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/process'
require 'relaxo/query_server/library'

module Relaxo
    module QueryServer
        # Call the reduction function, and if it fails, respond with an error message.
        class ReducingProcess < Process
            def evaluate(*args)
                begin
                    call(*args)
                rescue Exception => exception
                    # If the mapping function throws an error, report the error for this document:
                    @context.error_for_exception(exception)
                end
            end
        end
        
        # Implements the `reduce` and `rereduce` functions along with all associated state.
        class Reducer < Loader
            # Create a reducer attached to the given context.
            def initialize(context)
                super()
                
                @context = context
            end
            
            # Apply the reduce function to a given list of items. Functions are typically in the form of:
            #     functions = [lambda{|keys,values,rereduce| ...}]
            #
            # such that:
            #     items = [[key1, value1], [key2, value2], [key3, value3]]
            #     functions.map{|function| function.call(all keys, all values, false)}
            #
            # @param [Array] functions 
            #     An array of functions to apply.
            # @param [Array] items
            #     A composite list of items.
            def reduce(functions, items)
                load_default
                
                functions = functions.collect do |function_text|
                    @context.parse_function(function_text, binding)
                end
                
                keys, values = [], []
                
                items.each do |value|
                    keys << value[0]
                    values << value[1]
                end
                
                result = functions.map do |function|
                    ReducingProcess.new(self, function).run(keys, values, false)
                end
                
                return [true, result]
            end
            
            # Apply the rereduce functions to a given list of values.
            #     lambda{|keys,values,rereduce| ...}.call([], values, true)
            #
            # @param [Array] functions
            #     An array of functions to apply, in the form of:
            # @param [Array] values
            #     An array of values to reduce
            def rereduce(functions, values)
                load_default
                
                functions = functions.collect do |function_text|
                    @context.parse_function(function_text, binding)
                end
                
                result = functions.map do |function|
                    ReducingProcess.new(self, function).run([], values, true)
                end
                
                return [true, result]
            end
        end
    end
end