"""
稳定性实测：真实的初始化、正常关闭、崩溃关闭、链路故障与恢复。

拓扑：Windows 上的 Probe（NativeAOT exe）→ WSL2 里的 Agent → 同一个 WSL 里的 Backend。
Probe↔Agent 走真实的虚拟网络（eth0），Agent↔Backend 走 WSL 里的回环（故障用 tc 注入在 lo 上）。

前提：WSL 里有 Debian（root）和 tc；已发布 linux-x64 的 agent、backend、fleet-enroll（scripts/publish.sh），
以及 Windows 的 probe（dotnet publish backend/probe/src/Monitor.Probe -c Release -r win-x64 -p:PublishAot=true -o backend/artifacts/aot-probe）。

用法：python scripts/stability_wsl.py [场景名 ...]   （不带参数运行全部）
场景：init  graceful  crash  probe_link  backend_link  silent  soak
"""
import ctypes
import json
import os
import subprocess
import sys
import time
import urllib.error
import urllib.request

# 要连的是本机的虚拟网络（WSL），不能走环境变量里的 HTTP(S)_PROXY
OPENER = urllib.request.build_opener(urllib.request.ProxyHandler({}))

ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
PROBE_EXE = os.path.join(ROOT, "backend", "artifacts", "aot-probe", "monitor-probe.exe")
PUB = "/mnt/" + ROOT[0].lower() + ROOT[2:].replace("\\", "/") + "/backend/artifacts/publish"
WORK = os.path.join(os.environ.get("TEMP", "."), "stability")
PORT = 29181
ADMIN_PASSWORD = os.environ.get("MONITOR_ADMIN_PASSWORD", "correct horse battery")  # 测试用后端的初始管理员密码
RESULTS = []
HIDDEN = subprocess.CREATE_NO_WINDOW  # 所有子进程都不弹窗


# ------------------------------------------------------------------ WSL / process helpers

def wsl(cmd, check=True, timeout=120):
    r = subprocess.run(["wsl", "-d", "Debian", "-u", "root", "-e", "bash", "-c", cmd], capture_output=True, text=True, timeout=timeout, creationflags=HIDDEN)
    if check and r.returncode != 0:
        raise RuntimeError(f"wsl failed ({r.returncode}): {cmd}\n{r.stdout}\n{r.stderr}")
    return r.stdout.strip()


WSLIP = wsl("ip -4 addr show eth0 | grep -oP '(?<=inet )[0-9.]+'")
BASE = f"http://{WSLIP}:{PORT}"
TOKEN = ""

LAUNCHER = r"""#!/bin/sh
# start.sh <name> <command...>: run detached, append to <name>.log, record the exit code in <name>.exit
name=$1; shift
rm -f /root/mon/$name.exit
setsid -f sh -c 'cd /root/mon; "$@" >> /root/mon/'$name'.log 2>&1; echo $? > /root/mon/'$name'.exit' sh "$@" < /dev/null
"""


def now():
    return time.time()


def check(name, ok, detail=""):
    RESULTS.append((name, bool(ok), detail))
    print(f"  [{'PASS' if ok else 'FAIL'}] {name}" + (f" - {detail}" if detail else ""), flush=True)
    return ok


def wait_until(cond, timeout, step=0.5):
    start = now()
    while now() - start < timeout:
        try:
            if cond():
                return now() - start
        except Exception:
            pass
        time.sleep(step)
    return None


def api(method, path, body=None, ctype="application/json", timeout=15):
    headers = {"Content-Type": ctype}
    if TOKEN:
        headers["Authorization"] = "Bearer " + TOKEN
    data = None if body is None else json.dumps(body).encode()
    req = urllib.request.Request(BASE + path, data=data, method=method, headers=headers)
    with OPENER.open(req, timeout=timeout) as resp:
        text = resp.read().decode()
        return json.loads(text) if text else None


def backend_up():
    try:
        OPENER.open(BASE + "/healthz", timeout=2)
        return True
    except Exception:
        return False


