#!/usr/bin/env python3
"""Claude Usage Tracker Daemon — Windows (Phase 2).

Reads the Claude OAuth token from the native-Windows credentials path and
polls the Anthropic API for rate-limit utilization data. BLE glue added in
later plans.
"""

import asyncio
import datetime
import json
import logging
import logging.handlers
import os
import re
import signal
import sys
import threading
import time
from pathlib import Path

import httpx
from bleak import BleakClient, BleakScanner
from bleak.exc import BleakError

DEVICE_NAME = "Clawdmeter"   # must match firmware ble.cpp DEVICE_NAME
# Optional direct-connect address. Once the device is bonded as a BLE HID
# keyboard, Windows keeps it connected, so it stops advertising and an active
# scan (find_device_by_name) never sees it. Setting CLAWDMETER_ADDRESS lets the
# daemon connect straight to the bonded device by address via WinRT.
DEVICE_ADDRESS = os.environ.get("CLAWDMETER_ADDRESS")
SERVICE_UUID = "4c41555a-4465-7669-6365-000000000001"
RX_CHAR_UUID = "4c41555a-4465-7669-6365-000000000002"
REQ_CHAR_UUID = "4c41555a-4465-7669-6365-000000000004"

POLL_INTERVAL = 60          # Anthropic rate-limit / usage poll cadence (seconds)
NOWPLAYING_INTERVAL = 3     # Windows media-session read cadence (seconds). The
                            # "music card" is refreshed ~20x faster than the API
                            # poll so a track / play-pause change reaches the watch
                            # within a few seconds instead of at the next 60s poll.
                            # Doubles as the inner-loop tick (was TICK=5) — the loop
                            # wakes this often to read media + detect a dropped link.
SCAN_TIMEOUT = 8.0
CONNECT_RETRIES = 3        # D-01: attempts before giving up on a device
CONNECT_RETRY_DELAY = 2.0  # D-01: seconds between failed connect attempts
ZOMBIE_BREAK_LIMIT = 1     # D-03: consecutive write failures before abandoning a half-open link
                           # N=1: breaks at T=60s, leaves ~60s headroom for reconnect+poll inside 120s SLA
                           # N=2 would bust the 120s budget before reconnect even begins
RECONNECT_BACKOFF_CAP = 8  # D-05: fast-reconnect cap (seconds); keeps stacked retries inside 120s SLA
                           # ~5–10s band per CONTEXT.md Claude's Discretion; 8 chosen as middle ground

API_URL = "https://api.anthropic.com/v1/messages"
API_HEADERS_TEMPLATE = {
    "anthropic-version": "2023-06-01",
    "anthropic-beta": "oauth-2025-04-20",
    "Content-Type": "application/json",
    "User-Agent": "claude-code/2.1.5",
}
API_BODY = {
    "model": "claude-haiku-4-5-20251001",
    "max_tokens": 1,
    "messages": [{"role": "user", "content": "hi"}],
}

# --- OAuth self-refresh -------------------------------------------------------
# In a managed (Agent SDK) environment `claude login` is unavailable, so once the
# stored access token expires nothing renews it and the 5h/7d rate-limit % goes
# dark permanently. The credentials file ships a refreshToken, so the daemon
# renews its own access token via the standard Claude Code OAuth refresh grant
# and writes the (rotated) tokens back. Endpoint + client_id verified empirically
# against a live refresh: HTTP 200, refresh_token rotates, expires_in=28800 (8h).
OAUTH_TOKEN_URL = "https://console.anthropic.com/v1/oauth/token"
OAUTH_CLIENT_ID = "9d1c250a-e61b-44d9-88ed-5944d1962f5e"
TOKEN_REFRESH_SKEW = 300  # refresh this many seconds BEFORE expiry (proactive)

# Anthropic list prices, USD per million tokens, keyed by a substring of the
# model id. Used to show the "equivalent API cost" of today's Claude Code usage
# — subscription users don't actually pay this; it's the ccusage-style flex.
# Verified against ccusage/LiteLLM: cost reproduces to 100%. The rates follow
# Anthropic's fixed structure (output 5x, cache-write 2x, cache-read 0.1x of the
# base input rate). Opus 4.x is $5/$25 — NOT the older $15/$75.
PRICING = {
    "opus":   {"in": 5.0,  "out": 25.0,  "cache_w": 10.0, "cache_r": 0.50},
    "sonnet": {"in": 3.0,  "out": 15.0,  "cache_w": 6.0,  "cache_r": 0.30},
    "haiku":  {"in": 0.75, "out": 3.75,  "cache_w": 1.50, "cache_r": 0.075},
}
_DEFAULT_PRICE = PRICING["opus"]


def _price_for(model: str) -> dict:
    m = (model or "").lower()
    for key, price in PRICING.items():
        if key in m:
            return price
    return _DEFAULT_PRICE


def compute_today_usage() -> dict:
    """Sum today's Claude Code token usage + equivalent API cost across all local
    project transcripts (~/.claude/projects/**/*.jsonl).

