/*
 * 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.ahc.codec;

import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;

import org.apache.ahc.util.DateUtil;
import org.apache.ahc.util.NameValuePair;
import org.apache.asyncweb.common.Cookie;
import org.apache.asyncweb.common.DefaultCookie;
import org.apache.asyncweb.common.MutableCookie;
import org.apache.mina.core.buffer.IoBuffer;

/**
 * Utility class for helping to decode the HTTP Protocol.
 */
public class HttpDecoder {

    /** The Constant CHUNKED. */
    public static final String CHUNKED = "chunked";

    /** The Constant CONNECTION. */
    public static final String CONNECTION = "Connection";
    
    /** The Constant CLOSE as a value for the Connection header */
    public static final String CLOSE = "close";

    /** The Constant COOKIE_COMMENT. */
    public static final String COOKIE_COMMENT = "comment";
    
    /** The Constant COOKIE_DOMAIN. */
    public static final String COOKIE_DOMAIN = "domain";
    
    /** The Constant COOKIE_EXPIRES. */
    public static final String COOKIE_EXPIRES = "expires";
    
    /** The Constant COOKIE_MAX_AGE. */
    public static final String COOKIE_MAX_AGE = "max-age";
    
    /** The Constant COOKIE_PATH. */
    public static final String COOKIE_PATH = "path";
    
    /** The Constant COOKIE_SECURE. */
    public static final String COOKIE_SECURE = "secure";

    /** The Constant COOKIE_HTTP_ONLY. */
    public static final String COOKIE_HTTP_ONLY = "HTTPOnly";
    
    /** The Constant COOKIE_VERSION. */
    public static final String COOKIE_VERSION = "version";

    /** The Constant LOCATION. */
    public static final String LOCATION = "Location";
    
    /** The Constant SET_COOKIE. */
    public static final String SET_COOKIE = "Set-Cookie";

    /** The Constant WWW_AUTH. */
    public static final String WWW_AUTH = "WWW-Authenticate";

    /** The Constant TRANSFER_ENCODING. */
    public static final String TRANSFER_ENCODING = "Transfer-Encoding";

    /** Carriage return character. */
    private static final byte CR = 13;

    /** Line feed character. */
    private static final byte LF = 10;


    /** The decoder. */
    private CharsetDecoder decoder = Charset.forName(HttpMessage.HTTP_ELEMENT_CHARSET).newDecoder();

    /**
     * Finds a line from a ByteBuffer that ends with a CR/LF and returns the line as a String.
     * 
     * @param in ByteBuffer containing data
     * 
     * @return a <code>String</code> representing the decoded line
     * 
     * @throws Exception for any Exception that is encountered
     */
    public String decodeLine(IoBuffer in) throws Exception {
        int beginPos = in.position();
        int limit = in.limit();
        boolean lastIsCR = false;
        int terminatorPos = -1;

        for (int i = beginPos; i < limit; i++) {
            byte b = in.get(i);
            if (b == CR) {
                lastIsCR = true;
            } else {
                if (b == LF && lastIsCR) {
                    terminatorPos = i;
                    break;
                }
                lastIsCR = false;
            }
        }

        //Check if we don't have enough data to process or found a full readable line
        if (terminatorPos == -1) {
            return null;
        }

        String result = null;
        if (terminatorPos > 1) {
            IoBuffer line = in.slice();
            line.limit(terminatorPos - beginPos - 1);
            result = line.getString(decoder);
        }

        in.position(terminatorPos + 1);

        return result;
    }

    /**
     * Decodes the status code and message from a HTTP response and places the values in a
     * {@link HttpResponseMessage} object.
     * 
     * @param line <code>String</code> containing <code>HTTP/1.<i>X</i> <i>Message</i></code>
     * @param msg the <code>HttpResponseMessage</code> for which to place the result
     * 
     * @throws Exception on any Exception that may occur
     * 
     * @see HttpResponseMessage
     */
    public void decodeStatus(String line, HttpResponseMessage msg) throws Exception {
        String magic = line.substring(0, 8);
        if (!magic.equals("HTTP/1.1") && !magic.equals("HTTP/1.0")) {
            throw new IOException("Invalid HTTP response");
        }

        String status = line.substring(9, 12);
        msg.setStatusCode(Integer.parseInt(status));
        msg.setStatusMessage(line.substring(13));
    }

