import logging
import os
import sys
import time
import socket
import warnings

from datetime import datetime

from celery import platforms
from celery.app import app_or_default, current_app
from celery.datastructures import ExceptionInfo
from celery.exceptions import SoftTimeLimitExceeded, TimeLimitExceeded
from celery.exceptions import WorkerLostError, RetryTaskError
from celery.execute.trace import TaskTrace
from celery.registry import tasks
from celery.utils import noop, kwdict, fun_takes_kwargs
from celery.utils import truncate_text
from celery.utils.compat import log_with_extra
from celery.utils.timeutils import maybe_iso8601
from celery.worker import state

# pep8.py borks on a inline signature separator and
# says "trailing whitespace" ;)
EMAIL_SIGNATURE_SEP = "-- "

#: format string for the body of an error e-mail.
TASK_ERROR_EMAIL_BODY = """
Task %%(name)s with id %%(id)s raised exception:\n%%(exc)r


Task was called with args: %%(args)s kwargs: %%(kwargs)s.

The contents of the full traceback was:

%%(traceback)s

%(EMAIL_SIGNATURE_SEP)s
Just to let you know,
celeryd at %%(hostname)s.
""" % {"EMAIL_SIGNATURE_SEP": EMAIL_SIGNATURE_SEP}


#: Keys to keep from the message delivery info.  The values
#: of these keys must be pickleable.
WANTED_DELIVERY_INFO = ("exchange", "routing_key", "consumer_tag", )


class InvalidTaskError(Exception):
    """The task has invalid data or is not properly constructed."""


class AlreadyExecutedError(Exception):
    """Tasks can only be executed once, as they might change
    world-wide state."""


class WorkerTaskTrace(TaskTrace):
    """Wraps the task in a jail, catches all exceptions, and
    saves the status and result of the task execution to the task
    meta backend.

    If the call was successful, it saves the result to the task result
    backend, and sets the task status to `"SUCCESS"`.

    If the call raises :exc:`celery.exceptions.RetryTaskError`, it extracts
    the original exception, uses that as the result and sets the task status
    to `"RETRY"`.

    If the call results in an exception, it saves the exception as the task
    result, and sets the task status to `"FAILURE"`.

    :param task_name: The name of the task to execute.
    :param task_id: The unique id of the task.
    :param args: List of positional args to pass on to the function.
    :param kwargs: Keyword arguments mapping to pass on to the function.

    :keyword loader: Custom loader to use, if not specified the current app
      loader will be used.
    :keyword hostname: Custom hostname to use, if not specified the system
      hostname will be used.

    :returns: the evaluated functions return value on success, or
        the exception instance on failure.

    """

    #: Current loader.
    loader = None

    #: Hostname to report as.
    hostname = None

    def __init__(self, *args, **kwargs):
        self.loader = kwargs.get("loader") or current_app().loader
        self.hostname = kwargs.get("hostname") or socket.gethostname()
        super(WorkerTaskTrace, self).__init__(*args, **kwargs)

        self._store_errors = True
        if self.task.ignore_result:
            self._store_errors = self.task.store_errors_even_if_ignored
        self.super = super(WorkerTaskTrace, self)

    def execute_safe(self, *args, **kwargs):
        """Same as :meth:`execute`, but catches errors."""
        try:
            return self.execute(*args, **kwargs)
        except Exception, exc:
            _type, _value, _tb = sys.exc_info()
            _value = self.task.backend.prepare_exception(exc)
            exc_info = ExceptionInfo((_type, _value, _tb))
            warnings.warn("Exception outside body: %s: %s\n%s" % tuple(
                map(str, (exc.__class__, exc, exc_info.traceback))))
            return exc_info

    def execute(self):
        """Execute, trace and store the result of the task."""
        self.loader.on_task_init(self.task_id, self.task)
        if self.task.track_started:
            if not self.task.ignore_result:
                self.task.backend.mark_as_started(self.task_id,
                                                  pid=os.getpid(),
                                                  hostname=self.hostname)
        try:
            return super(WorkerTaskTrace, self).execute()
        finally:
            self.task.backend.process_cleanup()
            self.loader.on_process_cleanup()

    def handle_success(self, retval, *args):
        """Handle successful execution."""
        if not self.task.ignore_result:
            self.task.backend.mark_as_done(self.task_id, retval)
        return self.super.handle_success(retval, *args)

    def handle_retry(self, exc, type_, tb, strtb):
        """Handle retry exception."""
        message, orig_exc = exc.args
        if self._store_errors:
            self.task.backend.mark_as_retry(self.task_id, orig_exc, strtb)
        return self.super.handle_retry(exc, type_, tb, strtb)

    def handle_failure(self, exc, type_, tb, strtb):
        """Handle exception."""
        if self._store_errors:
            exc = self.task.backend.mark_as_failure(self.task_id, exc, strtb)
        else:
            exc = self.task.backend.prepare_exception(exc)
        return self.super.handle_failure(exc, type_, tb, strtb)


def execute_and_trace(task_name, *args, **kwargs):
    """This is a pickleable method used as a target when applying to pools.

