class Journey::NFA::Visitor

# File lib/journey/nfa/builder.rb, line 7
def initialize tt
  @tt = tt
  @i  = -1
end

# File lib/journey/nfa/builder.rb, line 50
def terminal node
  from_i = @i += 1 # new state
  to_i   = @i += 1 # new state

  @tt[from_i, to_i] = node
  @tt.accepting = to_i
  @tt.add_memo to_i, node.memo

  [from_i, to_i]
end

# File lib/journey/nfa/builder.rb, line 12
def visit_CAT node
  left  = visit node.left
  right = visit node.right

  @tt.merge left.last, right.first

  [left.first, right.last]
end

# File lib/journey/nfa/builder.rb, line 21
def visit_GROUP node
  from  = @i += 1
  left  = visit node.left
  to    = @i += 1

  @tt.accepting = to

  @tt[from, left.first] = nil
  @tt[left.last, to] = nil
  @tt[from, to] = nil

  [from, to]
end

# File lib/journey/nfa/builder.rb, line 35
def visit_OR node
  from  = @i += 1
  children = node.children.map { |c| visit c }
  to    = @i += 1

  children.each do |child|
    @tt[from, child.first]  = nil
    @tt[child.last, to]     = nil
  end

  @tt.accepting = to

  [from, to]
end