import os
import re

def parse_range(header_value, file_size):
    if header_value is None:
        # HTTP Range header range end is inclusive
        return 0, file_size - 1

    match = re.match(r"bytes=(\d*)-(\d*)", header_value.decode())
    start = int(match.group(1)) if match.group(1).strip() != "" else 0
    last = int(match.group(2)) if match.group(2).strip() != "" else file_size - 1
    return start, last

def main(request, response):
    file_extension = request.GET.first(b"extension").decode()
    file_path = os.path.join(request.doc_root, "media", f"movie_300.{file_extension}")
    with open(file_path, "rb") as f:
        f.seek(0, os.SEEK_END)
        file_size = f.tell()

        range_header = request.headers.get("range")
        req_start, req_last = parse_range(range_header, file_size)
        f.seek(req_start, os.SEEK_SET)

        response.add_required_headers = False
        response.writer.write_status(206 if range_header else 200)
        response.writer.write_header("Accept-Ranges", "bytes")
        response.writer.write_header("Content-Type", f"video/{file_extension}")
        if range_header:
            response.writer.write_header("Content-Range", f"bytes {req_start}-{req_last}/{file_size}")
        response.writer.write_header("Content-Length", str(req_last - req_start + 1))
        response.writer.end_headers()

        gap_start = int(file_size * 0.5)
        gap_last = int(file_size * 0.95)

        if gap_start < req_start < gap_last:
            # If the start position is part of the gap, don't send any data
            return

        if req_start < gap_start:
            # If the position is before of the gap, only send data until the
            # gap is reached
            req_last = min(req_last, gap_start)

        size = req_last - req_start + 1
        response.writer.write(f.read(size))