json repl for ruby

json-repl.rb

require 'readline'

module Repl
  module Command

    class PWD
      def self.parse argv=nil
        dir = Repl::Container.dirs.last
        '/' + (dir ? dir.join('/') : '')
      end
    end

    class CD
      def self.parse argv
        argv
      end
    end

    class LS
      def self.parse argv
        raise Repl::Exception.new("ls error!")
      end
    end

    class LoadJSON
      def self.parse argv
        raise Repl::Exception.new("load is not yet implemented!")
      end
    end

    COMMANDS = {
      :cd => CD,
      :ls => LS,
      :pwd => PWD,
      :load => LoadJSON,
    }

    def self.run!(cmd)
      cmd_name = cmd.first.to_sym
      cmd_parser = COMMANDS[cmd_name] or
        raise Repl::Exception.new "Command '#{cmd_name}' not found!"
      cmd_parser.parse(cmd)
    end

  end
end

module Repl

  class Exception < ::Exception; end

  module Container
    def self.dirs
      @dirs ||= []
    end

    def self.jsons
      @json ||= {}
    end

    def self.root
      @root
    end

    def self.current_object
      dirs.last.inject(root) {|a, e| a[e]}
    end
  end

  module_function

  def prompt
    "[#{Repl::Command::PWD.parse}] > "
  end

  def start
    while true do
      cmd = Readline.readline(prompt, true)
      break unless cmd

      cmd = cmd.strip.split(/\s+/)
      next if cmd.empty?

      begin
        result = Command.run!(cmd)
      rescue Exception => ex
        puts "input: #{ex.message}"
      else
        puts result
      end
    end
  end

end

Repl.start