#include<stdio.h>
#include<stdlib.h>
typedef struct data
{
    int a;
    char ch[20];
    struct data *next,*prev;
} data;

data *head=NULL,*tail=NULL;


int main()
{
    printf("__________Doubly Linked List__________\n");
    menu();
    return 0;
}


void menu()
{
    printf("\n1. Add\n");
    printf("2. Search\n");
    printf("3. Delete\n");
    printf("4. Display\n");
    printf("5. Exit\n");
    printf("Choose any option : ");
    int a;
    scanf("%d",&a);
    switch(a)
    {
    case 1:
    {
        add();
        break;
    }
    case 2:
    {
        search();
        break;
    }
    case 3:
    {
        Delete();
        break;
    }
    case 4:
    {
        display();
        break;
    }
    case 5:
    {
        exit(0);
        break;
    }
    default:
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void insert_at_first()
{
    data *N=(data*)malloc(sizeof(data));
    printf("\nEnter Student Name : ");
    scanf(" %[^\n]",N->ch);
    printf("Enter Semester : ");
    scanf(" %d",&N->a);
    N->next=NULL;
    N->prev=NULL;
    if(head==NULL && tail==NULL)
    {
        head=N;
        tail=N;
    }
    else
    {
        head->prev=N;
        N->next=head;
        head=N;
    }
    printf("\n1. Menu\n");
    printf("2. Exit\n");
    printf("Choose any option : ");
    int b;
    scanf("%d",&b);
    switch(b)
    {
    case 1:
    {
        menu();
        break;
    }
    case 2:
    {
        exit(0);
        break;
    }
    default:
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void insert_at_end()
{
    data *N=(data*)malloc(sizeof(data));
    printf("\nEnter Student Name : ");
    scanf(" %[^\n]",N->ch);
    printf("Enter Semester : ");
    scanf(" %d",&N->a);
    N->next=NULL;
    N->prev=NULL;
    data *list=head;
    if(head==NULL && tail==NULL)
    {
        head=N;
        tail=N;
    }
    else
    {
        tail->next=N;
        N->prev=tail;
        tail=N;
    }
    printf("\n1. Menu\n");
    printf("2. Exit\n");
    printf("Choose any option : ");
    int c;
    scanf("%d",&c);
    switch(c)
    {
    case 1:
    {
        menu();
        break;
    }
    case 2:
    {
        exit(0);
        break;
    }
    default:
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void insert_at_nth()
{
    int p;
    data *list=head;
    data *N=(data*)malloc(sizeof(data));
    printf("\nEnter Student Name : ");
    scanf(" %[^\n]",N->ch);
    printf("Enter Semester : ");
    scanf(" %d",&N->a);
    N->next=NULL;
    N->prev=NULL;
    printf("Enter Nth Position : ");
    scanf(" %d",&p);
    if(p==1 )
    {
        if(head==NULL)
        {
            head=N;
            tail=N;
        }
        else
        {
            head->prev=N;
            N->next=head;
            head=N;
        }
    }
    else
    {
        p=p-2;
        while(p!=0 && list->next!=NULL)
        {
            list=list->next;
            p--;
        }
        if(list->next==NULL)
        {
            N->prev=tail;
            tail->next=N;
            tail=N;
        }
        else
        {
            list->next->prev=N;
            N->next=list->next;
            N->prev=list;
            list->next=N;
        }
    }
    printf("\n1. Menu\n");
    printf("2. Exit\n");
    printf("Choose any option : ");
    int d;
    scanf("%d",&d);
    switch(d)
    {
    case 1:
    {
        menu();
        break;
    }
    case 2:
    {
        exit(0);
        break;
    }
    default:
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void add()
{
    printf("\n1. Add at frist\n");
    printf("2. Add at end\n");
    printf("3. Add by position\n");
    printf("4. Exit\n");
    printf("Choose any option : ");
    int e;
    scanf("%d",&e);
    switch(e)
    {
    case 1:
    {
        insert_at_first();
        break;
    }
    case 2:
    {
        insert_at_end();
        break;
    }
    case 3:
    {
        insert_at_nth();
        break;
    }
    case 4:
    {
        exit(0);
        break;
    }
    default :
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void search_by_pos()
{
    data *list=head;
    int p;
    printf("\nEnter Nth Position : ");
    scanf("%d",&p);
    if(p==1)
    {
        printf("\nName : %s\n",list->ch);
        printf("Semester : %d\n\n",list->a);
    }
    else
    {
        p=p-2;
        while(p!=0 && list->next!=NULL)
        {
            list=list->next;
            p--;
        }
        if(list->next==NULL)
        {
            printf("\nNo Information Available!\n");
        }
        else
        {
            printf("\nName : %s\n",list->next->ch);
            printf("Semester : %d\n",list->next->a);
        }
    }
    printf("\n1. Menu\n");
    printf("2. Exit\n");
    printf("Choose any option : ");
    int f;
    scanf("%d",&f);
    switch(f)
    {
    case 1:
    {
        menu();
        break;
    }
    case 2:
    {
        exit(0);
        break;
    }
    default :
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void search_by_value()
{
    data *list=head;
    int n;
    printf("\nEnter Semester : ");
    scanf("%d",&n);
    if(list->a==n)
    {
        printf("\nName : %s\n",list->ch);
        printf("Semester : %d\n\n",list->a);
    }
    else
    {
        while(list->a!=n)
        {
            list=list->next;
            if(list==NULL)
            {
                printf("\nNo Information Available!\n");
                break;
            }
        }
        printf("\nName : %s\n",list->ch);
        printf("Semester : %d\n",list->a);
    }
    printf("\n1. Menu\n");
    printf("2. Exit\n");
    printf("Choose a option : ");
    int g;
    scanf("%d",&g);
    switch(g)
    {
    case 1:
    {
        menu();
        break;
    }
    case 2:
    {
        exit(0);
        break;
    }
    default :
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void search()
