"use client";

import { CalendarX2Icon, SearchXIcon } from "lucide-react";
import { Fragment } from "react";
import { EventListItem } from "@/components/admin/EventListItem";
import { Button } from "@/components/ui/button";
import { Skeleton } from "@/components/ui/skeleton";
import { formatDay } from "@/lib/dates";
import { groupByMonth, type Range, type Sort } from "@/lib/filter";
import type { CalendarEvent } from "@/lib/types";

/**
 * The list itself: grouped by month when sorted by start (what people scan
 * for), flat when sorted by creation date (where month headings would repeat
 * and mislead).
 */
export function EventList({
  events,
  now,
  sort,
  range,
  query,
  loading,
  noCalendars,
  publishingId,
  todayMarker,
  onOpen,
  onPublish,
  onClearQuery,
}: {
  events: CalendarEvent[];
  now: Date;
  sort: Sort;
  range: Range;
  query: string;
  loading: boolean;
  noCalendars: boolean;
  publishingId: number | null;
  /** Index into `events` to show the "Heute" marker in front of (`events.length` = after the last); null for none. */
  todayMarker: number | null;
  onOpen?: (event: CalendarEvent) => void;
  onPublish: (event: CalendarEvent) => void;
  onClearQuery: () => void;
}) {
  if (noCalendars) {
    return <Empty icon={<CalendarX2Icon />} title="Kein Kalender ausgewählt" text="Wähle oben mindestens einen Kalender." />;
  }
  if (events.length === 0 && loading) {
    return <ListSkeleton />;
  }
  if (events.length === 0) {
    if (query.trim() !== "") {
      return (
        <Empty
          icon={<SearchXIcon />}
          title={`Keine Termine für „${query.trim()}“`}
          text="Die Suche berücksichtigt Titel und Ort."
          action={
            <Button variant="outline" size="sm" onClick={onClearQuery}>
              Suche leeren
            </Button>
          }
        />
      );
    }
    const text = { future: "Keine kommenden Termine.", past: "Keine vergangenen Termine.", all: "Noch keine Termine." }[range];
    return <Empty icon={<CalendarX2Icon />} title={text} text="In den ausgewählten Kalendern ist nichts eingetragen." />;
  }

  const markerBefore = todayMarker !== null && todayMarker < events.length ? events[todayMarker].eventId : null;
  const marker = <TodayMarker now={now} />;

  const item = (event: CalendarEvent) => (
    <Fragment key={event.eventId}>
      {event.eventId === markerBefore && marker}
      <EventListItem
        event={event}
        now={now}
        publishing={publishingId === event.eventId}
        onOpen={onOpen}
        onPublish={onPublish}
      />
    </Fragment>
  );

  if (sort.startsWith("created")) {
    return <ul className="divide-y overflow-hidden rounded-xl border bg-card">{events.map(item)}</ul>;
  }

  return (
    <div className="flex flex-col gap-5">
      {groupByMonth(events, now).map((group, i) => (
        <section key={`${group.key}-${i}`} aria-label={group.label}>
          <h2 className="sticky top-[calc(3.5rem+env(safe-area-inset-top))] z-10 -mx-1 bg-background/95 px-1 py-2 text-sm font-semibold text-muted-foreground backdrop-blur">
            {group.label}
          </h2>
          <ul className="divide-y overflow-hidden rounded-xl border bg-card">{group.events.map(item)}</ul>
        </section>
      ))}
      {todayMarker === events.length && <ul className="overflow-hidden rounded-xl border">{marker}</ul>}
    </div>
  );
}

/** Where today falls in the list. The page scrolls it into view in the "Alle" range. */
function TodayMarker({ now }: { now: Date }) {
  return (
    <li
      id="heute"
      className="flex items-center gap-2 bg-primary/[0.05] px-4 py-1.5 text-xs font-semibold text-primary"
    >
      <span aria-hidden className="size-1.5 rounded-full bg-primary" />
      Heute · {formatDay(now)}
    </li>
  );
}

function Empty({ icon, title, text, action }: { icon: React.ReactNode; title: string; text: string; action?: React.ReactNode }) {
  return (
    <div className="flex flex-col items-center gap-2 rounded-xl border border-dashed px-6 py-12 text-center">
      <div className="text-muted-foreground [&_svg]:size-8">{icon}</div>
      <p className="font-medium">{title}</p>
      <p className="text-sm text-muted-foreground">{text}</p>
      {action && <div className="mt-2">{action}</div>}
    </div>
  );
}

function ListSkeleton() {
  return (
    <div className="flex flex-col gap-3" aria-busy="true" aria-label="Termine werden geladen">
      <Skeleton className="h-5 w-32" />
      <div className="divide-y rounded-xl border">
        {Array.from({ length: 5 }, (_, i) => (
          <div key={i} className="flex gap-4 p-4">
            <Skeleton className="h-12 w-11" />
            <div className="flex flex-1 flex-col gap-2">
              <Skeleton className="h-4 w-2/3" />
              <Skeleton className="h-3 w-1/3" />
              <Skeleton className="h-5 w-24" />
            </div>
          </div>
        ))}
      </div>
    </div>
  );
}