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

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

static const char * const describe_usage[] = {
        N_("git describe [options] <committish>*"),
        N_("git describe [options] --dirty"),
        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 first_parent;
static int abbrev = -1; /* unspecified */
static int max_candidates = 10;
static struct hash_table names;
static int have_util;
static const char *pattern;
static int always;
static const char *dirty;

/* diff-index command arguments to check if working tree is dirty. */
static const char *diff_index_args[] = {
        "diff-index", "--quiet", "HEAD", "--", NULL
};


struct commit_name {
        struct commit_name *next;
        unsigned char peeled[20];
        struct tag *tag;
        unsigned prio:2; /* annotated tag = 2, tag = 1, head = 0 */
        unsigned name_checked:1;
        unsigned char sha1[20];
        const char *path;
};
static const char *prio_names[] = {
        "head", "lightweight", "annotated",
};

static inline unsigned int hash_sha1(const unsigned char *sha1)
{
        unsigned int hash;
        memcpy(&hash, sha1, sizeof(hash));
        return hash;
}

static inline struct commit_name *find_commit_name(const unsigned char *peeled)
{
        struct commit_name *n = lookup_hash(hash_sha1(peeled), &names);
        while (n && !!hashcmp(peeled, n->peeled))
                n = n->next;
        return n;
}

static int set_util(void *chain, void *data)
{
        struct commit_name *n;
        for (n = chain; n; n = n->next) {
                struct commit *c = lookup_commit_reference_gently(n->peeled, 1);
                if (c)
                        c->util = n;
        }
        return 0;
}

static int replace_name(struct commit_name *e,
                               int prio,
                               const unsigned char *sha1,
                               struct tag **tag)
{
        if (!e || e->prio < prio)
                return 1;

        if (e->prio == 2 && prio == 2) {
                /* Multiple annotated tags point to the same commit.
                 * Select one to keep based upon their tagger date.
                 */
                struct tag *t;

                if (!e->tag) {
                        t = lookup_tag(e->sha1);
                        if (!t || parse_tag(t))
                                return 1;
                        e->tag = t;
                }

                t = lookup_tag(sha1);
                if (!t || parse_tag(t))
                        return 0;
                *tag = t;

                if (e->tag->date < t->date)
                        return 1;
        }

        return 0;
}

static void add_to_known_names(const char *path,
                               const unsigned char *peeled,
                               int prio,
                               const unsigned char *sha1)
{
        struct commit_name *e = find_commit_name(peeled);
        struct tag *tag = NULL;
        if (replace_name(e, prio, sha1, &tag)) {
                if (!e) {
                        void **pos;
                        e = xmalloc(sizeof(struct commit_name));
                        hashcpy(e->peeled, peeled);
                        pos = insert_hash(hash_sha1(peeled), e, &names);
                        if (pos) {
                                e->next = *pos;
                                *pos = e;
                        } else {
                                e->next = NULL;
                        }
                }
                e->tag = tag;
                e->prio = prio;
                e->name_checked = 0;
                hashcpy(e->sha1, sha1);
                e->path = path;
        }
}

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

        /* Reject anything outside refs/tags/ unless --all */
        if (!all && !is_tag)
                return 0;

        /* Accept only tags that match the pattern, if given */
        if (pattern && (!is_tag || fnmatch(pattern, path + 10, 0)))
                return 0;

        /* Is it annotated? */
        if (!peel_ref(path, peeled)) {
                is_annotated = !!hashcmp(sha1, peeled);
        } else {
                hashcpy(peeled, sha1);
                is_annotated = 0;
        }

        /*
         * By default, we only use annotated tags, but with --tags
         * we fall back to lightweight ones (even without --tags,
         * we still remember lightweight ones, only to give hints
         * in an error message).  --all allows any refs to be used.
         */
        if (is_annotated)
                prio = 2;
        else if (is_tag)
                prio = 1;
        else
                prio = 0;

        add_to_known_names(all ? path + 5 : path + 10, peeled, 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))
                                commit_list_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))
                        die(_("annotated tag %s not available"), n->path);
        }
        if (n->tag && !n->name_checked) {
                if (!n->tag->tag)
                        die(_("annotated tag %s has no embedded name"), 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);
                n->name_checked = 1;
        }

