ioquatix/relaxo-query-server

# Copyright (c) 2012 Samuel G. D. Williams. <http://www.oriontransfer.co.nz>
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

require 'json'
require 'logger'

module Relaxo
    module QueryServer
        # A simple wrapper that reads and writes objects using JSON serialization to the given `input` and `output` `IO`s.
        class Shell
            def initialize(input, output)
                @input = input
                @output = output
            end
            
            attr :input
            attr :output
            
            # Read a JSON serialised object from `input`.
            def read_object
                JSON.parse @input.readline
            end

            # Write a JSON serialized object to `output`.
            def write_object object
                @output.puts object.to_json
                @output.flush
            end

            # Read commands from `input`, execute them and then write out the results.
            def run
                begin
                    while true
                        command = read_object
                        
                        result = yield command
                        
                        write_object(result)
                    end
                rescue EOFError
                    # Finish...
                end
            end
        end
        
        class DebugShell
            def initialize(log, wrapper)
                @log = log
                @wrapper = wrapper
            end
            
            # Read commands from `input`, execute them and then write out the results.
            def run
                @wrapper.run do |command|
                    @log.puts "-> #{command.inspect}"
                    
                    result = yield command
                    
                    @log.puts "<- #{result.inspect}"
                    
                    next result
                end
            end
        end
        
        # Used primarily for testing, allows the input and output of the server to be provided directly.
        class MockShell < Shell
            def initialize
                super [], []
            end

            def read_object
                if @input.size > 0
                    @input.shift
                else
                    raise EOFError.new("No more objects")
                end
            end

            def write_object object
                @output << object
            end
        end
    end
end