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

typedef struct node {
    void *content;
    struct node *next;
}Node;

typedef struct slist {
    Node *head;
    size_t w;
}SList;

SList *new_slist(size_t w) {
    SList *l = malloc(sizeof(SList));
    l->head = NULL;
    l->w = w;
    return l;
}

bool is_empty(SList *l) {
    return !l->head;
}

void delete_head(SList *l) {
    Node *n = l->head;
    //free(n->content);
    l->head = n->next;
    free(n);
}

void destroy_node(Node *n, Node *prev) {
    //free(n->content);
    prev->next = n->next;
    free(n);
}

void destroy_list(SList *l) {
    while (!is_empty(l))
        delete_head(l);
    free(l);
}

void delete_node(Node *n, SList *l) {
    Node *prev = l->head;
    while (prev && prev->next != n) 
        prev = prev->next;
    if (prev) 
        destroy_node(n, prev);
}

void delete_index(SList *l, int index) {
    Node *prev, *n = l->head;
    for (int i = 0; n && i < index; i++) {
        prev = n;
        n = n->next;
    }
    destroy_node(n, prev);
}

int get_len(SList *l) {
    if (is_empty(l))
        return 0;
    int i = 1;
    Node *n = l->head;
    do {
        n = n->next;
        i++;
    }while(n);
    return i-1;
}

void insert_after(void *content, SList *l, Node *prev) {
    Node *n = malloc(sizeof(Node));
    n->content = content;
    n->next = prev->next;
    prev->next = n;
}

void insert_head(void *content, SList *l) {
    Node *n = malloc(sizeof(Node));
    n->content = content;
    n->next = l->head;
    l->head = n;
}

void insert_empty(void *content, SList *l) {
    insert_head(content, l);
}

void insert(void *content, SList *l, int pos) {
    if (is_empty(l) || !pos) {
        insert_head(content, l);
        return;
    }
    Node *prev = l->head;
    while(pos > 1 && prev) {
        prev = prev->next;
        pos--;
    }
    insert_after(content, l, prev);
}

void append(void *content, SList *l) {
    if (is_empty(l)) {
        insert_empty(content, l);
        return;
    }
    Node *prev = l->head;
    while(prev->next) 
        prev = prev->next;
    insert_after(content, l, prev);
}

Node *find(void *content, SList *l, int (*cmp)(void *a, void *b)) {
    Node *n = l->head;
    while (cmp(n->content, content)) {
        n = n->next;
        if (!n) 
            return NULL;
    }
    return n;
}

void print_list(SList *l, void (*print_content)(void *content)) {
    Node *n = l->head;
    printf("[");
    while(n) {
        print_content(n->content);
        printf(", ");
        n = n->next;
    }
    printf("]\n");
}

void print_content(void *c) {
    printf("%d", *((int *)c));
}

int cmp(void *a, void *b) {
   return *(int *)a - *(int *)b; 
}

int main() {
    SList *l = new_slist(sizeof(int));
    int *a=malloc(sizeof(int)), *b=malloc(sizeof(int)), *c=malloc(sizeof(int)), *d=malloc(sizeof(int));
    *a = 1; *b = 2; *c = 3; *d = 4;
    append(a, l);
    delete_head(l);
    insert(a, l, 0);
    append(b, l);
    insert(c, l, 1);
    insert(d, l, 0);
    append(a, l);
    printf("%d\n", get_len(l));
    destroy_list(l);
    free(a); free(b); free(c); free(d);
}