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/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package com.sun.xml.rpc.client.http;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/**
 * A parser for date strings commonly found in http and email headers that
 * follow various RFC conventions.  Given a date-string, the parser will
 * attempt to parse it by trying matches with a set of patterns, returning
 * null on failure, a Date object on success.
 *
 * @author JAX-RPC Development Team
 */
public class RfcDateParser {

    private static final String debugProp = "hotjava.debug.RfcDateParser";
    private boolean isGMT = false;
    static final String[] standardFormats =
        { "EEEE', 'dd-MMM-yy HH:mm:ss z", // RFC 850 (obsoleted by 1036)
        "EEEE', 'dd-MMM-yy HH:mm:ss", // ditto but no tz. Happens too often
        "EEE', 'dd-MMM-yyyy HH:mm:ss z", // RFC 822/1123
        "EEE', 'dd MMM yyyy HH:mm:ss z", // REMIND what rfc? Apache/1.1
        "EEEE', 'dd MMM yyyy HH:mm:ss z", // REMIND what rfc? Apache/1.1
        "EEE', 'dd MMM yyyy hh:mm:ss z", // REMIND what rfc? Apache/1.1
        "EEEE', 'dd MMM yyyy hh:mm:ss z", // REMIND what rfc? Apache/1.1
        "EEE MMM dd HH:mm:ss z yyyy", // Date's string output format
        "EEE MMM dd HH:mm:ss yyyy", // ANSI C asctime format()
        "EEE', 'dd-MMM-yy HH:mm:ss", // No time zone 2 digit year RFC 1123
        "EEE', 'dd-MMM-yyyy HH:mm:ss" // No time zone RFC 822/1123
    };
    static final String[] gmtStandardFormats =
        { "EEEE',' dd-MMM-yy HH:mm:ss 'GMT'", // RFC 850 (obsoleted by 1036)
        "EEE',' dd-MMM-yyyy HH:mm:ss 'GMT'", // RFC 822/1123
        "EEE',' dd MMM yyyy HH:mm:ss 'GMT'", // REMIND what rfc? Apache/1.1
        "EEEE',' dd MMM yyyy HH:mm:ss 'GMT'", // REMIND what rfc? Apache/1.1
        "EEE',' dd MMM yyyy hh:mm:ss 'GMT'", // REMIND what rfc? Apache/1.1
        "EEEE',' dd MMM yyyy hh:mm:ss 'GMT'", // REMIND what rfc? Apache/1.1
        "EEE MMM dd HH:mm:ss 'GMT' yyyy" // Date's string output format
    };
    String dateString;

    public RfcDateParser(String dateString) {

        this.dateString = dateString.trim();

        if (this.dateString.indexOf("GMT") != -1) {
            isGMT = true;
        }
    }

    public Date getDate() {

        // format is wdy, DD-Mon-yyyy HH:mm:ss GMT
        int arrayLen =
            isGMT ? gmtStandardFormats.length : standardFormats.length;

        for (int i = 0; i < arrayLen; i++) {
            Date d;

            if (isGMT) {
                d = tryParsing(gmtStandardFormats[i]);
            } else {
                d = tryParsing(standardFormats[i]);
            }

            if (d != null) {
                return d;
            }
        }

        return null;
    }

    private Date tryParsing(String format) {

        SimpleDateFormat df = new SimpleDateFormat(format, Locale.US);

        if (isGMT) {
            df.setTimeZone(TimeZone.getTimeZone("GMT"));
        }

        try {
            return df.parse(dateString);
        } catch (Exception e) {
            return null;
        }
    }
}