"""Bounded Audit Core transport for the acknowledgment outbox."""
import json
from urllib.error import HTTPError, URLError
from urllib.parse import urlsplit
from urllib.request import Request, HTTPRedirectHandler, ProxyHandler, build_opener


class NoRedirect(HTTPRedirectHandler):
    def redirect_request(self, req, fp, code, msg, headers, newurl):
        return None


class AuditTransport:
    def __init__(self, origin, token_provider, *, allow_internal_http=False):
        parsed = urlsplit(origin)
        internal = parsed.hostname in ('127.0.0.1', '::1') or (parsed.hostname or '').endswith(('.svc', '.svc.cluster.local'))
        if (parsed.scheme != 'https' and not (allow_internal_http and internal and parsed.scheme == 'http')
                or not parsed.hostname or parsed.path or parsed.query or parsed.fragment
                or parsed.username or parsed.password):
            raise ValueError('fixed audit origin required')
        self.url = origin + '/v1/events'
        self.token_provider = token_provider
        self.opener = build_opener(ProxyHandler({}), NoRedirect())

    def __call__(self, event):
        token = self.token_provider()
        if (not isinstance(token, str) or not 1 <= len(token) <= 32768
                or any(ord(c) < 33 or ord(c) > 126 for c in token)):
            raise OSError('audit credential unavailable')
        request = Request(self.url, data=json.dumps(event, sort_keys=True, separators=(',', ':')).encode(),
                          headers={'Content-Type': 'application/json', 'Authorization': 'Bearer ' + token,
                                   'Idempotency-Key': event['id']}, method='POST')
        try:
            with self.opener.open(request, timeout=5) as response:
                raw = response.read(65537)
                if len(raw) > 65536:
                    raise OSError('audit response invalid')
                body = json.loads(raw)
                if not isinstance(body, dict):
                    raise ValueError()
                return response.status, body
        except HTTPError as error:
            # Keep no upstream diagnostic body, URL, credential or response text.
            status = error.code
            error.close()
            return status, {}
        except (URLError, ValueError, UnicodeError):
            raise OSError('audit unavailable or invalid response') from None