module Rid
  module Attachments
    # Mime type mapping from extensions
    MIME_TYPE_MAPPING = {
      ".html" => "text/html",
      ".js" => "text/javascript",
      ".css" => "text/css",
    }

    def reduce_attachments!
      return hash unless hash["_attachments"]
      attachments = {}
      hash["_attachments"].each do |key, value|
        data = value["data"]
        next unless data
        attachments.update key => decode_attachment(data)
      end
      hash.update "_attachments" => attachments
    end

    def map_attachments!
      return unless hash["_attachments"]
      attachments = {}
      flatten_attachements(hash["_attachments"]).each do |key, value|
        attachments.update key => {
          "data" => encode_attachment(value),
          "content_type" => mime_type_for(key)
        }
      end
      self.hash.update "_attachments" => attachments
    end

    def flatten_attachements(doc, base = nil)
      result = {}
      doc.each do |key, value|
        new_base = base ? [base, key].join('/') : key
        if value.is_a?(Hash)
          result.update flatten_attachements(value, new_base)
        else
          result.update new_base => value
        end
      end
      result
    end

    def decode_attachment(data)
      data.unpack("m").first
    end

    def encode_attachment(data)
      [data].pack("m").gsub(/\s+/,'')
    end

    def mime_type_for(filename)
      ext = File.extname(filename)
      MIME_TYPE_MAPPING[ext] || 'text/plain'
    end
  end
end