/*
 * 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 *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 = (mode & ~0777) | 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;
}

/* We allow "recursive" symbolic links. Only within reason, though. */
#define MAXDEPTH 5

const char *make_absolute_path(const char *path)
{
        static char bufs[2][PATH_MAX + 1], *buf = bufs[0], *next_buf = bufs[1];
        char cwd[1024] = "";
        int buf_index = 1, len;

        int depth = MAXDEPTH;
        char *last_elem = NULL;
        struct stat st;

        if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX)
                die ("Too long path: %.*s", 60, path);

        while (depth--) {
                if (stat(buf, &st) || !S_ISDIR(st.st_mode)) {
                        char *last_slash = strrchr(buf, '/');
                        if (last_slash) {
                                *last_slash = '\0';
                                last_elem = xstrdup(last_slash + 1);
                        } else {
                                last_elem = xstrdup(buf);
                                *buf = '\0';
                        }
                }

                if (*buf) {
                        if (!*cwd && !getcwd(cwd, sizeof(cwd)))
                                die ("Could not get current working directory");

                        if (chdir(buf))
                                die ("Could not switch to '%s'", buf);
                }
                if (!getcwd(buf, PATH_MAX))
                        die ("Could not get current working directory");

                if (last_elem) {
                        int len = strlen(buf);
                        if (len + strlen(last_elem) + 2 > PATH_MAX)
                                die ("Too long path name: '%s/%s'",
                                                buf, last_elem);
                        buf[len] = '/';
                        strcpy(buf + len + 1, last_elem);
                        free(last_elem);
                        last_elem = NULL;
                }

                if (!lstat(buf, &st) && S_ISLNK(st.st_mode)) {
                        len = readlink(buf, next_buf, PATH_MAX);
                        if (len < 0)
                                die ("Invalid symlink: %s", buf);
                        next_buf[len] = '\0';
                        buf = next_buf;
                        buf_index = 1 - buf_index;
                        next_buf = bufs[buf_index];
                } else
                        break;
        }

        if (*cwd && chdir(cwd))
                die ("Could not change back to '%s'", cwd);

        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;
}