// linked list
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

#include "linked_list.h"


linkedList* createLinkedList() {
    linkedList *list = (linkedList*)malloc(sizeof(linkedList));
    list->head = NULL;
    return list;
}

//insert link at the first location
void insertFirst(linkedList *list, int key, void *data) {
    //create a link
    node *link = (node*) malloc(sizeof(node));
	
    link->key = key;
    link->data = data;
	
    //point it to old first node
    link->next = list->head;
	
    //point first to new first node
    list->head = link;
}

//delete first item
node* deleteFirst(linkedList *list) {
    if (!list->head) {
        return NULL;
    }

    //save reference to first link
    node *tempLink = list->head;
	
    //mark next to first link as first
    list->head = list->head->next;
	
    //return the deleted link
    return tempLink;
}

//find a link with given key
node* find(linkedList *list, int key) {

    //start from the first link
    node* current = list->head;

    //if list is empty
    if(!current) {
        return NULL;
    }

    //navigate through list
    while(current->key != key) {
	
        //if it is last node
        if(!current->next) {
            return NULL;
        } else {
            //go to next link
            current = current->next;
        }
    }
	
    //if data found, return the current Link
    return current;
}

//delete a link with given key
node* deleteElement(linkedList *list, int key) {

    //start from the first link
    node* current = list->head;
    node* previous = NULL;
	
    //if list is empty
    if(!list->head) {
        return NULL;
    }

    //navigate through list
    while(current->key != key) {

        //if it is last node
        if(!current->next) {
            return NULL;
        } else {
            //store reference to current link
            previous = current;
            //move to next link
            current = current->next;
        }
    }

    //found a match, update the link
    if(current == list->head) {
        //change first to point to next link
        list->head = list->head->next;
    } else {
        //bypass the current link
        previous->next = current->next;
    }
	
    return current;
}

//is list empty
bool isEmpty(linkedList *list) {
    return !list->head;
}

int length(linkedList *list) {
    int length = 0;
    node *current;
	
    for(current = list->head; current != NULL; current = current->next) {
        length++;
    }
	
    return length;
}