from collections import OrderedDict
import json
import posixpath
import random
import threading
import traceback
import sys

from mysos.common.cluster import get_cluster_path
from mysos.common.decorators import logged

from .launcher import MySQLClusterLauncher
from .password import gen_password, PasswordBox
from .state import MySQLCluster, Scheduler, StateProvider

import mesos.interface
import mesos.interface.mesos_pb2 as mesos_pb2
from twitter.common import log
from twitter.common.collections.orderedset import OrderedSet
from twitter.common.metrics import AtomicGauge, MutatorGauge, Observable
from twitter.common.quantity import Amount, Data, Time
from twitter.common.quantity.parse_simple import InvalidData, parse_data


DEFAULT_TASK_CPUS = 1.0
DEFAULT_TASK_DISK = Amount(2, Data.GB)
DEFAULT_TASK_MEM = Amount(512, Data.MB)

# Refuse the offer for "eternity".
# NOTE: Using sys.maxint / 2 because sys.maxint causes rounding and precision loss when converted to
# double 'refuse_seconds' in the ProtoBuf and results in a negative duration on Mesos Master.
INCOMPATIBLE_ROLE_OFFER_REFUSE_DURATION = Amount(sys.maxint / 2, Time.NANOSECONDS)


class MysosScheduler(mesos.interface.Scheduler, Observable):

  class Error(Exception): pass

  class ClusterExists(Error): pass
  class ClusterNotFound(Error): pass
  class InvalidUser(Error): pass
  class ServiceUnavailable(Error): pass

  def __init__(
      self,
      state,
      state_provider,
      framework_user,
      executor_uri,
      executor_cmd,
      kazoo,
      zk_url,
      election_timeout,
      admin_keypath,
      scheduler_key,
      installer_args=None,
      backup_store_args=None,
      executor_environ=None,
      executor_source_prefix=None,
      framework_role='*'):
    """
      :param state: The Scheduler object.
      :param state_provider: The StateProvider instance that the scheduler should use to
                             restore/persist states.
      :param framework_user: See flags.
      :param executor_uri: See flags.
      :param executor_cmd: See flags.
      :param framework_role: See flags.
      :param election_timeout: See flags.
      :param admin_keypath: See flags.
      :param scheduler_key: Scheduler uses it to encrypt cluster passwords.
      :param installer_args: See flags.
      :param backup_store_args: See flags.
      :param executor_environ: See flags.
      :param executor_source_prefix: See flags.
      :param kazoo: The Kazoo client for communicating MySQL cluster information between the
                    scheduler and the executors.
      :param zk_url: ZooKeeper URL for used by the scheduler and the executors to access ZooKeeper.
    """
    self._lock = threading.Lock()

    if not isinstance(state, Scheduler):
      raise TypeError("'state' should be an instance of Scheduler")
    self._state = state

    if not isinstance(state_provider, StateProvider):
      raise TypeError("'state_provider' should be an instance of StateProvider")
    self._state_provider = state_provider

    self._framework_user = framework_user
    self._executor_uri = executor_uri
    self._executor_cmd = executor_cmd
    self._framework_role = framework_role
    self._election_timeout = election_timeout
    self._admin_keypath = admin_keypath
    self._installer_args = installer_args
    self._backup_store_args = backup_store_args
    self._executor_environ = executor_environ
    self._executor_source_prefix = executor_source_prefix

    self._driver = None  # Will be set by registered().

    # Use a subdir to avoid name collision with the state storage.
    self._discover_zk_url = posixpath.join(zk_url, "discover")
    self._kazoo = kazoo

    self._scheduler_key = scheduler_key
    self._password_box = PasswordBox(scheduler_key)

    self._tasks = {}  # {Task ID: cluster name} mappings.
    self._launchers = OrderedDict()  # Order-preserving {cluster name : MySQLClusterLauncher}
                                     # mappings so cluster requests are fulfilled on a first come,
                                     # first serve (FCFS) basis.

    self.stopped = threading.Event()  # An event set when the scheduler is stopped.
    self.connected = threading.Event()  # An event set when the scheduler is first connected to
                                        # Mesos. The scheduler tolerates later disconnections.

    self._cluster_count = self.metrics.register(AtomicGauge('cluster_count', 0))

    # Total resources requested by the scheduler's clients. When a cluster is created its resources
    # are added to the total; when it's deleted its resources are subtracted from the total.
    # NOTE: These are 'requested' resources that are independent of resources offered by Mesos or
    # allocated to or used by Mysos tasks running on Mesos cluster.
    self._total_requested_cpus = self.metrics.register(MutatorGauge('total_requested_cpus', 0.))
    self._total_requested_mem_mb = self.metrics.register(MutatorGauge('total_requested_mem_mb', 0.))
    self._total_requested_disk_mb = self.metrics.register(
        MutatorGauge('total_requested_disk_mb', 0.))

