from flask import request, current_app, url_for
from urllib.parse import urlsplit, urlunsplit


def prefixed_url_for(endpoint, **values):
    prefix = request.headers.get('X-Forwarded-Prefix', '')
    scheme = request.headers.get('X-Forwarded-Proto', request.scheme)
    host = request.headers.get('Host', request.host)
    current_app.logger.debug(f'prefix: {prefix}, scheme: {scheme}, host: {host}')

    external = values.pop('_external', False)
    generated_url = url_for(endpoint, **values)

    if external:
        path, query, fragment = urlsplit(generated_url)[2:5]
        new_path = prefix + path
        return urlunsplit((scheme, host, new_path, query, fragment))
    else:
        return prefix + generated_url