/**
 * Copyright (C) 2012 The Android Open Source Project
 *
 * 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.
 */
package android.service.dreams;

import android.annotation.IdRes;
import android.annotation.LayoutRes;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.SdkConstant;
import android.annotation.SdkConstant.SdkConstantType;
import android.app.Activity;
import android.app.ActivityTaskManager;
import android.app.AlarmManager;
import android.app.Service;
import android.compat.annotation.UnsupportedAppUsage;
import android.content.Intent;
import android.os.Build;
import android.os.Handler;
import android.os.IBinder;
import android.os.IRemoteCallback;
import android.os.Looper;
import android.os.PowerManager;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.util.Log;
import android.util.MathUtils;
import android.util.Slog;
import android.view.ActionMode;
import android.view.Display;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.SearchEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.WindowManager;
import android.view.WindowManager.LayoutParams;
import android.view.accessibility.AccessibilityEvent;

import com.android.internal.util.DumpUtils;
import com.android.internal.util.DumpUtils.Dump;

import java.io.FileDescriptor;
import java.io.PrintWriter;

/**
 * Extend this class to implement a custom dream (available to the user as a "Daydream").
 *
 * <p>Dreams are interactive screensavers launched when a charging device is idle, or docked in a
 * desk dock. Dreams provide another modality for apps to express themselves, tailored for
 * an exhibition/lean-back experience.</p>
 *
 * <p>The {@code DreamService} lifecycle is as follows:</p>
 * <ol>
 *   <li>{@link #onAttachedToWindow}
 *     <p>Use this for initial setup, such as calling {@link #setContentView setContentView()}.</li>
 *   <li>{@link #onDreamingStarted}
 *     <p>Your dream has started, so you should begin animations or other behaviors here.</li>
 *   <li>{@link #onDreamingStopped}
 *     <p>Use this to stop the things you started in {@link #onDreamingStarted}.</li>
 *   <li>{@link #onDetachedFromWindow}
 *     <p>Use this to dismantle resources (for example, detach from handlers
 *        and listeners).</li>
 * </ol>
 *
 * <p>In addition, onCreate and onDestroy (from the Service interface) will also be called, but
 * initialization and teardown should be done by overriding the hooks above.</p>
 *
 * <p>To be available to the system, your {@code DreamService} should be declared in the
 * manifest as follows:</p>
 * <pre>
 * &lt;service
 *     android:name=".MyDream"
 *     android:exported="true"
 *     android:icon="@drawable/my_icon"
 *     android:label="@string/my_dream_label" >
 *
 *     &lt;intent-filter>
 *         &lt;action android:name="android.service.dreams.DreamService" />
 *         &lt;category android:name="android.intent.category.DEFAULT" />
 *     &lt;/intent-filter>
 *
 *     &lt;!-- Point to additional information for this dream (optional) -->
 *     &lt;meta-data
 *         android:name="android.service.dream"
 *         android:resource="@xml/my_dream" />
 * &lt;/service>
 * </pre>
 *
 * <p>If specified with the {@code <meta-data>} element,
 * additional information for the dream is defined using the
 * {@link android.R.styleable#Dream &lt;dream&gt;} element in a separate XML file.
 * Currently, the only addtional
 * information you can provide is for a settings activity that allows the user to configure
 * the dream behavior. For example:</p>
 * <p class="code-caption">res/xml/my_dream.xml</p>
 * <pre>
 * &lt;dream xmlns:android="http://schemas.android.com/apk/res/android"
 *     android:settingsActivity="com.example.app/.MyDreamSettingsActivity" />
 * </pre>
 * <p>This makes a Settings button available alongside your dream's listing in the
 * system settings, which when pressed opens the specified activity.</p>
 *
 *
 * <p>To specify your dream layout, call {@link #setContentView}, typically during the
 * {@link #onAttachedToWindow} callback. For example:</p>
 * <pre>
 * public class MyDream extends DreamService {
 *
 *     &#64;Override
 *     public void onAttachedToWindow() {
 *         super.onAttachedToWindow();
 *
 *         // Exit dream upon user touch
 *         setInteractive(false);
 *         // Hide system UI
 *         setFullscreen(true);
 *         // Set the dream layout
 *         setContentView(R.layout.dream);
 *     }
 * }
 * </pre>
 *
 * <p>When targeting api level 21 and above, you must declare the service in your manifest file
 * with the {@link android.Manifest.permission#BIND_DREAM_SERVICE} permission. For example:</p>
 * <pre>
 * &lt;service
 *     android:name=".MyDream"
 *     android:exported="true"
 *     android:icon="@drawable/my_icon"
 *     android:label="@string/my_dream_label"
 *     android:permission="android.permission.BIND_DREAM_SERVICE">
 *   &lt;intent-filter>
 *     &lt;action android:name=”android.service.dreams.DreamService” />
 *     &lt;category android:name=”android.intent.category.DEFAULT” />
 *   &lt;/intent-filter>
 * &lt;/service>
 * </pre>
 */
public class DreamService extends Service implements Window.Callback {
    private final String TAG = DreamService.class.getSimpleName() + "[" + getClass().getSimpleName() + "]";

