/*
 * git gc builtin command
 *
 * Cleanup unreachable files and optimize the repository.
 *
 * Copyright (c) 2007 James Bowes
 *
 * Based on git-gc.sh, which is
 *
 * Copyright (c) 2006 Shawn O. Pearce
 */

#include "builtin.h"
#include "repository.h"
#include "config.h"
#include "tempfile.h"
#include "lockfile.h"
#include "parse-options.h"
#include "run-command.h"
#include "sigchain.h"
#include "argv-array.h"
#include "commit.h"
#include "packfile.h"
#include "object-store.h"

#define FAILED_RUN "failed to run %s"

static const char * const builtin_gc_usage[] = {
        N_("git gc [<options>]"),
        NULL
};

static int pack_refs = 1;
static int prune_reflogs = 1;
static int aggressive_depth = 50;
static int aggressive_window = 250;
static int gc_auto_threshold = 6700;
static int gc_auto_pack_limit = 50;
static int detach_auto = 1;
static timestamp_t gc_log_expire_time;
static const char *gc_log_expire = "1.day.ago";
static const char *prune_expire = "2.weeks.ago";
static const char *prune_worktrees_expire = "3.months.ago";
static unsigned long big_pack_threshold;

static struct argv_array pack_refs_cmd = ARGV_ARRAY_INIT;
static struct argv_array reflog = ARGV_ARRAY_INIT;
static struct argv_array repack = ARGV_ARRAY_INIT;
static struct argv_array prune = ARGV_ARRAY_INIT;
static struct argv_array prune_worktrees = ARGV_ARRAY_INIT;
static struct argv_array rerere = ARGV_ARRAY_INIT;

static struct tempfile *pidfile;
static struct lock_file log_lock;

static struct string_list pack_garbage = STRING_LIST_INIT_DUP;

static void clean_pack_garbage(void)
{
        int i;
        for (i = 0; i < pack_garbage.nr; i++)
                unlink_or_warn(pack_garbage.items[i].string);
        string_list_clear(&pack_garbage, 0);
}

static void report_pack_garbage(unsigned seen_bits, const char *path)
{
        if (seen_bits == PACKDIR_FILE_IDX)
                string_list_append(&pack_garbage, path);
}

static void process_log_file(void)
{
        struct stat st;
        if (fstat(get_lock_file_fd(&log_lock), &st)) {
                /*
                 * Perhaps there was an i/o error or another
                 * unlikely situation.  Try to make a note of
                 * this in gc.log along with any existing
                 * messages.
                 */
                int saved_errno = errno;
                fprintf(stderr, _("Failed to fstat %s: %s"),
                        get_tempfile_path(log_lock.tempfile),
                        strerror(saved_errno));
                fflush(stderr);
                commit_lock_file(&log_lock);
                errno = saved_errno;
        } else if (st.st_size) {
                /* There was some error recorded in the lock file */
                commit_lock_file(&log_lock);
        } else {
                /* No error, clean up any old gc.log */
                unlink(git_path("gc.log"));
                rollback_lock_file(&log_lock);
        }
}

static void process_log_file_at_exit(void)
{
        fflush(stderr);
        process_log_file();
}

static void process_log_file_on_signal(int signo)
{
        process_log_file();
        sigchain_pop(signo);
        raise(signo);
}

static void gc_config(void)
{
        const char *value;

        if (!git_config_get_value("gc.packrefs", &value)) {
                if (value && !strcmp(value, "notbare"))
                        pack_refs = -1;
                else
                        pack_refs = git_config_bool("gc.packrefs", value);
        }

        git_config_get_int("gc.aggressivewindow", &aggressive_window);
        git_config_get_int("gc.aggressivedepth", &aggressive_depth);
        git_config_get_int("gc.auto", &gc_auto_threshold);
        git_config_get_int("gc.autopacklimit", &gc_auto_pack_limit);
        git_config_get_bool("gc.autodetach", &detach_auto);
        git_config_get_expiry("gc.pruneexpire", &prune_expire);
        git_config_get_expiry("gc.worktreepruneexpire", &prune_worktrees_expire);
        git_config_get_expiry("gc.logexpiry", &gc_log_expire);

        git_config_get_ulong("gc.bigpackthreshold", &big_pack_threshold);