# ------------------------------------------------------------------ components

def pids(name):
    out = wsl(f"pgrep -x {name} || true")
    return [int(x) for x in out.split()]


def rss_mb(name):
    p = pids(name)
    if not p:
        return None
    return int(wsl(f"ps -o rss= -p {p[0]}")) / 1024


def start_backend():
    wsl(f"cd /root/mon && /root/mon/start.sh backend env ASPNETCORE_URLS=http://0.0.0.0:{PORT} Monitor__DataDirectory=/root/mon/data "
        f"Monitor__InitialAdminUser=admin 'Monitor__InitialAdminPassword={ADMIN_PASSWORD}' Monitor__SecureCookies=false ./monitor-backend")
    return wait_until(backend_up, 30)


def start_agent():
    wsl("/root/mon/start.sh agent ./monitor-agent --config /root/mon/agent.json")
    return wait_until(lambda: bool(pids("monitor-agent")), 10)


def stop_proc(name, sig="TERM", timeout=30):
    """Send a signal and wait for the process to exit; returns (seconds, exit code or None)."""
    start = now()
    wsl(f"pkill -{sig} -x {name} || true")
    gone = wait_until(lambda: not pids(name), timeout, 0.2)
    code = wsl(f"cat /root/mon/{name.replace('monitor-', '')}.exit 2>/dev/null || true")
    return (now() - start if gone is not None else None), (int(code) if code.strip().lstrip('-').isdigit() else None)


def send_ctrl_break(pid):
    """
    Ctrl+Break to a process that owns its own (hidden) console: attach to that console, broadcast the event, detach.
    Ctrl+Break rather than Ctrl+C: a console process can inherit "ignore Ctrl+C" from its parent (it does under most job runners),
    Ctrl+Break cannot be ignored that way. .NET reports it as SIGQUIT.
    """
    from ctypes import wintypes
    k = ctypes.WinDLL("kernel32", use_last_error=True)
    handler = ctypes.WINFUNCTYPE(wintypes.BOOL, wintypes.DWORD)(lambda event: True)  # swallow the event in this process
    k.FreeConsole()
    if not k.AttachConsole(pid):
        raise OSError(f"AttachConsole({pid}) failed: {ctypes.get_last_error()}")
    k.SetConsoleCtrlHandler(handler, True)
    k.GenerateConsoleCtrlEvent(1, 0)
    time.sleep(0.3)
    k.FreeConsole()
    k.SetConsoleCtrlHandler(handler, False)


class Probe:
    def __init__(self):
        self.proc = None
        self.log = os.path.join(WORK, "probe.log")

    def start(self):
        os.makedirs(WORK, exist_ok=True)
        handle = open(self.log, "a")
        # 自己的隐藏控制台：这样才能从外面给它发 Ctrl+Break
        flags = subprocess.CREATE_NO_WINDOW
        self.proc = subprocess.Popen([PROBE_EXE, "--config", os.path.join(WORK, "probe", "probe.json")], stdout=handle, stderr=subprocess.STDOUT, creationflags=flags)
        return self.proc.pid

    def alive(self):
        return self.proc is not None and self.proc.poll() is None

    def stop(self, mode="graceful", timeout=20):
        if not self.alive():
            return 0.0, self.proc.poll() if self.proc else None
        start = now()
        if mode == "graceful":
            send_ctrl_break(self.proc.pid)
        else:
            self.proc.kill()
        try:
            code = self.proc.wait(timeout)
        except subprocess.TimeoutExpired:
            self.proc.kill()
            return None, None
        return now() - start, code

    def suspend(self):
        """Freeze the process (its TCP connections stay open and go silent, like a hung machine)."""
        handle = ctypes.windll.kernel32.OpenProcess(0x0800, False, self.proc.pid)  # PROCESS_SUSPEND_RESUME
        ctypes.windll.ntdll.NtSuspendProcess(handle)
        ctypes.windll.kernel32.CloseHandle(handle)