    It's the same as::

        >>> WorkerTaskTrace(task_name, *args, **kwargs).execute_safe()

    """
    hostname = kwargs.get("hostname")
    platforms.set_mp_process_title("celeryd", task_name, hostname=hostname)
    try:
        return WorkerTaskTrace(task_name, *args, **kwargs).execute_safe()
    finally:
        platforms.set_mp_process_title("celeryd", "-idle-", hostname)


class TaskRequest(object):
    """A request for task execution."""

    #: Kind of task.  Must be a name registered in the task registry.
    name = None

    #: The task class (set by constructor using :attr:`task_name`).
    task = None

    #: UUID of the task.
    task_id = None

    #: List of positional arguments to apply to the task.
    args = None

    #: Mapping of keyword arguments to apply to the task.
    kwargs = None

    #: Number of times the task has been retried.
    retries = 0

    #: The tasks eta (for information only).
    eta = None

    #: When the task expires.
    expires = None

    #: Callback called when the task should be acknowledged.
    on_ack = None

    #: The message object.  Used to acknowledge the message.
    message = None

    #: Flag set when the task has been executed.
    executed = False

    #: Additional delivery info, e.g. contains the path from
    #: Producer to consumer.
    delivery_info = None

    #: Flag set when the task has been acknowledged.
    acknowledged = False

    #: Format string used to log task success.
    success_msg = """\
        Task %(name)s[%(id)s] succeeded in %(runtime)ss: %(return_value)s
    """

    #: Format string used to log task failure.
    error_msg = """\
        Task %(name)s[%(id)s] raised exception: %(exc)s\n%(traceback)s
    """

    #: Format string used to log task retry.
    retry_msg = """Task %(name)s[%(id)s] retry: %(exc)s"""

    #: Format string used to generate error e-mail subjects.
    email_subject = """\
        [celery@%(hostname)s] Error: Task %(name)s (%(id)s): %(exc)s
    """

    #: Format string used to generate error e-mail content.
    email_body = TASK_ERROR_EMAIL_BODY

    #: Timestamp set when the task is started.
    time_start = None

    #: Process id of the worker processing this task (if any).
    worker_pid = None

    _already_revoked = False
    _terminate_on_ack = None

    def __init__(self, task_name, task_id, args, kwargs,
            on_ack=noop, retries=0, delivery_info=None, hostname=None,
            email_subject=None, email_body=None, logger=None,
            eventer=None, eta=None, expires=None, app=None, **opts):
        self.app = app_or_default(app)
        self.task_name = task_name
        self.task_id = task_id
        self.retries = retries
        self.args = args
        self.kwargs = kwargs
        self.eta = eta
        self.expires = expires
        self.on_ack = on_ack
        self.delivery_info = delivery_info or {}
        self.hostname = hostname or socket.gethostname()
        self.logger = logger or self.app.log.get_default_logger()
        self.eventer = eventer
        self.email_subject = email_subject or self.email_subject
        self.email_body = email_body or self.email_body

        self.task = tasks[self.task_name]
        self._store_errors = True
        if self.task.ignore_result:
            self._store_errors = self.task.store_errors_even_if_ignored

    @classmethod
    def from_message(cls, message, body, on_ack=noop, **kw):
        """Create request from a task message.

        :raises UnknownTaskError: if the message does not describe a task,
            the message is also rejected.

        """
        _delivery_info = getattr(message, "delivery_info", {})
        delivery_info = dict((key, _delivery_info.get(key))
                                for key in WANTED_DELIVERY_INFO)

        kwargs = body["kwargs"]
        if not hasattr(kwargs, "items"):
            raise InvalidTaskError("Task keyword arguments is not a mapping.")

        return cls(task_name=body["task"],
                   task_id=body["id"],
                   args=body["args"],
                   kwargs=kwdict(kwargs),
                   retries=body.get("retries", 0),
                   eta=maybe_iso8601(body.get("eta")),
                   expires=maybe_iso8601(body.get("expires")),
                   on_ack=on_ack,
                   delivery_info=delivery_info,
                   **kw)

    def get_instance_attrs(self, loglevel, logfile):
        return {"logfile": logfile,
                "loglevel": loglevel,
                "id": self.task_id,
                "retries": self.retries,
                "is_eager": False,
                "delivery_info": self.delivery_info}

    def extend_with_default_kwargs(self, loglevel, logfile):
        """Extend the tasks keyword arguments with standard task arguments.

