#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;
}