/*
 * Copyright (C) 2013 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.example.inputmanagercompat;

import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;
import android.util.Log;
import android.util.SparseArray;
import android.view.InputDevice;
import android.view.MotionEvent;

import java.lang.ref.WeakReference;
import java.util.ArrayDeque;
import java.util.HashMap;
import java.util.Map;
import java.util.Queue;

public class InputManagerV9 implements InputManagerCompat {
    private static final String LOG_TAG = "InputManagerV9";
    private static final int MESSAGE_TEST_FOR_DISCONNECT = 101;
    private static final long CHECK_ELAPSED_TIME = 3000L;

    private static final int ON_DEVICE_ADDED = 0;
    private static final int ON_DEVICE_CHANGED = 1;
    private static final int ON_DEVICE_REMOVED = 2;

    private final SparseArray<long[]> mDevices;
    private final Map<InputDeviceListener, Handler> mListeners;
    private final Handler mDefaultHandler;

    private static class PollingMessageHandler extends Handler {
        private final WeakReference<InputManagerV9> mInputManager;

        PollingMessageHandler(InputManagerV9 im) {
            mInputManager = new WeakReference<InputManagerV9>(im);
        }

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            switch (msg.what) {
                case MESSAGE_TEST_FOR_DISCONNECT:
                    InputManagerV9 imv = mInputManager.get();
                    if (null != imv) {
                        long time = SystemClock.elapsedRealtime();
                        int size = imv.mDevices.size();
                        for (int i = 0; i < size; i++) {
                            long[] lastContact = imv.mDevices.valueAt(i);
                            if (null != lastContact) {
                                if (time - lastContact[0] > CHECK_ELAPSED_TIME) {
                                    // check to see if the device has been
                                    // disconnected
                                    int id = imv.mDevices.keyAt(i);
                                    if (null == InputDevice.getDevice(id)) {
                                        // disconnected!
                                        imv.notifyListeners(ON_DEVICE_REMOVED, id);
                                        imv.mDevices.remove(id);
                                    } else {
                                        lastContact[0] = time;
                                    }
                                }
                            }
                        }
                        sendEmptyMessageDelayed(MESSAGE_TEST_FOR_DISCONNECT,
                                CHECK_ELAPSED_TIME);
                    }
                    break;
            }
        }

    }

    public InputManagerV9() {
        mDevices = new SparseArray<long[]>();
        mListeners = new HashMap<InputDeviceListener, Handler>();
        mDefaultHandler = new PollingMessageHandler(this);
        // as a side-effect, populates our collection of watched
        // input devices
        getInputDeviceIds();
    }

    @Override
    public InputDevice getInputDevice(int id) {
        return InputDevice.getDevice(id);
    }

    @Override
    public int[] getInputDeviceIds() {
        // add any hitherto unknown devices to our
        // collection of watched input devices
        int[] activeDevices = InputDevice.getDeviceIds();
        long time = SystemClock.elapsedRealtime();
        for ( int id : activeDevices ) {
            long[] lastContact = mDevices.get(id);
            if ( null == lastContact ) {
                // we have a new device
                mDevices.put(id, new long[] { time });
            }
        }
        return activeDevices;
    }

    @Override
    public void registerInputDeviceListener(InputDeviceListener listener, Handler handler) {
        mListeners.remove(listener);
        if (handler == null) {
            handler = mDefaultHandler;
        }
        mListeners.put(listener, handler);
    }

    @Override
    public void unregisterInputDeviceListener(InputDeviceListener listener) {
        mListeners.remove(listener);
    }

    private void notifyListeners(int why, int deviceId) {
        // the state of some device has changed
        if (!mListeners.isEmpty()) {
            // yes... this will cause an object to get created... hopefully
            // it won't happen very often
            for (InputDeviceListener listener : mListeners.keySet()) {
                Handler handler = mListeners.get(listener);
                DeviceEvent odc = DeviceEvent.getDeviceEvent(why, deviceId, listener);
                handler.post(odc);
            }
        }
    }

    private static class DeviceEvent implements Runnable {
        private int mMessageType;
        private int mId;
        private InputDeviceListener mListener;
        private static Queue<DeviceEvent> sEventQueue = new ArrayDeque<DeviceEvent>();

        private DeviceEvent() {
        }

        static DeviceEvent getDeviceEvent(int messageType, int id,
                InputDeviceListener listener) {
            DeviceEvent curChanged = sEventQueue.poll();
            if (null == curChanged) {
                curChanged = new DeviceEvent();
            }
            curChanged.mMessageType = messageType;
            curChanged.mId = id;
            curChanged.mListener = listener;
            return curChanged;
        }

        @Override
        public void run() {
            switch (mMessageType) {
                case ON_DEVICE_ADDED:
                    mListener.onInputDeviceAdded(mId);
                    break;
                case ON_DEVICE_CHANGED:
                    mListener.onInputDeviceChanged(mId);
                    break;
                case ON_DEVICE_REMOVED:
                    mListener.onInputDeviceRemoved(mId);
                    break;
                default:
                    Log.e(LOG_TAG, "Unknown Message Type");
                    break;
            }
            // dump this runnable back in the queue
            sEventQueue.offer(this);
        }
    }

    @Override
    public void onGenericMotionEvent(MotionEvent event) {
        // detect new devices
        int id = event.getDeviceId();
        long[] timeArray = mDevices.get(id);
        if (null == timeArray) {
            notifyListeners(ON_DEVICE_ADDED, id);
            timeArray = new long[1];
            mDevices.put(id, timeArray);
        }
        long time = SystemClock.elapsedRealtime();
        timeArray[0] = time;
    }

    @Override
    public void onPause() {
        mDefaultHandler.removeMessages(MESSAGE_TEST_FOR_DISCONNECT);
    }

    @Override
    public void onResume() {
        mDefaultHandler.sendEmptyMessage(MESSAGE_TEST_FOR_DISCONNECT);
    }

}
