#include "cache.h"
#include "commit.h"
#include "tag.h"
#include "refs.h"
#include "builtin.h"

#define SEEN            (1u<<0)
#define MAX_TAGS        (FLAG_BITS - 1)

static const char describe_usage[] =
"git-describe [--all] [--tags] [--abbrev=<n>] <committish>*";

static int debug;       /* Display lots of verbose info */
static int all; /* Default to annotated tags only */
static int tags;        /* But allow any tags if --tags is specified */
static int abbrev = DEFAULT_ABBREV;
static int max_candidates = 10;

static unsigned int names[256], allocs[256];
static struct commit_name {
        struct commit *commit;
        int prio; /* annotated tag = 2, tag = 1, head = 0 */
        char path[FLEX_ARRAY]; /* more */
} **name_array[256];

static struct commit_name *match(struct commit *cmit)
{
        unsigned char level0 = cmit->object.sha1[0];
        struct commit_name **p = name_array[level0];
        unsigned int hi = names[level0];
        unsigned int lo = 0;

        while (lo < hi) {
                unsigned int mi = (lo + hi) / 2;
                int cmp = hashcmp(p[mi]->commit->object.sha1,
                        cmit->object.sha1);
                if (!cmp) {
                        while (mi && p[mi - 1]->commit == cmit)
                                mi--;
                        return p[mi];
                }
                if (cmp > 0)
                        hi = mi;
                else
                        lo = mi+1;
        }
        return NULL;
}

static void add_to_known_names(const char *path,
                               struct commit *commit,
                               int prio)
{
        int idx;
        int len = strlen(path)+1;
        struct commit_name *name = xmalloc(sizeof(struct commit_name) + len);
        unsigned char m = commit->object.sha1[0];

        name->commit = commit;
        name->prio = prio;
        memcpy(name->path, path, len);
        idx = names[m];
        if (idx >= allocs[m]) {
                allocs[m] = (idx + 50) * 3 / 2;
                name_array[m] = xrealloc(name_array[m],
                        allocs[m] * sizeof(*name_array));
        }
        name_array[m][idx] = name;
        names[m] = ++idx;
}

static int get_name(const char *path, const unsigned char *sha1, int flag, void *cb_data)
{
        struct commit *commit = lookup_commit_reference_gently(sha1, 1);
        struct object *object;
        int prio;

        if (!commit)
                return 0;
        object = parse_object(sha1);
        /* If --all, then any refs are used.
         * If --tags, then any tags are used.
         * Otherwise only annotated tags are used.
         */
        if (!strncmp(path, "refs/tags/", 10)) {
                if (object->type == OBJ_TAG)
                        prio = 2;
                else
                        prio = 1;
        }
        else
                prio = 0;

        if (!all) {
                if (!prio)
                        return 0;
                if (!tags && prio < 2)
                        return 0;
        }
        add_to_known_names(all ? path + 5 : path + 10, commit, prio);
        return 0;
}

static int compare_names(const void *_a, const void *_b)
{
        struct commit_name *a = *(struct commit_name **)_a;
        struct commit_name *b = *(struct commit_name **)_b;
        unsigned long a_date = a->commit->date;
        unsigned long b_date = b->commit->date;
        int cmp = hashcmp(a->commit->object.sha1, b->commit->object.sha1);

        if (cmp)
                return cmp;
        if (a->prio != b->prio)
                return b->prio - a->prio;
        return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
}

struct possible_tag {
        struct commit_name *name;
        unsigned long depth;
        unsigned flag_within;
};

static void describe(const char *arg, int last_one)
{
        unsigned char sha1[20];
        struct commit *cmit, *gave_up_on = NULL;
        struct commit_list *list;
        static int initialized = 0;
        struct commit_name *n;
        struct possible_tag all_matches[MAX_TAGS], *min_match;
        unsigned int match_cnt = 0, annotated_cnt = 0, cur_match;
        unsigned long seen_commits = 0;

        if (get_sha1(arg, sha1))
                die("Not a valid object name %s", arg);
        cmit = lookup_commit_reference(sha1);
        if (!cmit)
                die("%s is not a valid '%s' object", arg, commit_type);

