"""Implements and prints out a markov chain"""

import random

def main():
	file1 = input("Enter file name >>> ")
	firstWords = []
	dict1 = {} #A dictionary storing each word and a list of all words that can follow it
	flag = 1
	count = 0

	#Open the file named file1 in reading mode, and call the open file descriptor f1
	with open(file1, "r") as f1:
		#Loop through the open file line by line
		for line in f1:
			#Split each line into a list
			tempList = line.split()

			#If that line wasn't empty, add its first word to the list of first words
			if len(tempList) > 0:
				firstWords.append(tempList[0])

			#Walk through the entire line
			for i in range(0, len(tempList)):
				#if the word in the line isn't in the dictionary, add it to the dictionary and give its value to be a new list
				if tempList[i] not in dict1:
					dict1[tempList[i]] = []
				#otherwise, so long as it isn't punctuation, add the next word to the list of that dictionary entry
				if tempList[i] != '.' and tempList[i] != ',' and i < len(tempList) - 1:
					dict1[tempList[i]].append(tempList[i + 1])

	#Choose any word from the file that was the start of a sentance
	string = random.choice(firstWords)

	#While the current word as a non-empty list as its value (basically, there's some word that can follow it) keep looping
	#And for simplicity, just stop if we hit 100 in a chain. No need to go forever.
	while flag == 1 and count < 100:
		count = count + 1
		print(string, end=' ')

		#Change from the current string into one of the possible words that could follow it, and continue with the loop
		if len(dict1[string]) != 0:
			string = random.choice(dict1[string])
		#The current word doesn't have anything that can follow it. So we're at the end of the chain.
		elif len(dict1[string]) == 0:
			flag = 0
	#Put a newline after the chain is done for pretty-print reasons
	print('')

if __name__ == "__main__":
    main()