# Source code for fontTools.voltLib.voltToFea

    """\
    MS VOLT ``.vtp`` to AFDKO ``.fea`` OpenType Layout converter.

    Usage
    -----

    To convert a VTP project file:

    .. code-block:: sh

        $ fonttools voltLib.voltToFea input.vtp output.fea

    It is also possible convert font files with `TSIV` table (as saved from Volt),
    in this case the glyph names used in the Volt project will be mapped to the
    actual glyph names in the font files when written to the feature file:

    .. code-block:: sh

        $ fonttools voltLib.voltToFea input.ttf output.fea

    The ``--quiet`` option can be used to suppress warnings.

    The ``--traceback`` can be used to get Python traceback in case of exceptions,
    instead of suppressing the traceback.

    Limitations
    -----------

    * Not all VOLT features are supported, the script will error if it it
      encounters something it does not understand. Please report an issue if this
      happens.
    * AFDKO feature file syntax for mark positioning is awkward and does not allow
      setting the mark coverage. It also defines mark anchors globally, as a result
      some mark positioning lookups might cover many marks than what was in the VOLT
      file. This should not be an issue in practice, but if it is then the only way
      is to modify the VOLT file or the generated feature file manually to use unique
      mark anchors for each lookup.
    * VOLT allows subtable breaks in any lookup type, but AFDKO feature file
      implementations vary in their support; currently AFDKO’s makeOTF supports
      subtable breaks in pair positioning lookups only, while FontTools’ feaLib
      support it for most substitution lookups and only some positioning lookups.
    """

    import logging
    import re
    from io import StringIO
    from graphlib import TopologicalSorter

    from fontTools.feaLib import ast
    from fontTools.ttLib import TTFont, TTLibError
    from fontTools.voltLib import ast as VAst
    from fontTools.voltLib.parser import Parser as VoltParser

    log = logging.getLogger("fontTools.voltLib.voltToFea")

    TABLES = ["GDEF", "GSUB", "GPOS"]

    def _flatten_group(group):
        ret = []
        if isinstance(group, (tuple, list)):
            for item in group:
                ret.extend(_flatten_group(item))
        elif hasattr(group, "enum"):
            ret.extend(_flatten_group(group.enum))
        else:
            ret.append(group)
        return ret

    # Topologically sort of group definitions to ensure that all groups are defined
    # before they are referenced. This is necessary because FEA requires it but
    # VOLT does not, see below.

    def sort_groups(groups):
        group_map = {group.name.lower(): group for group in groups}
        graph = {
            group.name.lower(): [
                x.group.lower()
                for x in _flatten_group(group)
                if isinstance(x, VAst.GroupName)
            ]
            for group in groups
        }
        sorter = TopologicalSorter(graph)
        return [group_map[name] for name in sorter.static_order()]

    class Lookup(ast.LookupBlock):
        def __init__(self, name, use_extension=False, location=None):
            super().__init__(name, use_extension, location)
            self.chained = []

    class VoltToFea:
        _NOT_LOOKUP_NAME_RE = re.compile(r"[^A-Za-z_0-9.]")
        _NOT_CLASS_NAME_RE = re.compile(r"[^A-Za-z_0-9.\-]")

        def __init__(self, file_or_path, font=None):
            if isinstance(file_or_path, VAst.VoltFile):
                self._doc, self._file_or_path = file_or_path, None
            else:
                self._doc, self._file_or_path = None, file_or_path
            self._font = font

            self._glyph_map = {}
            self._glyph_order = None

            self._gdef = {}
            self._glyphclasses = {}
            self._features = {}
            self._lookups = {}

            self._marks = set()
            self._ligatures = {}

            self._markclasses = {}
            self._anchors = {}

            self._settings = {}

            self._lookup_names = {}
            self._class_names = {}

        def _lookupName(self, name):
            if name not in self._lookup_names:
                res = self._NOT_LOOKUP_NAME_RE.sub("_", name)
                while res in self._lookup_names.values():
                    res += "_"
                self._lookup_names[name] = res
            return self._lookup_names[name]

        def _className(self, name):
            if name not in self._class_names:
                res = self._NOT_CLASS_NAME_RE.sub("_", name)
                while res in self._class_names.values():
                    res += "_"
                self._class_names[name] = res
            return self._class_names[name]

        def _collectStatements(self, doc, tables, ignore_unsupported_settings=False):
            # Collect glyph difinitions first, as we need them to map VOLT glyph names to font glyph name.
            for statement in doc.statements:
                if isinstance(statement, VAst.GlyphDefinition):
                    self._glyphDefinition(statement)

