'use client';

import { useTranslations } from 'next-intl';
import { useTheme } from 'next-themes';
import { type CSSProperties, useCallback, useEffect, useRef, useState } from 'react';
import { updateDashboardBackgroundAction } from '@/lib/auth-actions';
import {
  BACKGROUND_PRESETS,
  type DashboardBackground,
  NO_BACKGROUND,
  presetBackground,
  takeLegacyDashboardBackground,
} from '@/lib/dashboard-background';
import {
  type DashboardImageMeta,
  dashboardImageSrc,
  fetchDashboardImages,
  uploadDashboardImage,
} from '@/lib/dashboard-images-api';
import { useAuthStore } from '@/lib/stores/auth-store';

/** Schreibt die Wahl in den Auth-Store, sofern noch derselbe Benutzer angemeldet ist. */
function setStoredBackground(userId: string, value: DashboardBackground | null) {
  const current = useAuthStore.getState().user;
  if (!current || current.id !== userId) return;
  useAuthStore.getState().setUser({ ...current, dashboardBackground: value });
}

/**
 * Wahl des Hintergrunds fuer den angemeldeten Benutzer (quick-260928-ujj).
 *
 * Gelesen aus dem Auth-Store (Sitzungsantwort, `null` = nie gewaehlt =
 * kein Hintergrund). `choose()` setzt den Store sofort und speichert ueber
 * die Server-Aktion; schlaegt das fehl, kommt der vorige Wert zurueck.
 * Ist der Server-Wert `null` und liegt noch eine alte localStorage-Wahl vor,
 * wird sie genau einmal je Benutzerkennung uebernommen.
 */
export function useDashboardBackground() {
  const user = useAuthStore((s) => s.user);
  const userId = user?.id ?? null;
  const stored = user?.dashboardBackground ?? null;
  const background = stored ?? NO_BACKGROUND;
  const migratedFor = useRef<string | null>(null);

  const save = useCallback(
    (id: string, value: DashboardBackground, previous: DashboardBackground | null) => {
      setStoredBackground(id, value);
      const revert = () => setStoredBackground(id, previous);
      updateDashboardBackgroundAction(value)
        .then((result) => {
          if (!result.success) revert();
        })
        .catch(revert);
    },
    [],
  );

  const choose = useCallback(
    (value: DashboardBackground) => {
      if (!userId) return;
      save(userId, value, stored);
    },
    [userId, stored, save],
  );

  useEffect(() => {
    if (!userId || migratedFor.current === userId) return;
    migratedFor.current = userId;
    // Auch bei gesetztem Server-Wert auslesen: der alte Schluessel wird so
    // aufgeraeumt, uebernommen wird aber nur, wenn noch nie gewaehlt wurde.
    const legacy = takeLegacyDashboardBackground(userId);
    if (legacy && stored === null) save(userId, legacy, null);
  }, [userId, stored, save]);

  return { background, choose };
}

/** CSS fuer eine Wahl; Flaechenfarbe oder Bild, jeweils bildschirmfuellend. */
function backgroundStyle(value: DashboardBackground, dark: boolean): CSSProperties | null {
  if (value.kind === 'none') return null;
  if (value.kind === 'image') {
    return {
      backgroundImage: `url("${dashboardImageSrc(value.imageId)}")`,
      backgroundSize: 'cover',
      backgroundPosition: 'center',
    };
  }
  const css = presetBackground(value.id, dark);
  if (!css) return null;
  return css.startsWith('url(')
    ? { backgroundImage: css, backgroundSize: 'cover', backgroundPosition: 'center' }
    : { backgroundColor: css };
}

/**
 * Bildschirmfuellende Hintergrundebene hinter dem Dashboard. Liegt fest
 * unter Kopfzeile und Seitenleiste (beide haben eigene Flaechen). Im dunklen
 * Erscheinungsbild werden eigene Bilder abgedunkelt — so bleibt der Text auf
 * den durchscheinenden Kacheln auch bei einem sehr hellen Foto lesbar.
 */
export function DashboardBackdrop({ background }: { background: DashboardBackground }) {
  const { resolvedTheme } = useTheme();
  const dark = resolvedTheme === 'dark';
  const style = backgroundStyle(background, dark);
  if (!style) return null;
  return (
    <div
      aria-hidden="true"
      data-testid="dashboard-backdrop"
      data-background={background.kind === 'preset' ? background.id : background.kind}
      className={`pointer-events-none fixed inset-0 z-0 ${
        background.kind === 'image' ? 'dark:brightness-[0.55]' : ''
      }`}
      style={style}
    />
  );
}

