Upstream.py

from flask import Flask, request, Response
import os
import re

app = Flask(__name__)

@app.route('/download/<filename>')
def dmain_download(filename):
    return download_file(filename)

def download_file(filename):
    file_path = os.path.join('/tmp', filename) # Update this, if the directory is different
    test_header = request.headers.get('Test-Header')

    if not os.path.exists(file_path):
        return "File not found", 404
    file_size = os.path.getsize(file_path)

    print("------------------------------------------------------------------------")
    range_header = request.headers.get('Range')
    print(f"Slice Range Header: {range_header}")
    print("------------------------------------------------------------------------")
    if not range_header:
        return send_full_file(file_path, filename, file_size)

    try:
        byte1, byte2 = 0, None

        m = re.search(r'bytes=(\d+)-(\d*)', range_header)
        if m:
            g = m.groups()
            byte1 = int(g[0])
            if g[1]:
                byte2 = int(g[1])

        # Adjust ranges if they are invalid
        if byte1 >= file_size:
            # If the start byte is greater than or equal to the file size,
            # it's an invalid range request per HTTP RFC.
            return Response(status=416, headers={'Content-Range': f'bytes */{file_size}'})

        byte2 = min(byte2 if byte2 else file_size - 1, file_size - 1)  # Clamp byte2 to file size
        length = byte2 - byte1 + 1

        with open(file_path, 'rb') as f:
            f.seek(byte1)
            data = f.read(length)

        rv = Response(data, 206, mimetype='application/octet-stream', direct_passthrough=True)
        rv.headers['Content-Range'] = f'bytes {byte1}-{byte2}/{file_size}'
        rv.headers['Accept-Ranges'] = 'bytes'
        rv.headers['Content-Length'] = str(length)
        rv.headers['Content-Disposition'] = f'attachment; filename={filename}'

        return rv

    except Exception as e:
        print(f"Error handling range request: {e}")
        return "Internal Server Error", 500


def send_full_file(file_path, filename, file_size):
    with open(file_path, 'rb') as f:
        data = f.read()

    rv = Response(data, 200, mimetype='application/octet-stream', direct_passthrough=True)
    rv.headers['Accept-Ranges'] = 'bytes'
    rv.headers['Content-Length'] = str(file_size)
    rv.headers['Content-Disposition'] = f'attachment; filename={filename}'
    return rv

if __name__ == '__main__':
    app.run(debug=True)