import { desc, eq, ledgerEvents, sessions, tariffVersions, tariffs, type Db, type DeviceRow } from "@parking/db";
import { registry, type AccessControlDevice } from "@parking/devices";
import { firstRelayByDirection, type ResolvedRelay } from "./device-resolve.js";
import { snapshotAsync } from "./snapshot.js";
import type { VisionClient } from "./vision-client.js";
import { computeFee, reasonPayload, renderReasonEn, type LedgerPayload, type TariffStructure } from "@parking/shared";
import type { FastifyBaseLogger } from "fastify";
import type { DeviceReadEvent, ReadOutcome } from "./device-events.js";
import type { EventLog } from "./event-log.js";

// The EXIT flow (pay-on-foot model): a credential read at the exit lane → look up
// the session → validate it is PAID and within the walk-back grace → sign a
// vehicle_exit → open. Payment is decoupled from exit (it happens earlier at the
// pay station); the exit lane only VALIDATES. See wiki/concepts/parking-session.md.
//
// Validation is a fold over the SIGNED ledger (the authoritative record), not the
// projection cache: find the open vehicle_entry for this identity, then a covering
// payment within grace. The cache is updated after, for fast reads.
//
// REJECT (barrier stays closed) when unpaid / over grace — this is correct business
// logic, NOT a fail-state. "Exit fails OPEN" (fail-state-safety) is about the SYSTEM
// being unable to decide (power/host loss), not about an unpaid car; an unpaid driver
// is sent back to the pay station, the rejection is logged.
//
// NOTE: payments / the pay station don't exist yet, so no session is ever PAID — every
// transient exit currently REJECTS (logged). That's the correct end-state; it becomes
// passable once the pay-station + `payment` events land.

interface SessionView {
  readonly identity: string;
  readonly enteredAt: string;
  readonly open: boolean; // no vehicle_exit yet
  readonly paidAt: string | null; // latest payment time, if any
  /** A SUBSCRIPTION occurrence (prepaid; entry payload permit:true). Authorized to
   *  exit / re-open without a `payment`. */
  readonly subscription: boolean;
  readonly graceExitMin: number | null; // from the payment's tariff context, if known
  // Within the FREE entry-grace window (a quick in-and-out that the tariff prices at
  // 0). When true the exit opens without a pay-station visit — we mint a $0 payment so
  // the ledger's "an exit is covered by a payment" invariant still holds. Null when no
  // active tariff resolves (then we fall back to the normal paid check).
  readonly freeGrace: { tariffVersionId: string; currency: string; graceExitMin: number } | null;
}

/** Result of a booth-driven exit (POST /api/exit). `ok=false` = validation rejected
 *  (nothing signed beyond an anomaly). `ok=true, opened=false` = exit IS signed but
 *  the barrier didn't open (payment stands; operator opens manually). */
export type BoothExitResult =
  | { ok: false; status: "invalid" | "no_session" | "closed" | "unpaid" | "grace_expired"; reason: string }
  | { ok: true; opened: true }
  | { ok: true; opened: false; reason: string };

/** Result of a human-intervention barrier re-open (POST /api/barrier/reopen).
 *  `ok=false` = refused (no session / unpaid). `ok=true, opened=false` = the
 *  intervention was recorded (signed anomaly) but the relay did not fire. */
export type BoothReopenResult =
  | { ok: false; reason: string }
  | { ok: true; opened: boolean; reason?: string };

export class ExitFlow {
  readonly #db: Db;
  readonly #log: EventLog;
  readonly #logger: FastifyBaseLogger;
  readonly #inFlight = new Set<string>();
  /** Optional vision client — passed to snapshotAsync so ANPR runs on the exit 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;
  }

  /**
   * BOOTH-driven exit: the operator (not a reader at the lane) opens the barrier for
   * a ticket. Runs the SAME validation as the reader path — there is no booth-only
   * bypass that admits an unpaid car (see wiki/concepts/booth-exit-flow.md +
   * threat-model.md). On a valid session it signs vehicle_exit, resolves AN exit
   * relay site-wide, pulses it, and fires the exit snapshot.
   *
   * Returns a discriminated result so the route can react precisely:
   *  - { ok: false, status } when validation rejects (unpaid / no session / closed)
   *    — nothing is signed beyond the existing anomaly; the operator takes payment.
   *  - { ok: true, opened: true } on a clean exit.
   *  - { ok: true, opened: false } when the exit IS signed but the relay open FAILED
   *    (offline controller / no exit relay). The signed payment + vehicle_exit STAND
   *    (money was taken, the car is owed an exit) and an `anomaly` is appended so the
   *    operator opens manually. Payment is never rolled back.
   */
  async exitForBooth(identity: string): Promise<BoothExitResult> {
    const id = identity.trim();
    if (!id) return { ok: false, status: "invalid", reason: "ticket id required" };

