/**
 * When a place frees up (cancellation or reschedule), offer it to the first person
 * waiting: reserve it as a hold for `waitlistOfferMinutes` and message them a link
 * that adopts the hold in their cart.
 */
import { randomBytes } from "node:crypto";
import prisma from "../db.server";
import { capsFor, type Selection } from "../engine/capacity";
import { loadShopConfig } from "./config.server";
import { send } from "./notifications.server";
import { features } from "./plans";
import { ReservationService } from "./reservations.server";

const reservations = new ReservationService(prisma);

export async function offerFreedPlace(domain: string, freed: Selection, now = new Date()) {
  const cfg = await loadShopConfig(domain);
  if (!features(cfg.shop.plan).waitlist) return null;
  const entry = await prisma.waitlistEntry.findFirst({
    where: {
      shopId: cfg.shop.id,
      locationId: freed.locationId,
      method: freed.method,
      date: freed.date,
      slot: { in: [freed.slot, "*"] },
      offeredAt: null,
    },
    orderBy: { createdAt: "asc" },
  });
  const loc = cfg.locations.find((l) => l.id === freed.locationId);
  if (!entry || !loc) return null;
  const token = `wl_${randomBytes(16).toString("base64url")}`;
  const caps = capsFor(loc, freed.method, freed.date, freed.slot, cfg.peakDays);
  const held = await reservations.hold(cfg.shop.id, token, freed, caps, now, cfg.settings.waitlistOfferMinutes);
  if (!held.ok) return null;
  await prisma.waitlistEntry.update({ where: { id: entry.id }, data: { offeredAt: now, offerToken: token } });
  const link = `https://${domain}/cart?datewise_offer=${token}`;
  const nice = new Date(`${freed.date}T12:00:00Z`).toLocaleDateString("en-CA", { weekday: "long", month: "long", day: "numeric", timeZone: "UTC" });
  const body = `Good news${entry.name ? `, ${entry.name}` : ""}! A ${freed.method} place opened on ${nice} (${freed.slot.replace("-", "–")}). We're holding it for you for ${cfg.settings.waitlistOfferMinutes} minutes: ${link}`;
  const channel = entry.email ? "email" : features(cfg.shop.plan).smsWhatsapp ? "sms" : null;
  if (channel)
    await send(cfg.settings, domain.replace(".myshopify.com", ""), {
      channel,
      to: (entry.email ?? entry.phone)!,
      subject: "A place opened up for you",
      body,
    }).catch((e) => console.error("waitlist notify failed", e));
  return { entryId: entry.id, token };
}