# coding: utf-8
"""fontTools.ttLib.tables.otTables -- A collection of classes representing the various
OpenType subtables.

Most are constructed upon import from data in otData.py, all are populated with
converter objects from otConverters.py.
"""
from enum import IntEnum
import itertools
from collections import namedtuple
from fontTools.misc.py23 import *
from fontTools.misc.fixedTools import otRound
from fontTools.misc.textTools import pad, safeEval
from .otBase import BaseTable, FormatSwitchingBaseTable, ValueRecord, CountReference
from fontTools.feaLib.lookupDebugInfo import LookupDebugInfo, LOOKUP_DEBUG_INFO_KEY
import logging
import struct


log = logging.getLogger(__name__)


class AATStateTable(object):
	def __init__(self):
		self.GlyphClasses = {}  # GlyphID --> GlyphClass
		self.States = []  # List of AATState, indexed by state number
		self.PerGlyphLookups = []  # [{GlyphID:GlyphID}, ...]


class AATState(object):
	def __init__(self):
		self.Transitions = {}  # GlyphClass --> AATAction


class AATAction(object):
	_FLAGS = None

	@staticmethod
	def compileActions(font, states):
		return (None, None)

	def _writeFlagsToXML(self, xmlWriter):
		flags = [f for f in self._FLAGS if self.__dict__[f]]
		if flags:
			xmlWriter.simpletag("Flags", value=",".join(flags))
			xmlWriter.newline()
		if self.ReservedFlags != 0:
			xmlWriter.simpletag(
				"ReservedFlags",
				value='0x%04X' % self.ReservedFlags)
			xmlWriter.newline()

	def _setFlag(self, flag):
		assert flag in self._FLAGS, "unsupported flag %s" % flag
		self.__dict__[flag] = True


class RearrangementMorphAction(AATAction):
	staticSize = 4
	actionHeaderSize = 0
	_FLAGS = ["MarkFirst", "DontAdvance", "MarkLast"]

	_VERBS = {
		0: "no change",
		1: "Ax ⇒ xA",
		2: "xD ⇒ Dx",
		3: "AxD ⇒ DxA",
		4: "ABx ⇒ xAB",
		5: "ABx ⇒ xBA",
		6: "xCD ⇒ CDx",
		7: "xCD ⇒ DCx",
		8: "AxCD ⇒ CDxA",
		9: "AxCD ⇒ DCxA",
		10: "ABxD ⇒ DxAB",
		11: "ABxD ⇒ DxBA",
		12: "ABxCD ⇒ CDxAB",
		13: "ABxCD ⇒ CDxBA",
		14: "ABxCD ⇒ DCxAB",
		15: "ABxCD ⇒ DCxBA",
        }

	def __init__(self):
		self.NewState = 0
		self.Verb = 0
		self.MarkFirst = False
		self.DontAdvance = False
		self.MarkLast = False
		self.ReservedFlags = 0

	def compile(self, writer, font, actionIndex):
		assert actionIndex is None
		writer.writeUShort(self.NewState)
		assert self.Verb >= 0 and self.Verb <= 15, self.Verb
		flags = self.Verb | self.ReservedFlags
		if self.MarkFirst: flags |= 0x8000
		if self.DontAdvance: flags |= 0x4000
		if self.MarkLast: flags |= 0x2000
		writer.writeUShort(flags)

	def decompile(self, reader, font, actionReader):
		assert actionReader is None
		self.NewState = reader.readUShort()
		flags = reader.readUShort()
		self.Verb = flags & 0xF
		self.MarkFirst = bool(flags & 0x8000)
		self.DontAdvance = bool(flags & 0x4000)
		self.MarkLast = bool(flags & 0x2000)
		self.ReservedFlags = flags & 0x1FF0

	def toXML(self, xmlWriter, font, attrs, name):
		xmlWriter.begintag(name, **attrs)
		xmlWriter.newline()
		xmlWriter.simpletag("NewState", value=self.NewState)
		xmlWriter.newline()
		self._writeFlagsToXML(xmlWriter)
		xmlWriter.simpletag("Verb", value=self.Verb)
		verbComment = self._VERBS.get(self.Verb)
		if verbComment is not None:
			xmlWriter.comment(verbComment)
		xmlWriter.newline()
		xmlWriter.endtag(name)
		xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
		self.NewState = self.Verb = self.ReservedFlags = 0
		self.MarkFirst = self.DontAdvance = self.MarkLast = False
		content = [t for t in content if isinstance(t, tuple)]
		for eltName, eltAttrs, eltContent in content:
			if eltName == "NewState":
				self.NewState = safeEval(eltAttrs["value"])
			elif eltName == "Verb":
				self.Verb = safeEval(eltAttrs["value"])
			elif eltName == "ReservedFlags":
				self.ReservedFlags = safeEval(eltAttrs["value"])
			elif eltName == "Flags":
				for flag in eltAttrs["value"].split(","):
					self._setFlag(flag.strip())


class ContextualMorphAction(AATAction):
	staticSize = 8
	actionHeaderSize = 0
	_FLAGS = ["SetMark", "DontAdvance"]

	def __init__(self):
		self.NewState = 0
		self.SetMark, self.DontAdvance = False, False
		self.ReservedFlags = 0
		self.MarkIndex, self.CurrentIndex = 0xFFFF, 0xFFFF

	def compile(self, writer, font, actionIndex):
		assert actionIndex is None
		writer.writeUShort(self.NewState)
		flags = self.ReservedFlags
		if self.SetMark: flags |= 0x8000
		if self.DontAdvance: flags |= 0x4000
		writer.writeUShort(flags)
		writer.writeUShort(self.MarkIndex)
		writer.writeUShort(self.CurrentIndex)

	def decompile(self, reader, font, actionReader):
		assert actionReader is None
		self.NewState = reader.readUShort()
		flags = reader.readUShort()
		self.SetMark = bool(flags & 0x8000)
		self.DontAdvance = bool(flags & 0x4000)
		self.ReservedFlags = flags & 0x3FFF
		self.MarkIndex = reader.readUShort()
		self.CurrentIndex = reader.readUShort()

	def toXML(self, xmlWriter, font, attrs, name):
		xmlWriter.begintag(name, **attrs)
		xmlWriter.newline()
		xmlWriter.simpletag("NewState", value=self.NewState)
		xmlWriter.newline()
		self._writeFlagsToXML(xmlWriter)
		xmlWriter.simpletag("MarkIndex", value=self.MarkIndex)
		xmlWriter.newline()
		xmlWriter.simpletag("CurrentIndex",
		                    value=self.CurrentIndex)
		xmlWriter.newline()
		xmlWriter.endtag(name)
		xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
		self.NewState = self.ReservedFlags = 0
		self.SetMark = self.DontAdvance = False
		self.MarkIndex, self.CurrentIndex = 0xFFFF, 0xFFFF
		content = [t for t in content if isinstance(t, tuple)]
		for eltName, eltAttrs, eltContent in content:
			if eltName == "NewState":
				self.NewState = safeEval(eltAttrs["value"])
			elif eltName == "Flags":
				for flag in eltAttrs["value"].split(","):
					self._setFlag(flag.strip())
			elif eltName == "ReservedFlags":
				self.ReservedFlags = safeEval(eltAttrs["value"])
			elif eltName == "MarkIndex":
				self.MarkIndex = safeEval(eltAttrs["value"])
			elif eltName == "CurrentIndex":
				self.CurrentIndex = safeEval(eltAttrs["value"])


class LigAction(object):
	def __init__(self):
		self.Store = False
		# GlyphIndexDelta is a (possibly negative) delta that gets
		# added to the glyph ID at the top of the AAT runtime
		# execution stack. It is *not* a byte offset into the
		# morx table. The result of the addition, which is performed
		# at run time by the shaping engine, is an index into
		# the ligature components table. See 'morx' specification.
		# In the AAT specification, this field is called Offset;
		# but its meaning is quite different from other offsets
		# in either AAT or OpenType, so we use a different name.
		self.GlyphIndexDelta = 0


