import { eq, devices, type Db, type DeviceRow } from "@parking/db";
import type { FastifyBaseLogger } from "fastify";
import { hasAuxOutput, registry, type AuxOutputDevice } from "@parking/devices";
import { deviceEvents, type DeviceInputEvent, type LaneStatusEvent } from "./device-events.js";
import { alertRelaysOf, relayForPresence, type RelaySpec } from "./device-resolve.js";

// Alert (radarAlert) relays — non-barrier indicator lamps, e.g. the entry button's 12 V
// light. Each lamp is a `relays[]` row with event `radarAlert`, driven by ITS trigger
// input vs. the camera "car in zone" signal (the advisory lane-status). A disagreement
// indicator:
//   trigger active + lane busy (camera confirms a car) → SOLID on
//   trigger active + lane free  (radar sees something, no car) → BLINK (~1 Hz)
//   otherwise → OFF
// The lamp is a NON-barrier aux output (setAux latch), so holding/blinking it is fine
// — barrier-not-a-door applies only to barriers, which still only pulseOpen. The lamp
// FAILS OFF: any error / shutdown leaves it off, so a dead lamp is "no hint", never a
// misleading solid "go". A controller may have several alert relays (each its own row +
// trigger input), keyed independently. See wiki/concepts/button-light-indicator.md.

type LightState = "off" | "solid" | "blink";

const DEFAULT_BLINK_MS = 500;

/** Per-lamp live state for the alert rule (one per radarAlert relay). */
interface LampState {
  /** The controller this lamp lives on (its deviceId) — for resolving the aux adapter. */
  readonly controllerId: string;
  /** Alert relay row (relay #, triggerInput, blink ms). Mutable: #reconcile updates it in
   *  place when the admin changes the alert config without a restart. */
  spec: RelaySpec;
  /** Is the lamp's trigger input (the radar) currently active? */
  present: boolean;
  /** The high-level state we're rendering (to avoid restarting a running blink). */
  rendered: LightState | null;
  /** Active blink timer, if blinking. */
  blink: ReturnType<typeof setInterval> | null;
  /** Blink phase (true = currently on). */
  blinkOn: boolean;
  /** The output we WANT the relay to be in. The serialized worker drives the device
   *  toward this. The blink timer only flips this flag — it never sends directly. */
  desiredOn: boolean;
  /** The output we last CONFIRMED on the device (after a successful send). null = unknown. */
  confirmedOn: boolean | null;
  /** True while a send is in flight for this lamp — serializes UDP so on/off can't
   *  overlap or reorder (UDP is unordered; concurrent toggles left the relay stuck). */
  sending: boolean;
}

/** Resolves a controller's live aux-output adapter. The default goes through the
 *  driver registry; tests inject a spy. Returns null when the controller has no
 *  aux-output capability (or won't build). */
export type AuxResolver = (controllerId: string) => AuxOutputDevice | null;

export class ButtonLightController {
  readonly #db: Db;
  readonly #logger: FastifyBaseLogger;
  readonly #resolveAux: AuxResolver;
  /** Per-lamp state, keyed by `${controllerId}:${relay}` (a controller may have several). */
  readonly #lamps = new Map<string, LampState>();
  /** Latest lane status — a camera-confirmed car in the entry / exit zone. A lamp locks
   *  SOLID off its OWN lane's camera (`spec.lockLane`), so an exit radar's lamp tracks the
   *  exit camera, not the entry one. */
  #entryBusy = false;
  #exitBusy = false;
  /** Controllers we've already warned lack the aux-output capability (warn once). */
  readonly #warned = new Set<string>();
  #unsubInput: (() => void) | null = null;
  #unsubLane: (() => void) | null = null;

  constructor(db: Db, logger: FastifyBaseLogger, resolveAux?: AuxResolver) {
    this.#db = db;
    this.#logger = logger;
    this.#resolveAux = resolveAux ?? ((id) => this.#auxFromRegistry(id));
  }

  /** Subscribe to radar input edges + lane status, and initialise every lamp OFF. */
  start(): void {
    this.#reconcile();
    // All lamps start OFF (known-safe baseline) regardless of prior device state.
    for (const lamp of this.#lamps.values()) this.#apply(lamp);

    this.#unsubInput = deviceEvents.onInput((e) => this.#onInput(e));
    this.#unsubLane = deviceEvents.onLaneStatus((s) => this.#onLane(s));
  }

