/*
 * 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.systemui.statusbar.policy;

import android.content.Context;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraManager;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Process;
import android.text.TextUtils;
import android.util.Log;

import java.lang.ref.WeakReference;
import java.util.ArrayList;

/**
 * Manages the flashlight.
 */
public class FlashlightController {

    private static final String TAG = "FlashlightController";
    private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);

    private static final int DISPATCH_ERROR = 0;
    private static final int DISPATCH_CHANGED = 1;
    private static final int DISPATCH_AVAILABILITY_CHANGED = 2;

    private final CameraManager mCameraManager;
    /** Call {@link #ensureHandler()} before using */
    private Handler mHandler;

    /** Lock on mListeners when accessing */
    private final ArrayList<WeakReference<FlashlightListener>> mListeners = new ArrayList<>(1);

    /** Lock on {@code this} when accessing */
    private boolean mFlashlightEnabled;

    private final String mCameraId;
    private boolean mTorchAvailable;

    public FlashlightController(Context mContext) {
        mCameraManager = (CameraManager) mContext.getSystemService(Context.CAMERA_SERVICE);

        String cameraId = null;
        try {
            cameraId = getCameraId();
        } catch (Throwable e) {
            Log.e(TAG, "Couldn't initialize.", e);
            return;
        } finally {
            mCameraId = cameraId;
        }

        if (mCameraId != null) {
            ensureHandler();
            mCameraManager.registerTorchCallback(mTorchCallback, mHandler);
        }
    }

    public void setFlashlight(boolean enabled) {
        boolean pendingError = false;
        synchronized (this) {
            if (mFlashlightEnabled != enabled) {
                mFlashlightEnabled = enabled;
                try {
                    mCameraManager.setTorchMode(mCameraId, enabled);
                } catch (CameraAccessException e) {
                    Log.e(TAG, "Couldn't set torch mode", e);
                    mFlashlightEnabled = false;
                    pendingError = true;
                }
            }
        }
        dispatchModeChanged(mFlashlightEnabled);
        if (pendingError) {
            dispatchError();
        }
    }

    public boolean hasFlashlight() {
        return mCameraId != null;
    }

    public synchronized boolean isEnabled() {
        return mFlashlightEnabled;
    }

    public synchronized boolean isAvailable() {
        return mTorchAvailable;
    }

    public void addListener(FlashlightListener l) {
        synchronized (mListeners) {
            cleanUpListenersLocked(l);
            mListeners.add(new WeakReference<>(l));
        }
    }

    public void removeListener(FlashlightListener l) {
        synchronized (mListeners) {
            cleanUpListenersLocked(l);
        }
    }

    private synchronized void ensureHandler() {
        if (mHandler == null) {
            HandlerThread thread = new HandlerThread(TAG, Process.THREAD_PRIORITY_BACKGROUND);
            thread.start();
            mHandler = new Handler(thread.getLooper());
        }
    }

    private String getCameraId() throws CameraAccessException {
        String[] ids = mCameraManager.getCameraIdList();
        for (String id : ids) {
            CameraCharacteristics c = mCameraManager.getCameraCharacteristics(id);
            Boolean flashAvailable = c.get(CameraCharacteristics.FLASH_INFO_AVAILABLE);
            Integer lensFacing = c.get(CameraCharacteristics.LENS_FACING);
            if (flashAvailable != null && flashAvailable
                    && lensFacing != null && lensFacing == CameraCharacteristics.LENS_FACING_BACK) {
                return id;
            }
        }
        return null;
    }

    private void dispatchModeChanged(boolean enabled) {
        dispatchListeners(DISPATCH_CHANGED, enabled);
    }

    private void dispatchError() {
        dispatchListeners(DISPATCH_CHANGED, false /* argument (ignored) */);
    }

    private void dispatchAvailabilityChanged(boolean available) {
        dispatchListeners(DISPATCH_AVAILABILITY_CHANGED, available);
    }

    private void dispatchListeners(int message, boolean argument) {
        synchronized (mListeners) {
            final int N = mListeners.size();
            boolean cleanup = false;
            for (int i = 0; i < N; i++) {
                FlashlightListener l = mListeners.get(i).get();
                if (l != null) {
                    if (message == DISPATCH_ERROR) {
                        l.onFlashlightError();
                    } else if (message == DISPATCH_CHANGED) {
                        l.onFlashlightChanged(argument);
                    } else if (message == DISPATCH_AVAILABILITY_CHANGED) {
                        l.onFlashlightAvailabilityChanged(argument);
                    }
                } else {
                    cleanup = true;
                }
            }
            if (cleanup) {
                cleanUpListenersLocked(null);
            }
        }
    }

    private void cleanUpListenersLocked(FlashlightListener listener) {
        for (int i = mListeners.size() - 1; i >= 0; i--) {
            FlashlightListener found = mListeners.get(i).get();
            if (found == null || found == listener) {
                mListeners.remove(i);
            }
        }
    }

    private final CameraManager.TorchCallback mTorchCallback =
            new CameraManager.TorchCallback() {

        @Override
        public void onTorchModeUnavailable(String cameraId) {
            if (TextUtils.equals(cameraId, mCameraId)) {
                setCameraAvailable(false);
            }
        }

        @Override
        public void onTorchModeChanged(String cameraId, boolean enabled) {
            if (TextUtils.equals(cameraId, mCameraId)) {
                setCameraAvailable(true);
                setTorchMode(enabled);
            }
        }

        private void setCameraAvailable(boolean available) {
            boolean changed;
            synchronized (FlashlightController.this) {
                changed = mTorchAvailable != available;
                mTorchAvailable = available;
            }
            if (changed) {
                if (DEBUG) Log.d(TAG, "dispatchAvailabilityChanged(" + available + ")");
                dispatchAvailabilityChanged(available);
            }
        }

        private void setTorchMode(boolean enabled) {
            boolean changed;
            synchronized (FlashlightController.this) {
                changed = mFlashlightEnabled != enabled;
                mFlashlightEnabled = enabled;
            }
            if (changed) {
                if (DEBUG) Log.d(TAG, "dispatchModeChanged(" + enabled + ")");
                dispatchModeChanged(enabled);
            }
        }
    };

    public interface FlashlightListener {

        /**
         * Called when the flashlight was turned off or on.
         * @param enabled true if the flashlight is currently turned on.
         */
        void onFlashlightChanged(boolean enabled);


        /**
         * Called when there is an error that turns the flashlight off.
         */
        void onFlashlightError();

        /**
         * Called when there is a change in availability of the flashlight functionality
         * @param available true if the flashlight is currently available.
         */
        void onFlashlightAvailabilityChanged(boolean available);
    }
}