Tokenizer

package com.hypixel.hytale.server.core.command.system;

import com.hypixel.hytale.server.core.Message;
import it.unimi.dsi.fastutil.objects.ObjectArrayList;
import java.util.List;
import java.util.regex.Pattern;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;

public class Tokenizer {
   public static final char MULTI_ARG_SEPARATOR_CHAR = ',';
   public static final char MULTI_ARG_BEGIN_CHAR = '[';
   public static final char MULTI_ARG_END_CHAR = ']';
   public static final String MULTI_ARG_SEPARATOR = String.valueOf(',');
   public static final String MULTI_ARG_BEGIN = String.valueOf('[');
   public static final String MULTI_ARG_END = String.valueOf(']');
   private static final Message MESSAGE_COMMANDS_PARSING_ERROR_UNBALANCED_QUOTES = Message.translation("server.commands.parsing.error.unbalancedQuotes");

   public Tokenizer() {
   }

   @Nullable
   public static List<String> parseArguments(@Nonnull String input, @Nonnull ParseResult parseResult) {
      List<String> parsedTokens = new ObjectArrayList();
      String[] firstSplit = input.split(Pattern.quote(" "), 2);
      parsedTokens.add(firstSplit[0]);
      if (firstSplit.length == 1) {
         return parsedTokens;
      } else {
         String argsStr = firstSplit[1];
         char quote = 0;
         int tokenStart = 0;
         boolean inList = false;

         for (int i = 0; i < argsStr.length(); i++) {
            boolean extractToken;
            char c = argsStr.charAt(i);
            extractToken = false;
            label88:
            switch (c) {
               case ' ':
                  if (quote == 0) {
                     if (tokenStart < i) {
                        parsedTokens.add(argsStr.substring(tokenStart, i));
                     }

                     tokenStart = i + 1;
                  }
                  break;
               case '"':
                  if (quote == 0) {
                     quote = '"';
                  } else if (quote == '"') {
                     quote = 0;
                     String extraction = argsStr.substring(tokenStart, i + 1);
                     if (!extraction.isEmpty()) {
                        parsedTokens.add(extraction);
                     }

                     tokenStart = i + 1;
                  }
                  break;
               case '\'':
                  if (quote == 0) {
                     quote = '\'';
                  } else if (quote == '\'') {
                     quote = 0;
                     String extraction = argsStr.substring(tokenStart, i + 1);
                     if (!extraction.isEmpty()) {
                        parsedTokens.add(extraction);
                     }

                     tokenStart = i + 1;
                  }
                  break;
               case ',':
                  if (quote == 0) {
                     String extraction = argsStr.substring(tokenStart, i);
                     if (!extraction.isEmpty()) {
                        parsedTokens.add(extraction);
                     }

                     tokenStart = i;
                     extractToken = true;
                  }
                  break;
               case '[':
                  if (quote == 0) {
                     if (inList) {
                        parseResult.fail(Message.translation("server.commands.parsing.error.cannotBeginListInsideList").param("index", i));
                        return null;
                     }

                     inList = true;
                     tokenStart = i;
                     extractToken = true;
                  }
                  break;
               case '\\':
                  if (argsStr.length() <= i + 1) {
                     parseResult.fail(Message.translation("server.commands.parsing.error.invalidEscape").param("index", i + 1).param("input", input));
                     return null;
                  }

                  char nextCharacter = argsStr.charAt(i + 1);
                  switch (nextCharacter) {
                     case '"':
                     case '\'':
                     case ',':
                     case '[':
                     case '\\':
                     case ']':
                        argsStr = argsStr.substring(0, i) + argsStr.substring(i + 1);
                        i++;
                        break label88;
                     default:
                        parseResult.fail(
                           Message.translation("server.commands.parsing.error.invalidEscapeForSymbol")
                              .param("symbol", nextCharacter)
                              .param("index", i + 1)
                              .param("input", input)
                              .param("command", input)
                        );
                        return null;
                  }
               case ']':
                  if (quote == 0) {
                     if (!inList) {
                        parseResult.fail(Message.translation("server.commands.parsing.error.cannotEndListWithoutStarting").param("index", i));
                        return null;
                     }

                     String extraction = argsStr.substring(tokenStart, i);
                     if (!extraction.isEmpty()) {
                        parsedTokens.add(extraction);
                     }

                     tokenStart = i;
                     inList = false;
                     extractToken = true;
                  }
            }

            if (extractToken) {
               parsedTokens.add(argsStr.substring(tokenStart, i + 1));
               tokenStart = i + 1;
            }

            if (tokenStart > argsStr.length()) {
               tokenStart = argsStr.length();
               break;
            }
         }

         if (quote != 0) {
            parseResult.fail(MESSAGE_COMMANDS_PARSING_ERROR_UNBALANCED_QUOTES);
            return null;
         } else {
            if (tokenStart != argsStr.length()) {
               parsedTokens.add(argsStr.substring(tokenStart));
            }

            return parsedTokens;
         }
      }
   }
}