# Ultralytics YOLO 🚀, GPL-3.0 license

import contextlib
from copy import deepcopy
from pathlib import Path

import thop
import torch
import torch.nn as nn

from ultralytics.nn.modules import *  # noqa: F403
from ultralytics.yolo.utils import DEFAULT_CFG_DICT, DEFAULT_CFG_KEYS, LOGGER, RANK, colorstr, emojis, yaml_load
from ultralytics.yolo.utils.checks import check_requirements, check_yaml
from ultralytics.yolo.utils.torch_utils import (fuse_conv_and_bn, fuse_deconv_and_bn, initialize_weights,
                                                intersect_dicts, make_divisible, model_info, scale_img, time_sync)


class BaseModel(nn.Module):
    """
    The BaseModel class serves as a base class for all the models in the Ultralytics YOLO family.
    """

    def forward(self, x, profile=False, visualize=False):
        """
        Forward pass of the model on a single scale.
        Wrapper for `_forward_once` method.

        Args:
            x (torch.Tensor): The input image tensor
            profile (bool): Whether to profile the model, defaults to False
            visualize (bool): Whether to return the intermediate feature maps, defaults to False

        Returns:
            (torch.Tensor): The output of the network.
        """
        return self._forward_once(x, profile, visualize)

    def _forward_once(self, x, profile=False, visualize=False):
        """
        Perform a forward pass through the network.

        Args:
            x (torch.Tensor): The input tensor to the model
            profile (bool):  Print the computation time of each layer if True, defaults to False.
            visualize (bool): Save the feature maps of the model if True, defaults to False

        Returns:
            (torch.Tensor): The last output of the model.
        """
        y, dt = [], []  # outputs
        for m in self.model:
            if m.f != -1:  # if not from previous layer
                x = y[m.f] if isinstance(m.f, int) else [x if j == -1 else y[j] for j in m.f]  # from earlier layers
            if profile:
                self._profile_one_layer(m, x, dt)
            x = m(x)  # run
            y.append(x if m.i in self.save else None)  # save output
            if visualize:
                LOGGER.info('visualize feature not yet supported')
                # TODO: feature_visualization(x, m.type, m.i, save_dir=visualize)
        return x

    def _profile_one_layer(self, m, x, dt):
        """
        Profile the computation time and FLOPs of a single layer of the model on a given input.
        Appends the results to the provided list.

        Args:
            m (nn.Module): The layer to be profiled.
            x (torch.Tensor): The input data to the layer.
            dt (list): A list to store the computation time of the layer.

        Returns:
            None
        """
        c = m == self.model[-1]  # is final layer, copy input as inplace fix
        o = thop.profile(m, inputs=[x.clone() if c else x], verbose=False)[0] / 1E9 * 2 if thop else 0  # FLOPs
        t = time_sync()
        for _ in range(10):
            m(x.clone() if c else x)
        dt.append((time_sync() - t) * 100)
        if m == self.model[0]:
            LOGGER.info(f"{'time (ms)':>10s} {'GFLOPs':>10s} {'params':>10s}  module")
        LOGGER.info(f'{dt[-1]:10.2f} {o:10.2f} {m.np:10.0f}  {m.type}')
        if c:
            LOGGER.info(f"{sum(dt):10.2f} {'-':>10s} {'-':>10s}  Total")

    def fuse(self, verbose=True):
        """
        Fuse the `Conv2d()` and `BatchNorm2d()` layers of the model into a single layer, in order to improve the
        computation efficiency.

        Returns:
            (nn.Module): The fused model is returned.
        """
        if not self.is_fused():
            for m in self.model.modules():
                if isinstance(m, (Conv, DWConv)) and hasattr(m, 'bn'):
                    m.conv = fuse_conv_and_bn(m.conv, m.bn)  # update conv
                    delattr(m, 'bn')  # remove batchnorm
                    m.forward = m.forward_fuse  # update forward
                if isinstance(m, ConvTranspose) and hasattr(m, 'bn'):
                    m.conv_transpose = fuse_deconv_and_bn(m.conv_transpose, m.bn)
                    delattr(m, 'bn')  # remove batchnorm
                    m.forward = m.forward_fuse  # update forward
            self.info(verbose=verbose)

        return self

    def is_fused(self, thresh=10):
        """
        Check if the model has less than a certain threshold of BatchNorm layers.

