package org.junit.runners;

import static org.junit.internal.runners.rules.RuleMemberValidator.RULE_METHOD_VALIDATOR;
import static org.junit.internal.runners.rules.RuleMemberValidator.RULE_VALIDATOR;

import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;

import org.junit.After;
import org.junit.Before;
import org.junit.Ignore;
import org.junit.Rule;
import org.junit.Test;
import org.junit.Test.None;
import org.junit.internal.runners.model.ReflectiveCallable;
import org.junit.internal.runners.statements.ExpectException;
import org.junit.internal.runners.statements.Fail;
import org.junit.internal.runners.statements.FailOnTimeout;
import org.junit.internal.runners.statements.InvokeMethod;
import org.junit.internal.runners.statements.RunAfters;
import org.junit.internal.runners.statements.RunBefores;
import org.junit.rules.MethodRule;
import org.junit.rules.RunRules;
import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runner.notification.RunNotifier;
import org.junit.runners.model.FrameworkMethod;
import org.junit.runners.model.InitializationError;
import org.junit.runners.model.MultipleFailureException;
import org.junit.runners.model.Statement;

Implements the JUnit 4 standard test case class model, as defined by the annotations in the org.junit package. Many users will never notice this class: it is now the default test class runner, but it should have exactly the same behavior as the old test class runner (JUnit4ClassRunner). 

BlockJUnit4ClassRunner has advantages for writers of custom JUnit runners
that are slight changes to the default behavior, however:

It has a much simpler implementation based on Statements, allowing new operations to be inserted into the appropriate point in the execution flow. 
It is published, and extension and reuse are encouraged, whereas 
JUnit4ClassRunner was in an internal package, and is now deprecated. 
 In turn, in 2009 we introduced Rules. In many cases where extending BlockJUnit4ClassRunner was necessary to add new behavior, Rules can be used, which makes the extension more reusable and composable. 
Since:
4.5/**
 * Implements the JUnit 4 standard test case class model, as defined by the
 * annotations in the org.junit package. Many users will never notice this
 * class: it is now the default test class runner, but it should have exactly
 * the same behavior as the old test class runner ({@code JUnit4ClassRunner}).
 * <p>
 * BlockJUnit4ClassRunner has advantages for writers of custom JUnit runners
 * that are slight changes to the default behavior, however:
 *
 * <ul>
 * <li>It has a much simpler implementation based on {@link Statement}s,
 * allowing new operations to be inserted into the appropriate point in the
 * execution flow.
 *
 * <li>It is published, and extension and reuse are encouraged, whereas {@code
 * JUnit4ClassRunner} was in an internal package, and is now deprecated.
 * </ul>
 * <p>
 * In turn, in 2009 we introduced {@link Rule}s.  In many cases where extending
 * BlockJUnit4ClassRunner was necessary to add new behavior, {@link Rule}s can
 * be used, which makes the extension more reusable and composable.
 *
 * @since 4.5
 */
public class BlockJUnit4ClassRunner extends ParentRunner<FrameworkMethod> {
    private final ConcurrentHashMap<FrameworkMethod, Description> methodDescriptions = new ConcurrentHashMap<FrameworkMethod, Description>();
    
Creates a BlockJUnit4ClassRunner to run klass 
Throws:
InitializationError – if the test class is malformed./**
     * Creates a BlockJUnit4ClassRunner to run {@code klass}
     *
     * @throws InitializationError if the test class is malformed.
     */
    public BlockJUnit4ClassRunner(Class<?> klass) throws InitializationError {
        super(klass);
    }

    //
    // Implementation of ParentRunner
    //

    @Override
    protected void runChild(final FrameworkMethod method, RunNotifier notifier) {
        Description description = describeChild(method);
        if (isIgnored(method)) {
            notifier.fireTestIgnored(description);
        } else {
            runLeaf(methodBlock(method), description, notifier);
        }
    }
    
    
Evaluates whether FrameworkMethods are ignored based on the Ignore annotation. /**
     * Evaluates whether {@link FrameworkMethod}s are ignored based on the
     * {@link Ignore} annotation.
     */
    @Override
    protected boolean isIgnored(FrameworkMethod child) {
        return child.getAnnotation(Ignore.class) != null;
    }

    @Override
    protected Description describeChild(FrameworkMethod method) {
        Description description = methodDescriptions.get(method);

        if (description == null) {
            description = Description.createTestDescription(getTestClass().getJavaClass(),
                    testName(method), method.getAnnotations());
            methodDescriptions.putIfAbsent(method, description);
        }

        return description;
    }

    @Override
    protected List<FrameworkMethod> getChildren() {
        return computeTestMethods();
    }