class LigatureMorphAction(AATAction):
	staticSize = 6

	# 4 bytes for each of {action,ligComponents,ligatures}Offset
	actionHeaderSize = 12

	_FLAGS = ["SetComponent", "DontAdvance"]

	def __init__(self):
		self.NewState = 0
		self.SetComponent, self.DontAdvance = False, False
		self.ReservedFlags = 0
		self.Actions = []

	def compile(self, writer, font, actionIndex):
		assert actionIndex is not None
		writer.writeUShort(self.NewState)
		flags = self.ReservedFlags
		if self.SetComponent: flags |= 0x8000
		if self.DontAdvance: flags |= 0x4000
		if len(self.Actions) > 0: flags |= 0x2000
		writer.writeUShort(flags)
		if len(self.Actions) > 0:
			actions = self.compileLigActions()
			writer.writeUShort(actionIndex[actions])
		else:
			writer.writeUShort(0)

	def decompile(self, reader, font, actionReader):
		assert actionReader is not None
		self.NewState = reader.readUShort()
		flags = reader.readUShort()
		self.SetComponent = bool(flags & 0x8000)
		self.DontAdvance = bool(flags & 0x4000)
		performAction = bool(flags & 0x2000)
		# As of 2017-09-12, the 'morx' specification says that
		# the reserved bitmask in ligature subtables is 0x3FFF.
		# However, the specification also defines a flag 0x2000,
		# so the reserved value should actually be 0x1FFF.
		# TODO: Report this specification bug to Apple.
		self.ReservedFlags = flags & 0x1FFF
		actionIndex = reader.readUShort()
		if performAction:
			self.Actions = self._decompileLigActions(
				actionReader, actionIndex)
		else:
			self.Actions = []

	@staticmethod
	def compileActions(font, states):
		result, actions, actionIndex = b"", set(), {}
		for state in states:
			for _glyphClass, trans in state.Transitions.items():
				actions.add(trans.compileLigActions())
		# Sort the compiled actions in decreasing order of
		# length, so that the longer sequence come before the
		# shorter ones.  For each compiled action ABCD, its
		# suffixes BCD, CD, and D do not be encoded separately
		# (in case they occur); instead, we can just store an
		# index that points into the middle of the longer
		# sequence. Every compiled AAT ligature sequence is
		# terminated with an end-of-sequence flag, which can
		# only be set on the last element of the sequence.
		# Therefore, it is sufficient to consider just the
		# suffixes.
		for a in sorted(actions, key=lambda x:(-len(x), x)):
			if a not in actionIndex:
				for i in range(0, len(a), 4):
					suffix = a[i:]
					suffixIndex = (len(result) + i) // 4
					actionIndex.setdefault(
						suffix, suffixIndex)
				result += a
		result = pad(result, 4)
		return (result, actionIndex)

	def compileLigActions(self):
		result = []
		for i, action in enumerate(self.Actions):
			last = (i == len(self.Actions) - 1)
			value = action.GlyphIndexDelta & 0x3FFFFFFF
			value |= 0x80000000 if last else 0
			value |= 0x40000000 if action.Store else 0
			result.append(struct.pack(">L", value))
		return bytesjoin(result)

	def _decompileLigActions(self, actionReader, actionIndex):
		actions = []
		last = False
		reader = actionReader.getSubReader(
			actionReader.pos + actionIndex * 4)
		while not last:
			value = reader.readULong()
			last = bool(value & 0x80000000)
			action = LigAction()
			actions.append(action)
			action.Store = bool(value & 0x40000000)
			delta = value & 0x3FFFFFFF
			if delta >= 0x20000000: # sign-extend 30-bit value
				delta = -0x40000000 + delta
			action.GlyphIndexDelta = delta
		return actions

	def fromXML(self, name, attrs, content, font):
		self.NewState = self.ReservedFlags = 0
		self.SetComponent = self.DontAdvance = False
		self.ReservedFlags = 0
		self.Actions = []
		content = [t for t in content if isinstance(t, tuple)]
		for eltName, eltAttrs, eltContent in content:
			if eltName == "NewState":
				self.NewState = safeEval(eltAttrs["value"])
			elif eltName == "Flags":
				for flag in eltAttrs["value"].split(","):
					self._setFlag(flag.strip())
			elif eltName == "ReservedFlags":
				self.ReservedFlags = safeEval(eltAttrs["value"])
			elif eltName == "Action":
				action = LigAction()
				flags = eltAttrs.get("Flags", "").split(",")
				flags = [f.strip() for f in flags]
				action.Store = "Store" in flags
				action.GlyphIndexDelta = safeEval(
					eltAttrs["GlyphIndexDelta"])
				self.Actions.append(action)

	def toXML(self, xmlWriter, font, attrs, name):
		xmlWriter.begintag(name, **attrs)
		xmlWriter.newline()
		xmlWriter.simpletag("NewState", value=self.NewState)
		xmlWriter.newline()
		self._writeFlagsToXML(xmlWriter)
		for action in self.Actions:
			attribs = [("GlyphIndexDelta", action.GlyphIndexDelta)]
			if action.Store:
				attribs.append(("Flags", "Store"))
			xmlWriter.simpletag("Action", attribs)
			xmlWriter.newline()
		xmlWriter.endtag(name)
		xmlWriter.newline()


class InsertionMorphAction(AATAction):
	staticSize = 8
	actionHeaderSize = 4  # 4 bytes for actionOffset
	_FLAGS = ["SetMark", "DontAdvance",
	          "CurrentIsKashidaLike", "MarkedIsKashidaLike",
	          "CurrentInsertBefore", "MarkedInsertBefore"]

	def __init__(self):
		self.NewState = 0
		for flag in self._FLAGS:
			setattr(self, flag, False)
		self.ReservedFlags = 0
		self.CurrentInsertionAction, self.MarkedInsertionAction = [], []

	def compile(self, writer, font, actionIndex):
		assert actionIndex is not None
		writer.writeUShort(self.NewState)
		flags = self.ReservedFlags
		if self.SetMark: flags |= 0x8000
		if self.DontAdvance: flags |= 0x4000
		if self.CurrentIsKashidaLike: flags |= 0x2000
		if self.MarkedIsKashidaLike: flags |= 0x1000
		if self.CurrentInsertBefore: flags |= 0x0800
		if self.MarkedInsertBefore: flags |= 0x0400
		flags |= len(self.CurrentInsertionAction) << 5
		flags |= len(self.MarkedInsertionAction)
		writer.writeUShort(flags)
		if len(self.CurrentInsertionAction) > 0:
			currentIndex = actionIndex[
				tuple(self.CurrentInsertionAction)]
		else:
			currentIndex = 0xFFFF
		writer.writeUShort(currentIndex)
		if len(self.MarkedInsertionAction) > 0:
			markedIndex = actionIndex[
				tuple(self.MarkedInsertionAction)]
		else:
			markedIndex = 0xFFFF
		writer.writeUShort(markedIndex)

	def decompile(self, reader, font, actionReader):
		assert actionReader is not None
		self.NewState = reader.readUShort()
		flags = reader.readUShort()
		self.SetMark = bool(flags & 0x8000)
		self.DontAdvance = bool(flags & 0x4000)
		self.CurrentIsKashidaLike = bool(flags & 0x2000)
		self.MarkedIsKashidaLike = bool(flags & 0x1000)
		self.CurrentInsertBefore = bool(flags & 0x0800)
		self.MarkedInsertBefore = bool(flags & 0x0400)
		self.CurrentInsertionAction = self._decompileInsertionAction(
			actionReader, font,
			index=reader.readUShort(),
			count=((flags & 0x03E0) >> 5))
		self.MarkedInsertionAction = self._decompileInsertionAction(
			actionReader, font,
			index=reader.readUShort(),
			count=(flags & 0x001F))

	def _decompileInsertionAction(self, actionReader, font, index, count):
		if index == 0xFFFF or count == 0:
			return []
		reader = actionReader.getSubReader(
			actionReader.pos + index * 2)
		return [font.getGlyphName(glyphID)
		        for glyphID in reader.readUShortArray(count)]