        git_config(git_default_config, NULL);
}

static int too_many_loose_objects(void)
{
        /*
         * Quickly check if a "gc" is needed, by estimating how
         * many loose objects there are.  Because SHA-1 is evenly
         * distributed, we can check only one and get a reasonable
         * estimate.
         */
        DIR *dir;
        struct dirent *ent;
        int auto_threshold;
        int num_loose = 0;
        int needed = 0;

        if (gc_auto_threshold <= 0)
                return 0;

        dir = opendir(git_path("objects/17"));
        if (!dir)
                return 0;

        auto_threshold = DIV_ROUND_UP(gc_auto_threshold, 256);
        while ((ent = readdir(dir)) != NULL) {
                if (strspn(ent->d_name, "0123456789abcdef") != 38 ||
                    ent->d_name[38] != '\0')
                        continue;
                if (++num_loose > auto_threshold) {
                        needed = 1;
                        break;
                }
        }
        closedir(dir);
        return needed;
}

static void find_base_packs(struct string_list *packs, unsigned long limit)
{
        struct packed_git *p, *base = NULL;

        for (p = get_packed_git(the_repository); p; p = p->next) {
                if (!p->pack_local)
                        continue;
                if (limit) {
                        if (p->pack_size >= limit)
                                string_list_append(packs, p->pack_name);
                } else if (!base || base->pack_size < p->pack_size) {
                        base = p;
                }
        }

        if (base)
                string_list_append(packs, base->pack_name);
}

static int too_many_packs(void)
{
        struct packed_git *p;
        int cnt;

        if (gc_auto_pack_limit <= 0)
                return 0;

        for (cnt = 0, p = get_packed_git(the_repository); p; p = p->next) {
                if (!p->pack_local)
                        continue;
                if (p->pack_keep)
                        continue;
                /*
                 * Perhaps check the size of the pack and count only
                 * very small ones here?
                 */
                cnt++;
        }
        return gc_auto_pack_limit < cnt;
}

static int keep_one_pack(struct string_list_item *item, void *data)
{
        argv_array_pushf(&repack, "--keep-pack=%s", basename(item->string));
        return 0;
}

static void add_repack_all_option(struct string_list *keep_pack)
{
        if (prune_expire && !strcmp(prune_expire, "now"))
                argv_array_push(&repack, "-a");
        else {
                argv_array_push(&repack, "-A");
                if (prune_expire)
                        argv_array_pushf(&repack, "--unpack-unreachable=%s", prune_expire);
        }

        if (keep_pack)
                for_each_string_list(keep_pack, keep_one_pack, NULL);
}

static void add_repack_incremental_option(void)
{
       argv_array_push(&repack, "--no-write-bitmap-index");
}

static int need_to_gc(void)
{
        /*
         * Setting gc.auto to 0 or negative can disable the
         * automatic gc.
         */
        if (gc_auto_threshold <= 0)
                return 0;

        /*
         * If there are too many loose objects, but not too many
         * packs, we run "repack -d -l".  If there are too many packs,
         * we run "repack -A -d -l".  Otherwise we tell the caller
         * there is no need.
         */
        if (too_many_packs()) {
                struct string_list keep_pack = STRING_LIST_INIT_NODUP;

                if (big_pack_threshold)
                        find_base_packs(&keep_pack, big_pack_threshold);

                add_repack_all_option(&keep_pack);
                string_list_clear(&keep_pack, 0);
        } else if (too_many_loose_objects())
                add_repack_incremental_option();
        else
                return 0;

        if (run_hook_le(NULL, "pre-auto-gc", NULL))
                return 0;
        return 1;
}

/* return NULL on success, else hostname running the gc */
static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
{
        static struct lock_file lock;
        char my_host[HOST_NAME_MAX + 1];
        struct strbuf sb = STRBUF_INIT;
        struct stat st;
        uintmax_t pid;
        FILE *fp;
        int fd;
        char *pidfile_path;

        if (is_tempfile_active(pidfile))
                /* already locked */
                return NULL;

        if (xgethostname(my_host, sizeof(my_host)))
                xsnprintf(my_host, sizeof(my_host), "unknown");

        pidfile_path = git_pathdup("gc.pid");
        fd = hold_lock_file_for_update(&lock, pidfile_path,
                                       LOCK_DIE_ON_ERROR);
        if (!force) {
                static char locking_host[HOST_NAME_MAX + 1];
                static char *scan_fmt;
                int should_exit;

