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

struct node {
    int value;
    struct node *next;
};

struct node *start=NULL;

struct node *sll_new_node() {
    struct node *new_node;

    new_node = (struct node*) malloc(sizeof(struct node));
    if(new_node == NULL) {
        printf("Out of Memory\n");
        exit(1);
    }

    return new_node;
}

void sll_insert_first(int value) {
    struct node *new_node;

    new_node = sll_new_node();

    new_node->value = value;
    new_node->next = start;
    start = new_node;
}

void sll_insert_last(int value) {
    struct node *new_node;

    new_node = sll_new_node(); // creates new node

    new_node->value = value; // sets the new node's value
    new_node->next = NULL; // sets the next node's value to NULL

    if(start == NULL) { // if no node to start
        start = new_node;
    } else {
        struct node *temp;

        temp = start; // set temp to start
        while(temp->next != NULL) { // loop until temp is at the last node
            temp = temp->next; // set temp to next until loop finishes
        }
        temp->next = new_node; // set the next node after temp (last) to the new_node
    }
}

void sll_insert_at(int position, int value) {

    if(start == NULL || position == 0) {
        sll_insert_first(value);
    } else {
        struct node *new_node;
        int i;

        new_node = sll_new_node();
        new_node->value = value;

        struct node *temp;
        temp = start;
        while(i != position-1) { // loop until i = position-1
            if(temp->next == NULL) { // if it reaches last node
                sll_insert_last(value);
                return;
            } else {
                temp = temp->next; // set temp to the next node until...
                i++;
            }
        }
        new_node->next = temp->next; //set the next node of new_node to the next node of temp
        temp->next = new_node; // set the next node of temp to the new node
    }
}

void sll_delete_first() {
    struct node *deleted_node;

    if(start == NULL) { // if no node to delete
        printf("No node to delete\n");
    } else {
        deleted_node = start; // set deleted_node to first node
        start = start->next; // set the next node to start
        free(deleted_node); // remove the first node
    }
}

void sll_delete_last() {

    if(start == NULL) { // if no node to delete
            printf("No node to delete\n");
    } else {
        if(start->next == NULL) { // if only one node
            sll_delete_first();
        } else {

            struct node *deleted_node;
            struct node *new_last_node;

            deleted_node = start; // set deleted_node to start
            while(deleted_node->next != NULL) {
                new_last_node = deleted_node; // set new_last_node to node before last
                deleted_node = deleted_node->next; // set deleted_node to last node
            }
            new_last_node->next = NULL; // set new_last_node to NULL (end of list)
            free(deleted_node);  // remove deleted_node (last node)
        }
    }
}

void sll_delete_at(int position) {
    int i;
    if(start == NULL) { // if no node to delete
        printf("No node to delete\n");
    } else {
        if(start->next == NULL || position == 0) { // if only one node or position == 0
            sll_delete_first();
        } else {
            struct node *deleted_node;
            struct node *temp;

            deleted_node = start; // set deleted_node to start
            while(i != position) { // loop until i = position-1
                if(deleted_node->next == NULL) { // if it reaches last node
                    sll_delete_last();
                    return;
                } else {
                    temp = deleted_node; // set temp to deleted_node
                    deleted_node = deleted_node->next; // set deleted_node to the next node until...
                    i++;
                }
            }
            temp->next = deleted_node->next; //set the next node of temp to the next node of deleted_node
            free(deleted_node);
        }
    }
}

void sll_delete_value(int value) {
    if(start == NULL) { // if no node to delete
            printf("No node to delete\n");
    } else {
        if(start->next == NULL) { // if only one node
            sll_delete_first();
        } else {
            struct node *temp;
            int i = 0;

            temp = start;

            while(temp != NULL) {
                if(temp->value == value) {
                    sll_delete_at(i);
                    return;
                } else {
                    i++;
                    temp = temp->next;
                }
            }
            printf("Value (%d) not found!\n", value);
        }
    }
}

void sll_print_list() {
    struct node *temp;

    temp = start;

    while(temp != NULL) {
        printf("%d ", temp->value);
        temp = temp->next;
    }

    printf("\n");
}

void sll_print_at(int position) {
    struct node *temp;
    int i;

    if(start == NULL) { // if no node to print
        printf("No node to print\n");
    } else {

        temp = start; // set temp to first

        while(i != position) { // loop until i = position
            if(temp->next == NULL) { // if it reaches last node
                printf("No existing node on that position!");
                exit(1);
            } else {
                temp = temp->next; // set temp to the next node
                i++;
            }
        }
        printf("Position (%d) value: %d \n", position, temp->value);
    }
}

void sll_count() {
    struct node *temp;
    int i = 0;

    temp = start;

    while(temp != NULL) {
        i++;
        temp = temp->next;
    }

    printf("\nCount of Linked Lists: %d", i);
}

int main(void) {

    printf("SLL_INSERT_FIRST(10): "); sll_insert_first(10);sll_print_list();
    printf("\nSLL_INSERT_FIRST(20): "); sll_insert_first(20);sll_print_list();
    printf("\nSLL_INSERT_FIRST(30): "); sll_insert_first(30);sll_print_list();
    printf("\nSLL_INSERT_FIRST(40): "); sll_insert_first(40);sll_print_list();
    printf("\nSLL_INSERT_LAST(50): "); sll_insert_last(50); sll_print_list();
    printf("\nSLL_DELETE_FIRST: "); sll_delete_first(); sll_print_list();
    printf("\nSLL_PRINT_AT(3): "); sll_print_at(3);
    printf("\nSLL_INSERT_AT(0, 31): "); sll_insert_at(0, 31); sll_print_list();
    printf("\nSLL_DELETE_AT(0): "); sll_delete_at(0); sll_print_list();
    printf("\nSLL_DELETE_VALUE(50): "); sll_delete_value(50); sll_print_list();
    printf("\nSLL_COUNT(): "); sll_count();



    return 0;
}