#   Eos - Verifiable elections
#   Copyright © 2017-18  RunasSudo (Yingtong Li)
#
#   This program is free software: you can redistribute it and/or modify
#   it under the terms of the GNU Affero 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 Affero General Public License for more details.
#
#   You should have received a copy of the GNU Affero General Public License
#   along with this program.  If not, see <http://www.gnu.org/licenses/>.

from eos.core.tests import *

from eos.core.objects import *
from eos.core.bigint import *
from eos.core.hashing import *
from eos.psr.bitstream import *
from eos.psr.crypto import *
from eos.psr.election import *
from eos.psr.mixnet import *
from eos.psr.secretsharing import *
from eos.psr.workflow import *

from eos.core.objects import __pragma__

class GroupValidityTestCase(EosTestCase):
	# HAC 4.24
	def miller_rabin_test(self, n, t):
		# Write n - 1 = 2^s * r such that r is odd
		s = 0
		r = n - ONE
		while r % TWO == ZERO:
			r = r // TWO
			s = s + 1
		for _ in range(t):
			a = BigInt.noncrypto_random(TWO, n - TWO)
			y = pow(a, r, n)
			if y != ONE and y != (n - ONE):
				j = 1
				while j <= s - 1 and y != (n - ONE):
					y = pow(y, TWO, n)
					if y == ONE:
						return False
					j = j + 1
				if y != (n - ONE):
					return False
		return True
	
	@py_only
	def test_miller_rabin(self):
		self.assertTrue(self.miller_rabin_test(BigInt('7'), 30))
		self.assertFalse(self.miller_rabin_test(BigInt('35'), 30))
		self.assertTrue(self.miller_rabin_test(BigInt('15485863'), 30))
		self.assertFalse(self.miller_rabin_test(BigInt('502560280658509'), 30)) # 15485863 * 32452843
	
	@py_only
	def test_default_group_validity(self):
		self.assertTrue(self.miller_rabin_test(DEFAULT_GROUP.p, 30))
		self.assertTrue(self.miller_rabin_test(DEFAULT_GROUP.q, 30))
		# Since the subgroup G_q is of prime order q, g != 1 is a generator

class EGTestCase(EosTestCase):
	def test_eg(self):
		pt = DEFAULT_GROUP.random_Zq_element()
		sk = EGPrivateKey.generate()
		ct = sk.public_key.encrypt(pt)
		proved_pt = sk.decrypt_and_prove(ct)
		
		m = proved_pt.message
		self.assertEqualJSON(pt, m)
		
		self.assertTrue(proved_pt.is_proof_valid())

class SEGTestCase(EosTestCase):
	def test_eg(self):
		pt = DEFAULT_GROUP.random_Zq_element()
		sk = SEGPrivateKey.generate()
		ct = sk.public_key.encrypt(pt)
		self.assertTrue(ct.is_signature_valid())
		m = sk.decrypt(ct)
		self.assertEqualJSON(pt, m)
		
		ct2, _ = ct.reencrypt()
		m2 = sk.decrypt(ct2)
		self.assertEqualJSON(pt, m2)

class BitStreamTestCase(EosTestCase):
	def test_bitstream(self):
		bs = BitStream(BigInt('100101011011', 2))
		self.assertEqual(bs.read(4), 0b1001)
		self.assertEqual(bs.read(4), 0b0101)
		self.assertEqual(bs.read(4), 0b1011)
		bs = BitStream()
		bs.write(BigInt('100101011011', 2))
		bs.seek(0)
		self.assertEqual(bs.read(4), 0b1001)
		self.assertEqual(bs.read(4), 0b0101)
		self.assertEqual(bs.read(4), 0b1011)
		bs.seek(4)
		bs.write(BigInt('11', 2))
		bs.seek(0)
		self.assertEqual(bs.read(4), 0b1001)
		self.assertEqual(bs.read(4), 0b1101)
		self.assertEqual(bs.read(4), 0b0110)
		self.assertEqual(bs.read(2), 0b11)
	
	def test_bitstream_map(self):
		bs = BitStream(BigInt('100101011011', 2))
		result = bs.map(lambda x: x, 4)
		expect = [0b1001, 0b0101, 0b1011]
		for i in range(len(expect)):
			self.assertEqual(result[i], expect[i])
	
	def test_strings(self):
		bs = BitStream()
		bs.write_string('Hello World!')
		bs.seek(0)
		self.assertEqual(bs.read(32), len('Hello World!'))
		bs.seek(0)
		self.assertEqual(bs.read_string(), 'Hello World!')