        Args:
            thresh (int, optional): The threshold number of BatchNorm layers. Default is 10.

        Returns:
            (bool): True if the number of BatchNorm layers in the model is less than the threshold, False otherwise.
        """
        bn = tuple(v for k, v in nn.__dict__.items() if 'Norm' in k)  # normalization layers, i.e. BatchNorm2d()
        return sum(isinstance(v, bn) for v in self.modules()) < thresh  # True if < 'thresh' BatchNorm layers in model

    def info(self, verbose=False, imgsz=640):
        """
        Prints model information

        Args:
            verbose (bool): if True, prints out the model information. Defaults to False
            imgsz (int): the size of the image that the model will be trained on. Defaults to 640
        """
        model_info(self, verbose=verbose, imgsz=imgsz)

    def _apply(self, fn):
        """
        `_apply()` is a function that applies a function to all the tensors in the model that are not
        parameters or registered buffers

        Args:
            fn: the function to apply to the model

        Returns:
            A model that is a Detect() object.
        """
        self = super()._apply(fn)
        m = self.model[-1]  # Detect()
        if isinstance(m, (Detect, Segment)):
            m.stride = fn(m.stride)
            m.anchors = fn(m.anchors)
            m.strides = fn(m.strides)
        return self

    def load(self, weights):
        """
        This function loads the weights of the model from a file

        Args:
            weights (str): The weights to load into the model.
        """
        # Force all tasks to implement this function
        raise NotImplementedError('This function needs to be implemented by derived classes!')


class DetectionModel(BaseModel):
    # YOLOv8 detection model
    def __init__(self, cfg='yolov8n.yaml', ch=3, nc=None, verbose=True):  # model, input channels, number of classes
        super().__init__()
        self.yaml = cfg if isinstance(cfg, dict) else yaml_load(check_yaml(cfg), append_filename=True)  # cfg dict

        # Define model
        ch = self.yaml['ch'] = self.yaml.get('ch', ch)  # input channels
        if nc and nc != self.yaml['nc']:
            LOGGER.info(f"Overriding model.yaml nc={self.yaml['nc']} with nc={nc}")
            self.yaml['nc'] = nc  # override yaml value
        self.model, self.save = parse_model(deepcopy(self.yaml), ch=ch, verbose=verbose)  # model, savelist
        self.names = {i: f'{i}' for i in range(self.yaml['nc'])}  # default names dict
        self.inplace = self.yaml.get('inplace', True)

        # Build strides
        m = self.model[-1]  # Detect()
        if isinstance(m, (Detect, Segment)):
            s = 256  # 2x min stride
            m.inplace = self.inplace
            forward = lambda x: self.forward(x)[0] if isinstance(m, Segment) else self.forward(x)
            m.stride = torch.tensor([s / x.shape[-2] for x in forward(torch.zeros(1, ch, s, s))])  # forward
            self.stride = m.stride
            m.bias_init()  # only run once

        # Init weights, biases
        initialize_weights(self)
        if verbose:
            self.info()
            LOGGER.info('')

    def forward(self, x, augment=False, profile=False, visualize=False):
        if augment:
            return self._forward_augment(x)  # augmented inference, None
        return self._forward_once(x, profile, visualize)  # single-scale inference, train

    def _forward_augment(self, x):
        img_size = x.shape[-2:]  # height, width
        s = [1, 0.83, 0.67]  # scales
        f = [None, 3, None]  # flips (2-ud, 3-lr)
        y = []  # outputs
        for si, fi in zip(s, f):
            xi = scale_img(x.flip(fi) if fi else x, si, gs=int(self.stride.max()))
            yi = self._forward_once(xi)[0]  # forward
            # cv2.imwrite(f'img_{si}.jpg', 255 * xi[0].cpu().numpy().transpose((1, 2, 0))[:, :, ::-1])  # save
            yi = self._descale_pred(yi, fi, si, img_size)
            y.append(yi)
        y = self._clip_augmented(y)  # clip augmented tails
        return torch.cat(y, -1), None  # augmented inference, train

