# YOLOv5 🚀 by Ultralytics, AGPL-3.0 license

"""

AutoAnchor utils

"""

import random

import numpy as np

import torch

import yaml

from tqdm import tqdm

from utils import TryExcept

from utils.general import LOGGER, TQDM_BAR_FORMAT, colorstr

PREFIX = colorstr('AutoAnchor: ')

def check_anchor_order(m):

    # Check anchor order against stride order for YOLOv5 Detect() module m, and correct if necessary

    a = m.anchors.prod(-1).mean(-1).view(-1)  # mean anchor area per output layer

    da = a[-1] - a[0]  # delta a

    ds = m.stride[-1] - m.stride[0]  # delta s

    if da and (da.sign() != ds.sign()):  # same order

        LOGGER.info(f'{PREFIX}Reversing anchor order')

        m.anchors[:] = m.anchors.flip(0)

@TryExcept(f'{PREFIX}ERROR')

def check_anchors(dataset, model, thr=4.0, imgsz=640):

    # Check anchor fit to data, recompute if necessary

    m = model.module.model[-1] if hasattr(model, 'module') else model.model[-1]  # Detect()

    shapes = imgsz * dataset.shapes / dataset.shapes.max(1, keepdims=True)

    scale = np.random.uniform(0.9, 1.1, size=(shapes.shape[0], 1))  # augment scale

    wh = torch.tensor(np.concatenate([l[:, 3:5] * s for s, l in zip(shapes * scale, dataset.labels)])).float()  # wh

    def metric(k):  # compute metric

        r = wh[:, None] / k[None]

        x = torch.min(r, 1 / r).min(2)[0]  # ratio metric

        best = x.max(1)[0]  # best_x

        aat = (x > 1 / thr).float().sum(1).mean()  # anchors above threshold

        bpr = (best > 1 / thr).float().mean()  # best possible recall

        return bpr, aat

    stride = m.stride.to(m.anchors.device).view(-1, 1, 1)  # model strides

    anchors = m.anchors.clone() * stride  # current anchors

    bpr, aat = metric(anchors.cpu().view(-1, 2))

    s = f'\n{PREFIX}{aat:.2f} anchors/target, {bpr:.3f} Best Possible Recall (BPR). '

    if bpr > 0.98:  # threshold to recompute

        LOGGER.info(f'{s}Current anchors are a good fit to dataset ✅')

    else:

        LOGGER.info(f'{s}Anchors are a poor fit to dataset ⚠️, attempting to improve...')

        na = m.anchors.numel() // 2  # number of anchors

        anchors = kmean_anchors(dataset, n=na, img_size=imgsz, thr=thr, gen=1000, verbose=False)

        new_bpr = metric(anchors)[0]

        if new_bpr > bpr:  # replace anchors

            anchors = torch.tensor(anchors, device=m.anchors.device).type_as(m.anchors)

            m.anchors[:] = anchors.clone().view_as(m.anchors)

            check_anchor_order(m)  # must be in pixel-space (not grid-space)

            m.anchors /= stride

            s = f'{PREFIX}Done ✅ (optional: update model *.yaml to use these anchors in the future)'

        else:

            s = f'{PREFIX}Done ⚠️ (original anchors better than new anchors, proceeding with original anchors)'

        LOGGER.info(s)

def kmean_anchors(dataset='./data/coco128.yaml', n=9, img_size=640, thr=4.0, gen=1000, verbose=True):

    """ Creates kmeans-evolved anchors from training dataset

        Arguments:

            dataset: path to data.yaml, or a loaded dataset

            n: number of anchors

            img_size: image size used for training

            thr: anchor-label wh ratio threshold hyperparameter hyp['anchor_t'] used for training, default=4.0

            gen: generations to evolve anchors using genetic algorithm

            verbose: print all results

        Return:

            k: kmeans evolved anchors

        Usage:

            from utils.autoanchor import *; _ = kmean_anchors()

