/*
 * Copyright (C) 2004-2008 Jive Software. All rights reserved.
 *
 * Licensed 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.jivesoftware.openfire;

import org.jivesoftware.openfire.session.ClientSession;

import java.util.Comparator;
import java.util.Date;
import java.util.Objects;

/**
 * Filters and sorts lists of sessions. This allows for a very rich set of possible
 * queries that can be run on session data. Some examples are: "Show all sessions
 * started during the last hour by a certain user".
 * <p>
 * The class also supports pagination of results with the setStartIndex(int)
 * and setNumResults(int) methods. If the start index is not set, it will
 * begin at index 0 (the start of results). If the number of results is not set,
 * it will be unbounded and return as many results as available.</p>
 * <p>
 * Factory methods to create common queries are provided for convenience.</p>
 *
 * @author Matt Tucker
 */
public class SessionResultFilter {

    // ############################################################
    // Search order criteria
    // ############################################################
    /**
     * Descending sort (ie 3, 2, 1...).
     */
    public static final int DESCENDING = 0;

    /**
     * Ascending sort (ie 3, 4, 5...).
     */
    public static final int ASCENDING = 1;

    // ############################################################
    // Result limit search criteria
    // ############################################################
    /**
     * Represents no result limit (infinite results).
     */
    public static final int NO_RESULT_LIMIT = -1;

    // ############################################################
    // Sort fields
    // ############################################################
    public static final int SORT_USER = 0;
    public static final int SORT_CREATION_DATE = 1;
    public static final int SORT_LAST_ACTIVITY_DATE = 2;
    public static final int SORT_NUM_CLIENT_PACKETS = 3;
    public static final int SORT_NUM_SERVER_PACKETS = 4;

    /**
     * Creates a default SessionResultFilter: no filtering with results sorted
     * by user (ascending).
     *
     * @return default SessionResultFilter.
     */
    public static SessionResultFilter createDefaultSessionFilter() {
        SessionResultFilter resultFilter = new SessionResultFilter();
        resultFilter.setSortField(SORT_USER);
        resultFilter.setSortOrder(ASCENDING);
        return resultFilter;
    }

    private int sortField = SORT_LAST_ACTIVITY_DATE;
    private int sortOrder = DESCENDING;

    private String username = null;

    /**
     * The starting index for results. Default is 0.
     */
    private int startIndex = 0;

    /**
     * Number of results to return. Default is NO_RESULT_LIMIT
     * which means an unlimited number of results.
     */
    private int numResults = NO_RESULT_LIMIT;

    private Date creationDateRangeMin = null;
    private Date creationDateRangeMax = null;
    private Date lastActivityDateRangeMin = null;
    private Date lastActivityDateRangeMax = null;

    /**
     * Returns the currently selected sort field. The default value is
     * SessionResultFilter.SORT_LAST_ACTIVITY_DATE.
     *
     * @return current sort field.
     */
    public int getSortField() {
        return sortField;
    }

    /**
     * Sets the sort field to use. The default value is
     * SessionResultFilter.SORT_LAST_ACTIVITY_DATE.
     *
     * @param sortField the field that will be used for sorting.
     */
    public void setSortField(int sortField) {
        this.sortField = sortField;
    }

    /**
     * Returns the sort order, which will be SessionResultFilter.ASCENDING for
     * ascending sorting, or SessionResultFilter.DESCENDING for descending sorting.
     * Descending sorting is: 3, 2, 1, etc. Ascending sorting is 1, 2, 3, etc.
     *
     * @return the sort order.
     */
    public int getSortOrder() {
        return this.sortOrder;
    }

    /**
     * Sets the sort type. Valid arguments are SessionResultFilter.ASCENDING for
     * ascending sorting or SessionResultFilter.DESCENDING for descending sorting.
     * Descending sorting is: 3, 2, 1, etc. Ascending sorting is 1, 2, 3, etc.
     *
     * @param sortOrder the order that results will be sorted in.
     */
    public void setSortOrder(int sortOrder) {
        if (!(sortOrder == SessionResultFilter.ASCENDING || sortOrder == SessionResultFilter.DESCENDING)) {
            throw new IllegalArgumentException();
        }
        this.sortOrder = sortOrder;
    }