  /** Reconcile the lamp map with the CURRENT device config (the booth can add/change a
   *  button light without a server restart). Mirrors DeviceMonitor, which re-reads the
   *  device set each tick. Adds lamps for newly-configured controllers, updates the spec
   *  (relay #, blink ms) in place — preserving live `present`/blink state — and drops
   *  lamps whose controller lost its buttonLight or was disabled. Called at start() and
   *  before handling each event, so a just-saved lamp takes effect immediately. */
  #reconcile(): void {
    const rows = this.#db.select().from(devices).where(eq(devices.category, "access")).all();
    const seen = new Set<string>();
    for (const row of rows) {
      if (!row.enabled) continue;
      for (const spec of alertRelaysOf(row)) {
        const key = lampKey(row.id, spec.relay);
        seen.add(key);
        const existing = this.#lamps.get(key);
        if (existing) {
          existing.spec = spec; // pick up a changed trigger input / blink cadence
        } else {
          this.#lamps.set(key, {
            controllerId: row.id,
            spec,
            present: false,
            rendered: null,
            blink: null,
            blinkOn: false,
            desiredOn: false,
            confirmedOn: null,
            sending: false,
          });
        }
      }
    }
    // Drop lamps whose controller no longer declares one (or was disabled/removed).
    for (const [key, lamp] of this.#lamps) {
      if (seen.has(key)) continue;
      if (lamp.blink) {
        clearInterval(lamp.blink);
        lamp.blink = null;
      }
      this.#finalOff(lamp); // best-effort fail-OFF before forgetting it
      this.#lamps.delete(key);
    }
  }

  /** A radar (presence) edge updates that controller's `present` flag. We resolve the
   *  edge the SAME way the entry flow does (relayForPresence on an entry/both relay),
   *  so the lamp and the one-car-one-ticket gate always agree on "a car is here". */
  #onInput(e: DeviceInputEvent): void {
    // Reconcile first so a lamp added/changed since boot (no restart) is picked up.
    this.#reconcile();
    const present = e.edge === "on";
    for (const lamp of this.#lamps.values()) {
      if (lamp.controllerId !== e.deviceId) continue;
      // A lamp's trigger is its own `triggerInput`; if unset, fall back to the controller's
      // entry-relay presence terminal (resolved the SAME way the entry flow does) so the
      // lamp and the one-car-one-ticket gate always agree on "a car is here".
      const trigger =
        lamp.spec.triggerInput ?? relayForPresence(this.#db, e.deviceId, e.input)?.presenceInput;
      if (trigger !== e.input) continue; // not this lamp's trigger terminal
      if (present === lamp.present) continue;
      lamp.present = present;
      this.#apply(lamp);
    }
  }

  /** Lane status changed: a camera-confirmed car in the entry and/or exit zone. */
  #onLane(s: LaneStatusEvent): void {
    if (s.entry === this.#entryBusy && s.exit === this.#exitBusy) return;
    this.#entryBusy = s.entry;
    this.#exitBusy = s.exit;
    // Re-render every lamp (each picks its own lane's camera in #apply).
    for (const lamp of this.#lamps.values()) this.#apply(lamp);
  }

  /** Compute + render the target state for one lamp. Drives are fire-and-forget (the
   *  timer/state machine is synchronous; the UDP write resolves on its own). */
  #apply(lamp: LampState): void {
    // SOLID only once THIS lamp's lane camera confirms a car (default entry).
    const laneBusy = lamp.spec.lockLane === "exit" ? this.#exitBusy : this.#entryBusy;
    const target: LightState = !lamp.present ? "off" : laneBusy ? "solid" : "blink";
    if (target === lamp.rendered) return; // already rendering this state

    // Tear down any running blink before switching states.
    if (lamp.blink) {
      clearInterval(lamp.blink);
      lamp.blink = null;
    }
    lamp.rendered = target;

    if (target === "off") {
      lamp.desiredOn = false;
      this.#pump(lamp);
    } else if (target === "solid") {
      lamp.desiredOn = true;
      this.#pump(lamp);
    } else {
      // BLINK: a wall-clock timer flips ONLY the desired flag; #pump does the actual
      // (serialized) UDP send. A symmetric cadence uses one interval; an asymmetric one
      // re-arms each phase with its own duration. Sends never overlap or reorder, so the
      // relay can't get stuck on a stale packet.
      const onMs = lamp.spec.blinkOnMs && lamp.spec.blinkOnMs > 0 ? lamp.spec.blinkOnMs : DEFAULT_BLINK_MS;
      const offMs = lamp.spec.blinkOffMs && lamp.spec.blinkOffMs > 0 ? lamp.spec.blinkOffMs : DEFAULT_BLINK_MS;
      lamp.blinkOn = true;
      lamp.desiredOn = true;
      const tick = () => {
        lamp.blinkOn = !lamp.blinkOn;
        lamp.desiredOn = lamp.blinkOn;
        this.#pump(lamp);
        if (onMs !== offMs && lamp.blink) {
          clearInterval(lamp.blink);
          lamp.blink = setInterval(tick, lamp.blinkOn ? onMs : offMs);
          lamp.blink.unref?.();
        }
      };
      lamp.blink = setInterval(tick, onMs);
      lamp.blink.unref?.();
      this.#pump(lamp);
    }
  }

