import warnings

import mmcv
import numpy as np
import torch
from mmcv.ops import RoIPool
from mmcv.parallel import collate, scatter
from mmcv.runner import load_checkpoint

from mmdet.core import get_classes
from mmdet.datasets import replace_ImageToTensor
from mmdet.datasets.pipelines import Compose
from mmdet.models import build_detector


def init_detector(config, checkpoint=None, device='cuda:0', cfg_options=None):
    """Initialize a detector from config file.

    Args:
        config (str or :obj:`mmcv.Config`): Config file path or the config
            object.
        checkpoint (str, optional): Checkpoint path. If left as None, the model
            will not load any weights.
        cfg_options (dict): Options to override some settings in the used
            config.

    Returns:
        nn.Module: The constructed detector.
    """
    if isinstance(config, str):
        config = mmcv.Config.fromfile(config)
    elif not isinstance(config, mmcv.Config):
        raise TypeError('config must be a filename or Config object, '
                        f'but got {type(config)}')
    if cfg_options is not None:
        config.merge_from_dict(cfg_options)
    config.model.pretrained = None
    config.model.train_cfg = None
    model = build_detector(config.model, test_cfg=config.get('test_cfg'))
    if checkpoint is not None:
        map_loc = 'cpu' if device == 'cpu' else None
        checkpoint = load_checkpoint(model, checkpoint, map_location=map_loc)
        if 'CLASSES' in checkpoint.get('meta', {}):
            model.CLASSES = checkpoint['meta']['CLASSES']
        else:
            warnings.simplefilter('once')
            warnings.warn('Class names are not saved in the checkpoint\'s '
                          'meta data, use COCO classes by default.')
            model.CLASSES = get_classes('coco')
    model.cfg = config  # save the config in the model for convenience
    model.to(device)
    model.eval()
    return model


class LoadImage(object):
    """A simple pipeline to load image."""

    def __call__(self, results):
        """Call function to load images into results.

        Args:
            results (dict): A result dict contains the file name
                of the image to be read.

        Returns:
            dict: ``results`` will be returned containing loaded image.
        """
        if isinstance(results['img'], str):
            results['filename'] = results['img']
            results['ori_filename'] = results['img']
        else:
            results['filename'] = None
            results['ori_filename'] = None
        img = mmcv.imread(results['img'])
        results['img'] = img
        results['img_fields'] = ['img']
        results['img_shape'] = img.shape
        results['ori_shape'] = img.shape
        return results


def inference_detector(model, imgs):
    """Inference image(s) with the detector.

    Args:
        model (nn.Module): The loaded detector.
        imgs (str/ndarray or list[str/ndarray] or tuple[str/ndarray]):
           Either image files or loaded images.

    Returns:
        If imgs is a list or tuple, the same length list type results
        will be returned, otherwise return the detection results directly.
    """

    if isinstance(imgs, (list, tuple)):
        is_batch = True
    else:
        imgs = [imgs]
        is_batch = False

    cfg = model.cfg
    device = next(model.parameters()).device  # model device

    if isinstance(imgs[0], np.ndarray):
        cfg = cfg.copy()
        # set loading pipeline type
        cfg.data.test.pipeline[0].type = 'LoadImageFromWebcam'

    cfg.data.test.pipeline = replace_ImageToTensor(cfg.data.test.pipeline)
    test_pipeline = Compose(cfg.data.test.pipeline)

    datas = []
    for img in imgs:
        # prepare data
        if isinstance(img, np.ndarray):
            # directly add img
            data = dict(img=img)
        else:
            # add information into dict
            data = dict(img_info=dict(filename=img), img_prefix=None)
        # build the data pipeline
        data = test_pipeline(data)
        datas.append(data)

    data = collate(datas, samples_per_gpu=len(imgs))
    # just get the actual data from DataContainer
    data['img_metas'] = [img_metas.data[0] for img_metas in data['img_metas']]
    data['img'] = [img.data[0] for img in data['img']]
    if next(model.parameters()).is_cuda:
        # scatter to specified GPU
        data = scatter(data, [device])[0]
    else:
        for m in model.modules():
            assert not isinstance(
                m, RoIPool
            ), 'CPU inference with RoIPool is not supported currently.'

    # forward the model
    with torch.no_grad():
        results = model(return_loss=False, rescale=True, **data)

    if not is_batch:
        return results[0]
    else:
        return results


async def async_inference_detector(model, img):
    """Async inference image(s) with the detector.

    Args:
        model (nn.Module): The loaded detector.
        img (str | ndarray): Either image files or loaded images.

    Returns:
        Awaitable detection results.
    """
    cfg = model.cfg
    device = next(model.parameters()).device  # model device
    # prepare data
    if isinstance(img, np.ndarray):
        # directly add img
        data = dict(img=img)
        cfg = cfg.copy()
        # set loading pipeline type
        cfg.data.test.pipeline[0].type = 'LoadImageFromWebcam'
    else:
        # add information into dict
        data = dict(img_info=dict(filename=img), img_prefix=None)
    # build the data pipeline
    test_pipeline = Compose(cfg.data.test.pipeline)
    data = test_pipeline(data)
    data = scatter(collate([data], samples_per_gpu=1), [device])[0]

    # We don't restore `torch.is_grad_enabled()` value during concurrent
    # inference since execution can overlap
    torch.set_grad_enabled(False)
    result = await model.aforward_test(rescale=True, **data)
    return result


def show_result_pyplot(model,
                       img,
                       result,
                       score_thr=0.3,
                       title='result',
                       wait_time=0):
    """Visualize the detection results on the image.

    Args:
        model (nn.Module): The loaded detector.
        img (str or np.ndarray): Image filename or loaded image.
        result (tuple[list] or list): The detection result, can be either
            (bbox, segm) or just bbox.
        score_thr (float): The threshold to visualize the bboxes and masks.
        title (str): Title of the pyplot figure.
        wait_time (float): Value of waitKey param.
                Default: 0.
    """
    if hasattr(model, 'module'):
        model = model.module
    model.show_result(
        img,
        result,
        score_thr=score_thr,
        show=True,
        wait_time=wait_time,
        win_name=title,
        bbox_color=(72, 101, 241),
        text_color=(72, 101, 241))