    """

    from scipy.cluster.vq import kmeans

    npr = np.random

    thr = 1 / thr

    def metric(k, wh):  # compute metrics

        r = wh[:, None] / k[None]

        x = torch.min(r, 1 / r).min(2)[0]  # ratio metric

        # x = wh_iou(wh, torch.tensor(k))  # iou metric

        return x, x.max(1)[0]  # x, best_x

    def anchor_fitness(k):  # mutation fitness

        _, best = metric(torch.tensor(k, dtype=torch.float32), wh)

        return (best * (best > thr).float()).mean()  # fitness

    def print_results(k, verbose=True):

        k = k[np.argsort(k.prod(1))]  # sort small to large

        x, best = metric(k, wh0)

        bpr, aat = (best > thr).float().mean(), (x > thr).float().mean() * n  # best possible recall, anch > thr

        s = f'{PREFIX}thr={thr:.2f}: {bpr:.4f} best possible recall, {aat:.2f} anchors past thr\n' \

            f'{PREFIX}n={n}, img_size={img_size}, metric_all={x.mean():.3f}/{best.mean():.3f}-mean/best, ' \

            f'past_thr={x[x > thr].mean():.3f}-mean: '

        for x in k:

            s += '%i,%i, ' % (round(x[0]), round(x[1]))

        if verbose:

            LOGGER.info(s[:-2])

        return k

    if isinstance(dataset, str):  # *.yaml file

        with open(dataset, errors='ignore') as f:

            data_dict = yaml.safe_load(f)  # model dict

        from utils.dataloaders import LoadImagesAndLabels

        dataset = LoadImagesAndLabels(data_dict['train'], augment=True, rect=True)

    # Get label wh

    shapes = img_size * dataset.shapes / dataset.shapes.max(1, keepdims=True)

    wh0 = np.concatenate([l[:, 3:5] * s for s, l in zip(shapes, dataset.labels)])  # wh

    # Filter

    i = (wh0 < 3.0).any(1).sum()

    if i:

        LOGGER.info(f'{PREFIX}WARNING ⚠️ Extremely small objects found: {i} of {len(wh0)} labels are <3 pixels in size')

    wh = wh0[(wh0 >= 2.0).any(1)].astype(np.float32)  # filter > 2 pixels

    # wh = wh * (npr.rand(wh.shape[0], 1) * 0.9 + 0.1)  # multiply by random scale 0-1

    # Kmeans init

    try:

        LOGGER.info(f'{PREFIX}Running kmeans for {n} anchors on {len(wh)} points...')

        assert n <= len(wh)  # apply overdetermined constraint

        s = wh.std(0)  # sigmas for whitening

        k = kmeans(wh / s, n, iter=30)[0] * s  # points

        assert n == len(k)  # kmeans may return fewer points than requested if wh is insufficient or too similar

    except Exception:

        LOGGER.warning(f'{PREFIX}WARNING ⚠️ switching strategies from kmeans to random init')

        k = np.sort(npr.rand(n * 2)).reshape(n, 2) * img_size  # random init

    wh, wh0 = (torch.tensor(x, dtype=torch.float32) for x in (wh, wh0))

    k = print_results(k, verbose=False)

    # Plot

    # k, d = [None] * 20, [None] * 20

    # for i in tqdm(range(1, 21)):

    #     k[i-1], d[i-1] = kmeans(wh / s, i)  # points, mean distance

    # fig, ax = plt.subplots(1, 2, figsize=(14, 7), tight_layout=True)

    # ax = ax.ravel()

    # ax[0].plot(np.arange(1, 21), np.array(d) ** 2, marker='.')

    # fig, ax = plt.subplots(1, 2, figsize=(14, 7))  # plot wh

    # ax[0].hist(wh[wh[:, 0]<100, 0],400)

    # ax[1].hist(wh[wh[:, 1]<100, 1],400)

    # fig.savefig('wh.png', dpi=200)

    # Evolve

    f, sh, mp, s = anchor_fitness(k), k.shape, 0.9, 0.1  # fitness, generations, mutation prob, sigma

    pbar = tqdm(range(gen), bar_format=TQDM_BAR_FORMAT)  # progress bar

    for _ in pbar:

        v = np.ones(sh)

        while (v == 1).all():  # mutate until a change occurs (prevent duplicates)

            v = ((npr.random(sh) < mp) * random.random() * npr.randn(*sh) * s + 1).clip(0.3, 3.0)

        kg = (k.copy() * v).clip(min=2.0)

        fg = anchor_fitness(kg)

        if fg > f:

            f, k = fg, kg.copy()

            pbar.desc = f'{PREFIX}Evolving anchors with Genetic Algorithm: fitness = {f:.4f}'

            if verbose:

                print_results(k, verbose)

    return print_results(k).astype(np.float32)