import base64
import math
import os
import RNS
import time
import atexit
from .vendor import umsgpack as umsgpack
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.serialization import load_der_public_key
from cryptography.hazmat.primitives.serialization import load_der_private_key
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.primitives.asymmetric import padding

class Identity:
   #KEYSIZE     = 1536
	KEYSIZE     = 1024
	DERKEYSIZE  = KEYSIZE+272

	# Non-configurable constants
	PADDINGSIZE = 336		# In bits
	HASHLENGTH  = 256		# In bits
	SIGLENGTH   = KEYSIZE

	ENCRYPT_CHUNKSIZE = (KEYSIZE-PADDINGSIZE)//8
	DECRYPT_CHUNKSIZE = KEYSIZE//8

	TRUNCATED_HASHLENGTH = 80 # In bits

	# Storage
	known_destinations = {}

	@staticmethod
	def remember(packet_hash, destination_hash, public_key, app_data = None):
		RNS.log("Remembering "+RNS.prettyhexrep(destination_hash), RNS.LOG_VERBOSE)
		Identity.known_destinations[destination_hash] = [time.time(), packet_hash, public_key, app_data]


	@staticmethod
	def recall(destination_hash):
		RNS.log("Searching for "+RNS.prettyhexrep(destination_hash)+"...", RNS.LOG_EXTREME)
		if destination_hash in Identity.known_destinations:
			identity_data = Identity.known_destinations[destination_hash]
			identity = Identity(public_only=True)
			identity.loadPublicKey(identity_data[2])
			RNS.log("Found "+RNS.prettyhexrep(destination_hash)+" in known destinations", RNS.LOG_EXTREME)
			return identity
		else:
			RNS.log("Could not find "+RNS.prettyhexrep(destination_hash)+" in known destinations", RNS.LOG_EXTREME)
			return None

	@staticmethod
	def saveKnownDestinations():
		RNS.log("Saving known destinations to storage...", RNS.LOG_VERBOSE)
		file = open(RNS.Reticulum.storagepath+"/known_destinations","wb")
		umsgpack.dump(Identity.known_destinations, file)
		file.close()
		RNS.log("Done saving known destinations to storage", RNS.LOG_VERBOSE)

	@staticmethod
	def loadKnownDestinations():
		if os.path.isfile(RNS.Reticulum.storagepath+"/known_destinations"):
			try:
				file = open(RNS.Reticulum.storagepath+"/known_destinations","rb")
				Identity.known_destinations = umsgpack.load(file)
				file.close()
				RNS.log("Loaded "+str(len(Identity.known_destinations))+" known destination from storage", RNS.LOG_VERBOSE)
			except:
				RNS.log("Error loading known destinations from disk, file will be recreated on exit", RNS.LOG_ERROR)
		else:
			RNS.log("Destinations file does not exist, so no known destinations loaded", RNS.LOG_VERBOSE)

	@staticmethod
	def fullHash(data):
		digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
		digest.update(data)

		return digest.finalize()

	@staticmethod
	def truncatedHash(data):
		digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
		digest.update(data)

		return digest.finalize()[:(Identity.TRUNCATED_HASHLENGTH//8)]

	@staticmethod
	def getRandomHash():
		return Identity.truncatedHash(os.urandom(10))

	@staticmethod
	def validateAnnounce(packet):
		if packet.packet_type == RNS.Packet.ANNOUNCE:
			RNS.log("Validating announce from "+RNS.prettyhexrep(packet.destination_hash), RNS.LOG_DEBUG)
			destination_hash = packet.destination_hash
			public_key = packet.data[10:Identity.DERKEYSIZE//8+10]
			random_hash = packet.data[Identity.DERKEYSIZE//8+10:Identity.DERKEYSIZE//8+20]
			signature = packet.data[Identity.DERKEYSIZE//8+20:Identity.DERKEYSIZE//8+20+Identity.KEYSIZE//8]
			app_data = b""
			if len(packet.data) > Identity.DERKEYSIZE//8+20+Identity.KEYSIZE//8:
				app_data = packet.data[Identity.DERKEYSIZE//8+20+Identity.KEYSIZE//8:]

			signed_data = destination_hash+public_key+random_hash+app_data

			announced_identity = Identity(public_only=True)
			announced_identity.loadPublicKey(public_key)

			if announced_identity.pub != None and announced_identity.validate(signature, signed_data):
				RNS.Identity.remember(packet.getHash(), destination_hash, public_key)
				RNS.log("Stored valid announce from "+RNS.prettyhexrep(destination_hash), RNS.LOG_INFO)
				del announced_identity
				return True
			else:
				RNS.log("Received invalid announce", RNS.LOG_DEBUG)
				del announced_identity
				return False

	@staticmethod
	def exitHandler():
		Identity.saveKnownDestinations()


	@staticmethod
	def from_file(path):
		identity = Identity(public_only=True)
		if identity.load(path):
			return identity
		else:
			return None


	def __init__(self,public_only=False):
		# Initialize keys to none
		self.prv = None
		self.pub = None
		self.prv_bytes = None
		self.pub_bytes = None
		self.hash = None
		self.hexhash = None

		if not public_only:
			self.createKeys()

	def createKeys(self):
		self.prv = rsa.generate_private_key(
			public_exponent=65337,
			key_size=Identity.KEYSIZE,
			backend=default_backend()
		)
		self.prv_bytes = self.prv.private_bytes(
			encoding=serialization.Encoding.DER,
			format=serialization.PrivateFormat.PKCS8,
			encryption_algorithm=serialization.NoEncryption()
		)
		self.pub = self.prv.public_key()
		self.pub_bytes = self.pub.public_bytes(
			encoding=serialization.Encoding.DER,
			format=serialization.PublicFormat.SubjectPublicKeyInfo
		)

		self.updateHashes()

