/*
 * Copyright 2006 the original author or authors.
 * 
 * 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.wamblee.crawler.kiss.scheduling;

import java.io.Serializable;
import java.util.Calendar;
import java.util.Date;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.wamblee.crawler.kiss.main.Report;

/**
 * This class encapsulates the logic for deciding whether to
 * run the crawler. This provides the mechanism to keep the 
 * scheduler simple (e.g. scheduling every hour) and providing
 * more complex logic for determining whether to run the 
 * crawler. 
 */
public class CrawlerStatus implements Serializable {
    
    private static final Log LOG = LogFactory.getLog(CrawlerStatus.class);
    
    private CrawlerExecutor _crawler; 
    private Date _lastExecuted;
    private boolean _lastResult;
    private Exception _lastException;
    private Report _lastReport; 
    private int _hourMin; 
    private int _hourMax;
    private boolean _mustExecute; 
    
    /**
     * Constructs the scheduler.
     * The crawler will run if it is triggered in the range between the minimum (included)
     * and maximum (included) hour of the day if either
     * <ul>
     *   <li>it is triggered for the first time on the current day.</li>
     *   <li>an earlier crawling attempt on the same day failed. </li>
     * </ul>
     * @param aCrawler The interface through which the crawler is executed.
     * @param aHourMin The crawler may only run if hour &gt;= <code>aHourMin</code>
     * @param aHourMax The crawler may only run if hour &lt;= <code>aHourMax</code>
     */
    public CrawlerStatus(CrawlerExecutor aCrawler, int aHourMin, int aHourMax) { 
        _crawler = aCrawler; 
        _lastExecuted = new Date(); 
        _lastResult = true; // the crawler will automatically run the next day. 
        _lastException = null;
        _lastReport = null; 
        _hourMin = aHourMin;
        _hourMax = aHourMax;
        _mustExecute = false; 
    }
    
    /**
     * Determines whether or not the crawler must be run the next time it is triggered.
     * @param aMustExecute If true then the crawler will run the next time it is triggered
     *   by the scheduler. 
     */
    public void setMustExecute(boolean aMustExecute) { 
        _mustExecute = aMustExecute; 
    }
    
    /**
     * Called by a scheduled job. This determines whether the crawler must be run or 
     * not. This encapsulates the rukes for retrying and scheduling the crawler. 
     * @param aDate Time at which we are executing now. 
     */
    public void execute(Date aDate) { 
        
        if (mustExecute(aDate)) { 
            LOG.info("Executing crawler at " + aDate);
            Report report = new Report();
            try {
                _crawler.execute(aDate, report);
                _lastResult = true; 
                _lastException = null; 
            } catch (Exception e) {
                _lastResult = false; 
                _lastException = e; 
            } finally { 
                _lastExecuted = aDate;
                _lastReport = report;
            }
        } 
    }
    
    /**
     * Gets the time the crawler was last executed.
     * @return Time of last execution. 
     */
    public Date getLastExecuted() { 
        return _lastExecuted; 
    }
    
    /**
     * Gets the result of the last execution. 
     * @return True iff last execution was a success. 
     */
    public boolean getLastResult() { 
        return _lastResult; 
    }
    
    /**
     * Gets the exception thrown by the last execution. 
     * @return null if the last execution was successful or an exception 
     *   otherwise.
     */
    public Exception getLastException() { 
        return _lastException; 
    }
    
    /**
     * Gets the last report from the scheduler. 
     * @return Report. 
     */
    public Report getLastReport() { 
        return _lastReport; 
    }
    
    /**
     * Determines whether or not the crawler must be run. 
     * @param aDate Current time. 
     * @return True iff the crawler must be run. 
     */
    private boolean mustExecute(Date aDate) {
        if (_mustExecute) { 
            _mustExecute = false;
            return true; 
        }
        if ( _lastExecuted == null ) {
            return false; // crawler must be started manually at least once after deployment.
        }
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(aDate);
        int hour = calendar.get(Calendar.HOUR_OF_DAY);
        if ( hour < _hourMin ) {
            return false; 
        }
        if (hour > _hourMax ) { 
            return false; 
        }
     
        if ( !lastExecutionWasOnSameDay(aDate)) { 
            return true; // First execution of today. 
        } 
        // last execution was on the same day.
        if ( !_lastResult ) { 
            return true; // last execution of today was unsuccessful, retry. 
        }
        return false; // already run successfully today.
    }
    
    /**
     * Determines if the last execution was on the same day. 
     * @param aDate Current time. 
     * @return True iff last execution was on the same day. 
     */
    private boolean lastExecutionWasOnSameDay(Date aDate) {
        if ( _lastExecuted == null ) { 
            return false;
        }
        int curDay = getDayOfYear(aDate);
        int lastDay = getDayOfYear(_lastExecuted);
        return curDay == lastDay; // check can be invalid only if scheduling interval is one year,
                                  // which is ridiculous.
    }

    /**
     * Gets the day of the year
     * @param aDate Date to compute day for. 
     */
    private int getDayOfYear(Date aDate) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(aDate);
        return calendar.get(Calendar.DAY_OF_YEAR);
    }
}