"use client";

import { CalendarPlusIcon, CheckIcon, CircleAlertIcon, CopyIcon, RefreshCwIcon } from "lucide-react";
import { useState } from "react";
import { Button } from "@/components/ui/button";
import {
  Dialog,
  DialogContent,
  DialogDescription,
  DialogFooter,
  DialogHeader,
  DialogTitle,
  DialogTrigger,
} from "@/components/ui/dialog";
import { Skeleton } from "@/components/ui/skeleton";
import { goToAdminLogin } from "@/lib/admin-auth";
import { api } from "@/lib/api";
import { describeApiError, isSessionExpired } from "@/lib/api-errors";
import { CALENDARS, type CalendarSlug } from "@/lib/calendars";
import { toGoogleCalendar, toWebcal } from "@/lib/public-calendar";
import { cn } from "@/lib/utils";

type Subscription = { calendar: CalendarSlug; icalUrl: string };
type Load = { status: "idle" } | { status: "loading" } | { status: "ready"; subscriptions: Subscription[] } | { status: "error"; message: string };

/**
 * Subscription links for every calendar, for the editor's own phone or to
 * pass on to members. The URLs of the internal calendars carry their shared
 * password, which is why they come from the API (GET
 * /calendar/events/subscriptions, editors only) rather than being built here -
 * the browser has no other way to know the passwords.
 *
 * Fetched each time the dialog opens, so a rotated password shows up at once.
 */
export function SubscriptionsDialog() {
  const [load, setLoad] = useState<Load>({ status: "idle" });
  const [copied, setCopied] = useState<CalendarSlug | null>(null);

  const fetchLinks = async () => {
    setLoad({ status: "loading" });
    try {
      setLoad({ status: "ready", subscriptions: await api.getSubscriptions() });
    } catch (e) {
      if (isSessionExpired(e)) {
        goToAdminLogin();
        return;
      }
      setLoad({ status: "error", message: describeApiError(e) });
    }
  };

  const copy = async (subscription: Subscription) => {
    try {
      await navigator.clipboard.writeText(subscription.icalUrl);
      setCopied(subscription.calendar);
      setTimeout(() => setCopied((current) => (current === subscription.calendar ? null : current)), 2000);
    } catch {
      // No clipboard access: the URL is selectable in the dialog instead.
      setCopied(null);
    }
  };

  return (
    <Dialog
      onOpenChange={(open) => {
        if (open) void fetchLinks();
      }}
    >
      <DialogTrigger render={<Button variant="ghost" size="sm" aria-label="Abonnieren" title="Kalender abonnieren" />}>
        <CalendarPlusIcon />
        <span className="hidden sm:inline">Abonnieren</span>
      </DialogTrigger>
      {/* minmax(0,1fr): an implicit grid column grows to its longest unbreakable content - here a
          full URL - so `truncate` on the URL never kicked in and the dialog's content overflowed. */}
      <DialogContent className="max-h-[90dvh] grid-cols-[minmax(0,1fr)] overflow-y-auto sm:max-w-lg">
        <DialogHeader>
          <DialogTitle>Kalender abonnieren</DialogTitle>
          <DialogDescription>
            Mit diesen Links erscheinen die Termine automatisch in einer Kalender-App. Die Links der internen Kalender
            enthalten das jeweilige Kalender-Passwort – bitte nur an Mitglieder weitergeben.
          </DialogDescription>
        </DialogHeader>

        {load.status === "loading" || load.status === "idle" ? (
          <div className="flex flex-col gap-2" aria-busy="true" aria-label="Links werden geladen">
            {CALENDARS.map((c) => (
              <Skeleton key={c.id} className="h-16 w-full" />
            ))}
          </div>
        ) : load.status === "error" ? (
          <div role="alert" className="flex flex-col items-start gap-3 rounded-lg bg-destructive/10 p-3 text-sm text-destructive">
            <p className="flex gap-2">
              <CircleAlertIcon aria-hidden className="mt-0.5 size-4 shrink-0" />
              Die Links konnten nicht geladen werden: {load.message}
            </p>
            <Button variant="outline" size="sm" onClick={() => void fetchLinks()}>
              <RefreshCwIcon />
              Erneut versuchen
            </Button>
          </div>
        ) : (
          <ul className="divide-y rounded-xl border">
            {CALENDARS.map((calendar) => {
              const subscription = load.subscriptions.find((s) => s.calendar === calendar.slug);
              return (
                <li key={calendar.id} className="flex flex-col gap-2 p-3">
                  <span className="flex items-center gap-2 text-sm font-medium">
                    <span aria-hidden className={cn("size-2.5 rounded-full", calendar.dotClass)} />
                    {calendar.label}
                  </span>
                  {subscription ? (
                    <>
                      <code className="block truncate rounded-md bg-muted px-2 py-1 text-xs text-muted-foreground select-all">
                        {subscription.icalUrl}
                      </code>
                      <div className="flex flex-wrap gap-2">
                        <Button variant="outline" size="xs" render={<a href={toWebcal(subscription.icalUrl)} />}>
                          Apple Kalender
                        </Button>
                        <Button
                          variant="outline"
                          size="xs"
                          render={<a href={toGoogleCalendar(subscription.icalUrl)} target="_blank" rel="noopener noreferrer" />}
                        >
                          Google Kalender
                        </Button>
                        <Button variant="outline" size="xs" onClick={() => void copy(subscription)}>
                          {copied === calendar.slug ? <CheckIcon /> : <CopyIcon />}
                          {copied === calendar.slug ? "Kopiert" : "Link kopieren"}
                        </Button>
                      </div>
                    </>
                  ) : (
                    <p className="text-xs text-muted-foreground">
                      Für diesen Kalender ist auf dem Server kein Passwort eingerichtet, daher gibt es keinen Abo-Link.
                    </p>
                  )}
                </li>
              );
            })}
          </ul>
        )}

        <p className="text-xs text-muted-foreground">
          Chor und Geburtstage teilen sich ein Passwort: Wird es geändert, müssen beide neu abonniert werden.
        </p>
        <DialogFooter showCloseButton />
      </DialogContent>
    </Dialog>
  );
}