		RNS.log("Identity keys created for "+RNS.prettyhexrep(self.hash), RNS.LOG_VERBOSE)

	def getPrivateKey(self):
		return self.prv_bytes

	def getPublicKey(self):
		return self.pub_bytes

	def loadPrivateKey(self, prv_bytes):
		try:
			self.prv_bytes = prv_bytes
			self.prv = serialization.load_der_private_key(
				self.prv_bytes,
				password=None,
				backend=default_backend()
			)
			self.pub = self.prv.public_key()
			self.pub_bytes = self.pub.public_bytes(
				encoding=serialization.Encoding.DER,
				format=serialization.PublicFormat.SubjectPublicKeyInfo
			)
			self.updateHashes()

			return True

		except Exception as e:
			RNS.log("Failed to load identity key", RNS.LOG_ERROR)
			RNS.log("The contained exception was: "+str(e))
			return False

	def loadPublicKey(self, key):
		try:
			self.pub_bytes = key
			self.pub = load_der_public_key(self.pub_bytes, backend=default_backend())
			self.updateHashes()
		except Exception as e:
			RNS.log("Error while loading public key, the contained exception was: "+str(e), RNS.LOG_ERROR)

	def updateHashes(self):
		self.hash = Identity.truncatedHash(self.pub_bytes)
		self.hexhash = self.hash.hex()

	def save(self, path):
		try:
			with open(path, "wb") as key_file:
				key_file.write(self.prv_bytes)
				return True
			return False
		except Exception as e:
			RNS.log("Error while saving identity to "+str(path), RNS.LOG_ERROR)
			RNS.log("The contained exception was: "+str(e))

	def load(self, path):
		try:
			with open(path, "rb") as key_file:
				prv_bytes = key_file.read()
				return self.loadPrivateKey(prv_bytes)
			return False
		except Exception as e:
			RNS.log("Error while loading identity from "+str(path), RNS.LOG_ERROR)
			RNS.log("The contained exception was: "+str(e))

	def encrypt(self, plaintext):
		if self.pub != None:
			chunksize = Identity.ENCRYPT_CHUNKSIZE
			chunks = int(math.ceil(len(plaintext)/(float(chunksize))))

			ciphertext = b"";
			for chunk in range(chunks):
				start = chunk*chunksize
				end = (chunk+1)*chunksize
				if (chunk+1)*chunksize > len(plaintext):
					end = len(plaintext)
				
				ciphertext += self.pub.encrypt(
					plaintext[start:end],
					padding.OAEP(
						mgf=padding.MGF1(algorithm=hashes.SHA1()),
						algorithm=hashes.SHA1(),
						label=None
					)
				)
			return ciphertext
		else:
			raise KeyError("Encryption failed because identity does not hold a public key")


	def decrypt(self, ciphertext):
		if self.prv != None:
			plaintext = None
			try:
				chunksize = Identity.DECRYPT_CHUNKSIZE
				chunks = int(math.ceil(len(ciphertext)/(float(chunksize))))

				plaintext = b"";
				for chunk in range(chunks):
					start = chunk*chunksize
					end = (chunk+1)*chunksize
					if (chunk+1)*chunksize > len(ciphertext):
						end = len(ciphertext)

					plaintext += self.prv.decrypt(
						ciphertext[start:end],
						padding.OAEP(
							mgf=padding.MGF1(algorithm=hashes.SHA1()),
							algorithm=hashes.SHA1(),
							label=None
						)
					)
			except:
				RNS.log("Decryption by "+RNS.prettyhexrep(self.hash)+" failed", RNS.LOG_VERBOSE)
				
			return plaintext;
		else:
			raise KeyError("Decryption failed because identity does not hold a private key")


	def sign(self, message):
		if self.prv != None:
			signature = self.prv.sign(
				message,
				padding.PSS(
					mgf=padding.MGF1(hashes.SHA256()),
					salt_length=padding.PSS.MAX_LENGTH
				),
				hashes.SHA256()
			)
			return signature
		else:
			raise KeyError("Signing failed because identity does not hold a private key")

	def validate(self, signature, message):
		if self.pub != None:
			try:
				self.pub.verify(
					signature,
					message,
					padding.PSS(
						mgf=padding.MGF1(hashes.SHA256()),
						salt_length=padding.PSS.MAX_LENGTH
					),
					hashes.SHA256()
				)
				return True
			except Exception as e:
				return False
		else:
			raise KeyError("Signature validation failed because identity does not hold a public key")

	def prove(self, packet, destination=None):
		signature = self.sign(packet.packet_hash)
		if RNS.Reticulum.should_use_implicit_proof():
			proof_data = signature
		else:
			proof_data = packet.packet_hash + signature
		
		if destination == None:
			destination = packet.generateProofDestination()

		proof = RNS.Packet(destination, proof_data, RNS.Packet.PROOF, attached_interface = packet.receiving_interface)
		proof.send()

	def __str__(self):
		return RNS.prettyhexrep(self.hash)