# Source code for fontTools.cffLib.specializer

    # -*- coding: utf-8 -*-

    """T2CharString operator specializer and generalizer.

    PostScript glyph drawing operations can be expressed in multiple different
    ways. For example, as well as the ``lineto`` operator, there is also a
    ``hlineto`` operator which draws a horizontal line, removing the need to
    specify a ``dx`` coordinate, and a ``vlineto`` operator which draws a
    vertical line, removing the need to specify a ``dy`` coordinate. As well
    as decompiling :class:`fontTools.misc.psCharStrings.T2CharString` objects
    into lists of operations, this module allows for conversion between general
    and specific forms of the operation.

    """

    from fontTools.cffLib import maxStackLimit

    def stringToProgram(string):
        if isinstance(string, str):
            string = string.split()
        program = []
        for token in string:
            try:
                token = int(token)
            except ValueError:
                try:
                    token = float(token)
                except ValueError:
                    pass
            program.append(token)
        return program

    def programToString(program):
        return " ".join(str(x) for x in program)

    def programToCommands(program, getNumRegions=None):
        """Takes a T2CharString program list and returns list of commands.
        Each command is a two-tuple of commandname,arg-list.  The commandname might
        be empty string if no commandname shall be emitted (used for glyph width,
        hintmask/cntrmask argument, as well as stray arguments at the end of the
        program (🤷).
        'getNumRegions' may be None, or a callable object. It must return the
        number of regions. 'getNumRegions' takes a single argument, vsindex. It
        returns the numRegions for the vsindex.
        The Charstring may or may not start with a width value. If the first
        non-blend operator has an odd number of arguments, then the first argument is
        a width, and is popped off. This is complicated with blend operators, as
        there may be more than one before the first hint or moveto operator, and each
        one reduces several arguments to just one list argument. We have to sum the
        number of arguments that are not part of the blend arguments, and all the
        'numBlends' values. We could instead have said that by definition, if there
        is a blend operator, there is no width value, since CFF2 Charstrings don't
        have width values. I discussed this with Behdad, and we are allowing for an
        initial width value in this case because developers may assemble a CFF2
        charstring from CFF Charstrings, which could have width values.
        """

        seenWidthOp = False
        vsIndex = 0
        lenBlendStack = 0
        lastBlendIndex = 0
        commands = []
        stack = []
        it = iter(program)

        for token in it:
            if not isinstance(token, str):
                stack.append(token)
                continue

            if token == "blend":
                assert getNumRegions is not None
                numSourceFonts = 1 + getNumRegions(vsIndex)
                # replace the blend op args on the stack with a single list
                # containing all the blend op args.
                numBlends = stack[-1]
                numBlendArgs = numBlends * numSourceFonts + 1
                # replace first blend op by a list of the blend ops.
                stack[-numBlendArgs:] = [stack[-numBlendArgs:]]
                lenStack = len(stack)
                lenBlendStack += numBlends + lenStack - 1
                lastBlendIndex = lenStack
                # if a blend op exists, this is or will be a CFF2 charstring.
                continue

            elif token == "vsindex":
                vsIndex = stack[-1]
                assert type(vsIndex) is int

            elif (not seenWidthOp) and token in {
                "hstem",
                "hstemhm",
                "vstem",
                "vstemhm",
                "cntrmask",
                "hintmask",
                "hmoveto",
                "vmoveto",
                "rmoveto",
                "endchar",
            }:
                seenWidthOp = True
                parity = token in {"hmoveto", "vmoveto"}
                if lenBlendStack:
                    # lenBlendStack has the number of args represented by the last blend
                    # arg and all the preceding args. We need to now add the number of
                    # args following the last blend arg.
                    numArgs = lenBlendStack + len(stack[lastBlendIndex:])
                else:
                    numArgs = len(stack)
                if numArgs and (numArgs % 2) ^ parity:
                    width = stack.pop(0)
                    commands.append(("", [width]))

            if token in {"hintmask", "cntrmask"}:
                if stack:
                    commands.append(("", stack))
                commands.append((token, []))
                commands.append(("", [next(it)]))
            else:
                commands.append((token, stack))
            stack = []
        if stack:
            commands.append(("", stack))
        return commands

    def _flattenBlendArgs(args):
        token_list = []
        for arg in args:
            if isinstance(arg, list):
                token_list.extend(arg)
                token_list.append("blend")
            else:
                token_list.append(arg)
        return token_list