    def resume(self):
        handle = ctypes.windll.kernel32.OpenProcess(0x0800, False, self.proc.pid)
        ctypes.windll.ntdll.NtResumeProcess(handle)
        ctypes.windll.kernel32.CloseHandle(handle)

    def working_set_mb(self):
        if not self.alive():
            return None
        out = subprocess.run(["powershell", "-NoProfile", "-Command", f"(Get-Process -Id {self.proc.pid}).WorkingSet64"], capture_output=True, text=True, creationflags=HIDDEN).stdout.strip()
        return int(out) / 1048576 if out else None

    def log_text(self):
        return open(self.log, encoding="utf-8", errors="replace").read() if os.path.exists(self.log) else ""


PROBE = Probe()
AGENT_ID = ""


# ------------------------------------------------------------------ environment setup

def setup(fresh=True):
    """Clean state, copy the artifacts, start backend/agent, create the probe identity. The probe is not started."""
    global TOKEN, AGENT_ID
    PROBE.stop("kill")
    wsl("pkill -9 -x monitor-agent; pkill -9 -x monitor-backend; tc qdisc del dev eth0 ingress 2>/dev/null; tc qdisc del dev eth0 root 2>/dev/null; tc qdisc del dev lo root 2>/dev/null; tc qdisc del dev lo ingress 2>/dev/null; true")
    if fresh:
        wsl(f"rm -rf /root/mon && mkdir -p /root/mon && cp {PUB}/backend/linux-x64/* {PUB}/agent/linux-x64/* {PUB}/fleet-enroll/linux-x64/* /root/mon/ && chmod +x /root/mon/monitor-* /root/mon/fleet-enroll")
        wsl("cat > /root/mon/start.sh <<'EOF'\n" + LAUNCHER + "EOF\nchmod +x /root/mon/start.sh")
        if os.path.isdir(WORK):
            subprocess.run(["cmd", "/c", "rmdir", "/s", "/q", WORK], capture_output=True, creationflags=HIDDEN)
        os.makedirs(os.path.join(WORK, "probe"), exist_ok=True)
    assert start_backend() is not None, "backend did not start"
    if fresh:
        req = urllib.request.Request(BASE + "/api/admin/auth/login", data=json.dumps({"username": "admin", "password": ADMIN_PASSWORD}).encode(), headers={"Content-Type": "application/json"}, method="POST")
        with OPENER.open(req, timeout=15) as resp:
            cookie = resp.headers["Set-Cookie"].split(";")[0]
            csrf = json.loads(resp.read())["csrf_token"]
        req = urllib.request.Request(BASE + "/api/admin/api-tokens", data=json.dumps({"name": "stab", "scope": "admin"}).encode(), headers={"Content-Type": "application/json", "Cookie": cookie, "X-CSRF-Token": csrf}, method="POST")
        TOKEN = json.loads(OPENER.open(req, timeout=15).read())["plaintext"]
        join = api("POST", "/api/admin/join-tokens", {"auto_approve": True, "max_uses": 5, "expires_in_hours": 1})["plaintext"]
        wsl(f"cd /root/mon && ./fleet-enroll --server http://127.0.0.1:{PORT} --join {join} --name wsl-agent --identity-dir /root/mon/id")
        cfg = {"fleet": {"server": f"http://127.0.0.1:{PORT}", "identity_dir": "/root/mon/id"}, "listen": {"bind": "0.0.0.0"}}
        wsl("cat > /root/mon/agent.json <<'EOF'\n" + json.dumps(cfg) + "\nEOF")
    assert start_agent() is not None
    assert wait_until(lambda: api("GET", "/api/admin/agents")["items"][0]["online"], 20) is not None, "agent did not come online"
    agent = api("GET", "/api/admin/agents")["items"][0]
    AGENT_ID = agent["id"]
    if fresh:
        api("PATCH", "/api/admin/agents/" + AGENT_ID, {"public_host": WSLIP}, "application/merge-patch+json")
        ident = api("POST", "/api/admin/probes", {"name": "home"})
        json.dump(ident, open(os.path.join(WORK, "probe", "probe.json"), "w"))
    PROBE.start()
    assert wait_until(agent_view_probe_connected, 30) is not None, "probe did not connect"


