             for (Track track : tracks) {
-                logLn("Adding " + track.getName() + " by " + track.getArtist(), 3);
+                logLn("Searching " + track.getName() + " by " + track.getArtist(), 3);
                 StringBuilder searchQuery = new StringBuilder();
                 searchQuery.append("track:").append(track.getName().replaceAll(charsToReplace, ""));
                 searchQuery.append(" artist:").append(track.getArtist());
@@ -132,8 +146,10 @@ public class LastFMToSpotify {
                     }
                 }
             }
-            api.addItemsToPlaylist(list.getId(), adders.toArray(String[]::new)).build().execute();
+            logLn("Adding tracks to playlist.", 2);
+            api.addItemsToPlaylist(list.getId(), adders.toArray(String[]::new)).setHeader("User-Agent", configuration.get("requests.useragent")).build().execute();
             if(configuration.containsKey("playlist.cover")){
+                logLn("Setting playlist cover", 2);
                 logLn("Check for \"null\" if setting cover was successful: " + api.uploadCustomPlaylistCoverImage(list.getId()).image_data(configuration.get("playlist.cover")).setHeader("User-Agent", configuration.get("requests.useragent")).build().execute(),3);
             }
             logLn("Done.", 1);

src/main/java/de/b00tload/tools/lastfmtospotifyplaylist/arguments/ArgumentHandler.java

@@ -7,6 +7,7 @@ import de.umass.lastfm.Period;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
+import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.time.Clock;
@@ -24,6 +25,11 @@ import static de.b00tload.tools.lastfmtospotifyplaylist.util.Logger.logLn;
 import java.util.List;
 public class ArgumentHandler {
 
+    /**
+     * Selects which argument is handled by which method.
+     * @param argument the argument to handle
+     * @param value the value supplied with the argument
+     */
     public static void handle(Arguments argument, @Nullable String value) {
         switch (argument) {
             case HELP -> help(value);
@@ -45,11 +51,19 @@ public class ArgumentHandler {
         }
     }
 
+    /**
+     * Handles an argument without a value. Will pass <code>null</code> as value.
+     * @param argument the argument to handle without value
+     */
     public static void handle(Arguments argument) {
         handle(argument, null);
     }
 
-
+    /**
+     * Checks whether every required argument is used.
+     * @param args the <code>string[] args</code> passed to psvm.
+     * @return whether every required argument is used
+     */
     public static boolean checkArguments(String[] args) {
         // check if all required arguments are given
         Arguments[] required = {Arguments.SECRET, Arguments.CLIENT, Arguments.TOKEN, Arguments.USER};
@@ -72,6 +86,11 @@ public class ArgumentHandler {
         return true;
     }
 
+    /**
+     * Checks whether multiple arguments of an exclusivity group are used.
+     * @param args the <code>string[] args</code> passed to psvm.
+     * @return Whether only one argument out of every exclusivity group is given
+     */
     public static boolean checkExclusivity(String[] args){
         Arguments[][] exclusive = {{Arguments.PUBLIC, Arguments.COLLABORATIVE}, {Arguments.WEEKLY, Arguments.MONTHLY, Arguments.QUARTERLY, Arguments.BIANNUALLY, Arguments.YEARLY}};
         for(Arguments[] arguments : exclusive){
@@ -91,7 +110,12 @@ public class ArgumentHandler {
         return true;
     }
 
+    /**
+     * Displays help into the console.
+     * @param value The argument or alias to display help for.
+     */
     private static void help(String value) {
+        //evaluates whether an argument or alias is given. If not list of all arguments is displayed.
         if (value == null || value.isEmpty()) {
             logLn("This is a list of all available commands. For more specific help on the argument run --help <argument>.", 1);
             for (Arguments arg : Arguments.values()) {
@@ -103,11 +127,13 @@ public class ArgumentHandler {
             }
             System.exit(200);
         }
+        //resolves argument or alias. If no match is found tool will exit
         Arguments arg = Arguments.resolveByNameOrAlias(value);
         if (arg == null) {
             logLn("This argument is unknown. Use --help to get a list of all arguments", 1);
             System.exit(200);
         }
+        //Displays information about the selected argument
         String name = arg.getName();
         String description = arg.getDescription();
         String[] aliases = arg.getAliases();
@@ -121,10 +147,21 @@ public class ArgumentHandler {
         }
         logLn("    ALIASES:" + aliasString.substring(1), 1);
         logLn("____________________", 1);
+        //tool exits
         System.exit(200);
     }
 