	def toXML(self, xmlWriter, font, attrs, name):
		xmlWriter.begintag(name, **attrs)
		xmlWriter.newline()
		xmlWriter.simpletag("NewState", value=self.NewState)
		xmlWriter.newline()
		self._writeFlagsToXML(xmlWriter)
		for g in self.CurrentInsertionAction:
			xmlWriter.simpletag("CurrentInsertionAction", glyph=g)
			xmlWriter.newline()
		for g in self.MarkedInsertionAction:
			xmlWriter.simpletag("MarkedInsertionAction", glyph=g)
			xmlWriter.newline()
		xmlWriter.endtag(name)
		xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
		self.__init__()
		content = [t for t in content if isinstance(t, tuple)]
		for eltName, eltAttrs, eltContent in content:
			if eltName == "NewState":
				self.NewState = safeEval(eltAttrs["value"])
			elif eltName == "Flags":
				for flag in eltAttrs["value"].split(","):
					self._setFlag(flag.strip())
			elif eltName == "CurrentInsertionAction":
				self.CurrentInsertionAction.append(
					eltAttrs["glyph"])
			elif eltName == "MarkedInsertionAction":
				self.MarkedInsertionAction.append(
					eltAttrs["glyph"])
			else:
				assert False, eltName

	@staticmethod
	def compileActions(font, states):
		actions, actionIndex, result = set(), {}, b""
		for state in states:
			for _glyphClass, trans in state.Transitions.items():
				if trans.CurrentInsertionAction is not None:
					actions.add(tuple(trans.CurrentInsertionAction))
				if trans.MarkedInsertionAction is not None:
					actions.add(tuple(trans.MarkedInsertionAction))
		# Sort the compiled actions in decreasing order of
		# length, so that the longer sequence come before the
		# shorter ones.
		for action in sorted(actions, key=lambda x:(-len(x), x)):
			# We insert all sub-sequences of the action glyph sequence
			# into actionIndex. For example, if one action triggers on
			# glyph sequence [A, B, C, D, E] and another action triggers
			# on [C, D], we return result=[A, B, C, D, E] (as list of
			# encoded glyph IDs), and actionIndex={('A','B','C','D','E'): 0,
			# ('C','D'): 2}.
			if action in actionIndex:
				continue
			for start in range(0, len(action)):
				startIndex = (len(result) // 2) + start
				for limit in range(start, len(action)):
					glyphs = action[start : limit + 1]
					actionIndex.setdefault(glyphs, startIndex)
			for glyph in action:
				glyphID = font.getGlyphID(glyph)
				result += struct.pack(">H", glyphID)
		return result, actionIndex


class FeatureParams(BaseTable):

	def compile(self, writer, font):
		assert featureParamTypes.get(writer['FeatureTag']) == self.__class__, "Wrong FeatureParams type for feature '%s': %s" % (writer['FeatureTag'], self.__class__.__name__)
		BaseTable.compile(self, writer, font)

	def toXML(self, xmlWriter, font, attrs=None, name=None):
		BaseTable.toXML(self, xmlWriter, font, attrs, name=self.__class__.__name__)

class FeatureParamsSize(FeatureParams):
	pass

class FeatureParamsStylisticSet(FeatureParams):
	pass

class FeatureParamsCharacterVariants(FeatureParams):
	pass

class Coverage(FormatSwitchingBaseTable):

	# manual implementation to get rid of glyphID dependencies

	def populateDefaults(self, propagator=None):
		if not hasattr(self, 'glyphs'):
			self.glyphs = []

	def postRead(self, rawTable, font):
		if self.Format == 1:
			# TODO only allow glyphs that are valid?
			self.glyphs = rawTable["GlyphArray"]
		elif self.Format == 2:
			glyphs = self.glyphs = []
			ranges = rawTable["RangeRecord"]
			glyphOrder = font.getGlyphOrder()
			# Some SIL fonts have coverage entries that don't have sorted
			# StartCoverageIndex.  If it is so, fixup and warn.  We undo
			# this when writing font out.
			sorted_ranges = sorted(ranges, key=lambda a: a.StartCoverageIndex)
			if ranges != sorted_ranges:
				log.warning("GSUB/GPOS Coverage is not sorted by glyph ids.")
				ranges = sorted_ranges
			del sorted_ranges
			for r in ranges:
				assert r.StartCoverageIndex == len(glyphs), \
					(r.StartCoverageIndex, len(glyphs))
				start = r.Start
				end = r.End
				try:
					startID = font.getGlyphID(start, requireReal=True)
				except KeyError:
					log.warning("Coverage table has start glyph ID out of range: %s.", start)
					continue
				try:
					endID = font.getGlyphID(end, requireReal=True) + 1
				except KeyError:
					# Apparently some tools use 65535 to "match all" the range
					if end != 'glyph65535':
						log.warning("Coverage table has end glyph ID out of range: %s.", end)
					# NOTE: We clobber out-of-range things here.  There are legit uses for those,
					# but none that we have seen in the wild.
					endID = len(glyphOrder)
				glyphs.extend(glyphOrder[glyphID] for glyphID in range(startID, endID))
		else:
			self.glyphs = []
			log.warning("Unknown Coverage format: %s", self.Format)

	def preWrite(self, font):
		glyphs = getattr(self, "glyphs", None)
		if glyphs is None:
			glyphs = self.glyphs = []
		format = 1
		rawTable = {"GlyphArray": glyphs}
		getGlyphID = font.getGlyphID
		if glyphs:
			# find out whether Format 2 is more compact or not
			glyphIDs = [getGlyphID(glyphName) for glyphName in glyphs ]
			brokenOrder = sorted(glyphIDs) != glyphIDs

			last = glyphIDs[0]
			ranges = [[last]]
			for glyphID in glyphIDs[1:]:
				if glyphID != last + 1:
					ranges[-1].append(last)
					ranges.append([glyphID])
				last = glyphID
			ranges[-1].append(last)

			if brokenOrder or len(ranges) * 3 < len(glyphs):  # 3 words vs. 1 word
				# Format 2 is more compact
				index = 0
				for i in range(len(ranges)):
					start, end = ranges[i]
					r = RangeRecord()
					r.StartID = start
					r.Start = font.getGlyphName(start)
					r.End = font.getGlyphName(end)
					r.StartCoverageIndex = index
					ranges[i] = r
					index = index + end - start + 1
				if brokenOrder:
					log.warning("GSUB/GPOS Coverage is not sorted by glyph ids.")
					ranges.sort(key=lambda a: a.StartID)
				for r in ranges:
					del r.StartID
				format = 2
				rawTable = {"RangeRecord": ranges}
			#else:
			#	fallthrough; Format 1 is more compact
		self.Format = format
		return rawTable

	def toXML2(self, xmlWriter, font):
		for glyphName in getattr(self, "glyphs", []):
			xmlWriter.simpletag("Glyph", value=glyphName)
			xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
		glyphs = getattr(self, "glyphs", None)
		if glyphs is None:
			glyphs = []
			self.glyphs = glyphs
		glyphs.append(attrs["value"])


class VarIdxMap(BaseTable):

	def populateDefaults(self, propagator=None):
		if not hasattr(self, 'mapping'):
			self.mapping = {}

	def postRead(self, rawTable, font):
		assert (rawTable['EntryFormat'] & 0xFFC0) == 0
		glyphOrder = font.getGlyphOrder()
		mapList = rawTable['mapping']
		mapList.extend([mapList[-1]] * (len(glyphOrder) - len(mapList)))
		self.mapping = dict(zip(glyphOrder, mapList))

	def preWrite(self, font):
		mapping = getattr(self, "mapping", None)
		if mapping is None:
			mapping = self.mapping = {}

		glyphOrder = font.getGlyphOrder()
		mapping = [mapping[g] for g in glyphOrder]
		while len(mapping) > 1 and mapping[-2] == mapping[-1]:
			del mapping[-1]