def agent_view():
    return api("GET", "/api/admin/agents/" + AGENT_ID)


def agent_view_probe_connected():
    return agent_view()["probe_connected"]


def agent_online():
    return agent_view()["online"]


def metrics(rng="2m", names="loss.total,loss.up,loss.down,rtt.p50,tcp.rtt.p50,tcp.rtt.max"):
    s = api("GET", f"/api/public/lines/{AGENT_ID}/series?range={rng}&step=1s&metrics={names}")
    return s["summary"]["metrics"], s["summary"]["samples"]


def gaps(minutes=3):
    """Buckets (10 s) in the last N minutes, after the first data, whose udp sample count is below half of the expected 100."""
    s = api("GET", f"/api/public/lines/{AGENT_ID}/series?range={minutes}m&step=10s&metrics=n.udp_echo,n.tcp_echo")
    udp = s["values"]["n.udp_echo"]
    first = next((i for i, v in enumerate(udp) if v is not None and v >= 50), len(udp))  # buckets before the first data are not gaps
    return [i for i, v in enumerate(udp[:-1]) if i > first and (v is None or v < 50)], len(udp)


def stored_chunks():
    return len(api("GET", f"/api/admin/raw/chunks?agent_id={AGENT_ID}&limit=1000")["items"])


def healthy():
    try:
        return agent_online() and agent_view_probe_connected()
    except Exception:
        return False


def ensure_healthy(timeout=60):
    if not backend_up():
        start_backend()
    if not pids("monitor-agent"):
        start_agent()
    if not PROBE.alive():
        PROBE.start()
    return wait_until(healthy, timeout)


# ------------------------------------------------------------------ scenarios

def scenario_init():
    print("== init: cold starts in every order, bad configuration")
    # 1. everything down, then start in the opposite order: probe -> agent -> backend (each must retry until its peer is up)
    PROBE.stop("kill")
    wsl("pkill -9 -x monitor-agent; pkill -9 -x monitor-backend; true")
    time.sleep(1)
    PROBE.start()
    time.sleep(3)
    start_agent()
    time.sleep(3)
    t0 = now()
    start_backend()
    took = wait_until(healthy, 90)
    check("probe -> agent -> backend start order converges", took is not None, f"{took:.1f}s after the backend came up" if took else "never became healthy")
    chunks_flow = wait_until(lambda: stored_chunks() > 0, 40)
    check("data flows after the cold start", chunks_flow is not None)

    # 2. backend first, then agent, then probe (the normal order) after a full stop
    PROBE.stop("kill")
    wsl("pkill -9 -x monitor-agent; pkill -9 -x monitor-backend; true")
    start_backend()
    start_agent()
    PROBE.start()
    took = wait_until(healthy, 60)
    check("backend -> agent -> probe start order converges", took is not None, f"{took:.1f}s" if took else "")