    Reads only files modified today (a session that touched today has mtime
    today), so the scan stays cheap even with a large transcript history. Each
    assistant line carries message.usage (input/output/cache token counts) and a
    UTC timestamp; per-line timestamps gate to today so a session spanning
    midnight is split correctly. Assistant turns are de-duplicated by
    (messageId, requestId): Claude Code copies history into new transcript files
    on compaction/resume, so the same API turn appears in several files and a
    naive sum over-counts (it inflated the total ~2.7x). Matches ccusage.
    Returns the compact BLE fields tk/tc/tn/to.
    """
    base = Path.home() / ".claude" / "projects"
    today = datetime.date.today()
    midnight = datetime.datetime.combine(today, datetime.time.min)
    total_tokens = 0
    output_tokens = 0
    cost = 0.0
    messages = 0
    seen = set()
    try:
        files = list(base.glob("**/*.jsonl"))
    except OSError:
        return {"tk": 0, "tc": 0, "tn": 0}
    for f in files:
        try:
            if datetime.datetime.fromtimestamp(f.stat().st_mtime) < midnight:
                continue
        except OSError:
            continue
        try:
            with open(f, encoding="utf-8") as fh:
                for line in fh:
                    line = line.strip()
                    if not line:
                        continue
                    try:
                        obj = json.loads(line)
                    except (json.JSONDecodeError, ValueError):
                        continue
                    msg = obj.get("message") if isinstance(obj, dict) else None
                    if not isinstance(msg, dict):
                        continue
                    usage = msg.get("usage")
                    if not isinstance(usage, dict):
                        continue
                    ts = obj.get("timestamp")
                    if not ts:
                        continue
                    try:
                        d = datetime.datetime.fromisoformat(
                            ts.replace("Z", "+00:00")).astimezone().date()
                    except ValueError:
                        continue
                    if d != today:
                        continue
                    # De-dup the same API turn copied across resumed/compacted files.
                    mid = obj.get("messageId") or msg.get("id")
                    rid = obj.get("requestId")
                    if mid is not None and rid is not None:
                        key = (mid, rid)
                        if key in seen:
                            continue
                        seen.add(key)
                    inp = usage.get("input_tokens", 0) or 0
                    out = usage.get("output_tokens", 0) or 0
                    cw = usage.get("cache_creation_input_tokens", 0) or 0
                    cr = usage.get("cache_read_input_tokens", 0) or 0
                    total_tokens += inp + out + cw + cr
                    output_tokens += out
                    messages += 1
                    p = _price_for(msg.get("model"))
                    cost += (inp * p["in"] + out * p["out"]
                             + cw * p["cache_w"] + cr * p["cache_r"]) / 1_000_000
        except OSError:
            continue
    return {"tk": int(total_tokens), "tc": int(round(cost * 100)),
            "tn": messages, "to": int(output_tokens)}


def _build_file_logger() -> logging.Logger | None:
    """Create a rotating file logger for field diagnostics, or None.

    Autostart launches the tray under pythonw.exe, which has no console — stdout
    is discarded (and is in fact None, making print() unsafe). A rotating file is
    then the ONLY trail when the daemon stalls in the field. Windows-only: on the
    Linux dev box / CI the console print() suffices, and gating to win32 keeps the
    pure-helper unit tests from writing stray log files.
    """
    if sys.platform != "win32":
        return None
    logger = logging.getLogger("clawdmeter.daemon")
    if logger.handlers:
        return logger  # idempotent across re-import (tray imports this module)
    base = Path(os.environ.get("LOCALAPPDATA", Path.home() / "AppData" / "Local"))
    path = base / "Clawdmeter" / "daemon.log"
    try:
        path.parent.mkdir(parents=True, exist_ok=True)
        handler = logging.handlers.RotatingFileHandler(
            path, maxBytes=512 * 1024, backupCount=3, encoding="utf-8"
        )
    except OSError:
        return None  # best-effort — logging setup must never stop the daemon
    handler.setFormatter(logging.Formatter("%(asctime)s %(message)s", "%Y-%m-%d %H:%M:%S"))
    logger.addHandler(handler)
    logger.setLevel(logging.INFO)
    logger.propagate = False
    return logger


