require File.join(File.dirname(__FILE__), 'bnode')
require File.join(File.dirname(__FILE__), 'literal')
require File.join(File.dirname(__FILE__), 'uriref')

module RdfContext
  module TermUtils
    TERM_INSTANTIATION_DICT = {
        'U' => URIRef,
        'B' => BNode,
        #'V' => Variable,
        'L' => Literal
    }

    GRAPH_TERM_DICT = {
        #'F' => [QuotedGraph, URIRef],
        'U' => [Graph, URIRef],
        'B' => [Graph, BNode]
    }

    SUBJECT = 0
    PREDICATE = 1
    OBJECT = 2
    CONTEXT = 3

    TERM_COMBINATIONS = {
        'UUUU' => 0,
        'UUUB' => 1,
        'UUUF' => 2,
        'UUVU' => 3,
        'UUVB' => 4,
        'UUVF' => 5,
        'UUBU' => 6,
        'UUBB' => 7,
        'UUBF' => 8,
        'UULU' => 9,
        'UULB' => 10,
        'UULF' => 11,
        'UUFU' => 12,
        'UUFB' => 13,
        'UUFF' => 14,

        'UVUU' => 15,
        'UVUB' => 16,
        'UVUF' => 17,
        'UVVU' => 18,
        'UVVB' => 19,
        'UVVF' => 20,
        'UVBU' => 21,
        'UVBB' => 22,
        'UVBF' => 23,
        'UVLU' => 24,
        'UVLB' => 25,
        'UVLF' => 26,
        'UVFU' => 27,
        'UVFB' => 28,
        'UVFF' => 29,

        'VUUU' => 30,
        'VUUB' => 31,
        'VUUF' => 33,
        'VUVU' => 34,
        'VUVB' => 35,
        'VUVF' => 36,
        'VUBU' => 37,
        'VUBB' => 38,
        'VUBF' => 39,
        'VULU' => 40,
        'VULB' => 41,
        'VULF' => 42,
        'VUFU' => 43,
        'VUFB' => 44,
        'VUFF' => 45,

        'VVUU' => 46,
        'VVUB' => 47,
        'VVUF' => 48,
        'VVVU' => 49,
        'VVVB' => 50,
        'VVVF' => 51,
        'VVBU' => 52,
        'VVBB' => 53,
        'VVBF' => 54,
        'VVLU' => 55,
        'VVLB' => 56,
        'VVLF' => 57,
        'VVFU' => 58,
        'VVFB' => 59,
        'VVFF' => 60,

        'BUUU' => 61,
        'BUUB' => 62,
        'BUUF' => 63,
        'BUVU' => 64,
        'BUVB' => 65,
        'BUVF' => 66,
        'BUBU' => 67,
        'BUBB' => 68,
        'BUBF' => 69,
        'BULU' => 70,
        'BULB' => 71,
        'BULF' => 72,
        'BUFU' => 73,
        'BUFB' => 74,
        'BUFF' => 75,

        'BVUU' => 76,
        'BVUB' => 77,
        'BVUF' => 78,
        'BVVU' => 79,
        'BVVB' => 80,
        'BVVF' => 81,
        'BVBU' => 82,
        'BVBB' => 83,
        'BVBF' => 84,
        'BVLU' => 85,
        'BVLB' => 86,
        'BVLF' => 87,
        'BVFU' => 88,
        'BVFB' => 89,
        'BVFF' => 90,

        'FUUU' => 91,
        'FUUB' => 92,
        'FUUF' => 93,
        'FUVU' => 94,
        'FUVB' => 95,
        'FUVF' => 96,
        'FUBU' => 97,
        'FUBB' => 98,
        'FUBF' => 99,
        'FULU' => 100,
        'FULB' => 101,
        'FULF' => 102,
        'FUFU' => 103,
        'FUFB' => 104,
        'FUFF' => 105,

        'FVUU' => 106,
        'FVUB' => 107,
        'FVUF' => 108,
        'FVVU' => 109,
        'FVVB' => 110,
        'FVVF' => 111,
        'FVBU' => 112,
        'FVBB' => 113,
        'FVBF' => 114,
        'FVLU' => 115,
        'FVLB' => 116,
        'FVLF' => 117,
        'FVFU' => 118,
        'FVFB' => 119,
        'FVFF' => 120,
    }

    REVERSE_TERM_COMBINATIONS = TERM_COMBINATIONS.invert

    # Takes an instance of a Graph (Graph, QuotedGraph, ConjunctiveGraph)
    # and returns the Graphs identifier and 'type' ('U' for Graphs, 'F' for QuotedGraphs ).
    def normalizeGraph(graph)
      t = #graph.is_a?(QuotedGraph) ? "F" : term2Letter(graph.identifier)
      identifier = graph.respond_to?(:identifier) ? graph.identifier : graph
      t = term2Letter(identifier)
      [identifier, t]
    end
    
    def term2Letter(term)
      case term
      when URIRef       then "U"
      when BNode        then "B"
      when Literal      then "L"
      #when QuotedGraph  then "F"
      #when Variable     then "V"
      when Graph        then term2Letter(term.identifier)
      when nil          then "L"
      else
        raise RdfException.new("The given term (#{term}) is not an instance of any of the known types (URIRef, BNode, Literal, QuotedGraph, or Graph).  It is a #{term.class}")
      end
    end
    
    def constructGraph(term)
      GRAPH_TERM_DICT[term]
    end
    
    def type2TermCombination(member,klass,context)
      key = "#{term2Letter(member)}U#{term2Letter(klass)}#{normalizeGraph(context)[1]}"
      TERM_COMBINATIONS.fetch(key)
    rescue IndexError
       raise RdfException.new("Unable to persist classification triple: #{member.inspect}, rdf:type, #{klass.inspect}, context: #{context.inspect}, key: #{key}")
    end
    
    def statement2TermCombination(triple,context)
      key = "#{term2Letter(triple.subject)}#{term2Letter(triple.predicate)}#{term2Letter(triple.object)}#{normalizeGraph(context)[1]}"
      TERM_COMBINATIONS.fetch(key)
    rescue IndexError
      raise RdfException.new("Unable to persist triple: #{triple.inspect}, context: #{context.inspect}, key: #{key}")
    end
  end
end