from __future__ import annotations

from abc import ABC, abstractmethod
from contextlib import ExitStack, contextmanager
from functools import partial
from typing import TYPE_CHECKING, Callable, Dict

import torch
from diffusers import UNet2DConditionModel

if TYPE_CHECKING:
    from invokeai.backend.stable_diffusion.denoise_context import DenoiseContext
    from invokeai.backend.stable_diffusion.extensions import ExtensionBase


class ExtCallbacksApi(ABC):
    @abstractmethod
    def setup(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
        pass

    @abstractmethod
    def pre_denoise_loop(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
        pass

    @abstractmethod
    def post_denoise_loop(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
        pass

    @abstractmethod
    def pre_step(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
        pass

    @abstractmethod
    def post_step(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
        pass

    @abstractmethod
    def pre_unet(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
        pass

    @abstractmethod
    def post_unet(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
        pass

    @abstractmethod
    def post_apply_cfg(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
        pass


class ProxyCallsClass:
    def __init__(self, handler):
        self._handler = handler

    def __getattr__(self, item):
        return partial(self._handler, item)


class CallbackInjectionPoint:
    def __init__(self):
        self.handlers = {}

    def add(self, func: Callable, order: int):
        if order not in self.handlers:
            self.handlers[order] = []
        self.handlers[order].append(func)

    def __call__(self, *args, **kwargs):
        for order in sorted(self.handlers.keys(), reverse=True):
            for handler in self.handlers[order]:
                handler(*args, **kwargs)


class ExtensionsManager:
    def __init__(self):
        self.extensions = []

        self._callbacks = {}
        self.callbacks: ExtCallbacksApi = ProxyCallsClass(self.call_callback)

    def add_extension(self, ext: ExtensionBase):
        self.extensions.append(ext)

        self._callbacks.clear()

        for ext in self.extensions:
            for inj_info in ext.injections:
                if inj_info.type == "callback":
                    if inj_info.name not in self._callbacks:
                        self._callbacks[inj_info.name] = CallbackInjectionPoint()
                    self._callbacks[inj_info.name].add(inj_info.function, inj_info.order)

                else:
                    raise Exception(f"Unsupported injection type: {inj_info.type}")

    def call_callback(self, name: str, *args, **kwargs):
        if name in self._callbacks:
            self._callbacks[name](*args, **kwargs)

    @contextmanager
    def patch_extensions(self, context: DenoiseContext):
        with ExitStack() as exit_stack:
            for ext in self.extensions:
                exit_stack.enter_context(ext.patch_extension(context))

            yield None

    @contextmanager
    def patch_unet(self, state_dict: Dict[str, torch.Tensor], unet: UNet2DConditionModel):
        # TODO: create logic in PR with extension which uses it
        yield None