import type { FastifyBaseLogger } from "fastify";
import { devices, type Db, type DeviceRow } from "@parking/db";
import { isClockSyncable, isMonitorable, registry, type Device } from "@parking/devices";
import { deviceEvents, type DeviceStatusEvent } from "./device-events.js";
import { directionOf, relaysOf } from "./device-resolve.js";
import type { VisionClient } from "./vision-client.js";
import { siteTz } from "./subscription-window.js";

/** Synthetic device id for the vision service in the status footer (it's a service,
 *  not a device row, but shares the footer's traffic-light + WS plumbing). */
const VISION_STATUS_ID = "vision-service";

// Unified live DEVICE monitor — the source for the booth's device-status footer.
// Every enabled, configured device is probed on an interval, regardless of
// category: a printer via its rich readStatus() (paper/cover/cutter — reusing the
// same capability the PrinterMonitor uses), and a relay/reader/camera via the
// generic healthCheck() reachability probe every Device implements. The result is
// flattened to a common traffic-light (ready | degraded | offline) + a detail
// string, cached per device id, and emitted on the bus ONLY when it changes.
//
// This is device-agnostic (talks to the adapter interfaces, never a driver SDK)
// and read-only — polling a device never drives a relay or mutates the ledger.
// See wiki/concepts/device-status-monitoring.md, printer-status-monitoring.md.

const POLL_MS = Number(process.env.DEVICE_POLL_MS ?? 8000);

// Camera clock sync (Hikvision loses its clock on power cuts — reboots at the 1970
// epoch until a human logs into its web UI). The monitor re-syncs from the HOST
// clock (the site's offline time authority) at the offline→ready edge — exactly the
// power-restored moment — plus a daily backstop; drift under the threshold is left
// alone. See wiki/entities/lpr-camera.md (clock sync).
const CLOCK_SYNC_BACKSTOP_MS = 24 * 60 * 60 * 1000;
const CLOCK_MAX_DRIFT_SEC = 60;

/** The site's wall-clock now as ISO WITH utc offset (e.g. 2026-07-07T15:30:22+02:00)
 *  — what ISAPI's localTime wants. Derived via Intl for the site tz (no dep). */
export function localIsoWithOffset(tz: string, at = new Date()): string {
  const fmt = new Intl.DateTimeFormat("en-CA", {
    timeZone: tz,
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
    hour: "2-digit",
    minute: "2-digit",
    second: "2-digit",
    hourCycle: "h23",
  });
  const p = Object.fromEntries(fmt.formatToParts(at).map((x) => [x.type, x.value]));
  const wallAsUtcMs = Date.UTC(
    Number(p.year), Number(p.month) - 1, Number(p.day),
    Number(p.hour), Number(p.minute), Number(p.second),
  );
  const offMin = Math.round((wallAsUtcMs - at.getTime()) / 60_000);
  const sign = offMin < 0 ? "-" : "+";
  const abs = Math.abs(offMin);
  const hh = String(Math.floor(abs / 60)).padStart(2, "0");
  const mm = String(abs % 60).padStart(2, "0");
  return `${p.year}-${p.month}-${p.day}T${p.hour}:${p.minute}:${p.second}${sign}${hh}:${mm}`;
}

/**
 * The device's ROLE descriptor for the footer (never the vendor). Direction-style
 * tokens the client localises next to the category:
 *   - reader/camera → the direction inherited from its bound relay (entry/exit/both)
 *   - access        → entry/exit/both from its relays[]; "mixed" if it spans more
 *                     than one direction; null if it declares none yet
 *   - printer       → "lane" (entry-dispenser) | "booth" (booth-receipt) | "wash" (wash-desk)
 */
function roleKindOf(db: Db, row: DeviceRow): DeviceStatusEvent["roleKind"] {
  switch (row.category) {
    case "reader":
    case "camera": {
      const d = directionOf(db, row); // entry | exit | both
      return d;
    }
    case "access": {
      // Only barrier relays carry a role direction; alert (radarAlert) relays don't.
      const dirs = new Set(
        relaysOf(row)
          .map((r) => r.direction)
          .filter((d): d is "entry" | "exit" | "both" => d !== "radarAlert"),
      );
      if (dirs.size === 0) return null;
      if (dirs.size > 1) return "mixed";
      const only = [...dirs][0]; // entry | exit | both
      return only ?? null;
    }
    case "printer": {
      const role = (row.config as { role?: string }).role;
      if (role === "booth-receipt") return "booth";
      if (role === "entry-dispenser") return "lane";
      if (role === "wash-desk") return "wash";
      return null;
    }
    default:
      return null;
  }
}

export class DeviceMonitor {
  readonly #db: Db;
  readonly #log: FastifyBaseLogger;
  readonly #pollMs: number;
  /** Latest unified status per device id. */
  readonly #latest = new Map<string, DeviceStatusEvent>();
  #timer: ReturnType<typeof setInterval> | null = null;
  #ticking = false;

  /** Optional: the vision service client. When present + enabled, the monitor probes
   *  its /health each tick and shows it as a "vision" chip in the footer. */
  readonly #vision: VisionClient | null;

  constructor(db: Db, log: FastifyBaseLogger, pollMs = POLL_MS, vision: VisionClient | null = null) {
    this.#db = db;
    this.#log = log;
    this.#pollMs = pollMs;
    this.#vision = vision;
  }

  /** Begin polling. Idempotent. */
  start(): void {
    if (this.#timer) return;
    void this.#tick(); // immediate first pass so the footer fills without a wait
    this.#timer = setInterval(() => void this.#tick(), this.#pollMs);
    this.#timer.unref?.();
    this.#log.info(`device-monitor: polling every ${this.#pollMs}ms`);
  }

  stop(): void {
    if (this.#timer) {
      clearInterval(this.#timer);
      this.#timer = null;
    }
  }