		rawTable = { 'mapping': mapping }
		rawTable['MappingCount'] = len(mapping)

		ored = 0
		for idx in mapping:
			ored |= idx

		inner = ored & 0xFFFF
		innerBits = 0
		while inner:
			innerBits += 1
			inner >>= 1
		innerBits = max(innerBits, 1)
		assert innerBits <= 16

		ored = (ored >> (16-innerBits)) | (ored & ((1<<innerBits)-1))
		if   ored <= 0x000000FF:
			entrySize = 1
		elif ored <= 0x0000FFFF:
			entrySize = 2
		elif ored <= 0x00FFFFFF:
			entrySize = 3
		else:
			entrySize = 4

		entryFormat = ((entrySize - 1) << 4) | (innerBits - 1)

		rawTable['EntryFormat'] = entryFormat
		return rawTable

	def toXML2(self, xmlWriter, font):
		for glyph, value in sorted(getattr(self, "mapping", {}).items()):
			attrs = (
				('glyph', glyph),
				('outer', value >> 16),
				('inner', value & 0xFFFF),
			)
			xmlWriter.simpletag("Map", attrs)
			xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
		mapping = getattr(self, "mapping", None)
		if mapping is None:
			mapping = {}
			self.mapping = mapping
		try:
			glyph = attrs['glyph']
		except: # https://github.com/fonttools/fonttools/commit/21cbab8ce9ded3356fef3745122da64dcaf314e9#commitcomment-27649836
			glyph = font.getGlyphOrder()[attrs['index']]
		outer = safeEval(attrs['outer'])
		inner = safeEval(attrs['inner'])
		assert inner <= 0xFFFF
		mapping[glyph] = (outer << 16) | inner


class VarRegionList(BaseTable):

	def preWrite(self, font):
		# The OT spec says VarStore.VarRegionList.RegionAxisCount should always
		# be equal to the fvar.axisCount, and OTS < v8.0.0 enforces this rule
		# even when the VarRegionList is empty. We can't treat RegionAxisCount
		# like a normal propagated count (== len(Region[i].VarRegionAxis)),
		# otherwise it would default to 0 if VarRegionList is empty.
		# Thus, we force it to always be equal to fvar.axisCount.
		# https://github.com/khaledhosny/ots/pull/192
		fvarTable = font.get("fvar")
		if fvarTable:
			self.RegionAxisCount = len(fvarTable.axes)
		return {
			**self.__dict__,
			"RegionAxisCount": CountReference(self.__dict__, "RegionAxisCount")
		}


class SingleSubst(FormatSwitchingBaseTable):

	def populateDefaults(self, propagator=None):
		if not hasattr(self, 'mapping'):
			self.mapping = {}

	def postRead(self, rawTable, font):
		mapping = {}
		input = _getGlyphsFromCoverageTable(rawTable["Coverage"])
		if self.Format == 1:
			delta = rawTable["DeltaGlyphID"]
			inputGIDS =  [ font.getGlyphID(name) for name in input ]
			outGIDS = [ (glyphID + delta) % 65536 for glyphID in inputGIDS ]
			outNames = [ font.getGlyphName(glyphID) for glyphID in outGIDS ]
			for inp, out in zip(input, outNames):
				mapping[inp] = out
		elif self.Format == 2:
			assert len(input) == rawTable["GlyphCount"], \
					"invalid SingleSubstFormat2 table"
			subst = rawTable["Substitute"]
			for inp, sub in zip(input, subst):
				mapping[inp] = sub
		else:
			assert 0, "unknown format: %s" % self.Format
		self.mapping = mapping

	def preWrite(self, font):
		mapping = getattr(self, "mapping", None)
		if mapping is None:
			mapping = self.mapping = {}
		items = list(mapping.items())
		getGlyphID = font.getGlyphID
		gidItems = [(getGlyphID(a), getGlyphID(b)) for a,b in items]
		sortableItems = sorted(zip(gidItems, items))

		# figure out format
		format = 2
		delta = None
		for inID, outID in gidItems:
			if delta is None:
				delta = (outID - inID) % 65536

			if (inID + delta) % 65536 != outID:
					break
		else:
			if delta is None:
				# the mapping is empty, better use format 2
				format = 2
			else:
				format = 1

		rawTable = {}
		self.Format = format
		cov = Coverage()
		input =  [ item [1][0] for item in sortableItems]
		subst =  [ item [1][1] for item in sortableItems]
		cov.glyphs = input
		rawTable["Coverage"] = cov
		if format == 1:
			assert delta is not None
			rawTable["DeltaGlyphID"] = delta
		else:
			rawTable["Substitute"] = subst
		return rawTable

	def toXML2(self, xmlWriter, font):
		items = sorted(self.mapping.items())
		for inGlyph, outGlyph in items:
			xmlWriter.simpletag("Substitution",
					[("in", inGlyph), ("out", outGlyph)])
			xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
		mapping = getattr(self, "mapping", None)
		if mapping is None:
			mapping = {}
			self.mapping = mapping
		mapping[attrs["in"]] = attrs["out"]


class MultipleSubst(FormatSwitchingBaseTable):

	def populateDefaults(self, propagator=None):
		if not hasattr(self, 'mapping'):
			self.mapping = {}

	def postRead(self, rawTable, font):
		mapping = {}
		if self.Format == 1:
			glyphs = _getGlyphsFromCoverageTable(rawTable["Coverage"])
			subst = [s.Substitute for s in rawTable["Sequence"]]
			mapping = dict(zip(glyphs, subst))
		else:
			assert 0, "unknown format: %s" % self.Format
		self.mapping = mapping

	def preWrite(self, font):
		mapping = getattr(self, "mapping", None)
		if mapping is None:
			mapping = self.mapping = {}
		cov = Coverage()
		cov.glyphs = sorted(list(mapping.keys()), key=font.getGlyphID)
		self.Format = 1
		rawTable = {
                        "Coverage": cov,
                        "Sequence": [self.makeSequence_(mapping[glyph])
                                     for glyph in cov.glyphs],
                }
		return rawTable

	def toXML2(self, xmlWriter, font):
		items = sorted(self.mapping.items())
		for inGlyph, outGlyphs in items:
			out = ",".join(outGlyphs)
			xmlWriter.simpletag("Substitution",
					[("in", inGlyph), ("out", out)])
			xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
		mapping = getattr(self, "mapping", None)
		if mapping is None:
			mapping = {}
			self.mapping = mapping

		# TTX v3.0 and earlier.
		if name == "Coverage":
			self.old_coverage_ = []
			for element in content:
				if not isinstance(element, tuple):
					continue
				element_name, element_attrs, _ = element
				if element_name == "Glyph":
					self.old_coverage_.append(element_attrs["value"])
			return
		if name == "Sequence":
			index = int(attrs.get("index", len(mapping)))
			glyph = self.old_coverage_[index]
			glyph_mapping = mapping[glyph] = []
			for element in content:
				if not isinstance(element, tuple):
					continue
				element_name, element_attrs, _ = element
				if element_name == "Substitute":
					glyph_mapping.append(element_attrs["value"])
			return

                # TTX v3.1 and later.
		outGlyphs = attrs["out"].split(",") if attrs["out"] else []
		mapping[attrs["in"]] = [g.strip() for g in outGlyphs]