+    /**
+     * Sets the log level.
+     *   - 0: Quiet      Will run completely quietly
+     *   - 1: Default    Will only show progress
+     *   - 2: Verbose    Will echo current step being worked on
+     *   - 3: Debug      Will give specific information on what excactly the tool is doing
+     * @param value an int 0 - 3
+     */
     private static void verbose(String value) {
+
+        //evaluates whether value is set
         if (value == null || value.isEmpty()) {
             logLn("--loglevel must be provided with a numeric log level. Check usage: " + Arguments.VERBOSE.getUsage(), 1);
             System.exit(500);
@@ -139,7 +176,12 @@ public class ArgumentHandler {
 
     }
 
+    /**
+     * Sets the LastFM api token into the configuration
+     * @param value The LastFM api token
+     */
     private static void token(String value) {
+        //evaluates whether value is set
         if (value == null || value.isEmpty()) {
             logLn("--lastfmtoken must be provided with an api token from LastFM. Check usage: " + Arguments.TOKEN.getUsage(), 1);
             System.exit(500);
@@ -147,7 +189,12 @@ public class ArgumentHandler {
         configuration.put("lastfm.apikey", value);
     }
 
+    /**
+     * Sets the LastFM username into the configuration
+     * @param value The LastFM username
+     */
     private static void user(String value) {
+        //evaluates whether value is set
         if (value == null || value.isEmpty()) {
             logLn("--lastfmuser must be provided with a LastFM username. Check usage: " + Arguments.USER.getUsage(), 1);
             System.exit(500);
@@ -155,7 +202,12 @@ public class ArgumentHandler {
         configuration.put("lastfm.user", value);
     }
 
+    /**
+     * Sets the spotify client id into the configuration
+     * @param value The Spotify Client ID
+     */
     private static void client(String value) {
+        //evaluates whether value is set
         if (value == null || value.isEmpty()) {
             logLn("--spotifyclient must be provided with a client id from Spotify. Check usage: " + Arguments.CLIENT.getUsage(), 1);
             System.exit(500);
@@ -163,7 +215,12 @@ public class ArgumentHandler {
         configuration.put("spotify.clientid", value);
     }
 
+    /**
+     * Sets the spotify client secret into the configuration
+     * @param value The Spotify Client Secret
+     */
     private static void secret(String value) {
+        //evaluates whether value is set
         if (value == null || value.isEmpty()) {
             logLn("--spotifysecret must be provided with a client secret from Spotify. Check usage: " + Arguments.SECRET.getUsage(), 1);
             System.exit(500);
@@ -171,20 +228,44 @@ public class ArgumentHandler {
         configuration.put("spotify.secret", value);
     }
 
+    /**
+     * Sets the Period to be loaded from LastFM. Possibilities: WEEKLY, MONTHLY, QUARTERLY, BIANNUALLY, YEARLY
+     * @param value the LastFM Period to be loaded
+     */
     private static void period(Period value) {
         configuration.put("lastfm.period", value.getString());
 
     }
 
+    /**
+     *  Takes a path to a jpeg image and turns it into base64 encoded image data which is subsequently saved into <code>playlist.cover</code> in the configuration.
+     * @param value The filepath to the cover image. Must be jpeg.
+     */
     private static void cover(String value) {
-        if (value == null || value.isEmpty() || !Files.exists(Path.of(value.replace("\\", "//")))) {
+        //evaluating if value is provided and of content-type image/jpeg
-            logLn("--coverart must be provided with a path to a png file. Check usage: " + Arguments.COVER.getUsage(), 1);
+        try {
+            if(value == null){
+                logLn("--coverart must be provided with a path to a jpeg file. Check usage: " + Arguments.COVER.getUsage(), 1);
                 System.exit(500);
             }
+            Path path = Path.of(value.replace("\\", "//"));
+            if (value.isEmpty() || !Files.exists(path) || !Files.probeContentType(path).equalsIgnoreCase("image/jpeg")) {
+                logLn("--coverart must be provided with a path to a jpeg file. Check usage: " + Arguments.COVER.getUsage(), 1);
+                System.exit(500);
+            }
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+        //encodes image data into base64
         String base64 = FileHelper.encodeFileToBase64(new File(value.replace("\\", "//")));
+        //saves to configuration
         configuration.put("playlist.cover", base64);
     }
 