            # Collect and sort group definitions first, to make sure a group
            # definition that references other groups comes after them since VOLT
            # does not enforce such ordering, and feature file require it.
            groups = [s for s in doc.statements if isinstance(s, VAst.GroupDefinition)]
            for group in sort_groups(groups):
                self._groupDefinition(group)

            for statement in doc.statements:
                if isinstance(statement, VAst.AnchorDefinition):
                    if "GPOS" in tables:
                        self._anchorDefinition(statement)
                elif isinstance(statement, VAst.SettingDefinition):
                    self._settingDefinition(statement, ignore_unsupported_settings)
                elif isinstance(statement, (VAst.GlyphDefinition, VAst.GroupDefinition)):
                    pass  # Handled above
                elif isinstance(statement, VAst.ScriptDefinition):
                    self._scriptDefinition(statement)
                elif not isinstance(statement, VAst.LookupDefinition):
                    raise NotImplementedError(statement)

            # Lookup definitions need to be handled last as they reference glyph
            # and mark classes that might be defined after them.
            for statement in doc.statements:
                if isinstance(statement, VAst.LookupDefinition):
                    if statement.pos and "GPOS" not in tables:
                        continue
                    if statement.sub and "GSUB" not in tables:
                        continue
                    self._lookupDefinition(statement)

        def _buildFeatureFile(self, tables):
            doc = ast.FeatureFile()
            statements = doc.statements

            if self._glyphclasses:
                statements.append(ast.Comment("# Glyph classes"))
                statements.extend(self._glyphclasses.values())

            if self._markclasses:
                statements.append(ast.Comment("\n# Mark classes"))
                statements.extend(c[1] for c in sorted(self._markclasses.items()))

            if self._lookups:
                statements.append(ast.Comment("\n# Lookups"))
                for lookup in self._lookups.values():
                    statements.extend(lookup.chained)
                    statements.append(lookup)

            # Prune features
            features = self._features.copy()
            for feature_tag in features:
                scripts = features[feature_tag]
                for script_tag in scripts:
                    langs = scripts[script_tag]
                    for language_tag in langs:
                        langs[language_tag] = [
                            l for l in langs[language_tag] if l.lower() in self._lookups
                        ]
                    scripts[script_tag] = {t: l for t, l in langs.items() if l}
                features[feature_tag] = {t: s for t, s in scripts.items() if s}
            features = {t: f for t, f in features.items() if f}

            if features:
                statements.append(ast.Comment("# Features"))
                for feature_tag, scripts in features.items():
                    feature = ast.FeatureBlock(feature_tag)
                    script_tags = sorted(scripts, key=lambda k: 0 if k == "DFLT" else 1)
                    if feature_tag == "aalt" and len(script_tags) > 1:
                        log.warning(
                            "FEA syntax does not allow script statements in 'aalt' feature, "
                            "so only lookups from the first script will be included."
                        )
                        script_tags = script_tags[:1]
                    for script_tag in script_tags:
                        if feature_tag != "aalt":
                            feature.statements.append(ast.ScriptStatement(script_tag))
                        language_tags = sorted(
                            scripts[script_tag],
                            key=lambda k: 0 if k == "dflt" else 1,
                        )
                        if feature_tag == "aalt" and len(language_tags) > 1:
                            log.warning(
                                "FEA syntax does not allow language statements in 'aalt' feature, "
                                "so only lookups from the first language will be included."
                            )
                            language_tags = language_tags[:1]
                        for language_tag in language_tags:
                            if feature_tag != "aalt":
                                include_default = True if language_tag == "dflt" else False
                                feature.statements.append(
                                    ast.LanguageStatement(
                                        language_tag.ljust(4),
                                        include_default=include_default,
                                    )
                                )
                            for name in scripts[script_tag][language_tag]:
                                lookup = self._lookups[name.lower()]
                                lookupref = ast.LookupReferenceStatement(lookup)
                                feature.statements.append(lookupref)
                    statements.append(feature)

