#!/usr/bin/env python3
"""S-16b (#123): prove distributed tracing works end to end.

Generate anonymous BFF traffic (GET /openbaar/register, which the BFF serves by
calling projection-api — no auth, no OpenZaak egress), then query Tempo and assert
that ONE trace contains spans from both `bff` and `projection-api`. That proves the
services export OTLP to Tempo AND that the W3C traceparent propagates across the
HttpClient hop, stitching the request into a single connected trace.

Stdlib only (urllib/json) so it runs in a bare python:3-slim container in-network.
"""
import json
import os
import sys
import time
import urllib.error
import urllib.parse
import urllib.request

BFF = os.environ["BFF"]        # http://<bff-ip>:8080
TEMPO = os.environ["TEMPO"]    # http://<tempo-ip>:3200
TIMEOUT = int(os.environ.get("TRACING_TIMEOUT", "90"))
WANT = {"bff", "projection-api"}  # the two services that must share one trace


def _get(url):
    with urllib.request.urlopen(url, timeout=10) as r:
        return r.read()


def generate_traffic():
    # A non-2xx still produces spans; only total unreachability of the BFF is fatal.
    for _ in range(3):
        try:
            _get(f"{BFF}/openbaar/register")
        except urllib.error.HTTPError:
            pass


def search_trace_ids():
    q = urllib.parse.quote('{ resource.service.name = "bff" }')
    try:
        data = json.loads(_get(f"{TEMPO}/api/search?q={q}&limit=50"))
    except Exception:
        return []
    return [t["traceID"] for t in data.get("traces", [])]


def services_in_trace(trace_id):
    try:
        data = json.loads(_get(f"{TEMPO}/api/traces/{trace_id}"))
    except Exception:
        return set()
    names = set()
    for batch in data.get("batches", []):
        for attr in batch.get("resource", {}).get("attributes", []):
            if attr.get("key") == "service.name":
                names.add(attr.get("value", {}).get("stringValue"))
    return names


def tempo_ingest_state():
    """#156: distinguish a broken trace chain from Tempo dropping spans. `ingester_clients` is 0
    when the distributor has evicted its (single, in-process) ingester over a failed loopback
    health check — pushes fail and spans are lost, which looks identical to missing instrumentation
    from here. Diagnostics only; never fails the check."""
    try:
        for line in _get(f"{TEMPO}/metrics").decode().splitlines():
            if line.startswith("tempo_distributor_ingester_clients "):
                return f"tempo {line.strip()} (0 = no ingester in the pool — evicted, so pushes\n       are failing and spans are being dropped; see #156)"
    except Exception as e:
        return f"tempo /metrics unreadable: {e}"
    return "tempo_distributor_ingester_clients not reported"


def main():
    deadline = time.time() + TIMEOUT
    generate_traffic()
    seen = set()
    while time.time() < deadline:
        for tid in search_trace_ids():
            names = services_in_trace(tid)
            seen |= names
            if WANT.issubset(names):
                print(f"OK — trace {tid} spans {sorted(names)}")
                return 0
        time.sleep(3)
        generate_traffic()
    print(f"FAIL — no single trace spanned {sorted(WANT)}; services seen: {sorted(seen)}",
          file=sys.stderr)
    print(f"       {tempo_ingest_state()}", file=sys.stderr)
    return 1


if __name__ == "__main__":
    sys.exit(main())