# Copyright (c) MONAI Consortium
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#     http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from __future__ import annotations

import os
import unittest
import warnings

import numpy as np
import torch
from torch.utils.data import DataLoader

import monai
from monai.apps import download_and_extract
from monai.data import decollate_batch
from monai.metrics import ROCAUCMetric
from monai.networks import eval_mode
from monai.networks.nets import DenseNet121
from monai.transforms import (
    Activations,
    AsDiscrete,
    Compose,
    EnsureChannelFirst,
    LoadImage,
    RandFlip,
    RandRotate,
    RandZoom,
    ScaleIntensity,
    Transpose,
)
from monai.utils import set_determinism
from tests.testing_data.integration_answers import test_integration_value
from tests.utils import DistTestCase, TimedCall, skip_if_downloading_fails, skip_if_quick, testing_data_config

TASK = "integration_classification_2d"


class MedNISTDataset(torch.utils.data.Dataset):
    def __init__(self, image_files, labels, transforms):
        self.image_files = image_files
        self.labels = labels
        self.transforms = transforms

    def __len__(self):
        return len(self.image_files)

    def __getitem__(self, index):
        return self.transforms(self.image_files[index]), self.labels[index]


def run_training_test(root_dir, train_x, train_y, val_x, val_y, device="cuda:0", num_workers=10):
    monai.config.print_config()
    # define transforms for image and classification
    train_transforms = Compose(
        [
            LoadImage(image_only=True, simple_keys=True),
            EnsureChannelFirst(channel_dim="no_channel"),
            Transpose(indices=[0, 2, 1]),
            ScaleIntensity(),
            RandRotate(range_x=np.pi / 12, prob=0.5, keep_size=True, dtype=np.float64),
            RandFlip(spatial_axis=0, prob=0.5),
            RandZoom(min_zoom=0.9, max_zoom=1.1, prob=0.5),
        ]
    )
    train_transforms.set_random_state(1234)
    val_transforms = Compose(
        [
            LoadImage(image_only=True, simple_keys=True),
            EnsureChannelFirst(channel_dim="no_channel"),
            Transpose(indices=[0, 2, 1]),
            ScaleIntensity(),
        ]
    )
    y_pred_trans = Compose([Activations(softmax=True)])
    y_trans = AsDiscrete(to_onehot=len(np.unique(train_y)))
    auc_metric = ROCAUCMetric()

    # create train, val data loaders
    train_ds = MedNISTDataset(train_x, train_y, train_transforms)
    train_loader = DataLoader(train_ds, batch_size=300, shuffle=True, num_workers=num_workers)

    val_ds = MedNISTDataset(val_x, val_y, val_transforms)
    val_loader = DataLoader(val_ds, batch_size=300, num_workers=num_workers)

    model = DenseNet121(spatial_dims=2, in_channels=1, out_channels=len(np.unique(train_y))).to(device)
    loss_function = torch.nn.CrossEntropyLoss()
    optimizer = torch.optim.Adam(model.parameters(), 1e-5)
    epoch_num = 4
    val_interval = 1

    # start training validation
    best_metric = -1
    best_metric_epoch = -1
    epoch_loss_values = []
    metric_values = []
    model_filename = os.path.join(root_dir, "best_metric_model.pth")
    for epoch in range(epoch_num):
        print("-" * 10)
        print(f"Epoch {epoch + 1}/{epoch_num}")
        model.train()
        epoch_loss = 0
        step = 0
        for batch_data in train_loader:
            step += 1
            inputs, labels = batch_data[0].to(device), batch_data[1].to(device)
            optimizer.zero_grad()
            outputs = model(inputs)
            loss = loss_function(outputs, labels)
            loss.backward()
            optimizer.step()
            epoch_loss += loss.item()
        epoch_loss /= step
        epoch_loss_values.append(epoch_loss)
        print(f"epoch {epoch + 1} average loss:{epoch_loss:0.4f}")

        if (epoch + 1) % val_interval == 0:
            with eval_mode(model):
                y_pred = torch.tensor([], dtype=torch.float32, device=device)
                y = torch.tensor([], dtype=torch.long, device=device)
                for val_data in val_loader:
                    val_images, val_labels = val_data[0].to(device), val_data[1].to(device)
                    y_pred = torch.cat([y_pred, model(val_images)], dim=0)
                    y = torch.cat([y, val_labels], dim=0)

                # compute accuracy
                acc_value = torch.eq(y_pred.argmax(dim=1), y)
                acc_metric = acc_value.sum().item() / len(acc_value)
                # decollate prediction and label and execute post processing
                y_pred = [y_pred_trans(i) for i in decollate_batch(y_pred)]
                y = [y_trans(i) for i in decollate_batch(y, detach=False)]
                # compute AUC
                auc_metric(y_pred, y)
                auc_value = auc_metric.aggregate()
                auc_metric.reset()
                metric_values.append(auc_value)
                if auc_value > best_metric:
                    best_metric = auc_value
                    best_metric_epoch = epoch + 1
                    torch.save(model.state_dict(), model_filename)
                    print("saved new best metric model")
                print(
                    f"current epoch {epoch +1} current AUC: {auc_value:0.4f} "
                    f"current accuracy: {acc_metric:0.4f} best AUC: {best_metric:0.4f} at epoch {best_metric_epoch}"
                )
    print(f"train completed, best_metric: {best_metric:0.4f}  at epoch: {best_metric_epoch}")
    return epoch_loss_values, best_metric, best_metric_epoch


