/*
 * Copyright (C) 2014 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 com.android.camera.util;

import android.app.Activity;
import android.app.KeyguardManager;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.SystemClock;

import com.android.camera.debug.Log;
import javax.annotation.Nullable;

/**
 * Workaround for lockscreen double-onResume() bug:
 * <p>
 * We track 3 startup situations:
 * <ul>
 * <li>Normal startup -- e.g. from GEL.</li>
 * <li>Secure lock screen startup -- e.g. with a keycode.</li>
 * <li>Non-secure lock screen startup -- e.g. with just a swipe.</li>
 * </ul>
 * The KeyguardManager service can be queried to determine which state we are in.
 * If started from the lock screen, the activity may be quickly started,
 * resumed, paused, stopped, and then started and resumed again. This is
 * problematic for launch time from the lock screen because we typically open the
 * camera in onResume() and close it in onPause(). These camera operations take
 * a long time to complete. To workaround it, this class filters out
 * high-frequency onResume()->onPause() sequences if the KeyguardManager
 * indicates that we have started from the lock screen.
 * </p>
 * <p>
 * Subclasses should override the appropriate on[Create|Start...]Tasks() method
 * in place of the original.
 * </p>
 * <p>
 * Sequences of onResume() followed quickly by onPause(), when the activity is
 * started from a lockscreen will result in a quick no-op.<br>
 * </p>
 */
public abstract class QuickActivity extends Activity {
    private static final Log.Tag TAG = new Log.Tag("QuickActivity");

    /** onResume tasks delay from secure lockscreen. */
    private static final long ON_RESUME_DELAY_SECURE_MILLIS = 30;
    /** onResume tasks delay from non-secure lockscreen. */
    private static final long ON_RESUME_DELAY_NON_SECURE_MILLIS = 15;

    /** A reference to the main handler on which to run lifecycle methods. */
    private Handler mMainHandler;

    /**
     * True if onResume tasks have been skipped, and made false again once they
     * are executed within the onResume() method or from a delayed Runnable.
     */
    private boolean mSkippedFirstOnResume = false;

    /** When application execution started in SystemClock.elapsedRealtimeNanos(). */
    protected long mExecutionStartNanoTime = 0;
    /** Was this session started with onCreate(). */
    protected boolean mStartupOnCreate = false;

    /** Handle to Keyguard service. */
    @Nullable
    private KeyguardManager mKeyguardManager = null;
    /**
     * A runnable for deferring tasks to be performed in onResume() if starting
     * from the lockscreen.
     */
    private final Runnable mOnResumeTasks = new Runnable() {
            @Override
        public void run() {
            if (mSkippedFirstOnResume) {
                Log.v(TAG, "delayed Runnable --> onResumeTasks()");
                // Doing the tasks, can set to false.
                mSkippedFirstOnResume = false;
                onResumeTasks();
            }
        }
    };

    @Override
    protected final void onNewIntent(Intent intent) {
        logLifecycle("onNewIntent", true);
        Log.v(TAG, "Intent Action = " + intent.getAction());
        setIntent(intent);
        super.onNewIntent(intent);
        onNewIntentTasks(intent);
        logLifecycle("onNewIntent", false);
    }

    @Override
    protected final void onCreate(Bundle bundle) {
        mExecutionStartNanoTime = SystemClock.elapsedRealtimeNanos();
        logLifecycle("onCreate", true);
        mStartupOnCreate = true;
        super.onCreate(bundle);
        mMainHandler = new Handler(getMainLooper());
        onCreateTasks(bundle);
        logLifecycle("onCreate", false);
    }

    @Override
    protected final void onStart() {
        logLifecycle("onStart", true);
        onStartTasks();
        super.onStart();
        logLifecycle("onStart", false);
    }

    @Override
    protected final void onResume() {
        logLifecycle("onResume", true);

        // For lockscreen launch, there are two possible flows:
        // 1. onPause() does not occur before mOnResumeTasks is executed:
        //      Runnable mOnResumeTasks sets mSkippedFirstOnResume to false
        // 2. onPause() occurs within ON_RESUME_DELAY_*_MILLIS:
        //     a. Runnable mOnResumeTasks is removed
        //     b. onPauseTasks() is skipped, mSkippedFirstOnResume remains true
        //     c. next onResume() will immediately execute onResumeTasks()
        //        and set mSkippedFirstOnResume to false

