/*
 * 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 "cache.h"
#include "parse-options.h"
#include "run-command.h"
#include "argv-array.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 aggressive_window = 250;
static int gc_auto_threshold = 6700;
static int gc_auto_pack_limit = 50;
static const char *prune_expire = "2.weeks.ago";

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 rerere = ARGV_ARRAY_INIT;

static int gc_config(const char *var, const char *value, void *cb)
{
        if (!strcmp(var, "gc.packrefs")) {
                if (value && !strcmp(value, "notbare"))
                        pack_refs = -1;
                else
                        pack_refs = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "gc.aggressivewindow")) {
                aggressive_window = git_config_int(var, value);
                return 0;
        }
        if (!strcmp(var, "gc.auto")) {
                gc_auto_threshold = git_config_int(var, value);
                return 0;
        }
        if (!strcmp(var, "gc.autopacklimit")) {
                gc_auto_pack_limit = git_config_int(var, value);
                return 0;
        }
        if (!strcmp(var, "gc.pruneexpire")) {
                if (value && strcmp(value, "now")) {
                        unsigned long now = approxidate("now");
                        if (approxidate(value) >= now)
                                return error(_("Invalid %s: '%s'"), var, value);
                }
                return git_config_string(&prune_expire, var, value);
        }
        return git_default_config(var, value, cb);
}

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.
         */
        char path[PATH_MAX];
        const char *objdir = get_object_directory();
        DIR *dir;
        struct dirent *ent;
        int auto_threshold;
        int num_loose = 0;
        int needed = 0;

        if (gc_auto_threshold <= 0)
                return 0;

        if (sizeof(path) <= snprintf(path, sizeof(path), "%s/17", objdir)) {
                warning(_("insanely long object directory %.*s"), 50, objdir);
                return 0;
        }
        dir = opendir(path);
        if (!dir)
                return 0;

        auto_threshold = (gc_auto_threshold + 255) / 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 int too_many_packs(void)
{
        struct packed_git *p;
        int cnt;

        if (gc_auto_pack_limit <= 0)
                return 0;

        prepare_packed_git();
        for (cnt = 0, p = packed_git; 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 void add_repack_all_option(void)
{
        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);
        }
}

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())
                add_repack_all_option();
        else if (!too_many_loose_objects())
                return 0;

        if (run_hook(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;
        static char locking_host[128];
        char my_host[128];
        struct strbuf sb = STRBUF_INIT;
        struct stat st;
        uintmax_t pid;
        FILE *fp;
        int fd, should_exit;

        if (gethostname(my_host, sizeof(my_host)))
                strcpy(my_host, "unknown");

        fd = hold_lock_file_for_update(&lock, git_path("gc.pid"),
                                       LOCK_DIE_ON_ERROR);
        if (!force) {
                fp = fopen(git_path("gc.pid"), "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, "%"PRIuMAX" %127c", &pid, locking_host) == 2 &&
                        /* be gentle to concurrent "gc" on remote hosts */
                        (strcmp(locking_host, my_host) || !kill(pid, 0));
                if (fp != NULL)
                        fclose(fp);
                if (should_exit) {
                        if (fd >= 0)
                                rollback_lock_file(&lock);
                        *ret_pid = pid;
                        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);

        return NULL;
}

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;

        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_BOOLEAN(0, "aggressive", &aggressive, N_("be more thorough (increased runtime)")),
                OPT_BOOLEAN(0, "auto", &auto_gc, N_("enable auto-gc mode")),
                OPT_BOOL(0, "force", &force, N_("force running gc even if there may be another gc running")),
                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(&rerere, "rerere", "gc", NULL);

        git_config(gc_config, NULL);

        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");
                argv_array_push(&repack, "--depth=250");
                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)
                        fprintf(stderr,
                                        _("Auto packing the repository for optimum performance. You may also\n"
                                        "run \"git gc\" manually. See "
                                        "\"git help gc\" for more information.\n"));
        } else
                add_repack_all_option();

        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 (pack_refs && run_command_v_opt(pack_refs_cmd.argv, RUN_GIT_CMD))
                return error(FAILED_RUN, pack_refs_cmd.argv[0]);

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

        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 (run_command_v_opt(prune.argv, RUN_GIT_CMD))
                        return error(FAILED_RUN, prune.argv[0]);
        }

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

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

        return 0;
}