require 'bmp'

require 'core_ext/array/extract_options.rb' unless Array.method_defined?(:extract_options!)
require 'bit-struct' unless Object.const_defined?(:BitStruct)
require 'chunky_png' unless Object.const_defined?(:ChunkyPNG)

require 'ico/version'
require 'ico/utils'
require 'ico/icon_dir'
require 'ico/icon_dir_entry'
require 'ico/icon_image'

#
# @see https://en.wikipedia.org/wiki/ICO_(file_format)
#
module ICO

  # make all methods class-methods
  extend self

  # create ICO object
  #
  # @param filename_array [String, Array<String>] filename, or array of filenames
  # @return               [BitStruct]
  #
  def new(filename_array)
    raise ArgumentError unless (filename_array.is_a?(Array) || filename_array.is_a?(String))

    # ensure non-nested array
    fn_array = [filename_array].flatten

    # ensure .png extensions
    raise "more than PNG format files in #{filename_array.inspect}" if ICO::Utils.contains_other_than_ext?(fn_array, :png)

    fn_array_length       = fn_array.length
    icon_dir              = ICO::IconDir.new
    icon_dir.image_count  = fn_array.length
    offset                = ICO::IconDir::LENGTH_IN_BYTES + (fn_array_length * ICO::IconDirEntry::LENGTH_IN_BYTES)
    entries               = Array.new(fn_array_length) {ICO::IconDirEntry.new}
    images                = Array.new(fn_array_length) {ICO::IconImage.new}
    # reorder by image size
    images_array          = ICO::Utils.sizes_hash(fn_array, true, true).values

    images_array.each_with_index do |fn,i| 
      img                 = ChunkyPNG::Image.from_file(fn)
      #img_hash            = BMP::Utils.parse_image(img, ICO::IconImage::HEADER_SIZE_IN_BYTES)
      img_hash            = BMP::Utils.parse_image(img)
      file_size           = img_hash[:image_size] + ICO::IconImage::HEADER_SIZE_IN_BYTES

      entry               = entries[i]
      image               = images[i]

      entry.width         = img_hash[:image_width] 
      entry.height        = img_hash[:image_height] 
      #entry.bytes_in_res  = img_hash[:file_size] 
      entry.bytes_in_res  = file_size
      entry.image_offset  = offset

      image.width         = img_hash[:image_width]
      image.height        = (img_hash[:image_height] * 2)
      image.size_image    = img_hash[:image_size]  
      image.data          = img_hash[:pixel_array] 

      #offset              += img_hash[:file_size]
      offset              += file_size
    end

    # IconDirEntry + IconImage section as binary data string
    icon_dir.data         = entries.join + images.join

    icon_dir
  end

  # PNG to ICO
  #
  # @param input_filename   [Array<String>,String]  "/path/to/example.png" OR ["/path/to/example.png", ...]
  # @param output_filename  [String]                "/path/to/example_generated.ico"
  # @return                 [String]                filename of generated ico
  #
  def png_to_ico(filename_array, output_filename, overwrite=false)
    ico =  ICO.new(filename_array)
    
    unless overwrite
      raise "File exists: #{output_filename}" if File.exist?(output_filename)
    end

    IO.write(output_filename, ico) 
  end

  # PNG to ICO force overwrite output_filename
  #
  def png_to_ico!(filename_array, output_filename)
    png_to_ico(filename_array, output_filename, true)
  end

  # PNG to resized PNGs to ICO
  #
  # @param input_filename   [String]                "/path/to/example.png"
  # @param sizes_array      [Array<Array<Integer,Integer]>>, Array<Integer>]  
  #   rectangles use Array with XY: `[x,y]`
  #   squares use single Integer `N`
  #   mixed indices is valid
  #   example: `[24, [24,24], [480,270], 888] # a[0] => 24x24; a[1] => 24x24; a[2] => 480x270; a[3] => 888x888`
  # @param output_filename  [String]                "/path/to/example.ico"
  # @return                 [String]                filename of generated ico
  #
  def png_resize_to_ico(input_filename, sizes_array, output_filename)
    output_dir = ICO::Utils.png_to_sizes(input_filename, sizes_array)
    filename_array = Dir.glob(File.join(output_dir, '**/*'))
    png_to_ico(filename_array, output_filename)
  end
end