    //
    // Override in subclasses
    //

    
Returns the methods that run tests. Default implementation returns all methods annotated with @Test on this class and superclasses that are not overridden. /**
     * Returns the methods that run tests. Default implementation returns all
     * methods annotated with {@code @Test} on this class and superclasses that
     * are not overridden.
     */
    protected List<FrameworkMethod> computeTestMethods() {
        return getTestClass().getAnnotatedMethods(Test.class);
    }

    @Override
    protected void collectInitializationErrors(List<Throwable> errors) {
        super.collectInitializationErrors(errors);

        validateNoNonStaticInnerClass(errors);
        validateConstructor(errors);
        validateInstanceMethods(errors);
        validateFields(errors);
        validateMethods(errors);
    }

    protected void validateNoNonStaticInnerClass(List<Throwable> errors) {
        if (getTestClass().isANonStaticInnerClass()) {
            String gripe = "The inner class " + getTestClass().getName()
                    + " is not static.";
            errors.add(new Exception(gripe));
        }
    }

    
Adds to errors if the test class has more than one constructor, or if the constructor takes parameters. Override if a subclass requires different validation rules. /**
     * Adds to {@code errors} if the test class has more than one constructor,
     * or if the constructor takes parameters. Override if a subclass requires
     * different validation rules.
     */
    protected void validateConstructor(List<Throwable> errors) {
        validateOnlyOneConstructor(errors);
        validateZeroArgConstructor(errors);
    }

    
Adds to errors if the test class has more than one constructor (do not override) /**
     * Adds to {@code errors} if the test class has more than one constructor
     * (do not override)
     */
    protected void validateOnlyOneConstructor(List<Throwable> errors) {
        if (!hasOneConstructor()) {
            String gripe = "Test class should have exactly one public constructor";
            errors.add(new Exception(gripe));
        }
    }

    
Adds to errors if the test class's single constructor takes parameters (do not override) /**
     * Adds to {@code errors} if the test class's single constructor takes
     * parameters (do not override)
     */
    protected void validateZeroArgConstructor(List<Throwable> errors) {
        if (!getTestClass().isANonStaticInnerClass()
                && hasOneConstructor()
                && (getTestClass().getOnlyConstructor().getParameterTypes().length != 0)) {
            String gripe = "Test class should have exactly one public zero-argument constructor";
            errors.add(new Exception(gripe));
        }
    }

    private boolean hasOneConstructor() {
        return getTestClass().getJavaClass().getConstructors().length == 1;
    }

    
Adds to errors for each method annotated with @Test, @Before, or @After that is not a public, void instance method with no arguments. /**
     * Adds to {@code errors} for each method annotated with {@code @Test},
     * {@code @Before}, or {@code @After} that is not a public, void instance
     * method with no arguments.
     */
    @Deprecated
    protected void validateInstanceMethods(List<Throwable> errors) {
        validatePublicVoidNoArgMethods(After.class, false, errors);
        validatePublicVoidNoArgMethods(Before.class, false, errors);
        validateTestMethods(errors);

        if (computeTestMethods().size() == 0) {
            errors.add(new Exception("No runnable methods"));
        }
    }

    protected void validateFields(List<Throwable> errors) {
        RULE_VALIDATOR.validate(getTestClass(), errors);
    }

    private void validateMethods(List<Throwable> errors) {
        RULE_METHOD_VALIDATOR.validate(getTestClass(), errors);
    }

    
Adds to errors for each method annotated with @Testthat is not a public, void instance method with no arguments. /**
     * Adds to {@code errors} for each method annotated with {@code @Test}that
     * is not a public, void instance method with no arguments.
     */
    protected void validateTestMethods(List<Throwable> errors) {
        validatePublicVoidNoArgMethods(Test.class, false, errors);
    }

    
Returns a new fixture for running a test. Default implementation executes
the test class's no-argument constructor (validation should have ensured
one exists).
/**
     * Returns a new fixture for running a test. Default implementation executes
     * the test class's no-argument constructor (validation should have ensured
     * one exists).
     */
    protected Object createTest() throws Exception {
        return getTestClass().getOnlyConstructor().newInstance();
    }

    
Returns the name that describes method for Descriptions. Default implementation is the method's name /**
     * Returns the name that describes {@code method} for {@link Description}s.
     * Default implementation is the method's name
     */
    protected String testName(FrameworkMethod method) {
        return method.getName();
    }