_FILE_LOGGER = _build_file_logger()


def log(msg: str) -> None:
    line = f"[{time.strftime('%H:%M:%S')}] {msg}"
    # Under pythonw sys.stdout is None and print() would raise — guard it so a
    # missing console can never crash the daemon thread (the silent-freeze mode).
    try:
        print(line, flush=True)
    except (OSError, ValueError, AttributeError, RuntimeError):
        pass
    if _FILE_LOGGER is not None:
        _FILE_LOGGER.info(msg)


class AuthError(Exception):
    """Raised by poll_api on a genuine 401/403 — the token really is expired or
    invalid and the user must re-run `claude login`. Distinct from a None return,
    which means a TRANSIENT failure (network/DNS, timeout, rate-limit, 5xx) that
    must NOT be mislabeled as a token problem (SC#5: a boot-time `getaddrinfo
    failed` DNS blip wrongly fired the 'token expired' toast)."""


async def poll_api(token: str) -> dict | None:
    headers = dict(API_HEADERS_TEMPLATE)
    headers["Authorization"] = f"Bearer {token}"
    try:
        async with httpx.AsyncClient(timeout=20.0) as http:
            resp = await http.post(API_URL, headers=headers, json=API_BODY)
    except httpx.HTTPError as e:
        # Network/DNS/timeout — transient. Return None (no toast), retry next tick.
        log(f"API call failed: {e}")
        return None
    if resp.status_code in (401, 403):
        # Genuine auth rejection — the ONLY case that warrants the actionable
        # "run claude login" toast.
        log(f"API HTTP {resp.status_code}: {resp.text[:200]}")
        raise AuthError(resp.status_code)
    if resp.status_code >= 400:
        # Other 4xx/5xx (rate-limit, server error) — transient, not a token issue.
        log(f"API HTTP {resp.status_code}: {resp.text[:200]}")
        return None

    def hdr(name: str, default: str = "0") -> str:
        return resp.headers.get(name, default)

    now = time.time()

    def reset_minutes(reset_ts: str) -> int:
        try:
            r = float(reset_ts)
        except ValueError:
            return 0
        mins = (r - now) / 60.0
        return int(round(mins)) if mins > 0 else 0

    def pct(util: str) -> int:
        try:
            return int(round(float(util) * 100))
        except ValueError:
            return 0

    # Rate-limit utilization only. The local token usage and the "ok" flag are
    # merged by the caller (connect_and_run) so the Session screen keeps updating
    # even when this call fails (expired token / API down) — see decoupling there.
    return {
        "s": pct(hdr("anthropic-ratelimit-unified-5h-utilization")),
        "sr": reset_minutes(hdr("anthropic-ratelimit-unified-5h-reset")),
        "w": pct(hdr("anthropic-ratelimit-unified-7d-utilization")),
        "wr": reset_minutes(hdr("anthropic-ratelimit-unified-7d-reset")),
        "st": hdr("anthropic-ratelimit-unified-5h-status", "unknown"),
    }


async def scan_for_device():
    """Scan for DEVICE_NAME and return the BLEDevice, or None."""
    log(f"Scanning for '{DEVICE_NAME}' ({SCAN_TIMEOUT}s)...")
    device = await BleakScanner.find_device_by_name(DEVICE_NAME, timeout=SCAN_TIMEOUT)
    if device:
        log(f"Found: {device.address}")
        return device  # BLEDevice
    if DEVICE_ADDRESS:
        # Bonded device that's connected to Windows won't advertise — connect by address.
        log(f"Not advertising; connecting by bonded address {DEVICE_ADDRESS}")
        return DEVICE_ADDRESS  # address string — BleakClient accepts it on WinRT
    return device  # None


class Session:
    def __init__(self, client: BleakClient) -> None:
        self.client = client
        self.refresh_requested = asyncio.Event()

    def _on_refresh(self, _char, _data: bytearray) -> None:
        log("Refresh requested by device")
        self.refresh_requested.set()

    async def setup_refresh_subscription(self) -> None:
        # The refresh subscription is optional — the 60s poll loop works without it.
        # WinRT's start_notify() CCCD write can raise a raw OSError/WinError (not
        # wrapped as BleakError) when the peer GATT server is transiently unavailable,
        # e.g. a just-power-cycled ESP32 whose server is not yet ready (G-03-01, SC#3).
        # Degrade gracefully instead of crashing the daemon so it stays single-process
        # across a power-cycle reconnect (SC#4, no restart).
        try:
            await self.client.start_notify(REQ_CHAR_UUID, self._on_refresh)
        except (BleakError, ValueError, OSError) as e:
            log(f"Refresh subscription unavailable: {e}")

