"""
Convert user-provided internal UFO names to spec-compliant 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
"""

# Restrictions are taken mostly from
# https://docs.microsoft.com/en-gb/windows/win32/fileio/naming-a-file#naming-conventions.
#
# 1. Integer value zero, sometimes referred to as the ASCII NUL character.
# 2. Characters whose integer representations are in the range 1 to 31,
#    inclusive.
# 3. Various characters that (mostly) Windows and POSIX-y filesystems don't
#    allow, plus "(" and ")", as per the specification.
illegalCharacters = {
    "\x00",
    "\x01",
    "\x02",
    "\x03",
    "\x04",
    "\x05",
    "\x06",
    "\x07",
    "\x08",
    "\t",
    "\n",
    "\x0b",
    "\x0c",
    "\r",
    "\x0e",
    "\x0f",
    "\x10",
    "\x11",
    "\x12",
    "\x13",
    "\x14",
    "\x15",
    "\x16",
    "\x17",
    "\x18",
    "\x19",
    "\x1a",
    "\x1b",
    "\x1c",
    "\x1d",
    "\x1e",
    "\x1f",
    '"',
    "*",
    "+",
    "/",
    ":",
    "<",
    ">",
    "?",
    "[",
    "\\",
    "]",
    "(",
    ")",
    "|",
    "\x7f",
}
reservedFileNames = {
    "aux",
    "clock$",
    "com1",
    "com2",
    "com3",
    "com4",
    "com5",
    "com6",
    "com7",
    "com8",
    "com9",
    "con",
    "lpt1",
    "lpt2",
    "lpt3",
    "lpt4",
    "lpt5",
    "lpt6",
    "lpt7",
    "lpt8",
    "lpt9",
    "nul",
    "prn",
}
maxFileNameLength = 255


class NameTranslationError(Exception):
    pass


def userNameToFileName(userName: str, 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 string
    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=""):
    """A helper function that resolves collisions with existing names when choosing a filename.

    This function attempts to append an unused integer counter to the filename.

        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.

        >>> 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=""):
    """A helper function that resolves collisions with existing names when choosing a filename.

    This function is a fallback to :func:`handleClash1`. It attempts to append an unused integer counter to the filename.

        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::

          >>> 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

    doctest.testmod()
