/*
 * 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.shiro.util;

import java.util.Collection;
import java.util.Map;

/**
 * Assertion utility class that assists in validating arguments.
 * Useful for identifying programmer errors early and clearly at runtime.
 * Usage also reduces a program's
 * <a href="http://en.wikipedia.org/wiki/Cyclomatic_complexity">cyclomatic complexity</a>.
 *
 * <p>For example, if the contract of a public method states it does not
 * allow <code>null</code> arguments, Assert can be used to validate that
 * contract. Doing this clearly indicates a contract violation when it
 * occurs and protects the class's invariants.
 *
 * <p>Typically used to validate method arguments rather than configuration
 * properties, to check for cases that are usually programmer errors rather than
 * configuration errors. In contrast to config initialization code, there is
 * usally no point in falling back to defaults in such methods.
 *
 * <p>This class is similar to JUnit's assertion library. If an argument value is
 * deemed invalid, an {@link IllegalArgumentException} is thrown (typically).
 * For example:
 *
 * <pre class="code">
 * Assert.notNull(clazz, "The class must not be null");
 * Assert.isTrue(i > 0, "The value must be greater than zero");</pre>
 *
 * Mainly for internal use within the framework; consider Jakarta's Commons Lang
 * >= 2.0 for a more comprehensive suite of assertion utilities.
 * <p/>
 * <em>Gratefully borrowed from the Spring Framework, also Apache 2.0 licensed</em>
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @author Colin Sampaleanu
 * @author Rob Harrop
 * @since 1.3
 */
public abstract class Assert {

    /**
     * Assert a boolean expression, throwing <code>IllegalArgumentException</code>
     * if the test result is <code>false</code>.
     * <pre class="code">Assert.isTrue(i &gt; 0, "The value must be greater than zero");</pre>
     * @param expression a boolean expression
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if expression is <code>false</code>
     */
    public static void isTrue(boolean expression, String message) {
        if (!expression) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert a boolean expression, throwing <code>IllegalArgumentException</code>
     * if the test result is <code>false</code>.
     * <pre class="code">Assert.isTrue(i &gt; 0);</pre>
     * @param expression a boolean expression
     * @throws IllegalArgumentException if expression is <code>false</code>
     */
    public static void isTrue(boolean expression) {
        isTrue(expression, "[Assertion failed] - this expression must be true");
    }

    /**
     * Assert that an object is <code>null</code> .
     * <pre class="code">Assert.isNull(value, "The value must be null");</pre>
     * @param object the object to check
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if the object is not <code>null</code>
     */
    public static void isNull(Object object, String message) {
        if (object != null) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that an object is <code>null</code> .
     * <pre class="code">Assert.isNull(value);</pre>
     * @param object the object to check
     * @throws IllegalArgumentException if the object is not <code>null</code>
     */
    public static void isNull(Object object) {
        isNull(object, "[Assertion failed] - the object argument must be null");
    }

    /**
     * Assert that an object is not <code>null</code> .
     * <pre class="code">Assert.notNull(clazz, "The class must not be null");</pre>
     * @param object the object to check
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if the object is <code>null</code>
     */
    public static void notNull(Object object, String message) {
        if (object == null) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that an object is not <code>null</code> .
     * <pre class="code">Assert.notNull(clazz);</pre>
     * @param object the object to check
     * @throws IllegalArgumentException if the object is <code>null</code>
     */
    public static void notNull(Object object) {
        notNull(object, "[Assertion failed] - this argument is required; it must not be null");
    }

    /**
     * Assert that the given String is not empty; that is,
     * it must not be <code>null</code> and not the empty String.
     * <pre class="code">Assert.hasLength(name, "Name must not be empty");</pre>
     * @param text the String to check
     * @param message the exception message to use if the assertion fails
     * @see StringUtils#hasLength
     */
    public static void hasLength(String text, String message) {
        if (!StringUtils.hasLength(text)) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that the given String is not empty; that is,
     * it must not be <code>null</code> and not the empty String.
     * <pre class="code">Assert.hasLength(name);</pre>
     * @param text the String to check
     * @see StringUtils#hasLength
     */
    public static void hasLength(String text) {
        hasLength(text,
                "[Assertion failed] - this String argument must have length; it must not be null or empty");
    }

