import pycurl
from cStringIO import StringIO
import time
from collections import deque
from itertools import islice
from urlparse import urlsplit
import select

# curl_multi_perform -> transfer data on ready sockets & get num of active handlers
# curl_multi_fdset -> extract handlers to use in select/poll
# curl_multi_info_read -> info about handlers completed their work

DEFAULT_POOL_SIZE = 200

# Idea:
# task generator (in term of Spider) and task queue are both
# just task generators of different kind. They both produces tasks
# and therefor should have same interface:
# * get_task
# * is_active

class Crawler(object):
    def __init__(self, pool_size=DEFAULT_POOL_SIZE):
        self.pool_size = pool_size
        self._timer = {
            'stat': time.time(),
            'watchdog': time.time(),
        }
        self._timer_watchdog = time.time()
        self.init_multi_interface()
        self.build_task_generators()

    def build_task_generators(self):
        self.task_gens = []
        if hasattr(self, 'task_generator'):
            self.task_gens.append(CallbackTaskGenerator(self.task_generator()))

    def init_multi_interface(self):
        self.handler_reg = {}
        self.free_handlers = deque()
        self.active_handlers = deque()
        self.multi = pycurl.CurlMulti()
        for x in xrange(self.pool_size):
            handler = pycurl.Curl()
            self.free_handlers.append(handler)
        self._next_timeout = None

    def process_handler_data(self, handler, task, body):
        try:
            result = body.splitlines()[0]
        except IndexError:
            result = 'NA'
        print task['url'], '-->', result

    def add_task_to_work(self, task):
        handler = self.free_handlers.pop()
        handler.setopt(pycurl.URL, task['url'])
        handler.setopt(pycurl.FOLLOWLOCATION, True)
        handler.setopt(pycurl.MAXREDIRS, 5)
        TIMEOUT = 15
        handler.setopt(pycurl.TIMEOUT, TIMEOUT)
        handler.setopt(pycurl.CONNECTTIMEOUT, 5)

        buf = StringIO()
        self.handler_reg[handler] = {
            'buffer': buf,
            'task': task,
            'time_start': time.time(),
            'timeout': TIMEOUT,
        }
        handler.setopt(pycurl.WRITEFUNCTION, buf.write)
        self.multi.add_handle(handler)
        self.active_handlers.append(handler)

    def trigger_stat_logging(self, now):
        if now - self._timer['stat'] > 2:
            self._timer['stat'] = now
            print '===>>>'
            print 'Active handlers:'
            for handler in self.active_handlers:
                info = self.handler_reg[handler]
                age = time.time() - info['start_time'] 
                print '* %s --> %s [%.3f]' % (id(handler), info['task']['url'], age)
            print '<<<==='

    def trigger_watchdog(self, now):
        if now - self._timer['watchdog'] > 1:
            killed_handlers = set()
            kill_list = []

            self._timer['watchdog'] = now
            for handler in self.active_handlers:
                info = self.handler_reg[handler]
                if now - info['time_start'] > info['timeout']:
                    kill_list.append((handler, info))

            for handler, info in kill_list:
                print 'Explicitly kill timed out handler'
                self.process_completed_handler(handler, -1, 'Watchdog timeout (%d)' % info['timeout'])
                killed_handlers.add(handler)

            return killed_handlers

    def trigger_data_io(self):
        rlist, wlist, xlist = self.multi.fdset()
        if rlist or wlist or xlist:
            timeout = self.multi.timeout()
            if timeout:
                select.select(rlist, wlist, xlist, timeout / 1000.0)
        else:
            time.sleep(0.1)

        # Trigger data transfers
        while True:
            opcode, active_num = self.multi.perform()
            if opcode != pycurl.E_CALL_MULTI_PERFORM:
                break

    def get_completed_handlers(self):
        more_count, ok_handlers, fails = self.multi.info_read()
        for ok_handler in ok_handlers: 
            yield ok_handler, None, None
        for fail_handler, err_no, err_msg in fails:
            yield fail_handler, err_no, err_msg

    def process_completed_handler(self, handler, err_no, err_msg):
        info = self.handler_reg[handler]
        if err_no is None:
            info['task']['callback'](handler, info['task'], info['buffer'].getvalue())
        else:
            print u'ERROR [%s]: %s' % (info['task']['url'], err_msg)
        self.active_handlers.remove(handler)
        self.multi.remove_handle(handler)
        handler.reset()
        self.free_handlers.append(handler)

    def has_active_handlers(self):
        return len(self.active_handlers) > 0

    def get_next_task(self):
        task = None
        for gen in self.task_gens:
            if gen.is_active():
                task = gen.get_task()
                if task is not None:
                    break
        return task

    def run(self):
        dump_time = time.time()

        while self.has_active_handlers() or any(x.is_active() for x in self.task_gens):
            if self.free_handlers:
                task = self.get_next_task()
                if task is not None:
                    self.add_task_to_work(task)
        
            now = time.time()
            self.trigger_stat_logging(now)
            killed_handlers = self.trigger_watchdog(now)

            self.trigger_data_io()

            for handler, err_no, err_msg in self.get_completed_handlers():
                if killed_handlers and handler in killed_handlers:
                    pass
                else:
                    self.process_completed_handler(handler, err_no, err_msg)


class CallbackTaskGenerator(object):
    def __init__(self, gen):
        self.gen = gen
        self._active = True

    def get_task(self):
        if self._active:
            try:
                return self.gen.next()
            except StopIteration:
                self._active = False
        return None

    def is_active(self):
        return self._active