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
        # Supports `Mapper` by providing a context with an `emit` method that collects the results from the mapping function.
        class MappingProcess < Process
            def initialize(context, mapper, function)
                super(context, function)
                
                @mapper = mapper
                @results = []
            end
            
            # Emit a result
            def emit(key, value = nil)
                @results << [key, value]
            end
            
            def load(name)
                @mapper.load(name)
            end
            
            def run(*args)
                begin
                    call(*args)
                rescue Exception => exception
                    # If the mapping function throws an error, report the error for this document:
                    return @context.error_for_exception(exception)
                end
                
                return @results
            end
        end
        
        class Mapper < Loader
            def initialize(context)
                super()
                
                @context = context
                @functions = []
            end
            
            # Adds a function by parsing the text, typically containing a textual representation of a lambda.
            def add_function(text)
                @functions << @context.parse_function(text, binding)
            end
            
            # Map a document to a set of results by appling all functions.
            def map(document)
                # Force load the default library:
                load_default
                
                @functions.map do |function|
                    MappingProcess.new(@context, @libraries, function).run(document)
                end
            end
        end
    end
end