# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
#
# This source code is licensed under the license found in the
# LICENSE file in the root directory of this source tree.

import argparse
import subprocess
from collections import OrderedDict

import torch
from mmengine.runner import CheckpointLoader


def swin_converter(ckpt):

    new_ckpt = OrderedDict()

    def correct_unfold_reduction_order(x):
        out_channel, in_channel = x.shape
        x = x.reshape(out_channel, 4, in_channel // 4)
        x = x[:, [0, 2, 1, 3], :].transpose(1,
                                            2).reshape(out_channel, in_channel)
        return x

    def correct_unfold_norm_order(x):
        in_channel = x.shape[0]
        x = x.reshape(4, in_channel // 4)
        x = x[[0, 2, 1, 3], :].transpose(0, 1).reshape(in_channel)
        return x

    for k, v in ckpt.items():
        if k.startswith('backbone.layers'):
            new_v = v
            if 'attn.' in k:
                new_k = k.replace('attn.', 'attn.w_msa.')
            elif 'mlp.' in k:
                if 'mlp.fc1.' in k:
                    new_k = k.replace('mlp.fc1.', 'ffn.layers.0.0.')
                elif 'mlp.fc2.' in k:
                    new_k = k.replace('mlp.fc2.', 'ffn.layers.1.')
                else:
                    new_k = k.replace('mlp.', 'ffn.')
            elif 'downsample' in k:
                new_k = k
                if 'reduction.' in k:
                    new_v = correct_unfold_reduction_order(v)
                elif 'norm.' in k:
                    new_v = correct_unfold_norm_order(v)
            else:
                new_k = k
            new_k = new_k.replace('layers', 'stages', 1)
        elif k.startswith('backbone.patch_embed'):
            new_v = v
            if 'proj' in k:
                new_k = k.replace('proj', 'projection')
            else:
                new_k = k
        else:
            new_v = v
            new_k = k

        new_ckpt[new_k] = new_v

    return new_ckpt


def main():
    parser = argparse.ArgumentParser(
        description='Convert keys to mmdet style.')
    parser.add_argument('src', help='src model path or url')
    # The dst path must be a full path of the new checkpoint.
    parser.add_argument('dst', help='save path')
    args = parser.parse_args()

    checkpoint = CheckpointLoader.load_checkpoint(args.src, map_location='cpu')

    if 'state_dict' in checkpoint:
        state_dict = checkpoint['state_dict']
    else:
        state_dict = checkpoint
    torch.save(swin_converter(state_dict), args.dst)

    sha = subprocess.check_output(['sha256sum', args.dst]).decode()
    final_file = args.dst.replace('.pth', '') + '-{}.pth'.format(sha[:8])
    subprocess.Popen(['mv', args.dst, final_file])
    print(f'Done!!, save to {final_file}')


if __name__ == '__main__':
    main()