# Copyright The PyTorch Lightning team.
#
# 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.
import os
from unittest import mock

import pytest
import torch

from pytorch_lightning import Trainer, callbacks, seed_everything
from tests.base import BoringModel


@mock.patch.dict(os.environ, {"PL_DEV_DEBUG": "1"})
def test_mc_called_on_fastdevrun(tmpdir):
    seed_everything(1234)

    train_val_step_model = BoringModel()

    # fast dev run = called once
    # train loop only, dict, eval result
    trainer = Trainer(fast_dev_run=True)
    trainer.fit(train_val_step_model)

    # checkpoint should have been called once with fast dev run
    assert len(trainer.dev_debugger.checkpoint_callback_history) == 1

    # -----------------------
    # also called once with no val step
    # -----------------------
    class TrainingStepCalled(BoringModel):
        def __init__(self):
            super().__init__()
            self.training_step_called = False
            self.validation_step_called = False
            self.test_step_called = False

        def training_step(self, batch, batch_idx):
            self.training_step_called = True
            return super().training_step(batch, batch_idx)

    train_step_only_model = TrainingStepCalled()
    train_step_only_model.validation_step = None

    # fast dev run = called once
    # train loop only, dict, eval result
    trainer = Trainer(fast_dev_run=True)
    trainer.fit(train_step_only_model)

    # make sure only training step was called
    assert train_step_only_model.training_step_called
    assert not train_step_only_model.validation_step_called
    assert not train_step_only_model.test_step_called

    # checkpoint should have been called once with fast dev run
    assert len(trainer.dev_debugger.checkpoint_callback_history) == 1


@mock.patch.dict(os.environ, {"PL_DEV_DEBUG": "1"})
def test_mc_called(tmpdir):
    seed_everything(1234)

    # -----------------
    # TRAIN LOOP ONLY
    # -----------------
    train_step_only_model = BoringModel()
    train_step_only_model.validation_step = None

    # no callback
    trainer = Trainer(max_epochs=3, checkpoint_callback=False)
    trainer.fit(train_step_only_model)
    assert len(trainer.dev_debugger.checkpoint_callback_history) == 0

    # -----------------
    # TRAIN + VAL LOOP ONLY
    # -----------------
    val_train_model = BoringModel()
    # no callback
    trainer = Trainer(max_epochs=3, checkpoint_callback=False)
    trainer.fit(val_train_model)
    assert len(trainer.dev_debugger.checkpoint_callback_history) == 0


@mock.patch('torch.save')
@pytest.mark.parametrize(['epochs', 'val_check_interval', 'expected'],
                         [(1, 1.0, 1), (2, 1.0, 2), (1, 0.25, 4), (2, 0.3, 7)])
def test_default_checkpoint_freq(save_mock, tmpdir, epochs, val_check_interval, expected):

    model = BoringModel()
    trainer = Trainer(
        default_root_dir=tmpdir,
        max_epochs=epochs,
        weights_summary=None,
        val_check_interval=val_check_interval
    )
    trainer.fit(model)

    # make sure types are correct
    assert save_mock.call_count == expected


@mock.patch('torch.save')
@pytest.mark.parametrize(['k', 'epochs', 'val_check_interval', 'expected'],
                         [(1, 1, 1.0, 1), (2, 2, 1.0, 2), (2, 1, 0.25, 4), (2, 2, 0.3, 7)])
def test_top_k(save_mock, tmpdir, k, epochs, val_check_interval, expected):

    class TestModel(BoringModel):
        def __init__(self):
            super().__init__()
            self.last_coeff = 10.0

        def training_step(self, batch, batch_idx):
            loss = self.step(torch.ones(32))
            loss = loss / (loss + 0.0000001)
            loss += self.last_coeff
            self.log('my_loss', loss)
            self.last_coeff *= 0.999
            return loss

    model = TestModel()
    trainer = Trainer(
        callbacks=[callbacks.ModelCheckpoint(dirpath=tmpdir, monitor='my_loss', save_top_k=k)],
        default_root_dir=tmpdir,
        max_epochs=epochs,
        weights_summary=None,
        val_check_interval=val_check_interval
    )
    trainer.fit(model)

    # make sure types are correct
    assert save_mock.call_count == expected