class PDF::Reader::FontDescriptor

def glyph_to_pdf_scale_factor
  if @is_ttf
    @glyph_to_pdf_sf ||= (1.0 / ttf_program_stream.header.units_per_em) * 1000.0
  else
    @glyph_to_pdf_sf ||= 1.0
  end
  @glyph_to_pdf_sf
end

def glyph_width(char_code)
  if @is_ttf
    if ttf_program_stream.cmap.unicode.length > 0
      glyph_id = ttf_program_stream.cmap.unicode.first[char_code]
    else
      glyph_id = char_code
    end
    char_metric = ttf_program_stream.horizontal_metrics.metrics[glyph_id]
    if char_metric
      char_metric.advance_width
    else
      0
    end
  end
end

def initialize(ohash, fd_hash)
  # TODO change these to typed derefs
  @ascent                = ohash.deref_number(fd_hash[:Ascent])    || 0
  @descent               = ohash.deref_number(fd_hash[:Descent])   || 0
  @missing_width         = ohash.deref_number(fd_hash[:MissingWidth]) || 0
  @font_bounding_box     = ohash.deref_array_of_numbers(fd_hash[:FontBBox])  || [0,0,0,0]
  @avg_width             = ohash.deref_number(fd_hash[:AvgWidth])  || 0
  @cap_height            = ohash.deref_number(fd_hash[:CapHeight]) || 0
  @font_flags            = ohash.deref_integer(fd_hash[:Flags])     || 0
  @italic_angle          = ohash.deref_number(fd_hash[:ItalicAngle])
  @font_name             = ohash.deref_name(fd_hash[:FontName]).to_s
  @leading               = ohash.deref_number(fd_hash[:Leading])   || 0
  @max_width             = ohash.deref_number(fd_hash[:MaxWidth])  || 0
  @stem_v                = ohash.deref_number(fd_hash[:StemV])
  @x_height              = ohash.deref_number(fd_hash[:XHeight])
  @font_stretch          = ohash.deref_name(fd_hash[:FontStretch]) || :Normal
  @font_weight           = ohash.deref_number(fd_hash[:FontWeight])  || 400
  @font_family           = ohash.deref_string(fd_hash[:FontFamily])
  # A FontDescriptor may have an embedded font program in FontFile
  # (Type 1 Font Program), FontFile2 (TrueType font program), or
  # FontFile3 (Other font program as defined by Subtype entry)
  # Subtype entries:
  # 1) Type1C:        Type 1 Font Program in Compact Font Format
  # 2) CIDFontType0C: Type 0 Font Program in Compact Font Format
  # 3) OpenType:      OpenType Font Program
  # see Section 9.9, PDF 32000-1:2008, pp 288-292
  @font_program_stream = ohash.deref_stream(fd_hash[:FontFile2])
  #TODO handle FontFile and FontFile3
  @is_ttf = true if @font_program_stream
end

def ttf_program_stream
  @ttf_program_stream ||= TTFunk::File.new(@font_program_stream.unfiltered_data)
end