import { randomUUID } from "node:crypto";
import { APIError } from "payload";
import type { CollectionAfterChangeHook, CollectionBeforeChangeHook, CollectionConfig, Where } from "payload";
import { isAdmin, isAdminFieldLevel } from "@/access";
import { combineDateAndTime } from "@/lib/meeting/status";
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";
import { berlinDateKey, formatBerlinDate, formatBerlinTime } from "@/lib/calendar/timezone";

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 berlinDateKey(new Date(iso));
}

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

function fmtTime(iso: string): string {
  return formatBerlinTime(new Date(iso), { 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)));
}

// Normalize Payload time-only inputs before conflict checks and synchronize
// the private meeting whenever a booking is moved, cancelled or reactivated.
export const handleConfirmation: CollectionBeforeChangeHook = async ({ data, originalDoc, req }) => {
  const status = data.status ?? originalDoc?.status ?? "pending";
  const date = data.date ?? originalDoc?.date;
  const startTime = data.startTime ?? originalDoc?.startTime;
  const endTime = data.endTime ?? originalDoc?.endTime;
  const appointmentType = data.appointmentType ?? originalDoc?.appointmentType;
  if (!date || !startTime || !endTime) return data;
  const start = combineDateAndTime(date, startTime);
  const end = combineDateAndTime(date, endTime);
  if (!Number.isFinite(start.getTime()) || !Number.isFinite(end.getTime()) || end <= start) {
    throw new APIError("Das Ende muss nach dem Beginn am selben Tag liegen.", 400, undefined, true);
  }
  data.date = start.toISOString();
  data.startTime = start.toISOString();
  data.endTime = end.toISOString();

  const alternative = data.proposedAlternative;
  if (alternative && (alternative.date || alternative.startTime || alternative.endTime)) {
    if (!alternative.date || !alternative.startTime || !alternative.endTime) {
      throw new APIError("Bitte den alternativen Termin vollständig angeben.", 400, undefined, true);
    }
    const altStart = combineDateAndTime(alternative.date, alternative.startTime);
    const altEnd = combineDateAndTime(alternative.date, alternative.endTime);
    if (!Number.isFinite(altStart.getTime()) || !Number.isFinite(altEnd.getTime()) || altEnd <= altStart) {
      throw new APIError("Der alternative Zeitraum ist ungültig.", 400, undefined, true);
    }
    data.proposedAlternative = { date: altStart.toISOString(), startTime: altStart.toISOString(), endTime: altEnd.toISOString() };
  }

  if (status === "confirmed") {
    await acquireBookingDayLock(req, dateKey(data.date));
    const conflictClauses: Where[] = [
      { status: { equals: "confirmed" } },
      { startTime: { less_than: data.endTime } },
      { endTime: { greater_than: data.startTime } },
    ];
    if (originalDoc?.id) conflictClauses.push({ id: { not_equals: originalDoc.id } });
    const { totalDocs } = await req.payload.count({ collection: "booking-requests", where: { and: conflictClauses }, req });
    if (totalDocs) throw new APIError("Dieser Zeitraum ist bereits mit einem bestätigten Termin belegt.", 409, undefined, true);
  }

  const linked = data.linkedEvent ?? originalDoc?.linkedEvent;
  const linkedId = typeof linked === "object" ? linked?.id : linked;
  if (linkedId) {
    const existing = await req.payload.findByID({ collection: "events", id: linkedId, depth: 0, req });
    if (existing.isPrivateBooking) {
      const isOnline = status === "confirmed" && appointmentType === "online";
      if (existing.date !== data.date || existing.startTime !== data.startTime || existing.endTime !== data.endTime || existing.isOnline !== isOnline) {
        await req.payload.update({ collection: "events", id: existing.id, req, data: {
          date: data.date, startTime: data.startTime, endTime: data.endTime, isOnline,
        } });
      }
    }
  } else if (status === "confirmed" && appointmentType === "online") {
    const relatedOffer = data.offer ?? originalDoc?.offer;
    const offer = await req.payload.findByID({ collection: "offers", id: typeof relatedOffer === "object" ? relatedOffer.id : relatedOffer, req });
    const event = await req.payload.create({ collection: "events", req, draft: true, data: {
      title: offer.title,
      slug: `buchung-${randomUUID()}`,
      date: data.date, startTime: data.startTime, endTime: data.endTime,
      category: "sonstiges", isOnline: true, isPrivateBooking: true,
      ...(originalDoc?.id ? { bookingRequest: originalDoc.id } : {}),
    } });
    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`;

    // A brand-new request (the normal customer-initiated path) always gets
    // the "received" + admin-notification pair. A booking Anna creates
    // manually as already-confirmed/rejected (operation 26: manual bookings)
    // skips this and falls through to the same status-based emails below.
    if (operation === "create" && doc.status === "pending") {
      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 = operation === "create" || previousDoc?.status !== doc.status;

    const scheduleChanged = previousDoc && ["date", "startTime", "endTime", "appointmentType"].some((field) => doc[field] !== previousDoc[field]);
    if ((statusChanged || scheduleChanged) && 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 && JSON.stringify(doc.proposedAlternative) !== JSON.stringify(previousDoc?.proposedAlternative);
    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 Nutzern — 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 req.user.role === "admin";
      if (req.user?.collection === "customers") return { user: { equals: req.user.id } };
      return false;
    },
    update: isAdmin,
    delete: isAdmin,
  },
  hooks: {
    beforeOperation: [async ({ args, operation, req }) => {
      if (operation === "create" || operation === "update" || operation === "delete") {
        await acquireBookingDayLock(req, "booking-calendar");
      }
      return args;
    }],
    beforeChange: [handleConfirmation],
    afterChange: [notifyByEmail],
    afterDelete: [async ({ doc, req }) => {
      const id = typeof doc.linkedEvent === "object" ? doc.linkedEvent?.id : doc.linkedEvent;
      if (id) await req.payload.update({ collection: "events", id, req, data: { isOnline: false } });
      return doc;
    }],
  },
  fields: [
    {
      name: "user",
      type: "relationship",
      relationTo: "customers",
      label: "Nutzer",
      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 },
    },
  ],
};