import fs from 'node:fs';
import path from 'node:path';
import { env } from '../env';
import { resolveAuthSecret } from '../secret';
import { resolveSiteUrl } from '../siteUrl';
import { getInstallCredentials, installFilePath } from '../install';
import { loadYaml, clearYamlCache, validateUuid } from './parser';
import { resolveTheme, VALID_LAYOUTS, DEFAULT_PRESET } from './theme';
import { ALBUM_SORT_MODES, isAlbumSortMode, type AlbumSortMode } from '../albumSort';
import { LOCATION_PRECISIONS, isLocationPrecision, type LocationPrecision } from '../mapPrecision';
import {
  slugify,
  findAlbumSlugCollisions,
  resolveExifDisplay,
  resolveColorMode,
  clamp,
  PHOTO_GRID_COLUMNS_MIN,
  PHOTO_GRID_COLUMNS_MAX,
  PHOTO_GRID_GAP_MAX,
  AppConfig,
  AlbumEntryObject,
  SubpageConfig,
  SubpageSectionConfig,
  SubpageObjectValue,
  GalleryYaml,
  SettingsYaml,
  GridConfig,
  LegalConfig,
  ContactConfig,
  CONTACT_RETENTION_DEFAULT,
  CONTACT_RETENTION_MAX,
  isHttpUrl,
  isPageRef,
  type GallerySubpageYaml,
} from './schema';
import { isValidSlug } from '../journal';
import { getDictionary, resolveLocale } from '../i18n';
import type { NavEntry } from '../pages';

export * from './schema';
export * from './theme';

/** The last derived config and the inputs it was derived from; see getConfig(). */
let derived: { inputs: string; config: AppConfig } | null = null;

/** Invalidate the cached YAML so the next getConfig() call re-parses the files. */
export function invalidateConfigCache(): void {
  clearYamlCache();
  derived = null;
}

/**
 * getConfig(), but returns null instead of throwing on a gallery.yaml that
 * cannot be derived.
 *
 * getConfig() throws for three shapes the admin page builder is able to write:
 * a gallery with neither albums nor subpages, a subpage with no name, and a
 * subpage with neither albums nor sections. A throw inside a *layout* is not
 * caught by app/error.tsx — that needs a global-error boundary — so the site
 * and /admin would go down together, locking the user out of the only tool that
 * can undo the save. That is issue #326's failure mode reached through an
 * invalid config rather than a missing one.
 *
 * Callers should treat null exactly like `needsSetup`: show the setup screen,
 * and keep /admin reachable.
 */
export function getConfigOrNull(): AppConfig | null {
  try {
    return getConfig();
  } catch (error) {
    console.error(
      '[Folio] content/gallery.yaml could not be loaded — serving the setup screen. ' +
        'Fix the file or restore a backup from content/.backups/:',
      error,
    );
    return null;
  }
}

interface RawGridOverrides {
  columns?: number;
  gap?: number;
  aspectRatio?: string;
  layout?: string;
}

/**
 * Converts raw YAML grid overrides into a typed partial GridConfig.
 *
 * `columns` and `gap` are clamped here, not left for the renderer: a subpage
 * or album override reaches `--grid-columns` unclamped (app/[...path]/page.tsx),
 * so `columns: -1` produced an invalid `repeat(-1, 1fr)` and collapsed the
 * whole grid to one column with no error anywhere (#633). The cover grid had
 * this already (buildCoverGridVars); this is the same treatment for the photo
 * grid it was missing from.
 */
function parseGridOverrides(raw: RawGridOverrides): Partial<GridConfig> {
  return {
    ...(raw.columns != null
      ? { columns: clamp(raw.columns, PHOTO_GRID_COLUMNS_MIN, PHOTO_GRID_COLUMNS_MAX) }
      : {}),
    ...(raw.gap != null ? { gap: clamp(raw.gap, 0, PHOTO_GRID_GAP_MAX) } : {}),
    ...(raw.aspectRatio != null ? { aspectRatio: raw.aspectRatio } : {}),
    ...(raw.layout != null
      ? {
          layout: (VALID_LAYOUTS.includes(raw.layout)
            ? raw.layout
            : 'masonry') as GridConfig['layout'],
        }
      : {}),
  };
}

/** Converts raw YAML grid overrides into a typed partial GridConfig. */
export function buildSubpageGrid(
  raw?: RawGridOverrides,
): { grid: Partial<GridConfig> } | Record<string, never> {
  if (!raw) return {};
  return { grid: parseGridOverrides(raw) };
}

