#!/usr/bin/env python3
# -*- coding: utf-8 -*-

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.


import random
import re
import sys


class Sentence_generator:
	
	punctuation_re = re.compile(' ([^ ]+)$')
	variable_re = re.compile(r'\$([^_\$:]+)')
	
	def __init__(self, non_terminals, terminals, unique=False, verbosity=0, err_file=sys.stderr):
		self.non_terminals = non_terminals
		self.terminals = terminals
		self.unique = unique
		self.verbosity = verbosity
		self.err_file = err_file
		if self.unique:
			self.cache = set()
	
	def err(self, *args, **kwargs):
		if kwargs.pop('verbosity', 0) <= self.verbosity:
			print(kwargs.pop('align_char', ' ')*kwargs.pop('align_level', 0), end='', file=self.err_file)
			print(*args, file=sys.stderr, **kwargs)
	
	def compile_symbols(self, symbols, variables, level):
		
		def sub(match):
			a = match.group(1)
			if a not in variables:
				variables[a] = random.choice(self.non_terminals[a][0])
				self.err('choosing', a+'='+variables[a], align_level=level*2, verbosity=2)
			return variables[a]
		
		s = [self.variable_re.sub(sub, symbol) for symbol in symbols]
		
		return s
	
	def generate_from_symbols(self, symbols, variables=None, r=None, level=0):
		if variables is None:
			variables = {}
		if r is None:
			r = []
		
		symbols = self.compile_symbols(symbols, variables, level)
		
		for symbol in symbols:
			if ':' in symbol:
				symbol, attributes = symbol.split(':')
				attributes = attributes.split(',')
				
				if symbol not in self.non_terminals:
					r.append(symbol)
					continue
				
				v = {}
				for a in attributes:
					if a not in variables:
						variables[a] = random.choice(self.non_terminals[a][0])
						self.err('choosing', a+'='+variables[a], 'for', symbol, align_level=level*2, verbosity=2)
					v[a] = variables[a]
				
				c = random.choice(self.non_terminals[symbol])
				self.err(symbol, '→', ' '.join(c), align_level=level*2, verbosity=1)
				self.generate_from_symbols(c, v, r, level+1)
			
			elif symbol in self.non_terminals:
				c = random.choice(self.non_terminals[symbol])
				self.err(symbol, '→', ' '.join(c), align_level=level*2, verbosity=1)
				self.generate_from_symbols(c, None, r, level+1)
			
			elif symbol in self.terminals:
				r.append(random.choice(self.terminals[symbol]))
				self.err(symbol, '→', r[-1], align_level=level*2, verbosity=1)
			
			else:
				r.append(symbol)
			
		return r
	
	def generate_sentence(self):
		r = self.generate_from_symbols(['_Sentence'])
		r[0] = r[0][0].upper() + r[0][1:]
		r = ' '.join(r)
		r = self.punctuation_re.sub(r'\1', r)
		for a, b in self.terminals['_Replacements']:
			r = r.replace(a, b)
		return r