import { randomInt, randomUUID } from "node:crypto";
import { deviceEvents as deviceEventsTable, eq, sessions, siteConfig, type Db, type DeviceRow } from "@parking/db";
import {
  NoPrinterAvailableError,
  printWithFailover,
  registry,
  type AccessControlDevice,
  type PrinterDevice,
  type PrinterInstance,
  type TicketData,
  type TicketHeader,
} from "@parking/devices";
import { DEFAULT_VEHICLE_CATEGORY, reasonPayload } from "@parking/shared";
import type { FastifyBaseLogger } from "fastify";
import type { DeviceInputEvent } from "./device-events.js";
import { getOccupancy } from "./occupancy.js";
import type { EventLog } from "./event-log.js";
import { devicesByDirection, relayForButton, relayForPresence, type ResolvedRelay } from "./device-resolve.js";
import { snapshotAsync } from "./snapshot.js";
import type { VisionClient } from "./vision-client.js";

// The transient ENTRY flow: a button press → print a ticket → sign a vehicle_entry
// → open the barrier. The button is wired into an access controller's input; the
// admin maps that input terminal to a relay (config.relays[].button), so a press
// resolves to exactly the entry relay it should open. See entry-exit-points.md.
//
// Two invariants from the threat model + safety analysis:
//   1. SIGNED BEFORE OPEN — the vehicle_entry is appended to the signed ledger
//      BEFORE pulseOpen fires; an open with no matching signed event is the fraud
//      signal (wiki/concepts/append-only-event-chain.md).
//   2. HOLD ON PRINT FAILURE — a transient with no ticket can't pay on exit, so if
//      all printers are down we do NOT open. We sign an `anomaly` (attempt, ticket
//      unprinted) and leave the barrier closed; the operator handles the held car.
//      Crucially, NO vehicle_entry is written in that case — we never record an
//      "entered" event for a car that didn't get in (decision 2026-06-15).
//
// Ordering: print → (ok) sign vehicle_entry → pulseOpen → snapshot → cache session.
//                   (fail) sign anomaly, stop.
//
// ONE CAR = ONE TICKET (anti-double-press). The entry button can be physically held
// or mashed; without a guard each press mints a fresh ticket + signed vehicle_entry
// (corrupting occupancy and letting a transient shop the cheapest ticket at exit). The
// guard is per-relay and CONFIGURED on the relay spec (config.relays[]), chosen by what
// barrier feedback exists at the lane:
//   - PRESENCE loop (preferred): `presenceInput` ties ticketing to a real vehicle. A
//     press prints only while a car is present, and NO second ticket issues until the
//     loop CLEARS (car drove in) and a new car re-occupies it. We observe the loop's
//     input edges to track presence + "armed" per relay.
//   - COOLDOWN (fallback, no feedback): `entryCooldownSec` suppresses repeat presses on
//     the relay for N seconds after a ticket. A timer — mitigation, not a guarantee.
// A suppressed press is recorded as UNSIGNED telemetry (a no-op, not a fraud anomaly).
// See wiki/concepts/entry-double-press.md.

/** Per-relay anti-double-press state, keyed `controllerId:relay`. */
interface RelayGuardState {
  /** Last successful ticket time (ms epoch) — drives the cooldown check. */
  lastTicketAt: number;
  /** PRESENCE mode: is a vehicle currently on the loop? (from loop input edges) */
  present: boolean;
  /** PRESENCE mode: ready to issue a ticket for a NEW car. Set false after a ticket
   *  prints; re-armed when the loop CLEARS (the car drove through). */
  armed: boolean;
}

export class EntryFlow {
  readonly #db: Db;
  readonly #log: EventLog;
  readonly #logger: FastifyBaseLogger;
  /** Guard against double-fire from the same physical press (on edge only). */
  readonly #inFlight = new Set<string>();
  /** Per-relay one-car-one-ticket state (presence + cooldown), keyed controllerId:relay. */
  readonly #guard = new Map<string, RelayGuardState>();
  /** Optional vision client — passed to snapshotAsync so ANPR runs on the entry image. */
  readonly #vision: VisionClient | null;