        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;
        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;
        unsigned int unannotated_cnt = 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);

        n = find_commit_name(cmit->object.sha1);
        if (n && (tags || all || n->prio == 2)) {
                /*
                 * Exact match to an existing ref.
                 */
                display_name(n);
                if (longformat)
                        show_suffix(0, n->tag ? n->tag->tagged->sha1 : sha1);
                if (dirty)
                        printf("%s", dirty);
                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);

        if (!have_util) {
                for_each_hash(&names, set_util, NULL);
                have_util = 1;
        }

        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 (!tags && !all && n->prio < 2) {
                                unannotated_cnt++;
                        } else 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))
                                commit_list_insert_by_date(p, &list);
                        p->object.flags |= c->object.flags;
                        parents = parents->next;

                        if (first_parent)
                                break;
                }
        }

        if (!match_cnt) {
                const unsigned char *sha1 = cmit->object.sha1;
                if (always) {
                        printf("%s", find_unique_abbrev(sha1, abbrev));
                        if (dirty)
                                printf("%s", dirty);
                        printf("\n");
                        return;
                }
                if (unannotated_cnt)
                        die(_("No annotated tags can describe '%s'.\n"
                            "However, there were unannotated tags: try --tags."),
                            sha1_to_hex(sha1));
                else
                        die(_("No tags can describe '%s'.\n"
                            "Try --always, or create some tags."),
                            sha1_to_hex(sha1));
        }

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

        if (gave_up_on) {
                commit_list_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);
        if (dirty)
                printf("%s", dirty);
        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, N_("find the tag that comes after the commit")),
                OPT_BOOLEAN(0, "debug",      &debug, N_("debug search strategy on stderr")),
                OPT_BOOLEAN(0, "all",        &all, N_("use any ref")),
                OPT_BOOLEAN(0, "tags",       &tags, N_("use any tag, even unannotated")),
                OPT_BOOLEAN(0, "long",       &longformat, N_("always use long format")),
                OPT_BOOLEAN(0, "first-parent", &first_parent, N_("only follow first parent")),
                OPT__ABBREV(&abbrev),
                OPT_SET_INT(0, "exact-match", &max_candidates,
                            N_("only output exact matches"), 0),
                OPT_INTEGER(0, "candidates", &max_candidates,
                            N_("consider <n> most recent tags (default: 10)")),
                OPT_STRING(0, "match",       &pattern, N_("pattern"),
                           N_("only consider tags matching <pattern>")),
                OPT_BOOLEAN(0, "always",     &always,
                           N_("show abbreviated commit object as fallback")),
                {OPTION_STRING, 0, "dirty",  &dirty, N_("mark"),
                           N_("append <mark> on dirty working tree (default: \"-dirty\")"),
                 PARSE_OPT_OPTARG, NULL, (intptr_t) "-dirty"},
                OPT_END(),
        };

        git_config(git_default_config, NULL);
        argc = parse_options(argc, argv, prefix, options, describe_usage, 0);
        if (abbrev < 0)
                abbrev = DEFAULT_ABBREV;

        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);
        }

        init_hash(&names);
        for_each_rawref(get_name, NULL);
        if (!names.nr && !always)
                die(_("No names found, cannot describe anything."));

        if (argc == 0) {
                if (dirty) {
                        static struct lock_file index_lock;
                        int fd;

                        read_cache_preload(NULL);
                        refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED,
                                      NULL, NULL, NULL);
                        fd = hold_locked_index(&index_lock, 0);
                        if (0 <= fd)
                                update_index_if_able(&the_index, &index_lock);

                        if (!cmd_diff_index(ARRAY_SIZE(diff_index_args) - 1,
                                            diff_index_args, prefix))
                                dirty = NULL;
                }
                describe("HEAD", 1);
        } else if (dirty) {
                die(_("--dirty is incompatible with committishes"));
        } else {
                while (argc-- > 0) {
                        describe(*argv++, argc == 0);
                }
        }
        return 0;
}