# Source code for fontTools.varLib.featureVars

    """Module to build FeatureVariation tables:
    https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#featurevariations-table

    NOTE: The API is experimental and subject to change.
    """
    from fontTools.misc.dictTools import hashdict
    from fontTools.misc.intTools import popCount
    from fontTools.ttLib import newTable
    from fontTools.ttLib.tables import otTables as ot
    from fontTools.otlLib.builder import buildLookup, buildSingleSubstSubtable
    from collections import OrderedDict

    from .errors import VarLibError, VarLibValidationError

    def addFeatureVariations(font, conditionalSubstitutions, featureTag='rvrn'):
        """Add conditional substitutions to a Variable Font.

        The `conditionalSubstitutions` argument is a list of (Region, Substitutions)
        tuples.

        A Region is a list of Boxes. A Box is a dict mapping axisTags to
        (minValue, maxValue) tuples. Irrelevant axes may be omitted and they are
        interpretted as extending to end of axis in each direction.  A Box represents
        an orthogonal 'rectangular' subset of an N-dimensional design space.
        A Region represents a more complex subset of an N-dimensional design space,
        ie. the union of all the Boxes in the Region.
        For efficiency, Boxes within a Region should ideally not overlap, but
        functionality is not compromised if they do.

        The minimum and maximum values are expressed in normalized coordinates.

        A Substitution is a dict mapping source glyph names to substitute glyph names.

        Example:

        # >>> f = TTFont(srcPath)
        # >>> condSubst = [
        # ...     # A list of (Region, Substitution) tuples.
        # ...     ([{"wdth": (0.5, 1.0)}], {"cent": "cent.rvrn"}),
        # ...     ([{"wght": (0.5, 1.0)}], {"dollar": "dollar.rvrn"}),
        # ... ]
        # >>> addFeatureVariations(f, condSubst)
        # >>> f.save(dstPath)
        """

        _checkSubstitutionGlyphsExist(
            glyphNames=set(font.getGlyphOrder()),
            substitutions=conditionalSubstitutions,
        )

        substitutions = overlayFeatureVariations(conditionalSubstitutions)

        # turn substitution dicts into tuples of tuples, so they are hashable
        conditionalSubstitutions, allSubstitutions = makeSubstitutionsHashable(substitutions)
        if "GSUB" not in font:
            font["GSUB"] = buildGSUB()

        # setup lookups
        lookupMap = buildSubstitutionLookups(font["GSUB"].table, allSubstitutions)

        # addFeatureVariationsRaw takes a list of
        #  ( {condition}, [ lookup indices ] )
        # so rearrange our lookups to match
        conditionsAndLookups = []
        for conditionSet, substitutions in conditionalSubstitutions:
            conditionsAndLookups.append((conditionSet, [lookupMap[s] for s in substitutions]))

        addFeatureVariationsRaw(font, font["GSUB"].table,
                                conditionsAndLookups,
                                featureTag)

    def _checkSubstitutionGlyphsExist(glyphNames, substitutions):
        referencedGlyphNames = set()
        for _, substitution in substitutions:
            referencedGlyphNames |=  substitution.keys()
            referencedGlyphNames |=  set(substitution.values())
        missing = referencedGlyphNames - glyphNames
        if missing:
           raise VarLibValidationError(
                "Missing glyphs are referenced in conditional substitution rules:"
                f" {', '.join(missing)}"
            )

    def overlayFeatureVariations(conditionalSubstitutions):
        """Compute overlaps between all conditional substitutions.

        The `conditionalSubstitutions` argument is a list of (Region, Substitutions)
        tuples.

        A Region is a list of Boxes. A Box is a dict mapping axisTags to
        (minValue, maxValue) tuples. Irrelevant axes may be omitted and they are
        interpretted as extending to end of axis in each direction.  A Box represents
        an orthogonal 'rectangular' subset of an N-dimensional design space.
        A Region represents a more complex subset of an N-dimensional design space,
        ie. the union of all the Boxes in the Region.
        For efficiency, Boxes within a Region should ideally not overlap, but
        functionality is not compromised if they do.

        The minimum and maximum values are expressed in normalized coordinates.

