/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.util;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.nio.charset.Charset;
import java.util.BitSet;

This class is very similar to the java.net.URLEncoder class.
Unfortunately, with java.net.URLEncoder there is no way to specify to the
java.net.URLEncoder which characters should NOT be encoded.
This code was moved from DefaultServlet.java
Author:
Craig R. McClanahan, Remy Maucherat/**
 *
 * This class is very similar to the java.net.URLEncoder class.
 *
 * Unfortunately, with java.net.URLEncoder there is no way to specify to the
 * java.net.URLEncoder which characters should NOT be encoded.
 *
 * This code was moved from DefaultServlet.java
 *
 * @author Craig R. McClanahan
 * @author Remy Maucherat
 */
public final class URLEncoder implements Cloneable {

    private static final char[] hexadecimal =
            {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

    public static final URLEncoder DEFAULT = new URLEncoder();
    public static final URLEncoder QUERY = new URLEncoder();

    static {
        /*
         * Encoder for URI paths, so from the spec:
         *
         * pchar = unreserved / pct-encoded / sub-delims / ":" / "@"
         *
         * unreserved  = ALPHA / DIGIT / "-" / "." / "_" / "~"
         *
         * sub-delims = "!" / "$" / "&" / "'" / "(" / ")"
         *              / "*" / "+" / "," / ";" / "="
         */
        // ALPHA and DIGIT are always treated as safe characters
        // Add the remaining unreserved characters
        DEFAULT.addSafeCharacter('-');
        DEFAULT.addSafeCharacter('.');
        DEFAULT.addSafeCharacter('_');
        DEFAULT.addSafeCharacter('~');
        // Add the sub-delims
        DEFAULT.addSafeCharacter('!');
        DEFAULT.addSafeCharacter('$');
        DEFAULT.addSafeCharacter('&');
        DEFAULT.addSafeCharacter('\'');
        DEFAULT.addSafeCharacter('(');
        DEFAULT.addSafeCharacter(')');
        DEFAULT.addSafeCharacter('*');
        DEFAULT.addSafeCharacter('+');
        DEFAULT.addSafeCharacter(',');
        DEFAULT.addSafeCharacter(';');
        DEFAULT.addSafeCharacter('=');
        // Add the remaining literals
        DEFAULT.addSafeCharacter(':');
        DEFAULT.addSafeCharacter('@');
        // Add '/' so it isn't encoded when we encode a path
        DEFAULT.addSafeCharacter('/');

        /*
         * Encoder for query strings
         * https://www.w3.org/TR/html5/forms.html#application/x-www-form-urlencoded-encoding-algorithm
         * 0x20 ' ' -> '+'
         * 0x2A, 0x2D, 0x2E, 0x30 to 0x39, 0x41 to 0x5A, 0x5F, 0x61 to 0x7A as-is
         * '*',  '-',  '.',  '0'  to '9',  'A'  to 'Z',  '_',  'a'  to 'z'
         * Also '=' and '&' are not encoded
         * Everything else %nn encoded
         */
        // Special encoding for space
        QUERY.setEncodeSpaceAsPlus(true);
        // Alpha and digit are safe by default
        // Add the other permitted characters
        QUERY.addSafeCharacter('*');
        QUERY.addSafeCharacter('-');
        QUERY.addSafeCharacter('.');
        QUERY.addSafeCharacter('_');
        QUERY.addSafeCharacter('=');
        QUERY.addSafeCharacter('&');
    }

    //Array containing the safe characters set.
    private final BitSet safeCharacters;

    private boolean encodeSpaceAsPlus = false;


    public URLEncoder() {
        this(new BitSet(256));

        for (char i = 'a'; i <= 'z'; i++) {
            addSafeCharacter(i);
        }
        for (char i = 'A'; i <= 'Z'; i++) {
            addSafeCharacter(i);
        }
        for (char i = '0'; i <= '9'; i++) {
            addSafeCharacter(i);
        }
    }


    private URLEncoder(BitSet safeCharacters) {
        this.safeCharacters = safeCharacters;
    }


    public void addSafeCharacter(char c) {
        safeCharacters.set(c);
    }


    public void removeSafeCharacter(char c) {
        safeCharacters.clear(c);
    }


    public void setEncodeSpaceAsPlus(boolean encodeSpaceAsPlus) {
        this.encodeSpaceAsPlus = encodeSpaceAsPlus;
    }


    
URL encodes the provided path using the given character set.
Params:
path –      The path to encode
charset –   The character set to use to convert the path to bytes
Returns:
The encoded path/**
     * URL encodes the provided path using the given character set.
     *
     * @param path      The path to encode
     * @param charset   The character set to use to convert the path to bytes
     *
     * @return The encoded path
     */
    public String encode(String path, Charset charset) {

        int maxBytesPerChar = 10;
        StringBuilder rewrittenPath = new StringBuilder(path.length());
        ByteArrayOutputStream buf = new ByteArrayOutputStream(maxBytesPerChar);
        OutputStreamWriter writer = new OutputStreamWriter(buf, charset);

        for (int i = 0; i < path.length(); i++) {
            int c = path.charAt(i);
            if (safeCharacters.get(c)) {
                rewrittenPath.append((char)c);
            } else if (encodeSpaceAsPlus && c == ' ') {
                rewrittenPath.append('+');
            } else {
                // convert to external encoding before hex conversion
                try {
                    writer.write((char)c);
                    writer.flush();
                } catch(IOException e) {
                    buf.reset();
                    continue;
                }
                byte[] ba = buf.toByteArray();
                for (byte toEncode : ba) {
                    // Converting each byte in the buffer
                    rewrittenPath.append('%');
                    int low = toEncode & 0x0f;
                    int high = (toEncode & 0xf0) >> 4;
                    rewrittenPath.append(hexadecimal[high]);
                    rewrittenPath.append(hexadecimal[low]);
                }
                buf.reset();
            }
        }
        return rewrittenPath.toString();
    }


    @Override
    public Object clone() {
        URLEncoder result = new URLEncoder((BitSet) safeCharacters.clone());
        result.setEncodeSpaceAsPlus(encodeSpaceAsPlus);
        return result;
    }
}