require 'open-uri'

module WickedPdfHelper
  module Assets
    ASSET_URL_REGEX = /url\(['"]?([^'"]+?)['"]?\)/

    def wicked_pdf_asset_base64(path)
      asset = Rails.application.assets.find_asset(path)
      throw "Could not find asset '#{path}'" if asset.nil?
      base64 = Base64.encode64(asset.to_s).gsub(/\s+/, '')
      "data:#{asset.content_type};base64,#{Rack::Utils.escape(base64)}"
    end

    def wicked_pdf_stylesheet_link_tag(*sources)
      stylesheet_contents = sources.collect do |source|
        source = WickedPdfHelper.add_extension(source, 'css')
        "<style type='text/css'>#{read_asset(source)}</style>"
      end.join("\n")

      stylesheet_contents.gsub(ASSET_URL_REGEX) do
        if Regexp.last_match[1].starts_with?('data:')
          "url(#{Regexp.last_match[1]})"
        else
          asset = Regexp.last_match[1]
          "url(#{wicked_pdf_asset_path(asset)})" if asset_exists?(asset)
        end
      end.html_safe
    end

    def wicked_pdf_image_tag(img, options = {})
      image_tag wicked_pdf_asset_path(img), options
    end

    def wicked_pdf_javascript_src_tag(jsfile, options = {})
      jsfile = WickedPdfHelper.add_extension(jsfile, 'js')
      javascript_include_tag wicked_pdf_asset_path(jsfile), options
    end

    def wicked_pdf_javascript_include_tag(*sources)
      sources.collect do |source|
        source = WickedPdfHelper.add_extension(source, 'js')
        "<script type='text/javascript'>#{read_asset(source)}</script>"
      end.join("\n").html_safe
    end

    def wicked_pdf_asset_path(asset)
      if (pathname = asset_pathname(asset).to_s) =~ URI_REGEXP
        pathname
      else
        "file:///#{pathname}"
      end
    end

    private

    # borrowed from actionpack/lib/action_view/helpers/asset_url_helper.rb
    URI_REGEXP = %r{^[-a-z]+://|^(?:cid|data):|^//}

    def asset_pathname(source)
      if precompiled_asset?(source)
        if (pathname = set_protocol(asset_path(source))) =~ URI_REGEXP
          # asset_path returns an absolute URL using asset_host if asset_host is set
          pathname
        else
          File.join(Rails.public_path, asset_path(source).sub(/\A#{Rails.application.config.action_controller.relative_url_root}/, ''))
        end
      else
        Rails.application.assets.find_asset(source).pathname
      end
    end

    # will prepend a http or default_protocol to a protocol relative URL
    # or when no protcol is set.
    def set_protocol(source)
      protocol = WickedPdf.config[:default_protocol] || 'http'
      if source[0, 2] == '//'
        source = [protocol, ':', source].join
      elsif source[0] != '/' && !source[0, 8].include?('://')
        source = [protocol, '://', source].join
      end
      source
    end

    def precompiled_asset?(source)
      Rails.configuration.assets.compile == false || source.to_s[0] == '/'
    end

    def read_asset(source)
      if precompiled_asset?(source)
        if set_protocol(asset_path(source)) =~ URI_REGEXP
          read_from_uri(source)
        elsif asset_exists?(source)
          IO.read(asset_pathname(source))
        end
      else
        Rails.application.assets.find_asset(source).to_s
      end
    end

    def read_from_uri(source)
      encoding = ':UTF-8' if RUBY_VERSION > '1.8'
      asset = open(asset_pathname(source), "r#{encoding}") { |f| f.read }
      asset = gzip(asset) if WickedPdf.config[:expect_gzipped_remote_assets]
      asset
    end

    def gzip(asset)
      stringified_asset = StringIO.new(asset)
      gzipper = Zlib::GzipReader.new(stringified_asset)
      gzipper.read
    rescue Zlib::GzipFile::Error
    end

    def asset_exists?(source)
      Rails.application.assets.find_asset(source).present?
    end
  end
end