    /**
     * Assert that the given String has valid text content; that is, it must not
     * be <code>null</code> and must contain at least one non-whitespace character.
     * <pre class="code">Assert.hasText(name, "'name' must not be empty");</pre>
     * @param text the String to check
     * @param message the exception message to use if the assertion fails
     * @see StringUtils#hasText
     */
    public static void hasText(String text, String message) {
        if (!StringUtils.hasText(text)) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that the given String has valid text content; that is, it must not
     * be <code>null</code> and must contain at least one non-whitespace character.
     * <pre class="code">Assert.hasText(name, "'name' must not be empty");</pre>
     * @param text the String to check
     * @see StringUtils#hasText
     */
    public static void hasText(String text) {
        hasText(text,
                "[Assertion failed] - this String argument must have text; it must not be null, empty, or blank");
    }

    /**
     * Assert that the given text does not contain the given substring.
     * <pre class="code">Assert.doesNotContain(name, "rod", "Name must not contain 'rod'");</pre>
     * @param textToSearch the text to search
     * @param substring the substring to find within the text
     * @param message the exception message to use if the assertion fails
     */
    public static void doesNotContain(String textToSearch, String substring, String message) {
        if (StringUtils.hasLength(textToSearch) && StringUtils.hasLength(substring) &&
                textToSearch.indexOf(substring) != -1) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that the given text does not contain the given substring.
     * <pre class="code">Assert.doesNotContain(name, "rod");</pre>
     * @param textToSearch the text to search
     * @param substring the substring to find within the text
     */
    public static void doesNotContain(String textToSearch, String substring) {
        doesNotContain(textToSearch, substring,
                "[Assertion failed] - this String argument must not contain the substring [" + substring + "]");
    }


    /**
     * Assert that an array has elements; that is, it must not be
     * <code>null</code> and must have at least one element.
     * <pre class="code">Assert.notEmpty(array, "The array must have elements");</pre>
     * @param array the array to check
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if the object array is <code>null</code> or has no elements
     */
    public static void notEmpty(Object[] array, String message) {
        if (array == null || array.length == 0) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that an array has elements; that is, it must not be
     * <code>null</code> and must have at least one element.
     * <pre class="code">Assert.notEmpty(array);</pre>
     * @param array the array to check
     * @throws IllegalArgumentException if the object array is <code>null</code> or has no elements
     */
    public static void notEmpty(Object[] array) {
        notEmpty(array, "[Assertion failed] - this array must not be empty: it must contain at least 1 element");
    }

    /**
     * Assert that an array has no null elements.
     * Note: Does not complain if the array is empty!
     * <pre class="code">Assert.noNullElements(array, "The array must have non-null elements");</pre>
     * @param array the array to check
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if the object array contains a <code>null</code> element
     */
    public static void noNullElements(Object[] array, String message) {
        if (array != null) {
            for (int i = 0; i < array.length; i++) {
                if (array[i] == null) {
                    throw new IllegalArgumentException(message);
                }
            }
        }
    }

    /**
     * Assert that an array has no null elements.
     * Note: Does not complain if the array is empty!
     * <pre class="code">Assert.noNullElements(array);</pre>
     * @param array the array to check
     * @throws IllegalArgumentException if the object array contains a <code>null</code> element
     */
    public static void noNullElements(Object[] array) {
        noNullElements(array, "[Assertion failed] - this array must not contain any null elements");
    }

    /**
     * Assert that a collection has elements; that is, it must not be
     * <code>null</code> and must have at least one element.
     * <pre class="code">Assert.notEmpty(collection, "Collection must have elements");</pre>
     * @param collection the collection to check
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if the collection is <code>null</code> or has no elements
     */
    public static void notEmpty(Collection collection, String message) {
        if (CollectionUtils.isEmpty(collection)) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that a collection has elements; that is, it must not be
     * <code>null</code> and must have at least one element.
     * <pre class="code">Assert.notEmpty(collection, "Collection must have elements");</pre>
     * @param collection the collection to check
     * @throws IllegalArgumentException if the collection is <code>null</code> or has no elements
     */
    public static void notEmpty(Collection collection) {
        notEmpty(collection,
                "[Assertion failed] - this collection must not be empty: it must contain at least 1 element");
    }

