/*
 * 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 org.apache.el.lang;

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

import org.apache.el.util.MessageFactory;


/**
 * A helper class of Arithmetic defined by the EL Specification
 * @author Jacob Hookom [jacob@hookom.net]
 */
public abstract class ELArithmetic {

    public static final class BigDecimalDelegate extends ELArithmetic {

        @Override
        protected Number add(Number num0, Number num1) {
            return ((BigDecimal) num0).add((BigDecimal) num1);
        }

        @Override
        protected Number coerce(Number num) {
            if (num instanceof BigDecimal)
                return num;
            if (num instanceof BigInteger)
                return new BigDecimal((BigInteger) num);
            return new BigDecimal(num.doubleValue());
        }

        @Override
        protected Number coerce(String str) {
            return new BigDecimal(str);
        }

        @Override
        protected Number divide(Number num0, Number num1) {
            return ((BigDecimal) num0).divide((BigDecimal) num1,
                    BigDecimal.ROUND_HALF_UP);
        }

        @Override
        protected Number subtract(Number num0, Number num1) {
            return ((BigDecimal) num0).subtract((BigDecimal) num1);
        }

        @Override
        protected Number mod(Number num0, Number num1) {
            return new Double(num0.doubleValue() % num1.doubleValue());
        }

        @Override
        protected Number multiply(Number num0, Number num1) {
            return ((BigDecimal) num0).multiply((BigDecimal) num1);
        }

        @Override
        public boolean matches(Object obj0, Object obj1) {
            return (obj0 instanceof BigDecimal || obj1 instanceof BigDecimal);
        }
    }

    public static final class BigIntegerDelegate extends ELArithmetic {

        @Override
        protected Number add(Number num0, Number num1) {
            return ((BigInteger) num0).add((BigInteger) num1);
        }

        @Override
        protected Number coerce(Number num) {
            if (num instanceof BigInteger)
                return num;
            return new BigInteger(num.toString());
        }

        @Override
        protected Number coerce(String str) {
            return new BigInteger(str);
        }

        @Override
        protected Number divide(Number num0, Number num1) {
            return (new BigDecimal((BigInteger) num0)).divide(new BigDecimal((BigInteger) num1), BigDecimal.ROUND_HALF_UP);
        }

        @Override
        protected Number multiply(Number num0, Number num1) {
            return ((BigInteger) num0).multiply((BigInteger) num1);
        }

        @Override
        protected Number mod(Number num0, Number num1) {
            return ((BigInteger) num0).mod((BigInteger) num1);
        }

        @Override
        protected Number subtract(Number num0, Number num1) {
            return ((BigInteger) num0).subtract((BigInteger) num1);
        }

        @Override
        public boolean matches(Object obj0, Object obj1) {
            return (obj0 instanceof BigInteger || obj1 instanceof BigInteger);
        }
    }

    public static final class DoubleDelegate extends ELArithmetic {

        @Override
        protected Number add(Number num0, Number num1) {
            // could only be one of these
            if (num0 instanceof BigDecimal) {
                return ((BigDecimal) num0).add(new BigDecimal(num1.doubleValue()));
            } else if (num1 instanceof BigDecimal) {
                return ((new BigDecimal(num0.doubleValue()).add((BigDecimal) num1)));
            }
            return new Double(num0.doubleValue() + num1.doubleValue());
        }

        @Override
        protected Number coerce(Number num) {
            if (num instanceof Double)
                return num;
            if (num instanceof BigInteger)
                return new BigDecimal((BigInteger) num);
            return new Double(num.doubleValue());
        }

        @Override
        protected Number coerce(String str) {
            return new Double(str);
        }

        @Override
        protected Number divide(Number num0, Number num1) {
            return new Double(num0.doubleValue() / num1.doubleValue());
        }

        @Override
        protected Number mod(Number num0, Number num1) {
            return new Double(num0.doubleValue() % num1.doubleValue());
        }

        @Override
        protected Number subtract(Number num0, Number num1) {
            // could only be one of these
            if (num0 instanceof BigDecimal) {
                return ((BigDecimal) num0).subtract(new BigDecimal(num1.doubleValue()));
            } else if (num1 instanceof BigDecimal) {
                return ((new BigDecimal(num0.doubleValue()).subtract((BigDecimal) num1)));
            }
            return new Double(num0.doubleValue() - num1.doubleValue());
        }

        @Override
        protected Number multiply(Number num0, Number num1) {
            // could only be one of these
            if (num0 instanceof BigDecimal) {
                return ((BigDecimal) num0).multiply(new BigDecimal(num1.doubleValue()));
            } else if (num1 instanceof BigDecimal) {
                return ((new BigDecimal(num0.doubleValue()).multiply((BigDecimal) num1)));
            }
            return new Double(num0.doubleValue() * num1.doubleValue());
        }

        @Override
        public boolean matches(Object obj0, Object obj1) {
            return (obj0 instanceof Double
                    || obj1 instanceof Double
                    || obj0 instanceof Float
                    || obj1 instanceof Float
                    || (obj0 instanceof String && ELSupport
                            .isStringFloat((String) obj0)) || (obj1 instanceof String && ELSupport
                    .isStringFloat((String) obj1)));
        }
    }

    public static final class LongDelegate extends ELArithmetic {

        @Override
        protected Number add(Number num0, Number num1) {
            return Long.valueOf(num0.longValue() + num1.longValue());
        }

        @Override
        protected Number coerce(Number num) {
            if (num instanceof Long)
                return num;
            return Long.valueOf(num.longValue());
        }

