/*
 Copyright (C) 2007 Richard Gomes

 This source code is release under the BSD License.

 This file is part of JQuantLib, a free-software/open-source library
 for financial quantitative analysts and developers - http://jquantlib.org/

 JQuantLib is free software: you can redistribute it and/or modify it
 under the terms of the JQuantLib license.  You should have received a
 copy of the license along with this program; if not, please email
 . The license is also available online at
 .

 This program is distributed in the hope that it will be useful, but WITHOUT
 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 FOR A PARTICULAR PURPOSE.  See the license for more details.

 JQuantLib is based on QuantLib. http://quantlib.org/
 When applicable, the original copyright notice follows this notice.
 */

/*
 Copyright (C) 2000, 2001, 2002, 2003 RiskMap srl
 Copyright (C) 2003, 2004, 2005, 2006, 2007 StatPro Italia srl

 This file is part of QuantLib, a free-software/open-source library
 for financial quantitative analysts and developers - http://quantlib.org/

 QuantLib is free software: you can redistribute it and/or modify it
 under the terms of the QuantLib license.  You should have received a
 copy of the license along with this program; if not, please email
 . The license is also available online at
 .

 This program is distributed in the hope that it will be useful, but WITHOUT
 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 FOR A PARTICULAR PURPOSE.  See the license for more details.
*/

package org.jquantlib.daycounters;

import org.jquantlib.QL;
import org.jquantlib.lang.annotation.QualityAssurance;
import org.jquantlib.lang.annotation.QualityAssurance.Quality;
import org.jquantlib.lang.annotation.QualityAssurance.Version;
import org.jquantlib.time.Date;


/**
 * This interface provides methods for determining the length of a time
 * period according to given market convention, both as a number
 * of days and as a year fraction.
 *
 * @see Day count convention
 *
 * @author Richard Gomes
 * @author Srinivas Hasti
 */
@QualityAssurance(quality=Quality.Q4_UNIT, version=Version.V097, reviewers="Richard Gomes")
public class DayCounter {

    private static final String NO_IMPLEMENTATION_PROVIDED = "no implementation provided";

    //
    // protected fields
    //

    protected Impl impl;


    //
    // public constructors
    //

    public DayCounter() {
        // nothing
    }


    //
    // public methods
    //

    /**
     * Returns whether or not the day counter is initialized
     */
    public boolean empty() /* @ReadOnly */ {
        return impl == null;
    }

    /**
     * @return the name of this DayCounter
     */
	public String name() /* @ReadOnly */ {
        QL.require(impl != null, NO_IMPLEMENTATION_PROVIDED);
        return impl.name();
    }


	/**
     * Returns the number of days between two dates
	 *
	 * @param dateStart is the starting Date
	 * @param dateEnd is the ending Date
	 * @return the number of days between two dates.
	 */
	public long dayCount(final Date dateStart, final Date dateEnd) /* @ReadOnly */ {
        QL.require(impl != null, NO_IMPLEMENTATION_PROVIDED);
        return impl.dayCount(dateStart, dateEnd);
	}

	   /**
     * Returns the period between two dates as a fraction of year
     *
     * @param dateStart
     * @param dateEnd
     * @return the period between two dates as a fraction of year
     */
    public /*@Time*/ double yearFraction(final Date dateStart, final Date dateEnd) /* @ReadOnly */ {
        return yearFraction(dateStart, dateEnd, null, null);
    }


	/**
	 * Returns the period between two dates as a fraction of year, considering referencing dates for both.
	 *
	 * @param dateStart
	 * @param dateEnd
	 * @param refPeriodStart
	 * @param refPeriodEnd
	 * @return the period between two dates as a fraction of year, considering referencing dates for both.
	 */
	public /*@Time*/ double yearFraction(final Date dateStart, final Date dateEnd, final Date refPeriodStart, final Date refPeriodEnd) /* @ReadOnly */ {
        QL.require(impl != null, NO_IMPLEMENTATION_PROVIDED);
        return impl.yearFraction(dateStart, dateEnd, refPeriodStart, refPeriodEnd);
	}

    /**
     * Returns true if this and other belong to the same derived class.
     */
    public boolean eq(final DayCounter another) {
        return equals(another);
    }

    /**
     * @return the negation of {@link DayCounter#eq(DayCounter)}
     */
    public boolean ne(final DayCounter another) {
        return !equals(another);
    }


	//
	// overrides Object
	//

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((impl == null) ? 0 : impl.hashCode());
        result = prime * result + ((impl == null) ? 0 : name().hashCode());
        return result;
    }

//    @Override
//    public boolean equals(final Object obj) {
//        if (this == obj)
//            return true;
//        if (obj == null || !(obj instanceof DayCounter))
//            return false;
//
//        final DayCounter other = (DayCounter) obj;
//        if (this.empty() && other.empty())
//            return true;
//        if (this.name().equals(other.name()))
//            return true;
//        return false;
//    }
    
    @Override
  	public boolean equals(final Object obj) {
    	if (this == obj)
    		return true;
    	if (obj == null)
    		return false;
    	
        return obj instanceof DayCounter &&
        ((DayCounter) obj).fEquals(this);
   	
    }	
    
    @Override
    public String toString() {
        return (impl == null) ? "null" : impl.name();
    }

    
    //
    // protected methods
    //

    protected boolean fEquals(DayCounter other) {
    	if (this.empty() && other.empty())
    		return true;
    	if (this.name().equals(other.name()))
    		return true;
    	return false;  	
    }
    
    //
    // protected inner classes
    //

    /**
     * Base class for day counter implementations.
     */
	protected abstract class Impl {

        //
        // protected abstract methods
        //

        protected abstract String name() /* @ReadOnly */;
        protected abstract /*@Time*/ double yearFraction(final Date dateStart, final Date dateEnd, final Date refPeriodStart, final Date refPeriodEnd) /* @ReadOnly */;


	    //
	    // protected methods
	    //

	    /**
	     * To be overloaded by more complex day counters
	     *
	     * @param dateStart is the starting Date
	     * @param dateEnd is the ending Date
	     * @return the period between two dates as a fraction of year
	     */
	    protected long dayCount(final Date dateStart, final Date dateEnd) /* @ReadOnly */ {
	        return dateEnd.sub(dateStart);
	    }

    }

}