    /**
     * <p>Returns the max number of results that should be returned.</p>
     * <p>The default value for is NO_RESULT_LIMIT, which means there will be no limit
     * on the number of results. This method can be used in combination with
     * setStartIndex(int) to perform pagination of results.</p>
     *
     * @return the max number of results to return or NO_RESULT_LIMIT for no limit
     * @see #setStartIndex(int)
     */
    public int getNumResults() {
        return numResults;
    }

    /**
     * <p>Sets the limit on the number of results to be returned.</p>
     * <p>User NO_RESULT_LIMIT if you don't want to limit the results returned.</p>
     *
     * @param numResults the number of results to return or NO_RESULT_LIMIT for no limit
     */
    public void setNumResults(int numResults) {
        if (numResults != NO_RESULT_LIMIT && numResults < 0) {
            throw new IllegalArgumentException("numResults cannot be less than 0.");
        }
        this.numResults = numResults;
    }

    /**
     * Returns the index of the first result to return.
     *
     * @return the index of the first result which should be returned.
     */
    public int getStartIndex() {
        return startIndex;
    }

    /**
     * Sets the index of the first result to return. For example, if the start
     * index is set to 20, the Iterator returned will start at the 20th result
     * in the query. This method can be used in combination with
     * setNumResults(int) to perform pagination of results.
     *
     * @param startIndex the index of the first result to return.
     */
    public void setStartIndex(int startIndex) {
        if (startIndex < 0) {
            throw new IllegalArgumentException("A start index less than 0 is not valid.");
        }
        this.startIndex = startIndex;
    }

    /**
     * Returns a comparator that will sort a standard sorted set according
     * to this filter's sort order.
     *
     * @return a comparator that sorts Sessions matching the sort order for this filter.
     */
    public Comparator<ClientSession> getSortComparator() {
        return new SessionComparator();
    }

    /**
     * Compares sessions according to sort fields.
     *
     * @author Iain Shigeoka
     */
    private class SessionComparator implements Comparator<ClientSession> {

        @Override
        public int compare(ClientSession lhs, ClientSession rhs) {
            int comparison;
            switch (sortField) {
                case SessionResultFilter.SORT_CREATION_DATE:
                    comparison = lhs.getCreationDate().compareTo(rhs.getCreationDate());
                    break;
                case SessionResultFilter.SORT_LAST_ACTIVITY_DATE:
                    comparison = lhs.getLastActiveDate().compareTo(rhs.getCreationDate());
                    break;
                case SessionResultFilter.SORT_NUM_CLIENT_PACKETS:
                    comparison = (int)(lhs.getNumClientPackets() - rhs.getNumClientPackets());
                    break;
                case SessionResultFilter.SORT_NUM_SERVER_PACKETS:
                    comparison = (int)(lhs.getNumServerPackets() - rhs.getNumServerPackets());
                    break;
                case SessionResultFilter.SORT_USER:
                    // sort first by name, then by resource
                    String lUsername = lhs.isAnonymousUser() ? "" : lhs.getAddress().getNode();
                    String rUsername = rhs.isAnonymousUser() ? "" : rhs.getAddress().getNode();
                    comparison = compareString(lUsername, rUsername);
                    if (comparison == 0) {
                        comparison = compareString(lhs.getAddress().getResource(),
                                rhs.getAddress().getResource());
                    }
                    break;
                default:
                    comparison = 0;
            }
            if (sortOrder == SessionResultFilter.DESCENDING) {
                comparison *= -1; // Naturally ascending, flip sign if descending
            }
            return comparison;
        }

        private int compareString(String lhs, String rhs) {
            if (lhs == null) {
                lhs = "";
            }
            if (rhs == null) {
                rhs = "";
            }
            return lhs.compareTo(rhs);
        }
    }