    /**
     * The name of the dream manager service.
     * @hide
     */
    public static final String DREAM_SERVICE = "dreams";

    /**
     * The {@link Intent} that must be declared as handled by the service.
     */
    @SdkConstant(SdkConstantType.SERVICE_ACTION)
    public static final String SERVICE_INTERFACE =
            "android.service.dreams.DreamService";

    /**
     * Name under which a Dream publishes information about itself.
     * This meta-data must reference an XML resource containing
     * a <code>&lt;{@link android.R.styleable#Dream dream}&gt;</code>
     * tag.
     */
    public static final String DREAM_META_DATA = "android.service.dream";

    private final IDreamManager mDreamManager;
    private final Handler mHandler = new Handler(Looper.getMainLooper());
    private IBinder mDreamToken;
    private Window mWindow;
    private Activity mActivity;
    private boolean mInteractive;
    private boolean mLowProfile = true;
    private boolean mFullscreen;
    private boolean mScreenBright = true;
    private boolean mStarted;
    private boolean mWaking;
    private boolean mFinished;
    private boolean mCanDoze;
    private boolean mDozing;
    private boolean mWindowless;
    private int mDozeScreenState = Display.STATE_UNKNOWN;
    private int mDozeScreenBrightness = PowerManager.BRIGHTNESS_DEFAULT;

    private boolean mDebug = false;

    private DreamServiceWrapper mDreamServiceWrapper;
    private Runnable mDispatchAfterOnAttachedToWindow;

    public DreamService() {
        mDreamManager = IDreamManager.Stub.asInterface(ServiceManager.getService(DREAM_SERVICE));
    }

    /**
     * @hide
     */
    public void setDebug(boolean dbg) {
        mDebug = dbg;
    }

    // begin Window.Callback methods
    /** {@inheritDoc} */
    @Override
    public boolean dispatchKeyEvent(KeyEvent event) {
        // TODO: create more flexible version of mInteractive that allows use of KEYCODE_BACK
        if (!mInteractive) {
            if (mDebug) Slog.v(TAG, "Waking up on keyEvent");
            wakeUp();
            return true;
        } else if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
            if (mDebug) Slog.v(TAG, "Waking up on back key");
            wakeUp();
            return true;
        }
        return mWindow.superDispatchKeyEvent(event);
    }

    /** {@inheritDoc} */
    @Override
    public boolean dispatchKeyShortcutEvent(KeyEvent event) {
        if (!mInteractive) {
            if (mDebug) Slog.v(TAG, "Waking up on keyShortcutEvent");
            wakeUp();
            return true;
        }
        return mWindow.superDispatchKeyShortcutEvent(event);
    }

    /** {@inheritDoc} */
    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        // TODO: create more flexible version of mInteractive that allows clicks
        // but finish()es on any other kind of activity
        if (!mInteractive) {
            if (mDebug) Slog.v(TAG, "Waking up on touchEvent");
            wakeUp();
            return true;
        }
        return mWindow.superDispatchTouchEvent(event);
    }

    /** {@inheritDoc} */
    @Override
    public boolean dispatchTrackballEvent(MotionEvent event) {
        if (!mInteractive) {
            if (mDebug) Slog.v(TAG, "Waking up on trackballEvent");
            wakeUp();
            return true;
        }
        return mWindow.superDispatchTrackballEvent(event);
    }

    /** {@inheritDoc} */
    @Override
    public boolean dispatchGenericMotionEvent(MotionEvent event) {
        if (!mInteractive) {
            if (mDebug) Slog.v(TAG, "Waking up on genericMotionEvent");
            wakeUp();
            return true;
        }
        return mWindow.superDispatchGenericMotionEvent(event);
    }

    /** {@inheritDoc} */
    @Override
    public boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {
        return false;
    }

    /** {@inheritDoc} */
    @Override
    public View onCreatePanelView(int featureId) {
        return null;
    }

    /** {@inheritDoc} */
    @Override
    public boolean onCreatePanelMenu(int featureId, Menu menu) {
        return false;
    }

    /** {@inheritDoc} */
    @Override
    public boolean onPreparePanel(int featureId, View view, Menu menu) {
        return false;
    }

    /** {@inheritDoc} */
    @Override
    public boolean onMenuOpened(int featureId, Menu menu) {
        return false;
    }

    /** {@inheritDoc} */
    @Override
    public boolean onMenuItemSelected(int featureId, MenuItem item) {
        return false;
    }

    /** {@inheritDoc} */
    @Override
    public void onWindowAttributesChanged(LayoutParams attrs) {
    }