/**
 * The two grids a subpage can override, as one spread-able object.
 *
 * `grid` sizes the photos inside its albums, `coverGrid` the album-cover tiles
 * on the page itself. They were a single key until #523, where the admin field
 * labelled "Album Cover Grid" turned out to retune every photo grid on the page
 * as well. A gallery.yaml written before the split has no `coverGrid`, so the
 * covers fall back to `grid` and such a page renders exactly as it did.
 */
function buildSubpageGrids(
  grid?: RawGridOverrides,
  coverGrid?: RawGridOverrides,
): { grid?: Partial<GridConfig>; coverGrid?: Partial<GridConfig> } {
  const resolved = coverGrid ?? grid;
  return {
    ...buildSubpageGrid(grid),
    ...(resolved ? { coverGrid: parseGridOverrides(resolved) } : {}),
  };
}

/**
 * Whether client proofing is on for a page.
 *
 * Precedence is subpage → global, the same shape `buildSubpageGrid` gives the
 * grid: a subpage's own `proofing:` wins in either direction, and a page
 * reached without one follows `proofing.enabled` from settings.yaml. `??`
 * rather than `||` is load-bearing — `proofing: false` on a subpage has to
 * override a global `true`, which `||` would discard.
 *
 * Photo essays deliberately do not use this: a published story is not an album
 * handover, so it requires an explicit `proofing: true` and ignores the global
 * default. That exception lives at its call site in app/[...path]/page.tsx.
 */
export function resolveProofing(
  subpage: { proofing?: boolean } | undefined,
  globalEnabled: boolean,
): boolean {
  return subpage?.proofing ?? globalEnabled;
}

/**
 * The recipient of the proofing dialog's "email to photographer" (#736):
 * `proofing.email` when set, else the footer contact email. The first
 * non-empty value, trimmed — an address saved as only whitespace is not
 * configured. Undefined means neither is set, and the dialog hides the button
 * rather than opening a compose with an empty To:.
 */
export function resolveProofingEmail(
  proofingEmail?: string,
  footerEmail?: string,
): string | undefined {
  return (proofingEmail ?? '').trim() || (footerEmail ?? '').trim() || undefined;
}

/**
 * EXPERIMENTAL: keep only nav links that are safe to render as header <a>
 * tags. Non-http(s) schemes (javascript:, data:) and incomplete entries are
 * dropped with a warning rather than throwing — a bad external link should
 * not take the site down.
 */
export function sanitizeNavLinks(
  raw?: Array<{ label?: string; url?: string }>,
): Array<{ label: string; url: string }> {
  if (!raw) return [];
  const links: Array<{ label: string; url: string }> = [];
  for (const entry of raw) {
    const label = entry.label?.trim();
    const url = entry.url?.trim();
    if (!label || !url || !/^https?:\/\//i.test(url)) {
      console.warn(
        `[Folio] settings.yaml navLinks: dropping entry ${JSON.stringify(entry)} — ` +
          'label and an http(s) url are required.',
      );
      continue;
    }
    links.push({ label, url });
  }
  return links;
}

/**
 * The `legal:` block of settings.yaml, as the Impressum page renders it.
 *
 * `contactUrl` ends up in an `href`, so it gets the same rule as navLinks:
 * anything that is not http(s) is dropped with a warning, which keeps a
 * `javascript:` URL in hand-edited YAML off the page without taking it down.
 * Empty strings become undefined so the page can test fields with `&&`.
 */
export function resolveLegal(raw?: Partial<LegalConfig>): LegalConfig {
  const opt = (value?: string) => value?.trim() || undefined;
  let contactUrl = opt(raw?.contactUrl);
  if (contactUrl && !isHttpUrl(contactUrl)) {
    console.warn(
      `[Folio] settings.yaml legal.contactUrl: dropping ${JSON.stringify(contactUrl)} — ` +
        'only http(s) URLs are allowed.',
    );
    contactUrl = undefined;
  }
  return {
    enabled: raw?.enabled === true,
    heading: opt(raw?.heading),
    name: raw?.name || '',
    address: raw?.address || '',
    zipCity: raw?.zipCity || '',
    country: raw?.country || '',
    email: opt(raw?.email),
    phone: opt(raw?.phone),
    contactUrl,
    contactLabel: opt(raw?.contactLabel),
    taxId: opt(raw?.taxId),
    vatId: opt(raw?.vatId),
    extraInfo: opt(raw?.extraInfo),
  };
}

