#include "refs.h"
#include "cache.h"

#include <errno.h>

static int read_ref(const char *path, unsigned char *sha1)
{
        int ret = -1;
        int fd = open(path, O_RDONLY);

        if (fd >= 0) {
                char buffer[60];
                if (read(fd, buffer, sizeof(buffer)) >= 40)
                        ret = get_sha1_hex(buffer, sha1);
                close(fd);
        }
        return ret;
}

static int do_for_each_ref(const char *base, int (*fn)(const char *path, unsigned char *sha1))
{
        int retval = 0;
        DIR *dir = opendir(base);

        if (dir) {
                struct dirent *de;
                int baselen = strlen(base);
                char *path = xmalloc(baselen + 257);
                memcpy(path, base, baselen);

                while ((de = readdir(dir)) != NULL) {
                        unsigned char sha1[20];
                        struct stat st;
                        int namelen;

                        if (de->d_name[0] == '.')
                                continue;
                        namelen = strlen(de->d_name);
                        if (namelen > 255)
                                continue;
                        memcpy(path + baselen, de->d_name, namelen+1);
                        if (lstat(path, &st) < 0)
                                continue;
                        if (S_ISDIR(st.st_mode)) {
                                path[baselen + namelen] = '/';
                                path[baselen + namelen + 1] = 0;
                                retval = do_for_each_ref(path, fn);
                                if (retval)
                                        break;
                                continue;
                        }
                        if (read_ref(path, sha1) < 0)
                                continue;
                        if (!has_sha1_file(sha1))
                                continue;
                        retval = fn(path, sha1);
                        if (retval)
                                break;
                }
                free(path);
                closedir(dir);
        }
        return retval;
}

int for_each_ref(int (*fn)(const char *path, unsigned char *sha1))
{
        return do_for_each_ref("refs/", fn);
}

static char *ref_file_name(const char *ref)
{
        char *base = get_refs_directory();
        int baselen = strlen(base);
        int reflen = strlen(ref);
        char *ret = xmalloc(baselen + 2 + reflen);
        sprintf(ret, "%s/%s", base, ref);
        return ret;
}

static char *ref_lock_file_name(const char *ref)
{
        char *base = get_refs_directory();
        int baselen = strlen(base);
        int reflen = strlen(ref);
        char *ret = xmalloc(baselen + 7 + reflen);
        sprintf(ret, "%s/%s.lock", base, ref);
        return ret;
}

static int read_ref_file(const char *filename, unsigned char *sha1) {
        int fd = open(filename, O_RDONLY);
        char hex[41];
        if (fd < 0) {
                return error("Couldn't open %s\n", filename);
        }
        if ((read(fd, hex, 41) < 41) ||
            (hex[40] != '\n') ||
            get_sha1_hex(hex, sha1)) {
                error("Couldn't read a hash from %s\n", filename);
                close(fd);
                return -1;
        }
        close(fd);
        return 0;
}

int get_ref_sha1(const char *ref, unsigned char *sha1)
{
        char *filename;
        int retval;
        if (check_ref_format(ref))
                return -1;
        filename = ref_file_name(ref);
        retval = read_ref_file(filename, sha1);
        free(filename);
        return retval;
}

static int lock_ref_file(const char *filename, const char *lock_filename,
                         const unsigned char *old_sha1)
{
        int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
        unsigned char current_sha1[20];
        int retval;
        if (fd < 0) {
                return error("Couldn't open lock file for %s: %s",
                             filename, strerror(errno));
        }
        retval = read_ref_file(filename, current_sha1);
        if (old_sha1) {
                if (retval) {
                        close(fd);
                        unlink(lock_filename);
                        return error("Could not read the current value of %s",
                                     filename);
                }
                if (memcmp(current_sha1, old_sha1, 20)) {
                        close(fd);
                        unlink(lock_filename);
                        error("The current value of %s is %s",
                              filename, sha1_to_hex(current_sha1));
                        return error("Expected %s",
                                     sha1_to_hex(old_sha1));
                }
        } else {
                if (!retval) {
                        close(fd);
                        unlink(lock_filename);
                        return error("Unexpectedly found a value of %s for %s",
                                     sha1_to_hex(current_sha1), filename);
                }
        }
        return fd;
}

int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
{
        char *filename;
        char *lock_filename;
        int retval;
        if (check_ref_format(ref))
                return -1;
        filename = ref_file_name(ref);
        lock_filename = ref_lock_file_name(ref);
        retval = lock_ref_file(filename, lock_filename, old_sha1);
        free(filename);
        free(lock_filename);
        return retval;
}

static int write_ref_file(const char *filename,
                          const char *lock_filename, int fd,
                          const unsigned char *sha1)
{
        char *hex = sha1_to_hex(sha1);
        char term = '\n';
        if (write(fd, hex, 40) < 40 ||
            write(fd, &term, 1) < 1) {
                error("Couldn't write %s\n", filename);
                close(fd);
                return -1;
        }
        close(fd);
        rename(lock_filename, filename);
        return 0;
}

int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
{
        char *filename;
        char *lock_filename;
        int retval;
        if (fd < 0)
                return -1;
        if (check_ref_format(ref))
                return -1;
        filename = ref_file_name(ref);
        lock_filename = ref_lock_file_name(ref);
        retval = write_ref_file(filename, lock_filename, fd, sha1);
        free(filename);
        free(lock_filename);
        return retval;
}

int check_ref_format(const char *ref)
{
        char *middle;
        if (ref[0] == '.' || ref[0] == '/')
                return -1;
        middle = strchr(ref, '/');
        if (!middle || !middle[1])
                return -1;
        if (strchr(middle + 1, '/'))
                return -1;
        return 0;
}

int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
{
        char *filename;
        char *lock_filename;
        int fd;
        int retval;
        if (check_ref_format(ref))
                return -1;
        filename = ref_file_name(ref);
        lock_filename = ref_lock_file_name(ref);
        fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
        if (fd < 0) {
                error("Writing %s", lock_filename);
                perror("Open");
        }
        retval = write_ref_file(filename, lock_filename, fd, sha1);
        free(filename);
        free(lock_filename);
        return retval;
}