    
Returns a Statement that, when executed, either returns normally if method passes, or throws an exception if method fails. Here is an outline of the default implementation: 

Invoke method on the result of createTest(), and throw any exceptions thrown by either operation. 
HOWEVER, if method's @Test annotation has the 
expecting attribute, return normally only if the previous step threw an exception of the correct type, and throw an exception otherwise. 
HOWEVER, if method's @Test annotation has the 
timeout attribute, throw an exception if the previous step takes more than the specified number of milliseconds. 
ALWAYS run all non-overridden @Before methods on this class and superclasses before any of the previous steps; if any throws an Exception, stop execution and pass the exception on. 
ALWAYS run all non-overridden @After methods on this class and superclasses after any of the previous steps; all After methods are always executed: exceptions thrown by previous steps are combined, if necessary, with exceptions from After methods into a MultipleFailureException. 
ALWAYS allow @Rule fields to modify the execution of the above steps. A Rule may prevent all execution of the above steps, or add additional behavior before and after, or modify thrown exceptions. For more information, see TestRule 
This can be overridden in subclasses, either by overriding this method,
or the implementations creating each sub-statement.
/**
     * Returns a Statement that, when executed, either returns normally if
     * {@code method} passes, or throws an exception if {@code method} fails.
     *
     * Here is an outline of the default implementation:
     *
     * <ul>
     * <li>Invoke {@code method} on the result of {@code createTest()}, and
     * throw any exceptions thrown by either operation.
     * <li>HOWEVER, if {@code method}'s {@code @Test} annotation has the {@code
     * expecting} attribute, return normally only if the previous step threw an
     * exception of the correct type, and throw an exception otherwise.
     * <li>HOWEVER, if {@code method}'s {@code @Test} annotation has the {@code
     * timeout} attribute, throw an exception if the previous step takes more
     * than the specified number of milliseconds.
     * <li>ALWAYS run all non-overridden {@code @Before} methods on this class
     * and superclasses before any of the previous steps; if any throws an
     * Exception, stop execution and pass the exception on.
     * <li>ALWAYS run all non-overridden {@code @After} methods on this class
     * and superclasses after any of the previous steps; all After methods are
     * always executed: exceptions thrown by previous steps are combined, if
     * necessary, with exceptions from After methods into a
     * {@link MultipleFailureException}.
     * <li>ALWAYS allow {@code @Rule} fields to modify the execution of the
     * above steps. A {@code Rule} may prevent all execution of the above steps,
     * or add additional behavior before and after, or modify thrown exceptions.
     * For more information, see {@link TestRule}
     * </ul>
     *
     * This can be overridden in subclasses, either by overriding this method,
     * or the implementations creating each sub-statement.
     */
    protected Statement methodBlock(FrameworkMethod method) {
        Object test;
        try {
            test = new ReflectiveCallable() {
                @Override
                protected Object runReflectiveCall() throws Throwable {
                    return createTest();
                }
            }.run();
        } catch (Throwable e) {
            return new Fail(e);
        }

        Statement statement = methodInvoker(method, test);
        statement = possiblyExpectingExceptions(method, test, statement);
        statement = withPotentialTimeout(method, test, statement);
        statement = withBefores(method, test, statement);
        statement = withAfters(method, test, statement);
        statement = withRules(method, test, statement);
        return statement;
    }

    //
    // Statement builders
    //

    
Returns a Statement that invokes method on test /**
     * Returns a {@link Statement} that invokes {@code method} on {@code test}
     */
    protected Statement methodInvoker(FrameworkMethod method, Object test) {
        return new InvokeMethod(method, test);
    }

    
Returns a Statement: if method's @Test annotation has the expecting attribute, return normally only if next throws an exception of the correct type, and throw an exception otherwise. /**
     * Returns a {@link Statement}: if {@code method}'s {@code @Test} annotation
     * has the {@code expecting} attribute, return normally only if {@code next}
     * throws an exception of the correct type, and throw an exception
     * otherwise.
     */
    protected Statement possiblyExpectingExceptions(FrameworkMethod method,
            Object test, Statement next) {
        Test annotation = method.getAnnotation(Test.class);
        return expectsException(annotation) ? new ExpectException(next,
                getExpectedException(annotation)) : next;
    }

