#--
#     This file is part of the X12Parser library that provides tools to
#     manipulate X12 messages using Ruby native syntax.
#
#     http://x12parser.rubyforge.org 
#     
#     Copyright (C) 2008 APP Design, Inc.
#
#     This library is free software; you can redistribute it and/or
#     modify it under the terms of the GNU Lesser General Public
#     License as published by the Free Software Foundation; either
#     version 2.1 of the License, or (at your option) any later version.
#
#     This library is distributed in the hope that it will be useful,
#     but WITHOUT ANY WARRANTY; without even the implied warranty of
#     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
#     Lesser General Public License for more details.
#
#     You should have received a copy of the GNU Lesser General Public
#     License along with this library; if not, write to the Free Software
#     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
#++
#

require "rexml/document"
include REXML 

require 'pp'

module X12

  # $Id: Parser.rb 89 2009-05-13 19:36:20Z ikk $
  #
  # Main class for creating X12 parsers and factories.

  class Parser

    # These constitute prohibited file names under Microsoft
    MS_DEVICES = [   
                  'CON',
                  'PRN',
                  'AUX',
                  'CLOCK$',
                  'NUL',
                  'COM1',
                  'LPT1',
                  'LPT2',
                  'LPT3',
                  'COM2',
                  'COM3',
                  'COM4',
                 ]

    # Creates a parser out of a definition
    def initialize(file_name)
      save_definition = @x12_definition

      # Deal with Microsoft devices
      base_name = File.basename(file_name, '.xml')
      if MS_DEVICES.find{|i| i == base_name}
        file_name = File.join(File.dirname, "#{base_name}_.xml")
      end
      #puts "Reading definition from #{file_name}"

      # Read and parse the definition
      str = File.open(file_name, 'r').read
      @dir_name = File.dirname(File.expand_path(file_name)) # to look up other files if needed
      @x12_definition = X12::XMLDefinitions.new(str)

      # Populate fields in all segments found in all the loops
      @x12_definition[X12::Loop].each_pair{|k, v|
        #puts "Populating definitions for loop #{k}"
        process_loop(v)
      } if @x12_definition[X12::Loop]

      # Merge the newly parsed definition into a saved one, if any.
      if save_definition
        @x12_definition.keys.each{|t|
          save_definition[t] ||= {}
          @x12_definition[t].keys.each{|u|
            save_definition[t][u] = @x12_definition[t][u] 
          }
          @x12_definition = save_definition
        }
      end

      #puts PP.pp(self, '')
    end # initialize

    # Parse a loop of a given name out of a string. Throws an exception if the loop name is not defined.
    def parse(loop_name, str)
      loop = @x12_definition[X12::Loop][loop_name]
      #puts "Loops to parse #{@x12_definition[X12::Loop].keys}"
      throw Exception.new("Cannot find a definition for loop #{loop_name}") unless loop
      loop = loop.dup
      loop.parse(str)
      return loop
    end # parse

    # Make an empty loop to be filled out with information
    def factory(loop_name)
      loop = @x12_definition[X12::Loop][loop_name]
      throw Exception.new("Cannot find a definition for loop #{loop_name}") unless loop
      loop = loop.dup
      return loop
    end # factory

    private

    # Recursively scan the loop and instantiate fields' definitions for all its
    # segments
    def process_loop(loop)
      loop.nodes.each{|i|
        case i
          when X12::Loop: process_loop(i)
          when X12::Segment: process_segment(i) unless i.nodes.size > 0
          else return
        end
      }
    end

    # Instantiate segment's fields as previously defined
    def process_segment(segment)
      #puts "Trying to process segment #{segment.inspect}"
      unless @x12_definition[X12::Segment] && @x12_definition[X12::Segment][segment.name]
        # Try to find it in a separate file if missing from the @x12_definition structure
        initialize(File.join(@dir_name, segment.name+'.xml'))
        segment_definition = @x12_definition[X12::Segment][segment.name]
        throw Exception.new("Cannot find a definition for segment #{segment.name}") unless segment_definition
      else
        segment_definition = @x12_definition[X12::Segment][segment.name]
      end
      segment_definition.nodes.each_index{|i|
        segment.nodes[i] = segment_definition.nodes[i] 
        # Make sure we have the validation table if any for this field. Try to read one in if missing.
        table = segment.nodes[i].validation
        if table
          unless @x12_definition[X12::Table] && @x12_definition[X12::Table][table]
            initialize(File.join(@dir_name, table+'.xml'))
            throw Exception.new("Cannot find a definition for table #{table}") unless @x12_definition[X12::Table] && @x12_definition[X12::Table][table]
          end
        end
      }
    end

  end # Parser
end