import base64
from dataclasses import dataclass
from io import BytesIO
from os import path
from typing import Dict, Optional

import numpy as np
import torch
import torchvision
import torchvision.transforms as T
from PIL import Image as PILImage

from lightning.pytorch import cli_lightning_logo, LightningDataModule, LightningModule
from lightning.pytorch.cli import LightningCLI
from lightning.pytorch.serve import ServableModule, ServableModuleValidator
from lightning.pytorch.utilities.model_helpers import get_torchvision_model

DATASETS_PATH = path.join(path.dirname(__file__), "..", "..", "Datasets")


class LitModule(LightningModule):
    def __init__(self, name: str = "resnet18"):
        super().__init__()
        self.model = get_torchvision_model(name, weights="DEFAULT")
        self.model.fc = torch.nn.Linear(self.model.fc.in_features, 10)
        self.criterion = torch.nn.CrossEntropyLoss()

    def training_step(self, batch, batch_idx):
        inputs, labels = batch
        outputs = self.model(inputs)
        loss = self.criterion(outputs, labels)
        self.log("train_loss", loss)
        return loss

    def validation_step(self, batch, batch_idx):
        inputs, labels = batch
        outputs = self.model(inputs)
        loss = self.criterion(outputs, labels)
        self.log("val_loss", loss)

    def configure_optimizers(self):
        return torch.optim.SGD(self.parameters(), lr=0.001, momentum=0.9)


class CIFAR10DataModule(LightningDataModule):
    transform = T.Compose([T.Resize(256), T.CenterCrop(224), T.ToTensor()])

    def train_dataloader(self, *args, **kwargs):
        trainset = torchvision.datasets.CIFAR10(root=DATASETS_PATH, train=True, download=True, transform=self.transform)
        return torch.utils.data.DataLoader(trainset, batch_size=2, shuffle=True, num_workers=0)

    def val_dataloader(self, *args, **kwargs):
        valset = torchvision.datasets.CIFAR10(root=DATASETS_PATH, train=False, download=True, transform=self.transform)
        return torch.utils.data.DataLoader(valset, batch_size=2, shuffle=True, num_workers=0)


@dataclass(unsafe_hash=True)
class Image:
    height: Optional[int] = None
    width: Optional[int] = None
    extension: str = "JPEG"
    mode: str = "RGB"
    channel_first: bool = False

    def deserialize(self, data: str) -> torch.Tensor:
        encoded_with_padding = (data + "===").encode("UTF-8")
        img = base64.b64decode(encoded_with_padding)
        buffer = BytesIO(img)
        img = PILImage.open(buffer, mode="r")
        if self.height and self.width:
            img = img.resize((self.width, self.height))
        arr = np.array(img)
        return T.ToTensor()(arr).unsqueeze(0)


class Top1:
    def serialize(self, tensor: torch.Tensor) -> int:
        return torch.nn.functional.softmax(tensor).argmax().item()


class ProductionReadyModel(LitModule, ServableModule):
    def configure_payload(self):
        # 1: Access the train dataloader and load a single sample.
        image, _ = self.trainer.train_dataloader.dataset[0]

        # 2: Convert the image into a PIL Image to bytes and encode it with base64
        pil_image = T.ToPILImage()(image)
        buffered = BytesIO()
        pil_image.save(buffered, format="JPEG")
        img_str = base64.b64encode(buffered.getvalue()).decode("UTF-8")

        return {"body": {"x": img_str}}

    def configure_serialization(self):
        return {"x": Image(224, 224).deserialize}, {"output": Top1().serialize}

    def serve_step(self, x: torch.Tensor) -> Dict[str, torch.Tensor]:
        return {"output": self.model(x)}

    def configure_response(self):
        return {"output": 7}


def cli_main():
    cli = LightningCLI(
        ProductionReadyModel,
        CIFAR10DataModule,
        seed_everything_default=42,
        save_config_kwargs={"overwrite": True},
        run=False,
        trainer_defaults={
            "accelerator": "cpu",
            "callbacks": [ServableModuleValidator()],
            "max_epochs": 1,
            "limit_train_batches": 5,
            "limit_val_batches": 5,
        },
    )
    cli.trainer.fit(cli.model, cli.datamodule)


if __name__ == "__main__":
    cli_lightning_logo()
    cli_main()