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

  /** Handle a device input edge. Two kinds of edge matter to this flow:
   *  (1) an ENTRY BUTTON press (rising edge) → run entry, subject to the per-relay
   *      anti-double-press guard; (2) a PRESENCE LOOP edge (either direction) → update
   *      presence state so the guard knows when a car arrives/leaves. The same physical
   *      input is never both, so we resolve each independently. */
  async onInput(e: DeviceInputEvent): Promise<void> {
    // Presence-loop edge (both directions matter): keep the per-relay state current.
    const presence = relayForPresence(this.#db, e.deviceId, e.input);
    if (presence) {
      this.#onPresenceEdge(presence, e.edge);
      return; // a loop input is not a button — nothing else to do
    }

    if (e.edge !== "on") return; // for buttons, the release edge is just telemetry

    // The firing device must be an access controller, and the pressed input terminal
    // must map to an ENTRY (or both) relay — that's an entry button. Anything else
    // (reader/printer edge, exit-only relay's input) is not a transient-entry trigger.
    const resolved = relayForButton(this.#db, e.deviceId, e.input);
    if (!resolved) return;

    // ANTI-DOUBLE-PRESS: is this press allowed to issue a ticket? (presence/cooldown)
    const suppressed = this.#suppressReason(resolved);
    if (suppressed) {
      this.#recordSuppressedPress(e, resolved, suppressed);
      this.#logger.info(`entry press suppressed (${this.#relayKey(resolved)}): ${suppressed}`);
      return;
    }

    const key = `${e.deviceId}:${e.input}`;
    if (this.#inFlight.has(key)) return; // ignore re-fire while one is processing
    this.#inFlight.add(key);
    try {
      await this.#runEntry(resolved);
    } catch (err) {
      this.#logger.error(`entry-flow failed: ${(err as Error).message}`);
    } finally {
      this.#inFlight.delete(key);
    }
  }

  /** Stable per-relay key for the guard map. */
  #relayKey(r: ResolvedRelay): string {
    return `${r.controller.id}:${r.relay}`;
  }

  /** Lazily get (or create) the guard state for a relay. New relays start ARMED and
   *  with no car present, so the first press on a fresh lane works immediately. */
  #guardState(r: ResolvedRelay): RelayGuardState {
    const key = this.#relayKey(r);
    let s = this.#guard.get(key);
    if (!s) {
      s = { lastTicketAt: 0, present: false, armed: true };
      this.#guard.set(key, s);
    }
    return s;
  }

  /** Apply a presence-loop edge to a relay's state. The car ARRIVING re-arms ticketing;
   *  the car LEAVING the loop (after its entry) re-arms for the NEXT car. */
  #onPresenceEdge(r: ResolvedRelay, edge: "on" | "off"): void {
    const s = this.#guardState(r);
    if (edge === "on") {
      s.present = true; // a vehicle is at the barrier
    } else {
      // Loop cleared: the car drove through (or backed off). Re-arm for the next car —
      // this is the gate that makes a *new* car necessary before another ticket.
      s.present = false;
      s.armed = true;
    }
  }

  /** Why a press should be SUPPRESSED (no ticket), or null if it may proceed.
   *  PRESENCE mode is authoritative when a loop is wired; otherwise COOLDOWN; else no
   *  guard (legacy). The two can coexist — presence first, cooldown as a backstop. */
  #suppressReason(r: ResolvedRelay): string | null {
    const s = this.#guardState(r);

    if (typeof r.presenceInput === "number") {
      // Physical one-car-one-ticket: a car must be present AND we must be armed (no
      // ticket already issued for this still-present car).
      if (!s.present) return "no vehicle at the barrier (presence loop clear)";
      if (!s.armed) return "ticket already issued for the car at the barrier";
      return null;
    }

    if (typeof r.entryCooldownSec === "number" && r.entryCooldownSec > 0) {
      const elapsed = Date.now() - s.lastTicketAt;
      if (elapsed < r.entryCooldownSec * 1000) {
        const remain = Math.ceil((r.entryCooldownSec * 1000 - elapsed) / 1000);
        return `within ${r.entryCooldownSec}s entry cooldown (${remain}s left)`;
      }
    }
    return null;
  }

