# Copyright (c) 2015-2018. Mount Sinai School of Medicine
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from __future__ import print_function, division, absolute_import

import hashlib
from os import makedirs, environ
from os.path import join, exists, split, splitext
import re

from shutil import rmtree
import appdirs

def ensure_dir(path):
    if not exists(path):
        makedirs(path)

def get_data_dir(subdir=None, envkey=None):
    if envkey and environ.get(envkey):
        envdir = environ[envkey]
        if subdir:
            return join(envdir, subdir)
        else:
            return envdir
    return appdirs.user_cache_dir(subdir if subdir else "datacache")

def build_path(filename, subdir=None):
    data_dir = get_data_dir(subdir)
    ensure_dir(data_dir)
    return join(data_dir, filename)

def clear_cache(subdir=None):
    data_dir = get_data_dir(subdir)
    rmtree(data_dir)

def normalize_filename(filename):
    """
    Remove special characters and shorten if name is too long
    """
    # if the url pointed to a directory then just replace all the special chars
    filename = re.sub("/|\\|;|:|\?|=", "_", filename)

    if len(filename) > 150:
        prefix = hashlib.md5(filename).hexdigest()
        filename = prefix + filename[-140:]

    return filename

def build_local_filename(download_url=None, filename=None, decompress=False):
    """
    Determine which local filename to use based on the file's source URL,
    an optional desired filename, and whether a compression suffix needs
    to be removed
    """
    assert download_url or filename, "Either filename or URL must be specified"

    # if no filename provided, use the original filename on the server
    if not filename:
        digest = hashlib.md5(download_url.encode('utf-8')).hexdigest()
        parts = split(download_url)
        filename = digest + "." + "_".join(parts)

    filename = normalize_filename(filename)

    if decompress:
        (base, ext) = splitext(filename)
        if ext in (".gz", ".zip"):
            filename = base

    return filename