    async def write_payload(self, payload: dict) -> bool:
        # ensure_ascii=False keeps non-Latin titles as compact UTF-8 (~2 bytes/char)
        # instead of \uXXXX (6 bytes), which roughly thirds the size of a Cyrillic
        # "now playing" payload. ArduinoJson parses UTF-8 directly and LVGL renders
        # it, so this is a pure wire-size win with no firmware change.
        data = json.dumps(payload, separators=(",", ":"), ensure_ascii=False).encode()
        log(f"Sending: {data.decode()}")
        try:
            # response=True (Write Request, not Write Command). WinRT performs a
            # reliable long write when the payload exceeds the ATT MTU, so a long
            # media title no longer fails with E_INVALIDARG the way a larger-than-MTU
            # write-without-response does. The RX characteristic advertises WRITE as
            # well as WRITE_NR and NimBLE reassembles the long write (512 B buffer).
            # A successful write now also means the peer actually ACKed, which
            # sharpens the zombie-link detection below.
            await self.client.write_gatt_char(RX_CHAR_UUID, data, response=True)
            return True
        except (BleakError, OSError) as e:
            # WinRT can raise a raw OSError/WinError (NOT wrapped as BleakError)
            # when the peer GATT server goes transiently unavailable mid-write —
            # the same failure class setup_refresh_subscription() guards against.
            # Returning False trips the zombie-link break -> clean reconnect,
            # rather than an uncaught exception killing the daemon thread (the
            # silent-freeze failure mode, SC#2 field report).
            log(f"Write failed: {e}")
            return False


def _extract_access_token(blob: str) -> str | None:
    """Pull the accessToken out of a credentials blob.

    Claude Code stores credentials as a JSON object; the blob may also be
    nested ({"claudeAiOauth": {"accessToken": "..."}}). Fall back to a
    regex match so unexpected shapes still work, and finally treat the
    blob as a raw token if nothing else matches.
    """
    blob = blob.strip()
    if not blob:
        return None
    try:
        data = json.loads(blob)
    except json.JSONDecodeError:
        data = None
    if isinstance(data, dict):
        # direct: {"accessToken": "..."}
        tok = data.get("accessToken")
        if isinstance(tok, str) and tok.strip():
            return tok
        # nested: {"claudeAiOauth": {"accessToken": "..."}}
        for v in data.values():
            if isinstance(v, dict):
                tok = v.get("accessToken")
                if isinstance(tok, str) and tok.strip():
                    return tok
    m = re.search(r'"accessToken"\s*:\s*"([^"]+)"', blob)
    if m:
        return m.group(1)
    # Raw token (no JSON wrapper) — must look plausible (sk-ant-... etc.)
    if re.fullmatch(r"[A-Za-z0-9_\-.~+/=]{20,}", blob):
        return blob
    return None


def _windows_credential_candidates() -> list[Path]:
    """Return the ordered list of credential file paths to probe (first hit wins).

    Priority:
    1. CLAUDE_CREDENTIALS_PATH env override (D-03, project-specific)
    2. CLAUDE_CONFIG_DIR env override (official Claude override)
    3. D-02 candidate list: home/.claude, LOCALAPPDATA/Claude, APPDATA/Claude
    """
    # Priority 1: project-specific env override (D-03)
    if override := os.environ.get("CLAUDE_CREDENTIALS_PATH"):
        return [Path(override)]
    # Priority 2: official CLAUDE_CONFIG_DIR env override
    if config_dir := os.environ.get("CLAUDE_CONFIG_DIR"):
        return [Path(config_dir) / ".credentials.json"]
    # Priority 3: D-02 candidate list — first hit wins
    home = Path.home()
    local_appdata = Path(os.environ.get("LOCALAPPDATA", home / "AppData" / "Local"))
    appdata = Path(os.environ.get("APPDATA", home / "AppData" / "Roaming"))
    return [
        home / ".claude" / ".credentials.json",          # primary (confirmed by docs)
        local_appdata / "Claude" / ".credentials.json",  # fallback 2
        appdata / "Claude" / ".credentials.json",        # fallback 3
    ]


def read_token() -> str | None:
    """Read the Claude OAuth access token from the first available credential file."""
    for path in _windows_credential_candidates():
        try:
            return _extract_access_token(path.read_text(encoding="utf-8"))
        except OSError:
            continue
    return None


def _read_expiry() -> str:
    """Return human-readable expiry from the first-hit credentials file.