  /** Record a suppressed (repeat/no-car) entry press as UNSIGNED telemetry — a no-op,
   *  not a fraud anomaly, so the signed ledger stays clean (the operator's choice). */
  #recordSuppressedPress(e: DeviceInputEvent, r: ResolvedRelay, reason: string): void {
    try {
      this.#db
        .insert(deviceEventsTable)
        .values({
          id: randomUUID(),
          deviceId: e.deviceId,
          category: "access",
          kind: "input",
          detail: {
            driverId: e.driverId,
            input: e.input,
            edge: e.edge,
            entrySuppressed: true,
            relay: r.relay,
            reason,
          },
          occurredAt: e.at,
        })
        .run();
    } catch (err) {
      this.#logger.error(`suppressed-press telemetry insert failed: ${(err as Error).message}`);
    }
  }

  async #runEntry(resolved: ResolvedRelay): Promise<void> {
    // CAPACITY GATE (transient only). When the lot is full, refuse transient entry:
    // no ticket, no vehicle_entry, no open — sign an anomaly. Subscribers are NOT
    // gated here (their flow ignores site-full; their own maxConcurrent applies), so
    // they aren't locked out. "Full" is a soft policy seam for valet over-
    // capacity later. See wiki/concepts/capacity-occupancy.md.
    const occ = getOccupancy(this.#db);
    if (occ.full) {
      // No ticket id exists for a refused entry, so mint a synthetic ref to key the
      // anomaly + its evidence snapshot together. The operator wants the photo of WHO
      // was turned away (a fraud/dispute signal), so we still fire the entry camera.
      const refusedRef = `REFUSED-${randomUUID().replace(/-/g, "").slice(0, 12)}`;
      await this.#log.append({
        type: "anomaly",
        identity: refusedRef,
        payload: {
          ...reasonPayload("entry.refused.full", { count: occ.count, capacity: occ.capacity ?? 0 }),
          entryRefused: true,
          full: true,
        },
      });
      this.#fireSnapshot("entry", refusedRef);
      this.#logger.warn(`transient entry REFUSED: full (${occ.count}/${occ.capacity})`);
      return;
    }

    const ticketId = newTicketId();
    const issuedAt = new Date().toISOString();
    const printers = this.#loadPrinters();

    // 1. PRINT FIRST. The ticket is the transient's session key — no ticket, no entry.
    const ticket: TicketData = { ticketId, issuedAt, header: this.#ticketHeader() };
    try {
      const printedBy = await printWithFailover(printers, "entry-dispenser", (d: PrinterDevice) =>
        d.printTicket(ticket),
      );
      this.#logger.info(`entry ticket ${ticketId} printed on ${printedBy}`);
      // ONE CAR = ONE TICKET: a ticket is now out for the car at this barrier. Disarm +
      // stamp the cooldown so a repeat press (held button / mashing) issues no second
      // ticket. PRESENCE mode re-arms when the loop clears (car drove in); COOLDOWN mode
      // re-allows after entryCooldownSec. Done on the print success, NOT the open.
      const guard = this.#guardState(resolved);
      guard.lastTicketAt = Date.now();
      guard.armed = false;
    } catch (err) {
      // HOLD: do not open, do not record a vehicle_entry. Sign an anomaly so the
      // failed attempt is in the tamper-evident record for the operator.
      const reason =
        err instanceof NoPrinterAvailableError ? err.message : (err as Error).message;
      await this.#log.append({
        type: "anomaly",
        identity: ticketId,
        payload: { ...reasonPayload("entry.held.noTicket", { detail: reason }), ticketPrinted: false },
      });
      // Capture who is held at the barrier (evidence for the operator handling the car).
      this.#fireSnapshot("entry", ticketId);
      this.#logger.warn(`entry HELD: ${reason} (barrier NOT opened)`);
      return;
    }

