/*******************************************************************************
 * Copyright (c) 2005, 2010 Andrea Bittau, University College London, and others
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Andrea Bittau - initial API and implementation from the PsychoPath XPath 2.0
 *     Mukul Gandhi - bug 274805 - improvements to xs:integer data type
 *     David Carver (STAR) - bug 277774 - XSDecimal returning wrong values.
 *     David Carver (STAR) - bug 262765 - various numeric formatting fixes and calculations
 *     David Carver (STAR) - bug 282223 - Can't Cast Exponential values to Decimal values.
 *     David Carver (STAR) - bug 262765 - fixed edge case where rounding was occuring when it shouldn't. 
 *     Jesper Steen Moller - bug 262765 - fix type tests
 *     David Carver (STAR) - bug 262765 - fixed abs value tests.
 *     Jesper Steen Moller - bug 281028 - fixed division of zero (no, not by)
 *     Mukul Gandhi - bug 280798 - PsychoPath support for JDK 1.4
 *******************************************************************************/

package org.eclipse.wst.xml.xpath2.processor.internal.types;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Iterator;

import org.eclipse.wst.xml.xpath2.api.DynamicContext;
import org.eclipse.wst.xml.xpath2.api.Item;
import org.eclipse.wst.xml.xpath2.api.ResultBuffer;
import org.eclipse.wst.xml.xpath2.api.ResultSequence;
import org.eclipse.wst.xml.xpath2.api.typesystem.TypeDefinition;
import org.eclipse.wst.xml.xpath2.processor.DynamicError;
import org.eclipse.wst.xml.xpath2.processor.ResultSequenceFactory;
import org.eclipse.wst.xml.xpath2.processor.internal.types.builtin.BuiltinTypeLibrary;

/**
 * A representation of the Decimal datatype
 */
public class XSDecimal extends NumericType {

	private static final String XS_DECIMAL = "xs:decimal";
	private BigDecimal _value;
	private XPathDecimalFormat format = new XPathDecimalFormat("0.####################");

	/**
	 * Initiates a representation of 0.0
	 */
	public XSDecimal() {
		this(BigDecimal.valueOf(0));
	}

	/**
	 * Initiates a representation of the supplied number
	 * 
	 * @param x
	 *            Number to be stored
	 */
	public XSDecimal(BigDecimal x) {
		_value = x;
	}
	
	public XSDecimal(String x) {
		//_value = new BigDecimal(x, MathContext.DECIMAL128);
		_value = new BigDecimal(x);
	}

	/**
	 * Retrieves the datatype's full pathname
	 * 
	 * @return "xs:decimal" which is the datatype's full pathname
	 */
	public String string_type() {
		return XS_DECIMAL;
	}

	/**
	 * Retrieves the datatype's name
	 * 
	 * @return "decimal" which is the datatype's name
	 */
	public String type_name() {
		return "decimal";
	}

	/**
	 * Retrieves a String representation of the Decimal value stored
	 * 
	 * @return String representation of the Decimal value stored
	 */
	public String getStringValue() {
		
		if (zero()) {
			return "0";
		}
		
		// strip trailing zeros
		_value = new BigDecimal((_value.toString()).replaceFirst("0*", ""));
		
		return format.xpathFormat(_value);
	}

	/**
	 * Check if this XSDecimal represents 0
	 * 
	 * @return True if this XSDecimal represents 0. False otherwise
	 */
	public boolean zero() {
		return (_value.compareTo(new BigDecimal(0.0)) == 0);
	}

	/**
	 * Creates a new result sequence consisting of the retrievable decimal
	 * number in the supplied result sequence
	 * 
	 * @param arg
	 *            The result sequence from which to extract the decimal number.
	 * @throws DynamicError
	 * @return A new result sequence consisting of the decimal number supplied.
	 */
	public ResultSequence constructor(ResultSequence arg) throws DynamicError {
		if (arg.empty())
			return ResultBuffer.EMPTY;

