/*
 * 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.wicket.util.upload;

import java.util.HashMap;
import java.util.Map;

/**
 * A simple parser intended to parse sequences of name/value pairs. Parameter values are exptected
 * to be enclosed in quotes if they contain unsafe characters, such as '=' characters or separators.
 * Parameter values are optional and can be omitted.
 * 
 * <p>
 * <code>param1 = value; param2 = "anything goes; really"; param3</code>
 * </p>
 * 
 * @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
 */

public class ParameterParser
{
	/**
	 * String to be parsed.
	 */
	private char[] chars = null;

	/**
	 * Current position in the string.
	 */
	private int pos = 0;

	/**
	 * Maximum position in the string.
	 */
	private int len = 0;

	/**
	 * Start of a token.
	 */
	private int i1 = 0;

	/**
	 * End of a token.
	 */
	private int i2 = 0;

	/**
	 * Whether names stored in the map should be converted to lower case.
	 */
	private boolean lowerCaseNames = false;

	/**
	 * Default ParameterParser constructor.
	 */
	public ParameterParser()
	{
		super();
	}

	/**
	 * Are there any characters left to parse?
	 * 
	 * @return <tt>true</tt> if there are unparsed characters, <tt>false</tt> otherwise.
	 */
	private boolean hasChar()
	{
		return pos < len;
	}

	/**
	 * A helper method to process the parsed token. This method removes leading and trailing blanks
	 * as well as enclosing quotation marks, when necessary.
	 * 
	 * @param quoted
	 *            <tt>true</tt> if quotation marks are expected, <tt>false</tt> otherwise.
	 * @return the token
	 */
	private String getToken(final boolean quoted)
	{
		// Trim leading white spaces
		while ((i1 < i2) && (Character.isWhitespace(chars[i1])))
		{
			i1++;
		}
		// Trim trailing white spaces
		while ((i2 > i1) && (Character.isWhitespace(chars[i2 - 1])))
		{
			i2--;
		}
		// Strip away quotation marks if necessary
		if (quoted)
		{
			if (((i2 - i1) >= 2) && (chars[i1] == '"') && (chars[i2 - 1] == '"'))
			{
				i1++;
				i2--;
			}
		}
		String result = null;
		if (i2 > i1)
		{
			result = new String(chars, i1, i2 - i1);
		}
		return result;
	}

	/**
	 * Tests if the given character is present in the array of characters.
	 * 
	 * @param ch
	 *            the character to test for presense in the array of characters
	 * @param charray
	 *            the array of characters to test against
	 * 
	 * @return <tt>true</tt> if the character is present in the array of characters, <tt>false</tt>
	 *         otherwise.
	 */
	private boolean isOneOf(final char ch, final char[] charray)
	{
		for (char c : charray)
		{
			if (ch == c)
			{
				return true;
			}
		}
		return false;
	}

	/**
	 * Parses out a token until any of the given terminators is encountered.
	 * 
	 * @param terminators
	 *            the array of terminating characters. Any of these characters when encountered
	 *            signify the end of the token
	 * 
	 * @return the token
	 */
	private String parseToken(final char[] terminators)
	{
		char ch;
		i1 = pos;
		i2 = pos;
		while (hasChar())
		{
			ch = chars[pos];
			if (isOneOf(ch, terminators))
			{
				break;
			}
			i2++;
			pos++;
		}
		return getToken(false);
	}

	/**
	 * Parses out a token until any of the given terminators is encountered outside the quotation
	 * marks.
	 * 
	 * @param terminators
	 *            the array of terminating characters. Any of these characters when encountered
	 *            outside the quotation marks signify the end of the token
	 * 
	 * @return the token
	 */
	private String parseQuotedToken(final char[] terminators)
	{
		char ch;
		i1 = pos;
		i2 = pos;
		boolean quoted = false;
		boolean charEscaped = false;
		while (hasChar())
		{
			ch = chars[pos];
			if (!quoted && isOneOf(ch, terminators))
			{
				break;
			}
			if (!charEscaped && (ch == '"'))
			{
				quoted = !quoted;
			}
			charEscaped = (!charEscaped && (ch == '\\'));
			i2++;
			pos++;

