#include "cache.h"
#include "commit.h"
#include "commit-graph.h"
#include "decorate.h"
#include "prio-queue.h"
#include "tree.h"
#include "ref-filter.h"
#include "revision.h"
#include "tag.h"
#include "commit-reach.h"

/* Remember to update object flag allocation in object.h */
#define REACHABLE       (1u<<15)
#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 repository *r,
                                                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;

        if (!min_generation)
                queue.compare = compare_commits_by_commit_date;

        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 (min_generation && 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 (repo_parse_commit(r, 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 repository *r,
                                            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 (repo_parse_commit(r, one))
                return NULL;
        for (i = 0; i < n; i++) {
                if (repo_parse_commit(r, twos[i]))
                        return NULL;
        }

        list = paint_down_to_common(r, 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 repository *r, 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++)
                repo_parse_commit(r, 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(r, 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 repository *r,
                                                  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(r, 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(r, 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 *repo_get_merge_bases_many(struct repository *r,
                                              struct commit *one,
                                              int n,
                                              struct commit **twos)
{
        return get_merge_bases_many_0(r, one, n, twos, 1);
}

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

struct commit_list *repo_get_merge_bases(struct repository *r,
                                         struct commit *one,
                                         struct commit *two)
{
        return get_merge_bases_many_0(r, 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;

        if (generation_numbers_enabled(the_repository)) {
                struct commit_list *from_list = NULL;
                int result;
                commit_list_insert(commit, &from_list);
                result = can_all_from_reach(from_list, with_commit, 0);
                free_commit_list(from_list);
                return result;
        } else {
                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(the_repository, 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(the_repository, 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;
}

int ref_newer(const struct object_id *new_oid, const struct object_id *old_oid)
{
        struct object *o;
        struct commit *old_commit, *new_commit;
        struct commit_list *old_commit_list = NULL;

        /*
         * Both new_commit and old_commit must be commit-ish and new_commit is descendant of
         * old_commit.  Otherwise we require --force.
         */
        o = deref_tag(the_repository, parse_object(the_repository, old_oid),
                      NULL, 0);
        if (!o || o->type != OBJ_COMMIT)
                return 0;
        old_commit = (struct commit *) o;

        o = deref_tag(the_repository, parse_object(the_repository, new_oid),
                      NULL, 0);
        if (!o || o->type != OBJ_COMMIT)
                return 0;
        new_commit = (struct commit *) o;

        if (parse_commit(new_commit) < 0)
                return 0;

        commit_list_insert(old_commit, &old_commit_list);
        return is_descendant_of(new_commit, old_commit_list);
}

/*
 * Mimicking the real stack, this stack lives on the heap, avoiding stack
 * overflows.
 *
 * At each recursion step, the stack items points to the commits whose
 * ancestors are to be inspected.
 */
struct contains_stack {
        int nr, alloc;
        struct contains_stack_entry {
                struct commit *commit;
                struct commit_list *parents;
        } *contains_stack;
};

static int in_commit_list(const struct commit_list *want, struct commit *c)
{
        for (; want; want = want->next)
                if (oideq(&want->item->object.oid, &c->object.oid))
                        return 1;
        return 0;
}

/*
 * Test whether the candidate is contained in the list.
 * Do not recurse to find out, though, but return -1 if inconclusive.
 */
static enum contains_result contains_test(struct commit *candidate,
                                          const struct commit_list *want,
                                          struct contains_cache *cache,
                                          uint32_t cutoff)
{
        enum contains_result *cached = contains_cache_at(cache, candidate);

        /* If we already have the answer cached, return that. */
        if (*cached)
                return *cached;

        /* or are we it? */
        if (in_commit_list(want, candidate)) {
                *cached = CONTAINS_YES;
                return CONTAINS_YES;
        }

        /* Otherwise, we don't know; prepare to recurse */
        parse_commit_or_die(candidate);

        if (candidate->generation < cutoff)
                return CONTAINS_NO;

        return CONTAINS_UNKNOWN;
}

static void push_to_contains_stack(struct commit *candidate, struct contains_stack *contains_stack)
{
        ALLOC_GROW(contains_stack->contains_stack, contains_stack->nr + 1, contains_stack->alloc);
        contains_stack->contains_stack[contains_stack->nr].commit = candidate;
        contains_stack->contains_stack[contains_stack->nr++].parents = candidate->parents;
}

static enum contains_result contains_tag_algo(struct commit *candidate,
                                              const struct commit_list *want,
                                              struct contains_cache *cache)
{
        struct contains_stack contains_stack = { 0, 0, NULL };
        enum contains_result result;
        uint32_t cutoff = GENERATION_NUMBER_INFINITY;
        const struct commit_list *p;

        for (p = want; p; p = p->next) {
                struct commit *c = p->item;
                load_commit_graph_info(the_repository, c);
                if (c->generation < cutoff)
                        cutoff = c->generation;
        }

        result = contains_test(candidate, want, cache, cutoff);
        if (result != CONTAINS_UNKNOWN)
                return result;

        push_to_contains_stack(candidate, &contains_stack);
        while (contains_stack.nr) {
                struct contains_stack_entry *entry = &contains_stack.contains_stack[contains_stack.nr - 1];
                struct commit *commit = entry->commit;
                struct commit_list *parents = entry->parents;