    /**
     * Assert that a Map has entries; that is, it must not be <code>null</code>
     * and must have at least one entry.
     * <pre class="code">Assert.notEmpty(map, "Map must have entries");</pre>
     * @param map the map to check
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if the map is <code>null</code> or has no entries
     */
    public static void notEmpty(Map map, String message) {
        if (CollectionUtils.isEmpty(map)) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that a Map has entries; that is, it must not be <code>null</code>
     * and must have at least one entry.
     * <pre class="code">Assert.notEmpty(map);</pre>
     * @param map the map to check
     * @throws IllegalArgumentException if the map is <code>null</code> or has no entries
     */
    public static void notEmpty(Map map) {
        notEmpty(map, "[Assertion failed] - this map must not be empty; it must contain at least one entry");
    }


    /**
     * Assert that the provided object is an instance of the provided class.
     * <pre class="code">Assert.instanceOf(Foo.class, foo);</pre>
     * @param clazz the required class
     * @param obj the object to check
     * @throws IllegalArgumentException if the object is not an instance of clazz
     * @see Class#isInstance
     */
    public static void isInstanceOf(Class clazz, Object obj) {
        isInstanceOf(clazz, obj, "");
    }

    /**
     * Assert that the provided object is an instance of the provided class.
     * <pre class="code">Assert.instanceOf(Foo.class, foo);</pre>
     * @param type the type to check against
     * @param obj the object to check
     * @param message a message which will be prepended to the message produced by
     * the function itself, and which may be used to provide context. It should
     * normally end in a ": " or ". " so that the function generate message looks
     * ok when prepended to it.
     * @throws IllegalArgumentException if the object is not an instance of clazz
     * @see Class#isInstance
     */
    public static void isInstanceOf(Class type, Object obj, String message) {
        notNull(type, "Type to check against must not be null");
        if (!type.isInstance(obj)) {
            throw new IllegalArgumentException(message +
                    "Object of class [" + (obj != null ? obj.getClass().getName() : "null") +
                    "] must be an instance of " + type);
        }
    }

    /**
     * Assert that <code>superType.isAssignableFrom(subType)</code> is <code>true</code>.
     * <pre class="code">Assert.isAssignable(Number.class, myClass);</pre>
     * @param superType the super type to check
     * @param subType the sub type to check
     * @throws IllegalArgumentException if the classes are not assignable
     */
    public static void isAssignable(Class superType, Class subType) {
        isAssignable(superType, subType, "");
    }

    /**
     * Assert that <code>superType.isAssignableFrom(subType)</code> is <code>true</code>.
     * <pre class="code">Assert.isAssignable(Number.class, myClass);</pre>
     * @param superType the super type to check against
     * @param subType the sub type to check
     * @param message a message which will be prepended to the message produced by
     * the function itself, and which may be used to provide context. It should
     * normally end in a ": " or ". " so that the function generate message looks
     * ok when prepended to it.
     * @throws IllegalArgumentException if the classes are not assignable
     */
    public static void isAssignable(Class superType, Class subType, String message) {
        notNull(superType, "Type to check against must not be null");
        if (subType == null || !superType.isAssignableFrom(subType)) {
            throw new IllegalArgumentException(message + subType + " is not assignable to " + superType);
        }
    }


    /**
     * Assert a boolean expression, throwing <code>IllegalStateException</code>
     * if the test result is <code>false</code>. Call isTrue if you wish to
     * throw IllegalArgumentException on an assertion failure.
     * <pre class="code">Assert.state(id == null, "The id property must not already be initialized");</pre>
     * @param expression a boolean expression
     * @param message the exception message to use if the assertion fails
     * @throws IllegalStateException if expression is <code>false</code>
     */
    public static void state(boolean expression, String message) {
        if (!expression) {
            throw new IllegalStateException(message);
        }
    }

    /**
     * Assert a boolean expression, throwing {@link IllegalStateException}
     * if the test result is <code>false</code>.
     * <p>Call {@link #isTrue(boolean)} if you wish to
     * throw {@link IllegalArgumentException} on an assertion failure.
     * <pre class="code">Assert.state(id == null);</pre>
     * @param expression a boolean expression
     * @throws IllegalStateException if the supplied expression is <code>false</code>
     */
    public static void state(boolean expression) {
        state(expression, "[Assertion failed] - this state invariant must be true");
    }

}