    def commandsToProgram(commands):
        """Takes a commands list as returned by programToCommands() and converts
        it back to a T2CharString program list."""
        program = []
        for op, args in commands:
            if any(isinstance(arg, list) for arg in args):
                args = _flattenBlendArgs(args)
            program.extend(args)
            if op:
                program.append(op)
        return program

    def _everyN(el, n):
        """Group the list el into groups of size n"""
        l = len(el)
        if l % n != 0:
            raise ValueError(el)
        for i in range(0, l, n):
            yield el[i : i + n]

    class _GeneralizerDecombinerCommandsMap(object):
        @staticmethod
        def rmoveto(args):
            if len(args) != 2:
                raise ValueError(args)
            yield ("rmoveto", args)

        @staticmethod
        def hmoveto(args):
            if len(args) != 1:
                raise ValueError(args)
            yield ("rmoveto", [args[0], 0])

        @staticmethod
        def vmoveto(args):
            if len(args) != 1:
                raise ValueError(args)
            yield ("rmoveto", [0, args[0]])

        @staticmethod
        def rlineto(args):
            if not args:
                raise ValueError(args)
            for args in _everyN(args, 2):
                yield ("rlineto", args)

        @staticmethod
        def hlineto(args):
            if not args:
                raise ValueError(args)
            it = iter(args)
            try:
                while True:
                    yield ("rlineto", [next(it), 0])
                    yield ("rlineto", [0, next(it)])
            except StopIteration:
                pass

        @staticmethod
        def vlineto(args):
            if not args:
                raise ValueError(args)
            it = iter(args)
            try:
                while True:
                    yield ("rlineto", [0, next(it)])
                    yield ("rlineto", [next(it), 0])
            except StopIteration:
                pass

        @staticmethod
        def rrcurveto(args):
            if not args:
                raise ValueError(args)
            for args in _everyN(args, 6):
                yield ("rrcurveto", args)

        @staticmethod
        def hhcurveto(args):
            l = len(args)
            if l < 4 or l % 4 > 1:
                raise ValueError(args)
            if l % 2 == 1:
                yield ("rrcurveto", [args[1], args[0], args[2], args[3], args[4], 0])
                args = args[5:]
            for args in _everyN(args, 4):
                yield ("rrcurveto", [args[0], 0, args[1], args[2], args[3], 0])

        @staticmethod
        def vvcurveto(args):
            l = len(args)
            if l < 4 or l % 4 > 1:
                raise ValueError(args)
            if l % 2 == 1:
                yield ("rrcurveto", [args[0], args[1], args[2], args[3], 0, args[4]])
                args = args[5:]
            for args in _everyN(args, 4):
                yield ("rrcurveto", [0, args[0], args[1], args[2], 0, args[3]])

        @staticmethod
        def hvcurveto(args):
            l = len(args)
            if l < 4 or l % 8 not in {0, 1, 4, 5}:
                raise ValueError(args)
            last_args = None
            if l % 2 == 1:
                lastStraight = l % 8 == 5
                args, last_args = args[:-5], args[-5:]
            it = _everyN(args, 4)
            try:
                while True:
                    args = next(it)
                    yield ("rrcurveto", [args[0], 0, args[1], args[2], 0, args[3]])
                    args = next(it)
                    yield ("rrcurveto", [0, args[0], args[1], args[2], args[3], 0])
            except StopIteration:
                pass
            if last_args:
                args = last_args
                if lastStraight:
                    yield ("rrcurveto", [args[0], 0, args[1], args[2], args[4], args[3]])
                else:
                    yield ("rrcurveto", [0, args[0], args[1], args[2], args[3], args[4]])

        @staticmethod
        def vhcurveto(args):
            l = len(args)
            if l < 4 or l % 8 not in {0, 1, 4, 5}:
                raise ValueError(args)
            last_args = None
            if l % 2 == 1:
                lastStraight = l % 8 == 5
                args, last_args = args[:-5], args[-5:]
            it = _everyN(args, 4)
            try:
                while True:
                    args = next(it)
                    yield ("rrcurveto", [0, args[0], args[1], args[2], args[3], 0])
                    args = next(it)
                    yield ("rrcurveto", [args[0], 0, args[1], args[2], 0, args[3]])
            except StopIteration:
                pass
            if last_args:
                args = last_args
                if lastStraight:
                    yield ("rrcurveto", [0, args[0], args[1], args[2], args[3], args[4]])
                else:
                    yield ("rrcurveto", [args[0], 0, args[1], args[2], args[4], args[3]])