    Reads claudeAiOauth.expiresAt (epoch milliseconds — JS convention).
    Divides by 1000 before passing to fromtimestamp (Python expects seconds).
    Returns 'expiry unknown' on any parse failure.
    """
    for path in _windows_credential_candidates():
        try:
            raw = path.read_text(encoding="utf-8")
        except OSError:
            continue
        try:
            data = json.loads(raw)
            oauth = data.get("claudeAiOauth", {})
            expires_ms = oauth.get("expiresAt")
            if expires_ms is None:
                return "expiry unknown"
            # CRITICAL: expiresAt is JS-convention epoch milliseconds; divide by 1000
            # before fromtimestamp (Python expects seconds). Raw value -> year ~57000.
            dt = datetime.datetime.fromtimestamp(
                expires_ms / 1000, tz=datetime.timezone.utc
            )
            return dt.strftime("%Y-%m-%d %H:%M UTC")
        except (TypeError, ValueError, OSError, AttributeError, json.JSONDecodeError):
            return "expiry unknown"
    return "expiry unknown"


def _read_credentials() -> tuple[Path, dict] | None:
    """Return (path, parsed-JSON dict) for the first readable credentials file.

    Same probe order as read_token() so the file we refresh is the file we read
    the token from.
    """
    for path in _windows_credential_candidates():
        try:
            return path, json.loads(path.read_text(encoding="utf-8"))
        except (OSError, json.JSONDecodeError):
            continue
    return None


def _write_credentials_atomic(path: Path, data: dict) -> None:
    """Write credentials JSON via temp-file + os.replace (atomic same-volume).

    Avoids leaving a half-written .credentials.json if the process dies mid-write
    — a corrupt credentials file would break BOTH the daemon and Claude Code.
    """
    tmp = path.with_name(path.name + ".tmp")
    tmp.write_text(json.dumps(data, indent=2), encoding="utf-8")
    os.replace(tmp, path)


def _token_expired(oauth: dict, skew: int = TOKEN_REFRESH_SKEW) -> bool:
    """True if the access token is within `skew` seconds of expiry (or past it).

    Unknown/absent expiresAt -> False: don't refresh blindly on every cycle; the
    API-401 path (force=True) drives a refresh if the token is actually rejected.
    """
    exp = oauth.get("expiresAt")
    if not isinstance(exp, (int, float)):
        return False
    return (exp / 1000.0) <= (time.time() + skew)


async def refresh_token_if_needed(force: bool = False) -> bool:
    """Renew the OAuth access token from the stored refresh token when it is
    expired/near-expiry (or force=True), writing the rotated tokens back atomically.

    Returns True iff a refresh succeeded and credentials were updated. Never
    raises — every failure is logged and returned as False so a refresh hiccup
    can never take down the poll loop.
    """
    rc = _read_credentials()
    if rc is None:
        return False
    path, data = rc
    oauth = data.get("claudeAiOauth")
    if not isinstance(oauth, dict):
        return False
    refresh = oauth.get("refreshToken")
    if not isinstance(refresh, str) or not refresh.strip():
        return False
    if not force and not _token_expired(oauth):
        return False

    body = {
        "grant_type": "refresh_token",
        "refresh_token": refresh,
        "client_id": OAUTH_CLIENT_ID,
    }
    try:
        async with httpx.AsyncClient(timeout=20.0) as http:
            resp = await http.post(
                OAUTH_TOKEN_URL, json=body,
                headers={"Content-Type": "application/json"},
            )
    except httpx.HTTPError as e:
        log(f"Token refresh network error: {e}")
        return False
    if resp.status_code != 200:
        # Error bodies are {"error": ...} — no secrets; safe to log a snippet.
        log(f"Token refresh HTTP {resp.status_code}: {resp.text[:200]}")
        return False
    try:
        tok = resp.json()
    except ValueError:
        log("Token refresh: non-JSON response")
        return False

    new_access = tok.get("access_token")
    if not new_access:
        log("Token refresh: response had no access_token")
        return False
    oauth["accessToken"] = new_access
    if tok.get("refresh_token"):
        oauth["refreshToken"] = tok["refresh_token"]   # refresh tokens rotate
    if tok.get("expires_in"):
        oauth["expiresAt"] = int((time.time() + float(tok["expires_in"])) * 1000)
    try:
        _write_credentials_atomic(path, data)
    except OSError as e:
        log(f"Token refresh: could not write credentials: {e}")
        return False
    log(f"OAuth token refreshed; new expiry {_read_expiry()}")
    return True


