/*
 * Copyright 2015 The Netty Project
 *
 * The Netty Project 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 io.netty.handler.codec.http.cookie;

import static io.netty.util.internal.ObjectUtil.checkNotNull;

import java.util.Collections;
import java.util.Set;
import java.util.TreeSet;

A RFC6265 compliant cookie decoder to be used server side.
Only name and value fields are expected, so old fields are not populated (path, domain, etc).
Old RFC2965 cookies are still supported,
old fields will simply be ignored.
See Also:
ServerCookieEncoder/**
 * A <a href="http://tools.ietf.org/html/rfc6265">RFC6265</a> compliant cookie decoder to be used server side.
 *
 * Only name and value fields are expected, so old fields are not populated (path, domain, etc).
 *
 * Old <a href="http://tools.ietf.org/html/rfc2965">RFC2965</a> cookies are still supported,
 * old fields will simply be ignored.
 *
 * @see ServerCookieEncoder
 */
public final class ServerCookieDecoder extends CookieDecoder {

    private static final String RFC2965_VERSION = "$Version";

    private static final String RFC2965_PATH = "$" + CookieHeaderNames.PATH;

    private static final String RFC2965_DOMAIN = "$" + CookieHeaderNames.DOMAIN;

    private static final String RFC2965_PORT = "$Port";

    
Strict encoder that validates that name and value chars are in the valid scope
defined in RFC6265
/**
     * Strict encoder that validates that name and value chars are in the valid scope
     * defined in RFC6265
     */
    public static final ServerCookieDecoder STRICT = new ServerCookieDecoder(true);

    
Lax instance that doesn't validate name and value
/**
     * Lax instance that doesn't validate name and value
     */
    public static final ServerCookieDecoder LAX = new ServerCookieDecoder(false);

    private ServerCookieDecoder(boolean strict) {
        super(strict);
    }

    
Decodes the specified Set-Cookie HTTP header value into a Cookie. 
Returns:
the decoded Cookie/**
     * Decodes the specified Set-Cookie HTTP header value into a {@link Cookie}.
     *
     * @return the decoded {@link Cookie}
     */
    public Set<Cookie> decode(String header) {
        final int headerLen = checkNotNull(header, "header").length();

        if (headerLen == 0) {
            return Collections.emptySet();
        }

        Set<Cookie> cookies = new TreeSet<Cookie>();

        int i = 0;

        boolean rfc2965Style = false;
        if (header.regionMatches(true, 0, RFC2965_VERSION, 0, RFC2965_VERSION.length())) {
            // RFC 2965 style cookie, move to after version value
            i = header.indexOf(';') + 1;
            rfc2965Style = true;
        }

        loop: for (;;) {

            // Skip spaces and separators.
            for (;;) {
                if (i == headerLen) {
                    break loop;
                }
                char c = header.charAt(i);
                if (c == '\t' || c == '\n' || c == 0x0b || c == '\f'
                        || c == '\r' || c == ' ' || c == ',' || c == ';') {
                    i++;
                    continue;
                }
                break;
            }

            int nameBegin = i;
            int nameEnd;
            int valueBegin;
            int valueEnd;

            for (;;) {

                char curChar = header.charAt(i);
                if (curChar == ';') {
                    // NAME; (no value till ';')
                    nameEnd = i;
                    valueBegin = valueEnd = -1;
                    break;

                } else if (curChar == '=') {
                    // NAME=VALUE
                    nameEnd = i;
                    i++;
                    if (i == headerLen) {
                        // NAME= (empty value, i.e. nothing after '=')
                        valueBegin = valueEnd = 0;
                        break;
                    }

                    valueBegin = i;
                    // NAME=VALUE;
                    int semiPos = header.indexOf(';', i);
                    valueEnd = i = semiPos > 0 ? semiPos : headerLen;
                    break;
                } else {
                    i++;
                }

                if (i == headerLen) {
                    // NAME (no value till the end of string)
                    nameEnd = headerLen;
                    valueBegin = valueEnd = -1;
                    break;
                }
            }

            if (rfc2965Style && (header.regionMatches(nameBegin, RFC2965_PATH, 0, RFC2965_PATH.length()) ||
                    header.regionMatches(nameBegin, RFC2965_DOMAIN, 0, RFC2965_DOMAIN.length()) ||
                    header.regionMatches(nameBegin, RFC2965_PORT, 0, RFC2965_PORT.length()))) {

                // skip obsolete RFC2965 fields
                continue;
            }

            DefaultCookie cookie = initCookie(header, nameBegin, nameEnd, valueBegin, valueEnd);
            if (cookie != null) {
                cookies.add(cookie);
            }
        }

        return cookies;
    }
}