"""
    celery.canvas
    ~~~~~~~~~~~~~

    Designing task workflows.

    :copyright: (c) 2009 - 2012 by Ask Solem.
    :license: BSD, see LICENSE for more details.

"""
from __future__ import absolute_import

from itertools import chain as _chain

from kombu.utils import kwdict, reprcall

from celery import current_app
from celery.local import Proxy
from celery.utils import cached_property, uuid
from celery.utils.functional import maybe_list
from celery.utils.compat import chain_from_iterable

Chord = Proxy(lambda: current_app.tasks["celery.chord"])


class _getitem_property(object):

    def __init__(self, key):
        self.key = key

    def __get__(self, obj, type=None):
        if obj is None:
            return type
        return obj[self.key]

    def __set__(self, obj, value):
        obj[self.key] = value


class Signature(dict):
    """Class that wraps the arguments and execution options
    for a single task invocation.

    Used as the parts in a :class:`group` or to safely
    pass tasks around as callbacks.

    :param task: Either a task class/instance, or the name of a task.
    :keyword args: Positional arguments to apply.
    :keyword kwargs: Keyword arguments to apply.
    :keyword options: Additional options to :meth:`Task.apply_async`.

    Note that if the first argument is a :class:`dict`, the other
    arguments will be ignored and the values in the dict will be used
    instead.

        >>> s = subtask("tasks.add", args=(2, 2))
        >>> subtask(s)
        {"task": "tasks.add", args=(2, 2), kwargs={}, options={}}

    """
    TYPES = {}
    _type = None

    @classmethod
    def register_type(cls, subclass, name=None):
        cls.TYPES[name or subclass.__name__] = subclass
        return subclass

    @classmethod
    def from_dict(self, d):
        typ = d.get("subtask_type")
        if typ:
            return self.TYPES[typ].from_dict(d)
        return Signature(d)

    def __init__(self, task=None, args=None, kwargs=None, options=None,
                type=None, subtask_type=None, **ex):
        init = dict.__init__

        if isinstance(task, dict):
            return init(self, task)  # works like dict(d)

        # Also supports using task class/instance instead of string name.
        try:
            task_name = task.name
        except AttributeError:
            task_name = task
        else:
            self._type = task

        init(self, task=task_name, args=tuple(args or ()),
                                   kwargs=kwargs or {},
                                   options=dict(options or {}, **ex),
                                   subtask_type=subtask_type)

    def delay(self, *argmerge, **kwmerge):
        """Shortcut to `apply_async(argmerge, kwargs)`."""
        return self.apply_async(args=argmerge, kwargs=kwmerge)

    def apply(self, args=(), kwargs={}, **options):
        """Apply this task locally."""
        # For callbacks: extra args are prepended to the stored args.
        args, kwargs, options = self._merge(args, kwargs, options)
        return self.type.apply(args, kwargs, **options)

    def _merge(self, args=(), kwargs={}, options={}):
        return (tuple(args) + tuple(self.args),
                dict(self.kwargs, **kwargs),
                dict(self.options, **options))

    def clone(self, args=(), kwargs={}, **options):
        args, kwargs, options = self._merge(args, kwargs, options)
        s = self.from_dict({"task": self.task, "args": args,
                            "kwargs": kwargs, "options": options,
                            "subtask_type": self.subtask_type})
        s._type = self._type
        return s
    partial = clone

    def replace(self, args=None, kwargs=None, options=None):
        s = self.clone()
        if args is not None:
            s.args = args
        if kwargs is not None:
            s.kwargs = kwargs
        if options is not None:
            s.options = options
        return s

    def set(self, **options):
        self.options.update(options)
        return self

    def apply_async(self, args=(), kwargs={}, **options):
        """Apply this task asynchronously."""
        # For callbacks: extra args are prepended to the stored args.
        args, kwargs, options = self._merge(args, kwargs, options)
        return self.type.apply_async(args, kwargs, **options)

    def append_to_list_option(self, key, value):
        items = self.options.setdefault(key, [])
        if value not in items:
            items.append(value)
        return value

    def link(self, callback):
        """Add a callback task to be applied if this task
        executes successfully."""
        return self.append_to_list_option("link", callback)

