////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 Saxonica Limited.
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package net.sf.saxon.value;

import net.sf.saxon.expr.sort.DoubleSortComparer;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.util.FastStringBuffer;
import net.sf.saxon.type.AtomicType;
import net.sf.saxon.type.BuiltInAtomicType;

import java.math.BigDecimal;
import java.math.BigInteger;

/**
* A numeric (double precision floating point) value
*/

public final class DoubleValue extends NumericValue {

    public static final DoubleValue ZERO = new DoubleValue(0.0);
    public static final DoubleValue NEGATIVE_ZERO = new DoubleValue(-0.0);
    public static final DoubleValue ONE = new DoubleValue(1.0);
    public static final DoubleValue NaN = new DoubleValue(Double.NaN);

    private double value;

    /**
    * Constructor supplying a double
    * @param value the value of the NumericValue
    */

    public DoubleValue(double value) {
        this.value = value;
        typeLabel = BuiltInAtomicType.DOUBLE;
    }

    /**
     * Constructor supplying a double and an AtomicType, for creating
     * a value that belongs to a user-defined subtype of xs:double. It is
     * the caller's responsibility to ensure that the supplied value conforms
     * to the supplied type.
     * @param value the value of the NumericValue
     * @param type the type of the value. This must be a subtype of xs:double, and the
     * value must conform to this type. The methosd does not check these conditions.
     */

    public DoubleValue(double value, AtomicType type) {
        this.value = value;
        typeLabel = type;
    }

    /**
     * Static factory method (for convenience in compiled bytecode)
     * @param value the value of the double
     * @return a new DoubleValue
     */

    public static DoubleValue makeDoubleValue(double value) {
        return new DoubleValue(value);
    }

    /**
     * Create a copy of this atomic value, with a different type label
     *
     * @param typeLabel the type label of the new copy. The caller is responsible for checking that
     *                  the value actually conforms to this type.
     */

    /*@NotNull*/ public AtomicValue copyAsSubType(AtomicType typeLabel) {
        DoubleValue v = new DoubleValue(value);
        v.typeLabel = typeLabel;
        return v;
    }

    /**
     * Determine the primitive type of the value. This delivers the same answer as
     * getItemType().getPrimitiveItemType(). The primitive types are
     * the 19 primitive types of XML Schema, plus xs:integer, xs:dayTimeDuration and xs:yearMonthDuration,
     * and xs:untypedAtomic. For external objects, the result is AnyAtomicType.
     */

    public BuiltInAtomicType getPrimitiveType() {
        return BuiltInAtomicType.DOUBLE;
    }

    /**
     * Return this numeric value as a double
     * @return the value as a double
     */

    public double getDoubleValue() {
        return value;
    }

    /**
     * Get the numeric value converted to a float
     *
     * @return a float representing this numeric value; NaN if it cannot be converted
     */
    @Override
    public float getFloatValue() {
        return (float)value;
    }

    /**
     * Get the numeric value converted to a decimal
     *
     * @return a decimal representing this numeric value;
     * @throws net.sf.saxon.trans.XPathException
     *          if the value cannot be converted, for example if it is NaN or infinite
     */
    @Override
    public BigDecimal getDecimalValue() throws XPathException {
        return new BigDecimal(value);
    }

    /**
     * Return the numeric value as a Java long.
     *
     * @return the numeric value as a Java long. This performs truncation
     *         towards zero.
     * @throws net.sf.saxon.trans.XPathException
     *          if the value cannot be converted
     */
    @Override
    public long longValue() throws XPathException {
        return (long)value;
    }

    /**
     * Get the hashCode. This must conform to the rules for other NumericValue hashcodes
     * @see NumericValue#hashCode
     */

    public int hashCode() {
        if (value > Integer.MIN_VALUE && value < Integer.MAX_VALUE) {
            return (int)value;
        } else {
            return new Double(value).hashCode();
        }
    }

    /**
     * Test whether the value is the double/float value NaN
     */

    public boolean isNaN() {
        return Double.isNaN(value);
    }

    /**
     * Get the effective boolean value
     * @return the effective boolean value (true unless the value is zero or NaN)
     */
    public boolean effectiveBooleanValue() {
        return (value!=0.0 && !Double.isNaN(value));
    }

    /**
     * Convert the double to a string according to the XPath 2.0 rules
     * @return the string value
     */
//    public String getStringValue() {
//        return doubleToString(value).toString(); //, Double.toString(value)).toString();
//    }

    /**
     * Convert the double to a string according to the XPath 2.0 rules
     * @return the string value
     */
    public CharSequence getPrimitiveStringValue() {
        return doubleToString(value);
    }

