#include "cache.h"
#include "commit.h"
#include "tag.h"
#include "refs.h"
#include "builtin.h"
#include "exec_cmd.h"
#include "parse-options.h"

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

static const char * const describe_usage[] = {
        "git-describe [options] <committish>*",
        NULL
};

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;

struct commit_name {
        int prio; /* annotated tag = 2, tag = 1, head = 0 */
        char path[FLEX_ARRAY]; /* more */
};
static const char *prio_names[] = {
        "head", "lightweight", "annotated",
};

static void add_to_known_names(const char *path,
                               struct commit *commit,
                               int prio)
{
        struct commit_name *e = commit->util;
        if (!e || e->prio < prio) {
                size_t len = strlen(path)+1;
                free(e);
                e = xmalloc(sizeof(struct commit_name) + len);
                e->prio = prio;
                memcpy(e->path, path, len);
                commit->util = e;
        }
}

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 (!prefixcmp(path, "refs/tags/")) {
                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;
}

struct possible_tag {
        struct commit_name *name;
        int depth;
        int found_order;
        unsigned flag_within;
};

static int compare_pt(const void *a_, const void *b_)
{
        struct possible_tag *a = (struct possible_tag *)a_;
        struct possible_tag *b = (struct possible_tag *)b_;
        if (a->name->prio != b->name->prio)
                return b->name->prio - a->name->prio;
        if (a->depth != b->depth)
                return a->depth - b->depth;
        if (a->found_order != b->found_order)
                return a->found_order - b->found_order;
        return 0;
}

static unsigned long finish_depth_computation(
        struct commit_list **list,
        struct possible_tag *best)
{
        unsigned long seen_commits = 0;
        while (*list) {
                struct commit *c = pop_commit(list);
                struct commit_list *parents = c->parents;
                seen_commits++;
                if (c->object.flags & best->flag_within) {
                        struct commit_list *a = *list;
                        while (a) {
                                struct commit *i = a->item;
                                if (!(i->object.flags & best->flag_within))
                                        break;
                                a = a->next;
                        }
                        if (!a)
                                break;
                } else
                        best->depth++;
                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;
                }
        }
        return seen_commits;
}

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];
        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) {
                initialized = 1;
                for_each_ref(get_name, NULL);
        }

        n = cmit->util;
        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 = c->util;
                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;
                                t->found_order = 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;
                }
        }

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

        qsort(all_matches, match_cnt, sizeof(all_matches[0]), compare_pt);

        if (gave_up_on) {
                insert_by_date(gave_up_on, &list);
                seen_commits--;
        }
        seen_commits += finish_depth_computation(&list, &all_matches[0]);
        free_commit_list(list);

        if (debug) {
                for (cur_match = 0; cur_match < match_cnt; cur_match++) {
                        struct possible_tag *t = &all_matches[cur_match];
                        fprintf(stderr, " %-11s %8d %s\n",
                                prio_names[t->name->prio],
                                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));
                }
        }
        if (abbrev == 0)
                printf("%s\n", all_matches[0].name->path );
        else
                printf("%s-%d-g%s\n", all_matches[0].name->path,
                       all_matches[0].depth,
                       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 contains = 0;
        struct option options[] = {
                OPT_BOOLEAN(0, "contains",   &contains, "find the tag that comes after the commit"),
                OPT_BOOLEAN(0, "debug",      &debug, "debug search strategy on stderr"),
                OPT_BOOLEAN(0, "all",        &all, "use any ref in .git/refs"),
                OPT_BOOLEAN(0, "tags",       &tags, "use any tag in .git/refs/tags"),
                OPT__ABBREV(&abbrev),
                OPT_INTEGER(0, "candidates", &max_candidates,
                                        "consider <n> most recent tags (default: 10)"),
                OPT_END(),
        };

        argc = parse_options(argc, argv, options, describe_usage, 0);
        if (max_candidates < 1)
                max_candidates = 1;
        else if (max_candidates > MAX_TAGS)
                max_candidates = MAX_TAGS;

        save_commit_buffer = 0;

        if (contains) {
                const char **args = xmalloc((4 + argc) * sizeof(char*));
                args[0] = "name-rev";
                args[1] = "--name-only";
                args[2] = "--tags";
                memcpy(args + 3, argv, argc * sizeof(char*));
                args[3 + argc] = NULL;
                return cmd_name_rev(3 + argc, args, prefix);
        }

        if (argc == 0) {
                describe("HEAD", 1);
        } else {
                while (argc-- > 0) {
                        describe(*argv++, argc == 0);
                }
        }
        return 0;
}