A basic http server key/value store

server.rb

require 'socket'

# Wrapper for a key / value store that acts as our database
class DataStore
  def initialize
    @store = {}
  end

  def set(key, value)
    @store[key] = value
  end

  def get(key)
    @store[key]
  end

  def to_s
    @store.to_s
  end
end

# Encapsulate all the logic for request handling
class ResponseBuilder
  # Matches "GET /set?xxx=yyy ...and anything beyond"
  SETTER_REGEX = /\AGET \/set\?(\S*)=(\S*).*/
  # Matches "GET /get?key=xxx ...and anything beyond"
  GETTER_REGEX = /\AGET \/get\?key=(\S*).*/

  def initialize(request, datastore)
    @request = request
    @datastore = datastore
  end

  def response
    case @request
    when SETTER_REGEX
      key, value = $1, $2

      @datastore.set(key, value)

      build_http "#{ key } set to #{ value }", 200
    when GETTER_REGEX
      key, value = $1, @datastore.get($1)

      if value
        build_http value, 200
      else
        build_http "#{ key } was not found", 500
      end
    else

      build_http "Not a valid request", 500
    end
  end

  private

  # Some quick dirty HTTP response building
  def build_http(response, code)
    <<-HTTP
HTTP/1.1 #{ code } OK\r
Content-Type: text/plain\r
Content-Length: #{response.bytesize}\r
Connection: close\r
\r
#{ response }
HTTP
  end
end


# Setup the server and database
server = TCPServer.new('localhost', 4000)
datastore = DataStore.new

loop do
  socket = server.accept
  request = socket.gets

  response = ResponseBuilder.new(request, datastore).response
  socket.print response

  socket.close
end