from os import path
def init():
	if not path.exists(config['path']): raise Exception(f"Backend directory doesn't exist: {config['path']}")
	for n in ['users','invite_tokens','access_tokens']:
		p=path.join(config['path'],n+'.csv')
		globals()[n]=p
		if not path.exists(p): open(p,'w').write('\n')
		if path.isdir(p): raise Exception(f"Backend file is a directory: {p}")
		try: open(p).close()
		except PermissionError: raise Exception(f"Backend file can't be read: {p}")
		try: open(p,'w').close()
		except PermissionError: raise Exception(f"Backend file can't be written: {p}")

def load_user(username):
	for line in linegen(users):
		split=line.split(',')
		if split[0]==username: return models.User(*split)
def save_user(user):
	gen=linegen(users)
	for line in gen:
		split=line.split(',')
		if split[0]==user.username: update(users,{gen.send(True):user.csv}); break
	else: update(users,{-1:user.csv})
def delete_user(user): pass

def load_tokens(user): pass
def save_token(token): pass
def delete_token(token): pass

def load_invites(user): pass
def save_invite(token): pass
def delete_invite(token): pass

def linegen(path):
	i=0
	file=open(path)
	line=file.readline()
	while line:
		i+=1
		response=yield line
		if response is not None: yield i
		line=file.readline()
	file.close()

def update(path,lines):
	i=0
	file=open(path)
	write=open(f'{path}.tmp','w')
	line=file.readline()
	while line:
		i+=1
		if i in lines: write.write(lines[i]+'\n')
		else: write.write(line)
		line=file.readline()
	if -1 in lines: write.write(lines[-1])
	file.close()
	write.close()