import { APIError } from "payload";
import type { CollectionAfterChangeHook, CollectionBeforeChangeHook, CollectionConfig } from "payload";
import { isAdmin, isAdminFieldLevel } from "@/access";
import { acquireBookingDayLock } from "@/lib/booking/lock";
import {
  alternativeProposedEmail,
  bookingCancelledAdminEmail,
  bookingConfirmedEmail,
  bookingRejectedEmail,
  bookingRequestReceivedEmail,
  newBookingRequestAdminEmail,
} from "@/lib/email/bookingTemplates";
import { sendEmail } from "@/lib/email/sendBookingEmails";
import type { Customer, Event, Offer } from "@/payload-types";

export const APPOINTMENT_TYPES = [
  { label: "Vor Ort", value: "onsite" },
  { label: "Online", value: "online" },
] as const;

export const BOOKING_STATUSES = [
  { label: "Ausstehend", value: "pending" },
  { label: "Bestätigt", value: "confirmed" },
  { label: "Abgelehnt", value: "rejected" },
  { label: "Storniert", value: "cancelled" },
] as const;

function dateKey(iso: string): string {
  return new Date(iso).toISOString().slice(0, 10);
}

function fmtDate(iso: string): string {
  return new Date(iso).toLocaleDateString("de-DE", { day: "2-digit", month: "long", year: "numeric" });
}

function fmtTime(iso: string): string {
  return new Date(iso).toLocaleTimeString("de-DE", { hour: "2-digit", minute: "2-digit" });
}

const appointmentTypeLabel = (value: string) =>
  APPOINTMENT_TYPES.find((t) => t.value === value)?.label ?? value;

async function notifyAdmins(
  req: Parameters<CollectionAfterChangeHook>[0]["req"],
  template: { subject: string; html: string },
) {
  const { docs: admins } = await req.payload.find({ collection: "users", limit: 50, req });
  await Promise.all(admins.filter((admin) => admin.email).map((admin) => sendEmail(admin.email, template)));
}

// Runs whenever a booking is about to become "confirmed": locks the day
// (see lib/booking/lock.ts), re-checks for overlapping confirmed bookings
// inside that same lock/transaction, and — for online appointments — creates
// the linked video-call Event (reusing the existing meeting/password system)
// before the booking itself is written.
const handleConfirmation: CollectionBeforeChangeHook = async ({ data, originalDoc, req, operation }) => {
  if (operation !== "update" || data.status !== "confirmed" || originalDoc?.status === "confirmed") {
    return data;
  }

  const date = data.date ?? originalDoc.date;
  const startTime = data.startTime ?? originalDoc.startTime;
  const endTime = data.endTime ?? originalDoc.endTime;
  const appointmentType = data.appointmentType ?? originalDoc.appointmentType;

  await acquireBookingDayLock(req, dateKey(date));

  const { docs: sameDayConfirmed } = await req.payload.find({
    collection: "booking-requests",
    where: {
      and: [
        { status: { equals: "confirmed" } },
        { id: { not_equals: originalDoc.id } },
        { date: { greater_than_equal: new Date(new Date(date).setHours(0, 0, 0, 0)).toISOString() } },
        { date: { less_than_equal: new Date(new Date(date).setHours(23, 59, 59, 999)).toISOString() } },
      ],
    },
    req,
    limit: 200,
  });

  const newStart = new Date(startTime).getTime();
  const newEnd = new Date(endTime).getTime();
  const conflict = sameDayConfirmed.some((doc) => {
    const s = new Date(doc.startTime).getTime();
    const e = new Date(doc.endTime).getTime();
    return newStart < e && s < newEnd;
  });

  if (conflict) {
    throw new APIError(
      "Dieser Zeitraum ist bereits mit einem anderen bestätigten Termin belegt. Bitte wähle eine andere Zeit oder lehne den überschneidenden Termin zuerst ab.",
      409,
      undefined,
      true,
    );
  }

  if (appointmentType === "online" && !data.linkedEvent && !originalDoc.linkedEvent) {
    const offer = (await req.payload.findByID({ collection: "offers", id: data.offer ?? originalDoc.offer, req })) as Offer;
    const event = (await req.payload.create({
      collection: "events",
      req,
      data: {
        title: offer.title,
        date,
        startTime,
        endTime,
        category: "sonstiges",
        isOnline: true, // Events' own beforeChange hook auto-generates the password.
        isPrivateBooking: true,
        bookingRequest: originalDoc.id,
      },
      // Created as a draft so it never appears in public /termine listings
      // (see lib/payload/content.ts) — it's still reachable via its direct
      // join link, which is exactly what a private 1:1 booking needs.
      draft: true,
    })) as Event;
    data.linkedEvent = event.id;
  }

