import os
import sys
import re
import base64

import gf256


def shareByte(secretB,k,n):
	assert n<255
	coefs=[int(secretB)]+[int(b) for b in os.urandom(k-1)]
	points=[gf256.evaluate(coefs,i) for i in range(1,n+1)]
	return points


def generateRaw(secret,k,n):
	shares=[shareByte(b,k,n) for b in secret]
	return [(i+1, bytes([s[i] for s in shares])) for i in range(n)]


def reconstructRaw(*shares):
	secretLen=len(shares[0][1])
	res=[None]*secretLen
	for i in range(secretLen):
		bs=[(x,s[i]) for (x,s) in shares]
		res[i]=(gf256.getConstantCoef(*bs))
	return bytes(res)


def generate(secret,k,n,encoding="b32"):
	if isinstance(secret,str):
		secret=secret.encode("utf-8")
	shares=generateRaw(secret,k,n)
	return [encode(s,encoding) for s in shares]


def reconstruct(*shares,encoding="",raw=False):
	if not encoding:
		encoding=detectEncoding(shares)

	bs=reconstructRaw(decode(s,encoding) for s in shares)
	return bs if raw else bs.decode(encoding="utf-8")


def encode(share,encoding="b32"):
	if encoding=="hex": f=base64.b16encode
	elif encoding=="b32": f=base64.b32encode
	else: f=base64.b64encode
	return ["{0}.{1}".format(i,f(bs).decode("utf8")) for (i,bs) in share]


def decode(share,encoding="b32"):
	(i,_,shareStr)=share.partition(".")
	if not shareStr:
		raise ValueError("bad share format")
	i=int(i)
	if encoding=="hex": f=base64.b16decode
	elif encoding=="b32": f=base64.b32decode
	else: f=base64.b32decode
	shareBytes=f(shareStr)
	return (i,shareBytes)


def detectEncoding(shares):
	classes=[
		(re.compile(r"\d+\.[0-9a-f]+=*"), "hex"),
		(re.compile(r"\d+\.[A-Z2-7]+=*"), "b32"),
		(re.compile(r"\d+\.[A-Za-z0-9+/]+=*"), "b64")
	]
	for (regexp, res) in classes:
		if all(regexp.fullmatch(share) for share in shares):
			return res
	raise ValueError("no expected encoding detected")


if __name__=="__main__":
	secret=sys.argv[1].encode("utf8")
	k=int(sys.argv[2])
	n=int(sys.argv[3])
	output=sys.argv[4] if len(sys.argv)>4 else "raw"
	for share in generate(secret,k,n,output):
		print(share)