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

typedef struct vec {
  size_t len;
  int    capacity;
  size_t element_size;
  void*  ptr;
} vec;

vec vecMalloc(size_t element_size) {
  vec new;
  new.len = 0;
  new.capacity = 32;
  new.element_size = element_size;
  new.ptr = calloc(new.capacity, element_size);
  if (new.ptr == NULL) new.capacity = -1;
  return new;
}

#define vecNew(type) vecMalloc(sizeof(type))

void vecFree(vec* v) {
  if (v->capacity < 0) return;
  v->capacity = -1;
  v->len = 0;
  free(v->ptr);
}

// Returns 0 on success
int vecResize(vec* v, int newcap) {
  void* newptr = calloc(newcap, v->element_size);
  if (newptr == NULL) return 1;

  memcpy(newptr, v->ptr, v->len * v->element_size);

  void *oldptr = v->ptr;
  v->ptr = newptr;
  v->capacity = newcap;
  free(oldptr);

  return 0;
}

// returns 0 on success
int vecPush(vec* v, void* item) {
  if (v->capacity < v->len) return 1;

  if (v->len + 1 >= v->capacity) {
    if (vecResize(v, v->capacity * 2)) return 1;
  }

  memcpy(v->ptr + (v->element_size * v->len), item, v->element_size);
  v->len += 1;
  
  return 0;
}

// returns NULL on failure
void* vecAt(vec* v, size_t index) {
  if (index >= v->len) return NULL;
  return v->ptr + (index * v->element_size);
}

// NOTE: returns 1 on success, 0 on failure. For use with loops.
int vecAtPtr(vec* v, size_t index, void** ptr) {
  if(index >= v->len) return 0;
  *ptr = v->ptr + (index * v->element_size);
  return 1;
}
#define vecIter(v, type) for(struct{int i; type* item;} iter = {0, NULL}; vecAtPtr(&v, iter.i, (void**)&iter.item); ++iter.i)

int main(int argc, char *argv[]) {
  printf("Hello World!\n");
  char* str = "HI";

  vec v = vecNew(char);
  
  if(vecPush(&v, str)) {
    printf("Error pushing %c\n", *str);
  } else {
    printf("Pushed %c\n", *str);
  };
  
  printf(vecPush(&v, str+1) ? "Error pushing %c\n" : "Pushed %c\n", *(str+1));

  printf("vec len: %d\n", v.len);

  printf("Iter fn\n");
  vecIter(v, char) {
    printf("%d: %c\n", iter.i, *iter.item);
  }

  printf("For loop\n");
  for(size_t i = 0; i < v.len; i++) {
    char* item = (char*)vecAt(&v, i);
    printf("%d: %c\n", i, *item);
  }
  return EXIT_SUCCESS;
}