import inspect
from functools import partial
from typing import Any, List, Optional, Union

import matplotlib.cm as cm
import matplotlib.pyplot as plt
import numpy as np
import tensorflow as tf
import tensorflow_addons as tfa
from PIL import Image
from tensorflow import keras
from tensorflow.keras.models import Model
from tf_keras_vis.gradcam import Gradcam, GradcamPlusPlus
from tf_keras_vis.utils import normalize
from typeguard import check_argument_types, typechecked

from chitra.import_utils import is_installed

from .datagenerator import Dataset

pl = None
if is_installed("pytorch_lightning"):
    import pytorch_lightning as pl

MODEL_DICT = {}
for name, func in inspect.getmembers(tf.keras.applications):
    if inspect.isfunction(func):
        MODEL_DICT[name.lower()] = func

OPT_DICT = {}
for name, func in inspect.getmembers(tf.keras.optimizers):
    if inspect.isclass(func):
        OPT_DICT[name.lower()] = func


@typechecked
def _get_base_cnn(
    base_model: Union[str, Model],
    pooling: str = "avg",
    weights: Union[str, None] = "imagenet",
    include_top: bool = False,
) -> Model:
    if isinstance(base_model, str):
        if base_model not in MODEL_DICT.keys():
            raise AssertionError(f"base_model name must be in {tuple(MODEL_DICT.keys())}")
        base_model = MODEL_DICT[base_model]
        base_model = base_model(include_top=include_top, pooling=pooling, weights=weights)
    return base_model


@typechecked
def _add_output_layers(
    base_model: Model,
    outputs: int,
    drop_out: Union[float, None] = None,
    name: Optional[str] = None,
) -> Model:
    x = base_model.output
    if drop_out:
        x = tf.keras.layers.Dropout(drop_out)(x)
    x = tf.keras.layers.Dense(outputs, name="output")(x)

    model = tf.keras.Model(base_model.input, x, name=name)
    return model


def create_classifier(
    base_model_fn: callable,
    num_classes: int,
    weights="imagenet",
    dropout: Optional[float] = None,
    include_top=False,
):
    base_model = base_model_fn(
        include_top=include_top,
        weights=weights,
    )
    if include_top:
        return base_model

    outputs = 1 if num_classes == 2 else num_classes

    x = base_model.output
    x = tf.keras.layers.GlobalMaxPool2D()(x)
    if dropout:
        x = tf.keras.layers.Dropout(dropout)(x)
    x = tf.keras.layers.Dense(outputs, name="output")(x)

    model = tf.keras.Model(base_model.input, x)
    return model


@typechecked
def create_cnn(
    base_model: Union[str, Model],
    num_classes: int,
    drop_out=0.5,
    keras_applications: bool = True,
    pooling: str = "avg",
    weights: Union[str, None] = "imagenet",
    name: Optional[str] = None,
) -> Model:
    assert pooling in ("avg", "max")

    if keras_applications:
        if num_classes == 2:
            outputs = 1
        else:
            outputs = num_classes
    else:
        print("num_classes is ignored. returning the passed model as it is.")

    if isinstance(base_model, (str, Model)) and keras_applications:
        base_model = _get_base_cnn(base_model, pooling=pooling, weights=weights)
        if "pool" not in base_model.layers[-1].name:
            raise AssertionError("base_model last layer must be a pooling layer")
        model = _add_output_layers(base_model, outputs, drop_out=drop_out, name=name)

    elif isinstance(base_model, Model) and keras_applications is False:
        model = base_model

    elif isinstance(base_model, str) and keras_applications is False:
        model = _get_base_cnn(base_model, weights="imagenet", include_top=True)

    else:
        print("Invalid arguments!")
    return model


class Trainer(Model):
    """The Trainer class inherits tf.keras.Model and contains everything a
    model needs for training. It exposes trainer.cyclic_fit method which trains
    the model using Cyclic Learning rate discovered by Leslie Smith.

