# Copyright (c) OpenMMLab. All rights reserved.
import mmcv
import torch

from mmdet.models.dense_heads import TOODHead


def test_tood_head_loss():
    """Tests paa head loss when truth is empty and non-empty."""

    s = 256
    img_metas = [{
        'img_shape': (s, s, 3),
        'scale_factor': 1,
        'pad_shape': (s, s, 3)
    }]
    train_cfg = mmcv.Config(
        dict(
            initial_epoch=4,
            initial_assigner=dict(type='ATSSAssigner', topk=9),
            assigner=dict(type='TaskAlignedAssigner', topk=13),
            alpha=1,
            beta=6,
            allowed_border=-1,
            pos_weight=-1,
            debug=False))
    test_cfg = mmcv.Config(
        dict(
            nms_pre=1000,
            min_bbox_size=0,
            score_thr=0.05,
            nms=dict(type='nms', iou_threshold=0.6),
            max_per_img=100))
    # since Focal Loss is not supported on CPU
    self = TOODHead(
        num_classes=80,
        in_channels=1,
        stacked_convs=6,
        feat_channels=256,
        anchor_type='anchor_free',
        anchor_generator=dict(
            type='AnchorGenerator',
            ratios=[1.0],
            octave_base_scale=8,
            scales_per_octave=1,
            strides=[8, 16, 32, 64, 128]),
        bbox_coder=dict(
            type='DeltaXYWHBBoxCoder',
            target_means=[.0, .0, .0, .0],
            target_stds=[0.1, 0.1, 0.2, 0.2]),
        initial_loss_cls=dict(
            type='FocalLoss',
            use_sigmoid=True,
            activated=True,  # use probability instead of logit as input
            gamma=2.0,
            alpha=0.25,
            loss_weight=1.0),
        loss_cls=dict(
            type='QualityFocalLoss',
            use_sigmoid=True,
            activated=True,  # use probability instead of logit as input
            beta=2.0,
            loss_weight=1.0),
        loss_bbox=dict(type='GIoULoss', loss_weight=2.0),
        train_cfg=train_cfg,
        test_cfg=test_cfg)
    self.init_weights()
    feat = [
        torch.rand(1, 1, s // feat_size, s // feat_size)
        for feat_size in [8, 16, 32, 64, 128]
    ]
    cls_scores, bbox_preds = self(feat)

    # test initial assigner and losses
    self.epoch = 0
    # Test that empty ground truth encourages the network to predict background
    gt_bboxes = [torch.empty((0, 4))]
    gt_labels = [torch.LongTensor([])]
    gt_bboxes_ignore = None
    empty_gt_losses = self.loss(cls_scores, bbox_preds, gt_bboxes, gt_labels,
                                img_metas, gt_bboxes_ignore)
    # When there is no truth, the cls loss should be nonzero but there should
    # be no box loss.
    empty_cls_loss = empty_gt_losses['loss_cls']
    empty_box_loss = empty_gt_losses['loss_bbox']
    assert sum(empty_cls_loss).item() > 0, 'cls loss should be non-zero'
    assert sum(empty_box_loss).item() == 0, (
        'there should be no box loss when there are no true boxes')
    # When truth is non-empty then both cls and box loss should be nonzero for
    # random inputs
    gt_bboxes = [
        torch.Tensor([[23.6667, 23.8757, 238.6326, 151.8874]]),
    ]
    gt_labels = [torch.LongTensor([2])]
    one_gt_losses = self.loss(cls_scores, bbox_preds, gt_bboxes, gt_labels,
                              img_metas, gt_bboxes_ignore)
    onegt_cls_loss = one_gt_losses['loss_cls']
    onegt_box_loss = one_gt_losses['loss_bbox']
    assert sum(onegt_cls_loss).item() > 0, 'cls loss should be non-zero'
    assert sum(onegt_box_loss).item() > 0, 'box loss should be non-zero'

    # test task alignment assigner and losses
    self.epoch = 10
    # Test that empty ground truth encourages the network to predict background
    gt_bboxes = [torch.empty((0, 4))]
    gt_labels = [torch.LongTensor([])]
    gt_bboxes_ignore = None
    empty_gt_losses = self.loss(cls_scores, bbox_preds, gt_bboxes, gt_labels,
                                img_metas, gt_bboxes_ignore)
    # When there is no truth, the cls loss should be nonzero but there should
    # be no box loss.
    empty_cls_loss = empty_gt_losses['loss_cls']
    empty_box_loss = empty_gt_losses['loss_bbox']
    assert sum(empty_cls_loss).item() > 0, 'cls loss should be non-zero'
    assert sum(empty_box_loss).item() == 0, (
        'there should be no box loss when there are no true boxes')
    # When truth is non-empty then both cls and box loss should be nonzero for
    # random inputs
    gt_bboxes = [
        torch.Tensor([[23.6667, 23.8757, 238.6326, 151.8874]]),
    ]
    gt_labels = [torch.LongTensor([2])]
    one_gt_losses = self.loss(cls_scores, bbox_preds, gt_bboxes, gt_labels,
                              img_metas, gt_bboxes_ignore)
    onegt_cls_loss = one_gt_losses['loss_cls']
    onegt_box_loss = one_gt_losses['loss_bbox']
    assert sum(onegt_cls_loss).item() > 0, 'cls loss should be non-zero'
    assert sum(onegt_box_loss).item() > 0, 'box loss should be non-zero'