    @staticmethod
    def _descale_pred(p, flips, scale, img_size, dim=1):
        # de-scale predictions following augmented inference (inverse operation)
        p[:, :4] /= scale  # de-scale
        x, y, wh, cls = p.split((1, 1, 2, p.shape[dim] - 4), dim)
        if flips == 2:
            y = img_size[0] - y  # de-flip ud
        elif flips == 3:
            x = img_size[1] - x  # de-flip lr
        return torch.cat((x, y, wh, cls), dim)

    def _clip_augmented(self, y):
        # Clip YOLOv5 augmented inference tails
        nl = self.model[-1].nl  # number of detection layers (P3-P5)
        g = sum(4 ** x for x in range(nl))  # grid points
        e = 1  # exclude layer count
        i = (y[0].shape[-1] // g) * sum(4 ** x for x in range(e))  # indices
        y[0] = y[0][..., :-i]  # large
        i = (y[-1].shape[-1] // g) * sum(4 ** (nl - 1 - x) for x in range(e))  # indices
        y[-1] = y[-1][..., i:]  # small
        return y

    def load(self, weights, verbose=True):
        csd = weights.float().state_dict()  # checkpoint state_dict as FP32
        csd = intersect_dicts(csd, self.state_dict())  # intersect
        self.load_state_dict(csd, strict=False)  # load
        if verbose and RANK == -1:
            LOGGER.info(f'Transferred {len(csd)}/{len(self.model.state_dict())} items from pretrained weights')


class SegmentationModel(DetectionModel):
    # YOLOv8 segmentation model
    def __init__(self, cfg='yolov8n-seg.yaml', ch=3, nc=None, verbose=True):
        super().__init__(cfg, ch, nc, verbose)

    def _forward_augment(self, x):
        raise NotImplementedError('WARNING ⚠️ SegmentationModel has not supported augment inference yet!')


class ClassificationModel(BaseModel):
    # YOLOv8 classification model
    def __init__(self,
                 cfg=None,
                 model=None,
                 ch=3,
                 nc=None,
                 cutoff=10,
                 verbose=True):  # yaml, model, channels, number of classes, cutoff index, verbose flag
        super().__init__()
        self._from_detection_model(model, nc, cutoff) if model is not None else self._from_yaml(cfg, ch, nc, verbose)

    def _from_detection_model(self, model, nc=1000, cutoff=10):
        # Create a YOLOv5 classification model from a YOLOv5 detection model
        from ultralytics.nn.autobackend import AutoBackend
        if isinstance(model, AutoBackend):
            model = model.model  # unwrap DetectMultiBackend
        model.model = model.model[:cutoff]  # backbone
        m = model.model[-1]  # last layer
        ch = m.conv.in_channels if hasattr(m, 'conv') else m.cv1.conv.in_channels  # ch into module
        c = Classify(ch, nc)  # Classify()
        c.i, c.f, c.type = m.i, m.f, 'models.common.Classify'  # index, from, type
        model.model[-1] = c  # replace
        self.model = model.model
        self.stride = model.stride
        self.save = []
        self.nc = nc

    def _from_yaml(self, cfg, ch, nc, verbose):
        self.yaml = cfg if isinstance(cfg, dict) else yaml_load(check_yaml(cfg), append_filename=True)  # cfg dict
        # Define model
        ch = self.yaml['ch'] = self.yaml.get('ch', ch)  # input channels
        if nc and nc != self.yaml['nc']:
            LOGGER.info(f"Overriding model.yaml nc={self.yaml['nc']} with nc={nc}")
            self.yaml['nc'] = nc  # override yaml value
        elif not nc and not self.yaml.get('nc', None):
            raise ValueError('nc not specified. Must specify nc in model.yaml or function arguments.')
        self.model, self.save = parse_model(deepcopy(self.yaml), ch=ch, verbose=verbose)  # model, savelist
        self.stride = torch.Tensor([1])  # no stride constraints
        self.names = {i: f'{i}' for i in range(self.yaml['nc'])}  # default names dict
        self.info()