    // 2. SIGN the vehicle_entry — BEFORE the relay fires (the core invariant).
    //    `category` is FROZEN here (in the signed payload) so the tariff prices and
    //    later reprices the same way at exit. Today every transient takes the SITE
    //    default category (operator policy, site_config.default_vehicle_category;
    //    falls back to the shared DEFAULT_VEHICLE_CATEGORY). Per-relay capture (a
    //    "bus lane" relay, mirroring how direction is per-relay in device-resolve.ts)
    //    is the future seam — source it from `resolved` then. A V1/no-category tariff
    //    ignores it; only V2 category cards consult it.
    const cfg = this.#db.select().from(siteConfig).where(eq(siteConfig.id, 1)).get();
    const category =
      cfg?.defaultVehicleCategory && cfg.defaultVehicleCategory.length > 0
        ? cfg.defaultVehicleCategory
        : DEFAULT_VEHICLE_CATEGORY;
    await this.#log.append({
      type: "vehicle_entry",
      direction: "entry",
      source: "ticket",
      identity: ticketId,
      payload: { sessionRef: ticketId, ticketPrinted: true, category },
      occurredAt: issuedAt,
    });

    // 3. OPEN the resolved entry barrier (intent only; the barrier owns the close).
    const access = this.#buildAccess(resolved.controller);
    if (access) await access.pulseOpen(resolved.relay);
    else this.#logger.warn(`entry signed for ${ticketId} but the entry relay won't build`);

    // 3b. SNAPSHOT — fire the entry camera(s), never awaited (evidence, not a gate;
    //     a camera failure must not delay or block the already-open barrier).
    this.#fireSnapshot("entry", ticketId);

    // 4. Update the session projection cache (rebuildable from the ledger; this is
    //    just a fast read-model, never the source of truth).
    try {
      this.#db
        .insert(sessions)
        .values({ id: ticketId, identity: ticketId, source: "ticket", enteredAt: issuedAt, state: "open" })
        .run();
    } catch (err) {
      // Cache miss is non-fatal — the ledger is authoritative and the projection
      // can be rebuilt. Log it; don't fail the (already-open) entry.
      this.#logger.error(`session-cache insert failed for ${ticketId}: ${(err as Error).message}`);
    }
  }

  /** Fire the entry camera(s) for an identity; never awaited (evidence, not a gate).
   *  Used on both the OPEN path and the refused/held anomaly paths — a turned-away or
   *  held car is exactly when the operator wants the photo. */
  #fireSnapshot(direction: "entry", identity: string): void {
    void snapshotAsync({ db: this.#db, direction, identity, logger: this.#logger, vision: this.#vision }).catch(
      (err) => this.#logger.error(`entry snapshot error: ${(err as Error).message}`),
    );
  }

  /** Build a live access adapter from a resolved controller row, or null. */
  #buildAccess(row: DeviceRow): AccessControlDevice | null {
    const driver = registry.get(row.driverId);
    if (!driver) return null;
    try {
      return driver.create(row.config as never) as AccessControlDevice;
    } catch {
      return null;
    }
  }

