#ifndef VEC_TYPE
#error "Need vector type"
#endif

#ifndef VEC_NAME
#error "Need vector name"
#endif

#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#define UNDERSCORE2(a, b) a##_##b
#define UNDERSCORE(a, b) UNDERSCORE2(a, b)
#define VEC(n) UNDERSCORE(VEC_NAME, n)


#define VEC_STRUCT VEC_NAME
struct VEC_STRUCT {
	size_t n;
	size_t s;
	VEC_TYPE *buf;
};

#ifndef VEC_H
#define VEC_H

#define foreach_vec(iter, v) \
	for (size_t iter = 0; iter < (v).n; ++iter)

#define vec_uninit(v) \
	(v.buf == NULL)
#endif

static inline struct VEC_STRUCT VEC(create)()
{
	const size_t s = 8;
	return (struct VEC_STRUCT) {
		       .n = 0,
		       .s = s,
		       .buf = malloc(s * sizeof(VEC_TYPE)),
	};
}

static inline size_t VEC(len)(struct VEC_STRUCT *v)
{
	return v->n;
}

static inline VEC_TYPE *VEC(at)(struct VEC_STRUCT *v, size_t i)
{
	assert(i < v->n && "out of vector bounds");
	return &v->buf[i];
}

static inline VEC_TYPE *VEC(back)(struct VEC_STRUCT *v)
{
	assert(v->n);
	return &v->buf[v->n - 1];
}

static inline VEC_TYPE *VEC(pop)(struct VEC_STRUCT *v)
{
	assert(v->n && "attempting to pop empty vector");
	v->n--;
	return &v->buf[v->n];
}

static inline void VEC(append)(struct VEC_STRUCT *v, VEC_TYPE n)
{
	v->n++;
	if (v->n >= v->s) {
		v->s *= 2;
		v->buf = realloc(v->buf, v->s * sizeof(VEC_TYPE));
		assert(v->buf);
	}

	v->buf[v->n - 1] = n;
}

static inline void VEC(reset)(struct VEC_STRUCT *v)
{
	v->n = 0;
}

static inline void VEC(destroy)(struct VEC_STRUCT *v) {
	free(v->buf);
}

typedef int (*vec_comp_t)(void *a, void *b);
static inline void VEC(sort)(struct VEC_STRUCT *v, vec_comp_t comp)
{
	qsort(v->buf, v->n, sizeof(VEC_TYPE), (__compar_fn_t)comp);
}

static inline void VEC(reserve)(struct VEC_STRUCT *v, size_t n)
{
	if (v->n >= n)
		return;

	v->n = n;
	if (v->s >= v->n)
		return;

	while (v->s < v->n)
		v->s *= 2;

	v->buf = realloc(v->buf, v->s * sizeof(VEC_TYPE));
}

static inline void VEC(shrink)(struct VEC_STRUCT *v, size_t n)
{
	/* assert(v->n >= n); */
	v->n = n;
}

#undef VEC_TYPE
#undef VEC_NAME