from operator import itemgetter

class Substitution:

	def __init__(self,filename = "text.txt"):
         self.filename = filename
         self.getText()
         self.setAlphabet()
         self.setStandardPermutation()
         self.findInversePermutation()
         self.suggestedPermutation = {}

	def cryptAnalysis(self):
		self.countLetters()
		self.setDigrams()
		self.setTrigrams()
		self.digramCount = self.countPhrase(self.digrams)
		self.trigramCount = self.countPhrase(self.trigrams)
		self.printCount()
		self.printDigramCount()
		self.printTrigramCount()

	def getText(self):
		result_f = open(self.filename)
		self.inputText = ""	
		for line in result_f:
			self.inputText = self.inputText + line.strip("\n")
		self.inputText.upper()

	def setAlphabet(self):
		self.alphabet = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]
	
	def setStandardPermutation(self):
		self.permutation =  {'A':'D', 'B':'G','C':'T', 'D':'E', 'E':'F', 'F':'H' , 'G':'Q', 'H':'P', 'I':'U', 'J':'A', 'K':'W', 'L':'I', 'M':'Z', 'N':'C', 'O':'X', 'P':'B', 'Q':'N', 'R':'S', 'S':'O', 'T':'R', 'U':'V', 'V':'K', 'W':'J', 'X':'L', 'Y':'M', 'Z':'Y'}

	def setPermutation(self,permutation):
		if len(permutation) == 26:
			temp = self.permutation
			self.permutation = permutation
			self.findInversePermutation()
			if unlegalPerm:
				self.permutation = temp
				self.findInversePermutation()
		else:
			print "Need to have permutation of length 26"

	def findInversePermutation(self):
		self.iversePermutation = {}
		self.unlegalPerm = False
		for key,value in self.permutation:
			if(value in self.inversePermutation.keys()):
				print "Not a legal permutation"
				self.unlegalPerm = True
			else:
				self.inversePermutation[value] = key

	def setDigrams(self):
		self.digrams = []
		for i in range((len(self.inputText)-2)):
			self.digrams.append(self.inputText[i:(i+2)])

	def setTrigrams(self):
		self.trigrams = []
		for i in range((len(self.inputText)-3)):
			self.trigrams.append(self.inputText[i:(i+3)])

	# number of instances of a letter or small phrase (th, the, etc...) in a text
	def numberOfInstances(self,text, phrase):
	    instances = 0
	    length = len(text)-len(phrase) # to not end up outside array
	    for i in range(length):
	        if(text[i:(i+len(phrase))]) == phrase:
	            instances = instances + 1
	    return instances

	def countLetters(self):
		self.countTable = {}
		for letter in self.alphabet:
			self.countTable[letter] = self.numberOfInstances(self.inputText,letter)

	def countPhrase(self,phrases):
		phraseCount = {}
		for phrase in phrases:
			phraseCount[phrase] = self.numberOfInstances(self.inputText,phrase)
		return phraseCount

	# Find the howMany highest numbers in the list theList (unclear if needed)
	def highestNumbers(self,theList = {}, howMany = 0):
	    result = []
	    result.insert(0,[-1,-1])
	    for key in theList:
	    	if not (len(result) == 0):
		    	i = 0
		    	while i<len(result) and int(theList[key]) <= result[i][1]:
		    		i = i+1
		    	if(i == 0):
		    		k = 0
		    	else: 
		    		k = i-1
		    	result.insert(k,[key,theList[key]])
	    tmpResult = {}
	    for i in range(howMany):
	    	tmpResult[i] = result[i]
	    return tmpResult

	def sortedDict(self,d,l):
		table = []
		for key in d.keys():
			table.append([key,d[key]])
		table.sort(key=itemgetter(1), reverse=True)
		return table[0:l]


	# Print contents of the table sorted by keys with k rows.
	def printTable(self,table, k):
		stri = []
		n = len(table)
		for i in range(k):
			stri.append("")
		for i in range(len(table)):
			stri[(i%k)] = stri[(i%k)] + str(table[i][0]) + ": " + str(table[i][1]) + "	"	
		for i in range(k):
			print(stri[i])
		print(" ")

	def printCount(self):
		print("Letters: ")
		table1 = self.sortedDict(self.countTable,26)
		self.printTable(table1,3)

	def printDigramCount(self):
		print("Digrams: ")
		table1 = self.sortedDict(self.digramCount,10)
		self.printTable(table1,3)

	def printTrigramCount(self):
		print("Trigrams: ")
		self.printTable(self.sortedDict(self.trigramCount,10),3)

	def addletter(self,value,key):
		if not key in self.suggestedPermutation.keys():
			self.suggestedPermutation[key] = value
		else:
			print("Suggestion for this letter already made")

	def removeletter(self,key):
		del self.suggestedPermutation[key]

	def decrypt(self):
		output = ""
		for letter in self.inputText:
			if letter in self.suggestedPermutation.keys():
				output += self.suggestedPermutation[letter]
			else:
				output += "_"
		print(output)
	

	def encryptText(self):
		textString = ""
		for letter in self.inputText:
			textString = textString + self.permutation[letter]
		print(textString)

	def showcipher(self):
		print self.inputText

	def fulldecrypt(self):
		for key, value in self.permutation.items():
			if not value in self.suggestedPermutation.keys():
				self.suggestedPermutation[value] = key
		self.decrypt()


print """
Preliminary: Put a file called text.txt in the same directory
as the substitution.py file.

Usage: python -i substitution.py
   or: ./substitution.py (if you have set the executable flag)
	
The file provides the class substitution, which you can use by typing

	cs = Substitution(<filename>)
	
Where filename is name of the file containing either the message or 
ciphertext you want to work with. If no input is given, text.txt will be used.
Note that a file with the given filename input as name must sit in the same 
directory as the substitution.py file.

It contains
the following methods:

	cryptAnalysis(): Makes a count of each letter, each digram and each 
			trigram and prints the result.
	addletter(from,to): Add to the permutation we are building as suggestion
			for which permutation was used. 
	removeletter(from): Removes the the (from,to) tuple from the permutation
			we are building.
	encrypt(): Encrypts the message from <filename> with the pre set permutation.
	decrypt(): Decrypts the ciphertext from <filename> with the permutation 
			we are building, i.e. gives partial decryption if not the whole 
			permutation is set.
	showcipher(): Prints out the ciphertext in <filename>
	fulldecrypt(): Uses the inverse of the preset permutation to decrypt. 
			Note that the pre set permutation is not the one you are building 
			with addletter(from,to) and removeletter(from)
	setPermutation(permutation): Redefines the pre set permutation. Must be 
			a full valid permutation (all 26 characters) 
		               
Example
	cs = Substitution()
	cs.cryptAnalysis()
	cs.addletter(from,to)
	cs.removeletter(from)
	cs.decrypt()
	cs.encrypt()
	cs.showcipher()

"""