  return data;
};

const notifyByEmail: CollectionAfterChangeHook = async ({ doc, previousDoc, operation, req }) => {
  try {
    const user = (doc.user && typeof doc.user === "object" ? doc.user : await req.payload.findByID({
      collection: "customers",
      id: doc.user,
      req,
    })) as Customer;
    const offer = (doc.offer && typeof doc.offer === "object" ? doc.offer : await req.payload.findByID({
      collection: "offers",
      id: doc.offer,
      req,
    })) as Offer;

    const serverUrl = process.env.NEXT_PUBLIC_SERVER_URL || "http://localhost:3000";
    const adminUrl = `${serverUrl}/admin/collections/booking-requests/${doc.id}`;
    const accountUrl = `${serverUrl}/konto/termine`;

    if (operation === "create") {
      await sendEmail(
        user.email,
        bookingRequestReceivedEmail({
          name: user.name,
          offerTitle: offer.title,
          dateLabel: fmtDate(doc.date),
          timeLabel: fmtTime(doc.startTime),
          appointmentTypeLabel: appointmentTypeLabel(doc.appointmentType),
        }),
      );
      await notifyAdmins(
        req,
        newBookingRequestAdminEmail({
          customerName: user.name,
          customerEmail: user.email,
          offerTitle: offer.title,
          dateLabel: fmtDate(doc.date),
          timeLabel: fmtTime(doc.startTime),
          appointmentTypeLabel: appointmentTypeLabel(doc.appointmentType),
          adminUrl,
        }),
      );
      return doc;
    }

    const statusChanged = previousDoc?.status !== doc.status;

    if (statusChanged && doc.status === "confirmed") {
      let online: { joinUrl: string; password: string } | undefined;
      let onsite: { address: string; mapsUrl: string } | undefined;

      if (doc.appointmentType === "online" && doc.linkedEvent) {
        const event = (typeof doc.linkedEvent === "object" ? doc.linkedEvent : await req.payload.findByID({
          collection: "events",
          id: doc.linkedEvent,
          req,
        })) as Event;
        online = {
          joinUrl: `${serverUrl}/termine/${event.slug}/beitreten`,
          password: event.meetingPassword || "—",
        };
      } else if (doc.appointmentType === "onsite") {
        const settings = await req.payload.findGlobal({ slug: "booking-settings", req });
        const addressParts = [settings.locationName, settings.street, [settings.postalCode, settings.city].filter(Boolean).join(" ")].filter(Boolean);
        const address = addressParts.join(", ");
        onsite = { address, mapsUrl: `https://www.google.com/maps/search/?api=1&query=${encodeURIComponent(address)}` };
      }

      await sendEmail(
        user.email,
        bookingConfirmedEmail({
          name: user.name,
          offerTitle: offer.title,
          dateLabel: fmtDate(doc.date),
          timeLabel: `${fmtTime(doc.startTime)} – ${fmtTime(doc.endTime)}`,
          appointmentTypeLabel: appointmentTypeLabel(doc.appointmentType),
          online,
          onsite,
        }),
      );
    } else if (statusChanged && doc.status === "rejected") {
      await sendEmail(
        user.email,
        bookingRejectedEmail({
          name: user.name,
          offerTitle: offer.title,
          dateLabel: fmtDate(doc.date),
          timeLabel: fmtTime(doc.startTime),
        }),
      );
    } else if (statusChanged && doc.status === "cancelled") {
      await notifyAdmins(
        req,
        bookingCancelledAdminEmail({
          customerName: user.name,
          offerTitle: offer.title,
          dateLabel: fmtDate(doc.date),
          timeLabel: fmtTime(doc.startTime),
          adminUrl,
        }),
      );
    }

    const proposedNew = doc.proposedAlternative?.date && doc.proposedAlternative.date !== previousDoc?.proposedAlternative?.date;
    if (proposedNew && doc.status === "pending") {
      await sendEmail(
        user.email,
        alternativeProposedEmail({
          name: user.name,
          offerTitle: offer.title,
          originalDateLabel: fmtDate(doc.date),
          originalTimeLabel: fmtTime(doc.startTime),
          altDateLabel: fmtDate(doc.proposedAlternative.date),
          altTimeLabel: fmtTime(doc.proposedAlternative.startTime),
          accountUrl,
        }),
      );
    }
  } catch (err) {
    // Email delivery must never break the booking write itself.
    req.payload.logger.error({ err, msg: "booking-requests notifyByEmail failed" });
  }