  /** Current snapshot for the API / a freshly-connected WS client. */
  snapshot(): DeviceStatusEvent[] {
    return [...this.#latest.values()];
  }

  async #tick(): Promise<void> {
    if (this.#ticking) return; // never overlap polls
    this.#ticking = true;
    try {
      // Re-read the device set each tick so a newly-assigned/removed device is
      // picked up without a restart.
      const rows = await this.#db.select().from(devices).all();
      const enabled = rows.filter((r) => r.enabled);
      const present = new Set(enabled.map((r) => r.id));

      // The vision service is a pseudo-device — keep it in the present set when enabled
      // so the cleanup below doesn't evict it.
      if (this.#vision?.enabled) present.add(VISION_STATUS_ID);

      // Drop devices that are gone/disabled (so the footer doesn't show stale ones).
      for (const id of [...this.#latest.keys()]) {
        if (!present.has(id)) this.#latest.delete(id);
      }

      await Promise.all([...enabled.map((r) => this.#poll(r)), this.#pollVision()]);
    } catch (err) {
      this.#log.warn(`device-monitor tick failed: ${(err as Error).message}`);
    } finally {
      this.#ticking = false;
    }
  }

  async #poll(row: DeviceRow): Promise<void> {
    const cfg = (row.config ?? {}) as Record<string, unknown>;
    const base = {
      deviceId: row.id,
      driverId: row.driverId,
      category: row.category,
      roleKind: roleKindOf(this.#db, row),
    };

    let next: DeviceStatusEvent;
    let device: Device | null = null;
    const driver = registry.get(row.driverId);
    if (!driver) {
      // Configured against a driver that's no longer registered — surface it,
      // don't silently hide it.
      next = { ...base, state: "offline", detail: "driver not registered", checkedAt: new Date().toISOString() };
    } else {
      try {
        device = driver.create(cfg as never);
        // Printers expose richer paper/cover/cutter status; everything else uses
        // the generic reachability probe. Both flatten to the same traffic-light.
        if (isMonitorable(device)) {
          const s = await device.readStatus();
          next = { ...base, state: s.status, detail: s.detail, checkedAt: s.checkedAt };
        } else {
          const h = await device.healthCheck();
          next = { ...base, state: h.status, detail: h.detail, checkedAt: new Date().toISOString() };
        }
      } catch (err) {
        // A probe that throws (build error, timeout) reads as offline — never crash
        // the tick, and fail toward "there's a problem" rather than false-healthy.
        next = { ...base, state: "offline", detail: (err as Error).message, checkedAt: new Date().toISOString() };
      }
    }

    // Camera clock re-sync at the power-restored edge (prev offline/unknown →
    // ready) + a daily backstop. Stamped BEFORE the async attempt so a failing
    // camera is retried at backstop cadence, never every poll.
    if (row.category === "camera" && next.state === "ready" && device && isClockSyncable(device)) {
      const prev = this.#latest.get(row.id);
      const cameBack = !prev || prev.state === "offline";
      const last = this.#clockSyncedAt.get(row.id) ?? 0;
      if (cameBack || Date.now() - last > CLOCK_SYNC_BACKSTOP_MS) {
        this.#clockSyncedAt.set(row.id, Date.now());
        const cam = device;
        void (async () => {
          try {
            const r = await cam.syncClock(localIsoWithOffset(siteTz(this.#db)), CLOCK_MAX_DRIFT_SEC);
            if (r.synced) {
              // A large jump is the 1970 power-cut signature — warn (persisted) so
              // the reboot stays visible; a small correction is routine info.
              const msg = `device-monitor: camera ${row.id} clock synced (was ${r.driftSeconds ?? "unparseable"}s off)`;
              if (r.driftSeconds == null || r.driftSeconds > 3600) this.#log.warn(msg);
              else this.#log.info(msg);
            }
          } catch (err) {
            this.#log.warn(`device-monitor: camera ${row.id} clock sync failed: ${(err as Error).message}`);
          }
        })();
      }
    }

    this.#publish(row.id, next);
  }

  /** Probe the vision service /health and publish it as a "vision" footer chip. Skipped
   *  entirely when no client is wired or it's disabled (no chip then). */
  async #pollVision(): Promise<void> {
    if (!this.#vision?.enabled) return;
    const h = await this.#vision.health();
    const state: DeviceStatusEvent["state"] = h.ok && h.ready ? "ready" : h.ready ? "degraded" : "offline";
    this.#publish(VISION_STATUS_ID, {
      deviceId: VISION_STATUS_ID,
      driverId: "vision",
      category: "vision",
      roleKind: null,
      state,
      detail: h.ready ? h.recognizer : (h.detail ?? "not ready"),
      checkedAt: new Date().toISOString(),
    });
  }

  /** Per-camera timestamp of the last clock-sync ATTEMPT (backstop pacing). */
  readonly #clockSyncedAt = new Map<string, number>();

  /** Cache + emit a status, but only when it CHANGED (state or detail). */
  #publish(id: string, next: DeviceStatusEvent): void {
    const prev = this.#latest.get(id);
    this.#latest.set(id, next);
    if (!prev || prev.state !== next.state || prev.detail !== next.detail) {
      this.#log.info(
        `device-monitor: ${next.category}/${next.roleKind ?? "—"} ${id} -> ${next.state}${next.detail ? ` (${next.detail})` : ""}`,
      );
      deviceEvents.emitDeviceStatus(next);
    }
  }
}