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"""
Update the CDFs parameters of a trained model.

To be called on a model checkpoint after training. This will update the internal
CDFs related buffers required for entropy coding.
"""
import argparse
import hashlib
import sys

from pathlib import Path
from typing import Dict

import torch

from compressai.models.google import (
    FactorizedPrior,
    JointAutoregressiveHierarchicalPriors,
    MeanScaleHyperprior,
    ScaleHyperprior,
)
from compressai.models.video.google import ScaleSpaceFlow
from compressai.zoo import load_state_dict
from compressai.zoo.image import model_architectures as image_architectures
from compressai.zoo.image_vbr import model_architectures as image_architectures_vbr


def sha256_file(filepath: Path, len_hash_prefix: int = 8) -> str:
    # from pytorch github repo
    sha256 = hashlib.sha256()
    with filepath.open("rb") as f:
        while True:
            buf = f.read(8192)
            if len(buf) == 0:
                break
            sha256.update(buf)
    digest = sha256.hexdigest()

    return digest[:len_hash_prefix]


def load_checkpoint(filepath: Path, arch: str) -> Dict[str, torch.Tensor]:
    checkpoint = torch.load(filepath, map_location="cpu")

    if "network" in checkpoint:
        state_dict = checkpoint["network"]
    elif "state_dict" in checkpoint:
        state_dict = checkpoint["state_dict"]
    else:
        state_dict = checkpoint
    # if arch in ["bmshj2018-hyperprior-vbr", "mbt2018-mean-vbr"]:
    #     state_dict = load_state_dict(state_dict, vr_entbttlnck=True)
    # else:
    state_dict = load_state_dict(state_dict)
    return state_dict


description = """
Export a trained model to a new checkpoint with updated CDFs and a
hash prefix so that it can be loaded later via `load_state_dict_from_url`.
""".strip()

models = {
    "factorized-prior": FactorizedPrior,
    "jarhp": JointAutoregressiveHierarchicalPriors,
    "mean-scale-hyperprior": MeanScaleHyperprior,
    "scale-hyperprior": ScaleHyperprior,
    "ssf2020": ScaleSpaceFlow,
}
models.update(image_architectures)
models.update(image_architectures_vbr)


def setup_args():
    parser = argparse.ArgumentParser(description=description)
    parser.add_argument(
        "filepath", type=str, help="Path to the checkpoint model to be exported."
    )
    parser.add_argument("-n", "--name", type=str, help="Exported model name.")
    parser.add_argument("-d", "--dir", type=str, help="Exported model directory.")
    parser.add_argument(
        "--no-update",
        action="store_true",
        default=False,
        help="Do not update the model CDFs parameters.",
    )
    parser.add_argument(
        "-a",
        "--architecture",
        default="scale-hyperprior",
        choices=models.keys(),
        help="Set model architecture (default: %(default)s).",
    )
    return parser


def main(argv):
    args = setup_args().parse_args(argv)

    filepath = Path(args.filepath).resolve()
    if not filepath.is_file():
        raise RuntimeError(f'"{filepath}" is not a valid file.')

    state_dict = load_checkpoint(filepath, args.architecture)

    model_cls_or_entrypoint = models[args.architecture]
    if not isinstance(model_cls_or_entrypoint, type):
        model_cls = model_cls_or_entrypoint()
    else:
        model_cls = model_cls_or_entrypoint
    if args.architecture in ["bmshj2018-hyperprior-vbr", "mbt2018-mean-vbr"]:
        net = model_cls.from_state_dict(state_dict, vr_entbttlnck=True)
    else:
        net = model_cls.from_state_dict(state_dict)

    if not args.no_update:
        net.update(force=True)
    state_dict = net.state_dict()

    if not args.name:
        filename = filepath
        while filename.suffixes:
            filename = Path(filename.stem)
    else:
        filename = args.name

    ext = "".join(filepath.suffixes)

    if args.dir is not None:
        output_dir = Path(args.dir)
        Path(output_dir).mkdir(exist_ok=True)
    else:
        output_dir = Path.cwd()

    filepath = output_dir / f"{filename}{ext}"
    torch.save(state_dict, filepath)
    hash_prefix = sha256_file(filepath)

    filepath.rename(f"{output_dir}/{filename}-{hash_prefix}{ext}")


if __name__ == "__main__":
    main(sys.argv[1:])