                if (!scan_fmt)
                        scan_fmt = xstrfmt("%s %%%ds", "%"SCNuMAX, HOST_NAME_MAX);
                fp = fopen(pidfile_path, "r");
                memset(locking_host, 0, sizeof(locking_host));
                should_exit =
                        fp != NULL &&
                        !fstat(fileno(fp), &st) &&
                        /*
                         * 12 hour limit is very generous as gc should
                         * never take that long. On the other hand we
                         * don't really need a strict limit here,
                         * running gc --auto one day late is not a big
                         * problem. --force can be used in manual gc
                         * after the user verifies that no gc is
                         * running.
                         */
                        time(NULL) - st.st_mtime <= 12 * 3600 &&
                        fscanf(fp, scan_fmt, &pid, locking_host) == 2 &&
                        /* be gentle to concurrent "gc" on remote hosts */
                        (strcmp(locking_host, my_host) || !kill(pid, 0) || errno == EPERM);
                if (fp != NULL)
                        fclose(fp);
                if (should_exit) {
                        if (fd >= 0)
                                rollback_lock_file(&lock);
                        *ret_pid = pid;
                        free(pidfile_path);
                        return locking_host;
                }
        }

        strbuf_addf(&sb, "%"PRIuMAX" %s",
                    (uintmax_t) getpid(), my_host);
        write_in_full(fd, sb.buf, sb.len);
        strbuf_release(&sb);
        commit_lock_file(&lock);
        pidfile = register_tempfile(pidfile_path);
        free(pidfile_path);
        return NULL;
}

static int report_last_gc_error(void)
{
        struct strbuf sb = STRBUF_INIT;
        int ret = 0;
        struct stat st;
        char *gc_log_path = git_pathdup("gc.log");

        if (stat(gc_log_path, &st)) {
                if (errno == ENOENT)
                        goto done;

                ret = error_errno(_("Can't stat %s"), gc_log_path);
                goto done;
        }

        if (st.st_mtime < gc_log_expire_time)
                goto done;

        ret = strbuf_read_file(&sb, gc_log_path, 0);
        if (ret > 0)
                ret = error(_("The last gc run reported the following. "
                               "Please correct the root cause\n"
                               "and remove %s.\n"
                               "Automatic cleanup will not be performed "
                               "until the file is removed.\n\n"
                               "%s"),
                            gc_log_path, sb.buf);
        strbuf_release(&sb);
done:
        free(gc_log_path);
        return ret;
}

static int gc_before_repack(void)
{
        if (pack_refs && run_command_v_opt(pack_refs_cmd.argv, RUN_GIT_CMD))
                return error(FAILED_RUN, pack_refs_cmd.argv[0]);

        if (prune_reflogs && run_command_v_opt(reflog.argv, RUN_GIT_CMD))
                return error(FAILED_RUN, reflog.argv[0]);

        pack_refs = 0;
        prune_reflogs = 0;
        return 0;
}

int cmd_gc(int argc, const char **argv, const char *prefix)
{
        int aggressive = 0;
        int auto_gc = 0;
        int quiet = 0;
        int force = 0;
        const char *name;
        pid_t pid;
        int daemonized = 0;
        int keep_base_pack = -1;

        struct option builtin_gc_options[] = {
                OPT__QUIET(&quiet, N_("suppress progress reporting")),
                { OPTION_STRING, 0, "prune", &prune_expire, N_("date"),
                        N_("prune unreferenced objects"),
                        PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire },
                OPT_BOOL(0, "aggressive", &aggressive, N_("be more thorough (increased runtime)")),
                OPT_BOOL_F(0, "auto", &auto_gc, N_("enable auto-gc mode"),
                           PARSE_OPT_NOCOMPLETE),
                OPT_BOOL_F(0, "force", &force,
                           N_("force running gc even if there may be another gc running"),
                           PARSE_OPT_NOCOMPLETE),
                OPT_BOOL(0, "keep-largest-pack", &keep_base_pack,
                         N_("repack all other packs except the largest pack")),
                OPT_END()
        };

        if (argc == 2 && !strcmp(argv[1], "-h"))
                usage_with_options(builtin_gc_usage, builtin_gc_options);

        argv_array_pushl(&pack_refs_cmd, "pack-refs", "--all", "--prune", NULL);
        argv_array_pushl(&reflog, "reflog", "expire", "--all", NULL);
        argv_array_pushl(&repack, "repack", "-d", "-l", NULL);
        argv_array_pushl(&prune, "prune", "--expire", NULL);
        argv_array_pushl(&prune_worktrees, "worktree", "prune", "--expire", NULL);
        argv_array_pushl(&rerere, "rerere", "gc", NULL);