interface BackgroundPickerProps {
  value: DashboardBackground;
  onChange: (value: DashboardBackground) => void;
}

function sameChoice(a: DashboardBackground, b: DashboardBackground): boolean {
  if (a.kind !== b.kind) return false;
  if (a.kind === 'preset' && b.kind === 'preset') return a.id === b.id;
  if (a.kind === 'image' && b.kind === 'image') return a.imageId === b.imageId;
  return true;
}

/**
 * Knopf „Hintergrund“ (nur im Bearbeitungsmodus) mit einem kleinen Fenster:
 * Vorschaubilder fuer „Keiner“, die eingebauten Hintergruende, die eigenen
 * Bilder und eine Kachel zum Hochladen eines neuen Bildes.
 */
export function BackgroundPicker({ value, onChange }: BackgroundPickerProps) {
  const t = useTranslations('dashboard.background');
  const { resolvedTheme } = useTheme();
  const dark = resolvedTheme === 'dark';
  const [open, setOpen] = useState(false);
  const [images, setImages] = useState<DashboardImageMeta[] | null>(null);
  const [uploading, setUploading] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const rootRef = useRef<HTMLDivElement>(null);
  const fileRef = useRef<HTMLInputElement>(null);

  useEffect(() => {
    if (!open || images !== null) return;
    fetchDashboardImages()
      .then(setImages)
      .catch(() => setImages([]));
  }, [open, images]);

  useEffect(() => {
    if (!open) return;
    function onPointer(e: MouseEvent) {
      if (rootRef.current && !rootRef.current.contains(e.target as Node)) setOpen(false);
    }
    function onKey(e: KeyboardEvent) {
      if (e.key === 'Escape') setOpen(false);
    }
    document.addEventListener('mousedown', onPointer);
    document.addEventListener('keydown', onKey);
    return () => {
      document.removeEventListener('mousedown', onPointer);
      document.removeEventListener('keydown', onKey);
    };
  }, [open]);

  async function handleUpload(file: File | undefined) {
    if (!file) return;
    setError(null);
    setUploading(true);
    try {
      const meta = await uploadDashboardImage(file);
      setImages((prev) => [meta, ...(prev ?? [])]);
      onChange({ kind: 'image', imageId: meta.id });
    } catch (e) {
      setError(e instanceof Error ? e.message : t('uploadError'));
    } finally {
      setUploading(false);
      if (fileRef.current) fileRef.current.value = '';
    }
  }

  const option = (
    key: string,
    label: string,
    choice: DashboardBackground,
    preview: CSSProperties,
    content?: React.ReactNode,
  ) => {
    const selected = sameChoice(value, choice);
    return (
      <li key={key}>
        <button
          type="button"
          onClick={() => onChange(choice)}
          aria-pressed={selected}
          title={label}
          className="group flex w-full flex-col items-stretch gap-1 rounded-md text-left focus-visible:outline-none"
        >
          <span
            className={`flex h-12 items-center justify-center overflow-hidden rounded-md border text-muted-foreground transition-shadow group-focus-visible:ring-2 group-focus-visible:ring-ring ${
              selected
                ? 'border-transparent ring-2 ring-foreground'
                : 'border-border group-hover:border-input-strong'
            }`}
            style={preview}
          >
            {content}
          </span>
          <span
            className={`truncate text-xs ${selected ? 'font-semibold text-foreground' : 'text-muted-foreground'}`}
          >
            {label}
          </span>
        </button>
      </li>
    );
  };

  return (
    <div ref={rootRef} className="relative">
      <button
        type="button"
        onClick={() => setOpen((v) => !v)}
        aria-expanded={open}
        aria-haspopup="dialog"
        aria-label={t('button')}
        title={t('button')}
        className="btn btn-appbar"
      >
        <svg
          aria-hidden="true"
          xmlns="http://www.w3.org/2000/svg"
          width="16"
          height="16"
          viewBox="0 0 24 24"
          fill="none"
          stroke="currentColor"
          strokeWidth="2"
          strokeLinecap="round"
          strokeLinejoin="round"
        >
          <rect x="3" y="3" width="18" height="18" rx="2" />
          <circle cx="9" cy="9" r="2" />
          <path d="m21 15-3.1-3.1a2 2 0 0 0-2.8 0L6 21" />
        </svg>
        {/* In der App-Leiste ist der Platz knapp: Beschriftung erst ab lg. */}
        <span className="hidden lg:inline">{t('button')}</span>
      </button>