                if (!parents) {
                        *contains_cache_at(cache, commit) = CONTAINS_NO;
                        contains_stack.nr--;
                }
                /*
                 * If we just popped the stack, parents->item has been marked,
                 * therefore contains_test will return a meaningful yes/no.
                 */
                else switch (contains_test(parents->item, want, cache, cutoff)) {
                case CONTAINS_YES:
                        *contains_cache_at(cache, commit) = CONTAINS_YES;
                        contains_stack.nr--;
                        break;
                case CONTAINS_NO:
                        entry->parents = parents->next;
                        break;
                case CONTAINS_UNKNOWN:
                        push_to_contains_stack(parents->item, &contains_stack);
                        break;
                }
        }
        free(contains_stack.contains_stack);
        return contains_test(candidate, want, cache, cutoff);
}

int commit_contains(struct ref_filter *filter, struct commit *commit,
                    struct commit_list *list, struct contains_cache *cache)
{
        if (filter->with_commit_tag_algo)
                return contains_tag_algo(commit, list, cache) == CONTAINS_YES;
        return is_descendant_of(commit, list);
}

static int compare_commits_by_gen(const void *_a, const void *_b)
{
        const struct commit *a = (const struct commit *)_a;
        const struct commit *b = (const struct commit *)_b;

        if (a->generation < b->generation)
                return -1;
        if (a->generation > b->generation)
                return 1;
        return 0;
}

int can_all_from_reach_with_flag(struct object_array *from,
                                 unsigned int with_flag,
                                 unsigned int assign_flag,
                                 time_t min_commit_date,
                                 uint32_t min_generation)
{
        struct commit **list = NULL;
        int i;
        int nr_commits;
        int result = 1;

        ALLOC_ARRAY(list, from->nr);
        nr_commits = 0;
        for (i = 0; i < from->nr; i++) {
                struct object *from_one = from->objects[i].item;

                if (!from_one || from_one->flags & assign_flag)
                        continue;

                from_one = deref_tag(the_repository, from_one,
                                     "a from object", 0);
                if (!from_one || from_one->type != OBJ_COMMIT) {
                        /*
                         * no way to tell if this is reachable by
                         * looking at the ancestry chain alone, so
                         * leave a note to ourselves not to worry about
                         * this object anymore.
                         */
                        from->objects[i].item->flags |= assign_flag;
                        continue;
                }

                list[nr_commits] = (struct commit *)from_one;
                if (parse_commit(list[nr_commits]) ||
                    list[nr_commits]->generation < min_generation) {
                        result = 0;
                        goto cleanup;
                }

                nr_commits++;
        }

        QSORT(list, nr_commits, compare_commits_by_gen);

        for (i = 0; i < nr_commits; i++) {
                /* DFS from list[i] */
                struct commit_list *stack = NULL;

                list[i]->object.flags |= assign_flag;
                commit_list_insert(list[i], &stack);

                while (stack) {
                        struct commit_list *parent;

                        if (stack->item->object.flags & with_flag) {
                                pop_commit(&stack);
                                continue;
                        }

                        for (parent = stack->item->parents; parent; parent = parent->next) {
                                if (parent->item->object.flags & (with_flag | RESULT))
                                        stack->item->object.flags |= RESULT;

                                if (!(parent->item->object.flags & assign_flag)) {
                                        parent->item->object.flags |= assign_flag;

                                        if (parse_commit(parent->item) ||
                                            parent->item->date < min_commit_date ||
                                            parent->item->generation < min_generation)
                                                continue;

                                        commit_list_insert(parent->item, &stack);
                                        break;
                                }
                        }

                        if (!parent)
                                pop_commit(&stack);
                }

                if (!(list[i]->object.flags & (with_flag | RESULT))) {
                        result = 0;
                        goto cleanup;
                }
        }

cleanup:
        clear_commit_marks_many(nr_commits, list, RESULT | assign_flag);
        free(list);

        for (i = 0; i < from->nr; i++)
                from->objects[i].item->flags &= ~assign_flag;

        return result;
}

int can_all_from_reach(struct commit_list *from, struct commit_list *to,
                       int cutoff_by_min_date)
{
        struct object_array from_objs = OBJECT_ARRAY_INIT;
        time_t min_commit_date = cutoff_by_min_date ? from->item->date : 0;
        struct commit_list *from_iter = from, *to_iter = to;
        int result;
        uint32_t min_generation = GENERATION_NUMBER_INFINITY;

        while (from_iter) {
                add_object_array(&from_iter->item->object, NULL, &from_objs);

                if (!parse_commit(from_iter->item)) {
                        if (from_iter->item->date < min_commit_date)
                                min_commit_date = from_iter->item->date;

                        if (from_iter->item->generation < min_generation)
                                min_generation = from_iter->item->generation;
                }

                from_iter = from_iter->next;
        }

        while (to_iter) {
                if (!parse_commit(to_iter->item)) {
                        if (to_iter->item->date < min_commit_date)
                                min_commit_date = to_iter->item->date;

                        if (to_iter->item->generation < min_generation)
                                min_generation = to_iter->item->generation;
                }

                to_iter->item->object.flags |= PARENT2;

                to_iter = to_iter->next;
        }

        result = can_all_from_reach_with_flag(&from_objs, PARENT2, PARENT1,
                                              min_commit_date, min_generation);

        while (from) {
                clear_commit_marks(from->item, PARENT1);
                from = from->next;
        }

        while (to) {
                clear_commit_marks(to->item, PARENT2);
                to = to->next;
        }

        object_array_clear(&from_objs);
        return result;
}