+    /**
+     * Sets the access modifier. Can either be <code>"collaborative"</code> or <code>"public"</code>.
+     * @param value "collaborative" or "public"
+     */
     private static void access(String value) {
         switch (value) {
             case "collaborative" -> configuration.put("playlist.collab", "collab");
@@ -192,17 +273,27 @@ public class ArgumentHandler {
         }
     }
 
+    /**
+     * Sets the <code>playlist.name</code> value in the configuration. Supports templating and date offsetting. See <a href="https://github.com/B00tLoad/LastFMtoSpotifyPlaylist/wiki/Filename-Templating">wiki</a> for further documentation on templating.
+     * @param value The playlist name string, including templating
+     */
     private static void name(String value) {
+        //evaluating if value is provided
         if (value == null || value.isEmpty()) {
             logLn("--playlistname must be provided with a playlist name. Check usage: " + Arguments.NAME.getUsage(), 1);
             System.exit(500);
         }
+        //creating current datetime and users locale
         LocalDateTime now = LocalDateTime.now(Clock.systemDefaultZone());
         Locale loc = Locale.forLanguageTag(System.getProperty("user.country"));
+
+        //checking for the date offset flag and applying it if necessary
         if(value.matches("(%\\$-?\\d*\\$).*")){
             int offsetDays = Integer.parseInt(value.substring(2).split("\\$")[0]);
             now = offsetDays < 0 ?  now.minusDays(Math.abs(offsetDays)) : now.plusDays(Math.abs(offsetDays));
         }
+
+        //replacing datetime template
         String name = value.replace("%YYYY", String.valueOf(now.getYear())).replace("%YY", String.valueOf(now.getYear()).substring(2))
                 .replace("%MMMM", now.getMonth().name().charAt(0) + now.getMonth().name().toLowerCase().substring(1))
                 .replace("%MMM", now.getMonth().getDisplayName(TextStyle.FULL, loc))
@@ -231,7 +322,12 @@ public class ArgumentHandler {
         configuration.put("playlist.name", name);
     }
 
+    /**
+     * Sets the <code>cache.crypto</code> value in the configuration
+     * @param value a password encrypting the credential cache
+     */
     public static void cache(String value){
+        //evaluating if value is provided
         if (value == null || value.isEmpty()) {
             logLn("--spotifycache must be provided with a password. Check usage: " + Arguments.SPOTIFY_CACHING.getUsage(), 1);
             System.exit(500);

src/main/java/de/b00tload/tools/lastfmtospotifyplaylist/arguments/Arguments.java

@@ -6,6 +6,7 @@ import static de.b00tload.tools.lastfmtospotifyplaylist.LastFMToSpotify.LINE_SEP
 
 public enum Arguments {
 
+    //Defining arguments
     HELP("help", "[Optional, will not execute tool] " + LINE_SEPERATOR
             + "Shows a list of all commands or, if provided, help for a given command.", "--help [argument]", "h", "?"),
     VERBOSE("loglevel", "[Optional] " + LINE_SEPERATOR
@@ -73,6 +74,11 @@ public enum Arguments {
         return aliases;
     }
 
+    /**
+     * Resolves an alias-String into an Argument-object
+     * @param alias The alias to resolve
+     * @return The resolved Argument, null if alias does not exist.
+     */
     public static Arguments getByAlias(String alias){
         for(Arguments arg : values()){
             if(List.of(arg.getAliases()).contains(alias)) return arg;
@@ -80,6 +86,11 @@ public enum Arguments {
         return null;
     }
 
+    /**
+     * Resolves an argument-String into an Argument-object
+     * @param name The argument to resolve
+     * @return The resolved Argument, null if alias does not exist.
+     */
     public static Arguments getByName(String name){
         for(Arguments arg : values()){
             if(arg.getName().equalsIgnoreCase(name)) return arg;
@@ -87,6 +98,11 @@ public enum Arguments {
         return null;
     }
 
+    /**
+     * Resolves an argument- or alias-String into an Argument-object
+     * @param v The alias or argument to resolve
+     * @return The resolved Argument, null if alias does not exist.
+     */
     public static Arguments resolveByNameOrAlias(String v){
         Arguments ret = getByName(v);
         if(ret != null) return ret;
@@ -94,6 +110,10 @@ public enum Arguments {
         return ret;
     }
 
