require 'fastercsv'
require 'iconv'

module ActionView # :nodoc:
  module TemplateHandlers
    # Template handler for csv templates
    #
    # Add rows to your CSV file in the template by pushing arrays of columns into csv
    #
    #   # First row
    #   csv << [ 'cell 1', 'cell 2' ]
    #   # Second row
    #   csv << [ 'another cell value', 'and another' ]
    #   # etc...
    #
    # You can set the default filename for that a browser will use for 'save as' by
    # setting <tt>@filename</tt> instance variable in your controller's action method
    # e.g.
    #
    #   @filename = 'report.csv'
    #
    # You can also set the input encoding and output encoding by setting
    # <tt>@input_encoding</tt> and <tt>@output_encoding</tt> instance variables.
    # These default to 'UTF-8' and 'LATIN1' respectively. e.g.
    #
    #   @output_encoding = 'UTF-8'

    class CsvBuilder < TemplateHandler

      include Compilable

      def self.line_offset
        9
      end

      def compile(template)
        <<-EOV
        begin

          unless defined?(ActionMailer) && defined?(ActionMailer::Base) && controller.is_a?(ActionMailer::Base)
            @filename ||= "\#{controller.action_name}.csv"
            if controller.request.env['HTTP_USER_AGENT'] =~ /msie/i
              controller.response.headers['Pragma'] = 'public'
              controller.response.headers["Content-type"] = "text/plain" 
              controller.response.headers['Cache-Control'] = 'no-cache, must-revalidate, post-check=0, pre-check=0'
              controller.response.headers['Content-Disposition'] = "attachment; filename=\#{@filename}"
              controller.response.headers['Expires'] = "0" 
            else
              controller.response.headers["Content-Type"] ||= 'text/csv'
              controller.response.headers["Content-Disposition"] = "attachment; filename=\#{@filename}"
              controller.response.headers["Content-Transfer-Encoding"] = "binary"
            end
          end

          result = FasterCSV.generate(@csv_options || {}) do |csv|
            #{template.source}
          end

          # Transliterate into the required encoding if necessary
          # TODO: make defaults configurable
          @input_encoding ||= 'UTF-8'
          @output_encoding ||= 'LATIN1'

          if @input_encoding == @output_encoding
            result
          else
            # TODO: do some checking to make sure iconv works correctly in
            # current environment. See ActiveSupport::Inflector#transliterate
            # definition for details
            #
            # Not using the more standard //IGNORE//TRANLIST because it raises
            # Iconv::IllegalSequence for some inputs
            c = Iconv.new("\#{@output_encoding}//TRANSLIT//IGNORE", @input_encoding)
            c.iconv(result)
          end

        rescue Exception => e
          RAILS_DEFAULT_LOGGER.warn("Exception \#{e} \#{e.message} with class \#{e.class.name} thrown when rendering CSV")
          raise e
        end
        EOV
      end

    end
  end
end