    # 3. the probe starts when its agent list is only a stale cache (agents.json wrong): bootstrap is still tried
    # 4. bad configuration: clear errors and a non-zero exit code, no crash dump
    bad = os.path.join(WORK, "bad.json")
    open(bad, "w").write("{ not json")
    r = subprocess.run([PROBE_EXE, "--config", bad], capture_output=True, text=True, timeout=20, creationflags=HIDDEN)
    check("probe: malformed config exits 1 with a readable error", r.returncode == 1 and "startup failed" in r.stderr + r.stdout, (r.stderr + r.stdout).strip()[:120])
    r = subprocess.run([PROBE_EXE, "--config", os.path.join(WORK, "missing.json")], capture_output=True, text=True, timeout=20, creationflags=HIDDEN)
    check("probe: missing config exits 1 with the file name", r.returncode == 1 and "missing.json" in r.stderr + r.stdout, (r.stderr + r.stdout).strip()[:120])
    out = wsl("cd /root/mon && echo '{ not json' > bad.json && ./monitor-agent --config bad.json 2>&1; echo exit=$?", check=False)
    check("agent: malformed config exits 1", "exit=1" in out and "startup failed" in out, out.strip()[-120:])
    out = wsl("cd /root/mon && printf '{\"fleet\":{\"server\":\"http://127.0.0.1:1\",\"identity_dir\":\"/nonexistent\"}}' > noid.json && ./monitor-agent --config noid.json 2>&1; echo exit=$?", check=False)
    check("agent: no identity says to run fleet-enroll first", "exit=1" in out and "fleet-enroll" in out, out.strip()[-140:])
    out = wsl(f"cd /root/mon && ./fleet-enroll --server http://127.0.0.1:{PORT} --join bogus --name x --identity-dir /tmp/enroll-x 2>&1; echo exit=$?", check=False)
    check("fleet-enroll: a bad join token fails clearly (non-zero exit)", "exit=0" not in out, out.strip()[-140:])
    out = wsl(f"cd /root/mon && ./fleet-enroll --server http://127.0.0.1:{PORT} --join bogus --name x --identity-dir /root/mon/id 2>&1; echo exit=$?", check=False)
    check("fleet-enroll: refuses to overwrite an existing identity", "exit=0" not in out and "already enrolled" in out, out.strip()[-140:])
    ensure_healthy()


def scenario_graceful():
    print("== graceful: SIGTERM / Ctrl+Break of each component, then restart")
    ensure_healthy()
    # probe (Ctrl+Break in its own console)
    secs, code = PROBE.stop("graceful")
    check("probe exits on Ctrl+Break within 5 s with code 0", secs is not None and secs < 5 and code == 0, f"{secs and round(secs, 2)}s code={code}")
    seen = wait_until(lambda: not agent_view_probe_connected(), 10)
    check("backend sees the probe disconnect", seen is not None, f"{seen and round(seen, 1)}s")
    PROBE.start()
    check("probe restarts and reconnects", wait_until(healthy, 30) is not None)

    # agent
    secs, code = stop_proc("monitor-agent", "TERM")
    log = wsl("tail -5 /root/mon/agent.log")
    check("agent exits on SIGTERM within 5 s with code 0", secs is not None and secs < 5 and code == 0, f"{secs and round(secs, 2)}s code={code}")
    check("agent logs a clean stop (no crash trace)", "stopping" in log and "Unhandled" not in log, log.splitlines()[-1][:100] if log else "")
    seen = wait_until(lambda: not agent_online(), 10)
    check("backend sees the agent go offline", seen is not None, f"{seen and round(seen, 1)}s")
    start_agent()
    check("agent restarts, reconnects to backend and probe", wait_until(healthy, 40) is not None)

    # backend
    secs, code = stop_proc("monitor-backend", "TERM", 30)
    log = wsl("tail -5 /root/mon/backend.log")
    check("backend exits on SIGTERM within 15 s with code 0", secs is not None and secs < 15 and code == 0, f"{secs and round(secs, 2)}s code={code}")
    check("backend log has no unhandled exception", "Unhandled" not in log and "Exception" not in log, log.replace(chr(10), ' | ')[-160:])
    time.sleep(5)
    start_backend()
    check("backend restarts, agent and probe converge again", wait_until(healthy, 60) is not None)
    ensure_healthy()


def scenario_crash():
    print("== crash: kill -9 / taskkill /F of each component, data durability")
    ensure_healthy()
    time.sleep(25)
    before = stored_chunks()