        A Substitution is a dict mapping source glyph names to substitute glyph names.

        Returns data is in similar but different format.  Overlaps of distinct
        substitution Boxes (*not* Regions) are explicitly listed as distinct rules,
        and rules with the same Box merged.  The more specific rules appear earlier
        in the resulting list.  Moreover, instead of just a dictionary of substitutions,
        a list of dictionaries is returned for substitutions corresponding to each
        unique space, with each dictionary being identical to one of the input
        substitution dictionaries.  These dictionaries are not merged to allow data
        sharing when they are converted into font tables.

        Example::

            >>> condSubst = [
            ...     # A list of (Region, Substitution) tuples.
            ...     ([{"wght": (0.5, 1.0)}], {"dollar": "dollar.rvrn"}),
            ...     ([{"wght": (0.5, 1.0)}], {"dollar": "dollar.rvrn"}),
            ...     ([{"wdth": (0.5, 1.0)}], {"cent": "cent.rvrn"}),
            ...     ([{"wght": (0.5, 1.0), "wdth": (-1, 1.0)}], {"dollar": "dollar.rvrn"}),
            ... ]
            >>> from pprint import pprint
            >>> pprint(overlayFeatureVariations(condSubst))
            [({'wdth': (0.5, 1.0), 'wght': (0.5, 1.0)},
              [{'dollar': 'dollar.rvrn'}, {'cent': 'cent.rvrn'}]),
             ({'wdth': (0.5, 1.0)}, [{'cent': 'cent.rvrn'}]),
             ({'wght': (0.5, 1.0)}, [{'dollar': 'dollar.rvrn'}])]

        """

        # Merge same-substitutions rules, as this creates fewer number oflookups.
        merged = OrderedDict()
        for value,key in conditionalSubstitutions:
            key = hashdict(key)
            if key in merged:
                merged[key].extend(value)
            else:
                merged[key] = value
        conditionalSubstitutions = [(v,dict(k)) for k,v in merged.items()]
        del merged

        # Merge same-region rules, as this is cheaper.
        # Also convert boxes to hashdict()
        #
        # Reversing is such that earlier entries win in case of conflicting substitution
        # rules for the same region.
        merged = OrderedDict()
        for key,value in reversed(conditionalSubstitutions):
            key = tuple(sorted((hashdict(cleanupBox(k)) for k in key),
                               key=lambda d: tuple(sorted(d.items()))))
            if key in merged:
                merged[key].update(value)
            else:
                merged[key] = dict(value)
        conditionalSubstitutions = list(reversed(merged.items()))
        del merged

        # Overlay
        #
        # Rank is the bit-set of the index of all contributing layers.
        initMapInit = ((hashdict(),0),) # Initializer representing the entire space
        boxMap = OrderedDict(initMapInit) # Map from Box to Rank
        for i,(currRegion,_) in enumerate(conditionalSubstitutions):
            newMap = OrderedDict(initMapInit)
            currRank = 1<<i
            for box,rank in boxMap.items():
                for currBox in currRegion:
                    intersection, remainder = overlayBox(currBox, box)
                    if intersection is not None:
                        intersection = hashdict(intersection)
                        newMap[intersection] = newMap.get(intersection, 0) | rank|currRank
                    if remainder is not None:
                        remainder = hashdict(remainder)
                        newMap[remainder] = newMap.get(remainder, 0) | rank
            boxMap = newMap

        # Generate output
        items = []
        for box,rank in sorted(boxMap.items(),
                               key=(lambda BoxAndRank: -popCount(BoxAndRank[1]))):
            # Skip any box that doesn't have any substitution.
            if rank == 0:
                continue
            substsList = []
            i = 0
            while rank:
              if rank & 1:
                  substsList.append(conditionalSubstitutions[i][1])
              rank >>= 1
              i += 1
            items.append((dict(box),substsList))
        return items

    #
    # Terminology:
    #
    # A 'Box' is a dict representing an orthogonal "rectangular" bit of N-dimensional space.
    # The keys in the dict are axis tags, the values are (minValue, maxValue) tuples.
    # Missing dimensions (keys) are substituted by the default min and max values
    # from the corresponding axes.
    #

    def overlayBox(top, bot):
        """Overlays ``top`` box on top of ``bot`` box.