        /* default expiry time, overwritten in gc_config */
        gc_config();
        if (parse_expiry_date(gc_log_expire, &gc_log_expire_time))
                die(_("Failed to parse gc.logexpiry value %s"), gc_log_expire);

        if (pack_refs < 0)
                pack_refs = !is_bare_repository();

        argc = parse_options(argc, argv, prefix, builtin_gc_options,
                             builtin_gc_usage, 0);
        if (argc > 0)
                usage_with_options(builtin_gc_usage, builtin_gc_options);

        if (aggressive) {
                argv_array_push(&repack, "-f");
                if (aggressive_depth > 0)
                        argv_array_pushf(&repack, "--depth=%d", aggressive_depth);
                if (aggressive_window > 0)
                        argv_array_pushf(&repack, "--window=%d", aggressive_window);
        }
        if (quiet)
                argv_array_push(&repack, "-q");

        if (auto_gc) {
                /*
                 * Auto-gc should be least intrusive as possible.
                 */
                if (!need_to_gc())
                        return 0;
                if (!quiet) {
                        if (detach_auto)
                                fprintf(stderr, _("Auto packing the repository in background for optimum performance.\n"));
                        else
                                fprintf(stderr, _("Auto packing the repository for optimum performance.\n"));
                        fprintf(stderr, _("See \"git help gc\" for manual housekeeping.\n"));
                }
                if (detach_auto) {
                        if (report_last_gc_error())
                                return -1;

                        if (lock_repo_for_gc(force, &pid))
                                return 0;
                        if (gc_before_repack())
                                return -1;
                        delete_tempfile(&pidfile);

                        /*
                         * failure to daemonize is ok, we'll continue
                         * in foreground
                         */
                        daemonized = !daemonize();
                }
        } else {
                struct string_list keep_pack = STRING_LIST_INIT_NODUP;

                if (keep_base_pack != -1) {
                        if (keep_base_pack)
                                find_base_packs(&keep_pack, 0);
                } else if (big_pack_threshold) {
                        find_base_packs(&keep_pack, big_pack_threshold);
                }

                add_repack_all_option(&keep_pack);
                string_list_clear(&keep_pack, 0);
        }

        name = lock_repo_for_gc(force, &pid);
        if (name) {
                if (auto_gc)
                        return 0; /* be quiet on --auto */
                die(_("gc is already running on machine '%s' pid %"PRIuMAX" (use --force if not)"),
                    name, (uintmax_t)pid);
        }

        if (daemonized) {
                hold_lock_file_for_update(&log_lock,
                                          git_path("gc.log"),
                                          LOCK_DIE_ON_ERROR);
                dup2(get_lock_file_fd(&log_lock), 2);
                sigchain_push_common(process_log_file_on_signal);
                atexit(process_log_file_at_exit);
        }

        if (gc_before_repack())
                return -1;

        if (!repository_format_precious_objects) {
                if (run_command_v_opt(repack.argv, RUN_GIT_CMD))
                        return error(FAILED_RUN, repack.argv[0]);

                if (prune_expire) {
                        argv_array_push(&prune, prune_expire);
                        if (quiet)
                                argv_array_push(&prune, "--no-progress");
                        if (repository_format_partial_clone)
                                argv_array_push(&prune,
                                                "--exclude-promisor-objects");
                        if (run_command_v_opt(prune.argv, RUN_GIT_CMD))
                                return error(FAILED_RUN, prune.argv[0]);
                }
        }

        if (prune_worktrees_expire) {
                argv_array_push(&prune_worktrees, prune_worktrees_expire);
                if (run_command_v_opt(prune_worktrees.argv, RUN_GIT_CMD))
                        return error(FAILED_RUN, prune_worktrees.argv[0]);
        }

        if (run_command_v_opt(rerere.argv, RUN_GIT_CMD))
                return error(FAILED_RUN, rerere.argv[0]);

        report_garbage = report_pack_garbage;
        reprepare_packed_git(the_repository);
        if (pack_garbage.nr > 0)
                clean_pack_garbage();

        if (auto_gc && too_many_loose_objects())
                warning(_("There are too many unreachable loose objects; "
                        "run 'git prune' to remove them."));

        if (!daemonized)
                unlink(git_path("gc.log"));

        return 0;
}