# --- Now Playing (Phase 5) ----------------------------------------------------
# Best-effort read of the Windows "now playing" media session (System Media
# Transport Controls) so the watch can show the current track. Pure local WinRT —
# no network, no token — so it works even when the rate-limit data is unavailable.
# Any failure degrades to {"np": 0} (nothing playing) and never disturbs the loop.
NP_MAX_LEN = 60  # truncate title/artist so the BLE payload stays comfortably small


async def read_now_playing() -> dict:
    """Return compact now-playing fields for the BLE payload::

        {"np": 0|1|2, "nt": <title>, "na": <artist>}

    np: 0 = nothing playing, 1 = playing, 2 = paused. nt/na are omitted when
    empty. Never raises — the daemon must keep polling even if WinRT hiccups
    (and the winrt media package may simply be absent on some installs).
    """
    try:
        from winrt.windows.media.control import (
            GlobalSystemMediaTransportControlsSessionManager as MediaManager,
            GlobalSystemMediaTransportControlsSessionPlaybackStatus as PB,
        )
    except ImportError:
        return {"np": 0}

    try:
        mgr = await MediaManager.request_async()
        sess = mgr.get_current_session()
        if sess is None:
            return {"np": 0}
        status = sess.get_playback_info().playback_status
        if status == PB.PLAYING:
            np = 1
        elif status == PB.PAUSED:
            np = 2
        else:
            np = 0  # stopped / closed / changing -> treat as nothing playing
        out: dict = {"np": np}
        if np:
            info = await sess.try_get_media_properties_async()
            title = (info.title or "").strip()
            artist = (info.artist or "").strip()
            if title:
                out["nt"] = title[:NP_MAX_LEN]
            if artist:
                out["na"] = artist[:NP_MAX_LEN]
        return out
    except Exception as e:  # WinRT can surface assorted OSError/RuntimeError types
        log(f"Now-playing read failed: {e!r}")
        return {"np": 0}


async def _wait_first(*events: asyncio.Event, timeout: float) -> None:
    """Return when any of `events` is set, or after `timeout` seconds.

    Lets the poll loop's tick wait wake immediately on a stop signal (clean,
    responsive Quit) without losing the refresh-request wakeup — instead of
    waiting only on refresh_requested and re-checking stop_event up to a tick
    later. Cancels and drains the loser tasks so they don't warn.
    """
    tasks = [asyncio.ensure_future(e.wait()) for e in events]
    try:
        await asyncio.wait(tasks, timeout=timeout, return_when=asyncio.FIRST_COMPLETED)
    finally:
        for t in tasks:
            t.cancel()
        await asyncio.gather(*tasks, return_exceptions=True)


async def connect_and_run(device, stop_event: asyncio.Event, tray_state=None) -> bool:
    """Connect to device and poll until disconnected or stopped.

    Returns True if at least one successful write occurred.
    """
    addr = device if isinstance(device, str) else device.address
    log(f"Connecting to {addr}...")
    # D-01: retry wrapper — defeats WinRT post-wake failure modes
    # (Could not get GATT services: Unreachable, stale is_connected).
    # Rebuild a fresh BleakClient each attempt (locked D-05 recipe).
    client = None
    for attempt in range(CONNECT_RETRIES):
        # D-05: pass BLEDevice (not address string), address_type="random" (NimBLE
        # static-random), use_cached_services=False (DIY firmware — WinRT GATT cache
        # may be stale after firmware reflash).
        client = BleakClient(
            device,
            address_type="random",
            use_cached_services=False,
        )
        try:
            await client.connect()
        except (BleakError, asyncio.TimeoutError) as e:
            log(f"Connection attempt {attempt + 1}/{CONNECT_RETRIES} failed: {e}")
            try:
                await client.disconnect()
            except BleakError:
                pass
            if attempt < CONNECT_RETRIES - 1:
                await asyncio.sleep(CONNECT_RETRY_DELAY)
            continue

        if not client.is_connected:
            log(f"Connection attempt {attempt + 1}/{CONNECT_RETRIES} failed (not connected)")
            try:
                await client.disconnect()
            except BleakError:
                pass
            if attempt < CONNECT_RETRIES - 1:
                await asyncio.sleep(CONNECT_RETRY_DELAY)
            continue

        # Connected successfully
        break
    else:
        log(f"Connection failed after {CONNECT_RETRIES} attempts")
        return False

    log("Connected")
    session = Session(client)
    await session.setup_refresh_subscription()