/**
 * The `contact:` block. `CONTACT_NOTIFY_URL` wins over `notifyUrl`, the same
 * precedence SITE_PASSWORD has: an ntfy topic URL is as good as a password to
 * anyone who wants to spam the owner's phone, so it may live outside the YAML.
 * A non-http(s) URL is dropped with a warning, like `legal.contactUrl`.
 */
export function resolveContact(
  raw?: SettingsYaml['contact'],
  envNotifyUrl?: string,
): ContactConfig {
  let notifyUrl = envNotifyUrl?.trim() || raw?.notifyUrl?.trim() || undefined;
  if (notifyUrl && !isHttpUrl(notifyUrl)) {
    console.warn(
      `[Folio] contact.notifyUrl: dropping ${JSON.stringify(notifyUrl)} — only http(s) URLs are allowed.`,
    );
    notifyUrl = undefined;
  }
  const days = raw?.retentionDays;
  return {
    enabled: raw?.enabled === true,
    notifyUrl,
    retentionDays:
      typeof days === 'number' && Number.isFinite(days)
        ? clamp(Math.round(days), 1, CONTACT_RETENTION_MAX)
        : CONTACT_RETENTION_DEFAULT,
  };
}

/** The parts of AppConfig that come from gallery.yaml. */
export interface GalleryDerivation {
  albums: string[];
  standaloneAlbums: string[];
  subpages: SubpageConfig[];
  nav: NavEntry[];
  albumOverrides: Record<string, string>;
  albumDescriptions: Record<string, string>;
  albumPasswords: Record<string, string>;
  albumHeroImages: Record<string, string>;
  albumSortModes: Record<string, AlbumSortMode>;
  albumManualOrders: Record<string, string[]>;
  albumGrids: Record<string, Partial<GridConfig>>;
  albumCoverPositions: Record<string, string>;
  albumDownloads: Record<string, boolean>;
  /** Album zoom overrides on the standalone entries; subpages carry their own. */
  standaloneAlbumZoom: Record<string, boolean>;
  albumLocationPrecision: Record<string, LocationPrecision>;
}

/**
 * Derive the gallery half of AppConfig, throwing on a structure that cannot be
 * represented: a subpage with no name, a subpage with neither albums nor
 * sections. A gallery with no albums and no subpages is NOT an error — an
 * empty gallery still renders (title, hero-less homepage) so the owner can
 * add albums later via /admin.
 *
 * Extracted from getConfig() so the admin PUT can run the *real* derivation
 * against a proposed gallery before writing it. Re-implementing the three
 * checks in the route would guarantee drift; write-then-verify-then-roll-back
 * would leave a window where other requests read the broken config.
 */
export function deriveGallery(gallery: GalleryYaml): GalleryDerivation {
  const albumOverrides: Record<string, string> = {};
  const albumDescriptions: Record<string, string> = {};
  const albumPasswords: Record<string, string> = {};
  const albumHeroImages: Record<string, string> = {};
  const albumSortModes: Record<string, AlbumSortMode> = {};
  const albumManualOrders: Record<string, string[]> = {};
  const albumGrids: Record<string, Partial<GridConfig>> = {};
  const albumCoverPositions: Record<string, string> = {};
  const albumDownloads: Record<string, boolean> = {};
  /**
   * Per-album zoom overrides (#467), one map per route: the standalone entries
   * here, each subpage's (sections included) on the subpage. An album listed on
   * two pages can be zoomable on one and not the other; a single map would let
   * whichever entry came last decide for both.
   */
  const standaloneAlbumZoom: Record<string, boolean> = {};
  const albumLocationPrecision: Record<string, LocationPrecision> = {};

  /** Returns null for an entry whose album ID is not a UUID; callers drop it. */
  function processAlbumEntry(
    entry: string | Record<string, string | AlbumEntryObject>,
    context: string,
    inheritedLocation?: LocationPrecision,
    zoomSink?: Record<string, boolean>,
  ): string | null {
    if (typeof entry === 'string') {
      if (inheritedLocation) albumLocationPrecision[entry] = inheritedLocation;
      return validateUuid(entry, context);
    }
    const [uuid, value] = Object.entries(entry)[0];
    const validatedUuid = validateUuid(uuid, context);
    if (!validatedUuid) return null;
    // The subpage's setting applies unless the album states its own below.
    if (inheritedLocation) albumLocationPrecision[validatedUuid] = inheritedLocation;

