/*
 * 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 io.netty.handler.codec.DateFormatter;

import java.util.Date;

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

A RFC6265 compliant cookie decoder to be used client side. It will store the way the raw value was wrapped in Cookie.setWrap(boolean) so it can be eventually sent back to the Origin server as is. 
See Also:
ClientCookieEncoder/**
 * A <a href="http://tools.ietf.org/html/rfc6265">RFC6265</a> compliant cookie decoder to be used client side.
 *
 * It will store the way the raw value was wrapped in {@link Cookie#setWrap(boolean)} so it can be
 * eventually sent back to the Origin server as is.
 *
 * @see ClientCookieEncoder
 */
public final class ClientCookieDecoder extends CookieDecoder {

    
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 ClientCookieDecoder STRICT = new ClientCookieDecoder(true);

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

    private ClientCookieDecoder(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 Cookie decode(String header) {
        final int headerLen = checkNotNull(header, "header").length();

        if (headerLen == 0) {
            return null;
        }

        CookieBuilder cookieBuilder = null;

        loop: for (int i = 0;;) {

            // Skip spaces and separators.
            for (;;) {
                if (i == headerLen) {
                    break loop;
                }
                char c = header.charAt(i);
                if (c == ',') {
                    // Having multiple cookies in a single Set-Cookie header is
                    // deprecated, modern browsers only parse the first one
                    break loop;

                } else if (c == '\t' || c == '\n' || c == 0x0b || c == '\f'
                        || c == '\r' || 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 (valueEnd > 0 && header.charAt(valueEnd - 1) == ',') {
                // old multiple cookies separator, skipping it
                valueEnd--;
            }

            if (cookieBuilder == null) {
                // cookie name-value pair
                DefaultCookie cookie = initCookie(header, nameBegin, nameEnd, valueBegin, valueEnd);

                if (cookie == null) {
                    return null;
                }

                cookieBuilder = new CookieBuilder(cookie, header);
            } else {
                // cookie attribute
                cookieBuilder.appendAttribute(nameBegin, nameEnd, valueBegin, valueEnd);
            }
        }
        return cookieBuilder != null ? cookieBuilder.cookie() : null;
    }

    private static class CookieBuilder {

        private final String header;
        private final DefaultCookie cookie;
        private String domain;
        private String path;
        private long maxAge = Long.MIN_VALUE;
        private int expiresStart;
        private int expiresEnd;
        private boolean secure;
        private boolean httpOnly;

        CookieBuilder(DefaultCookie cookie, String header) {
            this.cookie = cookie;
            this.header = header;
        }

        private long mergeMaxAgeAndExpires() {
            // max age has precedence over expires
            if (maxAge != Long.MIN_VALUE) {
                return maxAge;
            } else if (isValueDefined(expiresStart, expiresEnd)) {
                Date expiresDate = DateFormatter.parseHttpDate(header, expiresStart, expiresEnd);
                if (expiresDate != null) {
                    long maxAgeMillis = expiresDate.getTime() - System.currentTimeMillis();
                    return maxAgeMillis / 1000 + (maxAgeMillis % 1000 != 0 ? 1 : 0);
                }
            }
            return Long.MIN_VALUE;
        }

        Cookie cookie() {
            cookie.setDomain(domain);
            cookie.setPath(path);
            cookie.setMaxAge(mergeMaxAgeAndExpires());
            cookie.setSecure(secure);
            cookie.setHttpOnly(httpOnly);
            return cookie;
        }

        
Parse and store a key-value pair. First one is considered to be the
cookie name/value. Unknown attribute names are silently discarded.
Params:
keyStart – 
           where the key starts in the header
keyEnd – 
           where the key ends in the header
valueStart – 
           where the value starts in the header
valueEnd – 
           where the value ends in the header/**
         * Parse and store a key-value pair. First one is considered to be the
         * cookie name/value. Unknown attribute names are silently discarded.
         *
         * @param keyStart
         *            where the key starts in the header
         * @param keyEnd
         *            where the key ends in the header
         * @param valueStart
         *            where the value starts in the header
         * @param valueEnd
         *            where the value ends in the header
         */
        void appendAttribute(int keyStart, int keyEnd, int valueStart, int valueEnd) {
            int length = keyEnd - keyStart;

            if (length == 4) {
                parse4(keyStart, valueStart, valueEnd);
            } else if (length == 6) {
                parse6(keyStart, valueStart, valueEnd);
            } else if (length == 7) {
                parse7(keyStart, valueStart, valueEnd);
            } else if (length == 8) {
                parse8(keyStart);
            }
        }

        private void parse4(int nameStart, int valueStart, int valueEnd) {
            if (header.regionMatches(true, nameStart, CookieHeaderNames.PATH, 0, 4)) {
                path = computeValue(valueStart, valueEnd);
            }
        }

        private void parse6(int nameStart, int valueStart, int valueEnd) {
            if (header.regionMatches(true, nameStart, CookieHeaderNames.DOMAIN, 0, 5)) {
                domain = computeValue(valueStart, valueEnd);
            } else if (header.regionMatches(true, nameStart, CookieHeaderNames.SECURE, 0, 5)) {
                secure = true;
            }
        }

        private void setMaxAge(String value) {
            try {
                maxAge = Math.max(Long.parseLong(value), 0L);
            } catch (NumberFormatException e1) {
                // ignore failure to parse -> treat as session cookie
            }
        }

        private void parse7(int nameStart, int valueStart, int valueEnd) {
            if (header.regionMatches(true, nameStart, CookieHeaderNames.EXPIRES, 0, 7)) {
                expiresStart = valueStart;
                expiresEnd = valueEnd;
            } else if (header.regionMatches(true, nameStart, CookieHeaderNames.MAX_AGE, 0, 7)) {
                setMaxAge(computeValue(valueStart, valueEnd));
            }
        }

        private void parse8(int nameStart) {
            if (header.regionMatches(true, nameStart, CookieHeaderNames.HTTPONLY, 0, 8)) {
                httpOnly = true;
            }
        }

        private static boolean isValueDefined(int valueStart, int valueEnd) {
            return valueStart != -1 && valueStart != valueEnd;
        }

        private String computeValue(int valueStart, int valueEnd) {
            return isValueDefined(valueStart, valueEnd) ? header.substring(valueStart, valueEnd) : null;
        }
    }
}