/*
Copyright (c) 2001, 2002 Thai Open Source Software Center Ltd
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 name of the Thai Open Source Software Center Ltd 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 REGENTS 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.
*/
package com.sun.msv.util;

import java.io.UnsupportedEncodingException;
import java.net.MalformedURLException;
import java.net.URL;

public class Uri {
  private static String utf8 = "UTF-8";

  public static boolean isValid(String s) {
    return isValidPercent(s) && isValidFragment(s) && isValidScheme(s);
  }

  private static final String HEX_DIGITS = "0123456789abcdef";

  public static String escapeDisallowedChars(String s) {
    StringBuffer buf = null;
    int len = s.length();
    int done = 0;
    for (;;) {
      int i = done;
      for (;;) {
        if (i == len) {
          if (done == 0)
            return s;
          break;
        }
        if (isExcluded(s.charAt(i)))
          break;
        i++;
      }
      if (buf == null)
        buf = new StringBuffer();
      if (i > done) {
        buf.append(s.substring(done, i));
        done = i;
      }
      if (i == len)
        break;
      for (i++; i < len && isExcluded(s.charAt(i)); i++)
        ;
      String tem = s.substring(done, i);
      byte[] bytes;
      try {
        bytes = tem.getBytes(utf8);
      }
      catch (UnsupportedEncodingException e) {
        utf8 = "UTF8";
        try {
          bytes = tem.getBytes(utf8);
        }
        catch (UnsupportedEncodingException e2) {
          // Give up
          return s;
        }
      }
      for (int j = 0; j < bytes.length; j++) {
        buf.append('%');
        buf.append(HEX_DIGITS.charAt((bytes[j] & 0xFF) >> 4));
        buf.append(HEX_DIGITS.charAt(bytes[j] & 0xF));
      }
      done = i;
    }
    return buf.toString();
  }

  private static String excluded = "<>\"{}|\\^`";

  private static boolean isExcluded(char c) {
    return c <= 0x20 || c >= 0x7F || excluded.indexOf(c) >= 0;
  }

  private static boolean isAlpha(char c) {
    return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z');
  }

  private static boolean isHexDigit(char c) {
    return ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F') || isDigit(c);
  }

  private static boolean isDigit(char c) {
    return '0' <= c && c <= '9';
  }
  
  private static boolean isSchemeChar(char c) {
    return isAlpha(c) || isDigit(c) || c == '+' || c == '-' || c =='.';
  }

  private static boolean isValidPercent(String s) {
    int len = s.length();
    for (int i = 0; i < len; i++)
      if (s.charAt(i) == '%') {
        if (i + 2 >= len)
          return false;
        else if (!isHexDigit(s.charAt(i + 1))
             || !isHexDigit(s.charAt(i + 2)))
          return false;
      }
    return true;
  }

  private static boolean isValidFragment(String s) {
    int i = s.indexOf('#');
    return i < 0 || s.indexOf('#', i + 1) < 0;
  }

  private static boolean isValidScheme(String s) {
    if (!isAbsolute(s))
      return true;
    int i = s.indexOf(':');
    if (i == 0
    || i + 1 == s.length()
    || !isAlpha(s.charAt(0)))
      return false;
    while (--i > 0)
      if (!isSchemeChar(s.charAt(i)))
    return false;
    return true;
  }

  public static String resolve(String baseUri, String uriReference) {
    if (!isAbsolute(uriReference) && baseUri != null && isAbsolute(baseUri)) {
      try {
        return new URL(new URL(baseUri), uriReference).toString();
      }
      catch (MalformedURLException e) { }
    }
    return uriReference;
  }

  public static boolean hasFragmentId(String uri) {
    return uri.indexOf('#') >= 0;
  }

  public static boolean isAbsolute(String uri) {
    int i = uri.indexOf(':');
    if (i < 0)
      return false;
    while (--i >= 0) {
      switch (uri.charAt(i)) {
      case '#':
      case '/':
      case '?':
    return false;
      }
    }
    return true;
  }
}