    if (typeof value === 'string') {
      albumOverrides[validatedUuid] = value;
    } else {
      if (value.title) albumOverrides[validatedUuid] = value.title;
      if (value.description) albumDescriptions[validatedUuid] = value.description;
      if (value.password) albumPasswords[validatedUuid] = value.password;
      // The album ID (the key) is validated above; the hero asset ID is a
      // separate UUID and was previously stored raw. It flows to encodeAssetId
      // via app/[...path]/page.tsx, which encrypts whatever it is handed — so a
      // typo here produced a well-formed URL that 404s forever, with nothing in
      // the log naming the cause. Every other ID in this file goes through
      // validateUuid; this one was the gap.
      if (value.heroImage) {
        const heroId = validateUuid(
          value.heroImage,
          `${context} heroImage for album ${validatedUuid}`,
        );
        // Dropped rather than defaulted: without one the album falls back to its
        // Immich cover, which is a better answer than a request that 400s.
        if (heroId) albumHeroImages[validatedUuid] = heroId;
      }

      // Throw rather than fall back to the default: a typo would otherwise be
      // invisible — the album would just keep rendering in Immich order and the
      // owner would be left wondering why the setting does nothing. Throwing
      // also gives the admin PUT its 400 for free via the deriveGallery
      // dry-run, and getConfigOrNull() degrades a hand-edited file to the setup
      // screen rather than taking the site down. Name the album and the legal
      // values so the log line is enough to fix it.
      if (value.sort != null) {
        if (!isAlbumSortMode(value.sort)) {
          throw new Error(
            `${context}: album ${validatedUuid} has an unknown sort "${value.sort}". ` +
              `Valid values are: ${ALBUM_SORT_MODES.join(', ')}.`,
          );
        }
        albumSortModes[validatedUuid] = value.sort;
      }

      // Kept regardless of the mode, so switching manual → newest → manual does
      // not silently destroy a hand-curated order.
      if (value.assetOrder?.length) {
        albumManualOrders[validatedUuid] = value.assetOrder
          .map((assetId, i) =>
            validateUuid(assetId, `${context} assetOrder[${i}] for album ${validatedUuid}`),
          )
          .filter((id): id is string => id !== null);
      }

      // EXPERIMENTAL: per-album grid override — reuses the subpage-grid
      // normalisation so unknown layouts degrade identically.
      if (value.grid) {
        const built = buildSubpageGrid(value.grid);
        if ('grid' in built) albumGrids[validatedUuid] = built.grid;
      }

      // EXPERIMENTAL: coverPosition lands in a style attribute, so only a
      // strict CSS position grammar is allowed. Throw like `sort` does — a
      // silent fallback would leave the owner wondering why nothing moves.
      if (value.coverPosition != null) {
        const pos = value.coverPosition.trim();
        const keyword = /^(center|top|bottom|left|right)( (center|top|bottom|left|right))?$/;
        const percent = /^\d{1,3}% \d{1,3}%$/;
        if (!keyword.test(pos) && !percent.test(pos)) {
          throw new Error(
            `${context}: album ${validatedUuid} has an invalid coverPosition "${value.coverPosition}". ` +
              `Use two percentages ("50% 25%") or CSS keywords ("top", "center bottom").`,
          );
        }
        albumCoverPositions[validatedUuid] = pos;
      }

      // Opt-in per album, never global: a public portfolio must not start
      // handing out full-resolution originals because one client gallery
      // needed to (#475).
      if (value.download === true) albumDownloads[validatedUuid] = true;
      // Both values mean something: `false` switches zoom off here even where
      // the subpage or the site has it on (#467). Anything else is ignored.
      // Written to the route this entry is on. Listed twice on one route (two
      // sections of a page), the cautious answer wins: `false` stays `false`.
      if (zoomSink && typeof value.zoom === 'boolean') {
        zoomSink[validatedUuid] = zoomSink[validatedUuid] !== false && value.zoom;
      }
      const location = parseLocation(value.location, `${context}: album ${validatedUuid} location`);
      if (location) albumLocationPrecision[validatedUuid] = location;
    }
    return validatedUuid;
  }

  /** Album entries, with the ones whose ID is not a UUID dropped (#517). */
  function processAlbumEntries(
    entries: Array<string | Record<string, string | AlbumEntryObject>>,
    context: string,
    inheritedLocation?: LocationPrecision,
    zoomSink?: Record<string, boolean>,
  ): string[] {
    return entries
      .map((entry) => processAlbumEntry(entry, context, inheritedLocation, zoomSink))
      .filter((id): id is string => id !== null);
  }