        Returns two items:

        * Box for intersection of ``top`` and ``bot``, or None if they don't intersect.
        * Box for remainder of ``bot``.  Remainder box might not be exact (since the
          remainder might not be a simple box), but is inclusive of the exact
          remainder.
        """

        # Intersection
        intersection = {}
        intersection.update(top)
        intersection.update(bot)
        for axisTag in set(top) & set(bot):
            min1, max1 = top[axisTag]
            min2, max2 = bot[axisTag]
            minimum = max(min1, min2)
            maximum = min(max1, max2)
            if not minimum < maximum:
                return None, bot # Do not intersect
            intersection[axisTag] = minimum,maximum

        # Remainder
        #
        # Remainder is empty if bot's each axis range lies within that of intersection.
        #
        # Remainder is shrank if bot's each, except for exactly one, axis range lies
        # within that of intersection, and that one axis, it spills out of the
        # intersection only on one side.
        #
        # Bot is returned in full as remainder otherwise, as true remainder is not
        # representable as a single box.

        remainder = dict(bot)
        exactlyOne = False
        fullyInside = False
        for axisTag in bot:
            if axisTag not in intersection:
                fullyInside = False
                continue # Axis range lies fully within
            min1, max1 = intersection[axisTag]
            min2, max2 = bot[axisTag]
            if min1 <= min2 and max2 <= max1:
                continue # Axis range lies fully within

            # Bot's range doesn't fully lie within that of top's for this axis.
            # We know they intersect, so it cannot lie fully without either; so they
            # overlap.

            # If we have had an overlapping axis before, remainder is not
            # representable as a box, so return full bottom and go home.
            if exactlyOne:
                return intersection, bot
            exactlyOne = True
            fullyInside = False

            # Otherwise, cut remainder on this axis and continue.
            if min1 <= min2:
                # Right side survives.
                minimum = max(max1, min2)
                maximum = max2
            elif max2 <= max1:
                # Left side survives.
                minimum = min2
                maximum = min(min1, max2)
            else:
                # Remainder leaks out from both sides.  Can't cut either.
                return intersection, bot

            remainder[axisTag] = minimum,maximum

        if fullyInside:
            # bot is fully within intersection.  Remainder is empty.
            return intersection, None

        return intersection, remainder

    def cleanupBox(box):
        """Return a sparse copy of `box`, without redundant (default) values.

            >>> cleanupBox({})
            {}
            >>> cleanupBox({'wdth': (0.0, 1.0)})
            {'wdth': (0.0, 1.0)}
            >>> cleanupBox({'wdth': (-1.0, 1.0)})
            {}

        """
        return {tag: limit for tag, limit in box.items() if limit != (-1.0, 1.0)}

    #
    # Low level implementation
    #

    def addFeatureVariationsRaw(font, table, conditionalSubstitutions, featureTag='rvrn'):
        """Low level implementation of addFeatureVariations that directly
        models the possibilities of the FeatureVariations table."""

        #
        # if there is no <featureTag> feature:
        #     make empty <featureTag> feature
        #     sort features, get <featureTag> feature index
        #     add <featureTag> feature to all scripts
        # make lookups
        # add feature variations
        #
        if table.Version < 0x00010001:
            table.Version = 0x00010001  # allow table.FeatureVariations

        table.FeatureVariations = None  # delete any existing FeatureVariations

        varFeatureIndices = []
        for index, feature in enumerate(table.FeatureList.FeatureRecord):
            if feature.FeatureTag == featureTag:
                varFeatureIndices.append(index)

        if not varFeatureIndices:
            varFeature = buildFeatureRecord(featureTag, [])
            table.FeatureList.FeatureRecord.append(varFeature)
            table.FeatureList.FeatureCount = len(table.FeatureList.FeatureRecord)

            sortFeatureList(table)
            varFeatureIndex = table.FeatureList.FeatureRecord.index(varFeature)