        @staticmethod
        def rcurveline(args):
            l = len(args)
            if l < 8 or l % 6 != 2:
                raise ValueError(args)
            args, last_args = args[:-2], args[-2:]
            for args in _everyN(args, 6):
                yield ("rrcurveto", args)
            yield ("rlineto", last_args)

        @staticmethod
        def rlinecurve(args):
            l = len(args)
            if l < 8 or l % 2 != 0:
                raise ValueError(args)
            args, last_args = args[:-6], args[-6:]
            for args in _everyN(args, 2):
                yield ("rlineto", args)
            yield ("rrcurveto", last_args)

    def _convertBlendOpToArgs(blendList):
        # args is list of blend op args. Since we are supporting
        # recursive blend op calls, some of these args may also
        # be a list of blend op args, and need to be converted before
        # we convert the current list.
        if any([isinstance(arg, list) for arg in blendList]):
            args = [
                i
                for e in blendList
                for i in (_convertBlendOpToArgs(e) if isinstance(e, list) else [e])
            ]
        else:
            args = blendList

        # We now know that blendList contains a blend op argument list, even if
        # some of the args are lists that each contain a blend op argument list.
        # 	Convert from:
        # 		[default font arg sequence x0,...,xn] + [delta tuple for x0] + ... + [delta tuple for xn]
        # 	to:
        # 		[ [x0] + [delta tuple for x0],
        #                 ...,
        #          [xn] + [delta tuple for xn] ]
        numBlends = args[-1]
        # Can't use args.pop() when the args are being used in a nested list
        # comprehension. See calling context
        args = args[:-1]

        l = len(args)
        numRegions = l // numBlends - 1
        if not (numBlends * (numRegions + 1) == l):
            raise ValueError(blendList)

        defaultArgs = [[arg] for arg in args[:numBlends]]
        deltaArgs = args[numBlends:]
        numDeltaValues = len(deltaArgs)
        deltaList = [
            deltaArgs[i : i + numRegions] for i in range(0, numDeltaValues, numRegions)
        ]
        blend_args = [a + b + [1] for a, b in zip(defaultArgs, deltaList)]
        return blend_args

    def generalizeCommands(commands, ignoreErrors=False):
        result = []
        mapping = _GeneralizerDecombinerCommandsMap
        for op, args in commands:
            # First, generalize any blend args in the arg list.
            if any([isinstance(arg, list) for arg in args]):
                try:
                    args = [
                        n
                        for arg in args
                        for n in (
                            _convertBlendOpToArgs(arg) if isinstance(arg, list) else [arg]
                        )
                    ]
                except ValueError:
                    if ignoreErrors:
                        # Store op as data, such that consumers of commands do not have to
                        # deal with incorrect number of arguments.
                        result.append(("", args))
                        result.append(("", [op]))
                    else:
                        raise

            func = getattr(mapping, op, None)
            if func is None:
                result.append((op, args))
                continue
            try:
                for command in func(args):
                    result.append(command)
            except ValueError:
                if ignoreErrors:
                    # Store op as data, such that consumers of commands do not have to
                    # deal with incorrect number of arguments.
                    result.append(("", args))
                    result.append(("", [op]))
                else:
                    raise
        return result

    def generalizeProgram(program, getNumRegions=None, **kwargs):
        return commandsToProgram(
            generalizeCommands(programToCommands(program, getNumRegions), **kwargs)
        )

    def _categorizeVector(v):
        """
        Takes X,Y vector v and returns one of r, h, v, or 0 depending on which
        of X and/or Y are zero, plus tuple of nonzero ones.  If both are zero,
        it returns a single zero still.