    # backend crash: the agent keeps its outbox; after restart nothing acknowledged is lost
    t = now()
    wsl("pkill -9 -x monitor-backend")
    time.sleep(25)  # agent outbox accumulates (2-3 chunk rounds)
    start_backend()
    back = wait_until(healthy, 60)
    check("backend kill -9: agent reconnects and everything converges", back is not None, f"{back and round(back, 1)}s after restart")
    time.sleep(20)
    after = stored_chunks()
    g, n = gaps(3)
    check("backend kill -9: chunks buffered by the agent are delivered after the restart (no gap)", not g, f"gaps in {n} buckets: {g}; chunks {before}->{after}")

    # agent crash
    wsl("pkill -9 -x monitor-agent")
    time.sleep(5)
    start_agent()
    check("agent kill -9: recovers", wait_until(healthy, 40) is not None)

    # probe crash
    PROBE.stop("kill")
    time.sleep(5)
    PROBE.start()
    check("probe kill: recovers", wait_until(healthy, 40) is not None)
    time.sleep(25)
    m, samples = metrics("30s")
    check("after all three crashes the line reports correct data (no phantom loss)", (m.get("loss.up") or 0) < 1 and (m.get("loss.down") or 0) < 1, f"loss.up={m.get('loss.up')} loss.down={m.get('loss.down')}")

    # crash in the middle of an on-demand test
    test = api("POST", f"/api/admin/lines/{AGENT_ID}/tests", {"plan": "hy2_ladder", "params": {"size": 1250}})
    time.sleep(12)
    PROBE.stop("kill")
    state = wait_until(lambda: api("GET", "/api/public/tests/" + test["id"])["status"] in ("failed", "aborted"), 30)
    final = api("GET", "/api/public/tests/" + test["id"])
    check("probe crash mid-test: the test ends (failed/aborted), it does not hang", state is not None, f"status={final['status']} error={final.get('error_code')}")
    PROBE.start()
    wait_until(healthy, 40)
    test2 = api("POST", f"/api/admin/lines/{AGENT_ID}/tests", {"plan": "hy2_ladder", "params": {"size": 1250}})
    done = wait_until(lambda: api("GET", "/api/public/tests/" + test2["id"])["status"] in ("succeeded", "failed", "aborted"), 90, 2)
    check("a new test runs to completion after the crash (the agent is not stuck busy)", done is not None and api("GET", "/api/public/tests/" + test2["id"])["status"] == "succeeded", api("GET", "/api/public/tests/" + test2["id"])["status"])
    ensure_healthy()


def netem(device, spec, direction="egress", ports=(7443, 7444)):
    """Impair only the data/control ports of the agent (so the rest of WSL is unaffected)."""
    clear_netem(device)
    if direction == "egress":
        wsl(f"tc qdisc add dev {device} root handle 1: prio && tc qdisc add dev {device} parent 1:3 handle 30: netem {spec}")
        for p in ports:
            wsl(f"tc filter add dev {device} protocol ip parent 1:0 prio 3 u32 match ip sport {p} 0xffff flowid 1:3")
    else:
        wsl(f"tc qdisc add dev {device} handle ffff: ingress")
        for p in ports:
            action = "action drop" if spec == "drop" else ""
            wsl(f"tc filter add dev {device} parent ffff: protocol ip u32 match ip dport {p} 0xffff {action}")


def clear_netem(device):
    wsl(f"tc qdisc del dev {device} root 2>/dev/null; tc qdisc del dev {device} ingress 2>/dev/null; true")


def scenario_probe_link():
    print("== probe<->agent link: flapping, long blackhole (half-open), reconnect storms")
    ensure_healthy()
    time.sleep(20)
    mem0 = (PROBE.working_set_mb(), rss_mb("monitor-agent"))

    # 1. flapping: 3 s blackholes every 10 s, 8 times
    for _ in range(8):
        netem("eth0", "drop", "ingress")
        time.sleep(3)
        clear_netem("eth0")
        time.sleep(7)
    check("flapping link: probe still connected afterwards", wait_until(healthy, 30) is not None)