    /** {@inheritDoc} */
    @Override
    public void onContentChanged() {
    }

    /** {@inheritDoc} */
    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
    }

    /** {@inheritDoc} */
    @Override
    public void onAttachedToWindow() {
    }

    /** {@inheritDoc} */
    @Override
    public void onDetachedFromWindow() {
    }

    /** {@inheritDoc} */
    @Override
    public void onPanelClosed(int featureId, Menu menu) {
    }

    /** {@inheritDoc} */
    @Override
    public boolean onSearchRequested(SearchEvent event) {
        return onSearchRequested();
    }

    /** {@inheritDoc} */
    @Override
    public boolean onSearchRequested() {
        return false;
    }

    /** {@inheritDoc} */
    @Override
    public ActionMode onWindowStartingActionMode(android.view.ActionMode.Callback callback) {
        return null;
    }

    /** {@inheritDoc} */
    @Override
    public ActionMode onWindowStartingActionMode(
            android.view.ActionMode.Callback callback, int type) {
        return null;
    }

    /** {@inheritDoc} */
    @Override
    public void onActionModeStarted(ActionMode mode) {
    }

    /** {@inheritDoc} */
    @Override
    public void onActionModeFinished(ActionMode mode) {
    }
    // end Window.Callback methods

    // begin public api
    /**
     * Retrieves the current {@link android.view.WindowManager} for the dream.
     * Behaves similarly to {@link android.app.Activity#getWindowManager()}.
     *
     * @return The current window manager, or null if the dream is not started.
     */
    public WindowManager getWindowManager() {
        return mWindow != null ? mWindow.getWindowManager() : null;
    }

    /**
     * Retrieves the current {@link android.view.Window} for the dream.
     * Behaves similarly to {@link android.app.Activity#getWindow()}.
     *
     * @return The current window, or null if the dream is not started.
     */
    public Window getWindow() {
        return mWindow;
    }

   /**
     * Inflates a layout resource and set it to be the content view for this Dream.
     * Behaves similarly to {@link android.app.Activity#setContentView(int)}.
     *
     * <p>Note: Requires a window, do not call before {@link #onAttachedToWindow()}</p>
     *
     * @param layoutResID Resource ID to be inflated.
     *
     * @see #setContentView(android.view.View)
     * @see #setContentView(android.view.View, android.view.ViewGroup.LayoutParams)
     */
    public void setContentView(@LayoutRes int layoutResID) {
        getWindow().setContentView(layoutResID);
    }

    /**
     * Sets a view to be the content view for this Dream.
     * Behaves similarly to {@link android.app.Activity#setContentView(android.view.View)} in an activity,
     * including using {@link ViewGroup.LayoutParams#MATCH_PARENT} as the layout height and width of the view.
     *
     * <p>Note: This requires a window, so you should usually call it during
     * {@link #onAttachedToWindow()} and never earlier (you <strong>cannot</strong> call it
     * during {@link #onCreate}).</p>
     *
     * @see #setContentView(int)
     * @see #setContentView(android.view.View, android.view.ViewGroup.LayoutParams)
     */
    public void setContentView(View view) {
        getWindow().setContentView(view);
    }

    /**
     * Sets a view to be the content view for this Dream.
     * Behaves similarly to
     * {@link android.app.Activity#setContentView(android.view.View, android.view.ViewGroup.LayoutParams)}
     * in an activity.
     *
     * <p>Note: This requires a window, so you should usually call it during
     * {@link #onAttachedToWindow()} and never earlier (you <strong>cannot</strong> call it
     * during {@link #onCreate}).</p>
     *
     * @param view The desired content to display.
     * @param params Layout parameters for the view.
     *
     * @see #setContentView(android.view.View)
     * @see #setContentView(int)
     */
    public void setContentView(View view, ViewGroup.LayoutParams params) {
        getWindow().setContentView(view, params);
    }

    /**
     * Adds a view to the Dream's window, leaving other content views in place.
     *
     * <p>Note: Requires a window, do not call before {@link #onAttachedToWindow()}</p>
     *
     * @param view The desired content to display.
     * @param params Layout parameters for the view.
     */
    public void addContentView(View view, ViewGroup.LayoutParams params) {
        getWindow().addContentView(view, params);
    }

    /**
     * Finds a view that was identified by the id attribute from the XML that
     * was processed in {@link #onCreate}.
     *
     * <p>Note: Requires a window, do not call before {@link #onAttachedToWindow()}</p>
     * <p>
     * <strong>Note:</strong> In most cases -- depending on compiler support --
     * the resulting view is automatically cast to the target class type. If
     * the target class type is unconstrained, an explicit cast may be
     * necessary.
     *
     * @param id the ID to search for
     * @return The view if found or null otherwise.
     * @see View#findViewById(int)
     * @see DreamService#requireViewById(int)
     */
    @Nullable
    public <T extends View> T findViewById(@IdRes int id) {
        return getWindow().findViewById(id);
    }

