#include "cache.h"
#include "refs.h"
#include "object.h"
#include "commit.h"
#include "tag.h"

/*
 * Create the file "path" by writing to a temporary file and renaming
 * it into place. The contents of the file come from "generate", which
 * should return non-zero if it encounters an error.
 */
static int update_info_file(char *path, int (*generate)(FILE *))
{
        char *tmp = mkpathdup("%s_XXXXXX", path);
        int ret = -1;
        int fd = -1;
        FILE *fp = NULL;

        safe_create_leading_directories(path);
        fd = mkstemp(tmp);
        if (fd < 0)
                goto out;
        fp = fdopen(fd, "w");
        if (!fp)
                goto out;
        ret = generate(fp);
        if (ret)
                goto out;
        if (fclose(fp))
                goto out;
        if (adjust_shared_perm(tmp) < 0)
                goto out;
        if (rename(tmp, path) < 0)
                goto out;
        ret = 0;

out:
        if (ret) {
                error("unable to update %s: %s", path, strerror(errno));
                if (fp)
                        fclose(fp);
                else if (fd >= 0)
                        close(fd);
                unlink(tmp);
        }
        free(tmp);
        return ret;
}

static int add_info_ref(const char *path, const unsigned char *sha1, int flag, void *cb_data)
{
        FILE *fp = cb_data;
        struct object *o = parse_object(sha1);
        if (!o)
                return -1;

        if (fprintf(fp, "%s     %s\n", sha1_to_hex(sha1), path) < 0)
                return -1;

        if (o->type == OBJ_TAG) {
                o = deref_tag(o, path, 0);
                if (o)
                        if (fprintf(fp, "%s     %s^{}\n",
                                sha1_to_hex(o->sha1), path) < 0)
                                return -1;
        }
        return 0;
}

static int generate_info_refs(FILE *fp)
{
        return for_each_ref(add_info_ref, fp);
}

static int update_info_refs(int force)
{
        char *path = git_pathdup("info/refs");
        int ret = update_info_file(path, generate_info_refs);
        free(path);
        return ret;
}

/* packs */
static struct pack_info {
        struct packed_git *p;
        int old_num;
        int new_num;
        int nr_alloc;
        int nr_heads;
        unsigned char (*head)[20];
} **info;
static int num_pack;
static const char *objdir;
static int objdirlen;

static struct pack_info *find_pack_by_name(const char *name)
{
        int i;
        for (i = 0; i < num_pack; i++) {
                struct packed_git *p = info[i]->p;
                /* skip "/pack/" after ".git/objects" */
                if (!strcmp(p->pack_name + objdirlen + 6, name))
                        return info[i];
        }
        return NULL;
}

/* Returns non-zero when we detect that the info in the
 * old file is useless.
 */
static int parse_pack_def(const char *line, int old_cnt)
{
        struct pack_info *i = find_pack_by_name(line + 2);
        if (i) {
                i->old_num = old_cnt;
                return 0;
        }
        else {
                /* The file describes a pack that is no longer here */
                return 1;
        }
}

/* Returns non-zero when we detect that the info in the
 * old file is useless.
 */
static int read_pack_info_file(const char *infofile)
{
        FILE *fp;
        char line[1000];
        int old_cnt = 0;

        fp = fopen(infofile, "r");
        if (!fp)
                return 1; /* nonexistent is not an error. */

        while (fgets(line, sizeof(line), fp)) {
                int len = strlen(line);
                if (len && line[len-1] == '\n')
                        line[--len] = 0;

                if (!len)
                        continue;

                switch (line[0]) {
                case 'P': /* P name */
                        if (parse_pack_def(line, old_cnt++))
                                goto out_stale;
                        break;
                case 'D': /* we used to emit D but that was misguided. */
                case 'T': /* we used to emit T but nobody uses it. */
                        goto out_stale;
                default:
                        error("unrecognized: %s", line);
                        break;
                }
        }
        fclose(fp);
        return 0;
 out_stale:
        fclose(fp);
        return 1;
}

static int compare_info(const void *a_, const void *b_)
{
        struct pack_info *const *a = a_;
        struct pack_info *const *b = b_;

        if (0 <= (*a)->old_num && 0 <= (*b)->old_num)
                /* Keep the order in the original */
                return (*a)->old_num - (*b)->old_num;
        else if (0 <= (*a)->old_num)
                /* Only A existed in the original so B is obviously newer */
                return -1;
        else if (0 <= (*b)->old_num)
                /* The other way around. */
                return 1;

        /* then it does not matter but at least keep the comparison stable */
        if ((*a)->p == (*b)->p)
                return 0;
        else if ((*a)->p < (*b)->p)
                return -1;
        else
                return 1;
}

static void init_pack_info(const char *infofile, int force)
{
        struct packed_git *p;
        int stale;
        int i = 0;

        objdir = get_object_directory();
        objdirlen = strlen(objdir);

        prepare_packed_git();
        for (p = packed_git; p; p = p->next) {
                /* we ignore things on alternate path since they are
                 * not available to the pullers in general.
                 */
                if (!p->pack_local)
                        continue;
                i++;
        }
        num_pack = i;
        info = xcalloc(num_pack, sizeof(struct pack_info *));
        for (i = 0, p = packed_git; p; p = p->next) {
                if (!p->pack_local)
                        continue;
                info[i] = xcalloc(1, sizeof(struct pack_info));
                info[i]->p = p;
                info[i]->old_num = -1;
                i++;
        }

        if (infofile && !force)
                stale = read_pack_info_file(infofile);
        else
                stale = 1;

        for (i = 0; i < num_pack; i++) {
                if (stale) {
                        info[i]->old_num = -1;
                        info[i]->nr_heads = 0;
                }
        }

        /* renumber them */
        qsort(info, num_pack, sizeof(info[0]), compare_info);
        for (i = 0; i < num_pack; i++)
                info[i]->new_num = i;
}

static void free_pack_info(void)
{
        int i;
        for (i = 0; i < num_pack; i++)
                free(info[i]);
        free(info);
}

static int write_pack_info_file(FILE *fp)
{
        int i;
        for (i = 0; i < num_pack; i++) {
                if (fprintf(fp, "P %s\n", info[i]->p->pack_name + objdirlen + 6) < 0)
                        return -1;
        }
        if (fputc('\n', fp) == EOF)
                return -1;
        return 0;
}

static int update_info_packs(int force)
{
        char *infofile = mkpathdup("%s/info/packs", get_object_directory());
        int ret;

        init_pack_info(infofile, force);
        ret = update_info_file(infofile, write_pack_info_file);
        free_pack_info();
        free(infofile);
        return ret;
}

/* public */
int update_server_info(int force)
{
        /* We would add more dumb-server support files later,
         * including index of available pack files and their
         * intended audiences.
         */
        int errs = 0;

        errs = errs | update_info_refs(force);
        errs = errs | update_info_packs(force);

        /* remove leftover rev-cache file if there is any */
        unlink_or_warn(git_path("info/rev-cache"));

        return errs;
}