#!/usr/bin/env python3
"""Health-only check before a future authorized run; never reserves or executes calls."""
import argparse
import json
from urllib import error, request
from urllib.parse import urlsplit


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


def probe(endpoint, timeout=5, opener=None):
    parsed = urlsplit(endpoint)
    if (parsed.scheme not in {'http', 'https'} or not parsed.hostname
            or parsed.username or parsed.password or parsed.query or parsed.fragment
            or parsed.path not in {'', '/'}):
        raise ValueError('Use an HTTP(S) service origin without credentials, path or query')
    if not 0 < timeout <= 15:
        raise ValueError('Health timeout must be greater than zero and at most 15 seconds')
    opener = opener or request.build_opener(NoRedirect())
    result = {'endpoint': endpoint.rstrip('/'), 'ready': False,
              'inference_calls': 0, 'attempts_reserved': 0,
              'limit': 'Health only; profile, provider, token enforcement and authorization are unverified.'}
    try:
        req = request.Request(endpoint.rstrip('/') + '/health', method='GET')
        with opener.open(req, timeout=timeout) as response:
            body = response.read(4097)
            if response.status != 200 or len(body) > 4096:
                result['reason'] = 'invalid_health_response'
            else:
                data = json.loads(body)
                result['ready'] = isinstance(data, dict) and data.get('status') == 'ok'
                result['reason'] = 'health_ok' if result['ready'] else 'invalid_health_response'
    except error.HTTPError as exc:
        result.update(reason='health_http_error', http_status=exc.code)
    except (error.URLError, TimeoutError, OSError):
        result['reason'] = 'health_unreachable'
    except (ValueError, UnicodeError):
        result['reason'] = 'invalid_health_response'
    return result


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--endpoint', default='http://127.0.0.1:18081')
    parser.add_argument('--timeout', type=float, default=5)
    args = parser.parse_args()
    try:
        result = probe(args.endpoint, args.timeout)
    except ValueError as exc:
        parser.error(str(exc))
    print(json.dumps(result, indent=2))
    return 0 if result['ready'] else 1


if __name__ == '__main__':
    raise SystemExit(main())