    # Two cadences share one connection: the Anthropic usage / rate-limit poll runs
    # every POLL_INTERVAL (60s) while the Windows media session is read every
    # NOWPLAYING_INTERVAL (3s). The last usage payload is cached and merged into
    # each now-playing write, so the firmware always gets one complete JSON object
    # (its parser defaults any missing field to 0 — a partial write would blank the
    # usage screens) and a track change shows within a few seconds, not 60.
    last_claude_poll = 0.0    # 0 => poll Anthropic immediately on first connect
    cached: dict = {}         # last usage + rate-limit fields, re-sent every tick
    last_np_sent = None       # last now-playing fields actually written (change gate)
    used_successfully = False
    consecutive_failures = 0  # D-03: zombie-link break counter
    try:
        while client.is_connected and not stop_event.is_set():
            now = time.time()
            claude_due = (session.refresh_requested.is_set()
                          or (now - last_claude_poll) >= POLL_INTERVAL)
            auth_problem = False

            if claude_due:
                session.refresh_requested.clear()

                # Local token usage (Session screen) needs no network — compute it
                # every cycle so the watch keeps updating even with no/expired token.
                fresh = compute_today_usage()

                # Rate-limit utilization is best-effort. A genuine 401/403 flags the
                # token; a transient failure (network/DNS/5xx) leaves the tray state
                # alone (SC#5: a DNS blip must not read as "token expired").
                rl = None

                # Self-refresh the OAuth token before using it. In a managed
                # (Agent SDK) environment `claude login` is unavailable, so the
                # daemon renews its own access token from the refresh token —
                # otherwise the rate-limit % goes dark forever once it expires.
                try:
                    await refresh_token_if_needed()
                except Exception as e:  # belt-and-braces: never crash the loop
                    log(f"Token refresh skipped: {e!r}")

                token = read_token()  # D-09: fresh each cycle (post-refresh)
                if not token:
                    auth_problem = True
                    log("No token; sending local usage only")
                else:
                    try:
                        rl = await poll_api(token)
                    except AuthError:
                        # Rejected despite the proactive refresh (e.g. expiresAt
                        # was stale/missing so we skipped it). Force one refresh
                        # and retry the poll once before flagging the token bad.
                        try:
                            forced = await refresh_token_if_needed(force=True)
                        except Exception as e:
                            log(f"Forced token refresh failed: {e!r}")
                            forced = False
                        if forced and (token := read_token()):
                            try:
                                rl = await poll_api(token)
                            except AuthError:
                                auth_problem = True
                        else:
                            auth_problem = True

                if rl is not None:
                    fresh.update(rl)
                    fresh["ok"] = True     # rate-limit data is fresh
                else:
                    fresh["ok"] = False    # rate-limit unknown -> watch usage view goes idle

                cached = fresh
                last_claude_poll = now

            # Now Playing (Phase 5) — best-effort Windows media session, read every
            # tick (fast cadence). Local only, so it works regardless of "ok" above.
            try:
                np = await read_now_playing()
            except Exception as e:  # never let media reading break the poll loop
                log(f"Now-playing skipped: {e!r}")
                np = {"np": 0}

            # Write when the usage data was just refreshed (this is also the ~60s
            # heartbeat) or when the track / playback state changed since the last
            # write — skip otherwise so the link, and the field log, stay quiet
            # between changes instead of repeating an identical payload every 3s.
            if claude_due or np != last_np_sent:
                payload = dict(cached)
                payload.update(np)
                if await session.write_payload(payload):
                    used_successfully = True
                    consecutive_failures = 0  # D-03: reset on success
                    last_np_sent = np
                    # The tray reflects the Anthropic data freshness, so only touch
                    # it on a usage poll — never on a now-playing-only write.
                    if claude_due:
                        if cached.get("ok"):
                            if tray_state:
                                tray_state.set_connected(time.time())
                        elif auth_problem:
                            if tray_state:
                                tray_state.set_error("token expired — run claude login")
                        # transient rate-limit failure: leave tray state unchanged
                else:
                    consecutive_failures += 1
                    if consecutive_failures >= ZOMBIE_BREAK_LIMIT:
                        log(
                            f"Zombie link detected ({consecutive_failures} consecutive"
                            f" write failures); abandoning connection"
                        )
                        break

            # Wake on a refresh request OR a stop, whichever comes first, but no
            # later than NOWPLAYING_INTERVAL so the media session is re-read on time.
            # Waking promptly on stop_event is what lets the finally below run
            # client.disconnect() before the process exits, so the peer gets a clean
            # GATT disconnect (returns to its waiting screen) instead of being left
            # frozen on stale data after Quit (SC#3 graceful shutdown).
            await _wait_first(session.refresh_requested, stop_event,
                              timeout=NOWPLAYING_INTERVAL)
    finally:
        # Clean GATT disconnect on the way out — this is what tells the peripheral
        # the link is gone. WinRT can surface a raw OSError (not BleakError) here,
        # so swallow both; the link tears down regardless once we exit.
        try:
            await client.disconnect()
        except (BleakError, OSError):
            pass

    log("Device disconnected" if not stop_event.is_set() else "Stopping")
    return used_successfully


def _next_backoff(current: int, cap: int) -> int:
    """D-05: double current backoff value, clamped to cap.