    def load(self, weights):
        model = weights['model'] if isinstance(weights, dict) else weights  # torchvision models are not dicts
        csd = model.float().state_dict()
        csd = intersect_dicts(csd, self.state_dict())  # intersect
        self.load_state_dict(csd, strict=False)  # load

    @staticmethod
    def reshape_outputs(model, nc):
        # Update a TorchVision classification model to class count 'n' if required
        name, m = list((model.model if hasattr(model, 'model') else model).named_children())[-1]  # last module
        if isinstance(m, Classify):  # YOLO Classify() head
            if m.linear.out_features != nc:
                m.linear = nn.Linear(m.linear.in_features, nc)
        elif isinstance(m, nn.Linear):  # ResNet, EfficientNet
            if m.out_features != nc:
                setattr(model, name, nn.Linear(m.in_features, nc))
        elif isinstance(m, nn.Sequential):
            types = [type(x) for x in m]
            if nn.Linear in types:
                i = types.index(nn.Linear)  # nn.Linear index
                if m[i].out_features != nc:
                    m[i] = nn.Linear(m[i].in_features, nc)
            elif nn.Conv2d in types:
                i = types.index(nn.Conv2d)  # nn.Conv2d index
                if m[i].out_channels != nc:
                    m[i] = nn.Conv2d(m[i].in_channels, nc, m[i].kernel_size, m[i].stride, bias=m[i].bias is not None)


# Functions ------------------------------------------------------------------------------------------------------------


def torch_safe_load(weight):
    """
    This function attempts to load a PyTorch model with the torch.load() function. If a ModuleNotFoundError is raised, it
    catches the error, logs a warning message, and attempts to install the missing module via the check_requirements()
    function. After installation, the function again attempts to load the model using torch.load().

    Args:
        weight (str): The file path of the PyTorch model.

    Returns:
        The loaded PyTorch model.
    """
    from ultralytics.yolo.utils.downloads import attempt_download_asset

    file = attempt_download_asset(weight)  # search online if missing locally
    try:
        return torch.load(file, map_location='cpu'), file  # load
    except ModuleNotFoundError as e:  # e.name is missing module name
        if e.name == 'models':
            raise TypeError(
                emojis(f'ERROR ❌️ {weight} appears to be an Ultralytics YOLOv5 model originally trained '
                       f'with https://github.com/ultralytics/yolov5.\nThis model is NOT forwards compatible with '
                       f'YOLOv8 at https://github.com/ultralytics/ultralytics.'
                       f"\nRecommend fixes are to train a new model using the latest 'ultralytics' package or to "
                       f"run a command with an official YOLOv8 model, i.e. 'yolo predict model=yolov8n.pt'")) from e
        LOGGER.warning(f"WARNING ⚠️ {weight} appears to require '{e.name}', which is not in ultralytics requirements."
                       f"\nAutoInstall will run now for '{e.name}' but this feature will be removed in the future."
                       f"\nRecommend fixes are to train a new model using the latest 'ultralytics' package or to "
                       f"run a command with an official YOLOv8 model, i.e. 'yolo predict model=yolov8n.pt'")
        check_requirements(e.name)  # install missing module

        return torch.load(file, map_location='cpu'), file  # load


def attempt_load_weights(weights, device=None, inplace=True, fuse=False):
    # Loads an ensemble of models weights=[a,b,c] or a single model weights=[a] or weights=a

    ensemble = Ensemble()
    for w in weights if isinstance(weights, list) else [weights]:
        ckpt, w = torch_safe_load(w)  # load ckpt
        args = {**DEFAULT_CFG_DICT, **ckpt['train_args']}  # combine model and default args, preferring model args
        model = (ckpt.get('ema') or ckpt['model']).to(device).float()  # FP32 model

        # Model compatibility updates
        model.args = args  # attach args to model
        model.pt_path = w  # attach *.pt file path to model
        model.task = guess_model_task(model)
        if not hasattr(model, 'stride'):
            model.stride = torch.tensor([32.])