		Item aat = arg.first();
		
		if (aat instanceof XSDuration || aat instanceof CalendarType ||
			aat instanceof XSBase64Binary || aat instanceof XSHexBinary ||
			aat instanceof XSAnyURI) {
			throw DynamicError.invalidType();
		}
		
		if (aat.getStringValue().indexOf("-INF") != -1) {
			throw DynamicError.cant_cast(null);
		}
		
		if (!isLexicalValue(aat.getStringValue())) {
			throw DynamicError.invalidLexicalValue();
		}
		
		if (!isCastable(aat)) {
			throw DynamicError.cant_cast(null);
		}

		try {
			// XPath doesn't allow for converting Exponents to Decimal values.
			
			return castDecimal(aat);
		} catch (NumberFormatException e) {
			throw DynamicError.cant_cast(null);
		}

	}

	protected boolean isLexicalValue(String value) {
		if (value.equalsIgnoreCase("inf")) {
			return false;
		}
		
		if (value.equalsIgnoreCase("-inf")) {
			return false;
		}
		return true;
	}
	
	private boolean isCastable(Item aat) throws DynamicError {
		if (aat instanceof XSBoolean || aat instanceof NumericType) {
			return true;
		}		
		
		if ((aat.getStringValue().indexOf("E") != -1) || 
			(aat.getStringValue().indexOf("e") != -1)) {
			return false;
		}

		if (aat instanceof XSString || aat instanceof XSUntypedAtomic ||
			aat instanceof NodeType) {
			return true;
		}
		return false;
	}

	private XSDecimal castDecimal(Item aat) {
		if (aat instanceof XSBoolean) {
			if (aat.getStringValue().equals("true")) {
				return new XSDecimal(new BigDecimal("1"));
			} else {
				return new XSDecimal(new BigDecimal("0"));
			}
		}
		return new XSDecimal(aat.getStringValue());
	}
	
	/**
	 * Retrieves the actual value of the number stored
	 * 
	 * @return The actual value of the number stored
	 * @deprecated Use getValue() instead.
	 */
	public double double_value() {
		return _value.doubleValue();
	}
	
	public BigDecimal getValue() {
		return _value;
	}

	/**
	 * Sets the number stored to that supplied
	 * 
	 * @param x
	 *            Number to be stored
	 */
	public void set_double(double x) {
		_value = new BigDecimal(x);
	}

	// comparisons
	/**
	 * Equality comparison between this number and the supplied representation.
	 * @param at
	 *            Representation to be compared with (must currently be of type
	 *            XSDecimal)
	 * 
	 * 
	 * @return True if the 2 representation represent the same number. False
	 *         otherwise
	 */
	public boolean eq(AnyType at, DynamicContext dynamicContext) throws DynamicError {
		XSDecimal dt = null;
		if (!(at instanceof XSDecimal)) { 
			ResultSequence rs = ResultSequenceFactory.create_new(at);
			
			ResultSequence crs = constructor(rs);
			if (crs.empty()) {
				throw DynamicError.throw_type_error();
			}
		
			Item cat = crs.first();

			dt = (XSDecimal) cat;
	    } else {
	    	dt = (XSDecimal) at;
	    }
		return (_value.compareTo(dt.getValue()) == 0);
	}

	/**
	 * Comparison between this number and the supplied representation. 
	 * 
	 * @param arg
	 *            Representation to be compared with (must currently be of type
	 *            XSDecimal)
	 * @return True if the supplied type represents a number smaller than this
	 *         one stored. False otherwise
	 */
	public boolean gt(AnyType arg, DynamicContext context) throws DynamicError {
		Item carg = convertArg(arg);
		
		XSDecimal val = (XSDecimal) get_single_type(carg, XSDecimal.class);
		return (_value.compareTo(val.getValue()) == 1);
	}

	protected Item convertArg(AnyType arg) throws DynamicError {
		ResultSequence rs = ResultSequenceFactory.create_new(arg);
		rs = constructor(rs);
		Item carg = rs.first();
		return carg;
	}
	