      {open && (
        <div
          role="dialog"
          aria-label={t('title')}
          className="absolute right-0 top-full z-30 mt-2 w-[min(22rem,calc(100vw-2rem))] rounded-lg bg-card p-4 text-card-foreground shadow-xl dark:border dark:border-border"
        >
          <h2 className="text-sm font-semibold">{t('title')}</h2>
          <p className="mt-0.5 text-xs text-muted-foreground">{t('hint')}</p>

          <h3 className="mt-4 text-xs font-semibold text-muted-foreground">{t('builtIn')}</h3>
          <ul className="mt-2 grid grid-cols-3 gap-3">
            {option(
              'none',
              t('none'),
              NO_BACKGROUND,
              { backgroundColor: 'var(--background)' },
              <svg
                aria-hidden="true"
                xmlns="http://www.w3.org/2000/svg"
                width="18"
                height="18"
                viewBox="0 0 24 24"
                fill="none"
                stroke="currentColor"
                strokeWidth="1.75"
                strokeLinecap="round"
              >
                <circle cx="12" cy="12" r="8" />
                <path d="m6.5 17.5 11-11" />
              </svg>,
            )}
            {BACKGROUND_PRESETS.filter((preset) => !dark || preset.dark !== null).map((preset) => {
              const css = (dark ? preset.dark : preset.light) ?? preset.light;
              return option(
                preset.id,
                t(`presets.${preset.labelKey}`),
                { kind: 'preset', id: preset.id },
                css.startsWith('url(')
                  ? { backgroundImage: css, backgroundSize: 'cover', backgroundPosition: 'center' }
                  : { backgroundColor: css },
              );
            })}
          </ul>

          <h3 className="mt-4 text-xs font-semibold text-muted-foreground">{t('ownImages')}</h3>
          <ul className="mt-2 grid max-h-40 grid-cols-3 gap-3 overflow-y-auto p-0.5">
            {(images ?? []).map((image) =>
              option(
                image.id,
                image.originalName,
                { kind: 'image', imageId: image.id },
                {
                  backgroundImage: `url("${dashboardImageSrc(image.id)}")`,
                  backgroundSize: 'cover',
                  backgroundPosition: 'center',
                },
              ),
            )}
            <li>
              <button
                type="button"
                onClick={() => fileRef.current?.click()}
                disabled={uploading}
                className="group flex w-full flex-col items-stretch gap-1 rounded-md text-left focus-visible:outline-none"
              >
                <span className="flex h-12 items-center justify-center rounded-md border border-dashed border-input-strong text-muted-foreground transition-colors group-hover:bg-muted group-hover:text-foreground group-focus-visible:ring-2 group-focus-visible:ring-ring">
                  {uploading ? (
                    <span className="inline-block h-4 w-4 animate-spin rounded-full border-2 border-current border-t-transparent" />
                  ) : (
                    <svg
                      aria-hidden="true"
                      xmlns="http://www.w3.org/2000/svg"
                      width="18"
                      height="18"
                      viewBox="0 0 24 24"
                      fill="none"
                      stroke="currentColor"
                      strokeWidth="2"
                      strokeLinecap="round"
                    >
                      <path d="M12 5v14" />
                      <path d="M5 12h14" />
                    </svg>
                  )}
                </span>
                <span className="truncate text-xs text-muted-foreground">{t('upload')}</span>
              </button>
            </li>
          </ul>
          <input
            ref={fileRef}
            type="file"
            accept="image/png,image/jpeg,image/webp,image/gif"
            className="hidden"
            onChange={(e) => handleUpload(e.target.files?.[0])}
          />
          {images !== null && images.length === 0 && (
            <p className="mt-2 text-xs text-muted-foreground">{t('noImages')}</p>
          )}
          {error && (
            <p role="alert" className="mt-2 text-xs text-destructive">
              {error}
            </p>
          )}
        </div>
      )}
    </div>
  );
}