    
Returns a Statement: if method's @Test annotation has the timeout attribute, throw an exception if next takes more than the specified number of milliseconds. /**
     * Returns a {@link Statement}: if {@code method}'s {@code @Test} annotation
     * has the {@code timeout} attribute, throw an exception if {@code next}
     * takes more than the specified number of milliseconds.
     */
    @Deprecated
    protected Statement withPotentialTimeout(FrameworkMethod method,
            Object test, Statement next) {
        long timeout = getTimeout(method.getAnnotation(Test.class));
        if (timeout <= 0) {
            return next;
        }
        return FailOnTimeout.builder()
               .withTimeout(timeout, TimeUnit.MILLISECONDS)
               .build(next);
    }

    
Returns a Statement: run all non-overridden @Before methods on this class and superclasses before running next; if any throws an Exception, stop execution and pass the exception on. /**
     * Returns a {@link Statement}: run all non-overridden {@code @Before}
     * methods on this class and superclasses before running {@code next}; if
     * any throws an Exception, stop execution and pass the exception on.
     */
    protected Statement withBefores(FrameworkMethod method, Object target,
            Statement statement) {
        List<FrameworkMethod> befores = getTestClass().getAnnotatedMethods(
                Before.class);
        return befores.isEmpty() ? statement : new RunBefores(statement,
                befores, target);
    }

    
Returns a Statement: run all non-overridden @After methods on this class and superclasses before running next; all After methods are always executed: exceptions thrown by previous steps are combined, if necessary, with exceptions from After methods into a MultipleFailureException. /**
     * Returns a {@link Statement}: run all non-overridden {@code @After}
     * methods on this class and superclasses before running {@code next}; all
     * After methods are always executed: exceptions thrown by previous steps
     * are combined, if necessary, with exceptions from After methods into a
     * {@link MultipleFailureException}.
     */
    protected Statement withAfters(FrameworkMethod method, Object target,
            Statement statement) {
        List<FrameworkMethod> afters = getTestClass().getAnnotatedMethods(
                After.class);
        return afters.isEmpty() ? statement : new RunAfters(statement, afters,
                target);
    }

    private Statement withRules(FrameworkMethod method, Object target,
            Statement statement) {
        List<TestRule> testRules = getTestRules(target);
        Statement result = statement;
        result = withMethodRules(method, testRules, target, result);
        result = withTestRules(method, testRules, result);

        return result;
    }

    private Statement withMethodRules(FrameworkMethod method, List<TestRule> testRules,
            Object target, Statement result) {
        for (org.junit.rules.MethodRule each : getMethodRules(target)) {
            if (!testRules.contains(each)) {
                result = each.apply(result, method, target);
            }
        }
        return result;
    }

    private List<org.junit.rules.MethodRule> getMethodRules(Object target) {
        return rules(target);
    }

    
Params:
target – the test case instance
Returns:
a list of MethodRules that should be applied when executing this
        test/**
     * @param target the test case instance
     * @return a list of MethodRules that should be applied when executing this
     *         test
     */
    protected List<MethodRule> rules(Object target) {
        List<MethodRule> rules = getTestClass().getAnnotatedMethodValues(target, 
                Rule.class, MethodRule.class);
        
        rules.addAll(getTestClass().getAnnotatedFieldValues(target,
                Rule.class, MethodRule.class));
        
        return rules;
    }

    
Returns a Statement: apply all non-static fields annotated with Rule. 
Params:
statement – The base statement
Returns:
a RunRules statement if any class-level Rules are found, or the base statement/**
     * Returns a {@link Statement}: apply all non-static fields
     * annotated with {@link Rule}.
     *
     * @param statement The base statement
     * @return a RunRules statement if any class-level {@link Rule}s are
     *         found, or the base statement
     */
    private Statement withTestRules(FrameworkMethod method, List<TestRule> testRules,
            Statement statement) {
        return testRules.isEmpty() ? statement :
                new RunRules(statement, testRules, describeChild(method));
    }

    
Params:
target – the test case instance
Returns:
a list of TestRules that should be applied when executing this
        test/**
     * @param target the test case instance
     * @return a list of TestRules that should be applied when executing this
     *         test
     */
    protected List<TestRule> getTestRules(Object target) {
        List<TestRule> result = getTestClass().getAnnotatedMethodValues(target,
                Rule.class, TestRule.class);

        result.addAll(getTestClass().getAnnotatedFieldValues(target,
                Rule.class, TestRule.class));

        return result;
    }

    private Class<? extends Throwable> getExpectedException(Test annotation) {
        if (annotation == null || annotation.expected() == None.class) {
            return null;
        } else {
            return annotation.expected();
        }
    }

    private boolean expectsException(Test annotation) {
        return getExpectedException(annotation) != null;
    }

    private long getTimeout(Test annotation) {
        if (annotation == null) {
            return 0;
        }
        return annotation.timeout();
    }
}