  /** Serialized per-lamp worker: drive the relay toward `desiredOn`, one UDP send at a
   *  time. Because UDP is unordered, concurrent on/off sends previously raced and left
   *  the relay stuck on a stale packet. Here a single in-flight send is guaranteed
   *  (`sending` guard); when it resolves, if the desired state moved on we send again —
   *  so the LAST desired state is always the one finally asserted on the device. */
  #pump(lamp: LampState): void {
    if (lamp.sending) return; // a send is already in flight; it'll re-check on completion
    if (lamp.confirmedOn === lamp.desiredOn) return; // already there — no redundant UDP
    const aux = this.#resolveAux(lamp.controllerId);
    if (!aux) return;
    const target = lamp.desiredOn;
    lamp.sending = true;
    void aux
      .setAux(lamp.spec.relay, target)
      .then(() => {
        lamp.confirmedOn = target;
      })
      .catch((err: unknown) => {
        // Leave confirmedOn unchanged so the next pump retries this state. Never escalates.
        this.#logger.error(`button-light setAux failed (${lamp.controllerId} R${lamp.spec.relay}): ${(err as Error).message}`);
      })
      .finally(() => {
        lamp.sending = false;
        // Desired state may have changed (or the send failed) while we were busy —
        // re-pump to converge. This is what makes the final state authoritative.
        if (lamp.confirmedOn !== lamp.desiredOn) this.#pump(lamp);
      });
  }

  /** Build the live aux-output adapter for a controller, or null (logged once). */
  #auxFromRegistry(controllerId: string): AuxOutputDevice | null {
    const row = this.#db.select().from(devices).where(eq(devices.id, controllerId)).get();
    if (!row) return null;
    const driver = registry.get(row.driverId);
    if (!driver) return null;
    let device: unknown;
    try {
      device = driver.create(row.config as never);
    } catch {
      return null;
    }
    if (!hasAuxOutput(device)) {
      if (!this.#warned.has(controllerId)) {
        this.#warned.add(controllerId);
        this.#logger.warn(`button-light: controller ${controllerId} (${row.driverId}) has no aux-output — lamp ignored`);
      }
      return null;
    }
    return device;
  }

  /** Unsubscribe, stop all blink timers, and best-effort drive every lamp OFF. */
  stop(): void {
    this.#unsubInput?.();
    this.#unsubLane?.();
    this.#unsubInput = null;
    this.#unsubLane = null;
    for (const lamp of this.#lamps.values()) {
      if (lamp.blink) {
        clearInterval(lamp.blink);
        lamp.blink = null;
      }
      // Best-effort fail-OFF on shutdown.
      this.#finalOff(lamp);
    }
  }

  /** Drive a lamp OFF as a one-shot (used when dropping/stopping a lamp): set desired
   *  OFF and pump. The serialized worker still applies, so this can't collide with an
   *  in-flight send — it converges to OFF. */
  #finalOff(lamp: LampState): void {
    lamp.desiredOn = false;
    this.#pump(lamp);
  }

  /** Test seam: current high-level state being rendered for a lamp (controller + relay).
   *  `relay` defaults to the controller's only/first alert relay for single-lamp tests. */
  stateOf(controllerId: string, relay?: number): LightState | null {
    return this.#lamp(controllerId, relay)?.rendered ?? null;
  }

  /** Test seam: the state last CONFIRMED on the device for a lamp (after a successful
   *  send). null = unknown / nothing sent yet. `relay` defaults to the only alert relay. */
  confirmedOf(controllerId: string, relay?: number): boolean | null {
    return this.#lamp(controllerId, relay)?.confirmedOn ?? null;
  }

  /** Resolve a lamp by controller + relay. When `relay` is omitted, returns the
   *  controller's single lamp (the common single-alert case); ambiguous if several. */
  #lamp(controllerId: string, relay?: number): LampState | undefined {
    if (relay != null) return this.#lamps.get(lampKey(controllerId, relay));
    for (const lamp of this.#lamps.values()) if (lamp.controllerId === controllerId) return lamp;
    return undefined;
  }
}

/** Composite key for the lamp map (a controller may carry several alert relays). */
function lampKey(controllerId: string, relay: number): string {
  return `${controllerId}:${relay}`;
}

/** Build a controller row's live aux device (exported for reuse/tests). */
export function buildAux(db: Db, row: DeviceRow): AuxOutputDevice | null {
  const driver = registry.get(row.driverId);
  if (!driver) return null;
  try {
    const device = driver.create(row.config as never);
    return hasAuxOutput(device) ? device : null;
  } catch {
    return null;
  }
}