            for scriptRecord in table.ScriptList.ScriptRecord:
                if scriptRecord.Script.DefaultLangSys is None:
                    raise VarLibError(
                        "Feature variations require that the script "
                        f"'{scriptRecord.ScriptTag}' defines a default language system."
                    )
                langSystems = [lsr.LangSys for lsr in scriptRecord.Script.LangSysRecord]
                for langSys in [scriptRecord.Script.DefaultLangSys] + langSystems:
                    langSys.FeatureIndex.append(varFeatureIndex)

            varFeatureIndices = [varFeatureIndex]

        axisIndices = {axis.axisTag: axisIndex for axisIndex, axis in enumerate(font["fvar"].axes)}

        featureVariationRecords = []
        for conditionSet, lookupIndices in conditionalSubstitutions:
            conditionTable = []
            for axisTag, (minValue, maxValue) in sorted(conditionSet.items()):
                if minValue > maxValue:
                    raise VarLibValidationError(
                        "A condition set has a minimum value above the maximum value."
                    )
                ct = buildConditionTable(axisIndices[axisTag], minValue, maxValue)
                conditionTable.append(ct)
            records = []
            for varFeatureIndex in varFeatureIndices:
                existingLookupIndices = table.FeatureList.FeatureRecord[varFeatureIndex].Feature.LookupListIndex
                records.append(buildFeatureTableSubstitutionRecord(varFeatureIndex, existingLookupIndices + lookupIndices))
            featureVariationRecords.append(buildFeatureVariationRecord(conditionTable, records))

        table.FeatureVariations = buildFeatureVariations(featureVariationRecords)

    #
    # Building GSUB/FeatureVariations internals
    #

    def buildGSUB():
        """Build a GSUB table from scratch."""
        fontTable = newTable("GSUB")
        gsub = fontTable.table = ot.GSUB()
        gsub.Version = 0x00010001  # allow gsub.FeatureVariations

        gsub.ScriptList = ot.ScriptList()
        gsub.ScriptList.ScriptRecord = []
        gsub.FeatureList = ot.FeatureList()
        gsub.FeatureList.FeatureRecord = []
        gsub.LookupList = ot.LookupList()
        gsub.LookupList.Lookup = []

        srec = ot.ScriptRecord()
        srec.ScriptTag = 'DFLT'
        srec.Script = ot.Script()
        srec.Script.DefaultLangSys = None
        srec.Script.LangSysRecord = []

        langrec = ot.LangSysRecord()
        langrec.LangSys = ot.LangSys()
        langrec.LangSys.ReqFeatureIndex = 0xFFFF
        langrec.LangSys.FeatureIndex = []
        srec.Script.DefaultLangSys = langrec.LangSys

        gsub.ScriptList.ScriptRecord.append(srec)
        gsub.ScriptList.ScriptCount = 1
        gsub.FeatureVariations = None

        return fontTable

    def makeSubstitutionsHashable(conditionalSubstitutions):
        """Turn all the substitution dictionaries in sorted tuples of tuples so
        they are hashable, to detect duplicates so we don't write out redundant
        data."""
        allSubstitutions = set()
        condSubst = []
        for conditionSet, substitutionMaps in conditionalSubstitutions:
            substitutions = []
            for substitutionMap in substitutionMaps:
                subst = tuple(sorted(substitutionMap.items()))
                substitutions.append(subst)
                allSubstitutions.add(subst)
            condSubst.append((conditionSet, substitutions))
        return condSubst, sorted(allSubstitutions)

    def buildSubstitutionLookups(gsub, allSubstitutions):
        """Build the lookups for the glyph substitutions, return a dict mapping
        the substitution to lookup indices."""
        firstIndex = len(gsub.LookupList.Lookup)
        lookupMap = {}
        for i, substitutionMap in enumerate(allSubstitutions):
            lookupMap[substitutionMap] = i + firstIndex

        for subst in allSubstitutions:
            substMap = dict(subst)
            lookup = buildLookup([buildSingleSubstSubtable(substMap)])
            gsub.LookupList.Lookup.append(lookup)
            assert gsub.LookupList.Lookup[lookupMap[subst]] is lookup
        gsub.LookupList.LookupCount = len(gsub.LookupList.Lookup)
        return lookupMap