    const key = `booth:${id}`;
    if (this.#inFlight.has(key)) return { ok: false, status: "invalid", reason: "exit already in progress" };
    this.#inFlight.add(key);
    try {
      const view = this.#sessionFor(id);

      // No open session — unknown/closed ticket. Sign an anomaly (same as the reader
      // path) so a booth attempt on a bad ticket is auditable.
      if (!view || !view.open) {
        const rp = reasonPayload(view ? "exit.refused.closed" : "exit.refused.noSession");
        await this.#log.append({ type: "anomaly", identity: id, payload: { ...rp, exitRefused: true, source: "booth" } });
        this.#fireExitSnapshot(id);
        this.#logger.warn(`booth exit refused (${id}): ${rp.reason}`);
        return { ok: false, status: view ? "closed" : "no_session", reason: rp.reason };
      }

      // PAID + within grace, OR free entry-grace — the same checks the reader uses.
      const freeGrace = view.paidAt == null && view.freeGrace != null;
      const paid = view.paidAt != null;
      const withinGrace =
        paid && view.graceExitMin != null && Date.now() - Date.parse(view.paidAt!) <= view.graceExitMin * 60_000;

      if (!freeGrace && (!paid || !withinGrace)) {
        const rp = reasonPayload(paid ? "exit.refused.graceExpired" : "exit.refused.unpaid");
        await this.#log.append({ type: "anomaly", identity: id, payload: { ...rp, exitRefused: true, source: "booth" } });
        this.#fireExitSnapshot(id);
        this.#logger.warn(`booth exit refused (${id}): ${rp.reason}`);
        return { ok: false, status: paid ? "grace_expired" : "unpaid", reason: rp.reason };
      }

      // Free entry-grace path: mint the $0 payment first (ledger invariant), as the
      // reader path does.
      if (freeGrace && view.freeGrace) {
        await this.#log.append({
          type: "payment",
          identity: id,
          payload: {
            sessionRef: id,
            amountMinor: 0,
            currency: view.freeGrace.currency,
            tariffVersionId: view.freeGrace.tariffVersionId,
            graceExitMin: view.freeGrace.graceExitMin,
            ...reasonPayload("exit.freeGrace"),
          },
        });
      }

      // Resolve AN exit barrier site-wide (no reader binding to follow at the booth).
      const resolved = firstRelayByDirection(this.#db, "exit");

      // Sign the vehicle_exit regardless of whether a relay resolves — the decision
      // to let the car out has been made and validated. Then attempt the open.
      await this.#signExit(id);

      if (!resolved) {
        await this.#openFailedAnomaly(id, "no exit relay configured");
        return { ok: true, opened: false, reason: renderReasonEn("exit.open.noBarrier") };
      }
      const access = this.#buildAccess(resolved.controller);
      if (!access) {
        await this.#openFailedAnomaly(id, "exit controller would not build");
        return { ok: true, opened: false, reason: renderReasonEn("exit.open.unavailable") };
      }
      try {
        await access.pulseOpen(resolved.relay);
      } catch (err) {
        await this.#openFailedAnomaly(id, `pulseOpen failed: ${(err as Error).message}`);
        return { ok: true, opened: false, reason: renderReasonEn("exit.open.failed") };
      }

      this.#fireExitSnapshot(id);
      this.#closeSessionCache(id);
      return { ok: true, opened: true };
    } finally {
      this.#inFlight.delete(key);
    }
  }

