page.coffee

###
PDFPage - represents a single page in the PDF document
By Devon Govett
###

class PDFPage
  constructor: (@document, options = {}) ->
    @size = options.size or 'letter'
    @layout = options.layout or 'portrait'
    
    # process margins
    if typeof options.margin is 'number'
      @margins = 
        top: options.margin
        left: options.margin
        bottom: options.margin
        right: options.margin
    
    # default to 1 inch margins
    else
      @margins = options.margins or DEFAULT_MARGINS
      
    # calculate page dimensions
    dimensions = if Array.isArray(@size) then @size else SIZES[@size.toUpperCase()]
    @width = dimensions[if @layout is 'portrait' then 0 else 1]
    @height = dimensions[if @layout is 'portrait' then 1 else 0]
    
    @content = @document.ref()
    
    # Initialize the Font, XObject, and ExtGState dictionaries
    @resources = @document.ref
      ProcSet: ['PDF', 'Text', 'ImageB', 'ImageC', 'ImageI']
    
    # Lazily create these dictionaries
    Object.defineProperties this,
      fonts:
        get: => @resources.data.Font ?= {}
      xobjects:
        get: => @resources.data.XObject ?= {}
      ext_gstates:
        get: => @resources.data.ExtGState ?= {}
      patterns:
        get: => @resources.data.Pattern ?= {}
      annotations:
        get: => @dictionary.data.Annots ?= []
    
    # The page dictionary
    @dictionary = @document.ref
      Type: 'Page'
      Parent: @document._root.data.Pages
      MediaBox: [0, 0, @width, @height]
      Contents: @content
      Resources: @resources
      
  maxY: ->
    @height - @margins.bottom
        
  write: (chunk) ->
    @content.write chunk
  
  end: ->
    @dictionary.end()
    @resources.end()
    @content.end()
      
  DEFAULT_MARGINS = 
    top: 72
    left: 72
    bottom: 72
    right: 72
    
  SIZES =
    '4A0': [4767.87, 6740.79]
    '2A0': [3370.39, 4767.87]
    A0: [2383.94, 3370.39]
    A1: [1683.78, 2383.94]
    A2: [1190.55, 1683.78]
    A3: [841.89, 1190.55]
    A4: [595.28, 841.89]
    A5: [419.53, 595.28]
    A6: [297.64, 419.53]
    A7: [209.76, 297.64]
    A8: [147.40, 209.76]
    A9: [104.88, 147.40]
    A10: [73.70, 104.88]
    B0: [2834.65, 4008.19]
    B1: [2004.09, 2834.65]
    B2: [1417.32, 2004.09]
    B3: [1000.63, 1417.32]
    B4: [708.66, 1000.63]
    B5: [498.90, 708.66]
    B6: [354.33, 498.90]
    B7: [249.45, 354.33]
    B8: [175.75, 249.45]
    B9: [124.72, 175.75]
    B10: [87.87, 124.72]
    C0: [2599.37, 3676.54]
    C1: [1836.85, 2599.37]
    C2: [1298.27, 1836.85]
    C3: [918.43, 1298.27]
    C4: [649.13, 918.43]
    C5: [459.21, 649.13]
    C6: [323.15, 459.21]
    C7: [229.61, 323.15]
    C8: [161.57, 229.61]
    C9: [113.39, 161.57]
    C10: [79.37, 113.39]
    RA0: [2437.80, 3458.27]
    RA1: [1729.13, 2437.80]
    RA2: [1218.90, 1729.13]
    RA3: [864.57, 1218.90]
    RA4: [609.45, 864.57]
    SRA0: [2551.18, 3628.35]
    SRA1: [1814.17, 2551.18]
    SRA2: [1275.59, 1814.17]
    SRA3: [907.09, 1275.59]
    SRA4: [637.80, 907.09]
    EXECUTIVE: [521.86, 756.00]
    FOLIO: [612.00, 936.00]
    LEGAL: [612.00, 1008.00]
    LETTER: [612.00, 792.00]
    TABLOID: [792.00, 1224.00]
  
module.exports = PDFPage