#include "builtin.h"
#include "cache.h"
#include "commit.h"
#include "refs.h"
#include "diff.h"
#include "revision.h"
#include "parse-options.h"

static int show_merge_base(struct commit **rev, int rev_nr, int show_all)
{
        struct commit_list *result;

        result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1, 0);

        if (!result)
                return 1;

        while (result) {
                printf("%s\n", sha1_to_hex(result->item->object.sha1));
                if (!show_all)
                        return 0;
                result = result->next;
        }

        return 0;
}

static const char * const merge_base_usage[] = {
        N_("git merge-base [-a|--all] <commit> <commit>..."),
        N_("git merge-base [-a|--all] --octopus <commit>..."),
        N_("git merge-base --independent <commit>..."),
        N_("git merge-base --is-ancestor <commit> <commit>"),
        N_("git merge-base --fork-point <ref> [<commit>]"),
        NULL
};

static struct commit *get_commit_reference(const char *arg)
{
        unsigned char revkey[20];
        struct commit *r;

        if (get_sha1(arg, revkey))
                die("Not a valid object name %s", arg);
        r = lookup_commit_reference(revkey);
        if (!r)
                die("Not a valid commit name %s", arg);

        return r;
}

static int handle_independent(int count, const char **args)
{
        struct commit_list *revs = NULL;
        struct commit_list *result;
        int i;

        for (i = count - 1; i >= 0; i--)
                commit_list_insert(get_commit_reference(args[i]), &revs);

        result = reduce_heads(revs);
        if (!result)
                return 1;

        while (result) {
                printf("%s\n", sha1_to_hex(result->item->object.sha1));
                result = result->next;
        }
        return 0;
}

static int handle_octopus(int count, const char **args, int show_all)
{
        struct commit_list *revs = NULL;
        struct commit_list *result;
        int i;

        for (i = count - 1; i >= 0; i--)
                commit_list_insert(get_commit_reference(args[i]), &revs);

        result = reduce_heads(get_octopus_merge_bases(revs));

        if (!result)
                return 1;

        while (result) {
                printf("%s\n", sha1_to_hex(result->item->object.sha1));
                if (!show_all)
                        return 0;
                result = result->next;
        }

        return 0;
}

static int handle_is_ancestor(int argc, const char **argv)
{
        struct commit *one, *two;

        if (argc != 2)
                die("--is-ancestor takes exactly two commits");
        one = get_commit_reference(argv[0]);
        two = get_commit_reference(argv[1]);
        if (in_merge_bases(one, two))
                return 0;
        else
                return 1;
}

struct rev_collect {
        struct commit **commit;
        int nr;
        int alloc;
        unsigned int initial : 1;
};

static void add_one_commit(unsigned char *sha1, struct rev_collect *revs)
{
        struct commit *commit;

        if (is_null_sha1(sha1))
                return;

        commit = lookup_commit(sha1);
        if (!commit ||
            (commit->object.flags & TMP_MARK) ||
            parse_commit(commit))
                return;

        ALLOC_GROW(revs->commit, revs->nr + 1, revs->alloc);
        revs->commit[revs->nr++] = commit;
        commit->object.flags |= TMP_MARK;
}

static int collect_one_reflog_ent(unsigned char *osha1, unsigned char *nsha1,
                                  const char *ident, unsigned long timestamp,
                                  int tz, const char *message, void *cbdata)
{
        struct rev_collect *revs = cbdata;

        if (revs->initial) {
                revs->initial = 0;
                add_one_commit(osha1, revs);
        }
        add_one_commit(nsha1, revs);
        return 0;
}

static int handle_fork_point(int argc, const char **argv)
{
        unsigned char sha1[20];
        char *refname;
        const char *commitname;
        struct rev_collect revs;
        struct commit *derived;
        struct commit_list *bases;
        int i, ret = 0;

        switch (dwim_ref(argv[0], strlen(argv[0]), sha1, &refname)) {
        case 0:
                die("No such ref: '%s'", argv[0]);
        case 1:
                break; /* good */
        default:
                die("Ambiguous refname: '%s'", argv[0]);
        }

        commitname = (argc == 2) ? argv[1] : "HEAD";
        if (get_sha1(commitname, sha1))
                die("Not a valid object name: '%s'", commitname);

        derived = lookup_commit_reference(sha1);
        memset(&revs, 0, sizeof(revs));
        revs.initial = 1;
        for_each_reflog_ent(refname, collect_one_reflog_ent, &revs);

        for (i = 0; i < revs.nr; i++)
                revs.commit[i]->object.flags &= ~TMP_MARK;

        bases = get_merge_bases_many(derived, revs.nr, revs.commit, 0);

        /*
         * There should be one and only one merge base, when we found
         * a common ancestor among reflog entries.
         */
        if (!bases || bases->next) {
                ret = 1;
                goto cleanup_return;
        }

        /* And the found one must be one of the reflog entries */
        for (i = 0; i < revs.nr; i++)
                if (&bases->item->object == &revs.commit[i]->object)
                        break; /* found */
        if (revs.nr <= i) {
                ret = 1; /* not found */
                goto cleanup_return;
        }

        printf("%s\n", sha1_to_hex(bases->item->object.sha1));

cleanup_return:
        free_commit_list(bases);
        return ret;
}

int cmd_merge_base(int argc, const char **argv, const char *prefix)
{
        struct commit **rev;
        int rev_nr = 0;
        int show_all = 0;
        int cmdmode = 0;

        struct option options[] = {
                OPT_BOOL('a', "all", &show_all, N_("output all common ancestors")),
                OPT_CMDMODE(0, "octopus", &cmdmode,
                            N_("find ancestors for a single n-way merge"), 'o'),
                OPT_CMDMODE(0, "independent", &cmdmode,
                            N_("list revs not reachable from others"), 'r'),
                OPT_CMDMODE(0, "is-ancestor", &cmdmode,
                            N_("is the first one ancestor of the other?"), 'a'),
                OPT_CMDMODE(0, "fork-point", &cmdmode,
                            N_("find where <commit> forked from reflog of <ref>"), 'f'),
                OPT_END()
        };

        git_config(git_default_config, NULL);
        argc = parse_options(argc, argv, prefix, options, merge_base_usage, 0);

        if (cmdmode == 'a') {
                if (argc < 2)
                        usage_with_options(merge_base_usage, options);
                if (show_all)
                        die("--is-ancestor cannot be used with --all");
                return handle_is_ancestor(argc, argv);
        }

        if (cmdmode == 'r' && show_all)
                die("--independent cannot be used with --all");

        if (cmdmode == 'o')
                return handle_octopus(argc, argv, show_all);

        if (cmdmode == 'r')
                return handle_independent(argc, argv);

        if (cmdmode == 'f') {
                if (argc < 1 || 2 < argc)
                        usage_with_options(merge_base_usage, options);
                return handle_fork_point(argc, argv);
        }

        if (argc < 2)
                usage_with_options(merge_base_usage, options);

        rev = xmalloc(argc * sizeof(*rev));
        while (argc-- > 0)
                rev[rev_nr++] = get_commit_reference(*argv++);
        return show_merge_base(rev, rev_nr, show_all);
}