# Copyright (c) OpenMMLab. All rights reserved.
import tempfile
from unittest import TestCase

import torch
import torch.nn as nn
from mmengine import Runner
from mmengine.data import LabelData
from mmengine.model import BaseModel as EngineBaseModel
from mmengine.model import BaseModule
from torch.utils.data import Dataset

from mmselfsup.engine import SimSiamHook
from mmselfsup.models.algorithms import BaseModel
from mmselfsup.registry import MODELS
from mmselfsup.structures import SelfSupDataSample


class DummyDataset(Dataset):
    METAINFO = dict()  # type: ignore
    data = torch.randn(12, 2)
    label = torch.ones(12)

    @property
    def metainfo(self):
        return self.METAINFO

    def __len__(self):
        return self.data.size(0)

    def __getitem__(self, index):
        data_sample = SelfSupDataSample()
        gt_label = LabelData(value=self.label[index])
        setattr(data_sample, 'gt_label', gt_label)
        return dict(inputs=self.data[index], data_sample=data_sample)


@MODELS.register_module()
class SimSiamDummyLayer(BaseModule):

    def __init__(self, init_cfg=None):
        super().__init__(init_cfg)
        self.predictor = nn.Linear(2, 1)

    def forward(self, x):
        return self.predictor(x)


class ToyModel(BaseModel):

    def __init__(self):
        super().__init__(backbone=dict(type='SimSiamDummyLayer'))

    def loss(self, batch_inputs, data_samples):
        labels = []
        for x in data_samples:
            labels.append(x.gt_label.value)
            labels = torch.stack(labels)
        outputs = self.backbone(batch_inputs)
        loss = (labels - outputs).sum()
        outputs = dict(loss=loss)
        return outputs


class TestSimSiamHook(TestCase):

    def setUp(self):
        self.temp_dir = tempfile.TemporaryDirectory()

    def tearDown(self):
        self.temp_dir.cleanup()

    def test_simsiam_hook(self):
        device = 'cuda:0' if torch.cuda.is_available() else 'cpu'
        dummy_dataset = DummyDataset()
        toy_model = ToyModel().to(device)
        simsiam_hook = SimSiamHook(
            fix_pred_lr=True, lr=0.05, adjust_by_epoch=False)

        class DummyWrapper(EngineBaseModel):

            def __init__(self, model):
                super().__init__()
                self.module = model

            def forward(self, *args, **kwargs):
                return self.module(*args, **kwargs)

        # test SimSiamHook
        runner = Runner(
            model=DummyWrapper(toy_model),
            work_dir=self.temp_dir.name,
            train_dataloader=dict(
                dataset=dummy_dataset,
                sampler=dict(type='DefaultSampler', shuffle=True),
                batch_size=1,
                num_workers=0),
            optim_wrapper=dict(
                optimizer=dict(type='SGD', lr=0.05),
                paramwise_cfg=dict(
                    custom_keys={'predictor': dict(fix_lr=True)})),
            param_scheduler=dict(type='MultiStepLR', milestones=[1]),
            train_cfg=dict(by_epoch=True, max_epochs=2),
            custom_hooks=[simsiam_hook],
            default_hooks=dict(logger=None),
            log_processor=dict(window_size=1),
            experiment_name='test_simsiam_hook',
            default_scope='mmselfsup')

        runner.train()

        for param_group in runner.optim_wrapper.optimizer.param_groups:
            if 'fix_lr' in param_group and param_group['fix_lr']:
                assert param_group['lr'] == 0.05
            else:
                assert param_group['lr'] != 0.05