from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

from ppdet.core.workspace import register, create
from .meta_arch import BaseArch

__all__ = ['SSD']


@register
class SSD(BaseArch):
    __category__ = 'architecture'
    __inject__ = ['post_process']

    def __init__(self, backbone, ssd_head, post_process):
        super(SSD, self).__init__()
        self.backbone = backbone
        self.ssd_head = ssd_head
        self.post_process = post_process

    @classmethod
    def from_config(cls, cfg, *args, **kwargs):
        # backbone
        backbone = create(cfg['backbone'])

        # head
        kwargs = {'input_shape': backbone.out_shape}
        ssd_head = create(cfg['ssd_head'], **kwargs)

        return {
            'backbone': backbone,
            "ssd_head": ssd_head,
        }

    def _forward(self):
        # Backbone
        body_feats = self.backbone(self.inputs)

        # SSD Head
        if self.training:
            return self.ssd_head(body_feats, self.inputs['image'],
                                 self.inputs['gt_bbox'],
                                 self.inputs['gt_class'])
        else:
            boxes, scores, anchors = self.ssd_head(body_feats,
                                                   self.inputs['image'])
            bbox, bbox_num = self.post_process((boxes, scores), anchors,
                                               self.inputs['im_shape'],
                                               self.inputs['scale_factor'])
            return bbox, bbox_num

    def get_loss(self, ):
        return {"loss": self._forward()}

    def get_pred(self):
        bbox_pred, bbox_num = self._forward()
        label = bbox_pred[:, 0]
        score = bbox_pred[:, 1]
        bbox = bbox_pred[:, 2:]
        output = {
            'bbox': bbox,
            'score': score,
            'label': label,
            'bbox_num': bbox_num
        }
        return output