    /**
     * Finds a view that was identified by the id attribute from the XML that was processed in
     * {@link #onCreate}, or throws an IllegalArgumentException if the ID is invalid or there is no
     * matching view in the hierarchy.
     *
     * <p>Note: Requires a window, do not call before {@link #onAttachedToWindow()}</p>
     * <p>
     * <strong>Note:</strong> In most cases -- depending on compiler support --
     * the resulting view is automatically cast to the target class type. If
     * the target class type is unconstrained, an explicit cast may be
     * necessary.
     *
     * @param id the ID to search for
     * @return a view with given ID
     * @see View#requireViewById(int)
     * @see DreamService#findViewById(int)
     */
    @NonNull
    public final <T extends View> T requireViewById(@IdRes int id) {
        T view = findViewById(id);
        if (view == null) {
            throw new IllegalArgumentException(
                    "ID does not reference a View inside this DreamService");
        }
        return view;
    }

    /**
     * Marks this dream as interactive to receive input events.
     *
     * <p>Non-interactive dreams (default) will dismiss on the first input event.</p>
     *
     * <p>Interactive dreams should call {@link #finish()} to dismiss themselves.</p>
     *
     * @param interactive True if this dream will handle input events.
     */
    public void setInteractive(boolean interactive) {
        mInteractive = interactive;
    }

    /**
     * Returns whether or not this dream is interactive.  Defaults to false.
     *
     * @see #setInteractive(boolean)
     */
    public boolean isInteractive() {
        return mInteractive;
    }

    /**
     * Sets View.SYSTEM_UI_FLAG_LOW_PROFILE on the content view.
     *
     * @param lowProfile True to set View.SYSTEM_UI_FLAG_LOW_PROFILE
     * @hide There is no reason to have this -- dreams can set this flag
     * on their own content view, and from there can actually do the
     * correct interactions with it (seeing when it is cleared etc).
     */
    public void setLowProfile(boolean lowProfile) {
        if (mLowProfile != lowProfile) {
            mLowProfile = lowProfile;
            int flag = View.SYSTEM_UI_FLAG_LOW_PROFILE;
            applySystemUiVisibilityFlags(mLowProfile ? flag : 0, flag);
        }
    }

    /**
     * Returns whether or not this dream is in low profile mode. Defaults to true.
     *
     * @see #setLowProfile(boolean)
     * @hide
     */
    public boolean isLowProfile() {
        return getSystemUiVisibilityFlagValue(View.SYSTEM_UI_FLAG_LOW_PROFILE, mLowProfile);
    }

    /**
     * Controls {@link android.view.WindowManager.LayoutParams#FLAG_FULLSCREEN}
     * on the dream's window.
     *
     * @param fullscreen If true, the fullscreen flag will be set; else it
     * will be cleared.
     */
    public void setFullscreen(boolean fullscreen) {
        if (mFullscreen != fullscreen) {
            mFullscreen = fullscreen;
            int flag = WindowManager.LayoutParams.FLAG_FULLSCREEN;
            applyWindowFlags(mFullscreen ? flag : 0, flag);
        }
    }

    /**
     * Returns whether or not this dream is in fullscreen mode. Defaults to false.
     *
     * @see #setFullscreen(boolean)
     */
    public boolean isFullscreen() {
        return mFullscreen;
    }

    /**
     * Marks this dream as keeping the screen bright while dreaming.
     *
     * @param screenBright True to keep the screen bright while dreaming.
     */
    public void setScreenBright(boolean screenBright) {
        if (mScreenBright != screenBright) {
            mScreenBright = screenBright;
            int flag = WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON;
            applyWindowFlags(mScreenBright ? flag : 0, flag);
        }
    }

    /**
     * Returns whether or not this dream keeps the screen bright while dreaming.
     * Defaults to false, allowing the screen to dim if necessary.
     *
     * @see #setScreenBright(boolean)
     */
    public boolean isScreenBright() {
        return getWindowFlagValue(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON, mScreenBright);
    }

    /**
     * Marks this dream as windowless.  Only available to doze dreams.
     *
     * @hide
     *
     */
    public void setWindowless(boolean windowless) {
        mWindowless = windowless;
    }

    /**
     * Returns whether or not this dream is windowless.  Only available to doze dreams.
     *
     * @hide
     */
    public boolean isWindowless() {
        return mWindowless;
    }

    /**
     * Returns true if this dream is allowed to doze.
     * <p>
     * The value returned by this method is only meaningful when the dream has started.
     * </p>
     *
     * @return True if this dream can doze.
     * @see #startDozing
     * @hide For use by system UI components only.
     */
    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023)
    public boolean canDoze() {
        return mCanDoze;
    }

