/*
 * 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 *current_dir(void)
{
        return getcwd(pathname, sizeof(pathname));
}

static int user_chdir(char *path)
{
        char *dir = path;

        if(*dir == '~') {               /* user-relative path */
                struct passwd *pw;
                char *slash = strchr(dir, '/');

                dir++;
                /* '~/' and '~' (no slash) means users own home-dir */
                if(!*dir || *dir == '/')
                        pw = getpwuid(getuid());
                else {
                        if (slash) {
                                *slash = '\0';
                                pw = getpwnam(dir);
                                *slash = '/';
                        }
                        else
                                pw = getpwnam(dir);
                }

                /* make sure we got something back that we can chdir() to */
                if(!pw || chdir(pw->pw_dir) < 0)
                        return -1;

                if(!slash || !slash[1]) /* no path following username */
                        return 0;

                dir = slash + 1;
        }

        /* ~foo/path/to/repo is now path/to/repo and we're in foo's homedir */
        if(chdir(dir) < 0)
                return -1;

        return 0;
}

char *enter_repo(char *path, int strict)
{
        if(!path)
                return NULL;

        if (strict) {
                if((path[0] != '/') || chdir(path) < 0)
                        return NULL;
        }
        else {
                if (!*path)
                        ; /* happy -- no chdir */
                else if (!user_chdir(path))
                        ; /* happy -- as given */
                else if (!user_chdir(mkpath("%s.git", path)))
                        ; /* happy -- uemacs --> uemacs.git */
                else
                        return NULL;
                (void)chdir(".git");
        }

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

        return NULL;
}