	@staticmethod
	def makeSequence_(g):
		seq = Sequence()
		seq.Substitute = g
		return seq


class ClassDef(FormatSwitchingBaseTable):

	def populateDefaults(self, propagator=None):
		if not hasattr(self, 'classDefs'):
			self.classDefs = {}

	def postRead(self, rawTable, font):
		classDefs = {}
		glyphOrder = font.getGlyphOrder()

		if self.Format == 1:
			start = rawTable["StartGlyph"]
			classList = rawTable["ClassValueArray"]
			try:
				startID = font.getGlyphID(start, requireReal=True)
			except KeyError:
				log.warning("ClassDef table has start glyph ID out of range: %s.", start)
				startID = len(glyphOrder)
			endID = startID + len(classList)
			if endID > len(glyphOrder):
				log.warning("ClassDef table has entries for out of range glyph IDs: %s,%s.",
					start, len(classList))
				# NOTE: We clobber out-of-range things here.  There are legit uses for those,
				# but none that we have seen in the wild.
				endID = len(glyphOrder)

			for glyphID, cls in zip(range(startID, endID), classList):
				if cls:
					classDefs[glyphOrder[glyphID]] = cls

		elif self.Format == 2:
			records = rawTable["ClassRangeRecord"]
			for rec in records:
				start = rec.Start
				end = rec.End
				cls = rec.Class
				try:
					startID = font.getGlyphID(start, requireReal=True)
				except KeyError:
					log.warning("ClassDef table has start glyph ID out of range: %s.", start)
					continue
				try:
					endID = font.getGlyphID(end, requireReal=True) + 1
				except KeyError:
					# Apparently some tools use 65535 to "match all" the range
					if end != 'glyph65535':
						log.warning("ClassDef table has end glyph ID out of range: %s.", end)
					# NOTE: We clobber out-of-range things here.  There are legit uses for those,
					# but none that we have seen in the wild.
					endID = len(glyphOrder)
				for glyphID in range(startID, endID):
					if cls:
						classDefs[glyphOrder[glyphID]] = cls
		else:
			log.warning("Unknown ClassDef format: %s", self.Format)
		self.classDefs = classDefs

	def _getClassRanges(self, font):
		classDefs = getattr(self, "classDefs", None)
		if classDefs is None:
			self.classDefs = {}
			return
		getGlyphID = font.getGlyphID
		items = []
		for glyphName, cls in classDefs.items():
			if not cls:
				continue
			items.append((getGlyphID(glyphName), glyphName, cls))
		if items:
			items.sort()
			last, lastName, lastCls = items[0]
			ranges = [[lastCls, last, lastName]]
			for glyphID, glyphName, cls in items[1:]:
				if glyphID != last + 1 or cls != lastCls:
					ranges[-1].extend([last, lastName])
					ranges.append([cls, glyphID, glyphName])
				last = glyphID
				lastName = glyphName
				lastCls = cls
			ranges[-1].extend([last, lastName])
			return ranges

	def preWrite(self, font):
		format = 2
		rawTable = {"ClassRangeRecord": []}
		ranges = self._getClassRanges(font)
		if ranges:
			startGlyph = ranges[0][1]
			endGlyph = ranges[-1][3]
			glyphCount = endGlyph - startGlyph + 1
			if len(ranges) * 3 < glyphCount + 1:
				# Format 2 is more compact
				for i in range(len(ranges)):
					cls, start, startName, end, endName = ranges[i]
					rec = ClassRangeRecord()
					rec.Start = startName
					rec.End = endName
					rec.Class = cls
					ranges[i] = rec
				format = 2
				rawTable = {"ClassRangeRecord": ranges}
			else:
				# Format 1 is more compact
				startGlyphName = ranges[0][2]
				classes = [0] * glyphCount
				for cls, start, startName, end, endName in ranges:
					for g in range(start - startGlyph, end - startGlyph + 1):
						classes[g] = cls
				format = 1
				rawTable = {"StartGlyph": startGlyphName, "ClassValueArray": classes}
		self.Format = format
		return rawTable

	def toXML2(self, xmlWriter, font):
		items = sorted(self.classDefs.items())
		for glyphName, cls in items:
			xmlWriter.simpletag("ClassDef", [("glyph", glyphName), ("class", cls)])
			xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
		classDefs = getattr(self, "classDefs", None)
		if classDefs is None:
			classDefs = {}
			self.classDefs = classDefs
		classDefs[attrs["glyph"]] = int(attrs["class"])


class AlternateSubst(FormatSwitchingBaseTable):

	def populateDefaults(self, propagator=None):
		if not hasattr(self, 'alternates'):
			self.alternates = {}

	def postRead(self, rawTable, font):
		alternates = {}
		if self.Format == 1:
			input = _getGlyphsFromCoverageTable(rawTable["Coverage"])
			alts = rawTable["AlternateSet"]
			assert len(input) == len(alts)
			for inp,alt in zip(input,alts):
				alternates[inp] = alt.Alternate
		else:
			assert 0, "unknown format: %s" % self.Format
		self.alternates = alternates

	def preWrite(self, font):
		self.Format = 1
		alternates = getattr(self, "alternates", None)
		if alternates is None:
			alternates = self.alternates = {}
		items = list(alternates.items())
		for i in range(len(items)):
			glyphName, set = items[i]
			items[i] = font.getGlyphID(glyphName), glyphName, set
		items.sort()
		cov = Coverage()
		cov.glyphs = [ item[1] for item in items]
		alternates = []
		setList = [ item[-1] for item in items]
		for set in setList:
			alts = AlternateSet()
			alts.Alternate = set
			alternates.append(alts)
		# a special case to deal with the fact that several hundred Adobe Japan1-5
		# CJK fonts will overflow an offset if the coverage table isn't pushed to the end.
		# Also useful in that when splitting a sub-table because of an offset overflow
		# I don't need to calculate the change in the subtable offset due to the change in the coverage table size.
		# Allows packing more rules in subtable.
		self.sortCoverageLast = 1
		return {"Coverage": cov, "AlternateSet": alternates}

	def toXML2(self, xmlWriter, font):
		items = sorted(self.alternates.items())
		for glyphName, alternates in items:
			xmlWriter.begintag("AlternateSet", glyph=glyphName)
			xmlWriter.newline()
			for alt in alternates:
				xmlWriter.simpletag("Alternate", glyph=alt)
				xmlWriter.newline()
			xmlWriter.endtag("AlternateSet")
			xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
		alternates = getattr(self, "alternates", None)
		if alternates is None:
			alternates = {}
			self.alternates = alternates
		glyphName = attrs["glyph"]
		set = []
		alternates[glyphName] = set
		for element in content:
			if not isinstance(element, tuple):
				continue
			name, attrs, content = element
			set.append(attrs["glyph"])


class LigatureSubst(FormatSwitchingBaseTable):

	def populateDefaults(self, propagator=None):
		if not hasattr(self, 'ligatures'):
			self.ligatures = {}

	def postRead(self, rawTable, font):
		ligatures = {}
		if self.Format == 1:
			input = _getGlyphsFromCoverageTable(rawTable["Coverage"])
			ligSets = rawTable["LigatureSet"]
			assert len(input) == len(ligSets)
			for i in range(len(input)):
				ligatures[input[i]] = ligSets[i].Ligature
		else:
			assert 0, "unknown format: %s" % self.Format
		self.ligatures = ligatures

	def preWrite(self, font):
		self.Format = 1
		ligatures = getattr(self, "ligatures", None)
		if ligatures is None:
			ligatures = self.ligatures = {}

		if ligatures and isinstance(next(iter(ligatures)), tuple):
			# New high-level API in v3.1 and later.  Note that we just support compiling this
			# for now.  We don't load to this API, and don't do XML with it.