        Currently these are `logfile`, `loglevel`, `task_id`,
        `task_name`, `task_retries`, and `delivery_info`.

        See :meth:`celery.task.base.Task.run` for more information.

        """
        if not self.task.accept_magic_kwargs:
            return self.kwargs
        kwargs = dict(self.kwargs)
        default_kwargs = {"logfile": logfile,
                          "loglevel": loglevel,
                          "task_id": self.task_id,
                          "task_name": self.task_name,
                          "task_retries": self.retries,
                          "task_is_eager": False,
                          "delivery_info": self.delivery_info}
        fun = self.task.run
        supported_keys = fun_takes_kwargs(fun, default_kwargs)
        extend_with = dict((key, val) for key, val in default_kwargs.items()
                                if key in supported_keys)
        kwargs.update(extend_with)
        return kwargs

    def execute_using_pool(self, pool, loglevel=None, logfile=None):
        """Like :meth:`execute`, but using the :mod:`multiprocessing` pool.

        :param pool: A :class:`multiprocessing.Pool` instance.

        :keyword loglevel: The loglevel used by the task.

        :keyword logfile: The logfile used by the task.

        """
        if self.revoked():
            return
        # Make sure task has not already been executed.
        self._set_executed_bit()

        args = self._get_tracer_args(loglevel, logfile)
        instance_attrs = self.get_instance_attrs(loglevel, logfile)
        result = pool.apply_async(execute_and_trace,
                                  args=args,
                                  kwargs={"hostname": self.hostname,
                                          "request": instance_attrs},
                                  accept_callback=self.on_accepted,
                                  timeout_callback=self.on_timeout,
                                  callbacks=[self.on_success],
                                  errbacks=[self.on_failure])
        return result

    def execute(self, loglevel=None, logfile=None):
        """Execute the task in a :class:`WorkerTaskTrace`.

        :keyword loglevel: The loglevel used by the task.

        :keyword logfile: The logfile used by the task.

        """
        if self.revoked():
            return

        # Make sure task has not already been executed.
        self._set_executed_bit()

        # acknowledge task as being processed.
        if not self.task.acks_late:
            self.acknowledge()

        instance_attrs = self.get_instance_attrs(loglevel, logfile)
        tracer = WorkerTaskTrace(*self._get_tracer_args(loglevel, logfile),
                                 **{"hostname": self.hostname,
                                    "loader": self.app.loader,
                                    "request": instance_attrs})
        retval = tracer.execute()
        self.acknowledge()
        return retval

    def maybe_expire(self):
        """If expired, mark the task as revoked."""
        if self.expires and datetime.now() > self.expires:
            state.revoked.add(self.task_id)
            if self._store_errors:
                self.task.backend.mark_as_revoked(self.task_id)

    def terminate(self, pool, signal=None):
        if self._terminate_on_ack is not None:
            return
        elif self.time_start:
            return pool.terminate_job(self.worker_pid, signal)
        else:
            self._terminate_on_ack = (True, pool, signal)

    def revoked(self):
        """If revoked, skip task and mark state."""
        if self._already_revoked:
            return True
        if self.expires:
            self.maybe_expire()
        if self.task_id in state.revoked:
            self.logger.warn("Skipping revoked task: %s[%s]" % (
                self.task_name, self.task_id))
            self.send_event("task-revoked", uuid=self.task_id)
            self.acknowledge()
            self._already_revoked = True
            return True
        return False

    def send_event(self, type, **fields):
        if self.eventer:
            self.eventer.send(type, **fields)

    def on_accepted(self, pid, time_accepted):
        """Handler called when task is accepted by worker pool."""
        self.worker_pid = pid
        self.time_start = time_accepted
        state.task_accepted(self)
        if not self.task.acks_late:
            self.acknowledge()
        self.send_event("task-started", uuid=self.task_id, pid=pid)
        self.logger.debug("Task accepted: %s[%s] pid:%r" % (
            self.task_name, self.task_id, pid))
        if self._terminate_on_ack is not None:
            _, pool, signal = self._terminate_on_ack
            self.terminate(pool, signal)

    def on_timeout(self, soft):
        """Handler called if the task times out."""
        state.task_ready(self)
        if soft:
            self.logger.warning("Soft time limit exceeded for %s[%s]" % (
                self.task_name, self.task_id))
            exc = SoftTimeLimitExceeded()
        else:
            self.logger.error("Hard time limit exceeded for %s[%s]" % (
                self.task_name, self.task_id))
            exc = TimeLimitExceeded()