        Log.v(TAG, "onResume(): isKeyguardLocked() = " + isKeyguardLocked());
        mMainHandler.removeCallbacks(mOnResumeTasks);
        if (isKeyguardLocked() && mSkippedFirstOnResume == false) {
            // Skipping onResumeTasks; set to true.
            mSkippedFirstOnResume = true;
            long delay = isKeyguardSecure() ? ON_RESUME_DELAY_SECURE_MILLIS :
                    ON_RESUME_DELAY_NON_SECURE_MILLIS;
            Log.v(TAG, "onResume() --> postDelayed(mOnResumeTasks," + delay + ")");
            mMainHandler.postDelayed(mOnResumeTasks, delay);
        } else {
            Log.v(TAG, "onResume --> onResumeTasks()");
            // Doing the tasks, can set to false.
            mSkippedFirstOnResume = false;
            onResumeTasks();
        }
        super.onResume();
        logLifecycle("onResume", false);
    }

    @Override
    protected final void onPause() {
        logLifecycle("onPause", true);
        mMainHandler.removeCallbacks(mOnResumeTasks);
        // Only run onPauseTasks if we have not skipped onResumeTasks in a
        // first call to onResume.  If we did skip onResumeTasks (note: we
        // just killed any delayed Runnable), we also skip onPauseTasks to
        // adhere to lifecycle state machine.
        if (mSkippedFirstOnResume == false) {
            Log.v(TAG, "onPause --> onPauseTasks()");
            onPauseTasks();
        }
        super.onPause();
        mStartupOnCreate = false;
        logLifecycle("onPause", false);
    }

    @Override
    protected final void onStop() {
        if (isChangingConfigurations()) {
            Log.v(TAG, "changing configurations");
        }
        logLifecycle("onStop", true);
        onStopTasks();
        super.onStop();
        logLifecycle("onStop", false);
    }

    @Override
    protected final void onRestart() {
        logLifecycle("onRestart", true);
        super.onRestart();
        // TODO Support onRestartTasks() and handle the workaround for that too.
        logLifecycle("onRestart", false);
    }

    @Override
    protected final void onDestroy() {
        logLifecycle("onDestroy", true);
        onDestroyTasks();
        super.onDestroy();
        logLifecycle("onDestroy", false);
    }

    private void logLifecycle(String methodName, boolean start) {
        String prefix = start ? "START" : "END";
        Log.v(TAG, prefix + " " + methodName + ": Activity = " + toString());
    }

    protected boolean isKeyguardLocked() {
        if (mKeyguardManager == null) {
            mKeyguardManager = AndroidServices.instance().provideKeyguardManager();
        }
        if (mKeyguardManager != null) {
            return mKeyguardManager.isKeyguardLocked();
        }
        return false;
    }

    protected boolean isKeyguardSecure() {
        if (mKeyguardManager == null) {
            mKeyguardManager = AndroidServices.instance().provideKeyguardManager();
        }
        if (mKeyguardManager != null) {
            return mKeyguardManager.isKeyguardSecure();
        }
        return false;
    }

    /**
     * Subclasses should override this in place of {@link Activity#onNewIntent}.
     */
    protected void onNewIntentTasks(Intent newIntent) {
    }

    /**
     * Subclasses should override this in place of {@link Activity#onCreate}.
     */
    protected void onCreateTasks(Bundle savedInstanceState) {
    }

    /**
     * Subclasses should override this in place of {@link Activity#onStart}.
     */
    protected void onStartTasks() {
    }

    /**
     * Subclasses should override this in place of {@link Activity#onResume}.
     */
    protected void onResumeTasks() {
    }

    /**
     * Subclasses should override this in place of {@link Activity#onPause}.
     */
    protected void onPauseTasks() {
    }

    /**
     * Subclasses should override this in place of {@link Activity#onStop}.
     */
    protected void onStopTasks() {
    }

    /**
     * Subclasses should override this in place of {@link Activity#onDestroy}.
     */
    protected void onDestroyTasks() {
    }
}