"""HTTP proxy that injects our webmention endpoint.
"""
import datetime
import urllib.parse

import flask
from flask import request
import requests

from app import app, cache
import common
from common import error

LINK_HEADER = '<%s>; rel="webmention"'
CACHE_TIME = datetime.timedelta(seconds=15)


@app.get(r'/wm/<path:url>')
@cache.cached(timeout=CACHE_TIME.total_seconds(), query_string=True,
              response_filter=common.not_5xx)
def add_wm(url=None):
    """Proxies HTTP requests and adds Link header to our webmention endpoint."""
    url = urllib.parse.unquote(url)
    if not url.startswith('http://') and not url.startswith('https://'):
        return error('URL must start with http:// or https://')

    try:
        got = common.requests_get(url)
    except requests.exceptions.Timeout as e:
        return error(str(e), status=504, exc_info=True)
    except requests.exceptions.RequestException as e:
        return error(str(e), status=502, exc_info=True)

    resp = flask.make_response(got.content, got.status_code, dict(got.headers))
    resp.headers.add('Link', LINK_HEADER % (request.args.get('endpoint') or
                                            request.host_url + 'webmention'))
    return resp