    /**
     * Decodes headers and footers (for HTTP/1.1) and stuffs them into a {@link HttpResponseMessage} response.
     * 
     * @param line the <code>String</code> line containing the header or footer
     * @param msg the {@link HttpResponseMessage} response message
     * 
     * @throws Exception if any exception occurs
     */
    public void decodeHeader(String line, HttpResponseMessage msg) throws Exception {
        int pos = line.indexOf(": ");
        String name = line.substring(0, pos);
        String value = line.substring(pos + 2);
        NameValuePair nvp = new NameValuePair(name, value);
        msg.addHeader(nvp);

        if (name.equalsIgnoreCase(SET_COOKIE)) {
            Cookie cookie = decodeCookie(value);
            if (cookie != null) {
                msg.addCookie(cookie);
            }
        }

        if (name.equalsIgnoreCase(HttpMessage.CONTENT_TYPE)) {
            msg.setContentType(value);
        }

        if (name.equalsIgnoreCase(HttpMessage.CONTENT_LENGTH)) {
            msg.setContentLength(Integer.parseInt(value));
        }

        if (name.equalsIgnoreCase(CONNECTION)) {
            msg.setConnection(value);
        }

        if (name.equalsIgnoreCase(LOCATION)) {
            msg.setLocation(value);
        }

        if (name.equalsIgnoreCase(TRANSFER_ENCODING) && value != null && value.equalsIgnoreCase(CHUNKED)) {
            msg.setChunked(true);
        }

        if (name.equalsIgnoreCase(WWW_AUTH)) {
            msg.addChallenge(nvp);
        }

    }

    /**
     * Decodes size records for chunked HTTP transcoding.
     * 
     * @param line the line containing the size
     * 
     * @return the <code>int</code> representing the size
     * 
     * @throws Exception if any exception occurs
     */
    public int decodeSize(String line) throws Exception {
        String strippedLine = line.trim().toLowerCase();
        for (int i = 0; i < strippedLine.length(); i++) {
            char ch = strippedLine.charAt(i);
            //Once we hit a non-numeric character, parse the number we have
            if (ch < '0' || (ch > '9' && ch < 'a') || ch > 'f') {
                return Integer.parseInt(strippedLine.substring(0, i), 16);
            }
        }

        //We got here, so the entire line passes
        return Integer.parseInt(strippedLine, 16);
    }

    /**
     * Decodes content from non-chunked transcoding.
     * 
     * @param in the <code>ByteBuffer</code> containing the content at the the current position
     * @param msg the <code>HttpResponseMessage</code> message to place the decoded content
     * 
     * @throws Exception if any exception occurs
     */
    public void decodeContent(IoBuffer in, HttpResponseMessage msg) throws Exception {
        byte content[] = new byte[msg.getContentLength()];
        in.get(content);
        msg.addContent(content);
    }

    /**
     * Decodes content from chunked transcoding.
     * 
     * @param in the <code>ByteBuffer</code> containing the content at the the current position
     * @param msg the <code>HttpResponseMessage</code> message to place the decoded content
     * 
     * @throws Exception if any exception occurs
     */
    public void decodeChunkedContent(IoBuffer in, HttpResponseMessage msg) throws Exception {
        int toRead = msg.getExpectedToRead();
        if ((in.get(in.position() + toRead) != CR) && (in.get(in.position() + toRead + 1) != LF)) {
            throw new IOException("Invalid HTTP response - chunk does not end with CRLF");

        }
        byte content[] = new byte[toRead];
        in.get(content);
        msg.addContent(content);

        //Pop the CRLF
        in.get();
        in.get();
    }

    /**
     * Decodes a cookie header and returns the decoded cookie.
     * 
     * @param cookieStr the cookie <code>String</code> header line
     * 
     * @return the decoded <code>Cookie</cookie>
     * 
     * @throws Exception if any exception occurs
     * @see Cookie
     */
    public Cookie decodeCookie(String cookieStr) throws Exception {

        MutableCookie cookie = null;

        String pairs[] = cookieStr.split(";");
        for (int i = 0; i < pairs.length; i++) {
            String nameValue[] = pairs[i].trim().split("=");
            String name = nameValue[0].trim();

            //First one is the cookie name/value pair
            if (i == 0) {
                cookie = new DefaultCookie(name, nameValue[1].trim());
                continue;
            }

            if (name.equalsIgnoreCase(COOKIE_COMMENT)) {
                cookie.setComment(nameValue[1].trim());
                continue;
            }

            if (name.equalsIgnoreCase(COOKIE_PATH)) {
                cookie.setPath(nameValue[1].trim());
            }

            if (name.equalsIgnoreCase(COOKIE_SECURE)) {
                cookie.setSecure(true);
            }

            if (name.equalsIgnoreCase(COOKIE_HTTP_ONLY)) {
                cookie.setHttpOnly(true);
            }

            if (name.equalsIgnoreCase(COOKIE_VERSION)) {
                cookie.setVersion(Integer.parseInt(nameValue[1]));
            }

            if (name.equalsIgnoreCase(COOKIE_MAX_AGE)) {
                int age = Integer.parseInt(nameValue[1]);
                cookie.setMaxAge(age);
            }

            if (name.equalsIgnoreCase(COOKIE_EXPIRES)) {
            	long createdDate = System.currentTimeMillis();
            	int age = (int)(DateUtil.parseDate(nameValue[1]).getTime() - createdDate) / 1000;
            	cookie.setCreatedDate(createdDate);
                cookie.setMaxAge(age);
            }

            if (name.equalsIgnoreCase(COOKIE_DOMAIN)) {
                cookie.setDomain(nameValue[1]);
            }
        }

        return cookie;
    }
}