Add command similarity check to mapper (work in progress)

src/main/java/fr/xephi/authme/command/CommandMapper.java

@@ -1,6 +1,7 @@
 package fr.xephi.authme.command;
 
 import fr.xephi.authme.util.CollectionUtils;
+import fr.xephi.authme.util.StringUtils;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -10,6 +11,18 @@ import java.util.List;
  */
 public class CommandMapper {
 
+    /**
+     * The threshold for assuming an existing command. If the difference is below this value, we assume
+     * that the user meant the similar command and we will run it.
+     */
+    private static final double ASSUME_COMMAND_THRESHOLD = 0.12;
+
+    /**
+     * The threshold for suggesting a similar command. If the difference is below this value, we will
+     * ask the player whether he meant the similar command.
+     */
+    private static final double SUGGEST_COMMAND_THRESHOLD = 0.75;
+
     /**
      * Map incoming command parts to an actual command.
      *
@@ -26,25 +39,41 @@ public class CommandMapper {
             return null; // TODO Pass on the information that base could not be mapped
         }
 
-        //List<String> labels = CollectionUtils.getRange(parts, 0, 1);
         List<String> remaining = parts.subList(1, parts.size());
 
-        // Prefer labels: /register help goes to "Help command", not "Register command" with 'help'
+        // Prefer labels: /register help goes to "Help command", not "Register command" with argument 'help'
         CommandDescription childCommand = returnSuitableChild(base, remaining);
         if (childCommand != null) {
             // return childcommand: it's valid...
-        }
+        } else if (isSuitableArgumentCount(base, remaining.size())) {
-
-        // No child command found, check if parent is suitable
-        if (isSuitableArgumentCount(base, remaining.size())) {
             // return base... it's valid
         }
 
-        // TODO: We don't have a suitable command for the given parts, so find the most similar one
+        // TODO: return getCommandWithSmallestDifference()
         return null;
 
     }
 
+    // TODO: Return FoundCommandDescription immediately
+    private CommandDescription getCommandWithSmallestDifference(CommandDescription base, List<String> parts) {
+        final String label = parts.get(0);
+        final int argumentCount = parts.size() - 1;
+
+        double minDifference = Double.POSITIVE_INFINITY;
+        CommandDescription closestCommand = null;
+        for (CommandDescription child : base.getChildren()) {
+            double argumentDifference = getArgumentCountDifference(child, argumentCount);
+            double labelDifference = getLabelDifference(child, label);
+            // Weigh argument difference less
+            double difference = labelDifference + argumentCount / 2;
+            if (difference < minDifference) {
+                minDifference = difference;
+                closestCommand = child;
+            }
+        }
+        return closestCommand;
+    }
+
     private static boolean isSuitableArgumentCount(CommandDescription command, int argumentCount) {
         int minArgs = CommandUtils.getMinNumberOfArguments(command);
         int maxArgs = CommandUtils.getMaxNumberOfArguments(command);
@@ -52,13 +81,32 @@ public class CommandMapper {
         return argumentCount >= minArgs && argumentCount <= maxArgs;
     }
 
+    private static double getLabelDifference(CommandDescription command, String givenLabel) {
+        double minDifference = Double.POSITIVE_INFINITY;
+        for (String commandLabel : command.getLabels()) {
+            double difference = StringUtils.getDifference(commandLabel, givenLabel);
+            if (difference < minDifference) {
+                minDifference = difference;
+            }
+        }
+        return minDifference;
+    }
+
+    private static int getArgumentCountDifference(CommandDescription commandDescription, int givenArgumentsCount) {
+        return Math.min(
+            Math.abs(givenArgumentsCount - CommandUtils.getMinNumberOfArguments(commandDescription)),
+            Math.abs(givenArgumentsCount - CommandUtils.getMaxNumberOfArguments(commandDescription)));
+    }
+
     // Is the given command a suitable match for the given parts? parts is for example [changepassword, newpw, newpw]
     public CommandDescription returnSuitableChild(CommandDescription baseCommand, List<String> parts) {
-        // TODO: Validate list + make case-insensitive
+        if (CollectionUtils.isEmpty(parts)) {
+            return null;
+        }
+
         final String label = parts.get(0).toLowerCase();
         final int argumentCount = parts.size() - 1;
 
-        List<String> args = parts.subList(1, parts.size());
         for (CommandDescription child : baseCommand.getChildren()) {
             if (child.getLabels().contains(label) && isSuitableArgumentCount(child, argumentCount)) {
                 return child;