# Copyright (c) OpenMMLab. All rights reserved.
import argparse
import os.path as osp
import time

import mmcv
import numpy as np
import torch
from mmcv import Config
from mmcv.runner import load_checkpoint, wrap_fp16_model
from mmengine.runner import Runner
from mmengine.utils import revert_sync_batchnorm

from mmseg.registry import MODELS
from mmseg.utils import register_all_modules


def parse_args():
    parser = argparse.ArgumentParser(description='MMSeg benchmark a model')
    parser.add_argument('config', help='test config file path')
    parser.add_argument('checkpoint', help='checkpoint file')
    parser.add_argument(
        '--log-interval', type=int, default=50, help='interval of logging')
    parser.add_argument(
        '--work-dir',
        help=('if specified, the results will be dumped '
              'into the directory as json'))
    parser.add_argument('--repeat-times', type=int, default=1)
    args = parser.parse_args()
    return args


def main():
    args = parse_args()
    register_all_modules()
    cfg = Config.fromfile(args.config)
    timestamp = time.strftime('%Y%m%d_%H%M%S', time.localtime())
    if args.work_dir is not None:
        mmcv.mkdir_or_exist(osp.abspath(args.work_dir))
        json_file = osp.join(args.work_dir, f'fps_{timestamp}.json')
    else:
        # use config filename as default work_dir if cfg.work_dir is None
        work_dir = osp.join('./work_dirs',
                            osp.splitext(osp.basename(args.config))[0])
        mmcv.mkdir_or_exist(osp.abspath(work_dir))
        json_file = osp.join(work_dir, f'fps_{timestamp}.json')

    repeat_times = args.repeat_times
    # set cudnn_benchmark
    torch.backends.cudnn.benchmark = False
    cfg.model.pretrained = None

    benchmark_dict = dict(config=args.config, unit='img / s')
    overall_fps_list = []
    for time_index in range(repeat_times):
        print(f'Run {time_index + 1}:')
        # build the dataloader
        data_loader = Runner.build_dataloader(cfg.test_dataloader)

        # build the model and load checkpoint
        cfg.model.train_cfg = None
        model = MODELS.build(cfg.model)
        fp16_cfg = cfg.get('fp16', None)
        if fp16_cfg is not None:
            wrap_fp16_model(model)
        if 'checkpoint' in args and osp.exists(args.checkpoint):
            load_checkpoint(model, args.checkpoint, map_location='cpu')

        if torch.cuda.is_available():
            model = model.cuda()
        else:
            model = revert_sync_batchnorm(model)

        model.eval()

        # the first several iterations may be very slow so skip them
        num_warmup = 5
        pure_inf_time = 0
        total_iters = 200

        # benchmark with 200 batches and take the average
        for i, data in enumerate(data_loader):
            batch_inputs, data_samples = model.data_preprocessor(data, True)

            if torch.cuda.is_available():
                torch.cuda.synchronize()
            start_time = time.perf_counter()

            with torch.no_grad():
                model(batch_inputs, data_samples, mode='predict')

            if torch.cuda.is_available():
                torch.cuda.synchronize()
            elapsed = time.perf_counter() - start_time

            if i >= num_warmup:
                pure_inf_time += elapsed
                if (i + 1) % args.log_interval == 0:
                    fps = (i + 1 - num_warmup) / pure_inf_time
                    print(f'Done image [{i + 1:<3}/ {total_iters}], '
                          f'fps: {fps:.2f} img / s')

            if (i + 1) == total_iters:
                fps = (i + 1 - num_warmup) / pure_inf_time
                print(f'Overall fps: {fps:.2f} img / s\n')
                benchmark_dict[f'overall_fps_{time_index + 1}'] = round(fps, 2)
                overall_fps_list.append(fps)
                break
    benchmark_dict['average_fps'] = round(np.mean(overall_fps_list), 2)
    benchmark_dict['fps_variance'] = round(np.var(overall_fps_list), 4)
    print(f'Average fps of {repeat_times} evaluations: '
          f'{benchmark_dict["average_fps"]}')
    print(f'The variance of {repeat_times} evaluations: '
          f'{benchmark_dict["fps_variance"]}')
    mmcv.dump(benchmark_dict, json_file, indent=4)


if __name__ == '__main__':
    main()