			# ligatures is map from components-sequence to lig-glyph
			newLigatures = dict()
			for comps,lig in sorted(ligatures.items(), key=lambda item: (-len(item[0]), item[0])):
				ligature = Ligature()
				ligature.Component = comps[1:]
				ligature.CompCount = len(comps)
				ligature.LigGlyph = lig
				newLigatures.setdefault(comps[0], []).append(ligature)
			ligatures = newLigatures

		items = list(ligatures.items())
		for i in range(len(items)):
			glyphName, set = items[i]
			items[i] = font.getGlyphID(glyphName), glyphName, set
		items.sort()
		cov = Coverage()
		cov.glyphs = [ item[1] for item in items]

		ligSets = []
		setList = [ item[-1] for item in items ]
		for set in setList:
			ligSet = LigatureSet()
			ligs = ligSet.Ligature = []
			for lig in set:
				ligs.append(lig)
			ligSets.append(ligSet)
		# Useful in that when splitting a sub-table because of an offset overflow
		# I don't need to calculate the change in subtabl offset due to the coverage table size.
		# Allows packing more rules in subtable.
		self.sortCoverageLast = 1
		return {"Coverage": cov, "LigatureSet": ligSets}

	def toXML2(self, xmlWriter, font):
		items = sorted(self.ligatures.items())
		for glyphName, ligSets in items:
			xmlWriter.begintag("LigatureSet", glyph=glyphName)
			xmlWriter.newline()
			for lig in ligSets:
				xmlWriter.simpletag("Ligature", glyph=lig.LigGlyph,
					components=",".join(lig.Component))
				xmlWriter.newline()
			xmlWriter.endtag("LigatureSet")
			xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
		ligatures = getattr(self, "ligatures", None)
		if ligatures is None:
			ligatures = {}
			self.ligatures = ligatures
		glyphName = attrs["glyph"]
		ligs = []
		ligatures[glyphName] = ligs
		for element in content:
			if not isinstance(element, tuple):
				continue
			name, attrs, content = element
			lig = Ligature()
			lig.LigGlyph = attrs["glyph"]
			components = attrs["components"]
			lig.Component = components.split(",") if components else []
			lig.CompCount = len(lig.Component)
			ligs.append(lig)


class COLR(BaseTable):

	def decompile(self, reader, font):
		# COLRv0 is exceptional in that LayerRecordCount appears *after* the
		# LayerRecordArray it counts, but the parser logic expects Count fields
		# to always precede the arrays. Here we work around this by parsing the
		# LayerRecordCount before the rest of the table, and storing it in
		# the reader's local state.
		subReader = reader.getSubReader(offset=0)
		for conv in self.getConverters():
			if conv.name != "LayerRecordCount":
				subReader.advance(conv.staticSize)
				continue
			conv = self.getConverterByName("LayerRecordCount")
			reader[conv.name] = conv.read(subReader, font, tableDict={})
			break
		else:
			raise AssertionError("LayerRecordCount converter not found")
		return BaseTable.decompile(self, reader, font)

	def preWrite(self, font):
		# The writer similarly assumes Count values precede the things counted,
		# thus here we pre-initialize a CountReference; the actual count value
		# will be set to the lenght of the array by the time this is assembled.
		self.LayerRecordCount = None
		return {
			**self.__dict__,
			"LayerRecordCount": CountReference(self.__dict__, "LayerRecordCount")
		}


class LookupList(BaseTable):
	@property
	def table(self):
		for l in self.Lookup:
			for st in l.SubTable:
				if type(st).__name__.endswith("Subst"):
					return "GSUB"
				if type(st).__name__.endswith("Pos"):
					return "GPOS"
		raise ValueError

	def toXML2(self, xmlWriter, font):
		if not font or "Debg" not in font or LOOKUP_DEBUG_INFO_KEY not in font["Debg"].data:
			return super().toXML2(xmlWriter, font)
		debugData = font["Debg"].data[LOOKUP_DEBUG_INFO_KEY][self.table]
		for conv in self.getConverters():
			if conv.repeat:
				value = getattr(self, conv.name, [])
				for lookupIndex, item in enumerate(value):
					if str(lookupIndex) in debugData:
						info = LookupDebugInfo(*debugData[str(lookupIndex)])
						tag = info.location
						if info.name:
							tag = f'{info.name}: {tag}'
						if info.feature:
							script,language,feature = info.feature
							tag = f'{tag} in {feature} ({script}/{language})'
						xmlWriter.comment(tag)
						xmlWriter.newline()

					conv.xmlWrite(xmlWriter, font, item, conv.name,
							[("index", lookupIndex)])
			else:
				if conv.aux and not eval(conv.aux, None, vars(self)):
					continue
				value = getattr(self, conv.name, None) # TODO Handle defaults instead of defaulting to None!
				conv.xmlWrite(xmlWriter, font, value, conv.name, [])

class BaseGlyphRecordArray(BaseTable):

	def preWrite(self, font):
		self.BaseGlyphRecord = sorted(
			self.BaseGlyphRecord,
			key=lambda rec: font.getGlyphID(rec.BaseGlyph)
		)
		return self.__dict__.copy()


class BaseGlyphV1List(BaseTable):

	def preWrite(self, font):
		self.BaseGlyphV1Record = sorted(
			self.BaseGlyphV1Record,
			key=lambda rec: font.getGlyphID(rec.BaseGlyph)
		)
		return self.__dict__.copy()



class VariableValue(namedtuple("VariableValue", ["value", "varIdx"])):
	__slots__ = ()

	_value_mapper = None

	def __new__(cls, value, varIdx=0):
		return super().__new__(
			cls,
			cls._value_mapper(value) if cls._value_mapper else value,
			varIdx
		)

	@classmethod
	def _make(cls, iterable):
		if cls._value_mapper:
			it = iter(iterable)
			try:
				value = next(it)
			except StopIteration:
				pass
			else:
				value = cls._value_mapper(value)
				iterable = itertools.chain((value,), it)
		return super()._make(iterable)


class VariableFloat(VariableValue):
	__slots__ = ()
	_value_mapper = float


class VariableInt(VariableValue):
	__slots__ = ()
	_value_mapper = otRound


class ExtendMode(IntEnum):
	PAD = 0
	REPEAT = 1
	REFLECT = 2


# For each subtable format there is a class. However, we don't really distinguish
# between "field name" and "format name": often these are the same. Yet there's
# a whole bunch of fields with different names. The following dict is a mapping
# from "format name" to "field name". _buildClasses() uses this to create a
# subclass for each alternate field name.
#
_equivalents = {
	'MarkArray': ("Mark1Array",),
	'LangSys': ('DefaultLangSys',),
	'Coverage': ('MarkCoverage', 'BaseCoverage', 'LigatureCoverage', 'Mark1Coverage',
			'Mark2Coverage', 'BacktrackCoverage', 'InputCoverage',
			'LookAheadCoverage', 'VertGlyphCoverage', 'HorizGlyphCoverage',
			'TopAccentCoverage', 'ExtendedShapeCoverage', 'MathKernCoverage'),
	'ClassDef': ('ClassDef1', 'ClassDef2', 'BacktrackClassDef', 'InputClassDef',
			'LookAheadClassDef', 'GlyphClassDef', 'MarkAttachClassDef'),
	'Anchor': ('EntryAnchor', 'ExitAnchor', 'BaseAnchor', 'LigatureAnchor',
			'Mark2Anchor', 'MarkAnchor'),
	'Device': ('XPlaDevice', 'YPlaDevice', 'XAdvDevice', 'YAdvDevice',
			'XDeviceTable', 'YDeviceTable', 'DeviceTable'),
	'Axis': ('HorizAxis', 'VertAxis',),
	'MinMax': ('DefaultMinMax',),
	'BaseCoord': ('MinCoord', 'MaxCoord',),
	'JstfLangSys': ('DefJstfLangSys',),
	'JstfGSUBModList': ('ShrinkageEnableGSUB', 'ShrinkageDisableGSUB', 'ExtensionEnableGSUB',
			'ExtensionDisableGSUB',),
	'JstfGPOSModList': ('ShrinkageEnableGPOS', 'ShrinkageDisableGPOS', 'ExtensionEnableGPOS',
			'ExtensionDisableGPOS',),
	'JstfMax': ('ShrinkageJstfMax', 'ExtensionJstfMax',),
	'MathKern': ('TopRightMathKern', 'TopLeftMathKern', 'BottomRightMathKern',
			'BottomLeftMathKern'),
	'MathGlyphConstruction': ('VertGlyphConstruction', 'HorizGlyphConstruction'),
}

