{
  lib,
  pkgs,
  ...
}:
let
  mockGrafana = ./mock-grafana-server.py;
  script = ../services/llama-cpp-annotations.py;
  python = pkgs.python3;

  mockLlamaCpp = pkgs.writeText "mock-llama-cpp-server.py" ''
    import http.server, json, sys, os

    PORT = int(sys.argv[1])
    STATE_FILE = sys.argv[2]

    if not os.path.exists(STATE_FILE):
        with open(STATE_FILE, "w") as f:
            json.dump([{"id": 0, "is_processing": False, "next_token": {"n_decoded": 0}}], f)

    class Handler(http.server.BaseHTTPRequestHandler):
        def log_message(self, fmt, *args):
            pass

        def _json(self, code, body):
            data = json.dumps(body).encode()
            self.send_response(code)
            self.send_header("Content-Type", "application/json")
            self.end_headers()
            self.wfile.write(data)

        def do_GET(self):
            if self.path == "/slots":
                with open(STATE_FILE) as f:
                    slots = json.load(f)
                self._json(200, slots)
            else:
                self.send_response(404)
                self.end_headers()

        def do_POST(self):
            if self.path == "/test/set-slots":
                length = int(self.headers.get("Content-Length", 0))
                body = json.loads(self.rfile.read(length)) if length else []
                with open(STATE_FILE, "w") as f:
                    json.dump(body, f)
                self._json(200, {"ok": True})
            else:
                self.send_response(404)
                self.end_headers()

    http.server.HTTPServer(("127.0.0.1", PORT), Handler).serve_forever()
  '';
in
pkgs.testers.runNixOSTest {
  name = "llama-cpp-annotations";

  nodes.machine =
    { pkgs, ... }:
    {
      environment.systemPackages = [
        pkgs.python3
        pkgs.curl
      ];
    };

  testScript = ''
    import json
    import time

    GRAFANA_PORT = 13000
    LLAMA_PORT = 16688
    ANNOTS_FILE = "/tmp/annotations.json"
    SLOTS_FILE = "/tmp/llama-slots.json"
    STATE_FILE = "/tmp/llama-annot-state.json"
    PYTHON = "${python}/bin/python3"
    MOCK_GRAFANA = "${mockGrafana}"
    MOCK_LLAMA = "${mockLlamaCpp}"
    SCRIPT = "${script}"

    def read_annotations():
        out = machine.succeed(f"cat {ANNOTS_FILE} 2>/dev/null || echo '[]'")
        return json.loads(out.strip())

    def set_slots(slots):
        machine.succeed(
            f"curl -sf -X POST http://127.0.0.1:{LLAMA_PORT}/test/set-slots "
            f"-H 'Content-Type: application/json' "
            f"-d '{json.dumps(slots)}'"
        )

    start_all()
    machine.wait_for_unit("multi-user.target")

    with subtest("Start mock services"):
        machine.succeed(f"echo '[]' > {ANNOTS_FILE}")
        machine.succeed(
            f"systemd-run --unit=mock-grafana {PYTHON} {MOCK_GRAFANA} {GRAFANA_PORT} {ANNOTS_FILE}"
        )
        machine.succeed(
            f"echo '[{{\"id\": 0, \"is_processing\": false, \"next_token\": {{\"n_decoded\": 0}}}}]' > {SLOTS_FILE}"
        )
        machine.succeed(
            f"systemd-run --unit=mock-llama {PYTHON} {MOCK_LLAMA} {LLAMA_PORT} {SLOTS_FILE}"
        )
        machine.wait_until_succeeds(
            f"curl -sf http://127.0.0.1:{GRAFANA_PORT}/api/annotations -X POST "
            f"-H 'Content-Type: application/json' -d '{{\"text\":\"ping\",\"tags\":[]}}' | grep -q id",
            timeout=10,
        )
        machine.wait_until_succeeds(
            f"curl -sf http://127.0.0.1:{LLAMA_PORT}/slots | grep -q is_processing",
            timeout=10,
        )
        machine.succeed(f"echo '[]' > {ANNOTS_FILE}")

    with subtest("Start annotation service"):
        machine.succeed(
            f"systemd-run --unit=llama-annot "
            f"--setenv=LLAMA_CPP_URL=http://127.0.0.1:{LLAMA_PORT} "
            f"--setenv=GRAFANA_URL=http://127.0.0.1:{GRAFANA_PORT} "
            f"--setenv=STATE_FILE={STATE_FILE} "
            f"--setenv=POLL_INTERVAL=2 "
            f"{PYTHON} {SCRIPT}"
        )
        time.sleep(3)

    with subtest("No annotations when slots are idle"):
        annots = read_annotations()
        assert annots == [], f"Expected no annotations, got: {annots}"

    with subtest("Annotation created when slot starts processing"):
        set_slots([{"id": 0, "is_processing": True, "next_token": {"n_decoded": 0}}])
        machine.wait_until_succeeds(
            f"cat {ANNOTS_FILE} | {PYTHON} -c "
            f"\"import sys,json; a=json.load(sys.stdin); exit(0 if a else 1)\"",
            timeout=15,
        )
        annots = read_annotations()
        assert len(annots) == 1, f"Expected 1 annotation, got: {annots}"
        assert "llama-cpp" in annots[0].get("tags", []), f"Missing tag: {annots[0]}"
        assert "slot 0" in annots[0]["text"], f"Missing slot info: {annots[0]['text']}"
        assert "timeEnd" not in annots[0], f"timeEnd should not be set: {annots[0]}"

    with subtest("Annotation closed when slot stops processing"):
        set_slots([{"id": 0, "is_processing": False, "next_token": {"n_decoded": 42}}])
        machine.wait_until_succeeds(
            f"cat {ANNOTS_FILE} | {PYTHON} -c "
            f"\"import sys,json; a=json.load(sys.stdin); exit(0 if a and 'timeEnd' in a[0] else 1)\"",
            timeout=15,
        )
        annots = read_annotations()
        assert len(annots) == 1, f"Expected 1, got: {annots}"
        assert "timeEnd" in annots[0], f"timeEnd missing: {annots[0]}"
        assert annots[0]["timeEnd"] > annots[0]["time"], "timeEnd should be after time"
        assert "42 tokens" in annots[0].get("text", ""), f"Token count missing: {annots[0]}"

    with subtest("State survives restart"):
        set_slots([{"id": 0, "is_processing": True, "next_token": {"n_decoded": 0}}])
        machine.wait_until_succeeds(
            f"cat {ANNOTS_FILE} | {PYTHON} -c "
            f"\"import sys,json; a=json.load(sys.stdin); exit(0 if len(a)==2 else 1)\"",
            timeout=15,
        )
        machine.succeed("systemctl stop llama-annot || true")
        time.sleep(1)
        machine.succeed(
            f"systemd-run --unit=llama-annot-2 "
            f"--setenv=LLAMA_CPP_URL=http://127.0.0.1:{LLAMA_PORT} "
            f"--setenv=GRAFANA_URL=http://127.0.0.1:{GRAFANA_PORT} "
            f"--setenv=STATE_FILE={STATE_FILE} "
            f"--setenv=POLL_INTERVAL=2 "
            f"{PYTHON} {SCRIPT}"
        )
        time.sleep(4)
        annots = read_annotations()
        assert len(annots) == 2, f"Restart should not duplicate, got: {annots}"
  '';
}