  # --- Public interface. ---
  def create_cluster(
        self,
        cluster_name,
        cluster_user,
        num_nodes,
        size=None,
        backup_id=None,
        cluster_password=None):
    """
      :param cluster_name: Name of the cluster.
      :param cluster_user: The user account on MySQL server.
      :param num_nodes: Number of nodes in the cluster.
      :param size: The size of instances in the cluster as a JSON dictionary of 'cpus', 'mem',
                   'disk'. 'mem' and 'disk' are specified with data size units: kb, mb, gb, etc. If
                   given 'None' then app defaults are used.
      :param backup_id: The 'backup_id' of the backup to restore from. If None then Mysos starts an
                        empty instance.
      :param cluster_password: The password used for accessing MySQL instances in the cluster as
                               well as deleting the cluster from Mysos. If None then Mysos generates
                               one for the cluster. In either case the password is sent back as
                               part of the return value.

      :return: a tuple of the following:
        - ZooKeeper URL for this Mysos cluster that can be used to resolve MySQL cluster info.
        - The password for the specified user of the specified cluster.

      NOTE:
        If the scheduler fails over after the cluster state is checkpointed, the new scheduler
        instance will restore the state and continue to launch the cluster. TODO(jyx): Need to allow
        users to retrieve the cluster info (e.g. the passwords) afterwards in case the user request
        has failed but the cluster is successfully created eventually.
    """
    with self._lock:
      if not self._driver:
        # 'self._driver' is set in (re)registered() after which the scheduler becomes "available".
        # We need to get hold of the driver to recover the scheduler.
        raise self.ServiceUnavailable("Service unavailable. Try again later")

      if cluster_name in self._state.clusters:
        raise self.ClusterExists("Cluster '%s' already exists" % cluster_name)

      if not cluster_user:
        raise self.InvalidUser('Invalid user name: %s' % cluster_user)

      num_nodes = int(num_nodes)
      if num_nodes <= 0:
        raise ValueError("Invalid number of cluster nodes: %s" % num_nodes)

      resources = parse_size(size)
      log.info("Requested resources per instance for cluster %s: %s" % (resources, cluster_name))

      self._total_requested_cpus.write(
          self._total_requested_cpus.read() + resources['cpus'] * num_nodes)
      self._total_requested_mem_mb.write(
          self._total_requested_mem_mb.read() + resources['mem'].as_(Data.MB) * num_nodes)
      self._total_requested_disk_mb.write(
          self._total_requested_disk_mb.read() + resources['disk'].as_(Data.MB) * num_nodes)

      self._state.clusters.add(cluster_name)
      self._state_provider.dump_scheduler_state(self._state)

      if not cluster_password:
        log.info("Generating password for cluster %s" % cluster_name)
        cluster_password = gen_password()

      # Return the plaintext version to the client but store the encrypted version.
      cluster = MySQLCluster(
          cluster_name,
          cluster_user,
          self._password_box.encrypt(cluster_password),
          num_nodes,
          cpus=resources['cpus'],
          mem=resources['mem'],
          disk=resources['disk'],
          backup_id=backup_id)
      self._state_provider.dump_cluster_state(cluster)

      log.info("Creating launcher for cluster %s" % cluster_name)
      self._launchers[cluster_name] = MySQLClusterLauncher(
          self._driver,
          cluster,
          self._state_provider,
          self._discover_zk_url,
          self._kazoo,
          self._framework_user,
          self._executor_uri,
          self._executor_cmd,
          self._election_timeout,
          self._admin_keypath,
          self._scheduler_key,
          installer_args=self._installer_args,
          backup_store_args=self._backup_store_args,
          executor_environ=self._executor_environ,
          executor_source_prefix=self._executor_source_prefix,
          framework_role=self._framework_role)

      self._cluster_count.increment()

      return get_cluster_path(self._discover_zk_url, cluster_name), cluster_password

  def delete_cluster(self, cluster_name, password):
    """
      :return: ZooKeeper URL for this Mysos cluster that can be used to wait for the termination of
               the cluster.
    """
    with self._lock:
      if not self._driver:
        raise self.ServiceUnavailable("Service unavailable. Try again later")

      if cluster_name not in self._state.clusters:
        raise self.ClusterNotFound("Cluster '%s' not found" % cluster_name)

