require "sass"
require "cgi"
require "base64"
require "chunky_png"

module Sass::Script::Functions

  def ustyle_version
    ::Sass::Script::String.new ::Ustyle::VERSION
  end
  declare :ustyle_version, []

  def inline_asset(source)
    assert_type source, :String
    if Ustyle.sprockets?
      ::Sass::Script::String.new "url(#{sprockets_context.asset_data_uri(source.value)})"
    else
      path = File.join(::Ustyle.assets_path, "images", source.value)
      asset_data_uri(path)
    end
  end
  declare :inline_asset, :args => [:source]

  def inline_svg(source)
    assert_type source, :String
    if Ustyle.sprockets?
      svg = escaped_svg(sprockets_context.environment.find_asset(source.value).to_s)
      ::Sass::Script::String.new "url(data:#{Ustyle.mime_type_for(source.value)};charset=utf-8,#{svg})"
    else
      path = File.join(::Ustyle.assets_path, "images", source.value)
      asset_data_uri(path, svg = true)
    end
  end
  declare :inline_svg, :args => [:source]

  def base64encode(string)
    assert_type string, :String
    Sass::Script::String.new(Base64.strict_encode64(string.value))
  end
  declare :base64encode, :args => [:string]

  def ustyle_image_path(source)
    ustyle_asset_path source, :image
  end
  declare :ustyle_image_path, :args => [:source]

  def ustyle_asset_path(source, type)
    url = if Ustyle.sprockets?
      sprockets_context.send(:"#{type}_path", source.value)
    else
      Ustyle.cloudfront_url(source.value, type)
    end

    # sass-only
    url ||= source.value.gsub('"', '')
    Sass::Script::String.new(url, :string)
  end
  declare :ustyle_asset_path, :args => [:source, :type]

  def rgba_inline(c, px = 5)
    color = ChunkyPNG::Color.rgba(c.red, c.green, c.blue, (c.alpha * 100 * 2.55).round)
    image = ChunkyPNG::Image.new(px.to_i, px.to_i, color)
    data  = Base64.encode64(image.to_blob).gsub("\n", "")

    Sass::Script::String.new("url('data:image/png;base64,#{data}')")
  end
  declare :rgba_inline, :args => [:c, :px]

  protected

  def asset_data_uri(path, svg = false)
    asset = data(path)
    encoding = "base64"
    if svg
      asset = escaped_svg(asset)
      encoding = "charset=utf-8"
    else
      asset = CGI::escape(Base64.strict_encode64(data(path).to_s))
    end
    url = "data:#{Ustyle.mime_type_for(path)};#{encoding},#{asset}"
    ::Sass::Script::String.new "url('#{url}')"
  end

  def escaped_svg(data)
    CGI::escape(data).gsub('+', '%20')
  end

  def data(path)
    File.open(path, "rb") {|io| io.read}
  end

  def sprockets_context
    # Modern Rails way to get context:
    if options.key?(:sprockets)
      options[:sprockets][:context]
    # Sprockets-sass context:
    elsif options.key?(:custom) && options[:custom].key?(:sprockets_context)
      options[:custom][:sprockets_context]
    # Compatibility with sprockets pre 2.10.0:
    elsif (importer = options[:importer]) && importer.respond_to?(:context)
      importer.context
    end
  end
end