# 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 copy import deepcopy

import pytest
import torch

from pytorch_lightning import seed_everything, Trainer
from pytorch_lightning.utilities.exceptions import MisconfigurationException
from tests.base import EvalModelTemplate
from tests.helpers import BoringModel
from tests.helpers.datamodules import ClassifDataModule
from tests.helpers.simple_models import ClassificationModel


def test_error_on_more_than_1_optimizer(tmpdir):
    """Check that error is thrown when more than 1 optimizer is passed"""

    model = EvalModelTemplate()
    model.configure_optimizers = model.configure_optimizers__multiple_schedulers

    # logger file to get meta
    trainer = Trainer(default_root_dir=tmpdir, max_epochs=1)

    with pytest.raises(MisconfigurationException):
        trainer.tuner.lr_find(model)


def test_model_reset_correctly(tmpdir):
    """Check that model weights are correctly reset after lr_find()"""

    model = EvalModelTemplate()

    # logger file to get meta
    trainer = Trainer(default_root_dir=tmpdir, max_epochs=1)

    before_state_dict = deepcopy(model.state_dict())

    trainer.tuner.lr_find(model, num_training=5)

    after_state_dict = model.state_dict()

    for key in before_state_dict.keys():
        assert torch.all(
            torch.eq(before_state_dict[key], after_state_dict[key])
        ), "Model was not reset correctly after learning rate finder"

    assert not os.path.exists(tmpdir / "lr_find_temp_model.ckpt")


def test_trainer_reset_correctly(tmpdir):
    """Check that all trainer parameters are reset correctly after lr_find()"""

    model = EvalModelTemplate()

    # logger file to get meta
    trainer = Trainer(default_root_dir=tmpdir, max_epochs=1)

    changed_attributes = [
        "accumulate_grad_batches",
        "auto_lr_find",
        "callbacks",
        "checkpoint_callback",
        "current_epoch",
        "logger",
        "max_steps",
    ]
    expected = {ca: getattr(trainer, ca) for ca in changed_attributes}
    trainer.tuner.lr_find(model, num_training=5)
    actual = {ca: getattr(trainer, ca) for ca in changed_attributes}

    assert actual == expected
    assert model.trainer == trainer


@pytest.mark.parametrize("use_hparams", [False, True])
def test_trainer_arg_bool(tmpdir, use_hparams):
    """Test that setting trainer arg to bool works"""
    hparams = EvalModelTemplate.get_default_hparams()
    model = EvalModelTemplate(**hparams)
    before_lr = hparams.get("learning_rate")
    if use_hparams:
        del model.learning_rate
        model.configure_optimizers = model.configure_optimizers__lr_from_hparams

    # logger file to get meta
    trainer = Trainer(default_root_dir=tmpdir, max_epochs=2, auto_lr_find=True)

    trainer.tune(model)
    if use_hparams:
        after_lr = model.hparams.learning_rate
    else:
        after_lr = model.learning_rate

    assert before_lr != after_lr, "Learning rate was not altered after running learning rate finder"


@pytest.mark.parametrize("use_hparams", [False, True])
def test_trainer_arg_str(tmpdir, use_hparams):
    """Test that setting trainer arg to string works"""
    hparams = EvalModelTemplate.get_default_hparams()
    model = EvalModelTemplate(**hparams)
    model.my_fancy_lr = 1.0  # update with non-standard field
    model.hparams["my_fancy_lr"] = 1.0
    before_lr = model.my_fancy_lr
    if use_hparams:
        del model.my_fancy_lr
        model.configure_optimizers = model.configure_optimizers__lr_from_hparams

    # logger file to get meta
    trainer = Trainer(default_root_dir=tmpdir, max_epochs=2, auto_lr_find="my_fancy_lr")

    trainer.tune(model)
    if use_hparams:
        after_lr = model.hparams.my_fancy_lr
    else:
        after_lr = model.my_fancy_lr

    assert before_lr != after_lr, "Learning rate was not altered after running learning rate finder"


@pytest.mark.parametrize("optimizer", ["Adam", "Adagrad"])
def test_call_to_trainer_method(tmpdir, optimizer):
    """Test that directly calling the trainer method works"""

    hparams = EvalModelTemplate.get_default_hparams()
    model = EvalModelTemplate(**hparams)
    if optimizer == "adagrad":
        model.configure_optimizers = model.configure_optimizers__adagrad

    before_lr = hparams.get("learning_rate")
    # logger file to get meta
    trainer = Trainer(default_root_dir=tmpdir, max_epochs=2)

    lrfinder = trainer.tuner.lr_find(model, mode="linear")
    after_lr = lrfinder.suggestion()
    model.learning_rate = after_lr
    trainer.tune(model)