            if self._gdef and "GDEF" in tables:
                classes = []
                for name in ("BASE", "MARK", "LIGATURE", "COMPONENT"):
                    if name in self._gdef:
                        classname = "GDEF_" + name.lower()
                        glyphclass = ast.GlyphClassDefinition(classname, self._gdef[name])
                        statements.append(glyphclass)
                        classes.append(ast.GlyphClassName(glyphclass))
                    else:
                        classes.append(None)

                gdef = ast.TableBlock("GDEF")
                gdef.statements.append(ast.GlyphClassDefStatement(*classes))
                statements.append(gdef)

            return doc

        def convert(self, tables=None, ignore_unsupported_settings=False):
            if self._doc is None:
                self._doc = VoltParser(self._file_or_path).parse()
            doc = self._doc

            if tables is None:
                tables = TABLES
            if self._font is not None:
                self._glyph_order = self._font.getGlyphOrder()

            self._collectStatements(doc, tables, ignore_unsupported_settings)
            fea = self._buildFeatureFile(tables)
            return fea.asFea()

        def _glyphName(self, glyph):
            try:
                name = glyph.glyph
            except AttributeError:
                name = glyph
            return ast.GlyphName(self._glyph_map.get(name, name))

        def _groupName(self, group):
            try:
                name = group.group
            except AttributeError:
                name = group
            return ast.GlyphClassName(self._glyphclasses[name.lower()])

        def _glyphSet(self, item):
            return [
                (self._glyphName(x) if isinstance(x, (str, VAst.GlyphName)) else x)
                for x in item.glyphSet()
            ]

        def _coverage(self, coverage, flatten=False):
            items = []
            for item in coverage:
                if isinstance(item, VAst.GlyphName):
                    items.append(self._glyphName(item))
                elif isinstance(item, VAst.GroupName):
                    items.append(self._groupName(item))
                elif isinstance(item, VAst.Enum):
                    item = self._coverage(item.enum, flatten=True)
                    if flatten:
                        items.extend(item)
                    else:
                        items.append(ast.GlyphClass(item))
                elif isinstance(item, VAst.Range):
                    item = self._glyphSet(item)
                    if flatten:
                        items.extend(item)
                    else:
                        items.append(ast.GlyphClass(item))
                else:
                    raise NotImplementedError(item)
            return items

        def _context(self, context):
            out = []
            for item in context:
                coverage = self._coverage(item, flatten=True)
                if len(coverage) > 1:
                    coverage = ast.GlyphClass(coverage)
                else:
                    coverage = coverage[0]
                out.append(coverage)
            return out

        def _groupDefinition(self, group):
            name = self._className(group.name)
            glyphs = self._coverage(group.enum.enum, flatten=True)
            glyphclass = ast.GlyphClass(glyphs)
            classdef = ast.GlyphClassDefinition(name, glyphclass)
            self._glyphclasses[group.name.lower()] = classdef

        def _glyphDefinition(self, glyph):
            try:
                self._glyph_map[glyph.name] = self._glyph_order[glyph.id]
            except TypeError:
                pass

            if glyph.type in ("BASE", "MARK", "LIGATURE", "COMPONENT"):
                if glyph.type not in self._gdef:
                    self._gdef[glyph.type] = ast.GlyphClass()
                self._gdef[glyph.type].glyphs.append(self._glyphName(glyph.name))

            if glyph.type == "MARK":
                self._marks.add(glyph.name)
            elif glyph.type == "LIGATURE":
                self._ligatures[glyph.name] = glyph.components