{
    printf("\n1. Search by Position\n");
    printf("2. Search by Value\n");
    printf("Choose any option : ");
    int h;
    scanf("%d",&h);
    switch(h)
    {
    case 1:
    {
        search_by_pos();
        break;
    }
    case 2:
    {
        search_by_value();
        break;
    }
    case 3:
    {
        exit(0);
        break;
    }
    default :
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void delete_by_pos()
{
    int p;
    data *list=head,*temp;
    printf("\nEnter Nth Position : ");
    scanf(" %d",&p);
    if(head==NULL)
    {
        printf("\nNo Information Available!\n");
    }
    else if(p==1)
    {
        if(list->next==NULL)
        {
            printf("\nDELETED!\n");
            free(list);
        }
        else
        {
            head=list->next;
            head->prev=NULL;
            printf("\nDELETED!\n");
            free(list);
        }
    }
    else
    {
        p=p-2;
        while(p!=0 && list->next!=NULL)
        {
            list=list->next;
            p--;
            if(list==NULL)
            {
                printf("\nNo Information Available!\n");
                break;
            }
        }
        if(list->next==NULL)
        {
            printf("\nPLEASE ENTER A VALID OPTION!\n");
        }
        else if(list->next->next==NULL && p==0)
        {
            temp=tail;
            tail=tail->prev;
            tail->next=NULL;
            printf("\nDELETED!\n");
            free(temp);
        }
        else if(list->next->next!=NULL && p==0)
        {
            temp=list->next;
            temp->next->prev=list;
            list->next=temp->next;
            printf("\nDELETED!\n");
            free(temp);
        }
    }
    printf("\n1. Menu\n");
    printf("2. Exit\n");
    printf("Choose any option : ");
    int i;
    scanf("%d",&i);
    switch(i)
    {
    case 1:
    {
        menu();
        break;
    }
    case 2:
    {
        exit(0);
        break;
    }
    default :
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void  delete_by_value()
{
    int x;
    printf("\nEnter Semester : ");
    scanf(" %d",&x);
    data *list=head;
    if(head==NULL)
    {
        printf("\nNo Information Available!\n");
    }
    else if(list->a==x)
    {
        if(list->next==NULL)
        {
            head=NULL;
            tail=NULL;
            printf("\nDELETED!\n");
            free(list);
        }
        else
        {
            list->next->prev=NULL;
            head=list->next;
            printf("\nDELETED!\n");
            free(list);
        }
    }
    else
    {
        data *temp;
        while(list->a!=x && list->next!=NULL)
        {
            list=list->next;
            if(list==NULL)
            {
                printf("\nNo Information Available!\n");
                break;
            }
        }
        if(list->a==x && list->next==NULL)
        {
            list=tail;
            temp=list;
            temp->prev->next=temp->next;
            tail=temp->prev;
            printf("\nDELETED!\n");
            free(temp);
        }
        else if(list->a==x && list->next!=NULL)
        {
            temp=list;
            temp->prev->next=temp->next;
            temp->next->prev=temp->prev;
            temp->next=NULL;
            temp->prev=NULL;
            printf("\nDELETED!\n");
            free(temp);
        }
    }
    printf("\n1. Menu\n");
    printf("2. Exit\n");
    printf("Choose a option : ");
    int j;
    scanf("%d",&j);
    switch(j)
    {
    case 1:
    {
        menu();
        break;
    }
    case 2:
    {
        exit(0);
        break;
    }
    default :
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void Delete()
{
    printf("\n1. Delete by Position\n");
    printf("2. Delete by Value\n");
    printf("Choose a option : ");
    int k;
    scanf("%d",&k);
    switch(k)
    {
    case 1:
    {
        delete_by_pos();
        break;
    }
    case 2:
    {
        delete_by_value();
        break;
    }
    case 3:
    {
        exit(0);
        break;
    }
    default :
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void display_first()
{
    data *list=head;
    if(head==NULL)
    {
        printf("\nNo Information Available!\n");
    }
    else
    {
        while(list!=NULL)
        {
            printf("\nName : %s\n",list->ch);
            printf("Semester : %d\n\n",list->a);
            list=list->next;
        }
    }
    printf("\n1. Menu\n");
    printf("2. Exit\n");
    printf("Choose a option : ");
    int l;
    scanf("%d",&l);
    switch(l)
    {
    case 1:
    {
        menu();
        break;
    }
    case 2:
    {
        exit(0);
        break;
    }
    default :
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void display_last()
{
    data *list=tail;
    if(head==NULL)
    {
        printf("\nNo Information Available!\n");
    }
    else
    {
        while(list!=NULL)
        {
            printf("\nName : %s\n",list->ch);
            printf("Semester : %d\n\n",list->a);
            list=list->prev;
        }
    }
    printf("\n1. Menu\n");
    printf("2. Exit\n");
    printf("Choose a option : ");
    int m;
    scanf("%d",&m);
    switch(m)
    {
    case 1:
    {
        menu();
        break;
    }
    case 2:
    {
        exit(0);
        break;
    }
    default:
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}


void display()
{
    printf("\n1. Display first to last\n");
    printf("2. Display last to first\n");
    printf("Choose a option : ");
    int n;
    scanf("%d",&n);
    switch(n)
    {
    case 1:
    {
        display_first();
        break;
    }
    case 2:
    {
        display_last();
        break;
    }
    default:
    {
        printf("\nPLEASE ENTER A VALID OPTION!\n");
        menu();
        break;
    }
    }
}