package com.google.android.apps.common.testing.ui.espresso;

import static com.google.android.apps.common.testing.ui.espresso.matcher.ViewMatchers.isAssignableFrom;
import static com.google.android.apps.common.testing.ui.espresso.matcher.ViewMatchers.isDescendantOfA;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.android.apps.common.testing.ui.espresso.action.ScrollToAction;
import com.google.android.apps.common.testing.ui.espresso.base.MainThread;
import com.google.android.apps.common.testing.ui.espresso.util.HumanReadables;
import com.google.common.base.Optional;

import android.util.Log;
import android.view.View;
import android.widget.AdapterView;

import org.hamcrest.Matcher;
import org.hamcrest.StringDescription;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.FutureTask;
import java.util.concurrent.atomic.AtomicReference;

import javax.inject.Inject;

/**
 * Provides the primary interface for test authors to perform actions or asserts on views.
 * <p>
 * Each interaction is associated with a view identified by a view matcher. All view actions and
 * asserts are performed on the UI thread (thus ensuring sequential execution). The same goes for
 * retrieval of views (this is done to ensure that view state is "fresh" prior to execution of each
 * operation).
 * <p>
 */
public final class ViewInteraction {

  private static final String TAG = ViewInteraction.class.getSimpleName();

  private final UiController uiController;
  private final ViewFinder viewFinder;
  private final Executor mainThreadExecutor;
  private final FailureHandler failureHandler;
  private final Matcher<View> viewMatcher;
  private final AtomicReference<Matcher<Root>> rootMatcherRef;

  @Inject
  ViewInteraction(
      UiController uiController,
      ViewFinder viewFinder,
      @MainThread Executor mainThreadExecutor,
      FailureHandler failureHandler,
      Matcher<View> viewMatcher,
      AtomicReference<Matcher<Root>> rootMatcherRef) {
    this.viewFinder = checkNotNull(viewFinder);
    this.uiController = checkNotNull(uiController);
    this.failureHandler = checkNotNull(failureHandler);
    this.mainThreadExecutor = checkNotNull(mainThreadExecutor);
    this.viewMatcher = checkNotNull(viewMatcher);
    this.rootMatcherRef = checkNotNull(rootMatcherRef);
  }

  /**
   * Performs the given action(s) on the view selected by the current view matcher. If more than one
   * action is provided, actions are executed in the order provided with precondition checks running
   * prior to each action.
   *
   * @param viewActions one or more actions to execute.
   * @return this interaction for further perform/verification calls.
   */
  public ViewInteraction perform(final ViewAction... viewActions) {
    checkNotNull(viewActions);
    for (ViewAction action : viewActions) {
      doPerform(action);
    }
    return this;
  }


  /**
   * Makes this ViewInteraction scoped to the root selected by the given root matcher.
   */
  public ViewInteraction inRoot(Matcher<Root> rootMatcher) {
    this.rootMatcherRef.set(checkNotNull(rootMatcher));
    return this;
  }

  private void doPerform(final ViewAction viewAction) {
    checkNotNull(viewAction);
    final Matcher<? extends View> constraints = checkNotNull(viewAction.getConstraints());
    runSynchronouslyOnUiThread(new Runnable() {

      @Override
      public void run() {
        uiController.loopMainThreadUntilIdle();
        View targetView = viewFinder.getView();
        Log.i(TAG, String.format(
            "Performing '%s' action on view %s", viewAction.getDescription(), viewMatcher));
        if (!constraints.matches(targetView)) {
          // TODO(user): update this to describeMismatch once hamcrest is updated to new
          StringDescription stringDescription = new StringDescription(new StringBuilder(
              "Action will not be performed because the target view "
              + "does not match one or more of the following constraints:\n"));
          constraints.describeTo(stringDescription);
          stringDescription.appendText("\nTarget view: ")
              .appendValue(HumanReadables.describe(targetView));

          if (viewAction instanceof ScrollToAction
              && isDescendantOfA(isAssignableFrom((AdapterView.class))).matches(targetView)) {
            stringDescription.appendText(
                "\nFurther Info: ScrollToAction on a view inside an AdapterView will not work. "
                + "Use Espresso.onData to load the view.");
          }
          throw new PerformException.Builder()
            .withActionDescription(viewAction.getDescription())
            .withViewDescription(viewMatcher.toString())
            .withCause(new RuntimeException(stringDescription.toString()))
            .build();
        } else {
          viewAction.perform(uiController, targetView);
        }
      }
    });
  }

  /**
   * Checks the given {@link ViewAssertion} on the the view selected by the current view matcher.
   *
   * @param viewAssert the assertion to perform.
   * @return this interaction for further perform/verification calls.
   */
  public ViewInteraction check(final ViewAssertion viewAssert) {
    checkNotNull(viewAssert);
    runSynchronouslyOnUiThread(new Runnable() {
      @Override
      public void run() {
        uiController.loopMainThreadUntilIdle();

        Optional<View> targetView = Optional.absent();
        Optional<NoMatchingViewException> missingViewException = Optional.absent();
        try {
          targetView = Optional.of(viewFinder.getView());
        } catch (NoMatchingViewException nsve) {
          missingViewException = Optional.of(nsve);
        }
        viewAssert.check(targetView, missingViewException);
      }
    });
    return this;
  }

  private void runSynchronouslyOnUiThread(Runnable action) {
    FutureTask<Void> uiTask = new FutureTask<Void>(action, null);
    mainThreadExecutor.execute(uiTask);
    try {
      uiTask.get();
    } catch (InterruptedException ie) {
      throw new RuntimeException("Interrupted  running UI task", ie);
    } catch (ExecutionException ee) {
      failureHandler.handle(ee.getCause(), viewMatcher);
    }
  }
}