class BlockEGTestCase(EosTestCase):
	@classmethod
	def setUpClass(cls):
		class Person(TopLevelObject):
			name = StringField()
			address = StringField(default=None)
			def say_hi(self):
				return 'Hello! My name is ' + self.name
		
		cls.Person = Person
		
		#cls.test_group = CyclicGroup(p=BigInt('11'), g=BigInt('2'))
		cls.test_group = CyclicGroup(p=BigInt('283'), g=BigInt('60'))
		cls.sk = EGPrivateKey.generate(cls.test_group)
	
	def test_basic(self):
		pt = BigInt('11010010011111010100101', 2)
		ct = BitStream(pt).multiple_of(self.sk.public_key.nbits()).map(self.sk.public_key.encrypt, self.sk.public_key.nbits())
		for ct_block in ct:
			self.assertTrue(ct_block.gamma < self.test_group.p)
			self.assertTrue(ct_block.delta < self.test_group.p)
		m = BitStream.unmap(ct, self.sk.decrypt, self.sk.public_key.nbits()).read()
		self.assertEqualJSON(pt, m)
	
	def test_object(self):
		obj = self.Person(name='John Smith')
		
		ct = BlockEncryptedAnswer.encrypt(self.sk.public_key, obj)
		_, m = ct.decrypt(self.sk)
		self.assertEqualJSON(obj, m)
		
		# Force another block
		ct2 = BlockEncryptedAnswer.encrypt(self.sk.public_key, obj, (len(ct.blocks) * self.sk.public_key.nbits()) + 1)
		self.assertEqual(len(ct2.blocks), len(ct.blocks) + 1)
		_, m = ct2.decrypt(self.sk)
		self.assertEqualJSON(obj, m)

class MixnetTestCase(EosTestCase):
	@py_only
	def test_mixnet(self):
		# Generate key
		sk = SEGPrivateKey.generate()
		
		# Generate plaintexts
		pts = []
		for _ in range(4):
			pts.append(sk.public_key.group.random_Zq_element())
		
		# Encrypt plaintexts
		answers = []
		for pt in pts:
			bs = BitStream(pt)
			bs.multiple_of(sk.public_key.nbits())
			ct = bs.map(sk.public_key.encrypt, sk.public_key.nbits())
			answers.append(BlockEncryptedAnswer(blocks=ct))
		
		def do_mixnet(mix_order):
			# Set up mixnet
			mixnet = RPCMixnet(mix_order=mix_order)
			
			# Mix answers
			shuffled_answers, commitments = mixnet.shuffle(answers)
			
			# Decrypt shuffle
			msgs = []
			for shuffled_answer in shuffled_answers:
				bs = BitStream.unmap(shuffled_answer.blocks, sk.decrypt, sk.public_key.nbits())
				m = bs.read()
				msgs.append(m)
			
			# Check decryption
			self.assertEqual(set(int(x) for x in pts), set(int(x) for x in msgs))
			
			# Check commitments
			def verify_shuffle(idx_left, idx_right, reencs):
				claimed_blocks = shuffled_answers[idx_right].blocks
				for j in range(len(answers[idx_left].blocks)):
					reencrypted_block, _ = answers[idx_left].blocks[j].reencrypt(reencs[j])
					self.assertEqual(claimed_blocks[j].gamma, reencrypted_block.gamma)
					self.assertEqual(claimed_blocks[j].delta, reencrypted_block.delta)
			
			for i in range(len(pts)):
				val_obj = mixnet.challenge(i)
				self.assertEqual(commitments[i], SHA256().update_obj(val_obj).hash_as_bigint())
				
				if mixnet.is_left:
					verify_shuffle(val_obj.challenge_index, val_obj.response_index, val_obj.reenc)
				else:
					verify_shuffle(val_obj.response_index, val_obj.challenge_index, val_obj.reenc)
		
		# NB: This isn't doing it in sequence, it's just testing a left mixnet and a right mixnet respectively
		do_mixnet(0)
		do_mixnet(1)

class ElectionTestCase(EosTestCase):
	@classmethod
	def setUpClass(cls):
		cls.db_connect_and_reset()
	
	def do_task_assert(self, election, task, next_task):
		self.assertEqual(election.workflow.get_task(task).status, WorkflowTaskStatus.READY)
		if next_task is not None:
			self.assertEqual(election.workflow.get_task(next_task).status, WorkflowTaskStatus.NOT_READY)
		election.workflow.get_task(task).enter()
		self.assertEqual(election.workflow.get_task(task).status, WorkflowTaskStatus.EXITED)
		if next_task is not None:
			self.assertEqual(election.workflow.get_task(next_task).status, WorkflowTaskStatus.READY)
	
	@py_only
	def test_run_election(self):
		# Set up election
		election = PSRElection()
		election.workflow = PSRWorkflow()
		
		# Set election details
		election.name = 'Test Election'
		
		for i in range(3):
			voter = Voter(name=['Alice', 'Bob', 'Charlie'][i])
			election.voters.append(voter)
		
		for _ in range(3):
			mixing_trustee = InternalMixingTrustee()
			election.mixing_trustees.append(mixing_trustee)
		
		election.sk = EGPrivateKey.generate()
		election.public_key = election.sk.public_key
		
		question = ApprovalQuestion(prompt='President', choices=[Choice(name='John Smith'), Choice(name='Joe Bloggs'), Choice(name='John Q. Public')])
		election.questions.append(question)
		
		question = ApprovalQuestion(prompt='Chairman', choices=[Choice(name='John Doe'), Choice(name='Andrew Citizen')])
		election.questions.append(question)
		
		election.save()
		