	/**
	 * Comparison between this number and the supplied representation. 
	 * 
	 * @param arg
	 *            Representation to be compared with (must currently be of type
	 *            XSDecimal)
	 * @return True if the supplied type represents a number greater than this
	 *         one stored. False otherwise
	 */
	public boolean lt(AnyType arg, DynamicContext context) throws DynamicError {
		Item carg = convertArg(arg);
		XSDecimal val = (XSDecimal) get_single_type(carg, XSDecimal.class);
		return (_value.compareTo(val.getValue()) == -1);
	}

	// math
	/**
	 * Mathematical addition operator between this XSDecimal and the supplied
	 * ResultSequence. Due to no numeric type promotion or conversion, the
	 * ResultSequence must be of type XSDecimal.
	 * 
	 * @param arg
	 *            The ResultSequence to perform an addition with
	 * @return A XSDecimal consisting of the result of the mathematical
	 *         addition.
	 */
	public ResultSequence plus(ResultSequence arg) throws DynamicError {
		// get arg
		ResultSequence carg = convertResultSequence(arg);
		Item at = get_single_arg(carg);
		if (!(at instanceof XSDecimal))
			DynamicError.throw_type_error();
		XSDecimal dt = (XSDecimal) at;

		// own it
		return ResultSequenceFactory.create_new(new XSDecimal(_value.add(dt.getValue())));
	}
	
	private ResultSequence convertResultSequence(ResultSequence arg)
			throws DynamicError {
		ResultSequence carg = arg;
		Iterator it = carg.iterator();
		while (it.hasNext()) {
			AnyType type = (AnyType) it.next();
			if (type.string_type().equals("xs:untypedAtomic") ||
				type.string_type().equals("xs:string")) {
				throw DynamicError.invalidType();
			}
		}
		carg = constructor(carg);
		return carg;
	}	

	/**
	 * Mathematical subtraction operator between this XSDecimal and the supplied
	 * ResultSequence. 
	 * 
	 * @param arg
	 *            The ResultSequence to perform a subtraction with
	 * @return A XSDecimal consisting of the result of the mathematical
	 *         subtraction.
	 */
	public ResultSequence minus(ResultSequence arg) throws DynamicError {
		
		ResultSequence carg = convertResultSequence(arg);

		Item at = get_single_arg(carg);
		if (!(at instanceof XSDecimal))
			DynamicError.throw_type_error();
		XSDecimal dt = (XSDecimal) at;

		return ResultSequenceFactory.create_new(new XSDecimal(_value.subtract(dt.getValue())));
	}

	/**
	 * Mathematical multiplication operator between this XSDecimal and the
	 * supplied ResultSequence. 
	 * 
	 * @param arg
	 *            The ResultSequence to perform a multiplication with
	 * @return A XSDecimal consisting of the result of the mathematical
	 *         multiplication.
	 */
	public ResultSequence times(ResultSequence arg) {
		ResultSequence carg = convertResultSequence(arg);

		XSDecimal val = (XSDecimal) get_single_type(carg, XSDecimal.class);
		BigDecimal result = _value.multiply(val.getValue());
		return ResultSequenceFactory.create_new(new XSDecimal(result));
	}

	/**
	 * Mathematical division operator between this XSDecimal and the supplied
	 * ResultSequence. 
	 * 
	 * @param arg
	 *            The ResultSequence to perform a division with
	 * @return A XSDecimal consisting of the result of the mathematical
	 *         division.
	 */
	public ResultSequence div(ResultSequence arg) throws DynamicError {
		ResultSequence carg = convertResultSequence(arg);
			
		XSDecimal val = (XSDecimal) get_single_type(carg, XSDecimal.class);
		if (val.zero()) {
			throw DynamicError.div_zero(null);
		}
		BigDecimal result = getValue().divide(val.getValue(), 18, BigDecimal.ROUND_HALF_EVEN);
		return ResultSequenceFactory.create_new(new XSDecimal(result));
	}

	/**
	 * Mathematical integer division operator between this XSDecimal and the
	 * supplied ResultSequence. Due to no numeric type promotion or conversion,
	 * the ResultSequence must be of type XSDecimal.
	 * 
	 * @param arg
	 *            The ResultSequence to perform an integer division with
	 * @return A XSInteger consisting of the result of the mathematical integer
	 *         division.
	 */
	public ResultSequence idiv(ResultSequence arg) throws DynamicError {
		ResultSequence carg = convertResultSequence(arg);