+    /**
+     * Builds a String consisting of the argument name and all aliases listed
+     * @return "--$argument ($aliases)"
+     */
     @Override
     public String toString() {
         StringBuilder args = new StringBuilder("--").append(this.name).append(" (");

src/main/java/de/b00tload/tools/lastfmtospotifyplaylist/util/CryptoHelper.java

@@ -15,18 +15,28 @@ import java.security.spec.KeySpec;
 
 public class CryptoHelper {
 
+    /**
+     * Creates a <code>javax.crypto.SecretKey</code> from a provided password
+     * @param pass The password
+     * @return the generated secret key
+     */
     public static SecretKey createKeyFromPassword(String pass){
         try {
             KeySpec spec = new PBEKeySpec(pass.toCharArray(), "abcdefghijklmnop".getBytes(), 65536, 256); // AES-256
             SecretKeyFactory f = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
-            byte[] key = new byte[0];
+            byte[] key = f.generateSecret(spec).getEncoded();
-            key = f.generateSecret(spec).getEncoded();
             return new SecretKeySpec(key, "AES");
         } catch (InvalidKeySpecException | NoSuchAlgorithmException e) {
             throw new RuntimeException(e);
         }
     }
 
+    /**
+     * Saves a <code>java.io.Serializable</code> Object into an encrypted file
+     * @param obj The object to save
+     * @param file The Path where to save the file
+     * @param key The SecretKey (AES) to encrypt the file with
+     */
     public static void serializeEncrypted(Serializable obj, Path file, SecretKey key){
         try {
             if(file.toFile().exists()) file.toFile().delete();
@@ -45,8 +55,14 @@ public class CryptoHelper {
         }
     }
 
+    /**
+     * Reads an encrypted file into a <code>java.io.Serializable</code> object.
+     * @param file The <code>java.nio.Path</code> where the encrypted file is stored.
+     * @param key The SecretKey (AES) to decrypt the file with
+     * @return The <code>java.io.Serializable</code> object read from the file.
+     */
     public static Serializable deserializeEncrypted(Path file, SecretKey key) {
-        Serializable ret = null;
+        Serializable ret;
         try {
             Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
             IvParameterSpec iv = new IvParameterSpec("abcdefghijklmnop".getBytes());

src/main/java/de/b00tload/tools/lastfmtospotifyplaylist/util/FileHelper.java

@@ -7,6 +7,11 @@ import java.util.Base64;
 
 public class FileHelper {
 
+    /**
+     * Reads a file and encodes it into Base64
+     * @param file The file to read
+     * @return A Base64 encoded String containing the data of the file
+     */
     public static String encodeFileToBase64(File file){
         String encodedfile = null;
         try (FileInputStream fileInputStreamReader = new FileInputStream(file)){

src/main/java/de/b00tload/tools/lastfmtospotifyplaylist/util/Logger.java

@@ -4,6 +4,11 @@ import static de.b00tload.tools.lastfmtospotifyplaylist.LastFMToSpotify.configur
 
 public class Logger {
 
+    /**
+     * Logs the provided String to console if the option <code>logging.level</code> in the configuration is higher or equal to the provided priority
+     * @param string The String to log
+     * @param priority The minimum logging level with which the provided string should be logged
+     */
     public static void logLn(String string, int priority){
         if(Integer.parseInt(configuration.get("logging.level"))>=priority){
             System.out.println(string);

src/main/java/de/b00tload/tools/lastfmtospotifyplaylist/util/PeriodHelper.java

@@ -4,6 +4,11 @@ import de.umass.lastfm.Period;
 
 public class PeriodHelper {
 
+    /**
+     * Converts a provided String (<code>de.umass.lastfm.Period.getString()</code>) into the corresponding <code>de.umass.lastfm.Period</code>
+     * @param string The value to be converted into a <code>de.umass.lastfm.Period</code>
+     * @return The converted <code>de.umass.lastfm.Period</code>, defaults to <code>de.umass.lastfm.Period.ONE_MONTH</code>
+     */
     public static Period getPeriodByString(String string){
         for(Period p : Period.values()){
             if(p.getString().equalsIgnoreCase(string)) return p;

src/main/java/de/b00tload/tools/lastfmtospotifyplaylist/util/TimeHelper.java

@@ -5,19 +5,33 @@ import java.time.ZoneId;
 
 public class TimeHelper {
 
+    /**
+     * Gets the hours of the UTC offset from a LocalDateTime, which is asserted to be at the system default Timezone (<code>ZoneId.systemDefault()</code>)
+     * @param now The <code>java.time.LocalDateTime</code> for which the offset should be calculated
+     * @return The hours of offset from UTC
+     */
     public static int getUTCOffsetHours(LocalDateTime now){
-
         return (int) Math.floor((double) now.atZone(ZoneId.systemDefault()).getOffset().getTotalSeconds()/3600);
     }
 
