#include "cache.h"
#include "prio-queue.h"
#include "commit.h"
#include "commit-reach.h"

/* Remember to update object flag allocation in object.h */
#define PARENT1		(1u<<16)
#define PARENT2		(1u<<17)
#define STALE		(1u<<18)
#define RESULT		(1u<<19)

static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);

static int queue_has_nonstale(struct prio_queue *queue)
{
	int i;
	for (i = 0; i < queue->nr; i++) {
		struct commit *commit = queue->array[i].data;
		if (!(commit->object.flags & STALE))
			return 1;
	}
	return 0;
}

/* all input commits in one and twos[] must have been parsed! */
static struct commit_list *paint_down_to_common(struct commit *one, int n,
						struct commit **twos,
						int min_generation)
{
	struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
	struct commit_list *result = NULL;
	int i;
	uint32_t last_gen = GENERATION_NUMBER_INFINITY;

	one->object.flags |= PARENT1;
	if (!n) {
		commit_list_append(one, &result);
		return result;
	}
	prio_queue_put(&queue, one);

	for (i = 0; i < n; i++) {
		twos[i]->object.flags |= PARENT2;
		prio_queue_put(&queue, twos[i]);
	}

	while (queue_has_nonstale(&queue)) {
		struct commit *commit = prio_queue_get(&queue);
		struct commit_list *parents;
		int flags;

		if (commit->generation > last_gen)
			BUG("bad generation skip %8x > %8x at %s",
			    commit->generation, last_gen,
			    oid_to_hex(&commit->object.oid));
		last_gen = commit->generation;

		if (commit->generation < min_generation)
			break;

		flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
		if (flags == (PARENT1 | PARENT2)) {
			if (!(commit->object.flags & RESULT)) {
				commit->object.flags |= RESULT;
				commit_list_insert_by_date(commit, &result);
			}
			/* Mark parents of a found merge stale */
			flags |= STALE;
		}
		parents = commit->parents;
		while (parents) {
			struct commit *p = parents->item;
			parents = parents->next;
			if ((p->object.flags & flags) == flags)
				continue;
			if (parse_commit(p))
				return NULL;
			p->object.flags |= flags;
			prio_queue_put(&queue, p);
		}
	}

	clear_prio_queue(&queue);
	return result;
}

static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
{
	struct commit_list *list = NULL;
	struct commit_list *result = NULL;
	int i;

	for (i = 0; i < n; i++) {
		if (one == twos[i])
			/*
			 * We do not mark this even with RESULT so we do not
			 * have to clean it up.
			 */
			return commit_list_insert(one, &result);
	}

	if (parse_commit(one))
		return NULL;
	for (i = 0; i < n; i++) {
		if (parse_commit(twos[i]))
			return NULL;
	}

	list = paint_down_to_common(one, n, twos, 0);

	while (list) {
		struct commit *commit = pop_commit(&list);
		if (!(commit->object.flags & STALE))
			commit_list_insert_by_date(commit, &result);
	}
	return result;
}

struct commit_list *get_octopus_merge_bases(struct commit_list *in)
{
	struct commit_list *i, *j, *k, *ret = NULL;

	if (!in)
		return ret;

	commit_list_insert(in->item, &ret);

	for (i = in->next; i; i = i->next) {
		struct commit_list *new_commits = NULL, *end = NULL;

		for (j = ret; j; j = j->next) {
			struct commit_list *bases;
			bases = get_merge_bases(i->item, j->item);
			if (!new_commits)
				new_commits = bases;
			else
				end->next = bases;
			for (k = bases; k; k = k->next)
				end = k;
		}
		ret = new_commits;
	}
	return ret;
}

static int remove_redundant(struct commit **array, int cnt)
{
	/*
	 * Some commit in the array may be an ancestor of
	 * another commit.  Move such commit to the end of
	 * the array, and return the number of commits that
	 * are independent from each other.
	 */
	struct commit **work;
	unsigned char *redundant;
	int *filled_index;
	int i, j, filled;

	work = xcalloc(cnt, sizeof(*work));
	redundant = xcalloc(cnt, 1);
	ALLOC_ARRAY(filled_index, cnt - 1);

	for (i = 0; i < cnt; i++)
		parse_commit(array[i]);
	for (i = 0; i < cnt; i++) {
		struct commit_list *common;
		uint32_t min_generation = array[i]->generation;

		if (redundant[i])
			continue;
		for (j = filled = 0; j < cnt; j++) {
			if (i == j || redundant[j])
				continue;
			filled_index[filled] = j;
			work[filled++] = array[j];

			if (array[j]->generation < min_generation)
				min_generation = array[j]->generation;
		}
		common = paint_down_to_common(array[i], filled, work,
					      min_generation);
		if (array[i]->object.flags & PARENT2)
			redundant[i] = 1;
		for (j = 0; j < filled; j++)
			if (work[j]->object.flags & PARENT1)
				redundant[filled_index[j]] = 1;
		clear_commit_marks(array[i], all_flags);
		clear_commit_marks_many(filled, work, all_flags);
		free_commit_list(common);
	}