      launcher = self._launchers[cluster_name]
      launcher.kill(password)
      log.info("Attempted to kill cluster %s" % cluster_name)

      self._cluster_count.decrement()
      cluster_info = launcher.cluster_info
      self._total_requested_cpus.write(self._total_requested_cpus.read() - cluster_info.total_cpus)
      self._total_requested_mem_mb.write(
          self._total_requested_mem_mb.read() - cluster_info.total_mem_mb)
      self._total_requested_disk_mb.write(
          self._total_requested_disk_mb.read() - cluster_info.total_disk_mb)

      if launcher.terminated:
        log.info("Deleting the launcher for cluster %s directly because the cluster has already "
                 "terminated" % launcher.cluster_name)
        self._delete_launcher(launcher)

      return get_cluster_path(self._discover_zk_url, cluster_name)

  @property
  def clusters(self):
    """
      A generator for information about clusters.
    """
    with self._lock:
      for launcher in self._launchers.values():
        yield launcher.cluster_info

  def _stop(self):
    """Stop the scheduler."""

    # 'self._driver' is set in registered() so it could be None if the scheduler is asked to stop
    # before it is registered (e.g. an error is received).
    if self._driver:
      self._driver.stop(True)  # Set failover to True.
    self.stopped.set()

  # --- Mesos methods. ---
  @logged
  def registered(self, driver, frameworkId, masterInfo):
    self._driver = driver
    self._state.framework_info.id.value = frameworkId.value
    self._state_provider.dump_scheduler_state(self._state)

    # Recover only after the scheduler is connected because it needs '_driver' to be assigned. This
    # is blocking the scheduler driver thread but we do want further messages to be blocked until
    # the scheduler state is fully recovered.
    # TODO(jyx): If performance becomes an issue, we can also restore all the state data while the
    # driver is connecting and proceed to recover all the internal state objects after the driver is
    # connected.
    try:
      self._recover()
    except Exception as e:
      log.error("Stopping scheduler because: %s" % e)
      log.error(traceback.format_exc())
      self._stop()
      return

    self.connected.set()

  def _recover(self):
    """
      Recover launchers for existing clusters. A newly created scheduler has no launcher to recover.
      TODO(jyx): The recovery of clusters can potentially be parallelized.
    """
    for cluster_name in OrderedSet(self._state.clusters):  # Make a copy so we can remove dead
                                                           # entries while iterating the copy.
      log.info("Recovering launcher for cluster %s" % cluster_name)

      cluster = self._state_provider.load_cluster_state(cluster_name)
      if not cluster:
        # The scheduler could have failed over before creating the launcher. The user request
        # should have failed and there is no cluster state to restore.
        log.info("Skipping cluster %s because its state cannot be found" % cluster_name)
        self._state.clusters.remove(cluster_name)
        self._state_provider.dump_scheduler_state(self._state)
        continue

      for task_id in cluster.tasks:
        self._tasks[task_id] = cluster.name  # Reconstruct the 'tasks' map.

      # Order of launchers is preserved thanks to the OrderedSet.
      # For recovered launchers we use the currently specified --framework_role and
      # --executor_environ, etc., instead of saving it in cluster state so the change in flags can
      # be picked up by existing clusters.
      self._launchers[cluster.name] = MySQLClusterLauncher(
          self._driver,
          cluster,
          self._state_provider,
          self._discover_zk_url,
          self._kazoo,
          self._framework_user,
          self._executor_uri,
          self._executor_cmd,
          self._election_timeout,
          self._admin_keypath,
          self._scheduler_key,
          installer_args=self._installer_args,
          backup_store_args=self._backup_store_args,
          executor_environ=self._executor_environ,
          executor_source_prefix=self._executor_source_prefix,
          framework_role=self._framework_role)

      # Recover metrics from restored state.
      self._cluster_count.increment()

      cluster_info = self._launchers[cluster.name].cluster_info
      self._total_requested_cpus.write(self._total_requested_cpus.read() + cluster_info.total_cpus)
      self._total_requested_mem_mb.write(
          self._total_requested_mem_mb.read() + cluster_info.total_mem_mb)
      self._total_requested_disk_mb.write(
          self._total_requested_disk_mb.read() + cluster_info.total_disk_mb)

    log.info("Recovered %s clusters" % len(self._launchers))

  @logged
  def reregistered(self, driver, masterInfo):
    self._driver = driver
    self.connected.set()
    # TODO(jyx): Reconcile tasks.

