Assert.java

/*
 * Copyright 2024-2024 the original author or authors.
 */

package io.modelcontextprotocol.util;

import org.jspecify.annotations.Nullable;

import java.util.Collection;

/**
 * Assertion utility class that assists in validating arguments.
 *
 * @author Christian Tzolov
 */

/**
 * Utility class providing assertion methods for parameter validation.
 */
public final class Assert {

	/**
	 * Assert that the collection is not {@code null} and not empty.
	 * @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} or empty
	 */
	public static void notEmpty(@Nullable Collection<?> collection, String message) {
		if (collection == null || collection.isEmpty()) {
			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that an object is not {@code null}.
	 *
	 * <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}
	 */
	public static void notNull(@Nullable Object object, String message) {
		if (object == null) {
			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that the given String contains valid text content; that is, it must not be
	 * {@code null} 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
	 * @throws IllegalArgumentException if the text does not contain valid text content
	 */
	public static void hasText(@Nullable String text, String message) {
		if (!hasText(text)) {
			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Check whether the given {@code String} contains actual <em>text</em>.
	 * <p>
	 * More specifically, this method returns {@code true} if the {@code String} is not
	 * {@code null}, its length is greater than 0, and it contains at least one
	 * non-whitespace character.
	 * @param str the {@code String} to check (may be {@code null})
	 * @return {@code true} if the {@code String} is not {@code null}, its length is
	 * greater than 0, and it does not contain whitespace only
	 * @see Character#isWhitespace
	 */
	public static boolean hasText(@Nullable String str) {
		return (str != null && !str.isBlank());
	}

	/**
	 * Assert a boolean expression, throwing an {@code IllegalArgumentException} if the
	 * expression evaluates to {@code false}.
	 * @param expression a boolean expression
	 * @param message the exception message to use if the assertion fails
	 * @throws IllegalArgumentException if {@code expression} is {@code false}
	 */
	public static void isTrue(boolean expression, String message) {
		if (!expression) {
			throw new IllegalArgumentException(message);
		}
	}

}