#!/usr/bin/env python3
"""
Database tools and functions.
"""
import MySQLdb
from flask import session
from passlib.hash import argon2

class Database():
	"""
	An interface to interact with the database.
	"""
	def __init__(self):
		"""
		Initalizes the database.
		"""
		with open("db_key", "r") as file:
			# TODO: encrypt this 
			self.user, self.db, self.key = file.read().strip().split()
		try:
			self.execute("SELECT * FROM `users`").fetchone()
		except MySQLdb.ProgrammingError: # database not initialized
			with open("anonkun.sql", "r") as file:
				commands = file.read().split(";")
			for cmd in commands:
				cmd = cmd.strip()
				if not cmd:
					continue
				self.execute(cmd)


	def execute(self, *args, **kwargs):
		"""
		Opens a connection to the app's database and executes the SQL
		statements passed to this function.
		"""
		with MySQLdb.connect(user=self.user,passwd=self.key,db=self.db) as cur:
			cur.execute(*args, **kwargs)
			return cur

_DB = Database()


def add_user(username, password):
	"""
	Adds a user to the database.
	"""
	if verify_username(username): # username taken
		return "username_taken"
	elif len(username) > 20:
		return "username_too_long"

	pw_hash = argon2.hash(password)
	_DB.execute(
		"INSERT INTO `users` (`username`, `password_hash`) VALUES (%s, %s)",
		(username, pw_hash))
	return "success"


def verify_password(username, password):
	"""
	Verifies a user's password.
	"""
	user = verify_username(username)
	if not user:
		return False

	user_id, _, pw_hash = user

	if argon2.verify(password, pw_hash):
		session["user_id"] = user_id
		return True
	else:
		return False


def verify_username(username):
	"""
	Checks to see if the given username is in the database.
	"""
	user = _DB.execute("SELECT * FROM `users` WHERE `username` = %s",
		(username,)).fetchone()
	if user:
		return user
	else:
		return False