#include <linux/module.h> // Needed by all modules
#include <linux/kernel.h> // for KERN_INFO
#include <linux/sched.h>  // for_each_process, pr_info
#include <linux/syscalls.h> // for SYSCALL_DEFINE<n>
#include <linux/sched/signal.h> // for "for_each_process"
#include <asm/current.h> // for get_current(), current macro
#include <asm/uaccess.h> // for copy_to_user, copy_from_user

struct proc_info
{
	pid_t pid;
	char name[16];
};

struct procinfos
{
	long studentID;
	struct proc_info proc;
	struct proc_info parent_proc;
	struct proc_info oldest_child_proc;
};

void charcpy(char *_dest, const char *_src);

void printProc(struct procinfos *info);

SYSCALL_DEFINE2(get_proc_info, pid_t, pid, struct procinfos *, info)
{
	struct task_struct *process = NULL, *child_process = NULL;
	struct procinfos k_info;
	
	k_info.studentID = 1814015;
	printk("\n\n******************************\n");
	if (pid == -1)
	{
		printk("PID = -1 passed sucessfully!\n");
		pid = current->pid;
	}
	
	// We have 'current' macro and we can speed up some but, I'm too lazy for that.
	for_each_process(process)
	{
		if (process->pid == pid)
		{
			k_info.proc.pid = process->pid;
			charcpy(k_info.proc.name,process->comm);

			// PARENT
			if (process->real_parent == NULL)
			{
				k_info.parent_proc.pid = 0;
				charcpy(k_info.parent_proc.name,"\0");
			}
			else
			{
				k_info.parent_proc.pid = process->real_parent->pid;
				charcpy(k_info.parent_proc.name, process->real_parent->comm);
			}

			// CHILD
			child_process = list_first_entry_or_null(&process->children, struct task_struct, sibling);

			if (child_process == NULL)
			{
				k_info.oldest_child_proc.pid = 0;
				charcpy(k_info.oldest_child_proc.name,"\0");
			}
			else
			{
				k_info.oldest_child_proc.pid = child_process->pid;
				charcpy(k_info.oldest_child_proc.name,child_process->comm);
			}

			// copy_to_user(void __user *to, const void *from, unsigned long n)
			printProc(&p_info);
			printk("\n\n******************************\n\n");
			copy_to_user(info,&p_info,sizeof(struct procinfos));
			return 0;
		}
	}
	printk("No proccess with pid = %d",pid);
	printk("\n\n******************************\n\n");
	return EINVAL;
}


void charcpy(char *_dest, const char *_src)
{
	int i = 0;
	while (_src[i] != '\0' && i < 15)
	{
		_dest[i] = _src[i];
		i++;
	}

	_dest[i] = '\0';
}

void printProc(struct procinfos *info)
{
	printk("%ld\n", info->studentID);
	printk("Process id : %d, process \'s name : %s\n", info->proc.pid, info->proc.name);
	printk("Parent process id : %d, process \'s name : %s\n", info->parent_proc.pid, info->parent_proc.name);
	printk("Child process id : %d, process \'s name : %s\n", info->oldest_child_proc.pid, info->oldest_child_proc.name);
}