#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; /* Any valid ref can be used */
static int tags;        /* Allow lightweight tags */
static int longformat;
static int abbrev = DEFAULT_ABBREV;
static int max_candidates = 10;
static int found_names;
static const char *pattern;
static int always;

struct commit_name {
        struct tag *tag;
        int prio; /* annotated tag = 2, tag = 1, head = 0 */
        unsigned char sha1[20];
        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,
                               const unsigned char *sha1)
{
        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->tag = NULL;
                e->prio = prio;
                hashcpy(e->sha1, sha1);
                memcpy(e->path, path, len);
                commit->util = e;
        }
        found_names = 1;
}

static int get_name(const char *path, const unsigned char *sha1, int flag, void *cb_data)
{
        int might_be_tag = !prefixcmp(path, "refs/tags/");
        struct commit *commit;
        struct object *object;
        unsigned char peeled[20];
        int is_tag, prio;

        if (!all && !might_be_tag)
                return 0;

        if (!peel_ref(path, peeled) && !is_null_sha1(peeled)) {
                commit = lookup_commit_reference_gently(peeled, 1);
                if (!commit)
                        return 0;
                is_tag = !!hashcmp(sha1, commit->object.sha1);
        } else {
                commit = lookup_commit_reference_gently(sha1, 1);
                object = parse_object(sha1);
                if (!commit || !object)
                        return 0;
                is_tag = object->type == OBJ_TAG;
        }

        /* If --all, then any refs are used.
         * If --tags, then any tags are used.
         * Otherwise only annotated tags are used.
         */
        if (might_be_tag) {
                if (is_tag)
                        prio = 2;
                else
                        prio = 1;

                if (pattern && fnmatch(pattern, path + 10, 0))
                        prio = 0;
        }
        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, sha1);
        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->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 display_name(struct commit_name *n)
{
        if (n->prio == 2 && !n->tag) {
                n->tag = lookup_tag(n->sha1);
                if (!n->tag || parse_tag(n->tag) || !n->tag->tag)
                        die("annotated tag %s not available", n->path);
                if (strcmp(n->tag->tag, all ? n->path + 5 : n->path))
                        warning("tag '%s' is really '%s' here", n->tag->tag, n->path);
        }

        if (n->tag)
                printf("%s", n->tag->tag);
        else
                printf("%s", n->path);
}

static void show_suffix(int depth, const unsigned char *sha1)
{
        printf("-%d-g%s", depth, find_unique_abbrev(sha1, abbrev));
}

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);
        }

        if (!found_names)
                die("cannot describe '%s'", sha1_to_hex(sha1));

        n = cmit->util;
        if (n) {
                /*
                 * Exact match to an existing ref.
                 */
                display_name(n);
                if (longformat)
                        show_suffix(0, n->tag ? n->tag->tagged->sha1 : sha1);
                printf("\n");
                return;
        }

        if (!max_candidates)
                die("no tag exactly matches '%s'", sha1_to_hex(cmit->object.sha1));
        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) {
                const unsigned char *sha1 = cmit->object.sha1;
                if (always) {
                        printf("%s\n", find_unique_abbrev(sha1, abbrev));
                        return;
                }
                die("cannot describe '%s'", sha1_to_hex(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));
                }
        }

        display_name(all_matches[0].name);
        if (abbrev)
                show_suffix(all_matches[0].depth, cmit->object.sha1);
        printf("\n");

        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_BOOLEAN(0, "long",       &longformat, "always use long format"),
                OPT__ABBREV(&abbrev),
                OPT_SET_INT(0, "exact-match", &max_candidates,
                            "only output exact matches", 0),
                OPT_INTEGER(0, "candidates", &max_candidates,
                            "consider <n> most recent tags (default: 10)"),
                OPT_STRING(0, "match",       &pattern, "pattern",
                           "only consider tags matching <pattern>"),
                OPT_BOOLEAN(0, "always",     &always,
                           "show abbreviated commit object as fallback"),
                OPT_END(),
        };

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

        save_commit_buffer = 0;

        if (longformat && abbrev == 0)
                die("--long is incompatible with --abbrev=0");

        if (contains) {
                const char **args = xmalloc((7 + argc) * sizeof(char *));
                int i = 0;
                args[i++] = "name-rev";
                args[i++] = "--name-only";
                args[i++] = "--no-undefined";
                if (always)
                        args[i++] = "--always";
                if (!all) {
                        args[i++] = "--tags";
                        if (pattern) {
                                char *s = xmalloc(strlen("--refs=refs/tags/") + strlen(pattern) + 1);
                                sprintf(s, "--refs=refs/tags/%s", pattern);
                                args[i++] = s;
                        }
                }
                memcpy(args + i, argv, argc * sizeof(char *));
                args[i + argc] = NULL;
                return cmd_name_rev(i + argc, args, prefix);
        }

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