require 'net/http'

module WickedPdf
  module AssetHelper
    ASSET_URL_REGEX = /url\(['"]?([^'"]+?)['"]?\)/

    def self.root_path
      String === Rails.root ? Pathname.new(Rails.root) : Rails.root
    end

    def self.add_extension(filename, extension)
      filename.to_s.split('.').include?(extension) ? filename : "#{filename}.#{extension}"
    end

    def wicked_pdf_asset_base64(path)
      asset = find_asset(path)
      raise "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 = WickedPdf::AssetHelper.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
          "url(#{wicked_pdf_asset_path(Regexp.last_match[1])})"
        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 = WickedPdf::AssetHelper.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 = WickedPdf::AssetHelper.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_or_absolute_asset?(source)
        asset = asset_path(source)
        pathname = prepend_protocol(asset)
        if pathname =~ URI_REGEXP
          # asset_path returns an absolute URL using asset_host if asset_host is set
          pathname
        else
          File.join(Rails.public_path, asset.sub(/\A#{Rails.application.config.action_controller.relative_url_root}/, ''))
        end
      else
        asset = find_asset(source)
        if asset
          # older versions need pathname, Sprockets 4 supports only filename
          asset.respond_to?(:filename) ? asset.filename : asset.pathname
        else
          File.join(Rails.public_path, source)
        end
      end
    end

    def find_asset(path)
      if Rails.application.assets.respond_to?(:find_asset)
        Rails.application.assets.find_asset(path, :base_path => Rails.application.root.to_s)
      else
        Sprockets::Railtie.build_environment(Rails.application).find_asset(path, :base_path => Rails.application.root.to_s)
      end
    end

    # will prepend a http or default_protocol to a protocol relative URL
    # or when no protcol is set.
    def prepend_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_or_absolute_asset?(source)
      Rails.configuration.assets.compile == false ||
        source.to_s[0] == '/' ||
        source.to_s.match(/\Ahttps?\:\/\//)
    end

    def read_asset(source)
      if precompiled_or_absolute_asset?(source)
        pathname = asset_pathname(source)
        if pathname =~ URI_REGEXP
          read_from_uri(pathname)
        elsif File.file?(pathname)
          IO.read(pathname)
        end
      else
        find_asset(source).to_s
      end
    end

    def read_from_uri(uri)
      asset = Net::HTTP.get(URI(uri))
      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
      nil
    end
  end
end