/*
 * I'm tired of doing "vsnprintf()" etc just to open a
 * file, so here's a "return static buffer with printf"
 * interface for paths.
 *
 * It's obviously not thread-safe. Sue me. But it's quite
 * useful for doing things like
 *
 *   f = open(mkpath("%s/%s.git", base, name), O_RDONLY);
 *
 * which is what it's designed for.
 */
#include "cache.h"
#include <pwd.h>

static char pathname[PATH_MAX];
static char bad_path[] = "/bad-path/";

static char *cleanup_path(char *path)
{
        /* Clean it up */
        if (!memcmp(path, "./", 2)) {
                path += 2;
                while (*path == '/')
                        path++;
        }
        return path;
}

char *mkpath(const char *fmt, ...)
{
        va_list args;
        unsigned len;

        va_start(args, fmt);
        len = vsnprintf(pathname, PATH_MAX, fmt, args);
        va_end(args);
        if (len >= PATH_MAX)
                return bad_path;
        return cleanup_path(pathname);
}

char *git_path(const char *fmt, ...)
{
        const char *git_dir = get_git_dir();
        va_list args;
        unsigned len;

        len = strlen(git_dir);
        if (len > PATH_MAX-100)
                return bad_path;
        memcpy(pathname, git_dir, len);
        if (len && git_dir[len-1] != '/')
                pathname[len++] = '/';
        va_start(args, fmt);
        len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
        va_end(args);
        if (len >= PATH_MAX)
                return bad_path;
        return cleanup_path(pathname);
}


/* git_mkstemp() - create tmp file honoring TMPDIR variable */
int git_mkstemp(char *path, size_t len, const char *template)
{
        char *env, *pch = path;

        if ((env = getenv("TMPDIR")) == NULL) {
                strcpy(pch, "/tmp/");
                len -= 5;
                pch += 5;
        } else {
                size_t n = snprintf(pch, len, "%s/", env);

                len -= n;
                pch += n;
        }

        safe_strncpy(pch, template, len);

        return mkstemp(path);
}


char *safe_strncpy(char *dest, const char *src, size_t n)
{
        strncpy(dest, src, n);
        dest[n - 1] = '\0';

        return dest;
}

int validate_symref(const char *path)
{
        struct stat st;
        char *buf, buffer[256];
        int len, fd;

        if (lstat(path, &st) < 0)
                return -1;

        /* Make sure it is a "refs/.." symlink */
        if (S_ISLNK(st.st_mode)) {
                len = readlink(path, buffer, sizeof(buffer)-1);
                if (len >= 5 && !memcmp("refs/", buffer, 5))
                        return 0;
                return -1;
        }

        /*
         * Anything else, just open it and try to see if it is a symbolic ref.
         */
        fd = open(path, O_RDONLY);
        if (fd < 0)
                return -1;
        len = read(fd, buffer, sizeof(buffer)-1);
        close(fd);

        /*
         * Is it a symbolic ref?
         */
        if (len < 4 || memcmp("ref:", buffer, 4))
                return -1;
        buf = buffer + 4;
        len -= 4;
        while (len && isspace(*buf))
                buf++, len--;
        if (len >= 5 && !memcmp("refs/", buf, 5))
                return 0;
        return -1;
}

static char *user_path(char *buf, char *path, int sz)
{
        struct passwd *pw;
        char *slash;
        int len, baselen;

        if (!path || path[0] != '~')
                return NULL;
        path++;
        slash = strchr(path, '/');
        if (path[0] == '/' || !path[0]) {
                pw = getpwuid(getuid());
        }
        else {
                if (slash) {
                        *slash = 0;
                        pw = getpwnam(path);
                        *slash = '/';
                }
                else
                        pw = getpwnam(path);
        }
        if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
                return NULL;
        baselen = strlen(pw->pw_dir);
        memcpy(buf, pw->pw_dir, baselen);
        while ((1 < baselen) && (buf[baselen-1] == '/')) {
                buf[baselen-1] = 0;
                baselen--;
        }
        if (slash && slash[1]) {
                len = strlen(slash);
                if (sz <= baselen + len)
                        return NULL;
                memcpy(buf + baselen, slash, len + 1);
        }
        return buf;
}

/*
 * First, one directory to try is determined by the following algorithm.
 *
 * (0) If "strict" is given, the path is used as given and no DWIM is
 *     done. Otherwise:
 * (1) "~/path" to mean path under the running user's home directory;
 * (2) "~user/path" to mean path under named user's home directory;
 * (3) "relative/path" to mean cwd relative directory; or
 * (4) "/absolute/path" to mean absolute directory.
 *
 * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 * what we try.
 *
 * Second, we try chdir() to that.  Upon failure, we return NULL.
 *
 * Then, we try if the current directory is a valid git repository.
 * Upon failure, we return NULL.
 *
 * If all goes well, we return the directory we used to chdir() (but
 * before ~user is expanded), avoiding getcwd() resolving symbolic
 * links.  User relative paths are also returned as they are given,
 * except DWIM suffixing.
 */
char *enter_repo(char *path, int strict)
{
        static char used_path[PATH_MAX];
        static char validated_path[PATH_MAX];

        if (!path)
                return NULL;

        if (!strict) {
                static const char *suffix[] = {
                        ".git/.git", "/.git", ".git", "", NULL,
                };
                int len = strlen(path);
                int i;
                while ((1 < len) && (path[len-1] == '/')) {
                        path[len-1] = 0;
                        len--;
                }
                if (PATH_MAX <= len)
                        return NULL;
                if (path[0] == '~') {
                        if (!user_path(used_path, path, PATH_MAX))
                                return NULL;
                        strcpy(validated_path, path);
                        path = used_path;
                }
                else if (PATH_MAX - 10 < len)
                        return NULL;
                else {
                        path = strcpy(used_path, path);
                        strcpy(validated_path, path);
                }
                len = strlen(path);
                for (i = 0; suffix[i]; i++) {
                        strcpy(path + len, suffix[i]);
                        if (!access(path, F_OK)) {
                                strcat(validated_path, suffix[i]);
                                break;
                        }
                }
                if (!suffix[i] || chdir(path))
                        return NULL;
                path = validated_path;
        }
        else if (chdir(path))
                return NULL;

        if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
            validate_symref("HEAD") == 0) {
                putenv("GIT_DIR=.");
                check_repository_format();
                return path;
        }

        return NULL;
}