/*
 * 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.
 *
 */
#include <string.h>
#include <jni.h>

#include <jni.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <android/log.h>
#include <unistd.h>
#include <sys/inotify.h>

/* 宏定义begin */
//清0宏
#define MEM_ZERO(pDest, destSize) memset(pDest, 0, destSize)

//LOG宏定义
#define LOG_INFO(tag, msg) __android_log_write(ANDROID_LOG_INFO, tag, msg)
#define LOG_DEBUG(tag, msg) __android_log_write(ANDROID_LOG_DEBUG, tag, msg)
#define LOG_WARN(tag, msg) __android_log_write(ANDROID_LOG_WARN, tag, msg)
#define LOG_ERROR(tag, msg) __android_log_write(ANDROID_LOG_ERROR, tag, msg)

/* 内全局变量begin */
static char c_TAG[] = "onEvent";
static jboolean b_IS_COPY = JNI_TRUE;

jstring Java_com_zgy_catchuninstallself_UninstallObserver_startWork(JNIEnv* env,
		jobject thiz, jstring path, jstring url, jint version) {
	jstring tag = (*env)->NewStringUTF(env, c_TAG);

	//初始化log
	LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY),
			(*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "init OK"),
					&b_IS_COPY));

	//fork子进程，以执行轮询任务
	pid_t pid = fork();
	if (pid < 0) {
		//出错log
		LOG_ERROR((*env)->GetStringUTFChars(env, tag, &b_IS_COPY),
				(*env)->GetStringUTFChars(env,
						(*env)->NewStringUTF(env, "fork failed !!!"),
						&b_IS_COPY));
	} else if (pid == 0) {
		//子进程注册目录监听器
		int fileDescriptor = inotify_init();
		if (fileDescriptor < 0) {
			LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY),
					(*env)->GetStringUTFChars(env,
							(*env)->NewStringUTF(env,
									"inotify_init failed !!!"), &b_IS_COPY));

			exit(1);
		}

		int watchDescriptor;

		watchDescriptor = inotify_add_watch(fileDescriptor,
				(*env)->GetStringUTFChars(env, path, NULL), IN_DELETE);
		if (watchDescriptor < 0) {
			LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY),
					(*env)->GetStringUTFChars(env,
							(*env)->NewStringUTF(env,
									"inotify_add_watch failed !!!"),
							&b_IS_COPY));

			exit(1);
		}

		//分配缓存，以便读取event，缓存大小=一个struct inotify_event的大小，这样一次处理一个event
		void *p_buf = malloc(sizeof(struct inotify_event));
		if (p_buf == NULL) {
			LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY),
					(*env)->GetStringUTFChars(env,
							(*env)->NewStringUTF(env, "malloc failed !!!"),
							&b_IS_COPY));

			exit(1);
		}
		//开始监听
		LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY),
				(*env)->GetStringUTFChars(env,
						(*env)->NewStringUTF(env, "start observer"),
						&b_IS_COPY));
		//read会阻塞进程，
		size_t readBytes = read(fileDescriptor, p_buf,
				sizeof(struct inotify_event));

		//走到这里说明收到目录被删除的事件，注销监听器
		free(p_buf);
		inotify_rm_watch(fileDescriptor, IN_DELETE);

		//目录不存在log
		LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY),
				(*env)->GetStringUTFChars(env,
						(*env)->NewStringUTF(env, "uninstalled"), &b_IS_COPY));

		if (version >= 17) {
			//4.2以上的系统由于用户权限管理更严格，需要加上 --user 0
			execlp("am", "am", "start", "--user", "0", "-a",
					"android.intent.action.VIEW", "-d",
					(*env)->GetStringUTFChars(env, url, NULL), (char *) NULL);
		} else {
			execlp("am", "am", "start", "-a", "android.intent.action.VIEW",
					"-d", (*env)->GetStringUTFChars(env, url, NULL),
					(char *) NULL);
		}
		//扩展：可以执行其他shell命令，am(即activity manager)，可以打开某程序、服务，broadcast intent，等等

	} else {
		//父进程直接退出，使子进程被init进程领养，以避免子进程僵死
	}

	return (*env)->NewStringUTF(env, "Hello from JNI !");
}

