# TODO
#  1. send an email to an email address defined by env['admin-email']
#     if resources are finished
#  2. v3) Introduce a status endpoint of the scheduler -
#     maybe expose a prometheus compatible output

import argparse
import logging

from decouple import config

from etcd3_wrapper import Etcd3Wrapper

from ucloud_common.vm import VmPool
from ucloud_common.host import HostPool
from ucloud_common.request import RequestEntry, RequestPool, RequestType
from helper import (get_suitable_host, dead_host_mitigation, dead_host_detection,
                    assign_host)

logging.basicConfig(
    level=logging.DEBUG,
    filename="log.txt",
    filemode="a",
    format="%(asctime)s: %(levelname)s - %(message)s",
    datefmt="%d-%b-%y %H:%M:%S",
)


def main(vm_prefix, host_prefix, request_prefix):
    logging.info(f"{'*' * 5} SESSION STARTED {'*' * 5}")
    client = Etcd3Wrapper(
        host=config("ETCD_HOST"), port=int(config("ETCD_PORT"))
    )
    vm_pool = VmPool(client, vm_prefix)
    host_pool = HostPool(client, host_prefix)
    request_pool = RequestPool(client, request_prefix)

    PENDING_VMS = []
    for events_iterator in [
        client.get_prefix(request_prefix, value_in_json=True),
        client.watch_prefix(request_prefix, timeout=5, value_in_json=True),
    ]:
        for e in events_iterator:
            if not e.value:
                continue
            e = RequestEntry(e)
            logging.debug(f"{e.key}, {e.value}")

            # Never Run time critical mechanism inside timeout
            # mechanism because timeout mechanism only comes
            # when no other event is happening. It means under
            # heavy load there would not be a timeout<
            if e.type == "TIMEOUT":
                logging.debug("TIMEOUT event occured")
                dead_hosts = dead_host_detection()
                logging.debug(f"Dead hosts: {dead_hosts}")
                dead_host_mitigation(dead_hosts)
                #
                # vm_scheduled = []
                # for vm in PENDING_VMS:
                #     if assign_host(vm) is not None:
                #         vm_scheduled.append(vm)
                #
                # for vm in vm_scheduled:
                #     PENDING_VMS.remove(vm)
                # logging.debug(f"Remaining Pending: {PENDING_VMS}")

            elif e.type == RequestType.ScheduleVM:
                if hasattr(e, "migration") and e.migration and\
                        hasattr(e, "destination") and e.destination:
                    client.client.delete(e.key)
                    vm = vm_pool.get(e.uuid)
                    host = get_suitable_host(vm.specs, [host_pool.get(e.destination)])
                    if host:
                        r = RequestEntry.from_scratch(type=RequestType.InitVMMigration,
                                                      uuid=e.uuid, destination=e.destination)
                        request_pool.put(r)
                        print(host, e)
                    else:
                        logging.info("Requested destination host doesn't have enough capacity"
                                     f"to hold {vm.uuid}")
                else:
                    client.client.delete(e.key)
                    vm = vm_pool.get(e.uuid)
                    if assign_host(vm) is None:
                        vm.log.append("Can't schedule VM. No Resource Left.")
                        vm_pool.put(vm)

                        PENDING_VMS.append(vm)
                        logging.info("No Resource Left. Emailing admin....")
                        logging.debug(f"Pending VMS: {PENDING_VMS}")


if __name__ == "__main__":
    argparser = argparse.ArgumentParser()
    argparser.add_argument(
        "--vm_prefix", required=False, default=config("VM_PREFIX")
    )
    argparser.add_argument(
        "--host_prefix", required=False, default=config("HOST_PREFIX")
    )
    argparser.add_argument(
        "--request_prefix", required=False, default=config("REQUEST_PREFIX")
    )
    args = argparser.parse_args()

    main(args.vm_prefix, args.host_prefix, args.request_prefix)