    # 2. a 70 s blackhole: both ends must notice or survive, and recover once the path returns
    t = now()
    netem("eth0", "drop", "ingress")
    time.sleep(70)
    clear_netem("eth0")
    back = wait_until(healthy, 120)
    check("70 s blackhole: converges back to healthy", back is not None, f"{back and round(back, 1)}s after the path returned")
    time.sleep(35)
    m, _ = metrics("30s")
    check("after the blackhole the line is measured correctly again", (m.get("loss.total") or 0) < 2, f"loss.total={m.get('loss.total')}")

    # 3. reconnect storm: kill the agent 12 times in a row
    for _ in range(12):
        wsl("pkill -9 -x monitor-agent; true")
        time.sleep(0.5)
        start_agent()
        time.sleep(2)
    check("12 agent restarts in a row: converges", wait_until(healthy, 60) is not None)
    time.sleep(30)
    g, n = gaps(1)
    check("... and the data is flowing again", not g, f"gaps: {g}")

    # 4. restart storm of the probe
    for _ in range(8):
        PROBE.stop("kill")
        time.sleep(0.3)
        PROBE.start()
        time.sleep(2)
    check("8 probe restarts in a row: converges", wait_until(healthy, 60) is not None)
    time.sleep(40)
    mem1 = (PROBE.working_set_mb(), rss_mb("monitor-agent"))
    check("memory stays bounded after the storms", mem1[0] < mem0[0] + 15 and mem1[1] < mem0[1] + 15, f"probe {mem0[0]:.1f}->{mem1[0]:.1f} MB, agent {mem0[1]:.1f}->{mem1[1]:.1f} MB")
    ensure_healthy()


def scenario_backend_link():
    print("== agent<->backend link: outage buffering, replay, duplicates")
    ensure_healthy()
    time.sleep(30)
    # an outage on loopback (tc on lo: the agent<->backend link) shorter than the buffering capacity
    netem("lo", "drop", "ingress", ports=(PORT,))
    t = now()
    time.sleep(45)
    clear_netem("lo")
    check("45 s agent<->backend outage: agent stays up and reconnects", wait_until(agent_online, 90) is not None, f"{now() - t:.0f}s")
    time.sleep(35)
    g, n = gaps(4)
    check("data produced during the outage is replayed from the agent's outbox (no gap)", not g, f"gaps in {n} buckets: {g}")

    # duplicates: chunk ids are idempotent. The count of stored chunks grows by the expected 2 per 10 s, not more
    c0 = stored_chunks()
    time.sleep(30)
    c1 = stored_chunks()
    check("steady state: ~2 chunks / 10 s (udp + tcp), no duplicates", 4 <= c1 - c0 <= 8, f"{c1 - c0} chunks in 30 s")

    # the backend is stopped for a while (graceful): the agent keeps collecting, delivers after
    stop_proc("monitor-backend", "TERM", 30)
    time.sleep(40)
    start_backend()
    check("backend down 40 s then up: everything converges", wait_until(healthy, 90) is not None)
    time.sleep(35)
    g, n = gaps(4)
    check("... with no gap in the data", not g, f"gaps: {g}")
    ensure_healthy()


def scenario_silent():
    print("== silent death: a frozen process keeps its sockets open and says nothing (hung machine, lost power)")
    ensure_healthy()
    time.sleep(10)

    # a frozen probe: the agent must notice and tell the backend, instead of keeping a dead session forever
    PROBE.suspend()
    t = now()
    seen = wait_until(lambda: not agent_view_probe_connected(), 150, 1)
    check("frozen probe: the backend learns the probe is gone", seen is not None, f"{seen and round(seen)}s" if seen else "still shown as connected after 150 s")
    PROBE.resume()
    check("... and when the probe thaws it comes back", wait_until(healthy, 90) is not None)

    # a frozen agent: the probe must drop the session and keep retrying; the backend must mark the agent offline
    wsl("pkill -STOP -x monitor-agent")
    seen_off = wait_until(lambda: not agent_online(), 150, 1)
    check("frozen agent: the backend marks it offline", seen_off is not None, f"{seen_off and round(seen_off)}s" if seen_off else "still online after 150 s")
    wsl("pkill -CONT -x monitor-agent")
    check("... and when the agent thaws everything converges", wait_until(healthy, 90) is not None)

