import os, errno

class opener(object):

    '''Open files relative to a base directory

    This class is used to hide the details of COW semantics and

    remote file access from higher level code.

    '''

    def __init__(self, base, audit=True):

        self.base = base

        if audit:

            self.auditor = util.path_auditor(base)

        else:

            self.auditor = util.always

        self.createmode = None

        self._trustnlink = None

    @util.propertycache

    def _can_symlink(self):

        return util.checklink(self.base)

    def _fixfilemode(self, name):

        if self.createmode is None:

            return

        os.chmod(name, self.createmode & 0666)

    def __call__(self, path, mode="r", text=False, atomictemp=False):

        r = util.checkosfilename(path)

        if r:

            raise Abort("%s: %r" % (r, path))

        self.auditor(path)

        f = os.path.join(self.base, path)

        if not text and "b" not in mode:

            mode += "b" # for that other OS

        nlink = -1

        dirname, basename = os.path.split(f)

        # If basename is empty, then the path is malformed because it points

        # to a directory. Let the posixfile() call below raise IOError.

        if basename and mode not in ('r', 'rb'):

            if atomictemp:

                if not os.path.isdir(dirname):

                    util.makedirs(dirname, self.createmode)

                return util.atomictempfile(f, mode, self.createmode)

            try:

                if 'w' in mode:

                    util.unlink(f)

                    nlink = 0

                else:

                    # nlinks() may behave differently for files on Windows

                    # shares if the file is open.

                    fd = util.posixfile(f)

                    nlink = util.nlinks(f)

                    if nlink < 1:

                        nlink = 2 # force mktempcopy (issue1922)

                    fd.close()

            except (OSError, IOError), e:

                if e.errno != errno.ENOENT:

                    raise

                nlink = 0

                if not os.path.isdir(dirname):

                    util.makedirs(dirname, self.createmode)

            if nlink > 0:

                if self._trustnlink is None:

                    self._trustnlink = nlink > 1 or util.checknlink(f)

                if nlink > 1 or not self._trustnlink:

                    util.rename(util.mktempcopy(f), f)

        fp = util.posixfile(f, mode)

        if nlink == 0:

            self._fixfilemode(f)

        return fp

    def symlink(self, src, dst):

        self.auditor(dst)

        linkname = os.path.join(self.base, dst)

        try:

            os.unlink(linkname)

        except OSError:

            pass

        dirname = os.path.dirname(linkname)

        if not os.path.exists(dirname):

            util.makedirs(dirname, self.createmode)

        if self._can_symlink:

            try:

                os.symlink(src, linkname)

            except OSError, err:

                raise OSError(err.errno, _('could not symlink to %r: %s') %

                              (src, err.strerror), linkname)

        else:

            f = self(dst, "w")

            f.write(src)

            f.close()

            self._fixfilemode(dst)