/* Function declaration -- Linked list without head pointer */

#include "list.h"

void InitList(List * L)
{
    *L = NULL;
}

void DestroyList(List * L)
{
    List tmp;

    while (*L)
    {
        tmp = (*L)->next;
        free(*L);
        *L = tmp;
    }
}

bool AddElem(List * L, ElemType e)
{
    List scan = *L;
    
    List new = (LNode *) malloc (sizeof(LNode));

    if (!new)
    {
        fprintf(stderr,"Failed Adding element\n");
        return false;
    }

    new->data = e;
    new->next = NULL;

    if (!*L)
        *L = new;
    else
    {
        while (scan->next)
            scan = scan->next;
        scan->next = new;
    }

    return true;
}

bool ListEmpty (List * L)
{
    if (!*L)
        return true;
    return false;
}

int ListLength (List * L)
{
    List tmp = *L;
    int count = 0;
    while (tmp)
    {
        tmp = tmp->next;
        count++;
    }

    return count;
}

ElemType GetElem (List * L, int i)
{
    int n = ListLength(L);
    if (i > n)
    {
        fprintf(stderr,"Position error, Please restricted between 0 and %d",n);
        return EOF;
    }
    List tmp = *L;

    for (int j = 0; j < i; j++)
        tmp = tmp->next;
    
    if (tmp)
        return tmp->data;
    return 0;
}

void TraverseList (List * L)
{
    List tmp = *L;

    while (tmp)
    {
        printf("%7d",tmp->data);
        tmp = tmp->next;
    }
    putchar('\n');
}

bool InsertElem (List * L, ElemType e, int i)
{
    bool flag = false;
    List tmp = *L;
    List new = (LNode *) malloc (sizeof(LNode));

    int n = ListLength(&tmp);

    if (!new)
    {
        fprintf(stderr,"Failed to create new node!\n");
        return flag;
    }

    new->data = e;

    if (i < 1)
        fprintf(stderr,"Invalid position!\n");

    else if (i == 1)
    {
        new->next = tmp;
        *L = new;
        flag = true;
    }

    else
    {
        for (int j = 2; j < i; j++)
            if (tmp->next)
                tmp = tmp->next;
            else
                break;
        
        if (i > n)
            printf("List length is %d, append element to last!\n",n);

        new->next = tmp->next;
        tmp->next = new;
        flag = true;
    }
    return flag;
}

bool DeleteElem (List * L, int i)
{
    List t1 = *L;
    List t2;
    bool flag = false;
    int n = ListLength(&t1);

    if (i < 1)
        fprintf(stderr, "Position error!\n");

    else if (i == 1)
    {
        t2 = t1;
        *L = t1->next;
        free(t2);
        flag = true;
    }

    else if (i <= n)
    {
        for (int j = 2; j < i; j++)
            if (t1->next)
                t1 = t1->next;
            else
                break;
                
        if (t1->next)
        {
            t2 = t1->next;
            t1->next = t2->next;
            free(t2);
            flag = true;
        }
    }

    else
        printf("No element at position %d\n",i);
    return flag;
}