		# Freeze election
		self.do_task_assert(election, 'eos.base.workflow.TaskConfigureElection', 'eos.base.workflow.TaskOpenVoting')
		
		election_hash = SHA256().update_obj(election).hash_as_b64() # Keep track of the hash and make sure it doesn't change
		
		# Open voting
		self.do_task_assert(election, 'eos.base.workflow.TaskOpenVoting', 'eos.base.workflow.TaskCloseVoting')
		election.save()
		
		# Cast ballots
		VOTES = [[[0], [0]], [[0, 1], [1]], [[2], [0]]]
		
		for i in range(3):
			ballot = Ballot(election_id=election._id, election_hash=election_hash)
			for j in range(2):
				answer = ApprovalAnswer(choices=VOTES[i][j])
				encrypted_answer = BlockEncryptedAnswer.encrypt(election.sk.public_key, answer)
				ballot.encrypted_answers.append(encrypted_answer)
			vote = Vote(voter_id=election.voters[i]._id, ballot=ballot, cast_at=DateTimeField.now())
			vote.save()
		
		#election.save()
		
		# Close voting
		self.do_task_assert(election, 'eos.base.workflow.TaskCloseVoting', 'eos.psr.workflow.TaskMixVotes')
		election.save()
		
		# Mix votes
		self.do_task_assert(election, 'eos.psr.workflow.TaskMixVotes', 'eos.psr.workflow.TaskProveMixes')
		election.save()
		
		# Prove mixes
		self.do_task_assert(election, 'eos.psr.workflow.TaskProveMixes', 'eos.base.workflow.TaskDecryptVotes')
		election.save()
		
		# Verify mixes
		for i in range(len(election.questions)):
			for j in range(len(election.mixing_trustees)):
				election.mixing_trustees[j].verify(i)
		
		# Decrypt votes, for realsies
		self.do_task_assert(election, 'eos.base.workflow.TaskDecryptVotes', 'eos.base.workflow.TaskReleaseResults')
		election.save()
		
		# Check result
		RESULTS = [[EosList(voter[i]) for voter in VOTES] for i in range(len(election.questions))]
		for i in range(len(RESULTS)):
			votes1 = RESULTS[i]
			votes2 = [x.choices for x in election.results[i].answers]
			self.assertEqual(sorted(votes1), sorted(votes2))
		
		# Release result
		self.do_task_assert(election, 'eos.base.workflow.TaskReleaseResults', None)
		election.save()
		
		# Check the hash hasn't changed during that
		self.assertEqual(SHA256().update_obj(election).hash_as_b64(), election_hash)
		
		# Check the election verifies
		election.verify()

class PVSSTestCase(EosTestCase):
	@py_only
	def test_basic(self):
		return
		setup = PedersenVSSSetup()
		setup.group = DEFAULT_GROUP
		setup.threshold = 3 # 3 of 5
		
		for _ in range(5):
			participant = PedersenVSSParticipant(setup)
			participant.sk = EGPrivateKey.generate()
			participant.pk = participant.sk.public_key
			setup.participants.append(participant)
		
		# Step 1
		
		for participant in setup.participants:
			participant.commit_pk_share()
		
		# IRL: Send hi=F[0] commitments around
		
		# Send shares around
		for participant in setup.participants:
			for j in range(len(setup.participants)):
				other = setup.participants[j]
				share = participant.get_share_for(j)
				#share_dec = other.sk.decrypt(share)
				share_dec = BitStream.unmap(share, other.sk.decrypt, other.sk.public_key.nbits()).read_bigint()
				other.shares_received.append(share_dec)
		
		# Step 2
		
		# IRL: Decommit hi=F[0], send F around
		
		# Verify shares
		for i in range(len(setup.participants)):
			participant = setup.participants[i]
			for j in range(len(setup.participants)):
				other = setup.participants[j]
				
				# Verify share received by other from participant
				share_dec = other.shares_received[i]
				g_share_dec_expected = ONE
				for k in range(setup.threshold):
					g_share_dec_expected = (g_share_dec_expected * pow(participant.F[k], pow(j + 1, k), setup.group.p)) % setup.group.p
				if pow(setup.group.g, share_dec, setup.group.p) != g_share_dec_expected:
					raise Exception('Share not consistent with commitments')
		
		# Compute threshold public key
		pk = setup.compute_public_key()
		
		# Compute secret key shares
		for participant in setup.participants:
			participant.compute_secret_key()
		
		# Encrypt data
		
		pt = pk.group.random_Zq_element()
		ct = pk.encrypt(pt)
		
		# Decrypt data
		
		decryption_shares = []
		
		# Pick any threshold
		__pragma__('skip')
		import random
		__pragma__('noskip')
		threshold_participants = list(range(len(setup.participants)))
		random.shuffle(threshold_participants)
		threshold_participants = threshold_participants[:setup.threshold]
		
		for i in setup.threshold:
			share = setup.participants[i].threshold_sk.decrypt(ct)
			decryption_shares.append((i, share))
		
		m = setup.combine_decryptions(decryption_shares)
		self.assertEqualJSON(pt, m)