  /**
   * HUMAN-INTERVENTION barrier re-open for an ACTIVE session (booth Active Sessions
   * list). The barrier is unconfirmed; a car may be stuck after a damaged-ticket
   * read, a dead scanner, or a phantom re-close (animal / bag / box). The operator
   * opens the barrier with a signed trace.
   *
   * Guard: requires a PAYMENT — no payment, no re-open (the no-unpaid-bypass rule;
   * the UI also hides the button). It re-pulses the exit relay and signs an `anomaly`
   * ("manual barrier open", attributed). Idempotent-safe per identity via #inFlight.
   *
   * CLOSING THE SESSION (fix 2026-06-18): if the session is still OPEN (no
   * `vehicle_exit` yet), the manual re-open *is* this car leaving — so we also sign a
   * `vehicle_exit` (attributed as human-intervention). Without it the paid session
   * would linger in the Active Sessions list FOREVER, since the grace-expiry eviction
   * only applies to already-exited sessions (the T-397815c0 bug). If the session is
   * already CLOSED (a prior exit exists — the phantom re-close case), we do NOT sign a
   * second exit (that would double-count occupancy): anomaly only, as before.
   * See wiki/concepts/booth-exit-flow.md.
   */
  async reopenBarrier(identity: string, operator?: string): Promise<BoothReopenResult> {
    const id = identity.trim();
    if (!id) return { ok: false, reason: "ticket id required" };

    const view = this.#sessionFor(id);
    if (!view) return { ok: false, reason: "no session for ticket" };
    // Authorization to re-open: a SUBSCRIPTION occurrence (prepaid — exactly the case
    // the operator must assist when the exit reader / card fails) OR a transient whose
    // payment is STILL WITHIN the walk-back grace window. A stale payment does NOT
    // authorize a free open: a car that paid once and then sat inside past grace owes a
    // top-up for the extra time — letting it out on the old payment is the overstay-fraud
    // path. So we mirror the exit flow's grace check here (not just in the UI): an
    // unpaid OR grace-expired transient takes the pay/exit (top-up) flow instead.
    // The no-unpaid-bypass + no-free-overstay-exit rules, enforced server-side.
    const paid = view.paidAt != null;
    const withinGrace =
      paid && view.graceExitMin != null && Date.now() - Date.parse(view.paidAt!) <= view.graceExitMin * 60_000;
    if (!view.subscription && (!paid || !withinGrace)) {
      return {
        ok: false,
        reason: paid ? "walk-back grace expired — take a top-up payment first" : "session not paid — no barrier open without payment",
      };
    }

    const key = `reopen:${id}`;
    if (this.#inFlight.has(key)) return { ok: false, reason: "re-open already in progress" };
    this.#inFlight.add(key);
    try {
      const resolved = firstRelayByDirection(this.#db, "exit");
      // Sign the audited anomaly FIRST (the intervention is recorded whether or not
      // the physical open succeeds).
      await this.#log.append({
        type: "anomaly",
        identity: id,
        payload: {
          ...reasonPayload("exit.manualOpen"),
          source: "booth",
          barrierReopen: true,
          ...(operator ? { operator } : {}),
        },
      });

      // Close an OPEN session: the re-open is the exit. Sign the vehicle_exit so the
      // session leaves the active list + occupancy settles. Skip when already exited
      // (no double-count). Recorded as a human-intervention exit for the audit trail.
      if (view.open) {
        await this.#signExit(id, "manual");
        this.#closeSessionCache(id);
        this.#fireExitSnapshot(id);
        this.#logger.info(`barrier re-open also closed open session ${id} (human-intervention exit)`);
      }

      if (!resolved) {
        this.#logger.warn(`barrier re-open for ${id}: no exit relay configured`);
        return { ok: true, opened: false, reason: renderReasonEn("exit.open.noBarrier") };
      }
      const access = this.#buildAccess(resolved.controller);
      if (!access) {
        this.#logger.warn(`barrier re-open for ${id}: exit controller would not build`);
        return { ok: true, opened: false, reason: renderReasonEn("exit.open.unavailable") };
      }
      try {
        await access.pulseOpen(resolved.relay);
      } catch (err) {
        this.#logger.error(`barrier re-open pulseOpen failed (${id}): ${(err as Error).message}`);
        return { ok: true, opened: false, reason: renderReasonEn("exit.open.failed") };
      }
      this.#logger.info(`manual barrier open for ${id}${operator ? ` by ${operator}` : ""}`);
      return { ok: true, opened: true };
    } finally {
      this.#inFlight.delete(key);
    }
  }