        if (!initialized) {
                unsigned int m;
                initialized = 1;
                for_each_ref(get_name, NULL);
                for (m = 0; m < ARRAY_SIZE(name_array); m++)
                        qsort(name_array[m], names[m],
                                sizeof(*name_array[m]), compare_names);
        }

        n = match(cmit);
        if (n) {
                printf("%s\n", n->path);
                return;
        }

        if (debug)
                fprintf(stderr, "searching to describe %s\n", arg);

        list = NULL;
        cmit->object.flags = SEEN;
        commit_list_insert(cmit, &list);
        while (list) {
                struct commit *c = pop_commit(&list);
                struct commit_list *parents = c->parents;
                seen_commits++;
                n = match(c);
                if (n) {
                        if (match_cnt < max_candidates) {
                                struct possible_tag *t = &all_matches[match_cnt++];
                                t->name = n;
                                t->depth = seen_commits - 1;
                                t->flag_within = 1u << match_cnt;
                                c->object.flags |= t->flag_within;
                                if (n->prio == 2)
                                        annotated_cnt++;
                        }
                        else {
                                gave_up_on = c;
                                break;
                        }
                }
                for (cur_match = 0; cur_match < match_cnt; cur_match++) {
                        struct possible_tag *t = &all_matches[cur_match];
                        if (!(c->object.flags & t->flag_within))
                                t->depth++;
                }
                if (annotated_cnt && !list) {
                        if (debug)
                                fprintf(stderr, "finished search at %s\n",
                                        sha1_to_hex(c->object.sha1));
                        break;
                }
                while (parents) {
                        struct commit *p = parents->item;
                        parse_commit(p);
                        if (!(p->object.flags & SEEN))
                                insert_by_date(p, &list);
                        p->object.flags |= c->object.flags;
                        parents = parents->next;
                }
        }
        free_commit_list(list);

        if (!match_cnt)
                die("cannot describe '%s'", sha1_to_hex(cmit->object.sha1));

        min_match = &all_matches[0];
        for (cur_match = 1; cur_match < match_cnt; cur_match++) {
                struct possible_tag *t = &all_matches[cur_match];
                if (t->depth < min_match->depth
                        && t->name->prio >= min_match->name->prio)
                        min_match = t;
        }
        if (debug) {
                for (cur_match = 0; cur_match < match_cnt; cur_match++) {
                        struct possible_tag *t = &all_matches[cur_match];
                        fprintf(stderr, " %c %8lu %s\n",
                                min_match == t ? '*' : ' ',
                                t->depth, t->name->path);
                }
                fprintf(stderr, "traversed %lu commits\n", seen_commits);
                if (gave_up_on) {
                        fprintf(stderr,
                                "more than %i tags found; listed %i most recent\n"
                                "gave up search at %s\n",
                                max_candidates, max_candidates,
                                sha1_to_hex(gave_up_on->object.sha1));
                }
        }
        printf("%s-g%s\n", min_match->name->path,
                   find_unique_abbrev(cmit->object.sha1, abbrev));

        if (!last_one)
                clear_commit_marks(cmit, -1);
}

int cmd_describe(int argc, const char **argv, const char *prefix)
{
        int i;

        for (i = 1; i < argc; i++) {
                const char *arg = argv[i];

                if (*arg != '-')
                        break;
                else if (!strcmp(arg, "--debug"))
                        debug = 1;
                else if (!strcmp(arg, "--all"))
                        all = 1;
                else if (!strcmp(arg, "--tags"))
                        tags = 1;
                else if (!strncmp(arg, "--abbrev=", 9)) {
                        abbrev = strtoul(arg + 9, NULL, 10);
                        if (abbrev < MINIMUM_ABBREV || 40 < abbrev)
                                abbrev = DEFAULT_ABBREV;
                }
                else if (!strncmp(arg, "--candidates=", 13)) {
                        max_candidates = strtoul(arg + 13, NULL, 10);
                        if (max_candidates < 1)
                                max_candidates = 1;
                        else if (max_candidates > MAX_TAGS)
                                max_candidates = MAX_TAGS;
                }
                else
                        usage(describe_usage);
        }

        save_commit_buffer = 0;

        if (argc <= i)
                describe("HEAD", 1);
        else
                while (i < argc) {
                        describe(argv[i], (i == argc - 1));
                        i++;
                }

        return 0;
}