        >>> _categorizeVector((0,0))
        ('0', (0,))
        >>> _categorizeVector((1,0))
        ('h', (1,))
        >>> _categorizeVector((0,2))
        ('v', (2,))
        >>> _categorizeVector((1,2))
        ('r', (1, 2))
        """
        if not v[0]:
            if not v[1]:
                return "0", v[:1]
            else:
                return "v", v[1:]
        else:
            if not v[1]:
                return "h", v[:1]
            else:
                return "r", v

    def _mergeCategories(a, b):
        if a == "0":
            return b
        if b == "0":
            return a
        if a == b:
            return a
        return None

    def _negateCategory(a):
        if a == "h":
            return "v"
        if a == "v":
            return "h"
        assert a in "0r"
        return a

    def _convertToBlendCmds(args):
        # return a list of blend commands, and
        # the remaining non-blended args, if any.
        num_args = len(args)
        stack_use = 0
        new_args = []
        i = 0
        while i < num_args:
            arg = args[i]
            i += 1
            if not isinstance(arg, list):
                new_args.append(arg)
                stack_use += 1
            else:
                prev_stack_use = stack_use
                # The arg is a tuple of blend values.
                # These are each (master 0,delta 1..delta n, 1)
                # Combine as many successive tuples as we can,
                # up to the max stack limit.
                num_sources = len(arg) - 1
                blendlist = [arg]
                stack_use += 1 + num_sources  # 1 for the num_blends arg

                # if we are here, max stack is the CFF2 max stack.
                # I use the CFF2 max stack limit here rather than
                # the 'maxstack' chosen by the client, as the default
                # maxstack may have been used unintentionally. For all
                # the other operators, this just produces a little less
                # optimization, but here it puts a hard (and low) limit
                # on the number of source fonts that can be used.
                #
                # Make sure the stack depth does not exceed (maxstack - 1), so
                # that subroutinizer can insert subroutine calls at any point.
                while (
                    (i < num_args)
                    and isinstance(args[i], list)
                    and stack_use + num_sources < maxStackLimit
                ):
                    blendlist.append(args[i])
                    i += 1
                    stack_use += num_sources
                # blendList now contains as many single blend tuples as can be
                # combined without exceeding the CFF2 stack limit.
                num_blends = len(blendlist)
                # append the 'num_blends' default font values
                blend_args = []
                for arg in blendlist:
                    blend_args.append(arg[0])
                for arg in blendlist:
                    assert arg[-1] == 1
                    blend_args.extend(arg[1:-1])
                blend_args.append(num_blends)
                new_args.append(blend_args)
                stack_use = prev_stack_use + num_blends

        return new_args

    def _addArgs(a, b):
        if isinstance(b, list):
            if isinstance(a, list):
                if len(a) != len(b) or a[-1] != b[-1]:
                    raise ValueError()
                return [_addArgs(va, vb) for va, vb in zip(a[:-1], b[:-1])] + [a[-1]]
            else:
                a, b = b, a
        if isinstance(a, list):
            assert a[-1] == 1
            return [_addArgs(a[0], b)] + a[1:]
        return a + b

    def _argsStackUse(args):
        stackLen = 0
        maxLen = 0
        for arg in args:
            if type(arg) is list:
                # Blended arg
                maxLen = max(maxLen, stackLen + _argsStackUse(arg))
                stackLen += arg[-1]
            else:
                stackLen += 1
        return max(stackLen, maxLen)

    def specializeCommands(
        commands,
        ignoreErrors=False,
        generalizeFirst=True,
        preserveTopology=False,
        maxstack=48,
    ):
        # We perform several rounds of optimizations.  They are carefully ordered and are:
        #
        # 0. Generalize commands.
        #    This ensures that they are in our expected simple form, with each line/curve only
        #    having arguments for one segment, and using the generic form (rlineto/rrcurveto).
        #    If caller is sure the input is in this form, they can turn off generalization to
        #    save time.
        #
        # 1. Combine successive rmoveto operations.
        #
        # 2. Specialize rmoveto/rlineto/rrcurveto operators into horizontal/vertical variants.
        #    We specialize into some, made-up, variants as well, which simplifies following
        #    passes.
        #
        # 3. Merge or delete redundant operations, to the extent requested.
        #    OpenType spec declares point numbers in CFF undefined.  As such, we happily
        #    change topology.  If client relies on point numbers (in GPOS anchors, or for
        #    hinting purposes(what?)) they can turn this off.
        #
        # 4. Peephole optimization to revert back some of the h/v variants back into their
        #    original "relative" operator (rline/rrcurveto) if that saves a byte.
        #
        # 5. Combine adjacent operators when possible, minding not to go over max stack size.
        #
        # 6. Resolve any remaining made-up operators into real operators.
        #
        # I have convinced myself that this produces optimal bytecode (except for, possibly
        # one byte each time maxstack size prohibits combining.)  YMMV, but you'd be wrong. :-)
        # A dynamic-programming approach can do the same but would be significantly slower.
        #
        # 7. For any args which are blend lists, convert them to a blend command.

