/* Copyright (c) 2020, D. R. Commander
 * Copyright (c) 2001-2010, JavaPLT group at Rice University (drjava@rice.edu)
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the names of DrJava, the JavaPLT group, Rice University, nor the
 *     names of its contributors may be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This file was part of DrJava.  Download the current version of this project
 * from http://www.drjava.org/ or http://sourceforge.net/projects/drjava/
 */

package com.turbovnc.vncviewer;

import java.util.List;
import java.util.LinkedList;

import com.turbovnc.rfb.Utils;

/**
 * Utility class which can tokenize a String into a list of String arguments,
 * with behavior similar to parsing command line arguments to a program.
 * Quoted Strings are treated as single arguments, and escaped characters
 * are translated so that the tokenized arguments have the same meaning.
 * Since all methods are static, the class is declared abstract to prevent
 * instantiation.
 * @version $Id$
 */
public abstract class ArgumentTokenizer {
  private static final int NO_TOKEN_STATE = 0;
  private static final int NORMAL_TOKEN_STATE = 1;
  private static final int SINGLE_QUOTE_STATE = 2;
  private static final int DOUBLE_QUOTE_STATE = 3;

  /** Tokenizes the given String into String tokens
    * @param arguments A String containing one or more command-line style
    * arguments to be tokenized.
    * @return A list of parsed and properly escaped arguments.
    */
  public static List<String> tokenize(String arguments) {
    return tokenize(arguments, false);
  }

  /** Tokenizes the given String into String tokens.
    * @param arguments A String containing one or more command-line style
    * arguments to be tokenized.
    * @param stringify whether or not to include escape special characters
    * @return A list of parsed and properly escaped arguments.
    */
  public static List<String> tokenize(String arguments, boolean stringify) {

    LinkedList<String> argList = new LinkedList<String>();
    StringBuilder currArg = new StringBuilder();
    boolean escaped = false;
    int state = NO_TOKEN_STATE;  // start in the NO_TOKEN_STATE
    int len = arguments.length();

    // Loop over each character in the string
    for (int i = 0; i < len; i++) {
      char c = arguments.charAt(i);
      if (escaped) {
        // Escaped state: just append the next character to the current arg.
        escaped = false;
        currArg.append(c);
      } else {
        switch (state) {
          case SINGLE_QUOTE_STATE:
            if (c == '\'') {
              // Seen the close quote; continue this arg until whitespace is
              // seen
              state = NORMAL_TOKEN_STATE;
            } else {
              currArg.append(c);
            }
            break;
          case DOUBLE_QUOTE_STATE:
            if (c == '"') {
              // Seen the close quote; continue this arg until whitespace is
              // seen
              state = NORMAL_TOKEN_STATE;
            } else if (c == '\\' && !Utils.isWindows()) {
              // Look ahead, and only escape quotes or backslashes
              i++;
              char next = arguments.charAt(i);
              if (next == '"' || next == '\\') {
                currArg.append(next);
              } else {
                currArg.append(c);
                currArg.append(next);
              }
            } else {
              currArg.append(c);
            }
            break;
          case NO_TOKEN_STATE:
          case NORMAL_TOKEN_STATE:
            switch (c) {
              case '\\':
                if (Utils.isWindows())
                  currArg.append(c);
                else
                  escaped = true;
                state = NORMAL_TOKEN_STATE;
                break;
              case '\'':
                state = SINGLE_QUOTE_STATE;
                break;
              case '"':
                state = DOUBLE_QUOTE_STATE;
                break;
              default:
                if (!Character.isWhitespace(c)) {
                  currArg.append(c);
                  state = NORMAL_TOKEN_STATE;
                } else if (state == NORMAL_TOKEN_STATE) {
                  // Whitespace ends the token; start a new one
                  argList.add(currArg.toString());
                  currArg = new StringBuilder();
                  state = NO_TOKEN_STATE;
                }
            }
            break;
          default:
            throw new IllegalStateException("ArgumentTokenizer state " +
                                            state + " is invalid!");
        }
      }
    }

    // If we're still escaped, put in the backslash
    if (escaped) {
      currArg.append('\\');
      argList.add(currArg.toString());
    // Close the last argument if we haven't yet
    } else if (state != NO_TOKEN_STATE) {
      argList.add(currArg.toString());
    }
    // Format each argument if we've been told to stringify them
    if (stringify) {
      for (int i = 0; i < argList.size(); i++) {
        argList.set(i, "\"" + escapeQuotesAndBackslashes(argList.get(i)) +
                    "\"");
      }
    }
    return argList;
  }

  /** Inserts backslashes before any occurrences of a backslash or
   * quote in the given string.  Also converts any special characters
   * appropriately.
   */
  protected static String escapeQuotesAndBackslashes(String s) {
    final StringBuilder buf = new StringBuilder(s);

    // Walk backwards, looking for quotes or backslashes.
    //  If we see any, insert an extra backslash into the buffer at
    //  the same index.  (By walking backwards, the index into the buffer
    //  will remain correct as we change the buffer.)
    for (int i = s.length() - 1; i >= 0; i--) {
      char c = s.charAt(i);
      if ((c == '\\') || (c == '"')) {
        buf.insert(i, '\\');
      // Replace any special characters with escaped versions
      } else if (c == '\n') {
        buf.deleteCharAt(i);
        buf.insert(i, "\\n");
      } else if (c == '\t') {
        buf.deleteCharAt(i);
        buf.insert(i, "\\t");
      } else if (c == '\r') {
        buf.deleteCharAt(i);
        buf.insert(i, "\\r");
      } else if (c == '\b') {
        buf.deleteCharAt(i);
        buf.insert(i, "\\b");
      } else if (c == '\f') {
        buf.deleteCharAt(i);
        buf.insert(i, "\\f");
      }
    }
    return buf.toString();
  }
}
