#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct node
{
	char ssn[20], name[20], dept[10], desg[10];
	int sal;
	long int phno;
	struct node *rlink;
	struct node *llink;
};
typedef struct node* NODE;
NODE first=NULL;
int count=NULL;

NODE createEmployeeNode()
{

	NODE employee;
	employee=(NODE)malloc(sizeof(struct node));

	if(employee==NULL)
	{
		printf("Out of Memory\n");
		exit(0);
	}
	employee->rlink=NULL;
	employee->llink=NULL;

	char ssn[20], name[20], dept[10], desg[10];
	int sal;
	long int phno;

	printf("Enter SSN:\t");
	scanf("%s", &ssn);
	printf("Enter Name:\t");
	scanf("%s", &name);
	printf("Enter Department:\t");
	scanf("%s", &dept);
	printf("Enter Designation:\t");
	scanf("%s",&desg);
	printf("Enter Salary:\t");
	scanf("%d", &sal);
	printf("Enter Phone Number:\t");
	scanf("%ld", &phno);

	strcpy(employee->ssn, ssn);
	strcpy(employee->name, name);
	strcpy(employee->dept, dept);
	strcpy(employee->desg, desg);

	employee->sal=sal;
	employee->phno=phno;

	count++;
	return employee;
}

NODE insert_front()
{
	NODE temp;
	temp=createEmployeeNode();

	if(first==NULL)
	{
		return temp;
	}

	temp->rlink=first;
	first->llink=temp;

	return temp;
}

NODE insert_end()
{
	NODE cur, temp;
	temp=createEmployeeNode();

	if(first==NULL)
	{
		return temp;
	}
	cur=first;
	while(cur->rlink!=NULL)
	{
		cur=cur->rlink;
	}
	cur->rlink=temp;
	temp->llink=cur;

	temp->rlink=NULL;

	return first;



}

NODE del_front()
{
	NODE temp;

	if(first==NULL)
	{
		printf("List is empty!\n");
		return NULL;
	}

	if(first->rlink==NULL)
	{
		printf("The employee record with ssn number %d has been deleted\n", first->ssn );
		free(first);
		count--;
		return NULL;
	}

	temp=first;
	temp->rlink=NULL;
	first->llink=NULL;
	printf("The employee record with ssn number %d has been deleted\n", temp->ssn );
	free(temp);
	count--;

	return first;

}

NODE del_end()
{
	NODE prev, cur, temp;

	if(first==NULL)
	{
		printf("List is empty\n");
		return NULL;
	}

	if(first->rlink==NULL)
	{
		printf("The employee record with ssn number %d has been deleted\n", first->ssn );
		free(first);
		count--;
		return NULL;
	}

	prev=NULL;
	cur=first;

	while(cur->rlink!=NULL)
	{
		prev=cur;
		cur=cur->rlink;
	}

	cur->llink=NULL;
	prev->rlink=NULL;

	count--;
	return first;

}

void display()
{
	NODE cur;

	if(first==NULL)
	{
		printf("The list is empty\n");
	}

	cur=first;
	printf("The contents of the list are");
	while(cur!=NULL)
	{
		printf("SSN: %s| Name: %s| Department: %s| Designation: %s| Salary: %d| Phone: %ld",cur->ssn, cur->name, cur->dept, cur->desg, cur->sal, cur->phno);
		cur=cur->rlink;
	}
	printf("The number of employees: %d",count);

}

void main()
{
	int ch,i,n;
	while(1)
	{
		printf("\t---Menu---\n");
		printf("1. Create DLL of employee\n");
		printf("2. Display\n");
		printf("3. Insert at Front\n");
		printf("4. Insert at End\n");
		printf("5. Delete at front\n");
		printf("6. Delete at end\n");
		printf("7. Exit\n");

		printf("Enter your choice:\t");
		scanf("%d",&ch);

		switch(ch)
		{
			case 1: printf("Enter the number of employees!\n");
					scanf("%d",&n);
					for(i=0; i<n; i++)
						first=insert_end();
					break;

			case 2: display();
					break;
			case 3: first=insert_front();
					break;
			case 4: first=insert_end();
					break;
			case 5: first=del_front();
					break;
			case 6: first=del_end();
					break;
			case 7: exit(0);
					break;
			default: printf("Invalid choice\n");
					break;

		}


	}
}