    Pure helper — unit-testable without driving the main loop.
    Used by both slow-search (cap=60) and fast-reconnect (cap=RECONNECT_BACKOFF_CAP) regimes.
    """
    return min(current * 2, cap)


async def main(tray_state=None) -> None:
    stop_event = asyncio.Event()
    loop = asyncio.get_running_loop()

    # Populate the shared state object so the tray can route Quit through
    # loop.call_soon_threadsafe (RESEARCH Pitfall 2).  Additive — the existing
    # stop_event = asyncio.Event() line above is unchanged.
    if tray_state is not None:
        tray_state.loop = loop
        tray_state.stop_event = stop_event

    def _stop(*_args: object) -> None:
        log("Daemon stopping")
        stop_event.set()

    # OS signal handlers can only be installed from the main thread, and
    # loop.add_signal_handler is unsupported on Windows. When running under the
    # tray (04-03) the loop lives in a background thread and the tray owns clean
    # shutdown via stop_event (loop.call_soon_threadsafe), so skip silently there.
    if threading.current_thread() is threading.main_thread():
        for sig in (signal.SIGINT, signal.SIGTERM):
            try:
                loop.add_signal_handler(sig, _stop)
            except NotImplementedError:
                # Windows: add_signal_handler not supported; fall back to signal.signal
                try:
                    signal.signal(sig, _stop)
                except ValueError:
                    # Not the main thread of the main interpreter — tray owns shutdown.
                    pass

    log("=== Claude Usage Tracker Daemon (BLE, Windows) ===")
    log(f"Poll interval: {POLL_INTERVAL}s")

    # D-05: two distinct backoff regimes — slow-search (device absent) vs fast-reconnect (link dropped)
    search_backoff = 1     # caps at 60s — gentle, for a device that is genuinely absent/off
    reconnect_backoff = 1  # caps at RECONNECT_BACKOFF_CAP — fast, to clear the 120s SLA after a drop
    while not stop_event.is_set():
        try:
            device = await scan_for_device()
            if not device:
                # Slow-search regime: device was not found by scan — back off gently
                if tray_state:
                    tray_state.set_scanning()
                log(f"Device not found, retrying in {search_backoff}s...")
                try:
                    await asyncio.wait_for(stop_event.wait(), timeout=search_backoff)
                except asyncio.TimeoutError:
                    pass
                search_backoff = _next_backoff(search_backoff, 60)
                continue

            ok = await connect_and_run(device, stop_event, tray_state)
            if not ok:
                # Fast-reconnect regime: had/attempted a link that dropped — retry quickly
                if tray_state:
                    tray_state.set_scanning()
                log(f"Connection lost, reconnecting in {reconnect_backoff}s...")
                try:
                    await asyncio.wait_for(stop_event.wait(), timeout=reconnect_backoff)
                except asyncio.TimeoutError:
                    pass
                reconnect_backoff = _next_backoff(reconnect_backoff, RECONNECT_BACKOFF_CAP)
            else:
                # Successful session — reset reconnect counter to floor; search_backoff also reset
                reconnect_backoff = 1
                search_backoff = 1
        except asyncio.CancelledError:
            raise
        except Exception as e:
            # The whole BLE adapter can disappear (USB dongle unplugged) — bleak/
            # WinRT then raises from the scan or the connect. Never let that kill
            # the loop: log, show Scanning, back off, and keep retrying so
            # replugging the adapter recovers on its own, no manual restart
            # (field SC: pulled the dongle -> daemon crashed and stayed down).
            if tray_state:
                tray_state.set_scanning()
            log(f"BLE error ({type(e).__name__}: {e}); retrying in {search_backoff}s...")
            try:
                await asyncio.wait_for(stop_event.wait(), timeout=search_backoff)
            except asyncio.TimeoutError:
                pass
            search_backoff = _next_backoff(search_backoff, 60)


if __name__ == "__main__":
    if sys.platform != "win32":
        print(
            "Warning: running under Linux/WSL — WinRT BLE will not be available.",
            file=sys.stderr,
        )
    try:
        asyncio.run(main())
    except KeyboardInterrupt:
        sys.exit(0)