import os, fcntl
import json
from threading import Event

def makedirs():
	for dir in ["cache", "meta", "temp"]:
		if not os.path.isdir(dir):
			os.mkdir(dir)

def hash2fname(hash,temp=False):
	return os.path.join("temp" if temp else "cache",hash[:2],hash[:10])

def hash2meta_fname(hash):
	return os.path.join("meta",hash[:10]+".json")

class MetaFile:
	def __init__(self, hash):
		self.hash=hash
		
	def __enter__(self):
		fname=hash2meta_fname(self.hash)
		self.fd=open( fname, "r+" if os.path.isfile(fname) else "x+" )
		fcntl.lockf(self.fd, fcntl.LOCK_EX)
		return self
	
	def read(self):
		self.fd.seek(0)
		if self.fd.read(1):
			self.fd.seek(0)
			return json.load(self.fd)
		else: # file is empty
			return {}
	
	def write(self, data):
		self.fd.seek(0)
		self.fd.truncate()
		json.dump(data, self.fd)

	def __exit__(self, type, value, traceback):
		fcntl.lockf(self.fd, fcntl.LOCK_UN)

hashlocks:dict[str,Event]={}

class DataFile:
	def __init__(self, fd):
		self.fd=fd

	def __enter__(self):
		fcntl.lockf(self.fd, fcntl.LOCK_EX)
		return self.fd
	
	def __exit__(self, type, value, exception):
		fcntl.lockf(self.fd, fcntl.LOCK_UN)