  @logged
  def disconnected(self, driver):
    pass

  @logged
  def resourceOffers(self, driver, offers):
    log.info('Got %d resource offers' % len(offers))

    with self._lock:
      # Current scheduling algorithm: randomly pick an offer and loop through the list of launchers
      # until one decides to use this offer to launch a task.
      # It's possible to launch multiple tasks on the same Mesos slave (in different batches of
      # offers).
      for offer in shuffled(offers):
        task_id = None
        # 'filters' is set when we need to create a special filter for incompatible roles.
        filters = None
        # For each offer, launchers are asked to launch a task in the order they are added (FCFS).
        for name in self._launchers:
          launcher = self._launchers[name]
          try:
            task_id, _ = launcher.launch(offer)
          except MySQLClusterLauncher.IncompatibleRoleError as e:
            # This "error" is not severe and we expect this to occur frequently only when Mysos
            # first joins the cluster. For a running Mesos cluster this should be somewhat rare
            # because we refuse the offer "forever".
            filters = mesos_pb2.Filters()
            filters.refuse_seconds = INCOMPATIBLE_ROLE_OFFER_REFUSE_DURATION.as_(Time.SECONDS)
            break  # No need to check with other launchers.
          if task_id:
            self._tasks[task_id] = launcher.cluster_name
            # No need to check with other launchers. 'filters' remains unset.
            break
        if task_id:
          break  # Some launcher has used this offer. Move on to the next one.

        if filters:
          log.info("Declining offer %s for %s because '%s'" % (
              offer.id.value, INCOMPATIBLE_ROLE_OFFER_REFUSE_DURATION, e))
        else:
          log.info("Declining offer %s because no launcher accepted this offer" % offer.id.value)
          # Mesos scheduler Python binding doesn't deal with filters='None' properly.
          # See https://issues.apache.org/jira/browse/MESOS-2567.
          filters = mesos_pb2.Filters()

        log.debug(offer)
        self._driver.declineOffer(offer.id, filters)

  @logged
  def statusUpdate(self, driver, status):
    with self._lock:
      # Forward the status update to the corresponding launcher.
      task_id = status.task_id.value
      launcher = self._get_launcher_by_task_id(task_id)
      if not launcher:
        log.info("Cluster for task %s doesn't exist. It could have been removed" % task_id)
        return

      try:
        launcher.status_update(status)
      except MySQLClusterLauncher.Error as e:
        log.error("Status update failed due to launcher error: %s" % e.message)
        self._stop()

      if launcher.terminated:
        log.info("Deleting the launcher for cluster %s because the cluster has terminated" %
                 launcher.cluster_name)
        self._delete_launcher(launcher)

  def _delete_launcher(self, launcher):
    assert launcher.terminated
    self._state.clusters.discard(launcher.cluster_name)
    self._state_provider.dump_scheduler_state(self._state)
    self._launchers[launcher.cluster_name].stop()
    del self._launchers[launcher.cluster_name]

  @logged
  def frameworkMessage(self, driver, executorId, slaveId, message):
    log.info('Received framework message %s' % message)
    task_id = executorId.value  # task_id == executor_id in Mysos.

    launcher = self._get_launcher_by_task_id(task_id)
    launcher.framework_message(task_id, slaveId.value, message)

  @logged
  def slaveLost(self, driver, slaveId):
    # We receive TASK_LOSTs when a slave is lost so we we don't need to handle it separately here.
    pass

  @logged
  def error(self, driver, message):
    log.error('Received error from mesos: %s' % message)
    self._stop()  # SchedulerDriver aborts when an error message is received.

  def _get_launcher_by_task_id(self, task_id):
    # TODO(jyx): Currently we don't delete entries from 'self._tasks' so a mapping can always
    # be found but we should clean it up when tasks die.
    assert task_id in self._tasks
    cluster_name = self._tasks[task_id]
    return self._launchers.get(cluster_name)  # Cluster could have been removed.


def shuffled(li):
  """Return a shuffled version of the list."""
  copy = li[:]
  random.shuffle(copy)
  return copy


def parse_size(size):
  """Return the resources specified in 'size' as a dictionary."""
  if not size:
    resources = dict(cpus=DEFAULT_TASK_CPUS, mem=DEFAULT_TASK_MEM, disk=DEFAULT_TASK_DISK)
  else:
    # TODO(jyx): Simplify this using T-shirt sizing
    # (https://github.com/twitter/mysos/issues/14).
    try:
      resources_ = json.loads(size)
      resources = dict(
        cpus=float(resources_['cpus']),
        mem=parse_data(resources_['mem']),
        disk=parse_data(resources_['disk']))
    except (TypeError, KeyError, ValueError, InvalidData):
      raise ValueError("'size' should be a JSON dictionary with keys 'cpus', 'mem' and 'disk'")

  return resources