    /**
     * Get the canonical lexical representation as defined in XML Schema. This is not always the same
     * as the result of casting to a string according to the XPath rules. For xs:double, the canonical
     * representation always uses exponential notation.
     */

    public CharSequence getCanonicalLexicalRepresentation() {
        FastStringBuffer fsb = new FastStringBuffer(FastStringBuffer.TINY);
        return FloatingPointConverter.appendDouble(fsb, value, true);
    }

    /**
     * Internal method used for conversion of a double to a string
     * @param value the actual value
     * @return the value converted to a string, according to the XPath casting rules.
     */

    public static CharSequence doubleToString(double value) {
        return FloatingPointConverter.appendDouble(new FastStringBuffer(FastStringBuffer.TINY), value, false);
    }


    /**
    * Negate the value
    */

    public NumericValue negate() {
        return new DoubleValue(-value);
    }

    /**
    * Implement the XPath floor() function
    */

    public NumericValue floor() {
        return new DoubleValue(Math.floor(value));
    }

    /**
    * Implement the XPath ceiling() function
    */

    public NumericValue ceiling() {
        return new DoubleValue(Math.ceil(value));
    }

    /**
    * Implement the XPath round() function
    */

    public NumericValue round(int scale) {
        if (Double.isNaN(value)) {
            return this;
        }
        if (Double.isInfinite(value)) {
            return this;
        }
        if (value == 0.0) {
            return this;    // handles the negative zero case
        }
        
        if (value == -0.0) {
            return this;    // handles the negative zero case
        }
        
        if (value >= -0.5 && value < 0.0) {
            return new DoubleValue(-0.0);
        }
        
        if (scale==0 && value > Long.MIN_VALUE && value < Long.MAX_VALUE) {
            return new DoubleValue(Math.round(value));
        }

        // Convert to a scaled integer, by multiplying by 10^scale

        double factor = Math.pow(10, scale+1);
        double d = Math.abs(value * factor);

        if (Double.isInfinite(d)) {
            // double arithmetic has overflowed - do it in decimal
            BigDecimal dec = new BigDecimal(value);
            dec = dec.setScale(scale, BigDecimal.ROUND_HALF_UP);
            return new DoubleValue(dec.doubleValue());
        }

        // Now apply any rounding needed, using the "round half to even" rule***CHANGE

        double rem = d % 10;
        if (rem >= 5) {
            d += (10-rem);
        } else if (rem < 5){
            d -= rem;
        }

        // Now convert back to the original magnitude

        d /= factor;
        if (value < 0) {
            d = -d;
        }
        return new DoubleValue(d);
    }

    /**
    * Implement the XPath round-to-half-even() function
    */

    public NumericValue roundHalfToEven(int scale) {
        if (Double.isNaN(value)) return this;
        if (Double.isInfinite(value)) return this;
        if (value==0.0) return this;    // handles the negative zero case

        // Convert to a scaled integer, by multiplying by 10^scale

        double factor = Math.pow(10, scale+1);
        double d = Math.abs(value * factor);

        if (Double.isInfinite(d)) {
            // double arithmetic has overflowed - do it in decimal
            BigDecimal dec = new BigDecimal(value);
            dec = dec.setScale(scale, BigDecimal.ROUND_HALF_EVEN);
            return new DoubleValue(dec.doubleValue());
        }

        // Now apply any rounding needed, using the "round half to even" rule

        double rem = d % 10;
        if (rem > 5) {
            d += (10-rem);
        } else if (rem < 5){
            d -= rem;
        } else {
            // round half to even - check the last bit
            if ((d % 20) == 15) {
                d +=5 ;
            } else {
                d -=5;
            }
        }

        // Now convert back to the original magnitude

        d /= factor;
        if (value < 0) {
            d = -d;
        }
        return new DoubleValue(d);

    }

    /**
     * Determine whether the value is negative, zero, or positive
     * @return -1 if negative, 0 if zero (including negative zero) or NaN, +1 if positive
     */

    public int signum() {
        if (Double.isNaN(value)) {
            return 0;
        }
        if (value > 0) return 1;
        if (value == 0) return 0;
        return -1;
    }

    /**
    * Determine whether the value is a whole number, that is, whether it compares
    * equal to some integer
    */

    public boolean isWholeNumber() {
        return value == Math.floor(value) && !Double.isInfinite(value);
    }

    /**
     * Get the absolute value as defined by the XPath abs() function
     * @return the absolute value
     * @since 9.2
     */

    public NumericValue abs() {
        if (value > 0.0) {
            return this;
        } else {
            return new DoubleValue(Math.abs(value));
        }
    }

    /**
     * Compare the value to a long.
     * @param other the value to be compared with
     * @return -1 if this is less, 0 if this is equal, +1 if this is greater or if this is NaN
     */

    public int compareTo(long other) {
        double otherDouble = (double)other;
        if (value == otherDouble) return 0;
        if (value < otherDouble) return -1;
        return +1;
    }