    Arguments:
    ds: Dataset object
    model: object of type tf.keras.Model
    num_classes (int, None): number of classes in the dataset. If None then will auto infer from Dataset
    """

    _AUTOTUNE = tf.data.experimental.AUTOTUNE

    @typechecked
    def __init__(self, ds: Dataset, model: Model, num_classes: Union[int, None] = None, **kwargs):
        assert check_argument_types()

        super(Trainer, self).__init__()
        self.ds = ds
        self.total = len(ds)
        if num_classes:
            self.NUM_CLASSES = num_classes
        else:
            self.NUM_CLASSES = ds.NUM_CLASSES
        self.gradcam = None
        self.model = model
        self.cyclic_opt_set = False
        self.max_lr, self.min_lr = None, None
        self.batch_size = None
        self.step_size = None

    def build(self):
        raise NotImplementedError('Build method is not implemented in Trainer! Please use "model.model.build" instead.')

    def summary(self):
        return self.model.summary()

    def compile(self, *args, **kwargs):
        return self.model.compile(*args, **kwargs)

    def call(self, *args, **kwargs):
        return self.model.call(*args, **kwargs)

    def fit(self, *args, **kwargs):
        return self.model.fit(*args, **kwargs)

    def warmup(self):
        raise NotImplementedError("warmup is not implemented yet! Would you like to raise a PR to chitra?")

    @staticmethod
    def prewhiten(image):
        image = tf.cast(image, tf.float32)
        image = image / 127.5 - 1.0
        return image

    def rescale(self, image, label):
        image = self.prewhiten(image)
        return image, label

    def _get_optimizer(self, optimizer, momentum=0.9, **kwargs):
        if optimizer.__name__ == "SGD":
            optimizer = partial(optimizer, momentum=momentum, nesterov=kwargs.get("nesterov", True))
        else:
            optimizer = partial(
                optimizer,
            )
        return optimizer

    def _prepare_dl(self, bs: int = 8, shuffle: bool = True):
        ds = self.ds
        dl = ds.get_tf_dataset(shuffle=shuffle)
        dl = dl.map(self.rescale, Trainer._AUTOTUNE)
        return dl.batch(bs).prefetch(Trainer._AUTOTUNE)

    def cyclic_fit(
        self,
        epochs: int,
        batch_size: int,
        lr_range: Union[tuple, list] = (1e-4, 1e-2),
        optimizer: tf.keras.optimizers.Optimizer = tf.keras.optimizers.SGD,
        momentum: float = 0.9,
        validation_data: Any = None,
        callbacks: Optional[List] = None,
        *args,
        **kwargs,
    ):
        """Trains model on ds as train data with cyclic learning rate. Dataset
        will be automatically converted into `tf.data` format and images will
        be prewhitened in range of [-1, 1]. Cyclical Learning Rates for
        Training Neural Networks: https://arxiv.org/abs/1506.01186.

        Args:
            epochs (int): number of epochs for training
            batch_size (int): batch size
            lr_range (tuple): learning rate will cycle from lr_min to lr_max
            optimizer (callable): Keras callable optimizer
            momentum(float): momentum for the optimizer
            validation_data: Data on which to evaluate
            callbacks: List of `tf.keras.callbacks` instances.
        kwargs:
            step_size (int): step size for the Cyclic learning rate.
            By default it is `2 * (self.ds.num_files//batch_size)`
            scale_mode (str): cycle or exp
            shuffle(bool): Dataset will be shuffle on each epoch if True
        """
        self.step_size = 2 * (self.ds.num_files // batch_size)
        self.ds.step_size = self.step_size
        if not self.cyclic_opt_set:
            self.max_lr, self.min_lr = lr_range
            lr_schedule = tfa.optimizers.Triangular2CyclicalLearningRate(
                initial_learning_rate=lr_range[0],
                maximal_learning_rate=lr_range[1],
                step_size=kwargs.get("step_size", self.step_size),
                scale_mode=kwargs.get("scale_mode", "cycle"),
            )

            optimizer = self._get_optimizer(optimizer, momentum=momentum)
            optimizer = optimizer(learning_rate=lr_schedule)
            self.model.optimizer = optimizer
            self.cyclic_opt_set = True
        else:
            print("cyclic learning rate already set!")

        return self.model.fit(
            self._prepare_dl(batch_size, kwargs.get("shuffle", True)),
            steps_per_epoch=self.step_size,
            validation_data=validation_data,
            epochs=epochs,
            callbacks=callbacks,
        )

    @typechecked
    def compile2(
        self,
        batch_size: int,
        optimizer: Union[None, str, tf.keras.optimizers.Optimizer] = None,
        lr_range: Union[tuple, list] = (1e-4, 1e-2),
        loss: Optional[tf.keras.losses.Loss] = None,
        metrics=None,
        **kwargs,
    ):
        """Compile2 compiles the model of Trainer for cyclic learning rate.
        Cyclical Learning Rates for Training Neural Networks:
        https://arxiv.org/abs/1506.01186.

