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/*
 *
 * Copyright (c) 2006-2020, Speedment, Inc. All Rights Reserved.
 *
 * Licensed 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 com.speedment.runtime.compute;

import com.speedment.runtime.compute.expression.Expression;
import com.speedment.runtime.compute.expression.ExpressionType;
import com.speedment.runtime.compute.expression.Expressions;
import com.speedment.runtime.compute.internal.expression.ComposedUtil;
import com.speedment.runtime.compute.internal.expression.OrElseGetUtil;
import com.speedment.runtime.compute.internal.expression.OrElseThrowUtil;
import com.speedment.runtime.compute.internal.expression.OrElseUtil;
import com.speedment.runtime.compute.trait.HasAbs;
import com.speedment.runtime.compute.trait.HasCompare;
import com.speedment.runtime.compute.trait.HasCompose;
import com.speedment.runtime.compute.trait.HasHash;
import com.speedment.runtime.compute.trait.HasMapIfPresent;
import com.speedment.runtime.compute.trait.HasNegate;
import com.speedment.runtime.compute.trait.HasSign;
import com.speedment.runtime.compute.trait.HasSqrt;
import com.speedment.runtime.compute.trait.ToNullable;

import java.util.function.DoubleUnaryOperator;
import java.util.function.Function;
import java.util.function.ToDoubleFunction;

import static java.util.Objects.requireNonNull;

/**
 * Expression that given an entity returns a {@code double} value, or
 * {@code null}. This expression can be implemented using a lambda, or it can be
 * a result of another operation. It has additional methods for operating on it.
 *
 * @param  type to extract from
 *
 * @see Function
 *
 * @author Emil Forslund
 * @since  3.1.0
 */
@FunctionalInterface
public interface ToDoubleNullable
extends Expression,
        ToDoubleFunction,
        ToNullable>,
        HasAbs>,
        HasSign>,
        HasSqrt>,
        HasNegate>,
        HasMapIfPresent>,
        HasHash,
        HasCompare,
        HasCompose {

    /**
     * Returns a typed {@code ToDoubleNullable} using the provided
     * {@code lambda}.
     *
     * @param  type to extract from
     * @param lambda to convert
     * @return a typed {@code ToDoubleNullable} using the provided
     * {@code lambda}
     *
     * @throws NullPointerException if the provided {@code lambda} is
     * {@code null}
     */
    // Note that Function is not the same as ToDoubleFunction
    // since the former returns Double and the later double
    static  ToDoubleNullable of(Function lambda) {
        requireNonNull(lambda);
        if (lambda instanceof ToDoubleNullable) {
            return (ToDoubleNullable) lambda;
        } else {
            return lambda::apply;
        }
    }
    
    @Override
    default ExpressionType expressionType() {
        return ExpressionType.DOUBLE_NULLABLE;
    }

    @Override
    default double applyAsDouble(T object) {
        return apply(object);
    }

    @Override
    default ToDouble orThrow() {
        return OrElseThrowUtil.doubleOrElseThrow(this);
    }

    @Override
    default ToDouble orElseGet(ToDouble getter) {
        return OrElseGetUtil.doubleOrElseGet(this, getter);
    }

    @Override
    default ToDouble orElse(Double value) {
        return OrElseUtil.doubleOrElse(this, value);
    }

    @Override
    default ToDoubleNullable abs() {
        return Expressions.absOrNull(this);
    }

    @Override
    default ToDoubleNullable negate() {
        return Expressions.negateOrNull(this);
    }

    @Override
    default ToByteNullable sign() {
        return Expressions.signOrNull(this);
    }

    @Override
    default ToDoubleNullable sqrt() {
        return Expressions.sqrtOrNull(this);
    }

    @Override
    default ToDoubleNullable mapIfPresent(DoubleUnaryOperator operator) {
        final ToDoubleNullable delegate = this;
        return new ToDoubleNullable() {

            @Override
            public Double apply(T t) {
                return delegate.isNull(t)
                    ? null
                    : operator.applyAsDouble(delegate.applyAsDouble(t));
            }

            @Override
            public ToDouble orElseGet(ToDouble getter) {
                return t -> delegate.isNull(t)
                    ? getter.applyAsDouble(t)
                    : operator.applyAsDouble(delegate.applyAsDouble(t));
            }

            @Override
            public ToDouble orElse(Double value) {
                return t -> delegate.isNull(t) ? value
                    : operator.applyAsDouble(delegate.applyAsDouble(t));
            }

            @Override
            public boolean isNull(T object) {
                return delegate.isNull(object);
            }

            @Override
            public boolean isNotNull(T object) {
                return delegate.isNotNull(object);
            }

            @Override
            public ToDoubleNullable mapIfPresent(DoubleUnaryOperator nextOperator) {
                return delegate.mapIfPresent(operator.andThen(nextOperator));
            }
        };
    }

    @Override
    default long hash(T object) {
        if (isNull(object)) {
            return 0;
        } else {
            final long l = Double.doubleToLongBits(applyAsDouble(object));
            return (int) (l ^ (l >>> 32));
        }
    }

    @Override
    default int compare(T first, T second) {
        if (isNull(first)) {
            return isNull(second) ? 0 : 1;
        } else if (isNull(second)) {
            return -1;
        } else {
            return Double.compare(
                applyAsDouble(first),
                applyAsDouble(second)
            );
        }
    }

    @Override
    default  ToDoubleNullable compose(Function before) {
        @SuppressWarnings("unchecked")
        final Function casted = (Function) before;
        return ComposedUtil.composeToDoubleNullable(casted, this);
    }
}