# Source code for fontTools.misc.filenames

    """
    This module implements the algorithm for converting between a "user name" -
    something that a user can choose arbitrarily inside a font editor - and a file
    name suitable for use in a wide range of operating systems and filesystems.

    The `UFO 3 specification <http://unifiedfontobject.org/versions/ufo3/conventions/>`_
    provides an example of an algorithm for such conversion, which avoids illegal
    characters, reserved file names, ambiguity between upper- and lower-case
    characters, and clashes with existing files.

    This code was originally copied from
    `ufoLib <https://github.com/unified-font-object/ufoLib/blob/8747da7/Lib/ufoLib/filenames.py>`_
    by Tal Leming and is copyright (c) 2005-2016, The RoboFab Developers:

    -	Erik van Blokland
    -	Tal Leming
    -	Just van Rossum
    """

    illegalCharacters = r"\" * + / : < > ? [ \ ] | \0".split(" ")
    illegalCharacters += [chr(i) for i in range(1, 32)]
    illegalCharacters += [chr(0x7F)]
    reservedFileNames = "CON PRN AUX CLOCK$ NUL A:-Z: COM1".lower().split(" ")
    reservedFileNames += "LPT1 LPT2 LPT3 COM2 COM3 COM4".lower().split(" ")
    maxFileNameLength = 255

    class NameTranslationError(Exception):
        pass

    def userNameToFileName(userName, existing=[], prefix="", suffix=""):
        """Converts from a user name to a file name.

        Takes care to avoid illegal characters, reserved file names, ambiguity between
        upper- and lower-case characters, and clashes with existing files.

        Args:
                userName (str): The input file name.
                existing: A case-insensitive list of all existing file names.
                prefix: Prefix to be prepended to the file name.
                suffix: Suffix to be appended to the file name.

        Returns:
                A suitable filename.

        Raises:
                NameTranslationError: If no suitable name could be generated.

        Examples::

                >>> userNameToFileName("a") == "a"
                True
                >>> userNameToFileName("A") == "A_"
                True
                >>> userNameToFileName("AE") == "A_E_"
                True
                >>> userNameToFileName("Ae") == "A_e"
                True
                >>> userNameToFileName("ae") == "ae"
                True
                >>> userNameToFileName("aE") == "aE_"
                True
                >>> userNameToFileName("a.alt") == "a.alt"
                True
                >>> userNameToFileName("A.alt") == "A_.alt"
                True
                >>> userNameToFileName("A.Alt") == "A_.A_lt"
                True
                >>> userNameToFileName("A.aLt") == "A_.aL_t"
                True
                >>> userNameToFileName(u"A.alT") == "A_.alT_"
                True
                >>> userNameToFileName("T_H") == "T__H_"
                True
                >>> userNameToFileName("T_h") == "T__h"
                True
                >>> userNameToFileName("t_h") == "t_h"
                True
                >>> userNameToFileName("F_F_I") == "F__F__I_"
                True
                >>> userNameToFileName("f_f_i") == "f_f_i"
                True
                >>> userNameToFileName("Aacute_V.swash") == "A_acute_V_.swash"
                True
                >>> userNameToFileName(".notdef") == "_notdef"
                True
                >>> userNameToFileName("con") == "_con"
                True
                >>> userNameToFileName("CON") == "C_O_N_"
                True
                >>> userNameToFileName("con.alt") == "_con.alt"
                True
                >>> userNameToFileName("alt.con") == "alt._con"
                True
        """
        # the incoming name must be a str
        if not isinstance(userName, str):
            raise ValueError("The value for userName must be a string.")
        # establish the prefix and suffix lengths
        prefixLength = len(prefix)
        suffixLength = len(suffix)
        # replace an initial period with an _
        # if no prefix is to be added
        if not prefix and userName[0] == ".":
            userName = "_" + userName[1:]
        # filter the user name
        filteredUserName = []
        for character in userName:
            # replace illegal characters with _
            if character in illegalCharacters:
                character = "_"
            # add _ to all non-lower characters
            elif character != character.lower():
                character += "_"
            filteredUserName.append(character)
        userName = "".join(filteredUserName)
        # clip to 255
        sliceLength = maxFileNameLength - prefixLength - suffixLength
        userName = userName[:sliceLength]
        # test for illegal files names
        parts = []
        for part in userName.split("."):
            if part.lower() in reservedFileNames:
                part = "_" + part
            parts.append(part)
        userName = ".".join(parts)
        # test for clash
        fullName = prefix + userName + suffix
        if fullName.lower() in existing:
            fullName = handleClash1(userName, existing, prefix, suffix)
        # finished
        return fullName