  /** Build live ENTRY printer instances (for failover selection). */
  #loadPrinters(): PrinterInstance[] {
    const rows = devicesByDirection(this.#db, "printer", "entry"); // already enabled-filtered
    const out: PrinterInstance[] = [];
    for (const row of rows) {
      const driver = registry.get(row.driverId);
      if (!driver) continue;
      const cfg = row.config as Record<string, unknown>;
      const role = cfg.role === "booth-receipt" ? "booth-receipt" : "entry-dispenser";
      try {
        out.push({
          id: row.id,
          role,
          failoverRank: typeof cfg.failoverRank === "number" ? cfg.failoverRank : 0,
          device: driver.create(cfg as never) as PrinterDevice,
        });
      } catch {
        // skip a printer whose config won't build
      }
    }
    return out;
  }

  /** Park identity for the ticket header, from site_config (all fields optional;
   *  the driver prints only what's set). See wiki/concepts/site-metadata.md. */
  #ticketHeader(): TicketHeader | undefined {
    const row = this.#db.select().from(siteConfig).where(eq(siteConfig.id, 1)).get();
    if (!row) return undefined;
    return {
      parkName: row.parkName,
      operatorName: row.operatorName,
      nius: row.nius,
      address: row.address,
      phone: row.phone,
    };
  }
}

/**
 * Opaque, unguessable transient ticket id (wiki/concepts/ticket-encoding.md).
 *
 * Format: 11 digits = 10 cryptographically-random digits + 1 trailing Luhn check
 * digit. All-numeric so the booth can read it on ANY legacy 1D barcode scanner and
 * an operator can hand-key it if every reader is down. RANDOM (not sequential): the
 * id must stay unguessable so an attacker can't iterate to claim a cheaper session
 * — the anti-fraud property the wiki settles.
 *
 * Length is driven by GUESS-RESISTANCE, not volume: with 10^10 valid ids and the
 * Luhn digit rejecting 9/10 of malformed guesses, a blind attempt at a currently-OPEN
 * ticket lands at ~1-in-10^7 even with thousands parked — comfortably safe — while
 * being two digits (≈2 barcode modules) narrower than the old 13. Collisions are
 * negligible at lot scale; the unique constraints on ledger_events.index / sessions.id
 * are the backstop. (Older 13-digit ids stay valid — the id is opaque, length-agnostic.)
 * The Luhn digit lets a manual entry reject a typo (validateTicketCode) instead of
 * failing as "session not found".
 */
function newTicketId(): string {
  let body = "";
  for (let i = 0; i < 10; i += 1) body += String(randomInt(10));
  return body + luhnCheckDigit(body);
}

/** The Luhn (mod-10) check digit for an all-digit string. */
function luhnCheckDigit(digits: string): string {
  let sum = 0;
  // Walk right-to-left; the check digit sits at position 0 from the right, so the
  // last body digit is an "even" position that gets doubled.
  let double = true;
  for (let i = digits.length - 1; i >= 0; i -= 1) {
    let d = digits.charCodeAt(i) - 48;
    if (double) {
      d *= 2;
      if (d > 9) d -= 9;
    }
    sum += d;
    double = !double;
  }
  return String((10 - (sum % 10)) % 10);
}

/**
 * True if `code` is a well-formed ticket code: all digits and a valid Luhn checksum.
 * Lets a manual-entry path (operator types the code off the ticket when readers are
 * down) reject a typo up front. A scanned/looked-up id that predates this format
 * (e.g. legacy `T-<uuid>`) won't pass — callers should only gate MANUAL entry on it,
 * never reject an id that already exists in the ledger. See ticket-encoding.md.
 */
export function validateTicketCode(code: string): boolean {
  // Length-agnostic: an all-digit code whose last digit is the Luhn check of the rest.
  // Accepts the current 11-digit ids AND any legacy 13-digit ones still in circulation
  // (the id is opaque; only the digits+checksum shape matters). The 10..14 bound keeps
  // a stray short/long string from being mistaken for a ticket. See ticket-encoding.md.
  if (!/^\d{10,14}$/.test(code)) return false;
  const body = code.slice(0, -1);
  return luhnCheckDigit(body) === code[code.length - 1];
}