        # Append
        ensemble.append(model.fuse().eval() if fuse and hasattr(model, 'fuse') else model.eval())  # model in eval mode

    # Module compatibility updates
    for m in ensemble.modules():
        t = type(m)
        if t in (nn.Hardswish, nn.LeakyReLU, nn.ReLU, nn.ReLU6, nn.SiLU, Detect, Segment):
            m.inplace = inplace  # torch 1.7.0 compatibility
        elif t is nn.Upsample and not hasattr(m, 'recompute_scale_factor'):
            m.recompute_scale_factor = None  # torch 1.11.0 compatibility

    # Return model
    if len(ensemble) == 1:
        return ensemble[-1]

    # Return ensemble
    LOGGER.info(f'Ensemble created with {weights}\n')
    for k in 'names', 'nc', 'yaml':
        setattr(ensemble, k, getattr(ensemble[0], k))
    ensemble.stride = ensemble[torch.argmax(torch.tensor([m.stride.max() for m in ensemble])).int()].stride
    assert all(ensemble[0].nc == m.nc for m in ensemble), f'Models differ in class counts: {[m.nc for m in ensemble]}'
    return ensemble


def attempt_load_one_weight(weight, device=None, inplace=True, fuse=False):
    # Loads a single model weights
    ckpt, weight = torch_safe_load(weight)  # load ckpt
    args = {**DEFAULT_CFG_DICT, **ckpt['train_args']}  # combine model and default args, preferring model args
    model = (ckpt.get('ema') or ckpt['model']).to(device).float()  # FP32 model

    # Model compatibility updates
    model.args = {k: v for k, v in args.items() if k in DEFAULT_CFG_KEYS}  # attach args to model
    model.pt_path = weight  # attach *.pt file path to model
    model.task = guess_model_task(model)
    if not hasattr(model, 'stride'):
        model.stride = torch.tensor([32.])

    model = model.fuse().eval() if fuse and hasattr(model, 'fuse') else model.eval()  # model in eval mode

    # Module compatibility updates
    for m in model.modules():
        t = type(m)
        if t in (nn.Hardswish, nn.LeakyReLU, nn.ReLU, nn.ReLU6, nn.SiLU, Detect, Segment):
            m.inplace = inplace  # torch 1.7.0 compatibility
        elif t is nn.Upsample and not hasattr(m, 'recompute_scale_factor'):
            m.recompute_scale_factor = None  # torch 1.11.0 compatibility

    # Return model and ckpt
    return model, ckpt


def parse_model(d, ch, verbose=True):  # model_dict, input_channels(3)
    # Parse a YOLO model.yaml dictionary
    if verbose:
        LOGGER.info(f"\n{'':>3}{'from':>20}{'n':>3}{'params':>10}  {'module':<45}{'arguments':<30}")
    nc, gd, gw, act = d['nc'], d['depth_multiple'], d['width_multiple'], d.get('activation')
    if act:
        Conv.default_act = eval(act)  # redefine default activation, i.e. Conv.default_act = nn.SiLU()
        if verbose:
            LOGGER.info(f"{colorstr('activation:')} {act}")  # print
    ch = [ch]
    layers, save, c2 = [], [], ch[-1]  # layers, savelist, ch out
    for i, (f, n, m, args) in enumerate(d['backbone'] + d['head']):  # from, number, module, args
        m = getattr(torch.nn, m[3:]) if 'nn.' in m else globals()[m]  # get module
        for j, a in enumerate(args):
            # TODO: re-implement with eval() removal if possible
            # args[j] = (locals()[a] if a in locals() else ast.literal_eval(a)) if isinstance(a, str) else a
            with contextlib.suppress(NameError):
                args[j] = eval(a) if isinstance(a, str) else a  # eval strings