    assert before_lr != after_lr, "Learning rate was not altered after running learning rate finder"


def test_datamodule_parameter(tmpdir):
    """Test that the datamodule parameter works"""
    seed_everything(1)

    dm = ClassifDataModule()
    model = ClassificationModel()

    before_lr = model.lr
    # logger file to get meta
    trainer = Trainer(default_root_dir=tmpdir, max_epochs=2)

    lrfinder = trainer.tuner.lr_find(model, datamodule=dm)
    after_lr = lrfinder.suggestion()
    model.lr = after_lr

    assert before_lr != after_lr, "Learning rate was not altered after running learning rate finder"


def test_accumulation_and_early_stopping(tmpdir):
    """Test that early stopping of learning rate finder works, and that accumulation also works for this feature"""

    class TestModel(BoringModel):
        def __init__(self):
            super().__init__()
            self.lr = 1e-3

    model = TestModel()
    trainer = Trainer(default_root_dir=tmpdir, accumulate_grad_batches=2)
    lrfinder = trainer.tuner.lr_find(model, early_stop_threshold=None)

    assert lrfinder.suggestion() != 1e-3
    assert len(lrfinder.results["lr"]) == 100
    assert lrfinder._total_batch_idx == 199


def test_suggestion_parameters_work(tmpdir):
    """Test that default skipping does not alter results in basic case"""

    dm = ClassifDataModule()
    model = ClassificationModel()

    # logger file to get meta
    trainer = Trainer(default_root_dir=tmpdir, max_epochs=3)

    lrfinder = trainer.tuner.lr_find(model, datamodule=dm)
    lr1 = lrfinder.suggestion(skip_begin=10)  # default
    lr2 = lrfinder.suggestion(skip_begin=150)  # way too high, should have an impact

    assert lr1 != lr2, "Skipping parameter did not influence learning rate"


def test_suggestion_with_non_finite_values(tmpdir):
    """Test that non-finite values does not alter results"""

    hparams = EvalModelTemplate.get_default_hparams()
    model = EvalModelTemplate(**hparams)

    # logger file to get meta
    trainer = Trainer(default_root_dir=tmpdir, max_epochs=3)

    lrfinder = trainer.tuner.lr_find(model)
    before_lr = lrfinder.suggestion()
    lrfinder.results["loss"][-1] = float("nan")
    after_lr = lrfinder.suggestion()

    assert before_lr == after_lr, "Learning rate was altered because of non-finite loss values"


def test_lr_finder_fails_fast_on_bad_config(tmpdir):
    """Test that tune fails if the model does not have a lr BEFORE running lr find"""
    trainer = Trainer(default_root_dir=tmpdir, max_steps=2, auto_lr_find=True)
    with pytest.raises(MisconfigurationException, match="should have one of these fields"):
        trainer.tune(BoringModel())


def test_lr_find_with_bs_scale(tmpdir):
    """Test that lr_find runs with batch_size_scaling"""

    class BoringModelTune(BoringModel):
        def __init__(self, learning_rate=0.1, batch_size=2):
            super().__init__()
            self.save_hyperparameters()

    model = BoringModelTune()
    before_lr = model.hparams.learning_rate

    # logger file to get meta
    trainer = Trainer(default_root_dir=tmpdir, max_epochs=3, auto_lr_find=True, auto_scale_batch_size=True)
    result = trainer.tune(model)
    bs = result["scale_batch_size"]
    lr = result["lr_find"].suggestion()

    assert lr != before_lr
    assert isinstance(bs, int)


def test_lr_candidates_between_min_and_max(tmpdir):
    """Test that learning rate candidates are between min_lr and max_lr."""

    class TestModel(BoringModel):
        def __init__(self, learning_rate=0.1):
            super().__init__()
            self.save_hyperparameters()

    model = TestModel()
    trainer = Trainer(default_root_dir=tmpdir)

    lr_min = 1e-8
    lr_max = 1.0
    lr_finder = trainer.tuner.lr_find(model, max_lr=lr_min, min_lr=lr_max, num_training=3)
    lr_candidates = lr_finder.results["lr"]
    assert all(lr_min <= lr <= lr_max for lr in lr_candidates)


def test_lr_finder_ends_before_num_training(tmpdir):
    """Tests learning rate finder ends before `num_training` steps."""

    class TestModel(BoringModel):
        def __init__(self, learning_rate=0.1):
            super().__init__()
            self.save_hyperparameters()

        def training_step_end(self, outputs):
            assert self.global_step < num_training
            return outputs

    model = TestModel()
    trainer = Trainer(default_root_dir=tmpdir)
    num_training = 3
    trainer.tuner.lr_find(model=model, num_training=num_training)