        def _scriptDefinition(self, script):
            stag = script.tag
            for lang in script.langs:
                ltag = lang.tag
                for feature in lang.features:
                    lookups = {l.split("\\")[0]: True for l in feature.lookups}
                    ftag = feature.tag
                    if ftag not in self._features:
                        self._features[ftag] = {}
                    if stag not in self._features[ftag]:
                        self._features[ftag][stag] = {}
                    assert ltag not in self._features[ftag][stag]
                    self._features[ftag][stag][ltag] = lookups.keys()

        def _settingDefinition(self, setting, ignore_unsupported=False):
            if setting.name.startswith("COMPILER_"):
                self._settings[setting.name] = setting.value
            elif not ignore_unsupported:
                log.warning(f"Unsupported setting ignored: {setting.name}")

        def _adjustment(self, adjustment):
            adv, dx, dy, adv_adjust_by, dx_adjust_by, dy_adjust_by = adjustment

            adv_device = adv_adjust_by and adv_adjust_by.items() or None
            dx_device = dx_adjust_by and dx_adjust_by.items() or None
            dy_device = dy_adjust_by and dy_adjust_by.items() or None

            return ast.ValueRecord(
                xPlacement=dx,
                yPlacement=dy,
                xAdvance=adv,
                xPlaDevice=dx_device,
                yPlaDevice=dy_device,
                xAdvDevice=adv_device,
            )

        def _anchor(self, adjustment):
            adv, dx, dy, adv_adjust_by, dx_adjust_by, dy_adjust_by = adjustment

            assert not adv_adjust_by
            dx_device = dx_adjust_by and dx_adjust_by.items() or None
            dy_device = dy_adjust_by and dy_adjust_by.items() or None

            return ast.Anchor(
                dx or 0,
                dy or 0,
                xDeviceTable=dx_device or None,
                yDeviceTable=dy_device or None,
            )

        def _anchorDefinition(self, anchordef):
            anchorname = anchordef.name
            glyphname = anchordef.glyph_name
            anchor = self._anchor(anchordef.pos)

            if glyphname not in self._anchors:
                self._anchors[glyphname] = {}
            if anchorname.startswith("MARK_"):
                anchorname = anchorname[:5] + anchorname[5:].lower()
            else:
                anchorname = anchorname.lower()
            if anchorname not in self._anchors[glyphname]:
                self._anchors[glyphname][anchorname] = {}
            self._anchors[glyphname][anchorname][anchordef.component] = anchor

        def _gposLookup(self, lookup, fealookup):
            statements = fealookup.statements

            pos = lookup.pos
            if isinstance(pos, VAst.PositionAdjustPairDefinition):
                for (idx1, idx2), (pos1, pos2) in pos.adjust_pair.items():
                    coverage_1 = pos.coverages_1[idx1 - 1]
                    coverage_2 = pos.coverages_2[idx2 - 1]

                    # If not both are groups, use “enum pos” otherwise makeotf will
                    # fail.
                    enumerated = False
                    for item in coverage_1 + coverage_2:
                        if not isinstance(item, VAst.GroupName):
                            enumerated = True

                    glyphs1 = self._coverage(coverage_1)
                    glyphs2 = self._coverage(coverage_2)
                    record1 = self._adjustment(pos1)
                    record2 = self._adjustment(pos2)
                    assert len(glyphs1) == 1
                    assert len(glyphs2) == 1
                    statements.append(
                        ast.PairPosStatement(
                            glyphs1[0], record1, glyphs2[0], record2, enumerated=enumerated
                        )
                    )
            elif isinstance(pos, VAst.PositionAdjustSingleDefinition):
                for a, b in pos.adjust_single:
                    glyphs = self._coverage(a)
                    record = self._adjustment(b)
                    assert len(glyphs) == 1
                    statements.append(
                        ast.SinglePosStatement([(glyphs[0], record)], [], [], False)
                    )
            elif isinstance(pos, VAst.PositionAttachDefinition):
                anchors = {}
                allmarks = set()
                for coverage, anchorname in pos.coverage_to:
                    # In feature files mark classes are global, but in VOLT they
                    # are defined per-lookup. If we output mark class definitions
                    # for all marks that use a given anchor, we might end up with a
                    # mark used in two different classes in the same lookup, which
                    # is causes feature file compilation error.
                    # At the expense of uglier feature code, we make the mark class
                    # name by appending the current lookup name not the anchor
                    # name, and output mark class definitions only for marks used
                    # in this lookup.
                    classname = self._className(f"{anchorname}.{lookup.name}")
                    markclass = ast.MarkClass(classname)

