import os, sys
import threading, Queue
import pyinotify

from bazjunk.path import makedirs
from bazbase import db, model, conversion

MAX_THREADS = 5

queue = Queue.PriorityQueue()
started = False

def render_from_queue():
    while True:
        neg_priority, ename, propname, format = queue.get()
        with db.begin_transaction():
            e = model.Element.get(ename)
            rendering = conversion.render(e, propname, format)

def start_render(ename, propnames, format, priority=0):
    global started
    if not started:
        # TODO(xavid): race
        started = True
        for x in xrange(MAX_THREADS):
            t = threading.Thread(target=render_from_queue)
            t.daemon = True
            t.start()

    for pn in propnames:
        queue.put((-priority, ename, pn, format))

def wait_for_render(ename, propnames, format):
    result_map = {}
    wm = pyinotify.WatchManager()
    dir = os.path.join(conversion.cache_dir(), ename)
    makedirs(dir)
    wdd = wm.add_watch(dir, pyinotify.IN_CLOSE_WRITE | pyinotify.IN_MOVED_TO)
    notifier = pyinotify.Notifier(wm)
    while True:
        for pn in propnames:
            rendering = conversion.cached(ename, pn, format)
            if rendering is not None:
                result_map[pn] = rendering
        if result_map:
            return result_map
        # If nothing, wait for an event.
        notifier.check_events()