/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 freemarker.template.utility;

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

Number- and math-related utilities.
Since:
2.3.20/**
 * Number- and math-related utilities.
 * 
 * @since 2.3.20
 */
public class NumberUtil {

    private static final BigDecimal BIG_DECIMAL_INT_MIN = BigDecimal.valueOf(Integer.MIN_VALUE);
    private static final BigDecimal BIG_DECIMAL_INT_MAX = BigDecimal.valueOf(Integer.MAX_VALUE);
    private static final BigInteger BIG_INTEGER_INT_MIN = BIG_DECIMAL_INT_MIN.toBigInteger();
    private static final BigInteger BIG_INTEGER_INT_MAX = BIG_DECIMAL_INT_MAX.toBigInteger();

    private NumberUtil() { }
    
    public static boolean isInfinite(Number num) {
        if (num instanceof Double) {
            return ((Double) num).isInfinite();
        } else if (num instanceof Float) {
            return ((Float) num).isInfinite();
        } else if (hasTypeThatIsKnownToNotSupportInfiniteAndNaN(num)) {
            return false;
        } else {
            throw new UnsupportedNumberClassException(num.getClass());
        }           
    }

    public static boolean isNaN(Number num) {
        if (num instanceof Double) {
            return ((Double) num).isNaN();
        } else if (num instanceof Float) {
            return ((Float) num).isNaN();
        } else if (hasTypeThatIsKnownToNotSupportInfiniteAndNaN(num)) {
            return false;
        } else {
            throw new UnsupportedNumberClassException(num.getClass());
        }           
    }

    
Throws:
ArithmeticException – if the number is NaN
Returns:
-1 for negative, 0 for zero, 1 for positive./**
     * @return -1 for negative, 0 for zero, 1 for positive.
     * @throws ArithmeticException if the number is NaN
     */
    public static int getSignum(Number num) throws ArithmeticException {
        if (num instanceof Integer) {
            int n = ((Integer) num).intValue();
            return n > 0 ? 1 : (n == 0 ? 0 : -1);
        } else if (num instanceof BigDecimal) {
            BigDecimal n = (BigDecimal) num;
            return n.signum();
        } else if (num instanceof Double) {
            double n = ((Double) num).doubleValue();
            if (n > 0) return 1;
            else if (n == 0) return 0;
            else if (n < 0) return -1;
            else throw new ArithmeticException("The signum of " + n + " is not defined.");  // NaN
        } else if (num instanceof Float) {
            float n = ((Float) num).floatValue();
            if (n > 0) return 1;
            else if (n == 0) return 0;
            else if (n < 0) return -1;
            else throw new ArithmeticException("The signum of " + n + " is not defined.");  // NaN
        } else if (num instanceof Long) {
            long n = ((Long) num).longValue();
            return n > 0 ? 1 : (n == 0 ? 0 : -1);
        } else if (num instanceof Short) {
            short n = ((Short) num).shortValue();
            return n > 0 ? 1 : (n == 0 ? 0 : -1);
        } else if (num instanceof Byte) {
            byte n = ((Byte) num).byteValue();
            return n > 0 ? 1 : (n == 0 ? 0 : -1);
        } else if (num instanceof BigInteger) {
            BigInteger n = (BigInteger) num;
            return n.signum();
        } else {
            throw new UnsupportedNumberClassException(num.getClass());
        }
    }
    
    
Tells if a BigDecimal stores a whole number. For example, it returns true for 1.0000, but false for 1.0001. 
Since:
2.3.21/**
     * Tells if a {@link BigDecimal} stores a whole number. For example, it returns {@code true} for {@code 1.0000},
     * but {@code false} for {@code 1.0001}.
     * 
     * @since 2.3.21
     */
    static public boolean isIntegerBigDecimal(BigDecimal bd) {
        // [Java 1.5] Try to utilize BigDecimal.toXxxExact methods
        return bd.scale() <= 0  // A fast check that whole numbers usually (not always) match
               || bd.setScale(0, BigDecimal.ROUND_DOWN).compareTo(bd) == 0;  // This is rather slow
        // Note that `bd.signum() == 0 || bd.stripTrailingZeros().scale() <= 0` was also tried for the last
        // condition, but stripTrailingZeros was slower than setScale + compareTo.
    }
    
    
Tells if the type of the parameter number is known to not be able to represent infinite (positive or negative) and NaN. If this returns false, that doesn't mean that it can do that, because it's maybe just that this utility doesn't know that type. 
Since:
2.3.28/**
     * Tells if the type of the parameter number is known to not be able to represent infinite (positive or negative)
     * and NaN. If this returns {@code false}, that doesn't mean that it can do that, because it's maybe just that this
     * utility doesn't know that type.
     * 
     * @since 2.3.28
     */
    public static boolean hasTypeThatIsKnownToNotSupportInfiniteAndNaN(Number num) {
        return num instanceof Integer || num instanceof BigDecimal || num instanceof Long
                || num instanceof Short || num instanceof Byte || num instanceof BigInteger;
    }

    
Converts a Number to int whose mathematical value is exactly the same as of the original number. 
Throws:
ArithmeticException –  if the conversion to int is not possible without losing precision or overflow/underflow.
Since:
2.3.22/**
     * Converts a {@link Number} to {@code int} whose mathematical value is exactly the same as of the original number.
     * 
     * @throws ArithmeticException
     *             if the conversion to {@code int} is not possible without losing precision or overflow/underflow.
     * 
     * @since 2.3.22
     */
    public static int toIntExact(Number num) {
        if (num instanceof Integer || num instanceof Short || num instanceof Byte) {
            return num.intValue();
        } else if (num instanceof Long) {
            final long n = num.longValue();
            final int result = (int) n;
            if (n != result) {
                throw newLossyConverionException(num, Integer.class);
            }
            return result;
        } else if (num instanceof Double || num instanceof Float) {
            final double n = num.doubleValue();
            if (n % 1 != 0 || n < Integer.MIN_VALUE || n > Integer.MAX_VALUE) {
                throw newLossyConverionException(num, Integer.class);
            }
            return (int) n;
        } else if (num instanceof BigDecimal) {
            // [Java 1.5] Use BigDecimal.toIntegerExact()
            BigDecimal n = (BigDecimal) num;
            if (!isIntegerBigDecimal(n)
                    || n.compareTo(BIG_DECIMAL_INT_MAX) > 0 || n.compareTo(BIG_DECIMAL_INT_MIN) < 0) {
                throw newLossyConverionException(num, Integer.class);
            }
            return n.intValue();
        } else if (num instanceof BigInteger) {
            BigInteger n = (BigInteger) num;
            if (n.compareTo(BIG_INTEGER_INT_MAX) > 0 || n.compareTo(BIG_INTEGER_INT_MIN) < 0) {
                throw newLossyConverionException(num, Integer.class);
            }
            return n.intValue();
        } else {
            throw new UnsupportedNumberClassException(num.getClass());
        }
    }

    private static ArithmeticException newLossyConverionException(Number fromValue, Class/*<Number>*/ toType) {
        return new ArithmeticException(
                "Can't convert " + fromValue + " to type " + ClassUtil.getShortClassName(toType) + " without loss.");
    }
    
}