                    # Anchor names are case-insensitive in VOLT
                    anchorname = anchorname.lower()

                    # We might still end in marks used in two different anchor
                    # classes, so we filter out already used marks.
                    marks = set()
                    for mark in coverage:
                        marks.update(mark.glyphSet())
                    if not marks.isdisjoint(allmarks):
                        marks.difference_update(allmarks)
                        if not marks:
                            continue
                    allmarks.update(marks)

                    for glyphname in marks:
                        glyph = self._glyphName(glyphname)
                        anchor = self._anchors[glyphname][f"MARK_{anchorname}"][1]
                        markdef = ast.MarkClassDefinition(markclass, anchor, glyph)
                        self._markclasses[(glyphname, classname)] = markdef

                    for base in pos.coverage:
                        for name in base.glyphSet():
                            if name not in anchors:
                                anchors[name] = []
                            if (anchorname, classname) not in anchors[name]:
                                anchors[name].append((anchorname, classname))

                is_ligature = all(n in self._ligatures for n in anchors)
                is_mark = all(n in self._marks for n in anchors)
                for name in anchors:
                    components = 1
                    if is_ligature:
                        components = self._ligatures[name]

                    marks = [[] for _ in range(components)]
                    for mark, classname in anchors[name]:
                        markclass = ast.MarkClass(classname)
                        for component in range(1, components + 1):
                            if component in self._anchors[name][mark]:
                                anchor = self._anchors[name][mark][component]
                                marks[component - 1].append((anchor, markclass))

                    base = self._glyphName(name)
                    if is_mark:
                        mark = ast.MarkMarkPosStatement(base, marks[0])
                    elif is_ligature:
                        mark = ast.MarkLigPosStatement(base, marks)
                    else:
                        mark = ast.MarkBasePosStatement(base, marks[0])
                    statements.append(mark)
            elif isinstance(pos, VAst.PositionAttachCursiveDefinition):
                # Collect enter and exit glyphs
                enter_coverage = []
                for coverage in pos.coverages_enter:
                    for base in coverage:
                        for name in base.glyphSet():
                            enter_coverage.append(name)
                exit_coverage = []
                for coverage in pos.coverages_exit:
                    for base in coverage:
                        for name in base.glyphSet():
                            exit_coverage.append(name)

                # Write enter anchors, also check if the glyph has exit anchor and
                # write it, too.
                for name in enter_coverage:
                    glyph = self._glyphName(name)
                    entry = self._anchors[name]["entry"][1]
                    exit = None
                    if name in exit_coverage:
                        exit = self._anchors[name]["exit"][1]
                        exit_coverage.pop(exit_coverage.index(name))
                    statements.append(ast.CursivePosStatement(glyph, entry, exit))

                # Write any remaining exit anchors.
                for name in exit_coverage:
                    glyph = self._glyphName(name)
                    exit = self._anchors[name]["exit"][1]
                    statements.append(ast.CursivePosStatement(glyph, None, exit))
            else:
                raise NotImplementedError(pos)

        def _gposContextLookup(self, lookup, prefix, suffix, ignore, fealookup, chained):
            statements = fealookup.statements

            pos = lookup.pos
            if isinstance(pos, VAst.PositionAdjustPairDefinition):
                for (idx1, idx2), (pos1, pos2) in pos.adjust_pair.items():
                    glyphs1 = self._coverage(pos.coverages_1[idx1 - 1])
                    glyphs2 = self._coverage(pos.coverages_2[idx2 - 1])
                    assert len(glyphs1) == 1
                    assert len(glyphs2) == 1
                    glyphs = (glyphs1[0], glyphs2[0])