+    /**
+     * Gets the minutes of the UTC offset from a LocalDateTime, which is asserted to be at the system default Timezone (<code>ZoneId.systemDefault()</code>)
+     * @param now The <code>java.time.LocalDateTime</code> for which the offset should be calculated
+     * @return The minutes of offset from UTC
+     */
     public static int getUTCOffsetMinutes(LocalDateTime now){
         return (now.atZone(ZoneId.systemDefault()).getOffset().getTotalSeconds()/60);
     }
 
+    /**
+     * Generates an ISO 8601 complying String containing the UTC offset from a LocalDateTime, which is asserted to be at the system default Timezone (<code>ZoneId.systemDefault()</code>)
+     * @param now The <code>java.time.LocalDateTime</code> for which the offset should be calculated
+     * @return an ISO 8601 complying String containing the UTC offset (e.g. "+01:00")
+     */
     public static String getUTCOffset(LocalDateTime now){
         int hour = getUTCOffsetHours(now);
         String h = (hour == Math.abs(hour) ? "+" : "-") + (String.valueOf(Math.abs(hour)).length() == 1 ? "0" + Math.abs(hour) : String.valueOf(Math.abs(hour)));
-        int min = Math.abs(getUTCOffsetMinutes(now))-(Math.abs(hour)*60);
+        int min = Math.abs(getUTCOffsetMinutes(now))%(Math.abs(hour));
         String m = (String.valueOf(Math.abs(min)).length() == 1 ? "0" + Math.abs(min) : String.valueOf(Math.abs(min)));
         return h + ":" + m;
     }

src/main/java/de/b00tload/tools/lastfmtospotifyplaylist/util/TokenHelper.java

@@ -8,14 +8,27 @@ import static de.b00tload.tools.lastfmtospotifyplaylist.LastFMToSpotify.USER_HOM
 import static de.b00tload.tools.lastfmtospotifyplaylist.LastFMToSpotify.configuration;
 
 public class TokenHelper {
+
+    /**
+     * Manages saving a <code>se.michaelthelin.spotify.model_objects.credentials.AuthorizationCodeCredentials</code> into "~/.lfm2s/spotify.lfm2scred" using <code>de.b00tload.tools.lastfmtospotifyplaylist.util.CryptoHelper.serializeEncrypted(...)</code>
+     * @param cred The <code>se.michaelthelin.spotify.model_objects.credentials.AuthorizationCodeCredentials</code> to be saved
+     */
     public static void saveTokens(AuthorizationCodeCredentials cred) {
         CryptoHelper.serializeEncrypted(cred, Path.of(USER_HOME, "/.lfm2s/spotify.lfm2scred"), CryptoHelper.createKeyFromPassword(configuration.get("cache.crypto")));
     }
 
+    /**
+     * Manages retrieving a <code>se.michaelthelin.spotify.model_objects.credentials.AuthorizationCodeCredentials</code> from "~/.lfm2s/spotify.lfm2scred" using <code>de.b00tload.tools.lastfmtospotifyplaylist.util.CryptoHelper.deserializeEncrypted(...)</code>
+     * @return The retrieved <code>se.michaelthelin.spotify.model_objects.credentials.AuthorizationCodeCredentials</code>
+     */
     public static AuthorizationCodeCredentials fetchTokens() {
         return (AuthorizationCodeCredentials) CryptoHelper.deserializeEncrypted(Path.of(USER_HOME, "/.lfm2s/spotify.lfm2scred"), CryptoHelper.createKeyFromPassword(configuration.get("cache.crypto")));
     }
 
+    /**
+     * Checks whether the saved spotify AuthorizationCodeCredentials at "~/.lfm2s/spotify.lfm2scred" exist
+     * @return true if file exists, false if not
+     */
     public static boolean existsTokens(){
         return Path.of(USER_HOME, "/.lfm2s/spotify.lfm2scred").toFile().exists();
     }