/*
 * 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 "run-command.h"

#define FAILED_RUN "failed to run %s"

static const char builtin_gc_usage[] = "git-gc [--prune] [--aggressive]";

static int pack_refs = 1;
static int aggressive_window = -1;
static int gc_auto_threshold = 6700;
static int gc_auto_pack_limit = 20;

#define MAX_ADD 10
static const char *argv_pack_refs[] = {"pack-refs", "--all", "--prune", NULL};
static const char *argv_reflog[] = {"reflog", "expire", "--all", NULL};
static const char *argv_repack[MAX_ADD] = {"repack", "-d", "-l", NULL};
static const char *argv_prune[] = {"prune", NULL};
static const char *argv_rerere[] = {"rerere", "gc", NULL};

static int gc_config(const char *var, const char *value)
{
        if (!strcmp(var, "gc.packrefs")) {
                if (!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;
        }
        return git_default_config(var, value);
}

static void append_option(const char **cmd, const char *opt, int max_length)
{
        int i;

        for (i = 0; cmd[i]; i++)
                ;

        if (i + 2 >= max_length)
                die("Too many options specified");
        cmd[i++] = opt;
        cmd[i] = 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.
         */
        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) {
                char path[PATH_MAX];
                size_t len;
                int keep;

                if (!p->pack_local)
                        continue;
                len = strlen(p->pack_name);
                if (PATH_MAX <= len + 1)
                        continue; /* oops, give up */
                memcpy(path, p->pack_name, len-5);
                memcpy(path + len - 5, ".keep", 6);
                keep = access(p->pack_name, F_OK) && (errno == ENOENT);
                if (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 need_to_gc(void)
{
        /*
         * Setting gc.auto and gc.autopacklimit to 0 or negative can
         * disable the automatic gc.
         */
        if (gc_auto_threshold <= 0 && gc_auto_pack_limit <= 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())
                append_option(argv_repack, "-A", MAX_ADD);
        else if (!too_many_loose_objects())
                return 0;
        return 1;
}

int cmd_gc(int argc, const char **argv, const char *prefix)
{
        int i;
        int prune = 0;
        int auto_gc = 0;
        char buf[80];

        git_config(gc_config);

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

        for (i = 1; i < argc; i++) {
                const char *arg = argv[i];
                if (!strcmp(arg, "--prune")) {
                        prune = 1;
                        continue;
                }
                if (!strcmp(arg, "--aggressive")) {
                        append_option(argv_repack, "-f", MAX_ADD);
                        if (aggressive_window > 0) {
                                sprintf(buf, "--window=%d", aggressive_window);
                                append_option(argv_repack, buf, MAX_ADD);
                        }
                        continue;
                }
                if (!strcmp(arg, "--auto")) {
                        auto_gc = 1;
                        continue;
                }
                break;
        }
        if (i != argc)
                usage(builtin_gc_usage);

        if (auto_gc) {
                /*
                 * Auto-gc should be least intrusive as possible.
                 */
                prune = 0;
                if (!need_to_gc())
                        return 0;
                fprintf(stderr, "Packing your repository for optimum "
                        "performance. You may also\n"
                        "run \"git gc\" manually. See "
                        "\"git help gc\" for more information.\n");
        } else {
                /*
                 * Use safer (for shared repos) "-A" option to
                 * repack when not pruning. Auto-gc makes its
                 * own decision.
                 */
                if (prune)
                        append_option(argv_repack, "-a", MAX_ADD);
                else
                        append_option(argv_repack, "-A", MAX_ADD);
        }

        if (pack_refs && run_command_v_opt(argv_pack_refs, RUN_GIT_CMD))
                return error(FAILED_RUN, argv_pack_refs[0]);

        if (run_command_v_opt(argv_reflog, RUN_GIT_CMD))
                return error(FAILED_RUN, argv_reflog[0]);

        if (run_command_v_opt(argv_repack, RUN_GIT_CMD))
                return error(FAILED_RUN, argv_repack[0]);

        if (prune && run_command_v_opt(argv_prune, RUN_GIT_CMD))
                return error(FAILED_RUN, argv_prune[0]);

        if (run_command_v_opt(argv_rerere, RUN_GIT_CMD))
                return error(FAILED_RUN, argv_rerere[0]);

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

        return 0;
}