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;
import org.plumelib.util.CollectionsPlume;

// TODO: large parts of this file are the same as PerDirectorySuite.java.
// Reduce duplication by moving common parts to an abstract class.
/**
 * PerDirectorySuite runs a test class once for each set of parameters returned by its method marked
 * with {@code @Parameters}
 *
 * <p>To use:<br>
 * Annotated your test class with {@code @RunWith(PerDirectorySuite.class)}<br>
 * Create a parameters 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 PerFileSuite 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 PerFileSuite(Class<?> klass) throws Throwable {
    super(klass, Collections.emptyList());
    final TestClass testClass = getTestClass();
    final Class<?> javaTestClass = testClass.getJavaClass();
    final List<Object[]> parametersList = getParametersList(testClass);

    for (Object[] parameters : parametersList) {
      runners.add(new PerParameterSetTestRunner(javaTestClass, parameters));
    }
  }

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

    List<File> javaFiles;
    // We will have either a method getTestDirs which returns String [] or getTestFiles
    // which returns List<Object []> or getParametersMethod would fail
    if (method.getReturnType().isArray()) {
      String[] dirs = (String[]) method.invokeExplosively(null);
      javaFiles = TestUtilities.findNestedJavaTestFiles(dirs);

    } else {
      javaFiles = (List<File>) method.invokeExplosively(null);
    }

    List<Object[]> argumentLists =
        CollectionsPlume.mapList((File javaFile) -> new Object[] {javaFile}, javaFiles);

    return argumentLists;
  }

  /** 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(requiredFormsMessage, testClass.getName(), methods);
    } // else

    FrameworkMethod method = parameterMethods.get(0);

    Class<?> returnType = method.getReturnType();
    String methodName = method.getName();
    switch (methodName) {
      case "getTestDirs":
        if (returnType.isArray()) {
          if (returnType.getComponentType() != String.class) {
            throw new RuntimeException(
                "Component type of getTestDirs must be java.lang.String, found "
                    + returnType.getComponentType().getCanonicalName());
          }
        }
        break;

      case "getTestFiles":
        // We'll force people to return a List for now but enforcing exactly List<File> or a
        // subtype thereof is not easy.
        if (!List.class.getCanonicalName().equals(returnType.getCanonicalName())) {
          throw new RuntimeException("getTestFiles must return a List<File>, found " + returnType);
        }
        break;

      default:
        throw new BugInCF(requiredFormsMessage, testClass.getName(), 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 or getTestFiles method. */
  private static final String requiredFormsMessage =
      "Parameter method must have one of the following two forms:%n"
          + "@Parameters String [] getTestDirs()%n"
          + "@Parameters List<File> getTestFiles()%n"
          + "testClass=%s%n"
          + "parameterMethods=%s";

  /** Runs the test class for the set of parameters passed in the constructor. */
  private static class PerParameterSetTestRunner extends BlockJUnit4ClassRunner {
    private final Object[] parameters;

    PerParameterSetTestRunner(Class<?> type, Object[] parameters) throws InitializationError {
      super(type);
      this.parameters = parameters;
    }

    @Override
    public Object createTest() throws Exception {
      return getTestClass().getOnlyConstructor().newInstance(parameters);
    }

    String testCaseName() {
      File file = (File) parameters[0];
      String name =
          file.getPath()
              .replace(".java", "")
              .replace("tests" + System.getProperty("file.separator"), "");
      return name;
    }

    @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);
    }
  }
}