  /** Handle a transient-ticket read at an exit barrier (the relay pre-resolved by the
   *  read dispatcher from the reader's binding, which has ruled out a subscription match). */
  async handleAt(resolved: ResolvedRelay, e: DeviceReadEvent): Promise<ReadOutcome> {
    const key = `${e.deviceId}:${e.value}`;
    if (this.#inFlight.has(key)) return { accepted: false, reason: "duplicate read in flight" };
    this.#inFlight.add(key);
    try {
      return await this.#runExit(resolved, e);
    } catch (err) {
      this.#logger.error(`exit-flow failed: ${(err as Error).message}`);
      return { accepted: false, reason: (err as Error).message };
    } finally {
      this.#inFlight.delete(key);
    }
  }

  async #runExit(resolved: ResolvedRelay, e: DeviceReadEvent): Promise<ReadOutcome> {
    const view = this.#sessionFor(e.value);

    // No matching open session — unknown/duplicate ticket. Reject + log.
    if (!view || !view.open) {
      const rp = reasonPayload(view ? "exit.refused.closed" : "exit.refused.noSession");
      await this.#log.append({
        type: "anomaly",
        identity: e.value,
        payload: { ...rp, exitRefused: true },
      });
      this.#fireExitSnapshot(e.value);
      this.#logger.warn(`exit refused: no open session for ${e.value}`);
      return { accepted: false, direction: "exit", reason: rp.reason };
    }

    // FREE entry-grace: a quick in-and-out the tariff prices at 0 exits at the gate
    // with no pay-station visit. Mint a signed $0 `payment` first so the ledger keeps
    // its "an exit is covered by a payment" invariant, then fall through to open.
    // Only when NOT already paid (a real payment, walk-back grace, takes precedence).
    if (view.paidAt == null && view.freeGrace) {
      await this.#log.append({
        type: "payment",
        // No `source` (not operator-keyed nor a read) — the payload reason marks it.
        identity: e.value,
        payload: {
          sessionRef: e.value,
          amountMinor: 0,
          currency: view.freeGrace.currency,
          tariffVersionId: view.freeGrace.tariffVersionId,
          graceExitMin: view.freeGrace.graceExitMin,
          ...reasonPayload("exit.freeGrace"),
        },
      });
      this.#logger.info(`exit free within entry-grace (${e.value})`);
      return this.#signExitAndOpen(resolved, e);
    }

    // PAID + within walk-back grace?
    const paid = view.paidAt != null;
    const withinGrace =
      paid &&
      view.graceExitMin != null &&
      Date.now() - Date.parse(view.paidAt!) <= view.graceExitMin * 60_000;

    if (!paid || !withinGrace) {
      const rp = reasonPayload(paid ? "exit.refused.graceExpired" : "exit.refused.unpaid");
      await this.#log.append({
        type: "anomaly",
        identity: e.value,
        payload: { ...rp, exitRefused: true, sessionRef: e.value },
      });
      this.#fireExitSnapshot(e.value);
      this.#logger.warn(`exit refused (${e.value}): ${rp.reason}`);
      return { accepted: false, direction: "exit", reason: rp.reason };
    }

    // Valid (a real payment within walk-back grace): sign + open.
    return this.#signExitAndOpen(resolved, e);
  }

  /** Sign the vehicle_exit BEFORE opening, then open, snapshot, and update the cache.
   *  Shared by the paid-exit and free-entry-grace paths. The caller has already
   *  established the session is allowed out (and, for grace, minted the $0 payment). */
  async #signExitAndOpen(resolved: ResolvedRelay, e: DeviceReadEvent): Promise<ReadOutcome> {
    await this.#signExit(e.value, e.kind === "plate" ? "lpr" : "ticket");

    const access = this.#buildAccess(resolved.controller);
    if (access) await access.pulseOpen(resolved.relay);
    else this.#logger.warn(`exit signed for ${e.value} but the exit relay won't build`);

    this.#fireExitSnapshot(e.value);
    this.#closeSessionCache(e.value);
    return { accepted: true, direction: "exit" };
  }

  /** Append the signed vehicle_exit. `source`: "ticket" (booth/reader), "lpr" (plate),
   *  or "manual" (a human-intervention barrier re-open that closes an open session —
   *  see reopenBarrier). */
  async #signExit(identity: string, source: "ticket" | "lpr" | "manual" = "ticket"): Promise<void> {
    await this.#log.append({
      type: "vehicle_exit",
      direction: "exit",
      source,
      identity,
      payload: {
        sessionRef: identity,
        ...(source === "manual" ? reasonPayload("exit.manualOpen") : {}),
      },
    });
  }