        n = n_ = max(round(n * gd), 1) if n > 1 else n  # depth gain
        if m in (Classify, Conv, ConvTranspose, GhostConv, Bottleneck, GhostBottleneck, SPP, SPPF, DWConv, Focus,
                 BottleneckCSP, C1, C2, C2f, C3, C3TR, C3Ghost, nn.ConvTranspose2d, DWConvTranspose2d, C3x):
            c1, c2 = ch[f], args[0]
            if c2 != nc:  # if c2 not equal to number of classes (i.e. for Classify() output)
                c2 = make_divisible(c2 * gw, 8)

            args = [c1, c2, *args[1:]]
            if m in (BottleneckCSP, C1, C2, C2f, C3, C3TR, C3Ghost, C3x):
                args.insert(2, n)  # number of repeats
                n = 1
        elif m is nn.BatchNorm2d:
            args = [ch[f]]
        elif m is Concat:
            c2 = sum(ch[x] for x in f)
        elif m in (Detect, Segment):
            args.append([ch[x] for x in f])
            if m is Segment:
                args[2] = make_divisible(args[2] * gw, 8)
        else:
            c2 = ch[f]

        m_ = nn.Sequential(*(m(*args) for _ in range(n))) if n > 1 else m(*args)  # module
        t = str(m)[8:-2].replace('__main__.', '')  # module type
        m.np = sum(x.numel() for x in m_.parameters())  # number params
        m_.i, m_.f, m_.type = i, f, t  # attach index, 'from' index, type
        if verbose:
            LOGGER.info(f'{i:>3}{str(f):>20}{n_:>3}{m.np:10.0f}  {t:<45}{str(args):<30}')  # print
        save.extend(x % i for x in ([f] if isinstance(f, int) else f) if x != -1)  # append to savelist
        layers.append(m_)
        if i == 0:
            ch = []
        ch.append(c2)
    return nn.Sequential(*layers), sorted(save)


def guess_model_task(model):
    """
    Guess the task of a PyTorch model from its architecture or configuration.

    Args:
        model (nn.Module) or (dict): PyTorch model or model configuration in YAML format.

    Returns:
        str: Task of the model ('detect', 'segment', 'classify').

    Raises:
        SyntaxError: If the task of the model could not be determined.
    """

    def cfg2task(cfg):
        # Guess from YAML dictionary
        m = cfg['head'][-1][-2].lower()  # output module name
        if m in ('classify', 'classifier', 'cls', 'fc'):
            return 'classify'
        if m == 'detect':
            return 'detect'
        if m == 'segment':
            return 'segment'

    # Guess from model cfg
    if isinstance(model, dict):
        with contextlib.suppress(Exception):
            return cfg2task(model)

    # Guess from PyTorch model
    if isinstance(model, nn.Module):  # PyTorch model
        for x in 'model.args', 'model.model.args', 'model.model.model.args':
            with contextlib.suppress(Exception):
                return eval(x)['task']
        for x in 'model.yaml', 'model.model.yaml', 'model.model.model.yaml':
            with contextlib.suppress(Exception):
                return cfg2task(eval(x))

        for m in model.modules():
            if isinstance(m, Detect):
                return 'detect'
            elif isinstance(m, Segment):
                return 'segment'
            elif isinstance(m, Classify):
                return 'classify'

    # Guess from model filename
    if isinstance(model, (str, Path)):
        model = Path(model)
        if '-seg' in model.stem or 'segment' in model.parts:
            return 'segment'
        elif '-cls' in model.stem or 'classify' in model.parts:
            return 'classify'
        elif 'detect' in model.parts:
            return 'detect'

    # Unable to determine task from model
    LOGGER.warning("WARNING ⚠️ Unable to automatically guess model task, assuming 'task=detect'. "
                   "Explicitly define task for your model, i.e. 'task=detect', 'task=segment' or 'task=classify'.")
    return 'detect'  # assume detect
