#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"
#include "argv-array.h"

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

static const char * const describe_usage[] = {
	N_("git describe [options] <commit-ish>*"),
	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];
	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->path = NULL;
		}
		e->tag = tag;
		e->prio = prio;
		e->name_checked = 0;
		hashcpy(e->sha1, sha1);
		free(e->path);
		e->path = xstrdup(path);
	}
}

static int get_name(const char *path, const unsigned char *sha1, int flag, void *cb_data)
{
	int is_tag = starts_with(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_BOOL(0, "contains",   &contains, N_("find the tag that comes after the commit")),
		OPT_BOOL(0, "debug",      &debug, N_("debug search strategy on stderr")),
		OPT_BOOL(0, "all",        &all, N_("use any ref")),
		OPT_BOOL(0, "tags",       &tags, N_("use any tag, even unannotated")),
		OPT_BOOL(0, "long",       &longformat, N_("always use long format")),
		OPT_BOOL(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_BOOL(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) {
		struct argv_array args;

		argv_array_init(&args);
		argv_array_pushl(&args, "name-rev",
				 "--peel-tag", "--name-only", "--no-undefined",
				 NULL);
		if (always)
			argv_array_push(&args, "--always");
		if (!all) {
			argv_array_push(&args, "--tags");
			if (pattern)
				argv_array_pushf(&args, "--refs=refs/tags/%s", pattern);
		}
		while (*argv) {
			argv_array_push(&args, *argv);
			argv++;
		}
		return cmd_name_rev(args.argc, args.argv, 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 commit-ishes"));
	} else {
		while (argc-- > 0)
			describe(*argv++, argc == 0);
	}
	return 0;
}