def run_inference_test(root_dir, test_x, test_y, device="cuda:0", num_workers=10):
    # define transforms for image and classification
    val_transforms = Compose(
        [LoadImage(image_only=True), EnsureChannelFirst(channel_dim="no_channel"), ScaleIntensity()]
    )
    val_ds = MedNISTDataset(test_x, test_y, val_transforms)
    val_loader = DataLoader(val_ds, batch_size=300, num_workers=num_workers)

    model = DenseNet121(spatial_dims=2, in_channels=1, out_channels=len(np.unique(test_y))).to(device)

    model_filename = os.path.join(root_dir, "best_metric_model.pth")
    model.load_state_dict(torch.load(model_filename))
    y_true = []
    y_pred = []
    with eval_mode(model):
        for test_data in val_loader:
            test_images, test_labels = test_data[0].to(device), test_data[1].to(device)
            pred = model(test_images).argmax(dim=1)
            for i in range(len(pred)):
                y_true.append(test_labels[i].item())
                y_pred.append(pred[i].item())
    tps = [np.sum((np.asarray(y_true) == idx) & (np.asarray(y_pred) == idx)) for idx in np.unique(test_y)]
    return tps


@skip_if_quick
class IntegrationClassification2D(DistTestCase):
    def setUp(self):
        set_determinism(seed=0)
        self.data_dir = os.path.join(os.path.dirname(os.path.realpath(__file__)), "testing_data")
        data_dir = os.path.join(self.data_dir, "MedNIST")
        dataset_file = os.path.join(self.data_dir, "MedNIST.tar.gz")

        if not os.path.exists(data_dir):
            with skip_if_downloading_fails():
                data_spec = testing_data_config("images", "mednist")
                download_and_extract(
                    data_spec["url"],
                    dataset_file,
                    self.data_dir,
                    hash_val=data_spec["hash_val"],
                    hash_type=data_spec["hash_type"],
                )

        assert os.path.exists(data_dir)

        class_names = sorted(x for x in os.listdir(data_dir) if os.path.isdir(os.path.join(data_dir, x)))
        image_files = [
            [os.path.join(data_dir, class_name, x) for x in sorted(os.listdir(os.path.join(data_dir, class_name)))]
            for class_name in class_names
        ]
        image_file_list, image_classes = [], []
        for i, _ in enumerate(class_names):
            image_file_list.extend(image_files[i])
            image_classes.extend([i] * len(image_files[i]))

        # split train, val, test
        valid_frac, test_frac = 0.1, 0.1
        self.train_x, self.train_y = [], []
        self.val_x, self.val_y = [], []
        self.test_x, self.test_y = [], []
        for i in range(len(image_classes)):
            rann = np.random.random()
            if rann < valid_frac:
                self.val_x.append(image_file_list[i])
                self.val_y.append(image_classes[i])
            elif rann < test_frac + valid_frac:
                self.test_x.append(image_file_list[i])
                self.test_y.append(image_classes[i])
            else:
                self.train_x.append(image_file_list[i])
                self.train_y.append(image_classes[i])

        self.device = "cuda:0" if torch.cuda.is_available() else "cpu:0"

    def tearDown(self):
        set_determinism(seed=None)
        try:
            os.remove(os.path.join(self.data_dir, "best_metric_model.pth"))
        except FileNotFoundError:
            warnings.warn("not found best_metric_model.pth, training skipped?")
            pass

    def train_and_infer(self, idx=0):
        results = []
        if not os.path.exists(os.path.join(self.data_dir, "MedNIST")):
            # skip test if no MedNIST dataset
            return results

        set_determinism(seed=0)
        losses, best_metric, best_metric_epoch = run_training_test(
            self.data_dir, self.train_x, self.train_y, self.val_x, self.val_y, device=self.device
        )
        infer_metric = run_inference_test(self.data_dir, self.test_x, self.test_y, device=self.device)

        print(f"integration_classification_2d {losses}")
        print("best metric", best_metric)
        print("infer metric", infer_metric)
        # check training properties
        self.assertTrue(test_integration_value(TASK, key="losses", data=losses, rtol=1e-2))
        self.assertTrue(test_integration_value(TASK, key="best_metric", data=best_metric, rtol=1e-4))
        np.testing.assert_allclose(best_metric_epoch, 4)
        model_file = os.path.join(self.data_dir, "best_metric_model.pth")
        self.assertTrue(os.path.exists(model_file))
        # check inference properties
        self.assertTrue(test_integration_value(TASK, key="infer_prop", data=np.asarray(infer_metric), rtol=1))
        results.extend(losses)
        results.append(best_metric)
        results.extend(infer_metric)
        return results

    def test_training(self):
        repeated = []
        for i in range(2):
            results = self.train_and_infer(i)
            repeated.append(results)
        np.testing.assert_allclose(repeated[0], repeated[1])

    @TimedCall(seconds=2000, skip_timing=not torch.cuda.is_available(), force_quit=False, daemon=False)
    def test_timing(self):
        self.train_and_infer()


if __name__ == "__main__":
    unittest.main()
