from dataclasses import dataclass
from datetime import datetime
from hashlib import shake_256
import uuid

def phash(pw,salt=None):
	if salt is None: salt=uuid.uuid4()
	return shake_256(f'{pw}{salt}'.encode('utf-8')).hexdigest(256),salt

class AbstractUser():
	pass # It fixes circular dep on user.invited_by
	# And on User.register (InviteToken)

@dataclass
class Token():
	value: str
	owner: AbstractUser
	def __init__(self,value,owner=None):
		if owner is None:
			owner=value
			self.value=uuid.uuid4()
		else:
			self.value=uuid.UUID(value)
		self.owner=owner
	def revoke(self):
		backend.delete_token(self)

@dataclass
class InviteToken(Token):
	_uses: int=0
	_max_uses: int=-1
	_expires: datetime=None
	def __init__(self,*args,**kwargs):
		return super().__init__(*args,**kwargs)
	@property
	def uses(self): return self._uses
	@uses.setter
	def uses(self,val):
		if -1<self.max_uses<=val: self.revoke()
		self._uses=val
	@property
	def max_uses(self): return self._max_uses
	@max_uses.setter
	def max_uses(self,val):
		if -1<val<=self.uses: self.revoke()
		self._max_uses=val

@dataclass
class AccessToken(Token):
	def __init__(self,*args,**kwargs):
		return super().__init__(*args,**kwargs)

@dataclass
class User(AbstractUser):
	username: str
	password_hash: str
	salt: str
	invited_by: AbstractUser=None # Root node will just reference itself
	email: str=''
	@property
	def csv(self):
		return ','.join([self.username,self.password_hash,str(self.salt),self.invited_by.username,self.email])
	def create_inv_token(self,*args,**kwargs):
		tok=InviteToken(self,*args,**kwargs)
		backend.save_token(tok)
		return tok
	def change_password(self,old_pw:str|None,new_pw:str): pass
	def save(self):
		backend.save_user(self)
	
	@classmethod
	def login(cls,username:str,password:str):
		u=backend.load_user(username)
		if u is None: raise Exception("User doesn't exist")
		if phash(password,u.salt)[0]==u.password_hash: return AccessToken(u)
		raise Exception("Incorrect password")
	@classmethod
	def register(cls,username:str,password:str,invite:InviteToken,email:str|None):
		if set([chr(n) for n in range(32)]+[','])&set(username): raise Exception('Invalid username')
		u=backend.load_user(username)
		if u is not None: raise Exception("User already exists")
		u=User(username,*phash(password),invite.owner,email)
		u.save()
		invite.uses+=1
		return u