/*
 * Copyright (C) 2010 ZXing authors
 *
 * 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.ggxiaozhi.zxing.zxing.camera;

import android.os.IBinder;
import android.util.Log;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * This class is used to activate the weak light on some camera phones (not flash)
 * in order to illuminate surfaces for scanning. There is no official way to do this,
 * but, classes which allow access to this function still exist on some devices.
 * This therefore proceeds through a great deal of reflection.
 *
 * See <a href="http://almondmendoza.com/2009/01/05/changing-the-screen-brightness-programatically/">
 * http://almondmendoza.com/2009/01/05/changing-the-screen-brightness-programatically/</a> and
 * <a href="http://code.google.com/p/droidled/source/browse/trunk/src/com/droidled/demo/DroidLED.java">
 * http://code.google.com/p/droidled/source/browse/trunk/src/com/droidled/demo/DroidLED.java</a>.
 * Thanks to Ryan Alford for pointing out the availability of this class.
 */
final class FlashlightManager
{
	private static final String TAG = FlashlightManager.class.getSimpleName();

	private static final Object iHardwareService;
	private static final Method setFlashEnabledMethod;
	static
	{
		iHardwareService = getHardwareService();
		setFlashEnabledMethod = getSetFlashEnabledMethod(iHardwareService);
		if (iHardwareService == null)
		{
			Log.v(TAG, "This device does supports control of a flashlight");
		}
		else
		{
			Log.v(TAG, "This device does not support control of a flashlight");
		}
	}

	private FlashlightManager()
	{
	}

	private static Object getHardwareService()
	{
		Class<?> serviceManagerClass = maybeForName("android.os.ServiceManager");
		if (serviceManagerClass == null)
		{
			return null;
		}

		Method getServiceMethod = maybeGetMethod(serviceManagerClass, "getService", String.class);
		if (getServiceMethod == null)
		{
			return null;
		}

		Object hardwareService = invoke(getServiceMethod, null, "hardware");
		if (hardwareService == null)
		{
			return null;
		}

		Class<?> iHardwareServiceStubClass = maybeForName("android.os.IHardwareService$Stub");
		if (iHardwareServiceStubClass == null)
		{
			return null;
		}

		Method asInterfaceMethod = maybeGetMethod(iHardwareServiceStubClass, "asInterface", IBinder.class);
		if (asInterfaceMethod == null)
		{
			return null;
		}

		return invoke(asInterfaceMethod, null, hardwareService);
	}

	private static Method getSetFlashEnabledMethod(Object iHardwareService)
	{
		if (iHardwareService == null)
		{
			return null;
		}
		Class<?> proxyClass = iHardwareService.getClass();
		return maybeGetMethod(proxyClass, "setFlashlightEnabled", boolean.class);
	}

	private static Class<?> maybeForName(String name)
	{
		try
		{
			return Class.forName(name);
		}
		catch (ClassNotFoundException cnfe)
		{
			// OK
			return null;
		}
		catch (RuntimeException re)
		{
			Log.w(TAG, "Unexpected error while finding class " + name, re);
			return null;
		}
	}

	private static Method maybeGetMethod(Class<?> clazz, String name, Class<?>... argClasses)
	{
		try
		{
			return clazz.getMethod(name, argClasses);
		}
		catch (NoSuchMethodException nsme)
		{
			// OK
			return null;
		}
		catch (RuntimeException re)
		{
			Log.w(TAG, "Unexpected error while finding method " + name, re);
			return null;
		}
	}

	private static Object invoke(Method method, Object instance, Object... args)
	{
		try
		{
			return method.invoke(instance, args);
		}
		catch (IllegalAccessException e)
		{
			Log.w(TAG, "Unexpected error while invoking " + method, e);
			return null;
		}
		catch (InvocationTargetException e)
		{
			Log.w(TAG, "Unexpected error while invoking " + method, e.getCause());
			return null;
		}
		catch (RuntimeException re)
		{
			Log.w(TAG, "Unexpected error while invoking " + method, re);
			return null;
		}
	}

	static void enableFlashlight()
	{
		setFlashlight(true);
	}

	static void disableFlashlight()
	{
		setFlashlight(false);
	}

	private static void setFlashlight(boolean active)
	{
		if (iHardwareService != null)
		{
			invoke(setFlashEnabledMethod, iHardwareService, active);
		}
	}

}