/*
 * ============LICENSE_START=======================================================
 * Common Utils-Test
 * ================================================================================
 * Copyright (C) 2018 AT&T Intellectual Property. 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.
 * ============LICENSE_END=========================================================
 */

package org.onap.policy.common.utils.test;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertTrue;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Used to test various Throwable subclasses. Uses reflection to identify the
 * constructors that the subclass supports.
 */
public class ThrowablesTester {

	private static Logger logger = LoggerFactory.getLogger(ThrowablesTester.class);

	public static final String EXPECTED_EXCEPTION_MSG = "expected exception";
	private static final String EXPECTED_SUPPRESSED_EXCEPTION_MSG = "expected suppressed exception";

	/**
	 * Passed as a "cause" to constructors.
	 */
	public static final Exception CAUSE = new Exception(EXPECTED_EXCEPTION_MSG);

	/**
	 * Passed to new objects via the <i>addSuppressed()</i> method..
	 */
	public static final Throwable SUPPRESSED = new Throwable(EXPECTED_SUPPRESSED_EXCEPTION_MSG);

	/**
	 * Runs tests, on an Throwable subclass, for all of the standard
	 * constructors. If the Throwable subclass does not support a given type of
	 * constructor, then it skips that test. Does <i>not</i> throw an exception
	 * if no standard constructors are found.
	 * 
	 * @param claz
	 *            subclass to be tested
	 * @return the number of constructors that were found/tested
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> int testThrowable(Class<T> claz) {
		int ncons = 0;

		ncons += testThrowable_Default(claz);
		ncons += testThrowable_StringConstuctor(claz);
		ncons += testThrowable_Throwable(claz);
		ncons += testThrowable_StringThrowable(claz);
		ncons += testThrowable_StringThrowableBooleanBoolean(claz);

		return ncons;
	}

	/**
	 * Tests Throwable objects created via the default constructor. Verifies
	 * that:
	 * <ul>
	 * <li><i>toString()</i> returns a non-null value</li>
	 * <li><i>getMessage()</i> returns null</li>
	 * <li><i>getCause()</i> returns null</li>
	 * </ul>
	 * 
	 * If the Throwable subclass does not support this type of constructor, then
	 * this method simply returns.
	 * 
	 * @param claz
	 *            subclass to be tested
	 * @return {@code 1}, if the subclass supports this type of constructor,
	 *         {@code 0} otherwise
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> int testThrowable_Default(Class<T> claz) {
		Constructor<T> cons = getConstructor(claz, "default");
		if (cons == null) {
			return 0;
		}

		T ex = newInstance(cons);

		assertNotNull(ex.toString());
		assertNull(ex.getMessage());
		assertNull(ex.getCause());

		return 1;
	}

	/**
	 * Tests Throwable objects created via the constructor that takes just a
	 * String. Verifies that:
	 * <ul>
	 * <li><i>toString()</i> returns a non-null value</li>
	 * <li><i>getMessage()</i> returns the original message passed to the
	 * constructor</li>
	 * <li><i>getCause()</i> returns null</li>
	 * </ul>
	 * 
	 * If the Throwable subclass does not support this type of constructor, then
	 * this method simply returns.
	 * 
	 * @param claz
	 *            subclass to be tested
	 * @return {@code 1}, if the subclass supports this type of constructor,
	 *         {@code 0} otherwise
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> int testThrowable_StringConstuctor(Class<T> claz) {
		Constructor<T> cons = getConstructor(claz, "string", String.class);
		if (cons == null) {
			return 0;
		}

		T ex = newInstance(cons, "hello");

		assertNotNull(ex.toString());
		assertEquals("hello", ex.getMessage());
		assertNull(ex.getCause());

		return 1;
	}

	/**
	 * Tests Throwable objects created via the constructor that takes just a
	 * Throwable. Verifies that:
	 * <ul>
	 * <li><i>toString()</i> returns a non-null value</li>
	 * <li><i>getMessage()</i> returns the cause's message</li>
	 * <li><i>getCause()</i> returns the original cause passed to the
	 * constructor</li>
	 * </ul>
	 * 
	 * If the Throwable subclass does not support this type of constructor, then
	 * this method simply returns.
	 * 
	 * @param claz
	 *            subclass to be tested
	 * @return {@code 1}, if the subclass supports this type of constructor,
	 *         {@code 0} otherwise
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> int testThrowable_Throwable(Class<T> claz) {
		Constructor<T> cons = getConstructor(claz, "throwable", Throwable.class);
		if (cons == null) {
			return 0;
		}

