/*
 * Copyright (C) 2009 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;

import static com.android.camera.Util.Assert;

import android.hardware.Camera.Parameters;
import android.os.Build;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;
import android.os.Message;
import jp.gr.java_conf.ka_ka_xyz.util.Log;

import java.io.IOException;

/**
 * The class is used to hold an {@code android.hardware.Camera} instance.
 * 
 * <p>
 * The {@code open()} and {@code release()} calls are similar to the ones in
 * {@code android.hardware.Camera}. The difference is if {@code keep()} is
 * called before {@code release()}, CameraHolder will try to hold the
 * {@code android.hardware.Camera} instance for a while, so if {@code open()} is
 * called soon after, we can avoid the cost of {@code open()} in
 * {@code android.hardware.Camera}.
 * 
 * <p>
 * This is used in switching between {@code Camera} and {@code VideoCamera}
 * activities.
 */
public class CameraHolder {
	private static final String TAG = "CameraHolder";
	private android.hardware.Camera mCameraDevice;
	private long mKeepBeforeTime = 0; // Keep the Camera before this time.
	private final Handler mHandler;
	private int mUsers = 0; // number of open() - number of release()

	// We store the camera parameters when we actually open the device,
	// so we can restore them in the subsequent open() requests by the user.
	// This prevents the parameters set by the Camera activity used by
	// the VideoCamera activity inadvertently.
	private Parameters mParameters;

	// Use a singleton.
	private static CameraHolder sHolder;

	public static synchronized CameraHolder instance() {
		if (sHolder == null) {
			sHolder = new CameraHolder();
		}
		return sHolder;
	}

	private static final int RELEASE_CAMERA = 1;

	private class MyHandler extends Handler {
		MyHandler(Looper looper) {
			super(looper);
		}

		@Override
		public void handleMessage(Message msg) {
			switch (msg.what) {
			case RELEASE_CAMERA:
				synchronized (CameraHolder.this) {
					// In 'CameraHolder.open', the 'RELEASE_CAMERA' message
					// will be removed if it is found in the queue. However,
					// there is a chance that this message has been handled
					// before being removed. So, we need to add a check
					// here:
					if (CameraHolder.this.mUsers == 0)
						releaseCamera();
				}
				break;
			}
		}
	}

	private CameraHolder() {
		HandlerThread ht = new HandlerThread("CameraHolder");
		ht.start();
		mHandler = new MyHandler(ht.getLooper());
	}

	public synchronized android.hardware.Camera open()
			throws CameraHardwareException {
		Assert(mUsers == 0);
		if (mCameraDevice == null) {
			try {
				mCameraDevice = android.hardware.Camera.open();
			} catch (RuntimeException e) {
				Log.e(TAG, "fail to connect Camera", e);
				throw new CameraHardwareException(e);
			}
			mParameters = mCameraDevice.getParameters();
			// } else {
			// try {
			// mCameraDevice.reconnect();
			// } catch (IOException e) {
			// Log.e(TAG, "reconnect failed.");
			// throw new CameraHardwareException(e);
			// }
			// mCameraDevice.setParameters(mParameters);
		}
		++mUsers;
		mHandler.removeMessages(RELEASE_CAMERA);
		mKeepBeforeTime = 0;
		return mCameraDevice;
	}

	/**
	 * Tries to open the hardware camera. If the camera is being used or
	 * unavailable then return {@code null}.
	 */
	public synchronized android.hardware.Camera tryOpen() {
		try {
			return mUsers == 0 ? open() : null;
		} catch (CameraHardwareException e) {
			// In eng build, we throw the exception so that test tool
			// can detect it and report it
			if ("eng".equals(Build.TYPE)) {
				throw new RuntimeException(e);
			}
			return null;
		}
	}

	public synchronized void release() {
		Assert(mUsers == 1);
		--mUsers;
		mCameraDevice.stopPreview();
		releaseCamera();
	}

	private synchronized void releaseCamera() {
		Assert(mUsers == 0);
		Assert(mCameraDevice != null);
		long now = System.currentTimeMillis();
		if (now < mKeepBeforeTime) {
			mHandler.sendEmptyMessageDelayed(RELEASE_CAMERA, mKeepBeforeTime
					- now);
			return;
		}
		mCameraDevice.release();
		mCameraDevice = null;
	}

	public synchronized void keep() {
		// We allow (mUsers == 0) for the convenience of the calling activity.
		// The activity may not have a chance to call open() before the user
		// choose the menu item to switch to another activity.
		Assert(mUsers == 1 || mUsers == 0);
		// Keep the camera instance for 3 seconds.
		mKeepBeforeTime = System.currentTimeMillis() + 3000;
	}
}
