#include "allocator.h"
#include "aoc.h"
#include "dvec_s.h"
#include "util.h"

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

static void
deck_cut(struct dvec *deck, struct dvec *table, ssize_t in)
{
	int *src, *dst;
	size_t i, split, n;

	n = deck->len;
	split = in < 0 ? (size_t) ((ssize_t) deck->len + in) : (size_t) in;
	src = deck->data;
	dst = table->data;

	for (i = 0; i < split; i++)
		dst[i + n - split] = src[i];
	for (i = split; i < n; i++)
		dst[i - split] = src[i];

	dvec_swap(deck, table);
}

static void
deal_increment(struct dvec *deck, struct dvec *table, size_t inc)
{
	int *src, *dst;
	size_t i, n, p;

	n = deck->len;
	src = deck->data;
	dst = table->data;

	p = 0;
	for (i = 0; i < n; i++) {
		dst[p] = src[i];
		p = (p + inc) % n;
	}

	dvec_swap(deck, table);
}

static void
deal_new_stack(struct dvec *deck, struct dvec *table)
{
	int *src, *dst;
	size_t i, n;

	n = deck->len - 1;
	src = deck->data;
	dst = table->data;

	for (i = 0; i <= n; i++)
		dst[n - i] = src[i];

	dvec_swap(deck, table);
}

static size_t
find_card(struct dvec *deck, int card)
{
	int *data;
	size_t i, n;

	n = deck->len;
	data = deck->data;
	for (i = 0; i < n; i++) {
		if (data[i] == card)
			return i;
	}
	return 0;
}

void
part1(void)
{
	char line[256];
	const char *lpos, *lend;
	struct dvec deck, table;
	size_t i, count;
	size_t answer;
	ssize_t val;
	int target;
	int *data;

	if (!strcmp(aoc.inputfile, "input")) {
		count = 10007;
		target = 2019;
	} else {
		count = 10;
		target = 9;
	}

	dvec_init(&deck, sizeof(int), count, &stdlib_strict_heap_allocator);
	dvec_init(&table, sizeof(int), count, &stdlib_strict_heap_allocator);

	dvec_add_slots(&deck, count);
	dvec_add_slots(&table, count);
	data = deck.data;
	for (i = 0; i < count; i++)
		data[i] = (int) i;

	lpos = aoc.input;
	lend = lpos + aoc.input_size;
	while (readtok(line, sizeof(line), '\n', &lpos, lend)) {
		if (sscanf(line, "deal with increment %li", &val) == 1) {
			deal_increment(&deck, &table, (size_t) val);
		} else if (sscanf(line, "cut %li", &val) == 1) {
			deck_cut(&deck, &table, val);
		} else if (!strcmp(line, "deal into new stack")) {
			deal_new_stack(&deck, &table);
		} else if (strspn(line, " \n\r\t\v") == strlen(line)) {
			continue;
		} else {
			assert(false);
		}
		aoc_debug("%i pos: %lu\n", target, find_card(&deck, target));
	}

	answer = find_card(&deck, target);
	aoc.answer = aprintf("%lu", answer);
	aoc.solution = "7171";

	dvec_deinit(&table);
	dvec_deinit(&deck);
}