#!/usr/bin/env python
# vim: set sw=4 et:

import argparse
import os
import sys
import logging
import umbra
import threading
import time
import surt
import signal
import kombu
from umbra import hq

arg_parser = argparse.ArgumentParser(prog=os.path.basename(__file__),
        description='crawl-url - browse urls, follow links',
        formatter_class=argparse.ArgumentDefaultsHelpFormatter)
arg_parser.add_argument('-u', '--url', dest='amqp_url', default='amqp://guest:guest@localhost:5672/%2f',
        help='URL identifying the amqp server to talk to')
arg_parser.add_argument('-e', '--executable', dest='chrome_exe', default='chromium-browser',
        help='executable to use to invoke chrome')
arg_parser.add_argument('-n', '--max-browsers', dest='max_browsers', default='1',
        help='max number of chrome instances simultaneously browsing pages')
arg_parser.add_argument('-v', '--verbose', dest='log_level',
        action="store_const", default=logging.INFO, const=logging.DEBUG)
arg_parser.add_argument('--version', action='version',
        version="umbra {} - {}".format(umbra.version, os.path.basename(__file__)))
args = arg_parser.parse_args(args=sys.argv[1:])

logging.basicConfig(stream=sys.stdout, level=args.log_level,
        format='%(asctime)s %(process)d %(levelname)s %(threadName)s %(name)s.%(funcName)s(%(filename)s:%(lineno)d) %(message)s')

browsers = set()
browsers_lock = threading.Lock()
num_browsers = 0

shutdown_requested = threading.Event()

def next_url(site):
    """Raises kombu.simple.Empty if queue is empty"""
    with kombu.Connection(args.amqp_url) as conn:
        q = conn.SimpleQueue("brozzler.sites.{}.crawl_urls".format(site.id))
        msg = q.get(block=True, timeout=0.5)
        crawl_url_dict = msg.payload
        crawl_url = umbra.CrawlUrl(**crawl_url_dict)
        msg.ack()
        return crawl_url

def completed(site, crawl_url):
    with kombu.Connection(args.amqp_url) as conn:
        q = conn.SimpleQueue("brozzler.sites.{}.completed_urls".format(site.id))
        logging.info("putting {} on queue {}".format(crawl_url, q.queue.name))
        q.put(crawl_url.to_dict())

def brozzle_site(site, chrome_port):
    with umbra.Browser(chrome_port=chrome_port, chrome_exe=args.chrome_exe) as browser:
        with browsers_lock:
            browsers.add(browser)
        try:
            while not shutdown_requested.is_set():
                try:
                    crawl_url = next_url(site)
                    logging.info("crawling {}".format(crawl_url))
                    crawl_url.outlinks = browser.browse_page(crawl_url.url)
                    completed(site, crawl_url)
                except kombu.simple.Empty:
                    # if some timeout reached, re-raise?
                    pass
        # except kombu.simple.Empty:
        #     logging.info("finished {} (queue is empty)".format(site))
        except umbra.browser.BrowsingAborted:
            logging.info("{} shut down")
        finally:
            with browsers_lock:
                browsers.remove(browser)

class ShutdownRequested(Exception):
    pass

def sigterm(signum, frame):
    raise ShutdownRequested('shutdown requested (caught SIGTERM)')
def sigint(signum, frame):
    raise ShutdownRequested('shutdown requested (caught SIGINT)')

signal.signal(signal.SIGTERM, sigterm)
signal.signal(signal.SIGINT, sigint)

latest_state = None
chrome_port = 9200
try:
    while True:
        if num_browsers < int(args.max_browsers):
            with kombu.Connection(args.amqp_url) as conn:
                q = conn.SimpleQueue("brozzler.sites.unclaimed")
                try:
                    msg = q.get(block=True, timeout=0.5)
                    site = hq.Site(**msg.payload)
                    logging.info("browsing site {}".format(site))
                    num_browsers += 1
                    msg.ack()
                    th = threading.Thread(target=lambda: brozzle_site(site, chrome_port), 
                            name="BrowsingThread-{}".format(site.scope_surt))
                    th.start()
                    chrome_port += 1
                except kombu.simple.Empty:
                    if latest_state != "no-unclaimed-sites":
                        logging.info("no unclaimed sites to browse")
                        latest_state = "no-unclaimed-sites"
        else:
            if latest_state != "browsers-busy":
                logging.info("all {} browsers are busy, not looking for unclaimed sites".format(args.max_browsers))
                latest_state = "browsers-busy"
            time.sleep(0.5)
except ShutdownRequested as e:
    logging.info("shutting down browsers")
    shutdown_requested.set()

    with browsers_lock:
        for browser in browsers:
            browser.abort_browse_page()

    for th in threading.enumerate():
        if th != threading.current_thread():
            th.join()
    
    logging.info("all done, exiting")