/*
 * iter.c: special iterators
 *
 * Stephen Brennan <stephen@brennan.io>
 */

#include <stdlib.h>
#include <stddef.h>
#include <stdint.h>

#include "iter.h"

void iterator_close_noop(struct iterator *iter)
{
	(void)iter;
}

static bool sv_has_next(struct iterator *iter)
{
	return iter->index == 0;
}

static void *sv_next(struct iterator *iter)
{
	iter->index++;
	return iter->ds;
}

struct iterator iterator_single_value(void *value)
{
	struct iterator it = {
		.ds=value,
		.index=0,
		.has_next=sv_has_next,
		.next=sv_next,
		.close=iterator_close_noop,
	};
	return it;
}

static bool cc_has_next(struct iterator *iter)
{
	struct iterator *its = iter->ds;
	intptr_t max_iterators = (intptr_t) iter->state_ptr;
	bool has_next;

	while (iter->state_int < max_iterators) {
		has_next = its[iter->state_int].has_next(&its[iter->state_int]);
		if (has_next) {
			return true;
		}

		its[iter->state_int].close(&its[iter->state_int]);
		iter->state_int++;
	}

	return false;
}

static void *cc_next(struct iterator *iter)
{
	struct iterator *its = iter->ds;
	void *result = its[iter->state_int].next(&its[iter->state_int]);
	if (result) {
		iter->index++;
	}
	return result;
}

static void cc_close(struct iterator *iter)
{
	free(iter->ds);
}

struct iterator iterator_concat(struct iterator *its, size_t n)
{
	struct iterator it = {
		.ds = its,
		.index = 0,
		.state_int = 0,
		.state_ptr = (void*) n,

		.has_next = cc_has_next,
		.next = cc_next,
		.close = cc_close,
	};
	return it;
}

struct iterator iterator_concat2(struct iterator left, struct iterator right)
{
	struct iterator *arr = calloc(sizeof(struct iterator), 2);
	arr[0] = left;
	arr[1] = right;
	return iterator_concat(arr, 2);
}

struct iterator iterator_concat3(struct iterator a, struct iterator b,
																 struct iterator c)
{
	struct iterator *arr = calloc(sizeof(struct iterator), 3);
	arr[0] = a;
	arr[1] = b;
	arr[2] = c;
	return iterator_concat(arr, 3);
}

static void *empty_next(struct iterator *iter)
{
	(void)iter;
	return NULL;
}

static bool empty_has_next(struct iterator *iter)
{
	(void)iter;
	return false;
}

struct iterator iterator_empty()
{
	struct iterator it = {
		.index=0,
		.next=empty_next,
		.has_next=empty_has_next,
		.close=iterator_close_noop,
	};
	return it;
}