		T ex = newInstance(cons, CAUSE);

		assertEquals(ex.getMessage(), ex.getMessage());
		assertNotNull(ex.toString());
		assertEquals(CAUSE, ex.getCause());

		return 1;
	}

	/**
	 * Tests Throwable objects created via the constructor that takes a String
	 * and a Throwable. Verifies that:
	 * <ul>
	 * <li><i>toString()</i> returns a non-null value</li>
	 * <li><i>getMessage()</i> returns the original message passed to the
	 * constructor</li>
	 * <li><i>getCause()</i> returns the original cause passed to the
	 * constructor</li>
	 * </ul>
	 * 
	 * If the Throwable subclass does not support this type of constructor, then
	 * this method simply returns.
	 * 
	 * @param claz
	 *            subclass to be tested
	 * @return {@code 1}, if the subclass supports this type of constructor,
	 *         {@code 0} otherwise
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> int testThrowable_StringThrowable(Class<T> claz) {
		Constructor<T> cons = getConstructor(claz, "string-throwable", String.class, Throwable.class);
		if (cons == null) {
			return 0;
		}

		T ex = newInstance(cons, "world", CAUSE);

		assertNotNull(ex.toString());
		assertEquals("world", ex.getMessage());
		assertEquals(CAUSE, ex.getCause());

		return 1;
	}

	/**
	 * Tests Throwable objects created via the constructor that takes a String,
	 * a Throwable, and two booleans. Verifies that:
	 * <ul>
	 * <li><i>toString()</i> returns a non-null value</li>
	 * <li><i>getMessage()</i> returns the original message passed to the
	 * constructor</li>
	 * <li><i>getCause()</i> returns the original cause passed to the
	 * constructor</li>
	 * <li>suppressed exceptions can be added, if enabled</li>
	 * <li>the stack trace can be added, if enabled</li>
	 * </ul>
	 * 
	 * If the Throwable subclass does not support this type of constructor, then
	 * this method simply returns.
	 * 
	 * @param claz
	 *            subclass to be tested
	 * @return {@code 1}, if the subclass supports this type of constructor,
	 *         {@code 0} otherwise
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> int testThrowable_StringThrowableBooleanBoolean(Class<T> claz) {
		Constructor<T> cons = getConstructor(claz, "string-throwable-flags", String.class, Throwable.class,
				Boolean.TYPE, Boolean.TYPE);
		if (cons == null) {
			return 0;
		}

		// test each combination of "message" and "cause"
		testThrowable_MessageCauseCombos(cons);

		// test each combination of the boolean flags
		testThrowable_SuppressStack(cons);
		testThrowable_SuppressNoStack(cons);
		testThrowable_NoSuppressStack(cons);
		testThrowable_NoSuppressNoStack(cons);

		return 1;
	}

	/**
	 * Tests each combination of values for the "message" and the "cause" when
	 * using the constructor that takes a String, a Throwable/Exception, and two
	 * booleans. Verifies that expected values are returned by <i>toString()/i>,
	 * <i>getMessage()</i>, and <i>getCause()</i>.
	 * </ul>
	 * 
	 * @param cons
	 *            constructor to be invoked
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> void testThrowable_MessageCauseCombos(Constructor<T> cons) {
		T ex;

		ex = newInstance(cons, null, null, true, true);
		assertNotNull(ex.toString());
		assertNull(ex.getMessage());
		assertNull(ex.getCause());

		ex = newInstance(cons, "abc", null, true, true);
		assertNotNull(ex.toString());
		assertEquals("abc", ex.getMessage());
		assertNull(ex.getCause());

		ex = newInstance(cons, null, CAUSE, true, true);
		assertNotNull(ex.toString());
		assertNull(ex.getMessage());
		assertEquals(CAUSE, ex.getCause());

		ex = newInstance(cons, "xyz", CAUSE, true, true);
		assertNotNull(ex.toString());
		assertEquals("xyz", ex.getMessage());
		assertEquals(CAUSE, ex.getCause());
	}

	/**
	 * Tests each combination of values for the "message" and the "cause" when
	 * using the constructor that takes a String, a Throwable/Exception, and two
	 * booleans. Verifies that expected values are returned by <i>toString()/i>,
	 * <i>getMessage()</i>, and <i>getCause()</i>.
	 * </ul>
	 * 
	 * @param cons
	 *            constructor to be invoked
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> void testThrowable_FlagCombos(Constructor<T> cons) {
		testThrowable_SuppressStack(cons);
		testThrowable_SuppressNoStack(cons);
		testThrowable_NoSuppressStack(cons);
		testThrowable_NoSuppressNoStack(cons);
	}

	/**
	 * Tests Throwable objects constructed with {@code enableSuppression=true}
	 * and {@code writableStackTrace=true}. Verifies that:
	 * <ul>
	 * <li><i>toString()</i> returns a non-null value</li>
	 * <li><i>getMessage()</i> returns the original message passed to the
	 * constructor</li>
	 * <li><i>getCause()</i> returns the original cause passed to the
	 * constructor</li>
	 * <li>suppressed exceptions are added</li>
	 * <li>the stack trace is added</li>
	 * </ul>
	 * 
	 * @param cons
	 *            the throwable's class constructor
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> void testThrowable_SuppressStack(Constructor<T> cons) {
		T ex = newInstance(cons, "yes,yes", CAUSE, true, true);

		ex.addSuppressed(SUPPRESSED);

		assertNotNull(ex.toString());
		assertEquals("yes,yes", ex.getMessage());
		assertEquals(CAUSE, ex.getCause());