        # 0. Generalize commands.
        if generalizeFirst:
            commands = generalizeCommands(commands, ignoreErrors=ignoreErrors)
        else:
            commands = list(commands)  # Make copy since we modify in-place later.

        # 1. Combine successive rmoveto operations.
        for i in range(len(commands) - 1, 0, -1):
            if "rmoveto" == commands[i][0] == commands[i - 1][0]:
                v1, v2 = commands[i - 1][1], commands[i][1]
                commands[i - 1] = (
                    "rmoveto",
                    [_addArgs(v1[0], v2[0]), _addArgs(v1[1], v2[1])],
                )
                del commands[i]

        # 2. Specialize rmoveto/rlineto/rrcurveto operators into horizontal/vertical variants.
        #
        # We, in fact, specialize into more, made-up, variants that special-case when both
        # X and Y components are zero.  This simplifies the following optimization passes.
        # This case is rare, but OCD does not let me skip it.
        #
        # After this round, we will have four variants that use the following mnemonics:
        #
        #  - 'r' for relative,   ie. non-zero X and non-zero Y,
        #  - 'h' for horizontal, ie. zero X and non-zero Y,
        #  - 'v' for vertical,   ie. non-zero X and zero Y,
        #  - '0' for zeros,      ie. zero X and zero Y.
        #
        # The '0' pseudo-operators are not part of the spec, but help simplify the following
        # optimization rounds.  We resolve them at the end.  So, after this, we will have four
        # moveto and four lineto variants:
        #
        #  - 0moveto, 0lineto
        #  - hmoveto, hlineto
        #  - vmoveto, vlineto
        #  - rmoveto, rlineto
        #
        # and sixteen curveto variants.  For example, a '0hcurveto' operator means a curve
        # dx0,dy0,dx1,dy1,dx2,dy2,dx3,dy3 where dx0, dx1, and dy3 are zero but not dx3.
        # An 'rvcurveto' means dx3 is zero but not dx0,dy0,dy3.
        #
        # There are nine different variants of curves without the '0'.  Those nine map exactly
        # to the existing curve variants in the spec: rrcurveto, and the four variants hhcurveto,
        # vvcurveto, hvcurveto, and vhcurveto each cover two cases, one with an odd number of
        # arguments and one without.  Eg. an hhcurveto with an extra argument (odd number of
        # arguments) is in fact an rhcurveto.  The operators in the spec are designed such that
        # all four of rhcurveto, rvcurveto, hrcurveto, and vrcurveto are encodable for one curve.
        #
        # Of the curve types with '0', the 00curveto is equivalent to a lineto variant.  The rest
        # of the curve types with a 0 need to be encoded as a h or v variant.  Ie. a '0' can be
        # thought of a "don't care" and can be used as either an 'h' or a 'v'.  As such, we always
        # encode a number 0 as argument when we use a '0' variant.  Later on, we can just substitute
        # the '0' with either 'h' or 'v' and it works.
        #
        # When we get to curve splines however, things become more complicated...  XXX finish this.
        # There's one more complexity with splines.  If one side of the spline is not horizontal or
        # vertical (or zero), ie. if it's 'r', then it limits which spline types we can encode.
        # Only hhcurveto and vvcurveto operators can encode a spline starting with 'r', and
        # only hvcurveto and vhcurveto operators can encode a spline ending with 'r'.
        # This limits our merge opportunities later.
        #
        for i in range(len(commands)):
            op, args = commands[i]

            if op in {"rmoveto", "rlineto"}:
                c, args = _categorizeVector(args)
                commands[i] = c + op[1:], args
                continue

            if op == "rrcurveto":
                c1, args1 = _categorizeVector(args[:2])
                c2, args2 = _categorizeVector(args[-2:])
                commands[i] = c1 + c2 + "curveto", args1 + args[2:4] + args2
                continue