    /**
     * Starts dozing, entering a deep dreamy sleep.
     * <p>
     * Dozing enables the system to conserve power while the user is not actively interacting
     * with the device.  While dozing, the display will remain on in a low-power state
     * and will continue to show its previous contents but the application processor and
     * other system components will be allowed to suspend when possible.
     * </p><p>
     * While the application processor is suspended, the dream may stop executing code
     * for long periods of time.  Prior to being suspended, the dream may schedule periodic
     * wake-ups to render new content by scheduling an alarm with the {@link AlarmManager}.
     * The dream may also keep the CPU awake by acquiring a
     * {@link android.os.PowerManager#PARTIAL_WAKE_LOCK partial wake lock} when necessary.
     * Note that since the purpose of doze mode is to conserve power (especially when
     * running on battery), the dream should not wake the CPU very often or keep it
     * awake for very long.
     * </p><p>
     * It is a good idea to call this method some time after the dream's entry animation
     * has completed and the dream is ready to doze.  It is important to completely
     * finish all of the work needed before dozing since the application processor may
     * be suspended at any moment once this method is called unless other wake locks
     * are being held.
     * </p><p>
     * Call {@link #stopDozing} or {@link #finish} to stop dozing.
     * </p>
     *
     * @see #stopDozing
     * @hide For use by system UI components only.
     */
    @UnsupportedAppUsage
    public void startDozing() {
        if (mCanDoze && !mDozing) {
            mDozing = true;
            updateDoze();
        }
    }

    private void updateDoze() {
        if (mDreamToken == null) {
            Slog.w(TAG, "Updating doze without a dream token.");
            return;
        }

        if (mDozing) {
            try {
                mDreamManager.startDozing(mDreamToken, mDozeScreenState, mDozeScreenBrightness);
            } catch (RemoteException ex) {
                // system server died
            }
        }
    }

    /**
     * Stops dozing, returns to active dreaming.
     * <p>
     * This method reverses the effect of {@link #startDozing}.  From this moment onward,
     * the application processor will be kept awake as long as the dream is running
     * or until the dream starts dozing again.
     * </p>
     *
     * @see #startDozing
     * @hide For use by system UI components only.
     */
    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023)
    public void stopDozing() {
        if (mDozing) {
            mDozing = false;
            try {
                mDreamManager.stopDozing(mDreamToken);
            } catch (RemoteException ex) {
                // system server died
            }
        }
    }

    /**
     * Returns true if the dream will allow the system to enter a low-power state while
     * it is running without actually turning off the screen.  Defaults to false,
     * keeping the application processor awake while the dream is running.
     *
     * @return True if the dream is dozing.
     *
     * @see #setDozing(boolean)
     * @hide For use by system UI components only.
     */
    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023)
    public boolean isDozing() {
        return mDozing;
    }

    /**
     * Gets the screen state to use while dozing.
     *
     * @return The screen state to use while dozing, such as {@link Display#STATE_ON},
     * {@link Display#STATE_DOZE}, {@link Display#STATE_DOZE_SUSPEND},
     * {@link Display#STATE_ON_SUSPEND}, {@link Display#STATE_OFF}, or {@link Display#STATE_UNKNOWN}
     * for the default behavior.
     *
     * @see #setDozeScreenState
     * @hide For use by system UI components only.
     */
    public int getDozeScreenState() {
        return mDozeScreenState;
    }

    /**
     * Sets the screen state to use while dozing.
     * <p>
     * The value of this property determines the power state of the primary display
     * once {@link #startDozing} has been called.  The default value is
     * {@link Display#STATE_UNKNOWN} which lets the system decide.
     * The dream may set a different state before starting to doze and may
     * perform transitions between states while dozing to conserve power and
     * achieve various effects.
     * </p><p>
     * Some devices will have dedicated hardware ("Sidekick") to animate
     * the display content while the CPU sleeps. If the dream and the hardware support
     * this, {@link Display#STATE_ON_SUSPEND} or {@link Display#STATE_DOZE_SUSPEND}
     * will switch control to the Sidekick.
     * </p><p>
     * If not using Sidekick, it is recommended that the state be set to
     * {@link Display#STATE_DOZE_SUSPEND} once the dream has completely
     * finished drawing and before it releases its wakelock
     * to allow the display hardware to be fully suspended.  While suspended,
     * the display will preserve its on-screen contents.
     * </p><p>
     * If the doze suspend state is used, the dream must make sure to set the mode back
     * to {@link Display#STATE_DOZE} or {@link Display#STATE_ON} before drawing again
     * since the display updates may be ignored and not seen by the user otherwise.
     * </p><p>
     * The set of available display power states and their behavior while dozing is
     * hardware dependent and may vary across devices.  The dream may therefore
     * need to be modified or configured to correctly support the hardware.
     * </p>
     *
     * @param state The screen state to use while dozing, such as {@link Display#STATE_ON},
     * {@link Display#STATE_DOZE}, {@link Display#STATE_DOZE_SUSPEND},
     * {@link Display#STATE_ON_SUSPEND}, {@link Display#STATE_OFF}, or {@link Display#STATE_UNKNOWN}
     * for the default behavior.
     *
     * @hide For use by system UI components only.
     */
    @UnsupportedAppUsage
    public void setDozeScreenState(int state) {
        if (mDozeScreenState != state) {
            mDozeScreenState = state;
            updateDoze();
        }
    }