  /** Fire the exit camera(s); never awaited (evidence, not a gate). */
  #fireExitSnapshot(identity: string): void {
    void snapshotAsync({
      db: this.#db,
      direction: "exit",
      identity,
      logger: this.#logger,
      vision: this.#vision,
    }).catch((err) => this.#logger.error(`exit snapshot error: ${(err as Error).message}`));
  }

  /** Update the (rebuildable) session projection cache to closed. */
  #closeSessionCache(identity: string): void {
    try {
      this.#db
        .update(sessions)
        .set({ exitedAt: new Date().toISOString(), state: "closed" })
        .where(eq(sessions.id, identity))
        .run();
    } catch (err) {
      this.#logger.error(`session-cache close failed for ${identity}: ${(err as Error).message}`);
    }
  }

  /** Record an audited anomaly when an exit was signed but the barrier didn't open.
   *  The payment + exit STAND; this tells the operator to open manually. */
  async #openFailedAnomaly(identity: string, detail: string): Promise<void> {
    await this.#log.append({
      type: "anomaly",
      identity,
      payload: { ...reasonPayload("exit.open.failed"), detail, source: "booth", exitOpenFailed: true },
    });
    this.#logger.error(`booth exit open failed (${identity}): ${detail}`);
  }

  /** Fold the signed ledger into a session view for one identity (authoritative). */
  #sessionFor(identity: string): SessionView | null {
    const rows = this.#db
      .select()
      .from(ledgerEvents)
      .where(eq(ledgerEvents.identity, identity))
      .orderBy(ledgerEvents.index)
      .all();
    if (rows.length === 0) return null;

    const entry = rows.find((r) => r.type === "vehicle_entry");
    if (!entry) return null;
    // A `void` (cancelled ticket) closes the session like an exit, so a voided ticket
    // presented at exit reads as "already closed" — never re-opens. See void-flow.ts.
    const exited = rows.some((r) => r.type === "vehicle_exit" || r.type === "void");

    let paidAt: string | null = null;
    let graceExitMin: number | null = null;
    for (const r of rows) {
      if (r.type === "payment") {
        paidAt = r.occurredAt;
        const p = (r.payload ?? {}) as LedgerPayload & { graceExitMin?: number };
        if (typeof p.graceExitMin === "number") graceExitMin = p.graceExitMin;
      }
    }

    // Free entry-grace: if the tariff prices entry→now at 0 (a quick in-and-out),
    // the exit may open at the gate. Resolve against the tariff in force at entry,
    // same as the pay station. Null when no payment is needed yet and no tariff
    // resolves — then exit falls back to the normal paid check.
    let freeGrace: SessionView["freeGrace"] = null;
    if (!exited && paidAt == null) {
      const tv = this.#tariffVersionFor(entry.occurredAt);
      if (tv) {
        const structure = tv.structure as unknown as TariffStructure;
        // Same frozen-at-entry category the pay station uses, so the free-grace
        // check agrees with the booth quote for V2 category tariffs.
        const category = (entry.payload as { category?: string } | null)?.category;
        const fee = computeFee(entry.occurredAt, new Date().toISOString(), structure, category);
        if (fee === 0) {
          freeGrace = {
            tariffVersionId: tv.id,
            currency: tv.currency,
            graceExitMin: structure.gracePeriodExitMin,
          };
        }
      }
    }

    const entryPl = (entry.payload ?? {}) as { permit?: boolean; permitId?: string };
    const subscription = entryPl.permit === true || entryPl.permitId != null;

    return {
      identity,
      enteredAt: entry.occurredAt,
      open: !exited,
      paidAt,
      subscription,
      graceExitMin,
      freeGrace,
    };
  }

  /** The tariff version in force at `at` — latest effectiveFrom ≤ at, for the
   *  (single, for now) active site tariff. Mirrors PayStation#tariffVersionFor. */
  #tariffVersionFor(at: string) {
    const tariff = this.#db.select().from(tariffs).where(eq(tariffs.scope, "site")).get();
    if (!tariff) return null;
    const versions = this.#db
      .select()
      .from(tariffVersions)
      .where(eq(tariffVersions.tariffId, tariff.id))
      .orderBy(desc(tariffVersions.effectiveFrom))
      .all();
    return versions.find((v) => v.effectiveFrom <= at) ?? null;
  }

  /** 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;
    }
  }
}