#!/usr/bin/env python3
"""
Allows the bot to scheduler tasks to be performed later.
"""
import pickle
import threading
from datetime import datetime

stop = threading.Event()

class CronThread(threading.Thread):
	def __init__(self, scheduler):
		super().__init__()
		self.scheduler = scheduler

	def run(self):
		while not self.scheduler.bot.stillConnected():
			stop.wait(1)
		while not stop.is_set():
			self.scheduler.run_tasks()
			stop.wait(5)

class Scheduler:
	def __init__(self, bot):
		self.bot = bot
		self.tasks = []
		self.lock = threading.Lock()
		self.init_database()
		self.load_database()
		self.bot.add_shutdown(stop.set)
		self.loop = CronThread(self)
		self.loop.start()

	def run_tasks(self):
		self.lock.acquire()
		tasks_due = [t for t in self.tasks if t[1] <= datetime.now()]
		for task in tasks_due:
			args = (self.bot,) + (task[1],) + task[2]
			t = threading.Thread(target=task[0], args=args)
			t.start()
			self.tasks.remove(task)
			self.bot.db.execute(
				"DELETE FROM scheduled_task WHERE dt = ?",
				(pickle.dumps(task[1]),))
		self.lock.release()


	def add_task(self, func, dt, args):
		"""
		`func` - The function to call. Must accept `bot` as the first
		argument. Must be picklable.
		`dt` - A datetime object representing when to call the function.
		`args` - Arguments to call the function with, not including `bot`.
		"""
		self.lock.acquire()
		self.tasks.append((func, dt, args))
		self.lock.release()

		t = tuple(pickle.dumps(i) for i in (func, dt, args))
		self.bot.db.execute("INSERT INTO scheduled_task VALUES (?,?,?)", t)

	def init_database(self):
		self.bot.db.execute("CREATE TABLE IF NOT EXISTS scheduled_task ("
			"func BLOB,"
			"dt BLOB,"
			"args BLOB"
			")")

	def load_database(self):
		tasks = self.bot.db.execute("SELECT * FROM scheduled_task").fetchall()
		for task in tasks:
			t = tuple(pickle.loads(i) for i in task)
			self.tasks.append(t)

	def dump_database(self):
		self.bot.db.execute("DELETE FROM scheduled_task")
		for task in self.tasks:
			t = tuple(pickle.dumps(i) for i in task)
			self.bot.db.execute("INSERT INTO scheduled_task VALUES (?,?,?)", t)