		XSDecimal val = (XSDecimal) get_single_type(carg, XSDecimal.class);

		if (val.zero())
			throw DynamicError.div_zero(null);
		BigInteger _ivalue = _value.toBigInteger();
		BigInteger ival =  val.getValue().toBigInteger();
		BigInteger result = _ivalue.divide(ival);
		return ResultSequenceFactory.create_new(new 
				           XSInteger(result));
	}

	/**
	 * Mathematical modulus operator between this XSDecimal and the supplied
	 * ResultSequence. Due to no numeric type promotion or conversion, the
	 * ResultSequence must be of type XSDecimal.
	 * 
	 * @param arg
	 *            The ResultSequence to perform a modulus with
	 * @return A XSDecimal consisting of the result of the mathematical modulus.
	 */
	public ResultSequence mod(ResultSequence arg) throws DynamicError {
		ResultSequence carg = convertResultSequence(arg);

		XSDecimal val = (XSDecimal) get_single_type(carg, XSDecimal.class);
		
		// BigDecimal result = _value.remainder(val.getValue());
		BigDecimal result = remainder(_value, val.getValue()); 
		
		return ResultSequenceFactory.create_new(new XSDecimal(result));
	}

	public static BigDecimal remainder(BigDecimal value, BigDecimal divisor) {
		// return value.remainder(divisor);
		
		// appx as of now. JDK 1.4 doesn't support BigDecimal.remainder(..)
		BigDecimal dividend = value.divide(divisor, BigDecimal.ROUND_DOWN);
		BigDecimal ceilDividend = new BigDecimal(dividend.toBigInteger());
		
		return value.subtract(ceilDividend.multiply(divisor)); 
	}
	
	/**
	 * Negation of the number stored
	 * 
	 * @return A XSDecimal representing the negation of this XSDecimal
	 */
	public ResultSequence unary_minus() {
		BigDecimal result = _value.negate();
		return ResultSequenceFactory.create_new(new XSDecimal(result));
	}

	// functions
	/**
	 * Absolutes the number stored
	 * 
	 * @return A XSDecimal representing the absolute value of the number stored
	 */
	public NumericType abs() {
		return new XSDecimal(_value.abs());
	}

	/**
	 * Returns the smallest integer greater than the number stored
	 * 
	 * @return A XSDecimal representing the smallest integer greater than the
	 *         number stored
	 */
	public NumericType ceiling() {
		BigDecimal ceiling = _value.setScale(0, BigDecimal.ROUND_CEILING);
		return new XSDecimal(ceiling);
	}

	/**
	 * Returns the largest integer smaller than the number stored
	 * 
	 * @return A XSDecimal representing the largest integer smaller than the
	 *         number stored
	 */
	public NumericType floor() {
		BigDecimal floor = _value.setScale(0, BigDecimal.ROUND_FLOOR);
		return new XSDecimal(floor);
	}

	/**
	 * Returns the closest integer of the number stored.
	 * 
	 * @return A XSDecimal representing the closest long of the number stored.
	 */
	public NumericType round() {
		BigDecimal round = _value.setScale(0, BigDecimal.ROUND_UP);
		return new XSDecimal(round);
	}

	/**
	 * Returns the closest integer of the number stored.
	 * 
	 * @return A XSDecimal representing the closest long of the number stored.
	 */
	public NumericType round_half_to_even() {
		return round_half_to_even(0);
	}

	/**
	 * Returns the closest integer of the number stored with the specified precision.
	 * 
	 * @param precision An integer precision 
	 * @return A XSDecimal representing the closest long of the number stored.
	 */
	public NumericType round_half_to_even(int precision) {
		BigDecimal round = _value.setScale(precision, BigDecimal.ROUND_HALF_EVEN);
		return new XSDecimal(round);
	}

	public TypeDefinition getTypeDefinition() {
		return BuiltinTypeLibrary.XS_DECIMAL;
	}

	@Override
	public Number getNativeValue() {
		return _value;
	}

}