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

typedef struct Contact{
    struct Contact* next; /*next is used to navigate through structures.*/
    char* name;
    char* tel;

}Contact;



Contact*start; /* start always points to the first node of the linked list.*/




/*Defining of the functions to be implemented*/

Contact* goEnd()
{
    Contact* end = start;
    while(end->next != NULL)
        {
        end = end->next;
        }
    return end;
}

void addFirst(Contact* new_contact )
{
    if(start == NULL)
        {
        start = new_contact;
        start->next = NULL;
        }
        else
        {
         Contact* current = start;
        start = new_contact;
        start->next = current;
        }
}

void addLast(Contact* new_contact)
{

    if(start == NULL){
        start = new_contact;
    }
    else
        {
        goEnd()->next = new_contact;
    }
    new_contact->next = NULL;

}

void removeByName(char*name)
{
    Contact* sel = start;
    Contact** prevNext = &start;
    while(sel != NULL){
        if(sel->name == name)
            {

            *prevNext = sel->next; /*to delete the contact and free the memory occupied*/
            free(sel);
            return;
            }
        else
           {
            prevNext = &sel->next;
            sel = sel->next;
           }
    }
}

void removeFirst()
{
if(start != NULL){
        Contact* ers = start;
        start = start->next;
        free(ers);
    }
}

void removeLast()
{
Contact* head = start;
    Contact** prevNext = &start;
    if(start != NULL){
        while(head->next != NULL){
            prevNext = &head->next;
            head = head->next;
        }
        free(head);
        *prevNext = NULL;
    }
}
void printList() /*Prints out the contact lists*/
{
    Contact* current = start;

    while(current != NULL)
    {
        printf("The Name is: %s - %s\n", current->name, current->tel);
        current = current->next;
    }
    printf("\n\n");
}

void builtList(Contact contacts[])
{
    Contact *ptr=NULL;
    int i;
    for(i=0; i<=6; i++)
    {
        ptr=&contacts[i];
        addLast(ptr);
    }

}

/*Implementation methods*/

int main()
{
    Contact contacts[7]=
    {
        {NULL,"Dennis","0203/123456"},
        {NULL,"Chantal","0177/3123345"},
        {NULL,"Robert","0163/9295986"},
        {NULL,"Bjoern","040 - 123232345"},
        {NULL,"Andreas","+49 178 11903123"},
        {NULL,"Jenny","+41 119 34544345"},
        {NULL,"Zeuss","0162-123-4531698"},
    };

    builtList(contacts);
    printList();
    printf("Removing name Andreas\n");
    removeByName("Andreas");
    printList();
    printf("Removing first\n");
    removeFirst();
    printList();
    printf("Removing last\n");
    removeLast();
    printList();

    return 0;
}