#!/usr/bin/env python
# vim: set fileencoding=utf-8 :

# Adpated from:
# https://github.com/pytorch/pytorch/blob/master/torch/hub.py
# https://github.com/facebookresearch/maskrcnn-benchmark/blob/master/maskrcnn_benchmark/utils/checkpoint.py

import errno
import hashlib
import os
import re
import shutil
import sys
import tempfile
import torch
import warnings
import zipfile
from urllib.request import urlopen
from urllib.parse import urlparse
from tqdm import tqdm 

modelurls = {
    "vgg11": "https://download.pytorch.org/models/vgg11-bbd30ac9.pth",
    "vgg13": "https://download.pytorch.org/models/vgg13-c768596a.pth",
    "vgg16": "https://download.pytorch.org/models/vgg16-397923af.pth",
    "vgg19": "https://download.pytorch.org/models/vgg19-dcbb9e9d.pth",
    "vgg11_bn": "https://download.pytorch.org/models/vgg11_bn-6002323d.pth",
    "vgg13_bn": "https://download.pytorch.org/models/vgg13_bn-abd245e5.pth",
    "vgg16_bn": "https://download.pytorch.org/models/vgg16_bn-6c64b313.pth",
    "vgg19_bn": "https://download.pytorch.org/models/vgg19_bn-c79401a0.pth",
    "resnet18": "https://download.pytorch.org/models/resnet18-5c106cde.pth",
    "resnet34": "https://download.pytorch.org/models/resnet34-333f7ec4.pth",
    "resnet50": "https://download.pytorch.org/models/resnet50-19c8e357.pth",
    "resnet101": "https://download.pytorch.org/models/resnet101-5d3b4d8f.pth",
    "resnet152": "https://download.pytorch.org/models/resnet152-b121ed2d.pth",
    "resnet50_SIN_IN": "https://bitbucket.org/robert_geirhos/texture-vs-shape-pretrained-models/raw/60b770e128fffcbd8562a3ab3546c1a735432d03/resnet50_finetune_60_epochs_lr_decay_after_30_start_resnet50_train_45_epochs_combined_IN_SF-ca06340c.pth.tar",
    "mobilenetv2": "https://dl.dropboxusercontent.com/s/4nie4ygivq04p8y/mobilenet_v2.pth.tar",
    }

def _download_url_to_file(url, dst, hash_prefix, progress):
    file_size = None
    u = urlopen(url)
    meta = u.info()
    if hasattr(meta, 'getheaders'):
        content_length = meta.getheaders("Content-Length")
    else:
        content_length = meta.get_all("Content-Length")
    if content_length is not None and len(content_length) > 0:
        file_size = int(content_length[0])

    f = tempfile.NamedTemporaryFile(delete=False)
    try:
        if hash_prefix is not None:
            sha256 = hashlib.sha256()
        with tqdm(total=file_size, disable=not progress) as pbar:
            while True:
                buffer = u.read(8192)
                if len(buffer) == 0:
                    break
                f.write(buffer)
                if hash_prefix is not None:
                    sha256.update(buffer)
                pbar.update(len(buffer))

        f.close()
        if hash_prefix is not None:
            digest = sha256.hexdigest()
            if digest[:len(hash_prefix)] != hash_prefix:
                raise RuntimeError('invalid hash value (expected "{}", got "{}")'
                                   .format(hash_prefix, digest))
        shutil.move(f.name, dst)
    finally:
        f.close()
        if os.path.exists(f.name):
            os.remove(f.name)

HASH_REGEX = re.compile(r'-([a-f0-9]*)\.')

def cache_url(url, model_dir=None, progress=True):
    r"""Loads the Torch serialized object at the given URL.
    If the object is already present in `model_dir`, it's deserialized and
    returned. The filename part of the URL should follow the naming convention
    ``filename-<sha256>.ext`` where ``<sha256>`` is the first eight or more
    digits of the SHA256 hash of the contents of the file. The hash is used to
    ensure unique names and to verify the contents of the file.
    The default value of `model_dir` is ``$TORCH_HOME/models`` where
    ``$TORCH_HOME`` defaults to ``~/.torch``. The default directory can be
    overridden with the ``$TORCH_MODEL_ZOO`` environment variable.
    Args:
        url (string): URL of the object to download
        model_dir (string, optional): directory in which to save the object
        progress (bool, optional): whether or not to display a progress bar to stderr

    """
    if model_dir is None:
        torch_home = os.path.expanduser(os.getenv("TORCH_HOME", "~/.torch"))
        model_dir = os.getenv("TORCH_MODEL_ZOO", os.path.join(torch_home, "models"))
    if not os.path.exists(model_dir):
        os.makedirs(model_dir)
    parts = urlparse(url)
    filename = os.path.basename(parts.path)
    
    cached_file = os.path.join(model_dir, filename)
    if not os.path.exists(cached_file):
        sys.stderr.write('Downloading: "{}" to {}\n'.format(url, cached_file))
        hash_prefix = HASH_REGEX.search(filename)
        if hash_prefix is not None:
            hash_prefix = hash_prefix.group(1)
        _download_url_to_file(url, cached_file, hash_prefix, progress=progress)
    
    return cached_file