        Args:
            batch_size (int): batch size
            lr_range (tuple): learning rate will cycle from lr_min to lr_max
            optimizer (str, keras.optimizer.Optimizer): Keras optimizer

        kwargs:
            step_size (int): step size for the Cyclic learning rate.
            By default it is `2 * (self.ds.num_files // batch_size)`
            scale_mode (str): cycle or exp
            momentum(int): momentum for the optimizer when optimizer is of type str
        """
        if not optimizer:
            optimizer = "adam"
        self.max_lr, self.min_lr = lr_range
        self.batch_size = batch_size

        self.step_size = 2 * (self.ds.num_files // batch_size)

        lr_schedule = tfa.optimizers.Triangular2CyclicalLearningRate(
            initial_learning_rate=lr_range[0],
            maximal_learning_rate=lr_range[1],
            step_size=kwargs.get("step_size", self.step_size),
            scale_mode=kwargs.get("scale_mode", "cycle"),
        )

        if isinstance(optimizer, str):
            optimizer = OPT_DICT[optimizer]
            optimizer = optimizer(learning_rate=lr_schedule)
            if kwargs.get("momentum"):
                optimizer.momentum = kwargs.get("momentum")

        else:
            optimizer.learning_rate = lr_schedule

        self.compile(optimizer=optimizer, loss=loss, metrics=metrics)
        self.cyclic_opt_set = True
        print("Model compiled!")


class InterpretModel:
    def __init__(self, gradcam_pp: bool, learner: Trainer, clone: bool = False):
        """Args:
        gradcam_pp: if True GradCam class will be used else GradCamPlusplus
        clone: whether GradCam will clone learner.model
        """
        if gradcam_pp:
            self.gradcam_fn = GradcamPlusPlus
        else:
            self.gradcam_fn = Gradcam
        self.learner = learner

        self.gradcam = self.gradcam_fn(learner.model, self.model_modifier, clone=clone)

    def __call__(self, image: Image.Image, auto_resize: bool = True, image_size=None) -> None:
        gradcam = self.gradcam
        get_loss = self.get_loss
        if auto_resize and image_size is None:
            image_size = self.learner.ds.img_sz_list.get_size()
        if image_size:
            image = image.resize(image_size)

        X = np.asarray(image, np.float32)
        X = self.learner.prewhiten(X)
        X = np.expand_dims(X, 0)

        cam = gradcam(
            get_loss,
            X,
            penultimate_layer=-1,  # model.layers number
            seek_penultimate_conv_layer=True,
        )
        cam = normalize(cam)
        heatmap = np.uint8(cm.jet(cam[0])[..., :3] * 255)
        plt.imshow(image)
        plt.imshow(heatmap, cmap="jet", alpha=0.5)
        plt.show()

    @staticmethod
    def model_modifier(m):
        """Sets last activation to linear."""
        m.layers[-1].activation = tf.keras.activations.linear
        return m

    def get_loss(self, preds):
        if self.learner.NUM_CLASSES == 2:
            ret = preds[0]
        else:
            index = tf.argmax(tf.math.softmax(preds), axis=1)[0]
            ret = preds[0, index]
            print(f"index: {index}")
        return ret


class Learner:
    TF = ("TF", "TENSORFLOW")
    PT = ("PYTORCH", "PT", "TORCH")

    def __init__(self, model: Union["pl.LightningModule", "keras.models.Model"], mode: str = "TF"):
        self.MODE = mode.upper()
        self.model = model
        self.epochs_trained = 0

        if self.MODE in Learner.PT:
            self.trainer = None

    def fit(
        self,
        train_data,
        epochs,
        val_data=None,
        callbacks=None,
        **kwargs,
    ):
        """train models For TF:

        Just pass train data and start training For PyTorch:     You can
        enter configs to Lightning Trainer
        """
        MODE = self.MODE
        initial_epoch = self.epochs_trained
        self.epochs_trained += epochs

        if MODE in Learner.TF:
            return self.model.fit(
                train_data,
                epochs=epochs,
                initial_epoch=initial_epoch,
                validation_data=val_data,
                callbacks=callbacks,
            )
        if MODE in Learner.PT:
            lit_confs = kwargs.get("LIT_TRAINER_CONFIG", {})
            if not self.trainer:
                self.trainer = pl.Trainer(max_epochs=epochs, **lit_confs)
            return self.trainer.fit(self.model, train_data, val_data)