        # 3. Merge or delete redundant operations, to the extent requested.
        #
        # TODO
        # A 0moveto that comes before all other path operations can be removed.
        # though I find conflicting evidence for this.
        #
        # TODO
        # "If hstem and vstem hints are both declared at the beginning of a
        # CharString, and this sequence is followed directly by the hintmask or
        # cntrmask operators, then the vstem hint operator (or, if applicable,
        # the vstemhm operator) need not be included."
        #
        # "The sequence and form of a CFF2 CharString program may be represented as:
        # {hs* vs* cm* hm* mt subpath}? {mt subpath}*"
        #
        # https://www.microsoft.com/typography/otspec/cff2charstr.htm#section3.1
        #
        # For Type2 CharStrings the sequence is:
        # w? {hs* vs* cm* hm* mt subpath}? {mt subpath}* endchar"

        # Some other redundancies change topology (point numbers).
        if not preserveTopology:
            for i in range(len(commands) - 1, -1, -1):
                op, args = commands[i]

                # A 00curveto is demoted to a (specialized) lineto.
                if op == "00curveto":
                    assert len(args) == 4
                    c, args = _categorizeVector(args[1:3])
                    op = c + "lineto"
                    commands[i] = op, args
                    # and then...

                # A 0lineto can be deleted.
                if op == "0lineto":
                    del commands[i]
                    continue

                # Merge adjacent hlineto's and vlineto's.
                # In CFF2 charstrings from variable fonts, each
                # arg item may be a list of blendable values, one from
                # each source font.
                if i and op in {"hlineto", "vlineto"} and (op == commands[i - 1][0]):
                    _, other_args = commands[i - 1]
                    assert len(args) == 1 and len(other_args) == 1
                    try:
                        new_args = [_addArgs(args[0], other_args[0])]
                    except ValueError:
                        continue
                    commands[i - 1] = (op, new_args)
                    del commands[i]
                    continue

        # 4. Peephole optimization to revert back some of the h/v variants back into their
        #    original "relative" operator (rline/rrcurveto) if that saves a byte.
        for i in range(1, len(commands) - 1):
            op, args = commands[i]
            prv, nxt = commands[i - 1][0], commands[i + 1][0]

            if op in {"0lineto", "hlineto", "vlineto"} and prv == nxt == "rlineto":
                assert len(args) == 1
                args = [0, args[0]] if op[0] == "v" else [args[0], 0]
                commands[i] = ("rlineto", args)
                continue

            if op[2:] == "curveto" and len(args) == 5 and prv == nxt == "rrcurveto":
                assert (op[0] == "r") ^ (op[1] == "r")
                if op[0] == "v":
                    pos = 0
                elif op[0] != "r":
                    pos = 1
                elif op[1] == "v":
                    pos = 4
                else:
                    pos = 5
                # Insert, while maintaining the type of args (can be tuple or list).
                args = args[:pos] + type(args)((0,)) + args[pos:]
                commands[i] = ("rrcurveto", args)
                continue

        # 5. Combine adjacent operators when possible, minding not to go over max stack size.
        stackUse = _argsStackUse(commands[-1][1]) if commands else 0
        for i in range(len(commands) - 1, 0, -1):
            op1, args1 = commands[i - 1]
            op2, args2 = commands[i]
            new_op = None

            # Merge logic...
            if {op1, op2} <= {"rlineto", "rrcurveto"}:
                if op1 == op2:
                    new_op = op1
                else:
                    l = len(args2)
                    if op2 == "rrcurveto" and l == 6:
                        new_op = "rlinecurve"
                    elif l == 2:
                        new_op = "rcurveline"

            elif (op1, op2) in {("rlineto", "rlinecurve"), ("rrcurveto", "rcurveline")}:
                new_op = op2

            elif {op1, op2} == {"vlineto", "hlineto"}:
                new_op = op1

            elif "curveto" == op1[2:] == op2[2:]:
                d0, d1 = op1[:2]
                d2, d3 = op2[:2]

                if d1 == "r" or d2 == "r" or d0 == d3 == "r":
                    continue

                d = _mergeCategories(d1, d2)
                if d is None:
                    continue
                if d0 == "r":
                    d = _mergeCategories(d, d3)
                    if d is None:
                        continue
                    new_op = "r" + d + "curveto"
                elif d3 == "r":
                    d0 = _mergeCategories(d0, _negateCategory(d))
                    if d0 is None:
                        continue
                    new_op = d0 + "r" + "curveto"
                else:
                    d0 = _mergeCategories(d0, d3)
                    if d0 is None:
                        continue
                    new_op = d0 + d + "curveto"

