from fontTools.misc import sstruct
from fontTools.misc.textTools import readHex, safeEval
import struct


sbixGlyphHeaderFormat = """
	>
	originOffsetX: h	# The x-value of the point in the glyph relative to its
						# lower-left corner which corresponds to the origin of
						# the glyph on the screen, that is the point on the
						# baseline at the left edge of the glyph.
	originOffsetY: h	# The y-value of the point in the glyph relative to its
						# lower-left corner which corresponds to the origin of
						# the glyph on the screen, that is the point on the
						# baseline at the left edge of the glyph.
	graphicType:  4s	# e.g. "png "
"""

sbixGlyphHeaderFormatSize = sstruct.calcsize(sbixGlyphHeaderFormat)


class Glyph(object):
	def __init__(self, glyphName=None, referenceGlyphName=None, originOffsetX=0, originOffsetY=0, graphicType=None, imageData=None, rawdata=None, gid=0):
		self.gid = gid
		self.glyphName = glyphName
		self.referenceGlyphName = referenceGlyphName
		self.originOffsetX = originOffsetX
		self.originOffsetY = originOffsetY
		self.rawdata = rawdata
		self.graphicType = graphicType
		self.imageData = imageData

		# fix self.graphicType if it is null terminated or too short
		if self.graphicType is not None:
			if self.graphicType[-1] == "\0":
				self.graphicType = self.graphicType[:-1]
			if len(self.graphicType) > 4:
				from fontTools import ttLib
				raise ttLib.TTLibError("Glyph.graphicType must not be longer than 4 characters.")
			elif len(self.graphicType) < 4:
				# pad with spaces
				self.graphicType += "    "[:(4 - len(self.graphicType))]

	def decompile(self, ttFont):
		self.glyphName = ttFont.getGlyphName(self.gid)
		if self.rawdata is None:
			from fontTools import ttLib
			raise ttLib.TTLibError("No table data to decompile")
		if len(self.rawdata) > 0:
			if len(self.rawdata) < sbixGlyphHeaderFormatSize:
				from fontTools import ttLib
				#print "Glyph %i header too short: Expected %x, got %x." % (self.gid, sbixGlyphHeaderFormatSize, len(self.rawdata))
				raise ttLib.TTLibError("Glyph header too short.")

			sstruct.unpack(sbixGlyphHeaderFormat, self.rawdata[:sbixGlyphHeaderFormatSize], self)

			if self.graphicType == "dupe":
				# this glyph is a reference to another glyph's image data
				gid, = struct.unpack(">H", self.rawdata[sbixGlyphHeaderFormatSize:])
				self.referenceGlyphName = ttFont.getGlyphName(gid)
			else:
				self.imageData = self.rawdata[sbixGlyphHeaderFormatSize:]
				self.referenceGlyphName = None
		# clean up
		del self.rawdata
		del self.gid

	def compile(self, ttFont):
		if self.glyphName is None:
			from fontTools import ttLib
			raise ttLib.TTLibError("Can't compile Glyph without glyph name")
			# TODO: if ttFont has no maxp, cmap etc., ignore glyph names and compile by index?
			# (needed if you just want to compile the sbix table on its own)
		self.gid = struct.pack(">H", ttFont.getGlyphID(self.glyphName))
		if self.graphicType is None:
			self.rawdata = b""
		else:
			self.rawdata = sstruct.pack(sbixGlyphHeaderFormat, self) + self.imageData

	def toXML(self, xmlWriter, ttFont):
		if self.graphicType == None:
			# TODO: ignore empty glyphs?
			# a glyph data entry is required for each glyph,
			# but empty ones can be calculated at compile time
			xmlWriter.simpletag("glyph", name=self.glyphName)
			xmlWriter.newline()
			return
		xmlWriter.begintag("glyph",
			graphicType=self.graphicType,
			name=self.glyphName,
			originOffsetX=self.originOffsetX,
			originOffsetY=self.originOffsetY,
		)
		xmlWriter.newline()
		if self.graphicType == "dupe":
			# graphicType == "dupe" is a reference to another glyph id.
			xmlWriter.simpletag("ref", glyphname=self.referenceGlyphName)
		else:
			xmlWriter.begintag("hexdata")
			xmlWriter.newline()
			xmlWriter.dumphex(self.imageData)
			xmlWriter.endtag("hexdata")
		xmlWriter.newline()
		xmlWriter.endtag("glyph")
		xmlWriter.newline()

	def fromXML(self, name, attrs, content, ttFont):
		if name == "ref":
			# glyph is a "dupe", i.e. a reference to another glyph's image data.
			# in this case imageData contains the glyph id of the reference glyph
			# get glyph id from glyphname
			self.imageData = struct.pack(">H", ttFont.getGlyphID(safeEval("'''" + attrs["glyphname"] + "'''")))
		elif name == "hexdata":
			self.imageData = readHex(content)
		else:
			from fontTools import ttLib
			raise ttLib.TTLibError("can't handle '%s' element" % name)