Add NFA class

Start converting units to NFAs

lib/imbecile/regex/nfa.rb

@@ -0,0 +1,40 @@
+module Imbecile
+  class Regex
+
+    class NFA
+
+      class State
+
+        def initialize
+          @transitions = []
+        end
+
+        def add_transition(code_point, destination_state)
+          @transitions << [code_point, destination_state]
+        end
+
+      end
+
+      attr_accessor :start_state
+
+      attr_accessor :end_state
+
+      def initialize
+        @start_state = State.new
+        @end_state = State.new
+      end
+
+      class << self
+
+        def empty
+          nfa = NFA.new
+          nfa.end_state = nfa.start_state
+          nfa
+        end
+
+      end
+
+    end
+
+  end
+end

lib/imbecile/regex/parser.rb

@@ -14,6 +14,18 @@ module Imbecile
         def method_missing(*args)
           @units.__send__(*args)
         end
+        def to_nfa
+          if @units.empty?
+            NFA.empty
+          else
+            @units.map do |unit|
+              unit.to_nfa
+            end.reduce do |result, nfa|
+              result.end_state.add_transition(nil, nfa.start_state)
+              result
+            end
+          end
+        end
       end
 
       class AlternatesUnit < Unit
@@ -47,6 +59,23 @@ module Imbecile
             @alternates[-1] = new_unit
           end
         end
+        def to_nfa
+          if @alternates.size == 0
+            NFA.empty
+          elsif @alternates.size == 1
+            @alternates[0].to_nfa
+          else
+            nfa = NFA.new
+            alternate_nfas = @alternates.map do |alternate|
+              alternate.to_nfa
+            end
+            alternate_nfas.each do |alternate_nfa|
+              nfa.start_state.add_transition(nil, alternate_nfa.start_state)
+              alternate_nfa.end_state.add_transition(nil, nfa.end_state)
+            end
+            nfa
+          end
+        end
       end
 
       class CharacterUnit < Unit