		}
		return getToken(true);
	}

	/**
	 * Returns <tt>true</tt> if parameter names are to be converted to lower case when name/value
	 * pairs are parsed.
	 * 
	 * @return <tt>true</tt> if parameter names are to be converted to lower case when name/value
	 *         pairs are parsed. Otherwise returns <tt>false</tt>
	 */
	public boolean isLowerCaseNames()
	{
		return lowerCaseNames;
	}

	/**
	 * Sets the flag if parameter names are to be converted to lower case when name/value pairs are
	 * parsed.
	 * 
	 * @param b
	 *            <tt>true</tt> if parameter names are to be converted to lower case when name/value
	 *            pairs are parsed. <tt>false</tt> otherwise.
	 */
	public void setLowerCaseNames(final boolean b)
	{
		lowerCaseNames = b;
	}

	/**
	 * Extracts a map of name/value pairs from the given string. Names are expected to be unique.
	 * Multiple separators may be specified and the earliest found in the input string is used.
	 * 
	 * @param str
	 *            the string that contains a sequence of name/value pairs
	 * @param separators
	 *            the name/value pairs separators
	 * 
	 * @return a map of name/value pairs
	 */
	public Map<String, String> parse(final String str, final char[] separators)
	{
		if ((separators == null) || (separators.length == 0))
		{
			return new HashMap<String, String>();
		}
		char separator = separators[0];
		if (str != null)
		{
			int idx = str.length();
			for (char sep : separators)
			{
				int tmp = str.indexOf(sep);
				if (tmp != -1)
				{
					if (tmp < idx)
					{
						idx = tmp;
						separator = sep;
					}
				}
			}
		}
		return parse(str, separator);
	}

	/**
	 * Extracts a map of name/value pairs from the given string. Names are expected to be unique.
	 * 
	 * @param str
	 *            the string that contains a sequence of name/value pairs
	 * @param separator
	 *            the name/value pairs separator
	 * 
	 * @return a map of name/value pairs
	 */
	public Map<String, String> parse(final String str, final char separator)
	{
		if (str == null)
		{
			return new HashMap<String, String>();
		}
		return parse(str.toCharArray(), separator);
	}

	/**
	 * Extracts a map of name/value pairs from the given array of characters. Names are expected to
	 * be unique.
	 * 
	 * @param chars
	 *            the array of characters that contains a sequence of name/value pairs
	 * @param separator
	 *            the name/value pairs separator
	 * 
	 * @return a map of name/value pairs
	 */
	public Map<String, String> parse(final char[] chars, final char separator)
	{
		if (chars == null)
		{
			return new HashMap<String, String>();
		}
		return parse(chars, 0, chars.length, separator);
	}

	/**
	 * Extracts a map of name/value pairs from the given array of characters. Names are expected to
	 * be unique.
	 * 
	 * @param chars
	 *            the array of characters that contains a sequence of name/value pairs
	 * @param offset
	 *            - the initial offset.
	 * @param length
	 *            - the length.
	 * @param separator
	 *            the name/value pairs separator
	 * 
	 * @return a map of name/value pairs
	 */
	public Map<String, String> parse(final char[] chars, final int offset, final int length,
		final char separator)
	{

		if (chars == null)
		{
			return new HashMap<String, String>();
		}
		Map<String, String> params = new HashMap<String, String>();
		this.chars = chars;
		pos = offset;
		len = length;

		String paramName = null;
		String paramValue = null;
		while (hasChar())
		{
			paramName = parseToken(new char[] { '=', separator });
			paramValue = null;
			if (hasChar() && (chars[pos] == '='))
			{
				pos++; // skip '='
				paramValue = parseQuotedToken(new char[] { separator });
			}
			if (hasChar() && (chars[pos] == separator))
			{
				pos++; // skip separator
			}
			if ((paramName != null) && (paramName.length() > 0))
			{
				if (lowerCaseNames)
				{
					paramName = paramName.toLowerCase();
				}
				params.put(paramName, paramValue);
			}
		}
		return params;
	}
}
