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The MongoDB Java Driver uber-artifact, containing mongodb-driver, mongodb-driver-core, and bson
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/*
 * Copyright 2008-present MongoDB, Inc.
 * Copyright (c) 2008-2014 Atlassian Pty Ltd
 *
 * 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 org.bson.assertions;

/**
 * Design by contract assertions.
 This class is not part of the public API and may be removed or changed at any time.
 */
public final class Assertions {
    /**
     * Throw IllegalArgumentException if the value is null.
     *
     * @param name  the parameter name
     * @param value the value that should not be null
     * @param    the value type
     * @return the value
     * @throws IllegalArgumentException if value is null
     */
    public static  T notNull(final String name, final T value) {
        if (value == null) {
            throw new IllegalArgumentException(name + " can not be null");
        }
        return value;
    }

    /**
     * Throw IllegalStateException if the condition if false.
     *
     * @param name      the name of the state that is being checked
     * @param condition the condition about the parameter to check
     * @throws IllegalStateException if the condition is false
     */
    public static void isTrue(final String name, final boolean condition) {
        if (!condition) {
            throw new IllegalStateException("state should be: " + name);
        }
    }

    /**
     * Throw IllegalArgumentException if the condition if false.
     *
     * @param name      the name of the state that is being checked
     * @param condition the condition about the parameter to check
     * @throws IllegalArgumentException if the condition is false
     */
    public static void isTrueArgument(final String name, final boolean condition) {
        if (!condition) {
            throw new IllegalArgumentException("state should be: " + name);
        }
    }

    /**
     * Throw IllegalArgumentException if the condition if false, otherwise return the value.  This is useful when arguments must be checked
     * within an expression, as when using {@code this} to call another constructor, which must be the first line of the calling
     * constructor.
     *
     * @param        the value type
     * @param name      the name of the state that is being checked
     * @param value     the value of the argument
     * @param condition the condition about the parameter to check
     * @return          the value
     * @throws java.lang.IllegalArgumentException if the condition is false
     */
    public static  T isTrueArgument(final String name, final T value, final boolean condition) {
        if (!condition) {
            throw new IllegalArgumentException("state should be: " + name);
        }
        return value;
    }

    /**
     * Cast an object to the given class and return it, or throw IllegalArgumentException if it's not assignable to that class.
     *
     * @param clazz        the class to cast to
     * @param value        the value to cast
     * @param errorMessage the error message to include in the exception
     * @param           the Class type
     * @return value cast to clazz
     * @throws IllegalArgumentException if value is not assignable to clazz
     */
    @SuppressWarnings("unchecked")
    public static  T convertToType(final Class clazz, final Object value, final String errorMessage) {
        if (!clazz.isAssignableFrom(value.getClass())) {
            throw new IllegalArgumentException(errorMessage);
        }
        return (T) value;
    }

    private Assertions() {
    }
}