    def buildFeatureVariations(featureVariationRecords):
        """Build the FeatureVariations subtable."""
        fv = ot.FeatureVariations()
        fv.Version = 0x00010000
        fv.FeatureVariationRecord = featureVariationRecords
        fv.FeatureVariationCount = len(featureVariationRecords)
        return fv

    def buildFeatureRecord(featureTag, lookupListIndices):
        """Build a FeatureRecord."""
        fr = ot.FeatureRecord()
        fr.FeatureTag = featureTag
        fr.Feature = ot.Feature()
        fr.Feature.LookupListIndex = lookupListIndices
        fr.Feature.populateDefaults()
        return fr

    def buildFeatureVariationRecord(conditionTable, substitutionRecords):
        """Build a FeatureVariationRecord."""
        fvr = ot.FeatureVariationRecord()
        fvr.ConditionSet = ot.ConditionSet()
        fvr.ConditionSet.ConditionTable = conditionTable
        fvr.ConditionSet.ConditionCount = len(conditionTable)
        fvr.FeatureTableSubstitution = ot.FeatureTableSubstitution()
        fvr.FeatureTableSubstitution.Version = 0x00010000
        fvr.FeatureTableSubstitution.SubstitutionRecord = substitutionRecords
        fvr.FeatureTableSubstitution.SubstitutionCount = len(substitutionRecords)
        return fvr

    def buildFeatureTableSubstitutionRecord(featureIndex, lookupListIndices):
        """Build a FeatureTableSubstitutionRecord."""
        ftsr = ot.FeatureTableSubstitutionRecord()
        ftsr.FeatureIndex = featureIndex
        ftsr.Feature = ot.Feature()
        ftsr.Feature.LookupListIndex = lookupListIndices
        ftsr.Feature.LookupCount = len(lookupListIndices)
        return ftsr

    def buildConditionTable(axisIndex, filterRangeMinValue, filterRangeMaxValue):
        """Build a ConditionTable."""
        ct = ot.ConditionTable()
        ct.Format = 1
        ct.AxisIndex = axisIndex
        ct.FilterRangeMinValue = filterRangeMinValue
        ct.FilterRangeMaxValue = filterRangeMaxValue
        return ct

    def sortFeatureList(table):
        """Sort the feature list by feature tag, and remap the feature indices
        elsewhere. This is needed after the feature list has been modified.
        """
        # decorate, sort, undecorate, because we need to make an index remapping table
        tagIndexFea = [(fea.FeatureTag, index, fea) for index, fea in enumerate(table.FeatureList.FeatureRecord)]
        tagIndexFea.sort()
        table.FeatureList.FeatureRecord = [fea for tag, index, fea in tagIndexFea]
        featureRemap = dict(zip([index for tag, index, fea in tagIndexFea], range(len(tagIndexFea))))

        # Remap the feature indices
        remapFeatures(table, featureRemap)

    def remapFeatures(table, featureRemap):
        """Go through the scripts list, and remap feature indices."""
        for scriptIndex, script in enumerate(table.ScriptList.ScriptRecord):
            defaultLangSys = script.Script.DefaultLangSys
            if defaultLangSys is not None:
                _remapLangSys(defaultLangSys, featureRemap)
            for langSysRecordIndex, langSysRec in enumerate(script.Script.LangSysRecord):
                langSys = langSysRec.LangSys
                _remapLangSys(langSys, featureRemap)

        if hasattr(table, "FeatureVariations") and table.FeatureVariations is not None:
            for fvr in table.FeatureVariations.FeatureVariationRecord:
                for ftsr in fvr.FeatureTableSubstitution.SubstitutionRecord:
                    ftsr.FeatureIndex = featureRemap[ftsr.FeatureIndex]

    def _remapLangSys(langSys, featureRemap):
        if langSys.ReqFeatureIndex != 0xffff:
            langSys.ReqFeatureIndex = featureRemap[langSys.ReqFeatureIndex]
        langSys.FeatureIndex = [featureRemap[index] for index in langSys.FeatureIndex]

    if __name__ == "__main__":
        import doctest, sys
        sys.exit(doctest.testmod().failed)