/*
 * 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"

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

static char *get_pathname(void)
{
        static char pathname_array[4][PATH_MAX];
        static int index;
        return pathname_array[3 & ++index];
}

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

char *mksnpath(char *buf, size_t n, const char *fmt, ...)
{
        va_list args;
        unsigned len;

        va_start(args, fmt);
        len = vsnprintf(buf, n, fmt, args);
        va_end(args);
        if (len >= n) {
                snprintf(buf, n, bad_path);
                return buf;
        }
        return cleanup_path(buf);
}

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

        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();
        char *pathname = get_pathname();
        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)
{
        const char *tmp;
        size_t n;

        tmp = getenv("TMPDIR");
        if (!tmp)
                tmp = "/tmp";
        n = snprintf(path, len, "%s/%s", tmp, template);
        if (len <= n) {
                errno = ENAMETOOLONG;
                return -1;
        }
        return mkstemp(path);
}


int validate_headref(const char *path)
{
        struct stat st;
        char *buf, buffer[256];
        unsigned char sha1[20];
        int fd;
        ssize_t len;

        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_in_full(fd, buffer, sizeof(buffer)-1);
        close(fd);

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

        /*
         * Is this a detached HEAD?
         */
        if (!get_sha1_hex(buffer, sha1))
                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_headref("HEAD") == 0) {
                setenv(GIT_DIR_ENVIRONMENT, ".", 1);
                check_repository_format();
                return path;
        }

        return NULL;
}

int adjust_shared_perm(const char *path)
{
        struct stat st;
        int mode;

        if (!shared_repository)
                return 0;
        if (lstat(path, &st) < 0)
                return -1;
        mode = st.st_mode;

        if (shared_repository) {
                int tweak = shared_repository;
                if (!(mode & S_IWUSR))
                        tweak &= ~0222;
                mode |= tweak;
        } else {
                /* Preserve old PERM_UMASK behaviour */
                if (mode & S_IWUSR)
                        mode |= S_IWGRP;
        }

        if (S_ISDIR(mode)) {
                mode |= FORCE_DIR_SET_GID;

                /* Copy read bits to execute bits */
                mode |= (shared_repository & 0444) >> 2;
        }

        if ((mode & st.st_mode) != mode && chmod(path, mode) < 0)
                return -2;
        return 0;
}

const char *make_relative_path(const char *abs, const char *base)
{
        static char buf[PATH_MAX + 1];
        int baselen;
        if (!base)
                return abs;
        baselen = strlen(base);
        if (prefixcmp(abs, base))
                return abs;
        if (abs[baselen] == '/')
                baselen++;
        else if (base[baselen - 1] != '/')
                return abs;
        strcpy(buf, abs + baselen);
        return buf;
}

/*
 * path = absolute path
 * buf = buffer of at least max(2, strlen(path)+1) bytes
 * It is okay if buf == path, but they should not overlap otherwise.
 *
 * Performs the following normalizations on path, storing the result in buf:
 * - Removes trailing slashes.
 * - Removes empty components.
 * - Removes "." components.
 * - Removes ".." components, and the components the precede them.
 * "" and paths that contain only slashes are normalized to "/".
 * Returns the length of the output.
 *
 * Note that this function is purely textual.  It does not follow symlinks,
 * verify the existence of the path, or make any system calls.
 */
int normalize_absolute_path(char *buf, const char *path)
{
        const char *comp_start = path, *comp_end = path;
        char *dst = buf;
        int comp_len;
        assert(buf);
        assert(path);

        while (*comp_start) {
                assert(*comp_start == '/');
                while (*++comp_end && *comp_end != '/')
                        ; /* nothing */
                comp_len = comp_end - comp_start;

                if (!strncmp("/",  comp_start, comp_len) ||
                    !strncmp("/.", comp_start, comp_len))
                        goto next;

                if (!strncmp("/..", comp_start, comp_len)) {
                        while (dst > buf && *--dst != '/')
                                ; /* nothing */
                        goto next;
                }

                memcpy(dst, comp_start, comp_len);
                dst += comp_len;
        next:
                comp_start = comp_end;
        }

        if (dst == buf)
                *dst++ = '/';

        *dst = '\0';
        return dst - buf;
}

/*
 * path = Canonical absolute path
 * prefix_list = Colon-separated list of absolute paths
 *
 * Determines, for each path in prefix_list, whether the "prefix" really
 * is an ancestor directory of path.  Returns the length of the longest
 * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 * is an ancestor.  (Note that this means 0 is returned if prefix_list is
 * "/".) "/foo" is not considered an ancestor of "/foobar".  Directories
 * are not considered to be their own ancestors.  path must be in a
 * canonical form: empty components, or "." or ".." components are not
 * allowed.  prefix_list may be null, which is like "".
 */
int longest_ancestor_length(const char *path, const char *prefix_list)
{
        char buf[PATH_MAX+1];
        const char *ceil, *colon;
        int len, max_len = -1;

        if (prefix_list == NULL || !strcmp(path, "/"))
                return -1;

        for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
                for (colon = ceil; *colon && *colon != ':'; colon++);
                len = colon - ceil;
                if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
                        continue;
                strlcpy(buf, ceil, len+1);
                len = normalize_absolute_path(buf, buf);
                /* Strip "trailing slashes" from "/". */
                if (len == 1)
                        len = 0;

                if (!strncmp(path, buf, len) &&
                    path[len] == '/' &&
                    len > max_len) {
                        max_len = len;
                }
        }

        return max_len;
}