import os
import re

from django.core.files.uploadedfile import SimpleUploadedFile, \
    TemporaryUploadedFile
from pytube import YouTube
import requests

from boards.utils import validate_file_size

YOUTUBE_VIDEO_FORMAT = 'webm'

HTTP_RESULT_OK = 200

HEADER_CONTENT_LENGTH = 'content-length'
HEADER_CONTENT_TYPE = 'content-type'

FILE_DOWNLOAD_CHUNK_BYTES = 200000

YOUTUBE_URL = re.compile(r'https?://((www\.)?youtube\.com/watch\?v=|youtu.be/)[-\w]+')


class Downloader:
    @staticmethod
    def handles(url: str) -> bool:
        return False

    @staticmethod
    def download(url: str):
        # Verify content headers
        response_head = requests.head(url, verify=False)
        content_type = response_head.headers[HEADER_CONTENT_TYPE].split(';')[0]
        length_header = response_head.headers.get(HEADER_CONTENT_LENGTH)
        if length_header:
            length = int(length_header)
            validate_file_size(length)
        # Get the actual content into memory
        response = requests.get(url, verify=False, stream=True)

        # Download file, stop if the size exceeds limit
        size = 0

        # Set a dummy file name that will be replaced
        # anyway, just keep the valid extension
        filename = 'file.' + content_type.split('/')[1]

        file = TemporaryUploadedFile(filename, content_type, 0, None, None)
        for chunk in response.iter_content(FILE_DOWNLOAD_CHUNK_BYTES):
            size += len(chunk)
            validate_file_size(size)
            file.write(chunk)

        if response.status_code == HTTP_RESULT_OK:
            return file


def download(url):
    for downloader in Downloader.__subclasses__():
        if downloader.handles(url):
            return downloader.download(url)
    # If nobody of the specific downloaders handles this, use generic
    # one
    return Downloader.download(url)


class YouTubeDownloader(Downloader):
    @staticmethod
    def download(url: str):
        yt = YouTube()
        yt.from_url(url)
        videos = yt.filter(YOUTUBE_VIDEO_FORMAT)
        if len(videos) > 0:
            video = videos[0]
            return Downloader.download(video.url)

    @staticmethod
    def handles(url: str) -> bool:
        return YOUTUBE_URL.match(url)