            # Make sure the stack depth does not exceed (maxstack - 1), so
            # that subroutinizer can insert subroutine calls at any point.
            args1StackUse = _argsStackUse(args1)
            combinedStackUse = max(args1StackUse, len(args1) + stackUse)
            if new_op and combinedStackUse < maxstack:
                commands[i - 1] = (new_op, args1 + args2)
                del commands[i]
                stackUse = combinedStackUse
            else:
                stackUse = args1StackUse

        # 6. Resolve any remaining made-up operators into real operators.
        for i in range(len(commands)):
            op, args = commands[i]

            if op in {"0moveto", "0lineto"}:
                commands[i] = "h" + op[1:], args
                continue

            if op[2:] == "curveto" and op[:2] not in {"rr", "hh", "vv", "vh", "hv"}:
                l = len(args)

                op0, op1 = op[:2]
                if (op0 == "r") ^ (op1 == "r"):
                    assert l % 2 == 1
                if op0 == "0":
                    op0 = "h"
                if op1 == "0":
                    op1 = "h"
                if op0 == "r":
                    op0 = op1
                if op1 == "r":
                    op1 = _negateCategory(op0)
                assert {op0, op1} <= {"h", "v"}, (op0, op1)

                if l % 2:
                    if op0 != op1:  # vhcurveto / hvcurveto
                        if (op0 == "h") ^ (l % 8 == 1):
                            # Swap last two args order
                            args = args[:-2] + args[-1:] + args[-2:-1]
                    else:  # hhcurveto / vvcurveto
                        if op0 == "h":  # hhcurveto
                            # Swap first two args order
                            args = args[1:2] + args[:1] + args[2:]

                commands[i] = op0 + op1 + "curveto", args
                continue

        # 7. For any series of args which are blend lists, convert the series to a single blend arg.
        for i in range(len(commands)):
            op, args = commands[i]
            if any(isinstance(arg, list) for arg in args):
                commands[i] = op, _convertToBlendCmds(args)

        return commands

    def specializeProgram(program, getNumRegions=None, **kwargs):
        return commandsToProgram(
            specializeCommands(programToCommands(program, getNumRegions), **kwargs)
        )

    if __name__ == "__main__":
        import sys

        if len(sys.argv) == 1:
            import doctest

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

        import argparse

        parser = argparse.ArgumentParser(
            "fonttools cffLib.specializer",
            description="CFF CharString generalizer/specializer",
        )
        parser.add_argument("program", metavar="command", nargs="*", help="Commands.")
        parser.add_argument(
            "--num-regions",
            metavar="NumRegions",
            nargs="*",
            default=None,
            help="Number of variable-font regions for blend opertaions.",
        )
        parser.add_argument(
            "--font",
            metavar="FONTFILE",
            default=None,
            help="CFF2 font to specialize.",
        )
        parser.add_argument(
            "-o",
            "--output-file",
            type=str,
            help="Output font file name.",
        )

        options = parser.parse_args(sys.argv[1:])

        if options.program:
            getNumRegions = (
                None
                if options.num_regions is None
                else lambda vsIndex: int(
                    options.num_regions[0 if vsIndex is None else vsIndex]
                )
            )

            program = stringToProgram(options.program)
            print("Program:")
            print(programToString(program))
            commands = programToCommands(program, getNumRegions)
            print("Commands:")
            print(commands)
            program2 = commandsToProgram(commands)
            print("Program from commands:")
            print(programToString(program2))
            assert program == program2
            print("Generalized program:")
            print(programToString(generalizeProgram(program, getNumRegions)))
            print("Specialized program:")
            print(programToString(specializeProgram(program, getNumRegions)))

        if options.font:
            from fontTools.ttLib import TTFont

            font = TTFont(options.font)
            cff2 = font["CFF2"].cff.topDictIndex[0]
            charstrings = cff2.CharStrings
            for glyphName in charstrings.keys():
                charstring = charstrings[glyphName]
                charstring.decompile()
                getNumRegions = charstring.private.getNumRegions
                charstring.program = specializeProgram(
                    charstring.program, getNumRegions, maxstack=maxStackLimit
                )

            if options.output_file is None:
                from fontTools.misc.cliTools import makeOutputFileName

                outfile = makeOutputFileName(
                    options.font, overWrite=True, suffix=".specialized"
                )
            else:
                outfile = options.output_file
            if outfile:
                print("Saving", outfile)
                font.save(outfile)