		assertEquals(1, ex.getSuppressed().length);
		assertEquals(SUPPRESSED, ex.getSuppressed()[0]);

		assertTrue(ex.getStackTrace().length > 0);
	}

	/**
	 * Tests Throwable objects constructed with {@code enableSuppression=true}
	 * and {@code writableStackTrace=false}. Verifies that:
	 * <ul>
	 * <li><i>toString()</i> returns a non-null value</li>
	 * <li><i>getMessage()</i> returns the original message passed to the
	 * constructor</li>
	 * <li><i>getCause()</i> returns the original cause passed to the
	 * constructor</li>
	 * <li>suppressed exceptions are added</li>
	 * <li>the stack trace is <i>not</i> added</li>
	 * </ul>
	 * 
	 * @param cons
	 *            the throwable's class constructor
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> void testThrowable_SuppressNoStack(Constructor<T> cons) {
		T ex = newInstance(cons, "yes,no", CAUSE, true, false);

		ex.addSuppressed(SUPPRESSED);

		assertNotNull(ex.toString());
		assertEquals("yes,no", ex.getMessage());
		assertEquals(CAUSE, ex.getCause());

		assertEquals(1, ex.getSuppressed().length);
		assertEquals(SUPPRESSED, ex.getSuppressed()[0]);

		assertEquals(0, ex.getStackTrace().length);
	}

	/**
	 * Tests Throwable objects constructed with {@code enableSuppression=false}
	 * and {@code writableStackTrace=true}. Verifies that:
	 * <ul>
	 * <li><i>toString()</i> returns a non-null value</li>
	 * <li><i>getMessage()</i> returns the original message passed to the
	 * constructor</li>
	 * <li><i>getCause()</i> returns the original cause passed to the
	 * constructor</li>
	 * <li>suppressed exceptions are <i>not</i> added</li>
	 * <li>the stack trace is added</li>
	 * </ul>
	 * 
	 * @param cons
	 *            the throwable's class constructor
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> void testThrowable_NoSuppressStack(Constructor<T> cons) {
		T ex = newInstance(cons, "no,yes", CAUSE, false, true);

		ex.addSuppressed(SUPPRESSED);

		assertNotNull(ex.toString());
		assertEquals("no,yes", ex.getMessage());
		assertEquals(CAUSE, ex.getCause());

		assertEquals(0, ex.getSuppressed().length);

		assertTrue(ex.getStackTrace().length > 0);
	}

	/**
	 * Tests Throwable objects constructed with {@code enableSuppression=false}
	 * and {@code writableStackTrace=false}. Verifies that:
	 * <ul>
	 * <li><i>toString()</i> returns a non-null value</li>
	 * <li><i>getMessage()</i> returns the original message passed to the
	 * constructor</li>
	 * <li><i>getCause()</i> returns the original cause passed to the
	 * constructor</li>
	 * <li>suppressed exceptions are <i>not</i> added</li>
	 * <li>the stack trace is <i>not</i> added</li>
	 * 
	 * @param cons
	 *            the throwable's class constructor
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 * @throws AssertionError
	 *             if the constructed objects fail to pass various tests
	 */
	public <T extends Throwable> void testThrowable_NoSuppressNoStack(Constructor<T> cons) {
		T ex = newInstance(cons, "no,no", CAUSE, false, false);

		ex.addSuppressed(SUPPRESSED);

		assertNotNull(ex.toString());
		assertEquals("no,no", ex.getMessage());
		assertEquals(CAUSE, ex.getCause());

		assertEquals(0, ex.getSuppressed().length);
		assertEquals(0, ex.getStackTrace().length);
	}

	/**
	 * Attempts to get a constructor for objects of a given type.
	 * 
	 * @param claz
	 *            class of objects whose constructor is to be gotten
	 * @param testType
	 *            type of test being run
	 * @param argTypes
	 *            argument types to be passed to the constructor
	 * @return the desired constructor, or {@code null} if the desired
	 *         constructor is not available
	 */
	protected <T extends Throwable> Constructor<T> getConstructor(Class<T> claz, String testType,
			Class<?>... argTypes) {

		try {
			return claz.getConstructor(argTypes);

		} catch (NoSuchMethodException | SecurityException e) {
			// this constructor is not defined so nothing to test
			logger.debug("skipped test, no constructor for: " + claz + " due to: " + e);
			return null;
		}
	}

	/**
	 * Creates a new instance of an Throwable subclass.
	 * 
	 * @param cons
	 *            subclass constructor
	 * @param args
	 *            arguments to be passed to the constructor
	 * @return a new instance of the Throwable subclass
	 * @throws ConstructionError
	 *             if the Throwable subclass cannot be constructed
	 */
	protected <T extends Throwable> T newInstance(Constructor<T> cons, Object... args) {
		try {
			return cons.newInstance(args);

		} catch (InstantiationException | IllegalAccessException | IllegalArgumentException
				| InvocationTargetException e) {

			throw new ConstructionError(e);
		}

	}
}