# -*- coding: utf-8 -*-
"""
    celery.contrib.migrate
    ~~~~~~~~~~~~~~~~~~~~~~

    Migration tools.

"""
from __future__ import absolute_import
from __future__ import with_statement

import socket

from functools import partial
from itertools import cycle, islice

from kombu import eventloop, Queue
from kombu.common import maybe_declare
from kombu.exceptions import StdChannelError
from kombu.utils.encoding import ensure_bytes

from celery.app import app_or_default
from celery.utils import worker_direct


class StopFiltering(Exception):
    pass


class State(object):
    count = 0
    filtered = 0
    total_apx = 0

    @property
    def strtotal(self):
        if not self.total_apx:
            return u'?'
        return unicode(self.total_apx)

    def __repr__(self):
        if self.filtered:
            return '^%s' % self.filtered
        return '%s/%s' % (self.count, self.strtotal)


def republish(producer, message, exchange=None, routing_key=None,
              remove_props=['application_headers',
                            'content_type',
                            'content_encoding',
                            'headers']):
    body = ensure_bytes(message.body)  # use raw message body.
    info, headers, props = (message.delivery_info,
                            message.headers, message.properties)
    exchange = info['exchange'] if exchange is None else exchange
    routing_key = info['routing_key'] if routing_key is None else routing_key
    ctype, enc = message.content_type, message.content_encoding
    # remove compression header, as this will be inserted again
    # when the message is recompressed.
    compression = headers.pop('compression', None)

    for key in remove_props:
        props.pop(key, None)

    producer.publish(ensure_bytes(body), exchange=exchange,
                     routing_key=routing_key, compression=compression,
                     headers=headers, content_type=ctype,
                     content_encoding=enc, **props)


def migrate_task(producer, body_, message, queues=None):
    info = message.delivery_info
    queues = {} if queues is None else queues
    republish(producer, message,
              exchange=queues.get(info['exchange']),
              routing_key=queues.get(info['routing_key']))


def filter_callback(callback, tasks):

    def filtered(body, message):
        if tasks and message.payload['task'] not in tasks:
            return

        return callback(body, message)
    return filtered


def migrate_tasks(source, dest, migrate=migrate_task, app=None,
                  queues=None, **kwargs):
    app = app_or_default(app)
    queues = prepare_queues(queues)
    producer = app.amqp.TaskProducer(dest)
    migrate = partial(migrate, producer, queues=queues)

    def on_declare_queue(queue):
        new_queue = queue(producer.channel)
        new_queue.name = queues.get(queue.name, queue.name)
        if new_queue.routing_key == queue.name:
            new_queue.routing_key = queues.get(queue.name,
                                               new_queue.routing_key)
        if new_queue.exchange.name == queue.name:
            new_queue.exchange.name = queues.get(queue.name, queue.name)
        new_queue.declare()

    return start_filter(app, source, migrate, queues=queues,
                        on_declare_queue=on_declare_queue, **kwargs)


def _maybe_queue(app, q):
    if isinstance(q, basestring):
        return app.amqp.queues[q]
    return q


def move(predicate, connection=None, exchange=None, routing_key=None,
         source=None, app=None, callback=None, limit=None, transform=None,
         **kwargs):
    """Find tasks by filtering them and move the tasks to a new queue.

    :param predicate: Filter function used to decide which messages
        to move.  Must accept the standard signature of ``(body, message)``
        used by Kombu consumer callbacks. If the predicate wants the message
        to be moved it must return either:

            1) a tuple of ``(exchange, routing_key)``, or

            2) a :class:`~kombu.entity.Queue` instance, or

            3) any other true value which means the specified
               ``exchange`` and ``routing_key`` arguments will be used.

    :keyword connection: Custom connection to use.
    :keyword source: Optional list of source queues to use instead of the
        default (which is the queues in :setting:`CELERY_QUEUES`).
        This list can also contain new :class:`~kombu.entity.Queue` instances.
    :keyword exchange: Default destination exchange.
    :keyword routing_key: Default destination routing key.
    :keyword limit: Limit number of messages to filter.
    :keyword callback: Callback called after message moved,
        with signature ``(state, body, message)``.
    :keyword transform: Optional function to transform the return
        value (destination) of the filter function.

    Also supports the same keyword arguments as :func:`start_filter`.

    To demonstrate, the :func:`move_task_by_id` operation can be implemented
    like this:

    .. code-block:: python

        def is_wanted_task(body, message):
            if body['id'] == wanted_id:
                return Queue('foo', exchange=Exchange('foo'),
                             routing_key='foo')

        move(is_wanted_task)

    or with a transform:

    .. code-block:: python

        def transform(value):
            if isinstance(value, basestring):
                return Queue(value, Exchange(value), value)
            return value

        move(is_wanted_task, transform=transform)

    The predicate may also return a tuple of ``(exchange, routing_key)``
    to specify the destination to where the task should be moved,
    or a :class:`~kombu.entitiy.Queue` instance.
    Any other true value means that the task will be moved to the
    default exchange/routing_key.