    # a frozen backend: the agent must notice (WebSocket ping timeout) and reconnect once the backend thaws
    wsl("pkill -STOP -x monitor-backend")
    time.sleep(70)
    wsl("pkill -CONT -x monitor-backend")
    check("frozen backend (70 s): converges after it thaws", wait_until(healthy, 90) is not None)
    time.sleep(30)
    g, n = gaps(3)
    check("... and the data produced while it was frozen is delivered", not g, f"gaps: {g}")
    ensure_healthy()


def scenario_soak():
    print("== soak: 8 minutes with random faults; memory, convergence and data continuity")
    ensure_healthy()
    time.sleep(20)
    mem0 = (PROBE.working_set_mb(), rss_mb("monitor-agent"), rss_mb("monitor-backend"))
    import random
    rnd = random.Random(7)
    end = now() + 8 * 60
    faults = 0
    while now() < end:
        fault = rnd.choice(["blackhole", "loss", "agent_kill", "probe_kill", "none", "none"])
        faults += fault != "none"
        if fault == "blackhole":
            netem("eth0", "drop", "ingress")
            time.sleep(rnd.uniform(1, 6))
            clear_netem("eth0")
        elif fault == "loss":
            netem("eth0", "delay 20ms 5ms loss 5%", "egress")
            time.sleep(rnd.uniform(5, 12))
            clear_netem("eth0")
        elif fault == "agent_kill":
            wsl("pkill -9 -x monitor-agent; true")
            time.sleep(1)
            start_agent()
        elif fault == "probe_kill":
            PROBE.stop("kill")
            time.sleep(0.5)
            PROBE.start()
        time.sleep(rnd.uniform(8, 20))
    clear_netem("eth0")
    check(f"after {faults} random faults everything converges", ensure_healthy(90) is not None)
    time.sleep(45)
    mem1 = (PROBE.working_set_mb(), rss_mb("monitor-agent"), rss_mb("monitor-backend"))
    check("memory bounded", mem1[0] < mem0[0] + 15 and mem1[1] < mem0[1] + 20 and mem1[2] < mem0[2] + 40, f"probe {mem0[0]:.0f}->{mem1[0]:.0f}, agent {mem0[1]:.0f}->{mem1[1]:.0f}, backend {mem0[2]:.0f}->{mem1[2]:.0f} MB")
    m, _ = metrics("30s")
    check("the final minute is measured correctly", (m.get("loss.up") or 0) < 1 and (m.get("loss.down") or 0) < 1, f"{m.get('loss.up')} {m.get('loss.down')}")


SCENARIOS = {
    "init": scenario_init,
    "graceful": scenario_graceful,
    "crash": scenario_crash,
    "probe_link": scenario_probe_link,
    "backend_link": scenario_backend_link,
    "silent": scenario_silent,
    "soak": scenario_soak,
}


def main():
    names = sys.argv[1:] or list(SCENARIOS)
    print(f"wsl ip {WSLIP}")
    setup(fresh=True)
    for name in names:
        try:
            SCENARIOS[name]()
        except Exception as ex:
            check(f"{name} ran to completion", False, repr(ex)[:300])
    PROBE.stop("kill")
    wsl("pkill -9 -x monitor-agent; pkill -9 -x monitor-backend; tc qdisc del dev eth0 root 2>/dev/null; tc qdisc del dev eth0 ingress 2>/dev/null; tc qdisc del dev lo ingress 2>/dev/null; true")
    failed = [r for r in RESULTS if not r[1]]
    print(f"\n{len(RESULTS) - len(failed)}/{len(RESULTS)} checks passed")
    for name, _, detail in failed:
        print(f"FAILED: {name} - {detail}")
    sys.exit(1 if failed else 0)


if __name__ == "__main__":
    main()