                    if ignore:
                        statement = ast.IgnorePosStatement([(prefix, glyphs, suffix)])
                    else:
                        statement = ast.ChainContextPosStatement(
                            prefix, glyphs, suffix, [chained, chained]
                        )
                    statements.append(statement)
            elif isinstance(pos, VAst.PositionAdjustSingleDefinition):
                glyphs = [ast.GlyphClass()]
                for a, _ in pos.adjust_single:
                    glyphs[0].extend(self._coverage(a, flatten=True))

                if ignore:
                    statement = ast.IgnorePosStatement([(prefix, glyphs, suffix)])
                else:
                    statement = ast.ChainContextPosStatement(
                        prefix, glyphs, suffix, [chained]
                    )
                statements.append(statement)
            elif isinstance(pos, VAst.PositionAttachDefinition):
                glyphs = [ast.GlyphClass()]
                for coverage, _ in pos.coverage_to:
                    glyphs[0].extend(self._coverage(coverage, flatten=True))

                if ignore:
                    statement = ast.IgnorePosStatement([(prefix, glyphs, suffix)])
                else:
                    statement = ast.ChainContextPosStatement(
                        prefix, glyphs, suffix, [chained]
                    )
                statements.append(statement)
            else:
                raise NotImplementedError(pos)

        def _gsubLookup(self, lookup, fealookup):
            statements = fealookup.statements

            sub = lookup.sub

            # Alternate substitutions are represented by adding multiple
            # substitutions for the same glyph, so we need to collect them into one
            # to many mapping.
            if isinstance(sub, VAst.SubstitutionAlternateDefinition):
                alternates = {}
                for key, val in sub.mapping.items():
                    if not key or not val:
                        path, line, column = sub.location
                        log.warning(f"{path}:{line}:{column}: Ignoring empty substitution")
                        continue
                    glyphs = self._coverage(key)
                    replacements = self._coverage(val)
                    assert len(glyphs) == 1
                    for src_glyph, repl_glyph in zip(
                        glyphs[0].glyphSet(), replacements[0].glyphSet()
                    ):
                        alternates.setdefault(str(self._glyphName(src_glyph)), []).append(
                            str(self._glyphName(repl_glyph))
                        )

                for glyph, replacements in alternates.items():
                    statement = ast.AlternateSubstStatement(
                        [], glyph, [], ast.GlyphClass(replacements)
                    )
                    statements.append(statement)
                return

            for key, val in sub.mapping.items():
                if not key or not val:
                    path, line, column = sub.location
                    log.warning(f"{path}:{line}:{column}: Ignoring empty substitution")
                    continue
                glyphs = self._coverage(key)
                replacements = self._coverage(val)
                if isinstance(sub, VAst.SubstitutionSingleDefinition):
                    assert len(glyphs) == 1
                    assert len(replacements) == 1
                    statements.append(
                        ast.SingleSubstStatement(glyphs, replacements, [], [], False)
                    )
                elif isinstance(sub, VAst.SubstitutionReverseChainingSingleDefinition):
                    # This is handled in gsubContextLookup()
                    pass
                elif isinstance(sub, VAst.SubstitutionMultipleDefinition):
                    assert len(glyphs) == 1
                    statements.append(
                        ast.MultipleSubstStatement([], glyphs[0], [], replacements)
                    )
                elif isinstance(sub, VAst.SubstitutionLigatureDefinition):
                    assert len(replacements) == 1
                    statement = ast.LigatureSubstStatement(
                        [], glyphs, [], replacements[0], False
                    )

                    # If any of the input glyphs is a group, we need to
                    # explode the substitution into multiple ligature substitutions
                    # since feature file syntax does not support classes in
                    # ligature substitutions.
                    n = max(len(x.glyphSet()) for x in glyphs)
                    if n > 1:
                        # All input should either be groups of the same length or single glyphs
                        assert all(len(x.glyphSet()) in (n, 1) for x in glyphs)
                        glyphs = [x.glyphSet() for x in glyphs]
                        glyphs = [([x[0]] * n if len(x) == 1 else x) for x in glyphs]

