/**
 * Capacity, holds and bookings.
 *
 * `MemoryReservationStore` is the reference implementation of the reservation
 * semantics. The production store (app/services/reservations.server.ts) implements
 * the same contract on Postgres with row-level locking; both are covered by the
 * same behavioural tests.
 *
 * Capacity unit (v1): orders, not items.
 */
import type { Booking, LocationConfig, Method, PeakDay, UsageSnapshot } from "./types";
import { peakFor, usageKey } from "./availability";

export interface Caps {
  dayCap: number | null;
  slotCap: number | null;
}

export function capsFor(
  loc: LocationConfig,
  method: Method,
  date: string,
  slot: string,
  peaks: PeakDay[],
): Caps {
  const cfg = loc.methods[method];
  const peak = peakFor(peaks, loc.id, method, date);
  let tplCap: number | null | undefined;
  if (cfg?.slotMode === "explicit") {
    const [start, end] = slot.split("-");
    for (const list of Object.values(cfg.slots ?? {}))
      for (const s of list ?? []) if (s.start === start && s.end === end && s.capacity != null) tplCap = s.capacity;
  }
  return {
    dayCap: peak?.dailyCapacity ?? cfg?.dailyCapacity ?? null,
    slotCap: peak?.slotCapacity ?? tplCap ?? cfg?.slotCapacity ?? null,
  };
}

export interface Selection {
  locationId: string;
  method: Method;
  date: string;
  slot: string; // "HH:MM-HH:MM"
}

export interface Hold extends Selection {
  token: string;
  expiresAt: number;
}

export type HoldResult =
  | { ok: true; hold: Hold }
  | { ok: false; code: "DAY_FULL" | "SLOT_FULL"; message: string };

export type ConfirmResult =
  | { ok: true; booking: Booking; duplicate: boolean; reReserved?: boolean }
  | { ok: false; booking: Booking; code: "NEEDS_REVIEW"; message: string };

export interface WaitlistEntry extends Selection {
  id: string;
  contact: { email?: string; phone?: string; name?: string };
  createdAt: number;
  notifiedAt?: number;
}

export class MemoryReservationStore {
  holds = new Map<string, Hold>();
  bookings = new Map<string, Booking>();
  waitlist: WaitlistEntry[] = [];
  audit: { at: number; actor: string; bookingId: string; action: string; before?: unknown; after?: unknown }[] = [];
  private seq = 0;

  private counts(sel: Selection, now: number, excludeToken?: string, excludeBooking?: string) {
    let day = 0;
    let slot = 0;
    const same = (s: Selection) => s.locationId === sel.locationId && s.method === sel.method && s.date === sel.date;
    for (const b of this.bookings.values()) {
      // Only confirmed bookings consume capacity; flagged ones wait for a merchant decision.
      if (b.id === excludeBooking || b.status !== "confirmed") continue;
      const s = { locationId: b.locationId, method: b.method, date: b.date, slot: `${b.slotStart}-${b.slotEnd}` };
      if (same(s)) {
        day++;
        if (s.slot === sel.slot) slot++;
      }
    }
    for (const h of this.holds.values()) {
      if (h.token === excludeToken || h.expiresAt <= now) continue;
      if (same(h)) {
        day++;
        if (h.slot === sel.slot) slot++;
      }
    }
    return { day, slot };
  }

  usage(now: number): UsageSnapshot {
    const out: UsageSnapshot = {};
    const add = (s: Selection) => {
      const k = usageKey(s.locationId, s.method, s.date);
      out[k] ??= { day: 0, slots: {} };
      out[k].day++;
      out[k].slots[s.slot] = (out[k].slots[s.slot] ?? 0) + 1;
    };
    for (const b of this.bookings.values())
      if (b.status === "confirmed")
        add({ locationId: b.locationId, method: b.method, date: b.date, slot: `${b.slotStart}-${b.slotEnd}` });
    for (const h of this.holds.values()) if (h.expiresAt > now) add(h);
    return out;
  }

  private fits(sel: Selection, caps: Caps, now: number, excludeToken?: string, excludeBooking?: string) {
    const c = this.counts(sel, now, excludeToken, excludeBooking);
    if (caps.dayCap != null && c.day >= caps.dayCap) return "DAY_FULL" as const;
    if (caps.slotCap != null && c.slot >= caps.slotCap) return "SLOT_FULL" as const;
    return null;
  }

  /** Atomic check-and-reserve. Re-holding with the same token moves the hold. */
  hold(token: string, sel: Selection, caps: Caps, now: number, holdMinutes: number): HoldResult {
    const full = this.fits(sel, caps, now, token);
    if (full) return { ok: false, code: full, message: full === "DAY_FULL" ? "Fully booked for this day" : "This time slot was just taken" };
    const hold: Hold = { ...sel, token, expiresAt: now + holdMinutes * 60000 };
    this.holds.set(token, hold);
    return { ok: true, hold };
  }

  release(token: string) {
    this.holds.delete(token);
  }

  sweep(now: number): number {
    let n = 0;
    for (const [t, h] of this.holds) if (h.expiresAt <= now) (this.holds.delete(t), n++);
    return n;
  }

