#!/usr/bin/env python3

"""
Markov chain simulation of words or characters.
"""

class Markov:
 def __init__(self, histsize, choice):
 self.histsize = histsize
 self.choice = choice
 self.trans = {}

 def add(self, state, next):
 self.trans.setdefault(state, []).append(next)

 def put(self, seq):
 n = self.histsize
 add = self.add
 add(None, seq[:0])
 for i in range(len(seq)):
 add(seq[max(0, i-n):i], seq[i:i+1])
 add(seq[len(seq)-n:], None)

 def get(self):
 choice = self.choice
 trans = self.trans
 n = self.histsize
 seq = choice(trans[None])
 while True:
 subseq = seq[max(0, len(seq)-n):]
 options = trans[subseq]
 next = choice(options)
 if not next:
 break
 seq += next
 return seq


def test():
 import sys, random, getopt
 args = sys.argv[1:]
 try:
 opts, args = getopt.getopt(args, '0123456789cdwq')
 except getopt.error:
 print('Usage: %s [-#] [-cddqw] [file] ...' % sys.argv[0])
 print('Options:')
 print('-#: 1-digit history size (default 2)')
 print('-c: characters (default)')
 print('-w: words')
 print('-d: more debugging output')
 print('-q: no debugging output')
 print('Input files (default stdin) are split in paragraphs')
 print('separated blank lines and each paragraph is split')
 print('in words by whitespace, then reconcatenated with')
 print('exactly one space separating words.')
 print('Output consists of paragraphs separated by blank')
 print('lines, where lines are no longer than 72 characters.')
 sys.exit(2)
 histsize = 2
 do_words = False
 debug = 1
 for o, a in opts:
 if '-0' <= o <= '-9': histsize = int(o[1:])
 if o == '-c': do_words = False
 if o == '-d': debug += 1
 if o == '-q': debug = 0
 if o == '-w': do_words = True
 if not args:
 args = ['-']

 m = Markov(histsize, random.choice)
 try:
 for filename in args:
 if filename == '-':
 f = sys.stdin
 if f.isatty():
 print('Sorry, need stdin from file')
 continue
 else:
 f = open(filename, 'r')
 if debug: print('processing', filename, '...')
 text = f.read()
 f.close()
 paralist = text.split('\n\n')
 for para in paralist:
 if debug > 1: print('feeding ...')
 words = para.split()
 if words:
 if do_words:
 data = tuple(words)
 else:
 data = ' '.join(words)
 m.put(data)
 except KeyboardInterrupt:
 print('Interrupted -- continue with data read so far')
 if not m.trans:
 print('No valid input files')
 return
 if debug: print('done.')

 if debug > 1:
 for key in m.trans.keys():
 if key is None or len(key) < histsize:
 print(repr(key), m.trans[key])
 if histsize == 0: print(repr(''), m.trans[''])
 print()
 while True:
 data = m.get()
 if do_words:
 words = data
 else:
 words = data.split()
 n = 0
 limit = 72
 for w in words:
 if n + len(w) > limit:
 print()
 n = 0
 print(w, end=' ')
 n += len(w) + 1
 print()
 print()

if __name__ == "__main__":
 test()