#!/usr/bin/env python3
# Copyright 2020 The Pigweed Authors
#
# 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
#
#     https://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.
"""File Helper Functions."""

import glob
import hashlib
import logging
import os
import shutil
import sys
import tarfile
import urllib.request
import zipfile
from pathlib import Path
from typing import List

_LOG = logging.getLogger(__name__)


class InvalidChecksumError(Exception):
    pass


def find_files(starting_dir: str,
               patterns: List[str],
               directories_only=False) -> List[str]:
    original_working_dir = os.getcwd()
    if not (os.path.exists(starting_dir) and os.path.isdir(starting_dir)):
        _LOG.error("Directory '%s' does not exist.", starting_dir)
        raise FileNotFoundError

    os.chdir(starting_dir)
    files = []
    for pattern in patterns:
        for file_path in glob.glob(pattern, recursive=True):
            if not directories_only or (directories_only
                                        and os.path.isdir(file_path)):
                files.append(file_path)
    os.chdir(original_working_dir)
    return sorted(files)


def sha256_sum(file_name):
    hash_sha256 = hashlib.sha256()
    with open(file_name, "rb") as file_handle:
        for chunk in iter(lambda: file_handle.read(4096), b""):
            hash_sha256.update(chunk)
    return hash_sha256.hexdigest()


def md5_sum(file_name):
    hash_md5 = hashlib.md5()
    with open(file_name, "rb") as file_handle:
        for chunk in iter(lambda: file_handle.read(4096), b""):
            hash_md5.update(chunk)
    return hash_md5.hexdigest()


def verify_file_checksum(file_path,
                         expected_checksum,
                         sum_function=sha256_sum):
    downloaded_checksum = sum_function(file_path)
    try:
        if downloaded_checksum != expected_checksum:
            raise InvalidChecksumError
    except InvalidChecksumError:
        _LOG.exception("Invalid %s\n"
                       "%s %s\n"
                       "%s (expected)",
                       sum_function.__name__, downloaded_checksum,
                       os.path.basename(file_path), expected_checksum)
        # Exit to stop installation
        return sys.exit(1)

    _LOG.info("  %s:", sum_function.__name__)
    _LOG.info("  %s %s", downloaded_checksum, os.path.basename(file_path))
    return True


def download_to_cache(url: str,
                      expected_md5sum=None,
                      expected_sha256sum=None,
                      cache_directory=".cache") -> str:

    cache_dir = os.path.realpath(
        os.path.expanduser(os.path.expandvars(cache_directory)))
    downloaded_file = os.path.join(cache_dir, url.split("/")[-1])

    if not os.path.exists(downloaded_file):
        _LOG.info("Downloading: %s", url)
        urllib.request.urlretrieve(url, filename=downloaded_file)

    if os.path.exists(downloaded_file):
        _LOG.info("Downloaded: %s", downloaded_file)
        if expected_sha256sum:
            verify_file_checksum(downloaded_file,
                                 expected_sha256sum,
                                 sum_function=sha256_sum)
        elif expected_md5sum:
            verify_file_checksum(downloaded_file,
                                 expected_md5sum,
                                 sum_function=md5_sum)

    return downloaded_file


def extract_zipfile(archive_file: str, dest_dir: str):
    with zipfile.ZipFile(archive_file) as archive:
        archive.extractall(path=dest_dir)


def extract_tarfile(archive_file: str, dest_dir: str):
    with tarfile.open(archive_file, 'r') as archive:
        archive.extractall(path=dest_dir)


def extract_archive(archive_file: str,
                    dest_dir: str,
                    cache_dir: str,
                    remove_single_toplevel_folder=True):
    """Extract a tar or zip file.

    Args:
        archive_file (str): Absolute path to the archive file.
        dest_dir (str): Extraction destination directory.
        cache_dir (str): Directory where temp files can be created.
        remove_single_toplevel_folder (bool): If the archive contains only a
            single folder move the contents of that into the destination
            directory.
    """
    # Make a temporary directory to extract files into
    temp_extract_dir = os.path.join(cache_dir,
                                    "." + os.path.basename(archive_file))
    os.makedirs(temp_extract_dir, exist_ok=True)

    _LOG.info("Extracting: %s", archive_file)
    if zipfile.is_zipfile(archive_file):
        extract_zipfile(archive_file, temp_extract_dir)
    elif tarfile.is_tarfile(archive_file):
        extract_tarfile(archive_file, temp_extract_dir)
    else:
        _LOG.error("Unknown archive format: %s", archive_file)
        return sys.exit(1)

    _LOG.info("Installing into: %s", dest_dir)
    path_to_extracted_files = temp_extract_dir

    extracted_top_level_files = os.listdir(temp_extract_dir)
    # Check if tarfile has only one folder
    # If yes, make that the new path_to_extracted_files
    if remove_single_toplevel_folder and len(extracted_top_level_files) == 1:
        path_to_extracted_files = os.path.join(temp_extract_dir,
                                               extracted_top_level_files[0])

    # Move extracted files to dest_dir
    extracted_files = os.listdir(path_to_extracted_files)
    for file_name in extracted_files:
        source_file = os.path.join(path_to_extracted_files, file_name)
        dest_file = os.path.join(dest_dir, file_name)
        shutil.move(source_file, dest_file)

    # rm -rf temp_extract_dir
    shutil.rmtree(temp_extract_dir, ignore_errors=True)

    # Return List of extracted files
    return list(Path(dest_dir).rglob("*"))


def remove_empty_directories(directory):
    """Recursively remove empty directories."""

    for path in sorted(Path(directory).rglob("*"), reverse=True):
        # If broken symlink
        if path.is_symlink() and not path.exists():
            path.unlink()
        # if empty directory
        elif path.is_dir() and len(os.listdir(path)) == 0:
            path.rmdir()