    def handleClash1(userName, existing=[], prefix="", suffix=""):
        """
        existing should be a case-insensitive list
        of all existing file names.

        >>> prefix = ("0" * 5) + "."
        >>> suffix = "." + ("0" * 10)
        >>> existing = ["a" * 5]

        >>> e = list(existing)
        >>> handleClash1(userName="A" * 5, existing=e,
        ...		prefix=prefix, suffix=suffix) == (
        ... 	'00000.AAAAA000000000000001.0000000000')
        True

        >>> e = list(existing)
        >>> e.append(prefix + "aaaaa" + "1".zfill(15) + suffix)
        >>> handleClash1(userName="A" * 5, existing=e,
        ...		prefix=prefix, suffix=suffix) == (
        ... 	'00000.AAAAA000000000000002.0000000000')
        True

        >>> e = list(existing)
        >>> e.append(prefix + "AAAAA" + "2".zfill(15) + suffix)
        >>> handleClash1(userName="A" * 5, existing=e,
        ...		prefix=prefix, suffix=suffix) == (
        ... 	'00000.AAAAA000000000000001.0000000000')
        True
        """
        # if the prefix length + user name length + suffix length + 15 is at
        # or past the maximum length, silce 15 characters off of the user name
        prefixLength = len(prefix)
        suffixLength = len(suffix)
        if prefixLength + len(userName) + suffixLength + 15 > maxFileNameLength:
            l = prefixLength + len(userName) + suffixLength + 15
            sliceLength = maxFileNameLength - l
            userName = userName[:sliceLength]
        finalName = None
        # try to add numbers to create a unique name
        counter = 1
        while finalName is None:
            name = userName + str(counter).zfill(15)
            fullName = prefix + name + suffix
            if fullName.lower() not in existing:
                finalName = fullName
                break
            else:
                counter += 1
            if counter >= 999999999999999:
                break
        # if there is a clash, go to the next fallback
        if finalName is None:
            finalName = handleClash2(existing, prefix, suffix)
        # finished
        return finalName

    def handleClash2(existing=[], prefix="", suffix=""):
        """
        existing should be a case-insensitive list
        of all existing file names.

        >>> prefix = ("0" * 5) + "."
        >>> suffix = "." + ("0" * 10)
        >>> existing = [prefix + str(i) + suffix for i in range(100)]

        >>> e = list(existing)
        >>> handleClash2(existing=e, prefix=prefix, suffix=suffix) == (
        ... 	'00000.100.0000000000')
        True

        >>> e = list(existing)
        >>> e.remove(prefix + "1" + suffix)
        >>> handleClash2(existing=e, prefix=prefix, suffix=suffix) == (
        ... 	'00000.1.0000000000')
        True

        >>> e = list(existing)
        >>> e.remove(prefix + "2" + suffix)
        >>> handleClash2(existing=e, prefix=prefix, suffix=suffix) == (
        ... 	'00000.2.0000000000')
        True
        """
        # calculate the longest possible string
        maxLength = maxFileNameLength - len(prefix) - len(suffix)
        maxValue = int("9" * maxLength)
        # try to find a number
        finalName = None
        counter = 1
        while finalName is None:
            fullName = prefix + str(counter) + suffix
            if fullName.lower() not in existing:
                finalName = fullName
                break
            else:
                counter += 1
            if counter >= maxValue:
                break
        # raise an error if nothing has been found
        if finalName is None:
            raise NameTranslationError("No unique name could be found.")
        # finished
        return finalName

    if __name__ == "__main__":
        import doctest
        import sys

        sys.exit(doctest.testmod().failed)