import sys

from regex import Literal, Concatenation, Alternation, Star, lit
from nfa import NFA, prettyprint
from parse_regex import parse, ParseError

def to_nfa(regex):
	def new_state():
		nonlocal state_name_counter, transitions

		state_name = state_name_counter
		state_name_counter += 1

		transitions[state_name] = {}

		return state_name

	def worker(node):
		nonlocal transitions

		if type(node) == Literal:
			#            text
			# (start) ---------> (end)
			start_state = new_state()
			end_state = new_state()

			transitions[start_state][end_state] = lit(node.text)

			return (start_state, end_state)

		elif type(node) == Concatenation:
			# (start) → […] → […] → […]
			start_state = new_state()

			prev_state = start_state
			for element in node.elements:
				inner_start, inner_end = worker(element)

				# (prev) → (inner_start) → […]
				transitions[prev_state][inner_start] = lit('')

				# Link next element straight to the inner end
				# state
				prev_state = inner_end

			return (start_state, prev_state)

		elif type(node) == Alternation:
			#           +-> […] --+
			#           |         |
			# (start) --+-> […] --+-> (end)
			#           |         |
			#           +-> […] --+
			start_state = new_state()
			end_state = new_state()

			for element in node.elements:
				inner_start, inner_end = worker(element)

				# (start) → (inner_start) → […]
				transitions[start_state][inner_start] = lit('')

				# […] → (inner_end) → (end)
				transitions[inner_end][end_state] = lit('')

			return (start_state, end_state)

		elif type(node) == Star:
			#  +- […] <-+
			#  |        |
			#  v        |
			# (start) --+--> (end)
			start_state = new_state()
			end_state = new_state()

			inner_start, inner_end = worker(node.element)

			# (start) → (inner_start) → […]
			transitions[start_state][inner_start] = lit('')

			# […] → (inner_end) → (start)
			transitions[inner_end][start_state] = lit('')

			# (start) → (end)
			transitions[start_state][end_state] = lit('')

			return (start_state, end_state)

		else:
			raise ValueError('node has to be Literal, Concatenation, Alternation, or Star')

	state_name_counter = 0
	transitions = {}

	start_state, end_state = worker(regex)

	return NFA(start_state, [end_state], transitions)

def main():
	try:
		regex = parse(input('regex> '))

	except ParseError as err:
		print('%s: Error: %s' % (sys.argv[0], str(err)), file=sys.stderr)

	else:
		nfa = to_nfa(regex)

		prettyprint(nfa)

if __name__ == '__main__':
	main()