    """
    app = app_or_default(app)
    queues = [_maybe_queue(app, queue) for queue in source or []] or None
    with app.connection_or_acquire(connection, pool=False) as conn:
        producer = app.amqp.TaskProducer(conn)
        state = State()

        def on_task(body, message):
            ret = predicate(body, message)
            if ret:
                if transform:
                    ret = transform(ret)
                if isinstance(ret, Queue):
                    maybe_declare(ret, conn.default_channel)
                    ex, rk = ret.exchange.name, ret.routing_key
                else:
                    ex, rk = expand_dest(ret, exchange, routing_key)
                republish(producer, message,
                          exchange=ex, routing_key=rk)
                message.ack()

                state.filtered += 1
                if callback:
                    callback(state, body, message)
                if limit and state.filtered >= limit:
                    raise StopFiltering()

        return start_filter(app, conn, on_task, consume_from=queues, **kwargs)


def expand_dest(ret, exchange, routing_key):
    try:
        ex, rk = ret
    except (TypeError, ValueError):
        ex, rk = exchange, routing_key
    return ex, rk


def task_id_eq(task_id, body, message):
    return body['id'] == task_id


def task_id_in(ids, body, message):
    return body['id'] in ids


def prepare_queues(queues):
    if isinstance(queues, basestring):
        queues = queues.split(',')
    if isinstance(queues, list):
        queues = dict(tuple(islice(cycle(q.split(':')), None, 2))
                      for q in queues)
    if queues is None:
        queues = {}
    return queues


def start_filter(app, conn, filter, limit=None, timeout=1.0,
                 ack_messages=False, tasks=None, queues=None,
                 callback=None, forever=False, on_declare_queue=None,
                 consume_from=None, state=None, **kwargs):
    state = state or State()
    queues = prepare_queues(queues)
    if isinstance(tasks, basestring):
        tasks = set(tasks.split(','))
    if tasks is None:
        tasks = set([])

    def update_state(body, message):
        state.count += 1
        if limit and state.count >= limit:
            raise StopFiltering()

    def ack_message(body, message):
        message.ack()

    consumer = app.amqp.TaskConsumer(conn, queues=consume_from)

    if tasks:
        filter = filter_callback(filter, tasks)
        update_state = filter_callback(update_state, tasks)
        ack_message = filter_callback(ack_message, tasks)

    consumer.register_callback(filter)
    consumer.register_callback(update_state)
    if ack_messages:
        consumer.register_callback(ack_message)
    if callback is not None:
        callback = partial(callback, state)
        if tasks:
            callback = filter_callback(callback, tasks)
        consumer.register_callback(callback)

    # declare all queues on the new broker.
    for queue in consumer.queues:
        if queues and queue.name not in queues:
            continue
        if on_declare_queue is not None:
            on_declare_queue(queue)
        try:
            _, mcount, _ = queue(consumer.channel).queue_declare(passive=True)
            if mcount:
                state.total_apx += mcount
        except conn.channel_errors + (StdChannelError, ):
            pass

    # start migrating messages.
    with consumer:
        try:
            for _ in eventloop(conn,  # pragma: no cover
                               timeout=timeout, ignore_timeouts=forever):
                pass
        except socket.timeout:
            pass
        except StopFiltering:
            pass
    return state


def move_task_by_id(task_id, dest, **kwargs):
    """Find a task by id and move it to another queue.

    :param task_id: Id of task to move.
    :param dest: Destination queue.

    Also supports the same keyword arguments as :func:`move`.

    """
    return move_by_idmap({task_id: dest}, **kwargs)


def move_by_idmap(map, **kwargs):
    """Moves tasks by matching from a ``task_id: queue`` mapping,
    where ``queue`` is a queue to move the task to.

    Example::

        >>> reroute_idmap({
        ...     '5bee6e82-f4ac-468e-bd3d-13e8600250bc': Queue(...),
        ...     'ada8652d-aef3-466b-abd2-becdaf1b82b3': Queue(...),
        ...     '3a2b140d-7db1-41ba-ac90-c36a0ef4ab1f': Queue(...)},
        ...   queues=['hipri'])

    """
    def task_id_in_map(body, message):
        return map.get(body['id'])

    # adding the limit means that we don't have to consume any more
    # when we've found everything.
    return move(task_id_in_map, limit=len(map), **kwargs)


def move_by_taskmap(map, **kwargs):
    """Moves tasks by matching from a ``task_name: queue`` mapping,
    where ``queue`` is the queue to move the task to.

    Example::

        >>> reroute_idmap({
        ...     'tasks.add': Queue(...),
        ...     'tasks.mul': Queue(...),
        ... })

    """

    def task_name_in_map(body, message):
        return map.get(body['task'])  # <- name of task

    return move(task_name_in_map, **kwargs)


move_direct = partial(move, transform=worker_direct)
move_direct_by_id = partial(move_task_by_id, transform=worker_direct)
move_direct_by_idmap = partial(move_by_idmap, transform=worker_direct)
move_direct_by_taskmap = partial(move_by_taskmap, transform=worker_direct)


def filter_status(state, body, message):
    print('Moving task %s/%s: %s[%s]' % (
        state.filtered, state.strtotal, body['task'], body['id']))
