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 'relaxo/query_server/shell'
require 'relaxo/query_server/mapper'
require 'relaxo/query_server/reducer'
require 'relaxo/query_server/designer'

module Relaxo
    module QueryServer
        class CompilationError < StandardError
        end
        
        # A query server context includes all state required for implementing the query server protocol.
        class Context
            # Given a function as text, and an execution scope, return a callable object.
            def parse_function(text, scope, filename = 'query-server')
                safe_level = @options[:safe] || 0
            
                function = lambda { $SAFE = safe_level; eval(text, scope, filename) }.call
            
                unless function.respond_to? :call
                    raise CompilationError.new('Expression does not evaluate to procedure!')
                end
                
                return function
            end
            
            def initialize(shell, options = {})
                @shell = shell
                @options = options
                
                @mapper = Mapper.new(self)
                @reducer = Reducer.new(self)
                @designer = Designer.new(self)
                
                @config = {}
            end
            
            attr :config
            attr :shell
            
            # Return an error structure from the given exception.
            def error_for_exception(exception)
                ["error", exception.class.to_s, exception.message, exception.backtrace]
            end
            
            # Process a single command as per the query server protocol.
            def run(command)
                case command[0]
                # ** Map functionality
                when 'add_fun'
                    @mapper.add_function command[1]; true
                when 'add_lib'
                    @mapper.add_libraries command[1]
                    @reducer.add_libraries command[1]; true
                when 'map_doc'
                    @mapper.map command[1]
                when 'reset'
                    @config = command[1] || {}
                    @mapper = Mapper.new(self); true
                
                # ** Reduce functionality
                when 'reduce'
                    @reducer.reduce command[1], command[2]
                when 'rereduce'
                    @reducer.rereduce command[1], command[2]
                
                # ** Design document functionality
                when 'ddoc'
                    if command[1] == 'new'
                        @designer.create(command[2], command[3]); true
                    else
                        @designer.run(command[1], command[2], command[3])
                    end
                end
            rescue Exception => exception
                error_for_exception(exception)
            end
            
            # Write a log message back to the shell.
            def log(message)
                @shell.write_object ['log', message]
            end
        end
    end
end