    /**
     * Get an object that implements XML Schema comparison semantics
     */

    public Comparable getSchemaComparable() {
        // convert negative to positive zero because Double.compareTo() does the wrong thing
        // TODO: what shall we do with NaN?
        return (value == 0.0 ? 0.0 : value);
    }

    /**
     * Determine whether two atomic values are identical, as determined by XML Schema rules. This is a stronger
     * test than equality (even schema-equality); for example two dateTime values are not identical unless
     * they are in the same timezone.
     * <p>Note that even this check ignores the type annotation of the value. The integer 3 and the short 3
     * are considered identical, even though they are not fully interchangeable. "Identical" means the
     * same point in the value space, regardless of type annotation.</p>
     * <p>NaN is identical to itself.</p>
     *
     * @param v the other value to be compared with this one
     * @return true if the two values are identical, false otherwise.
     */

    public boolean isIdentical(/*@NotNull*/ AtomicValue v) {
        return v instanceof DoubleValue && DoubleSortComparer.getInstance().comparesEqual(this, (DoubleValue)v);
    }

    /**
     * Diagnostic method: print the sign, exponent, and significand
     * @param d the double to be diagnosed
     */

    public static void printInternalForm(double d) {
        System.err.println("==== Double " + d + " ====");
        long bits = Double.doubleToLongBits(d);
        System.err.println("Internal form: " + Long.toHexString(bits));
        if (bits == 0x7ff0000000000000L) {
            System.err.println("+Infinity");
        } else if (bits == 0xfff0000000000000L) {
            System.err.println("-Infinity");
        } else if (bits == 0x7ff8000000000000L) {
            System.err.println("NaN");
        } else {
            int s = ((bits >> 63) == 0) ? 1 : -1;
            int e = (int)((bits >> 52) & 0x7ffL);
            long m = (e == 0) ?
                             (bits & 0xfffffffffffffL) << 1 :
                             (bits & 0xfffffffffffffL) | 0x10000000000000L;
            int exponent = e-1075;
            System.err.println("Sign: " + s);
            System.err.println("Raw Exponent: " + e);
            System.err.println("Exponent: " + exponent);
            System.err.println("Significand: " + m);
            BigDecimal dec = BigDecimal.valueOf(m);
            if (exponent > 0) {
                dec = dec.multiply(new BigDecimal(BigInteger.valueOf(2).pow(exponent)));
            } else {
                // Next line is sometimes failing, e.g. on -3.62e-5. Not investigated.
                dec = dec.divide(new BigDecimal(BigInteger.valueOf(2).pow(-exponent)), BigDecimal.ROUND_HALF_EVEN);
            }
            System.err.println("Exact value: " + (s>0?"":"-") + dec);
        }
    }

    public static DoubleValue fromInternalForm(String hex) {
        return new DoubleValue(Double.longBitsToDouble(Long.parseLong(hex, 16)));

    }

    public static void main(String[] args) {
        System.err.println(fromInternalForm("3fdeaee8744b05f1"));
        //printInternalForm(0.4794255386042030002732879352155713880818033679406000675);
//        System.err.println("3e0 : " + new DoubleValue(3e0).isWholeNumber());
//        System.err.println("3e1 : " + new DoubleValue(3e1).isWholeNumber());
//        System.err.println("3e-1 : " + new DoubleValue(3e-1).isWholeNumber());
//        System.err.println("1e0 : " + new DoubleValue(1e0).isWholeNumber());
//        System.err.println("1 - 20");
//        printInternalForm(1e0);
//        printInternalForm(2e0);
//        printInternalForm(3e0);
//        printInternalForm(4e0);
//        printInternalForm(5e0);
//        printInternalForm(6e0);
//        printInternalForm(7e0);
//        printInternalForm(8e0);
//        printInternalForm(9e0);
//        printInternalForm(10e0);
//        printInternalForm(11e0);
//        printInternalForm(12e0);
//        printInternalForm(13e0);
//        printInternalForm(14e0);
//        printInternalForm(15e0);
//        printInternalForm(16e0);
//        printInternalForm(17e0);
//        printInternalForm(18e0);
//        printInternalForm(19e0);
//        printInternalForm(20e0);
//        System.err.println("3.0000001");
//        printInternalForm(3.0000001e0);
//        System.err.println("1");
//        printInternalForm(1e0);
//        System.err.println("1.00000001");
//        printInternalForm(1.00000001e0);
//        System.err.println("0.9999999e0");
//        printInternalForm(0.9999999e0);
//        System.err.println("30");
//        printInternalForm(3e1);
//        System.err.println("== 0.3 ==");
//        printInternalForm(3e-1);
        
    }

 }