    def link_error(self, errback):
        """Add a callback task to be applied if an error occurs
        while executing this task."""
        return self.append_to_list_option("link_error", errback)

    def flatten_links(self):
        """Gives a recursive list of dependencies (unchain if you will,
        but with links intact)."""
        return list(chain_from_iterable(_chain([[self]],
                (link.flatten_links()
                    for link in maybe_list(self.options.get("link")) or []))))

    def __or__(self, other):
        if isinstance(other, chain):
            return chain(*self.tasks + other.tasks)
        elif isinstance(other, Signature):
            if isinstance(self, chain):
                return chain(*self.tasks + (other, ))
            return chain(self, other)
        return NotImplemented

    def __invert__(self):
        return self.apply_async().get()

    def __reduce__(self):
        # for serialization, the task type is lazily loaded,
        # and not stored in the dict itself.
        return subtask, (dict(self), )

    def reprcall(self, *args, **kwargs):
        args, kwargs, _ = self._merge(args, kwargs, {})
        return reprcall(self["task"], args, kwargs)

    def __repr__(self):
        return self.reprcall()

    @cached_property
    def type(self):
        return self._type or current_app.tasks[self.task]
    task = _getitem_property("task")
    args = _getitem_property("args")
    kwargs = _getitem_property("kwargs")
    options = _getitem_property("options")
    subtask_type = _getitem_property("subtask_type")


class chain(Signature):

    def __init__(self, *tasks, **options):
        Signature.__init__(self, "celery.chain", (), {"tasks": tasks}, options)
        self.tasks = tasks
        self.subtask_type = "chain"

    @classmethod
    def from_dict(self, d):
        return chain(*d["kwargs"]["tasks"], **kwdict(d["options"]))

    def __repr__(self):
        return " | ".join(map(repr, self.tasks))
Signature.register_type(chain)


class group(Signature):

    def __init__(self, tasks, **options):
        self.tasks = tasks = [maybe_subtask(t) for t in tasks]
        Signature.__init__(self, "celery.group", (), {"tasks": tasks}, options)
        self.subtask_type = "group"

    @classmethod
    def from_dict(self, d):
        return group(d["kwargs"]["tasks"], **kwdict(d["options"]))

    def __call__(self, **options):
        tasks, result = self.type.prepare(options,
                                map(Signature.clone, self.tasks))
        return self.type(tasks, result)

    def __repr__(self):
        return repr(self.tasks)
Signature.register_type(group)


class chord(Signature):
    Chord = Chord

    def __init__(self, header, body=None, **options):
        Signature.__init__(self, "celery.chord", (),
                         {"header": list(header),
                          "body": maybe_subtask(body)}, options)
        self.subtask_type = "chord"

    @classmethod
    def from_dict(self, d):
        kwargs = d["kwargs"]
        return chord(kwargs["header"], kwargs.get("body"),
                     **kwdict(d["options"]))

    def __call__(self, body=None, **options):
        _chord = self.Chord
        self.kwargs["body"] = body or self.kwargs["body"]
        if _chord.app.conf.CELERY_ALWAYS_EAGER:
            return _chord.apply((), self.kwargs)
        callback_id = body.options.setdefault("task_id", uuid())
        _chord(**self.kwargs)
        return _chord.AsyncResult(callback_id)

    def clone(self, *args, **kwargs):
        s = Signature.clone(self, *args, **kwargs)
        # need to make copy of body
        try:
            s.kwargs["body"] = s.kwargs["body"].clone()
        except (AttributeError, KeyError):
            pass
        return s

    def link(self, callback):
        self.body.link(callback)
        return callback

    def link_error(self, errback):
        self.body.link_error(errback)
        return errback

    def __repr__(self):
        if self.body:
            return self.body.reprcall(self.tasks)
        return "<chord without body: %r>" % (self.tasks, )

    @property
    def tasks(self):
        return self.kwargs["header"]

    @property
    def body(self):
        return self.kwargs.get("body")
Signature.register_type(chord)


def subtask(varies, *args, **kwargs):
    if not (args or kwargs) and isinstance(varies, dict):
        if isinstance(varies, Signature):
            return varies.clone()
        return Signature.from_dict(varies)
    return Signature(varies, *args, **kwargs)


def maybe_subtask(d):
    return subtask(d) if d is not None and not isinstance(d, Signature) else d