    /**
     * Rounds the given date down to the nearest specified second. The following
     * table shows sample input and expected output values: (Note, only
     * the time portion of the date is shown for brevity)
     *
     * <table border="1">
     * <caption>Rounding examples</caption>
     * <tr><th>Date</th><th>Seconds</th><th>Result</th></tr>
     * <tr><td>1:37.48</td><td>5</td><td>1:37.45</td></tr>
     * <tr><td>1:37.48</td><td>10</td><td>1:37.40</td></tr>
     * <tr><td>1:37.48</td><td>30</td><td>1:37.30</td></tr>
     * <tr><td>1:37.48</td><td>60</td><td>1:37.00</td></tr>
     * <tr><td>1:37.48</td><td>120</td><td>1:36.00</td></tr>
     * </table>
     *
     * <p>This method is useful when calculating the last post in
     * a forum or the number of new messages from a given date. Using a rounded
     * date allows Jive to internally cache the results of the date query.
     * Here's an example that shows the last posted message in a forum accurate
     * to the last 60 seconds:</p>
     *
     * <pre>
     * SessionResultFilter filter = new SessionResultFilter();
     * filter.setSortOrder(SessionResultFilter.DESCENDING);
     * filter.setSortField(JiveGlobals.SORT_CREATION_DATE);
     * <b>filter.setCreationDateRangeMin(SessionResultFilter.roundDate(forum.getModificationDate(), 60));</b>
     * filter.setNumResults(1);
     * Iterator messages = forum.messages(filter);
     * ForumMessage lastPost = (ForumMessage)messages.next();
     * </pre>
     *
     * @param date the {@code Date} we want to round.
     * @param seconds the number of seconds we want to round the date to.
     * @return the given date, rounded down to the nearest specified number of seconds.
     */
    public static Date roundDate(Date date, int seconds) {
        return new Date(roundDate(date.getTime(), seconds));
    }

    /**
     * Rounds the given date down to the nearest specified second.
     *
     * @param date the date (as a long) that we want to round.
     * @param seconds the number of seconds we want to round the date to.
     * @return the given date (as a long), rounded down to the nearest
     *         specified number of seconds.
     */
    public static long roundDate(long date, int seconds) {
        return date - (date % (1000 * seconds));
    }

    @Override
    public boolean equals(Object object) {
        if (this == object) {
            return true;
        }
        if (object != null && object instanceof SessionResultFilter) {
            SessionResultFilter o = (SessionResultFilter)object;
            if (sortField != o.sortField) {
                return false;
            }
            if (sortOrder != o.sortOrder) {
                return false;
            }
            if (numResults != o.numResults) {
                return false;
            }
            if (!compare(username, o.username)) {
                return false;
            }

            if (!compare(creationDateRangeMin, o.creationDateRangeMin)) {
                return false;
            }
            if (!compare(creationDateRangeMax, o.creationDateRangeMax)) {
                return false;
            }
            if (!compare(lastActivityDateRangeMin, o.lastActivityDateRangeMin)) {
                return false;
            }
            if (!compare(lastActivityDateRangeMax, o.lastActivityDateRangeMax)) {
                return false;
            }
            // All checks passed, so equal.
            return true;
        }
        else {
            return false;
        }
    }

    @Override
    public int hashCode() {
        return Objects.hash(sortField, sortOrder, username, numResults, creationDateRangeMin, creationDateRangeMax, lastActivityDateRangeMin, lastActivityDateRangeMax);
    }

    /**
     * Returns true if two objects are equal. This is a helper method
     * to assist with the case that one or both objects are {@code null};
     * if both objects are {@code null} then they're considered equal.
     *
     * @param one the first object.
     * @param two the second object.
     * @return true if the objects are equal.
     */
    private static boolean compare (Object one, Object two) {
        if (one == null && two != null) {
            return false;
        }
        else if (one != null) {
            if (!one.equals(two)) {
                return false;
            }
        }
        return true;
    }
}