        @Override
        protected Number coerce(String str) {
            return Long.valueOf(str);
        }

        @Override
        protected Number divide(Number num0, Number num1) {
            return Long.valueOf(num0.longValue() / num1.longValue());
        }

        @Override
        protected Number mod(Number num0, Number num1) {
            return Long.valueOf(num0.longValue() % num1.longValue());
        }

        @Override
        protected Number subtract(Number num0, Number num1) {
            return Long.valueOf(num0.longValue() - num1.longValue());
        }

        @Override
        protected Number multiply(Number num0, Number num1) {
            return Long.valueOf(num0.longValue() * num1.longValue());
        }

        @Override
        public boolean matches(Object obj0, Object obj1) {
            return (obj0 instanceof Long || obj1 instanceof Long);
        }
    }

    public static final BigDecimalDelegate BIGDECIMAL = new BigDecimalDelegate();

    public static final BigIntegerDelegate BIGINTEGER = new BigIntegerDelegate();

    public static final DoubleDelegate DOUBLE = new DoubleDelegate();

    public static final LongDelegate LONG = new LongDelegate();

    private static final Long ZERO = Long.valueOf(0);

    public static final Number add(final Object obj0, final Object obj1) {
        final ELArithmetic delegate = findDelegate(obj0, obj1);
        if (delegate == null) {
            return Long.valueOf(0);
        }

        Number num0 = delegate.coerce(obj0);
        Number num1 = delegate.coerce(obj1);

        return delegate.add(num0, num1);
    }

    public static final Number mod(final Object obj0, final Object obj1) {
        if (obj0 == null && obj1 == null) {
            return Long.valueOf(0);
        }

        final ELArithmetic delegate;
        if (BIGDECIMAL.matches(obj0, obj1))
            delegate = DOUBLE;
        else if (DOUBLE.matches(obj0, obj1))
            delegate = DOUBLE;
        else if (BIGINTEGER.matches(obj0, obj1))
            delegate = BIGINTEGER;
        else
            delegate = LONG;

        Number num0 = delegate.coerce(obj0);
        Number num1 = delegate.coerce(obj1);

        return delegate.mod(num0, num1);
    }

    public static final Number subtract(final Object obj0, final Object obj1) {
        final ELArithmetic delegate = findDelegate(obj0, obj1);
        if (delegate == null) {
            return Long.valueOf(0);
        }

        Number num0 = delegate.coerce(obj0);
        Number num1 = delegate.coerce(obj1);

        return delegate.subtract(num0, num1);
    }

    public static final Number divide(final Object obj0, final Object obj1) {
        if (obj0 == null && obj1 == null) {
            return ZERO;
        }

        final ELArithmetic delegate;
        if (BIGDECIMAL.matches(obj0, obj1))
            delegate = BIGDECIMAL;
        else if (BIGINTEGER.matches(obj0, obj1))
            delegate = BIGDECIMAL;
        else
            delegate = DOUBLE;

        Number num0 = delegate.coerce(obj0);
        Number num1 = delegate.coerce(obj1);

        return delegate.divide(num0, num1);
    }

    public static final Number multiply(final Object obj0, final Object obj1) {
        final ELArithmetic delegate = findDelegate(obj0, obj1);
        if (delegate == null) {
            return Long.valueOf(0);
        }

        Number num0 = delegate.coerce(obj0);
        Number num1 = delegate.coerce(obj1);

        return delegate.multiply(num0, num1);
    }

    private static ELArithmetic findDelegate(final Object obj0, final Object obj1) {
        if (obj0 == null && obj1 == null) {
            return null;
        }

        if (BIGDECIMAL.matches(obj0, obj1)) {
            return BIGDECIMAL;
        } else if (DOUBLE.matches(obj0, obj1)) {
            if (BIGINTEGER.matches(obj0, obj1)) {
                return BIGDECIMAL;
            } else {
                return DOUBLE;
            }
        } else if (BIGINTEGER.matches(obj0, obj1)) {
            return BIGINTEGER;
        } else {
            return LONG;
        }
    }

    public static final boolean isNumber(final Object obj) {
        return (obj != null && isNumberType(obj.getClass()));
    }

    public static final boolean isNumberType(final Class<?> type) {
        return type == Long.TYPE || type == Double.TYPE ||
            type == Byte.TYPE || type == Short.TYPE ||
            type == Integer.TYPE || type == Float.TYPE ||
            Number.class.isAssignableFrom(type);
    }

    /**
     *
     */
    protected ELArithmetic() {
        super();
    }

    protected abstract Number add(final Number num0, final Number num1);

    protected abstract Number multiply(final Number num0, final Number num1);

    protected abstract Number subtract(final Number num0, final Number num1);

    protected abstract Number mod(final Number num0, final Number num1);

    protected abstract Number coerce(final Number num);

    protected final Number coerce(final Object obj) {

        if (isNumber(obj)) {
            return coerce((Number) obj);
        }
        if (obj == null || "".equals(obj)) {
            return coerce(ZERO);
        }
        if (obj instanceof String) {
            return coerce((String) obj);
        }
        if (obj instanceof Character) {
            return coerce(Short.valueOf((short) ((Character) obj).charValue()));
        }

        throw new IllegalArgumentException(MessageFactory.get("error.convert",
                obj, obj.getClass(), "Number"));
    }

    protected abstract Number coerce(final String str);

    protected abstract Number divide(final Number num0, final Number num1);

    protected abstract boolean matches(final Object obj0, final Object obj1);

}