  return doc;
};

export const BookingRequests: CollectionConfig = {
  slug: "booking-requests",
  labels: {
    singular: "Buchungsanfrage",
    plural: "Buchungsanfragen",
  },
  admin: {
    useAsTitle: "id",
    defaultColumns: ["offer", "user", "date", "startTime", "status"],
    group: "Buchungen",
    description: "Terminanfragen von Nutzer:innen — bestätigen, ablehnen oder einen alternativen Termin vorschlagen, indem du die Felder unten änderst und speicherst.",
  },
  access: {
    // Customer-initiated writes always go through the vetted /api/booking/*
    // routes (Local API, elevated access, after the route verifies
    // ownership) — never directly through REST/GraphQL. This keeps a
    // customer from ever reading/writing another customer's booking, or
    // setting their own status to "confirmed" directly.
    create: isAdmin,
    read: ({ req }) => {
      if (req.user?.collection === "users") return true;
      if (req.user?.collection === "customers") return { user: { equals: req.user.id } };
      return false;
    },
    update: isAdmin,
    delete: isAdmin,
  },
  hooks: {
    beforeChange: [handleConfirmation],
    afterChange: [notifyByEmail],
  },
  fields: [
    {
      name: "user",
      type: "relationship",
      relationTo: "customers",
      label: "Nutzer:in",
      required: true,
      index: true,
    },
    {
      name: "offer",
      type: "relationship",
      relationTo: "offers",
      label: "Angebot",
      required: true,
    },
    {
      type: "row",
      fields: [
        {
          name: "date",
          type: "date",
          label: "Datum",
          required: true,
          admin: { date: { pickerAppearance: "dayOnly", displayFormat: "dd.MM.yyyy" }, width: "34%" },
        },
        {
          name: "startTime",
          type: "date",
          label: "Startzeit",
          required: true,
          admin: { date: { pickerAppearance: "timeOnly", displayFormat: "HH:mm" }, width: "33%" },
        },
        {
          name: "endTime",
          type: "date",
          label: "Endzeit",
          required: true,
          admin: { date: { pickerAppearance: "timeOnly", displayFormat: "HH:mm" }, width: "33%" },
        },
      ],
    },
    {
      name: "appointmentType",
      type: "select",
      label: "Terminart",
      required: true,
      defaultValue: "onsite",
      options: [...APPOINTMENT_TYPES],
    },
    {
      name: "status",
      type: "select",
      label: "Status",
      required: true,
      defaultValue: "pending",
      options: [...BOOKING_STATUSES],
      admin: {
        description: "Auf „Bestätigt“ setzen und speichern, um den Termin verbindlich zu machen (Konfliktprüfung läuft automatisch).",
      },
    },
    {
      name: "userMessage",
      type: "textarea",
      label: "Nachricht der Nutzerin/des Nutzers",
      admin: { readOnly: true },
    },
    {
      name: "internalNote",
      type: "textarea",
      label: "Interne Notiz",
      access: { read: isAdminFieldLevel, update: isAdminFieldLevel },
      admin: { description: "Nur für Anna sichtbar." },
    },
    {
      type: "collapsible",
      label: "Alternativer Termin",
      fields: [
        {
          type: "row",
          fields: [
            {
              name: "proposedAlternative",
              type: "group",
              label: "",
              fields: [
                {
                  type: "row",
                  fields: [
                    {
                      name: "date",
                      type: "date",
                      label: "Alternatives Datum",
                      admin: { date: { pickerAppearance: "dayOnly", displayFormat: "dd.MM.yyyy" }, width: "34%" },
                    },
                    {
                      name: "startTime",
                      type: "date",
                      label: "Alternative Startzeit",
                      admin: { date: { pickerAppearance: "timeOnly", displayFormat: "HH:mm" }, width: "33%" },
                    },
                    {
                      name: "endTime",
                      type: "date",
                      label: "Alternative Endzeit",
                      admin: { date: { pickerAppearance: "timeOnly", displayFormat: "HH:mm" }, width: "33%" },
                    },
                  ],
                },
              ],
            },
          ],
        },
      ],
    },
    {
      name: "linkedEvent",
      type: "relationship",
      relationTo: "events",
      label: "Verknüpfter Video-Termin",
      admin: { position: "sidebar", readOnly: true },
    },
  ],
};