        if self._store_errors:
            self.task.backend.mark_as_failure(self.task_id, exc)

    def on_success(self, ret_value):
        """Handler called if the task was successfully processed."""
        state.task_ready(self)

        if self.task.acks_late:
            self.acknowledge()

        runtime = self.time_start and (time.time() - self.time_start) or 0
        self.send_event("task-succeeded", uuid=self.task_id,
                        result=repr(ret_value), runtime=runtime)

        self.logger.info(self.success_msg.strip() % {
                "id": self.task_id,
                "name": self.task_name,
                "return_value": self.repr_result(ret_value),
                "runtime": runtime})

    def on_retry(self, exc_info):
        """Handler called if the task should be retried."""
        self.send_event("task-retried", uuid=self.task_id,
                                        exception=repr(exc_info.exception.exc),
                                        traceback=repr(exc_info.traceback))

        self.logger.info(self.retry_msg.strip() % {
                "id": self.task_id,
                "name": self.task_name,
                "exc": repr(exc_info.exception.exc)})

    def on_failure(self, exc_info):
        """Handler called if the task raised an exception."""
        state.task_ready(self)

        if self.task.acks_late:
            self.acknowledge()

        if isinstance(exc_info.exception, RetryTaskError):
            return self.on_retry(exc_info)

        # This is a special case as the process would not have had
        # time to write the result.
        if isinstance(exc_info.exception, WorkerLostError):
            if self._store_errors:
                self.task.backend.mark_as_failure(self.task_id,
                                                  exc_info.exception)

        self.send_event("task-failed", uuid=self.task_id,
                                       exception=repr(exc_info.exception),
                                       traceback=exc_info.traceback)

        context = {"hostname": self.hostname,
                   "id": self.task_id,
                   "name": self.task_name,
                   "exc": repr(exc_info.exception),
                   "traceback": unicode(exc_info.traceback,
                                        sys.getfilesystemencoding()),
                   "args": self.args,
                   "kwargs": self.kwargs}

        log_with_extra(self.logger, logging.ERROR,
                       self.error_msg.strip() % context,
                       exc_info=exc_info,
                       extra={"data": {"hostname": self.hostname,
                                       "id": self.task_id,
                                       "name": self.task_name}})

        task_obj = tasks.get(self.task_name, object)
        self.send_error_email(task_obj, context, exc_info.exception,
                              enabled=task_obj.send_error_emails,
                              whitelist=task_obj.error_whitelist)

    def acknowledge(self):
        """Acknowledge task."""
        if not self.acknowledged:
            self.on_ack()
            self.acknowledged = True

    def send_error_email(self, task, context, exc,
            whitelist=None, enabled=False, fail_silently=True):
        if enabled and not task.disable_error_emails:
            if whitelist:
                if not isinstance(exc, tuple(whitelist)):
                    return
            subject = self.email_subject.strip() % context
            body = self.email_body.strip() % context
            self.app.mail_admins(subject, body, fail_silently=fail_silently)

    def repr_result(self, result, maxlen=46):
        # 46 is the length needed to fit
        #     "the quick brown fox jumps over the lazy dog" :)
        return truncate_text(repr(result), maxlen)

    def info(self, safe=False):
        args = self.args
        kwargs = self.kwargs
        if not safe:
            args = repr(args)
            kwargs = repr(self.kwargs)

        return {"id": self.task_id,
                "name": self.task_name,
                "args": args,
                "kwargs": kwargs,
                "hostname": self.hostname,
                "time_start": self.time_start,
                "acknowledged": self.acknowledged,
                "delivery_info": self.delivery_info}

    def shortinfo(self):
        return "%s[%s]%s%s" % (
                    self.task_name,
                    self.task_id,
                    self.eta and " eta:[%s]" % (self.eta, ) or "",
                    self.expires and " expires:[%s]" % (self.expires, ) or "")

    def __repr__(self):
        return '<%s: {name:"%s", id:"%s", args:"%s", kwargs:"%s"}>' % (
                self.__class__.__name__,
                self.task_name, self.task_id, self.args, self.kwargs)

    def _get_tracer_args(self, loglevel=None, logfile=None):
        """Get the :class:`WorkerTaskTrace` tracer for this task."""
        task_func_kwargs = self.extend_with_default_kwargs(loglevel, logfile)
        return self.task_name, self.task_id, self.args, task_func_kwargs

    def _set_executed_bit(self):
        """Set task as executed to make sure it's not executed again."""
        if self.executed:
            raise AlreadyExecutedError(
                   "Task %s[%s] has already been executed" % (
                       self.task_name, self.task_id))
        self.executed = True