#
# OverFlow logic, to automatically create ExtensionLookups
# XXX This should probably move to otBase.py
#

def fixLookupOverFlows(ttf, overflowRecord):
	""" Either the offset from the LookupList to a lookup overflowed, or
	an offset from a lookup to a subtable overflowed.
	The table layout is:
	GPSO/GUSB
		Script List
		Feature List
		LookUpList
			Lookup[0] and contents
				SubTable offset list
					SubTable[0] and contents
					...
					SubTable[n] and contents
			...
			Lookup[n] and contents
				SubTable offset list
					SubTable[0] and contents
					...
					SubTable[n] and contents
	If the offset to a lookup overflowed (SubTableIndex is None)
		we must promote the *previous*	lookup to an Extension type.
	If the offset from a lookup to subtable overflowed, then we must promote it
		to an Extension Lookup type.
	"""
	ok = 0
	lookupIndex = overflowRecord.LookupListIndex
	if (overflowRecord.SubTableIndex is None):
		lookupIndex = lookupIndex - 1
	if lookupIndex < 0:
		return ok
	if overflowRecord.tableType == 'GSUB':
		extType = 7
	elif overflowRecord.tableType == 'GPOS':
		extType = 9

	lookups = ttf[overflowRecord.tableType].table.LookupList.Lookup
	lookup = lookups[lookupIndex]
	# If the previous lookup is an extType, look further back. Very unlikely, but possible.
	while lookup.SubTable[0].__class__.LookupType == extType:
		lookupIndex = lookupIndex -1
		if lookupIndex < 0:
			return ok
		lookup = lookups[lookupIndex]

	lookup.LookupType = extType
	for si in range(len(lookup.SubTable)):
		subTable = lookup.SubTable[si]
		extSubTableClass = lookupTypes[overflowRecord.tableType][extType]
		extSubTable = extSubTableClass()
		extSubTable.Format = 1
		extSubTable.ExtSubTable = subTable
		lookup.SubTable[si] = extSubTable
	ok = 1
	return ok

def splitMultipleSubst(oldSubTable, newSubTable, overflowRecord):
	ok = 1
	newSubTable.Format = oldSubTable.Format
	oldMapping = sorted(oldSubTable.mapping.items())
	oldLen = len(oldMapping)

	if overflowRecord.itemName in ['Coverage', 'RangeRecord']:
		# Coverage table is written last. Overflow is to or within the
		# the coverage table. We will just cut the subtable in half.
		newLen = oldLen // 2

	elif overflowRecord.itemName == 'Sequence':
		# We just need to back up by two items from the overflowed
		# Sequence index to make sure the offset to the Coverage table
		# doesn't overflow.
		newLen = overflowRecord.itemIndex - 1

	newSubTable.mapping = {}
	for i in range(newLen, oldLen):
		item = oldMapping[i]
		key = item[0]
		newSubTable.mapping[key] = item[1]
		del oldSubTable.mapping[key]

	return ok

def splitAlternateSubst(oldSubTable, newSubTable, overflowRecord):
	ok = 1
	newSubTable.Format = oldSubTable.Format
	if hasattr(oldSubTable, 'sortCoverageLast'):
		newSubTable.sortCoverageLast = oldSubTable.sortCoverageLast

	oldAlts = sorted(oldSubTable.alternates.items())
	oldLen = len(oldAlts)

	if overflowRecord.itemName in [ 'Coverage', 'RangeRecord']:
		# Coverage table is written last. overflow is to or within the
		# the coverage table. We will just cut the subtable in half.
		newLen = oldLen//2

	elif overflowRecord.itemName == 'AlternateSet':
		# We just need to back up by two items
		# from the overflowed AlternateSet index to make sure the offset
		# to the Coverage table doesn't overflow.
		newLen = overflowRecord.itemIndex - 1

	newSubTable.alternates = {}
	for i in range(newLen, oldLen):
		item = oldAlts[i]
		key = item[0]
		newSubTable.alternates[key] = item[1]
		del oldSubTable.alternates[key]

	return ok


def splitLigatureSubst(oldSubTable, newSubTable, overflowRecord):
	ok = 1
	newSubTable.Format = oldSubTable.Format
	oldLigs = sorted(oldSubTable.ligatures.items())
	oldLen = len(oldLigs)

	if overflowRecord.itemName in [ 'Coverage', 'RangeRecord']:
		# Coverage table is written last. overflow is to or within the
		# the coverage table. We will just cut the subtable in half.
		newLen = oldLen//2

	elif overflowRecord.itemName == 'LigatureSet':
		# We just need to back up by two items
		# from the overflowed AlternateSet index to make sure the offset
		# to the Coverage table doesn't overflow.
		newLen = overflowRecord.itemIndex - 1

	newSubTable.ligatures = {}
	for i in range(newLen, oldLen):
		item = oldLigs[i]
		key = item[0]
		newSubTable.ligatures[key] = item[1]
		del oldSubTable.ligatures[key]

	return ok


def splitPairPos(oldSubTable, newSubTable, overflowRecord):
	st = oldSubTable
	ok = False
	newSubTable.Format = oldSubTable.Format
	if oldSubTable.Format == 1 and len(oldSubTable.PairSet) > 1:
		for name in 'ValueFormat1', 'ValueFormat2':
			setattr(newSubTable, name, getattr(oldSubTable, name))

		# Move top half of coverage to new subtable

		newSubTable.Coverage = oldSubTable.Coverage.__class__()

		coverage = oldSubTable.Coverage.glyphs
		records = oldSubTable.PairSet

		oldCount = len(oldSubTable.PairSet) // 2

		oldSubTable.Coverage.glyphs = coverage[:oldCount]
		oldSubTable.PairSet = records[:oldCount]

		newSubTable.Coverage.glyphs = coverage[oldCount:]
		newSubTable.PairSet = records[oldCount:]

		oldSubTable.PairSetCount = len(oldSubTable.PairSet)
		newSubTable.PairSetCount = len(newSubTable.PairSet)

		ok = True

	elif oldSubTable.Format == 2 and len(oldSubTable.Class1Record) > 1:
		if not hasattr(oldSubTable, 'Class2Count'):
			oldSubTable.Class2Count = len(oldSubTable.Class1Record[0].Class2Record)
		for name in 'Class2Count', 'ClassDef2', 'ValueFormat1', 'ValueFormat2':
			setattr(newSubTable, name, getattr(oldSubTable, name))

		# The two subtables will still have the same ClassDef2 and the table
		# sharing will still cause the sharing to overflow.  As such, disable
		# sharing on the one that is serialized second (that's oldSubTable).
		oldSubTable.DontShare = True

		# Move top half of class numbers to new subtable

		newSubTable.Coverage = oldSubTable.Coverage.__class__()
		newSubTable.ClassDef1 = oldSubTable.ClassDef1.__class__()

		coverage = oldSubTable.Coverage.glyphs
		classDefs = oldSubTable.ClassDef1.classDefs
		records = oldSubTable.Class1Record

		oldCount = len(oldSubTable.Class1Record) // 2
		newGlyphs = set(k for k,v in classDefs.items() if v >= oldCount)

		oldSubTable.Coverage.glyphs = [g for g in coverage if g not in newGlyphs]
		oldSubTable.ClassDef1.classDefs = {k:v for k,v in classDefs.items() if v < oldCount}
		oldSubTable.Class1Record = records[:oldCount]

		newSubTable.Coverage.glyphs = [g for g in coverage if g in newGlyphs]
		newSubTable.ClassDef1.classDefs = {k:(v-oldCount) for k,v in classDefs.items() if v > oldCount}
		newSubTable.Class1Record = records[oldCount:]

		oldSubTable.Class1Count = len(oldSubTable.Class1Record)
		newSubTable.Class1Count = len(newSubTable.Class1Record)

		ok = True

	return ok


def splitMarkBasePos(oldSubTable, newSubTable, overflowRecord):
	# split half of the mark classes to the new subtable
	classCount = oldSubTable.ClassCount
	if classCount < 2:
		# oh well, not much left to split...
		return False