  /**
   * Confirm a hold against an order. Idempotent per orderId (duplicate webhooks are safe).
   * Expired hold: re-reserve if capacity still allows, otherwise flag for review —
   * never silently overbook.
   */
  confirm(
    orderId: string,
    token: string | null,
    fallbackSel: Selection | null,
    caps: Caps,
    now: number,
    details: Partial<Booking> & { timezone: string },
  ): ConfirmResult {
    const existing = [...this.bookings.values()].find((b) => b.orderId === orderId);
    if (existing) return { ok: true, booking: existing, duplicate: true };

    const hold = token ? this.holds.get(token) : undefined;
    const sel = hold ?? fallbackSel;
    const id = `bk_${++this.seq}`;
    const base = (status: Booking["status"]): Booking => ({
      ...details,
      id,
      orderId,
      status,
      method: sel!.method,
      locationId: sel!.locationId,
      date: sel!.date,
      slotStart: sel!.slot.split("-")[0],
      slotEnd: sel!.slot.split("-")[1],
      rescheduleCount: 0,
    });
    if (!sel) {
      const b: Booking = { ...details, id, orderId, status: "needs_review", method: "pickup", locationId: "", date: "" };
      this.bookings.set(id, b);
      return { ok: false, booking: b, code: "NEEDS_REVIEW", message: "Order has no scheduling data" };
    }
    const live = hold && hold.expiresAt > now;
    if (!live) {
      const full = this.fits(sel, caps, now, token ?? undefined);
      if (full) {
        const b = base("needs_review");
        this.bookings.set(id, b);
        if (token) this.holds.delete(token);
        this.log(now, "system", id, "flagged", undefined, { reason: full });
        return { ok: false, booking: b, code: "NEEDS_REVIEW", message: "Hold expired and the slot filled up" };
      }
    }
    const b = base("confirmed");
    this.bookings.set(id, b);
    if (token) this.holds.delete(token);
    this.log(now, "system", id, "confirmed");
    return { ok: true, booking: b, duplicate: false, reReserved: !live };
  }

  /** Atomic move: validates the new slot, then releases old + takes new together. */
  reschedule(
    bookingId: string,
    sel: Selection,
    caps: Caps,
    now: number,
    actor: string,
  ): { ok: true; booking: Booking; freed: Selection } | { ok: false; message: string } {
    const b = this.bookings.get(bookingId);
    if (!b || b.status !== "confirmed") return { ok: false, message: "Booking can't be rescheduled" };
    const full = this.fits(sel, caps, now, undefined, bookingId);
    if (full) return { ok: false, message: full === "DAY_FULL" ? "That day is fully booked" : "That slot is full" };
    const before = { ...b };
    const freed: Selection = { locationId: b.locationId, method: b.method, date: b.date, slot: `${b.slotStart}-${b.slotEnd}` };
    const [s, e] = sel.slot.split("-");
    Object.assign(b, {
      locationId: sel.locationId,
      method: sel.method,
      date: sel.date,
      slotStart: s,
      slotEnd: e,
      rescheduleCount: (b.rescheduleCount ?? 0) + 1,
    });
    this.log(now, actor, bookingId, "rescheduled", pick(before), pick(b));
    return { ok: true, booking: b, freed };
  }

  cancel(orderId: string, now: number, releaseCapacity = true): Booking | null {
    const b = [...this.bookings.values()].find((x) => x.orderId === orderId);
    if (!b || b.status === "cancelled") return b ?? null;
    const before = { ...b };
    b.status = releaseCapacity ? "cancelled" : b.status;
    this.log(now, "system", b.id, "cancelled", pick(before), pick(b));
    return b;
  }

  joinWaitlist(sel: Selection, contact: WaitlistEntry["contact"], now: number): WaitlistEntry {
    const e: WaitlistEntry = { ...sel, id: `wl_${++this.seq}`, contact, createdAt: now };
    this.waitlist.push(e);
    return e;
  }

  /** Who to notify when capacity frees up for a selection (FIFO, one at a time). */
  nextWaitlisted(sel: Selection): WaitlistEntry | null {
    return (
      this.waitlist.find(
        (w) =>
          !w.notifiedAt &&
          w.locationId === sel.locationId &&
          w.method === sel.method &&
          w.date === sel.date &&
          (w.slot === sel.slot || w.slot === "*"),
      ) ?? null
    );
  }

  private log(at: number, actor: string, bookingId: string, action: string, before?: unknown, after?: unknown) {
    this.audit.push({ at, actor, bookingId, action, before, after });
  }
}

function pick(b: Booking) {
  return { locationId: b.locationId, method: b.method, date: b.date, slotStart: b.slotStart, slotEnd: b.slotEnd, status: b.status };
}