                        # In this case ligature replacements must be a group of the same length
                        # as the input groups, or a single glyph. VOLT
                        # allows the replacement glyphs to be longer and truncates them.
                        # So well allow that and zip() below will do the truncation
                        # for us.
                        replacement = replacements[0].glyphSet()
                        if len(replacement) == 1:
                            replacement = [replacement[0]] * n
                        assert len(replacement) >= n

                        # Add the unexploded statement commented out for reference.
                        statements.append(ast.Comment(f"# {statement}"))

                        for zipped in zip(*glyphs, replacement):
                            zipped = [self._glyphName(x) for x in zipped]
                            statements.append(
                                ast.LigatureSubstStatement(
                                    [], zipped[:-1], [], zipped[-1], False
                                )
                            )
                    else:
                        statements.append(statement)
                else:
                    raise NotImplementedError(sub)

        def _gsubContextLookup(self, lookup, prefix, suffix, ignore, fealookup, chained):
            statements = fealookup.statements

            sub = lookup.sub

            if isinstance(sub, VAst.SubstitutionReverseChainingSingleDefinition):
                # Reverse substitutions is a special case, it can’t use chained lookups.
                for key, val in sub.mapping.items():
                    if not key or not val:
                        path, line, column = sub.location
                        log.warning(f"{path}:{line}:{column}: Ignoring empty substitution")
                        continue
                    glyphs = self._coverage(key)
                    replacements = self._coverage(val)
                    statements.append(
                        ast.ReverseChainSingleSubstStatement(
                            prefix, suffix, glyphs, replacements
                        )
                    )
                fealookup.chained = []
                return

            if not isinstance(
                sub,
                (
                    VAst.SubstitutionSingleDefinition,
                    VAst.SubstitutionMultipleDefinition,
                    VAst.SubstitutionLigatureDefinition,
                    VAst.SubstitutionAlternateDefinition,
                ),
            ):
                raise NotImplementedError(type(sub))

            glyphs = []
            for key, val in sub.mapping.items():
                if not key or not val:
                    path, line, column = sub.location
                    log.warning(f"{path}:{line}:{column}: Ignoring empty substitution")
                    continue
                glyphs.extend(self._coverage(key, flatten=True))

            if len(glyphs) > 1:
                glyphs = [ast.GlyphClass(glyphs)]
            if ignore:
                statements.append(ast.IgnoreSubstStatement([(prefix, glyphs, suffix)]))
            else:
                statements.append(
                    ast.ChainContextSubstStatement(prefix, glyphs, suffix, [chained])
                )

        def _lookupDefinition(self, lookup):
            mark_attachement = None
            mark_filtering = None

            flags = 0
            if lookup.direction == "RTL":
                flags |= 1
            if not lookup.process_base:
                flags |= 2
            # FIXME: Does VOLT support this?
            # if not lookup.process_ligatures:
            #     flags |= 4
            if not lookup.process_marks:
                flags |= 8
            elif isinstance(lookup.process_marks, str):
                mark_attachement = self._groupName(lookup.process_marks)
            elif lookup.mark_glyph_set is not None:
                mark_filtering = self._groupName(lookup.mark_glyph_set)

            lookupflags = None
            if flags or mark_attachement is not None or mark_filtering is not None:
                lookupflags = ast.LookupFlagStatement(
                    flags, mark_attachement, mark_filtering
                )

            use_extension = False
            if self._settings.get("COMPILER_USEEXTENSIONLOOKUPS"):
                use_extension = True