    /**
     * Gets the screen brightness to use while dozing.
     *
     * @return The screen brightness while dozing as a value between
     * {@link PowerManager#BRIGHTNESS_OFF} (0) and {@link PowerManager#BRIGHTNESS_ON} (255),
     * or {@link PowerManager#BRIGHTNESS_DEFAULT} (-1) to ask the system to apply
     * its default policy based on the screen state.
     *
     * @see #setDozeScreenBrightness
     * @hide For use by system UI components only.
     */
    @UnsupportedAppUsage
    public int getDozeScreenBrightness() {
        return mDozeScreenBrightness;
    }

    /**
     * Sets the screen brightness to use while dozing.
     * <p>
     * The value of this property determines the power state of the primary display
     * once {@link #startDozing} has been called.  The default value is
     * {@link PowerManager#BRIGHTNESS_DEFAULT} which lets the system decide.
     * The dream may set a different brightness before starting to doze and may adjust
     * the brightness while dozing to conserve power and achieve various effects.
     * </p><p>
     * Note that dream may specify any brightness in the full 0-255 range, including
     * values that are less than the minimum value for manual screen brightness
     * adjustments by the user.  In particular, the value may be set to 0 which may
     * turn off the backlight entirely while still leaving the screen on although
     * this behavior is device dependent and not guaranteed.
     * </p><p>
     * The available range of display brightness values and their behavior while dozing is
     * hardware dependent and may vary across devices.  The dream may therefore
     * need to be modified or configured to correctly support the hardware.
     * </p>
     *
     * @param brightness The screen brightness while dozing as a value between
     * {@link PowerManager#BRIGHTNESS_OFF} (0) and {@link PowerManager#BRIGHTNESS_ON} (255),
     * or {@link PowerManager#BRIGHTNESS_DEFAULT} (-1) to ask the system to apply
     * its default policy based on the screen state.
     *
     * @hide For use by system UI components only.
     */
    @UnsupportedAppUsage
    public void setDozeScreenBrightness(int brightness) {
        if (brightness != PowerManager.BRIGHTNESS_DEFAULT) {
            brightness = clampAbsoluteBrightness(brightness);
        }
        if (mDozeScreenBrightness != brightness) {
            mDozeScreenBrightness = brightness;
            updateDoze();
        }
    }

    /**
     * Called when this Dream is constructed.
     */
    @Override
    public void onCreate() {
        if (mDebug) Slog.v(TAG, "onCreate()");
        super.onCreate();
    }

    /**
     * Called when the dream's window has been created and is visible and animation may now begin.
     */
    public void onDreamingStarted() {
        if (mDebug) Slog.v(TAG, "onDreamingStarted()");
        // hook for subclasses
    }

    /**
     * Called when this Dream is stopped, either by external request or by calling finish(),
     * before the window has been removed.
     */
    public void onDreamingStopped() {
        if (mDebug) Slog.v(TAG, "onDreamingStopped()");
        // hook for subclasses
    }

    /**
     * Called when the dream is being asked to stop itself and wake.
     * <p>
     * The default implementation simply calls {@link #finish} which ends the dream
     * immediately.  Subclasses may override this function to perform a smooth exit
     * transition then call {@link #finish} afterwards.
     * </p><p>
     * Note that the dream will only be given a short period of time (currently about
     * five seconds) to wake up.  If the dream does not finish itself in a timely manner
     * then the system will forcibly finish it once the time allowance is up.
     * </p>
     */
    public void onWakeUp() {
        finish();
    }

    /** {@inheritDoc} */
    @Override
    public final IBinder onBind(Intent intent) {
        if (mDebug) Slog.v(TAG, "onBind() intent = " + intent);
        mDreamServiceWrapper = new DreamServiceWrapper();
        return mDreamServiceWrapper;
    }

    /**
     * Stops the dream and detaches from the window.
     * <p>
     * When the dream ends, the system will be allowed to go to sleep fully unless there
     * is a reason for it to be awake such as recent user activity or wake locks being held.
     * </p>
     */
    public final void finish() {
        if (mDebug) Slog.v(TAG, "finish(): mFinished=" + mFinished);