	/* Now collect the result */
	COPY_ARRAY(work, array, cnt);
	for (i = filled = 0; i < cnt; i++)
		if (!redundant[i])
			array[filled++] = work[i];
	for (j = filled, i = 0; i < cnt; i++)
		if (redundant[i])
			array[j++] = work[i];
	free(work);
	free(redundant);
	free(filled_index);
	return filled;
}

static struct commit_list *get_merge_bases_many_0(struct commit *one,
						  int n,
						  struct commit **twos,
						  int cleanup)
{
	struct commit_list *list;
	struct commit **rslt;
	struct commit_list *result;
	int cnt, i;

	result = merge_bases_many(one, n, twos);
	for (i = 0; i < n; i++) {
		if (one == twos[i])
			return result;
	}
	if (!result || !result->next) {
		if (cleanup) {
			clear_commit_marks(one, all_flags);
			clear_commit_marks_many(n, twos, all_flags);
		}
		return result;
	}

	/* There are more than one */
	cnt = commit_list_count(result);
	rslt = xcalloc(cnt, sizeof(*rslt));
	for (list = result, i = 0; list; list = list->next)
		rslt[i++] = list->item;
	free_commit_list(result);

	clear_commit_marks(one, all_flags);
	clear_commit_marks_many(n, twos, all_flags);

	cnt = remove_redundant(rslt, cnt);
	result = NULL;
	for (i = 0; i < cnt; i++)
		commit_list_insert_by_date(rslt[i], &result);
	free(rslt);
	return result;
}

struct commit_list *get_merge_bases_many(struct commit *one,
					 int n,
					 struct commit **twos)
{
	return get_merge_bases_many_0(one, n, twos, 1);
}

struct commit_list *get_merge_bases_many_dirty(struct commit *one,
					       int n,
					       struct commit **twos)
{
	return get_merge_bases_many_0(one, n, twos, 0);
}

struct commit_list *get_merge_bases(struct commit *one, struct commit *two)
{
	return get_merge_bases_many_0(one, 1, &two, 1);
}

/*
 * Is "commit" a descendant of one of the elements on the "with_commit" list?
 */
int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
{
	if (!with_commit)
		return 1;
	while (with_commit) {
		struct commit *other;

		other = with_commit->item;
		with_commit = with_commit->next;
		if (in_merge_bases(other, commit))
			return 1;
	}
	return 0;
}

/*
 * Is "commit" an ancestor of one of the "references"?
 */
int in_merge_bases_many(struct commit *commit, int nr_reference, struct commit **reference)
{
	struct commit_list *bases;
	int ret = 0, i;
	uint32_t min_generation = GENERATION_NUMBER_INFINITY;

	if (parse_commit(commit))
		return ret;
	for (i = 0; i < nr_reference; i++) {
		if (parse_commit(reference[i]))
			return ret;
		if (reference[i]->generation < min_generation)
			min_generation = reference[i]->generation;
	}

	if (commit->generation > min_generation)
		return ret;

	bases = paint_down_to_common(commit, nr_reference, reference, commit->generation);
	if (commit->object.flags & PARENT2)
		ret = 1;
	clear_commit_marks(commit, all_flags);
	clear_commit_marks_many(nr_reference, reference, all_flags);
	free_commit_list(bases);
	return ret;
}

/*
 * Is "commit" an ancestor of (i.e. reachable from) the "reference"?
 */
int in_merge_bases(struct commit *commit, struct commit *reference)
{
	return in_merge_bases_many(commit, 1, &reference);
}

struct commit_list *reduce_heads(struct commit_list *heads)
{
	struct commit_list *p;
	struct commit_list *result = NULL, **tail = &result;
	struct commit **array;
	int num_head, i;

	if (!heads)
		return NULL;

	/* Uniquify */
	for (p = heads; p; p = p->next)
		p->item->object.flags &= ~STALE;
	for (p = heads, num_head = 0; p; p = p->next) {
		if (p->item->object.flags & STALE)
			continue;
		p->item->object.flags |= STALE;
		num_head++;
	}
	array = xcalloc(num_head, sizeof(*array));
	for (p = heads, i = 0; p; p = p->next) {
		if (p->item->object.flags & STALE) {
			array[i++] = p->item;
			p->item->object.flags &= ~STALE;
		}
	}
	num_head = remove_redundant(array, num_head);
	for (i = 0; i < num_head; i++)
		tail = &commit_list_insert(array[i], tail)->next;
	free(array);
	return result;
}

void reduce_heads_replace(struct commit_list **heads)
{
	struct commit_list *result = reduce_heads(*heads);
	free_commit_list(*heads);
	*heads = result;
}