package org.checkerframework.framework.test;

import java.io.File;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.StringJoiner;
import org.checkerframework.javacutil.BugInCF;
import org.junit.runner.Runner;
import org.junit.runner.notification.RunNotifier;
import org.junit.runners.BlockJUnit4ClassRunner;
import org.junit.runners.Parameterized.Parameters;
import org.junit.runners.Suite;
import org.junit.runners.model.FrameworkMethod;
import org.junit.runners.model.InitializationError;
import org.junit.runners.model.Statement;
import org.junit.runners.model.TestClass;

// TODO: large parts of this file are the same as PerFileSuite.java.
// Reduce duplication by moving common parts to an abstract class.
/**
 * PerDirectorySuite runs a test class once for each set of javaFiles returned by its method marked
 * with {@code @Parameters}
 *
 * <p>To use:<br>
 * Annotated your test class with {@code @RunWith(PerDirectorySuite.class)}<br>
 * Create a javaFiles method by annotating a public static method with {@code @Parameters}. This
 * method must return either a {@code List<File>} where each element of the list is a Java file to
 * test against OR a {@code String []} where each String in the array is a directory in the tests
 * directory.
 */
public class PerDirectorySuite extends Suite {

  @Retention(RetentionPolicy.RUNTIME)
  @Target(ElementType.METHOD)
  public @interface Name {}

  private final ArrayList<Runner> runners = new ArrayList<>();

  @Override
  protected List<Runner> getChildren() {
    return runners;
  }

  /**
   * Only called reflectively. Do not use programmatically.
   *
   * @param klass the class whose tests to run
   */
  @SuppressWarnings("nullness") // JUnit needs to be annotated
  public PerDirectorySuite(Class<?> klass) throws Throwable {
    super(klass, Collections.emptyList());
    final TestClass testClass = getTestClass();
    final Class<?> javaTestClass = testClass.getJavaClass();
    final List<List<File>> parametersList = getParametersList(testClass);

    for (List<File> parameters : parametersList) {
      runners.add(new PerParameterSetTestRunner(javaTestClass, parameters));
    }
  }

  /** Returns a list of one-element arrays, each containing a Java File. */
  @SuppressWarnings("nullness") // JUnit needs to be annotated
  private List<List<File>> getParametersList(TestClass klass) throws Throwable {
    FrameworkMethod method = getParametersMethod(klass);

    // We must have a method getTestDirs which returns String[],
    // or getParametersMethod would fail.
    if (!method.getReturnType().isArray()) {
      return Collections.emptyList();
    }
    String[] dirs = (String[]) method.invokeExplosively(null);
    return TestUtilities.findJavaFilesPerDirectory(new File("tests"), dirs);
  }

  /** Returns method annotated @Parameters, typically the getTestDirs or getTestFiles method. */
  private FrameworkMethod getParametersMethod(TestClass testClass) {
    final List<FrameworkMethod> parameterMethods = testClass.getAnnotatedMethods(Parameters.class);
    if (parameterMethods.size() != 1) {
      // Construct error message

      String methods;
      if (parameterMethods.isEmpty()) {
        methods = "[No methods specified]";
      } else {
        StringJoiner sj = new StringJoiner(", ");
        for (FrameworkMethod method : parameterMethods) {
          sj.add(method.getName());
        }
        methods = sj.toString();
      }

      throw new BugInCF(
          "Exactly one of the following methods should be declared:%n%s%n"
              + "testClass=%s%n"
              + "parameterMethods=%s",
          requiredFormsMessage, testClass.getName(), methods);
    }

    FrameworkMethod method = parameterMethods.get(0);

    Class<?> returnType = method.getReturnType();
    String methodName = method.getName();
    switch (methodName) {
      case "getTestDirs":
        if (!(returnType.isArray() && returnType.getComponentType() == String.class)) {
          throw new RuntimeException("getTestDirs should return String[], found " + returnType);
        }
        break;

      default:
        throw new RuntimeException(
            requiredFormsMessage
                + "%n"
                + "testClass="
                + testClass.getName()
                + "%n"
                + "parameterMethods="
                + method);
    }

    int modifiers = method.getMethod().getModifiers();
    if (!Modifier.isStatic(modifiers) || !Modifier.isPublic(modifiers)) {
      throw new RuntimeException(
          "Parameter method (" + method.getName() + ") must be public and static");
    }

    return method;
  }

  /** The message about the required getTestDirs method. */
  private static final String requiredFormsMessage =
      "Parameter method must have the following form:"
          + System.lineSeparator()
          + "@Parameters String[] getTestDirs()";

  /** Runs the test class for the set of javaFiles passed in the constructor. */
  private static class PerParameterSetTestRunner extends BlockJUnit4ClassRunner {
    private final List<File> javaFiles;

    PerParameterSetTestRunner(Class<?> type, List<File> javaFiles) throws InitializationError {
      super(type);
      this.javaFiles = javaFiles;
    }

    @Override
    public Object createTest() throws Exception {
      Object[] arguments = Collections.singleton(javaFiles).toArray();
      return getTestClass().getOnlyConstructor().newInstance(arguments);
    }

    String testCaseName() {
      File file = javaFiles.get(0).getParentFile();
      if (file == null) {
        throw new Error("root was passed? " + javaFiles.get(0));
      }
      return file.getPath().replace("tests" + System.getProperty("file.separator"), "");
    }

    @Override
    protected String getName() {
      return String.format("[%s]", testCaseName());
    }

    @Override
    protected String testName(final FrameworkMethod method) {
      return String.format("%s[%s]", method.getName(), testCaseName());
    }

    @Override
    protected void validateZeroArgConstructor(List<Throwable> errors) {
      // constructor should have args.
    }

    @Override
    protected Statement classBlock(RunNotifier notifier) {
      return childrenInvoker(notifier);
    }
  }
}