            if "\\" in lookup.name:
                # Merge sub lookups as subtables (lookups named “base\sub”),
                # makeotf/feaLib will issue a warning and ignore the subtable
                # statement if it is not a pairpos lookup, though.
                name = lookup.name.split("\\")[0]
                if name.lower() not in self._lookups:
                    fealookup = Lookup(
                        self._lookupName(name),
                        use_extension=use_extension,
                    )
                    if lookupflags is not None:
                        fealookup.statements.append(lookupflags)
                    fealookup.statements.append(ast.Comment("# " + lookup.name))
                else:
                    fealookup = self._lookups[name.lower()]
                    fealookup.statements.append(ast.SubtableStatement())
                    fealookup.statements.append(ast.Comment("# " + lookup.name))
                self._lookups[name.lower()] = fealookup
            else:
                fealookup = Lookup(
                    self._lookupName(lookup.name),
                    use_extension=use_extension,
                )
                if lookupflags is not None:
                    fealookup.statements.append(lookupflags)
                self._lookups[lookup.name.lower()] = fealookup

            if lookup.comments is not None:
                fealookup.statements.append(ast.Comment("# " + lookup.comments))

            contexts = []
            for context in lookup.context:
                prefix = self._context(context.left)
                suffix = self._context(context.right)
                ignore = context.ex_or_in == "EXCEPT_CONTEXT"
                contexts.append([prefix, suffix, ignore])
                # It seems that VOLT will create contextual substitution using
                # only the input if there is no other contexts in this lookup.
                if ignore and len(lookup.context) == 1:
                    contexts.append([[], [], False])

            if contexts:
                chained = ast.LookupBlock(
                    self._lookupName(lookup.name + " chained"),
                    use_extension=use_extension,
                )
                fealookup.chained.append(chained)
                if lookup.sub is not None:
                    self._gsubLookup(lookup, chained)
                elif lookup.pos is not None:
                    self._gposLookup(lookup, chained)
                for prefix, suffix, ignore in contexts:
                    if lookup.sub is not None:
                        self._gsubContextLookup(
                            lookup, prefix, suffix, ignore, fealookup, chained
                        )
                    elif lookup.pos is not None:
                        self._gposContextLookup(
                            lookup, prefix, suffix, ignore, fealookup, chained
                        )
            else:
                if lookup.sub is not None:
                    self._gsubLookup(lookup, fealookup)
                elif lookup.pos is not None:
                    self._gposLookup(lookup, fealookup)

    def main(args=None):
        """Convert MS VOLT to AFDKO feature files."""

        import argparse
        from pathlib import Path

        from fontTools import configLogger

        parser = argparse.ArgumentParser(
            "fonttools voltLib.voltToFea", description=main.__doc__
        )
        parser.add_argument(
            "input", metavar="INPUT", type=Path, help="input font/VTP file to process"
        )
        parser.add_argument(
            "featurefile", metavar="OUTPUT", type=Path, help="output feature file"
        )
        parser.add_argument(
            "-t",
            "--table",
            action="append",
            choices=TABLES,
            dest="tables",
            help="List of tables to write, by default all tables are written",
        )
        parser.add_argument(
            "-q", "--quiet", action="store_true", help="Suppress non-error messages"
        )
        parser.add_argument(
            "--traceback", action="store_true", help="Don’t catch exceptions"
        )

        options = parser.parse_args(args)

        configLogger(level=("ERROR" if options.quiet else "INFO"))

        file_or_path = options.input
        font = None
        try:
            font = TTFont(file_or_path)
            if "TSIV" in font:
                file_or_path = StringIO(font["TSIV"].data.decode("utf-8"))
            else:
                log.error('"TSIV" table is missing, font was not saved from VOLT?')
                return 1
        except TTLibError:
            pass

        converter = VoltToFea(file_or_path, font)
        try:
            fea = converter.convert(options.tables)
        except NotImplementedError as e:
            if options.traceback:
                raise
            location = getattr(e.args[0], "location", None)
            message = f'"{e}" is not supported'
            if location:
                path, line, column = location
                log.error(f"{path}:{line}:{column}: {message}")
            else:
                log.error(message)
            return 1
        with open(options.featurefile, "w") as feafile:
            feafile.write(fea)

    if __name__ == "__main__":
        import sys

        sys.exit(main())