        Activity activity = mActivity;
        if (activity != null) {
            if (!activity.isFinishing()) {
                // In case the activity is not finished yet, do it now.
                activity.finishAndRemoveTask();
            }
            return;
        }

        if (mFinished) {
            return;
        }
        mFinished = true;

        if (mDreamToken == null) {
            Slog.w(TAG, "Finish was called before the dream was attached.");
            stopSelf();
            return;
        }

        try {
            // finishSelf will unbind the dream controller from the dream service. This will
            // trigger DreamService.this.onDestroy and DreamService.this will die.
            mDreamManager.finishSelf(mDreamToken, true /*immediate*/);
        } catch (RemoteException ex) {
            // system server died
        }
    }

    /**
     * Wakes the dream up gently.
     * <p>
     * Calls {@link #onWakeUp} to give the dream a chance to perform an exit transition.
     * When the transition is over, the dream should call {@link #finish}.
     * </p>
     */
    public final void wakeUp() {
        wakeUp(false);
    }

    private void wakeUp(boolean fromSystem) {
        if (mDebug) Slog.v(TAG, "wakeUp(): fromSystem=" + fromSystem
                + ", mWaking=" + mWaking + ", mFinished=" + mFinished);

        if (!mWaking && !mFinished) {
            mWaking = true;

            // As a minor optimization, invoke the callback first in case it simply
            // calls finish() immediately so there wouldn't be much point in telling
            // the system that we are finishing the dream gently.
            onWakeUp();

            // Now tell the system we are waking gently, unless we already told
            // it we were finishing immediately.
            if (!fromSystem && !mFinished) {
                if (mActivity == null) {
                    Slog.w(TAG, "WakeUp was called before the dream was attached.");
                } else {
                    try {
                        mDreamManager.finishSelf(mDreamToken, false /*immediate*/);
                    } catch (RemoteException ex) {
                        // system server died
                    }
                }
            }
        }
    }

    /** {@inheritDoc} */
    @Override
    public void onDestroy() {
        if (mDebug) Slog.v(TAG, "onDestroy()");
        // hook for subclasses

        // Just in case destroy came in before detach, let's take care of that now
        detach();

        super.onDestroy();
    }

    // end public api

    /**
     * Called by DreamController.stopDream() when the Dream is about to be unbound and destroyed.
     *
     * Must run on mHandler.
     */
    private final void detach() {
        if (mStarted) {
            if (mDebug) Slog.v(TAG, "detach(): Calling onDreamingStopped()");
            mStarted = false;
            onDreamingStopped();
        }

        if (mActivity != null && !mActivity.isFinishing()) {
            mActivity.finishAndRemoveTask();
        } else {
            finish();
        }

        mDreamToken = null;
        mCanDoze = false;
    }

    /**
     * Called when the Dream is ready to be shown.
     *
     * Must run on mHandler.
     *
     * @param dreamToken Token for this dream service.
     * @param started A callback that will be invoked once onDreamingStarted has completed.
     */
    private void attach(IBinder dreamToken, boolean canDoze, IRemoteCallback started) {
        if (mDreamToken != null) {
            Slog.e(TAG, "attach() called when dream with token=" + mDreamToken
                    + " already attached");
            return;
        }
        if (mFinished || mWaking) {
            Slog.w(TAG, "attach() called after dream already finished");
            try {
                mDreamManager.finishSelf(dreamToken, true /*immediate*/);
            } catch (RemoteException ex) {
                // system server died
            }
            return;
        }

        mDreamToken = dreamToken;
        mCanDoze = canDoze;
        if (mWindowless && !mCanDoze) {
            throw new IllegalStateException("Only doze dreams can be windowless");
        }

        mDispatchAfterOnAttachedToWindow = () -> {
            if (mWindow != null || mWindowless) {
                mStarted = true;
                try {
                    onDreamingStarted();
                } finally {
                    try {
                        started.sendResult(null);
                    } catch (RemoteException e) {
                        throw e.rethrowFromSystemServer();
                    }
                }
            }
        };

        // We need to defer calling onDreamingStarted until after the activity is created.
        // If the dream is windowless, we can call it immediately. Otherwise, we wait
        // for the DreamActivity to report onActivityCreated via
        // DreamServiceWrapper.onActivityCreated.
        if (!mWindowless) {
            Intent i = new Intent(this, DreamActivity.class);
            i.setPackage(getApplicationContext().getPackageName());
            i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            i.putExtra(DreamActivity.EXTRA_CALLBACK, mDreamServiceWrapper);

            try {
                if (!ActivityTaskManager.getService().startDreamActivity(i)) {
                    detach();
                    return;
                }
            } catch (RemoteException e) {
                Log.w(TAG, "Could not connect to activity task manager to start dream activity");
                e.rethrowFromSystemServer();
            }
        } else {
            mDispatchAfterOnAttachedToWindow.run();
        }
    }

    private void onWindowCreated(Window w) {
        mWindow = w;
        mWindow.setCallback(this);
        mWindow.requestFeature(Window.FEATURE_NO_TITLE);