	oldClassCount = classCount // 2
	newClassCount = classCount - oldClassCount

	oldMarkCoverage, oldMarkRecords = [], []
	newMarkCoverage, newMarkRecords = [], []
	for glyphName, markRecord in zip(
		oldSubTable.MarkCoverage.glyphs,
		oldSubTable.MarkArray.MarkRecord
	):
		if markRecord.Class < oldClassCount:
			oldMarkCoverage.append(glyphName)
			oldMarkRecords.append(markRecord)
		else:
			markRecord.Class -= oldClassCount
			newMarkCoverage.append(glyphName)
			newMarkRecords.append(markRecord)

	oldBaseRecords, newBaseRecords = [], []
	for rec in oldSubTable.BaseArray.BaseRecord:
		oldBaseRecord, newBaseRecord = rec.__class__(), rec.__class__()
		oldBaseRecord.BaseAnchor = rec.BaseAnchor[:oldClassCount]
		newBaseRecord.BaseAnchor = rec.BaseAnchor[oldClassCount:]
		oldBaseRecords.append(oldBaseRecord)
		newBaseRecords.append(newBaseRecord)

	newSubTable.Format = oldSubTable.Format

	oldSubTable.MarkCoverage.glyphs = oldMarkCoverage
	newSubTable.MarkCoverage = oldSubTable.MarkCoverage.__class__()
	newSubTable.MarkCoverage.Format = oldSubTable.MarkCoverage.Format
	newSubTable.MarkCoverage.glyphs = newMarkCoverage

	# share the same BaseCoverage in both halves
	newSubTable.BaseCoverage = oldSubTable.BaseCoverage

	oldSubTable.ClassCount = oldClassCount
	newSubTable.ClassCount = newClassCount

	oldSubTable.MarkArray.MarkRecord = oldMarkRecords
	newSubTable.MarkArray = oldSubTable.MarkArray.__class__()
	newSubTable.MarkArray.MarkRecord = newMarkRecords

	oldSubTable.MarkArray.MarkCount = len(oldMarkRecords)
	newSubTable.MarkArray.MarkCount = len(newMarkRecords)

	oldSubTable.BaseArray.BaseRecord = oldBaseRecords
	newSubTable.BaseArray = oldSubTable.BaseArray.__class__()
	newSubTable.BaseArray.BaseRecord = newBaseRecords

	oldSubTable.BaseArray.BaseCount = len(oldBaseRecords)
	newSubTable.BaseArray.BaseCount = len(newBaseRecords)

	return True


splitTable = {	'GSUB': {
#					1: splitSingleSubst,
					2: splitMultipleSubst,
					3: splitAlternateSubst,
					4: splitLigatureSubst,
#					5: splitContextSubst,
#					6: splitChainContextSubst,
#					7: splitExtensionSubst,
#					8: splitReverseChainSingleSubst,
					},
				'GPOS': {
#					1: splitSinglePos,
					2: splitPairPos,
#					3: splitCursivePos,
					4: splitMarkBasePos,
#					5: splitMarkLigPos,
#					6: splitMarkMarkPos,
#					7: splitContextPos,
#					8: splitChainContextPos,
#					9: splitExtensionPos,
					}

			}

def fixSubTableOverFlows(ttf, overflowRecord):
	"""
	An offset has overflowed within a sub-table. We need to divide this subtable into smaller parts.
	"""
	table = ttf[overflowRecord.tableType].table
	lookup = table.LookupList.Lookup[overflowRecord.LookupListIndex]
	subIndex = overflowRecord.SubTableIndex
	subtable = lookup.SubTable[subIndex]

	# First, try not sharing anything for this subtable...
	if not hasattr(subtable, "DontShare"):
		subtable.DontShare = True
		return True

	if hasattr(subtable, 'ExtSubTable'):
		# We split the subtable of the Extension table, and add a new Extension table
		# to contain the new subtable.

		subTableType = subtable.ExtSubTable.__class__.LookupType
		extSubTable = subtable
		subtable = extSubTable.ExtSubTable
		newExtSubTableClass = lookupTypes[overflowRecord.tableType][extSubTable.__class__.LookupType]
		newExtSubTable = newExtSubTableClass()
		newExtSubTable.Format = extSubTable.Format
		toInsert = newExtSubTable

		newSubTableClass = lookupTypes[overflowRecord.tableType][subTableType]
		newSubTable = newSubTableClass()
		newExtSubTable.ExtSubTable = newSubTable
	else:
		subTableType = subtable.__class__.LookupType
		newSubTableClass = lookupTypes[overflowRecord.tableType][subTableType]
		newSubTable = newSubTableClass()
		toInsert = newSubTable

	if hasattr(lookup, 'SubTableCount'): # may not be defined yet.
		lookup.SubTableCount = lookup.SubTableCount + 1

	try:
		splitFunc = splitTable[overflowRecord.tableType][subTableType]
	except KeyError:
		log.error(
			"Don't know how to split %s lookup type %s",
			overflowRecord.tableType,
			subTableType,
		)
		return False

	ok = splitFunc(subtable, newSubTable, overflowRecord)
	if ok:
		lookup.SubTable.insert(subIndex + 1, toInsert)
	return ok

# End of OverFlow logic


def _buildClasses():
	import re
	from .otData import otData

	formatPat = re.compile(r"([A-Za-z0-9]+)Format(\d+)$")
	namespace = globals()

	# populate module with classes
	for name, table in otData:
		baseClass = BaseTable
		m = formatPat.match(name)
		if m:
			# XxxFormatN subtable, we only add the "base" table
			name = m.group(1)
			baseClass = FormatSwitchingBaseTable
		if name not in namespace:
			# the class doesn't exist yet, so the base implementation is used.
			cls = type(name, (baseClass,), {})
			if name in ('GSUB', 'GPOS'):
				cls.DontShare = True
			namespace[name] = cls

	for base, alts in _equivalents.items():
		base = namespace[base]
		for alt in alts:
			namespace[alt] = base

	global lookupTypes
	lookupTypes = {
		'GSUB': {
			1: SingleSubst,
			2: MultipleSubst,
			3: AlternateSubst,
			4: LigatureSubst,
			5: ContextSubst,
			6: ChainContextSubst,
			7: ExtensionSubst,
			8: ReverseChainSingleSubst,
		},
		'GPOS': {
			1: SinglePos,
			2: PairPos,
			3: CursivePos,
			4: MarkBasePos,
			5: MarkLigPos,
			6: MarkMarkPos,
			7: ContextPos,
			8: ChainContextPos,
			9: ExtensionPos,
		},
		'mort': {
			4: NoncontextualMorph,
		},
		'morx': {
			0: RearrangementMorph,
			1: ContextualMorph,
			2: LigatureMorph,
			# 3: Reserved,
			4: NoncontextualMorph,
			5: InsertionMorph,
		},
	}
	lookupTypes['JSTF'] = lookupTypes['GPOS']  # JSTF contains GPOS
	for lookupEnum in lookupTypes.values():
		for enum, cls in lookupEnum.items():
			cls.LookupType = enum

	global featureParamTypes
	featureParamTypes = {
		'size': FeatureParamsSize,
	}
	for i in range(1, 20+1):
		featureParamTypes['ss%02d' % i] = FeatureParamsStylisticSet
	for i in range(1, 99+1):
		featureParamTypes['cv%02d' % i] = FeatureParamsCharacterVariants

	# add converters to classes
	from .otConverters import buildConverters
	for name, table in otData:
		m = formatPat.match(name)
		if m:
			# XxxFormatN subtable, add converter to "base" table
			name, format = m.groups()
			format = int(format)
			cls = namespace[name]
			if not hasattr(cls, "converters"):
				cls.converters = {}
				cls.convertersByName = {}
			converters, convertersByName = buildConverters(table[1:], namespace)
			cls.converters[format] = converters
			cls.convertersByName[format] = convertersByName
			# XXX Add staticSize?
		else:
			cls = namespace[name]
			cls.converters, cls.convertersByName = buildConverters(table, namespace)
			# XXX Add staticSize?


_buildClasses()


def _getGlyphsFromCoverageTable(coverage):
	if coverage is None:
		# empty coverage table
		return []
	else:
		return coverage.glyphs
