import functools
import threading

from .composition import parse_composition, parse_heads_from_composition


class AdapterSetup:
    """
    Represents an adapter setup of a model including active adapters and active heads. This class is intended to be
    used as a context manager using the ``with`` statement. The setup defined by the ``AdapterSetup`` context will
    override static adapter setups defined in a model (i.e. setups specified via ``active_adapters``).

    Example::

        with AdapterSetup(Stack("a", "b")):
            # will use the adapter stack "a" and "b" outputs = model(**inputs)

    Note that the context manager is thread-local, i.e. it can be used with different setups in a multi-threaded
    environment.
    """

    # thread-local storage that holds a stack of active contexts
    storage = threading.local()

    def __init__(self, adapter_setup, head_setup=None, ignore_empty: bool = False):
        self.adapter_setup = parse_composition(adapter_setup)
        if head_setup:
            self.head_setup = head_setup
        else:
            self.head_setup = parse_heads_from_composition(self.adapter_setup)
        self._empty = ignore_empty and self.adapter_setup is None and self.head_setup is None

    def __enter__(self):
        if not self._empty:
            AdapterSetup.get_contexts().append(self)
        return self

    def __exit__(self, type, value, traceback):
        if not self._empty:
            AdapterSetup.get_contexts().pop()

    @classmethod
    def get_contexts(cls):
        if not hasattr(cls.storage, "contexts"):
            cls.storage.contexts = []
        return cls.storage.contexts

    @classmethod
    def get_context(cls):
        try:
            return cls.get_contexts()[-1]
        except IndexError:
            return None

    @classmethod
    def get_context_adapter_setup(cls):
        context = cls.get_context()
        if context:
            return context.adapter_setup
        return None

    @classmethod
    def get_context_head_setup(cls):
        context = cls.get_context()
        if context:
            return context.head_setup
        return None


class ForwardContext:
    """
    Holds context information during a forward pass through a model. This class should be used via the
    ``ForwardContext.wrap()`` method.

    Note that the context is thread-local.
    """

    # thread-local storage that holds a stack of active contexts
    storage = threading.local()

    context_attributes = ["adapter_gating_scores", "adapter_fusion_attentions", "adapter_input_parallelized"]

    def __init__(self, model, *args, **kwargs):
        # If the model has a method ``forward_context()``, use it to create the context.
        if hasattr(model, "forward_context"):
            model.forward_context(self, *args, **kwargs)

    def __enter__(self):
        ForwardContext.get_contexts().append(self)
        return self

    def __exit__(self, type, value, traceback):
        ForwardContext.get_contexts().pop()

    @classmethod
    def wrap(cls, f):
        """
        Decorator method that wraps a ``forward()`` function of a model class.
        """

        @functools.wraps(f)
        def wrapper_func(self, *args, **kwargs):
            if self.config.adapters is not None:
                with cls(self, *args, **kwargs) as ctx:
                    kwargs = {
                        k: v for k, v in kwargs.items() if k.replace("output_", "") not in cls.context_attributes
                    }
                    results = f(self, *args, **kwargs)

                    # append output attributes
                    if isinstance(results, tuple):
                        for attr in cls.context_attributes:
                            if getattr(ctx, "output_" + attr, False):
                                results = results + (dict(getattr(ctx, attr)),)
                    else:
                        for attr in cls.context_attributes:
                            if getattr(ctx, "output_" + attr, False):
                                results[attr] = dict(getattr(ctx, attr))
                return results
            else:
                return f(self, *args, **kwargs)

        return wrapper_func

    @classmethod
    def get_contexts(cls):
        if not hasattr(cls.storage, "contexts"):
            cls.storage.contexts = []
        return cls.storage.contexts

    @classmethod
    def get_context(cls):
        try:
            return cls.get_contexts()[-1]
        except IndexError:
            return None