        WindowManager.LayoutParams lp = mWindow.getAttributes();
        lp.windowAnimations = com.android.internal.R.style.Animation_Dream;
        lp.flags |= (WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN
                    | WindowManager.LayoutParams.FLAG_LAYOUT_INSET_DECOR
                    | WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
                    | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD
                    | WindowManager.LayoutParams.FLAG_ALLOW_LOCK_WHILE_SCREEN_ON
                    | WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED
                    | (mFullscreen ? WindowManager.LayoutParams.FLAG_FULLSCREEN : 0)
                    | (mScreenBright ? WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON : 0)
                    );
        mWindow.setAttributes(lp);
        // Workaround: Currently low-profile and in-window system bar backgrounds don't go
        // along well. Dreams usually don't need such bars anyways, so disable them by default.
        mWindow.clearFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);

        applySystemUiVisibilityFlags(
                (mLowProfile ? View.SYSTEM_UI_FLAG_LOW_PROFILE : 0),
                View.SYSTEM_UI_FLAG_LOW_PROFILE);

        mWindow.getDecorView().addOnAttachStateChangeListener(
                new View.OnAttachStateChangeListener() {
                    @Override
                    public void onViewAttachedToWindow(View v) {
                        mDispatchAfterOnAttachedToWindow.run();
                    }

                    @Override
                    public void onViewDetachedFromWindow(View v) {
                        mActivity = null;
                        finish();
                    }
                });
    }

    private boolean getWindowFlagValue(int flag, boolean defaultValue) {
        return mWindow == null ? defaultValue : (mWindow.getAttributes().flags & flag) != 0;
    }

    private void applyWindowFlags(int flags, int mask) {
        if (mWindow != null) {
            WindowManager.LayoutParams lp = mWindow.getAttributes();
            lp.flags = applyFlags(lp.flags, flags, mask);
            mWindow.setAttributes(lp);
            mWindow.getWindowManager().updateViewLayout(mWindow.getDecorView(), lp);
        }
    }

    private boolean getSystemUiVisibilityFlagValue(int flag, boolean defaultValue) {
        View v = mWindow == null ? null : mWindow.getDecorView();
        return v == null ? defaultValue : (v.getSystemUiVisibility() & flag) != 0;
    }

    private void applySystemUiVisibilityFlags(int flags, int mask) {
        View v = mWindow == null ? null : mWindow.getDecorView();
        if (v != null) {
            v.setSystemUiVisibility(applyFlags(v.getSystemUiVisibility(), flags, mask));
        }
    }

    private int applyFlags(int oldFlags, int flags, int mask) {
        return (oldFlags&~mask) | (flags&mask);
    }

    @Override
    protected void dump(final FileDescriptor fd, PrintWriter pw, final String[] args) {
        DumpUtils.dumpAsync(mHandler, new Dump() {
            @Override
            public void dump(PrintWriter pw, String prefix) {
                dumpOnHandler(fd, pw, args);
            }
        }, pw, "", 1000);
    }

    /** @hide */
    protected void dumpOnHandler(FileDescriptor fd, PrintWriter pw, String[] args) {
        pw.print(TAG + ": ");
        if (mFinished) {
            pw.println("stopped");
        } else {
            pw.println("running (dreamToken=" + mDreamToken + ")");
        }
        pw.println("  window: " + mWindow);
        pw.print("  flags:");
        if (isInteractive()) pw.print(" interactive");
        if (isLowProfile()) pw.print(" lowprofile");
        if (isFullscreen()) pw.print(" fullscreen");
        if (isScreenBright()) pw.print(" bright");
        if (isWindowless()) pw.print(" windowless");
        if (isDozing()) pw.print(" dozing");
        else if (canDoze()) pw.print(" candoze");
        pw.println();
        if (canDoze()) {
            pw.println("  doze screen state: " + Display.stateToString(mDozeScreenState));
            pw.println("  doze screen brightness: " + mDozeScreenBrightness);
        }
    }

    private static int clampAbsoluteBrightness(int value) {
        return MathUtils.constrain(value, PowerManager.BRIGHTNESS_OFF, PowerManager.BRIGHTNESS_ON);
    }

    /**
     * The DreamServiceWrapper is used as a gateway to the system_server, where DreamController
     * uses it to control the DreamService. It is also used to receive callbacks from the
     * DreamActivity.
     */
    final class DreamServiceWrapper extends IDreamService.Stub {
        @Override
        public void attach(final IBinder dreamToken, final boolean canDoze,
                IRemoteCallback started) {
            mHandler.post(() -> DreamService.this.attach(dreamToken, canDoze, started));
        }

        @Override
        public void detach() {
            mHandler.post(DreamService.this::detach);
        }

        @Override
        public void wakeUp() {
            mHandler.post(() -> DreamService.this.wakeUp(true /*fromSystem*/));
        }

        /** @hide */
        void onActivityCreated(DreamActivity a) {
            mActivity = a;
            onWindowCreated(a.getWindow());
        }
    }
}