  /**
   * Narrow a raw `location:` value, or throw. Rejected rather than defaulted
   * for the same reason as `sort`: a typo in a privacy setting that silently
   * fell back to `exact` would publish the position it was meant to withhold.
   */
  function parseLocation(raw: string | undefined, context: string): LocationPrecision | undefined {
    if (raw == null) return undefined;
    if (!isLocationPrecision(raw)) {
      throw new Error(
        `${context}: unknown location "${raw}". ` +
          `Valid values are: ${LOCATION_PRECISIONS.join(', ')}.`,
      );
    }
    return raw;
  }

  const standaloneAlbumIds = processAlbumEntries(
    gallery.albums ?? [],
    'gallery.yaml albums',
    undefined,
    standaloneAlbumZoom,
  );

  let subpages: SubpageConfig[] = [];
  /** Menu order, subpages and `- page:` references interleaved (#722). */
  const nav: NavEntry[] = [];

  if (Array.isArray(gallery.subpages)) {
    const pageRefs = new Set<string>();
    const subpageEntries: GallerySubpageYaml[] = [];
    for (const entry of gallery.subpages) {
      if (isPageRef(entry)) {
        const slug = entry.page.trim();
        // Thrown like every other structure error: the admin PUT turns it into
        // a 400, and a hand-edited file degrades to the setup screen.
        if (!isValidSlug(slug)) {
          throw new Error(
            `gallery.yaml subpages: "page: ${entry.page}" is not a valid page slug ` +
              `(letters, digits, "-" and "_" only).`,
          );
        }
        if (pageRefs.has(slug)) {
          throw new Error(`gallery.yaml subpages: page "${slug}" is listed more than once.`);
        }
        pageRefs.add(slug);
        nav.push({ type: 'page', slug });
      } else {
        subpageEntries.push(entry);
        // Placeholder, filled in with the derived slug below.
        nav.push({ type: 'subpage', slug: '' });
      }
    }
    subpages = subpageEntries.map((sp) => {
      if (!sp.name) {
        throw new Error(`Subpage "(unnamed)" must have a name`);
      }

      // This page's own album zoom overrides, sections included (#467).
      const albumZoom: Record<string, boolean> = {};

      // Parse sections if present
      let sections: SubpageSectionConfig[] | undefined;
      let albumIds: string[];

      if (sp.sections && sp.sections.length > 0) {
        sections = sp.sections.map((sec) => ({
          title: sec.title,
          slug: slugify(sec.title),
          description: sec.description,
          albumIds: processAlbumEntries(
            sec.albums,
            `subpage "${sp.name}" section "${sec.title}"`,
            parseLocation(sp.location, `subpage "${sp.name}" location`),
            albumZoom,
          ),
        }));
        // flat union of all section albums
        albumIds = sections!.flatMap((sec) => sec.albumIds);
        // Also include any top-level albums (outside sections)
        const topLevel = processAlbumEntries(
          sp.albums ?? [],
          `subpage "${sp.name}"`,
          parseLocation(sp.location, `subpage "${sp.name}" location`),
          albumZoom,
        );
        albumIds = [...topLevel, ...albumIds];
      } else {
        const albums = sp.albums ?? [];
        if (albums.length === 0) {
          throw new Error(`Subpage "${sp.name}" must have albums or sections`);
        }
        albumIds = processAlbumEntries(
          albums,
          `subpage "${sp.name}"`,
          parseLocation(sp.location, `subpage "${sp.name}" location`),
          albumZoom,
        );
      }

      return {
        name: sp.name,
        slug: slugify(sp.name),
        title: sp.title,
        subtitle: sp.subtitle,
        albumIds,
        sections,
        password: sp.password,
        proofing: sp.proofing,
        zoom: typeof sp.zoom === 'boolean' ? sp.zoom : undefined,
        ...(Object.keys(albumZoom).length ? { albumZoom } : {}),
        essayFile: sp.essayFile,
        essayText: sp.essayText,
        enabled: sp.enabled !== false,
        hidden: sp.hidden === true,
        ...buildSubpageGrids(sp.grid, sp.coverGrid),
      };
    });
    let next = 0;
    for (const entry of nav) {
      if (entry.type === 'subpage') entry.slug = subpages[next++].slug;
    }
  } else if (gallery.subpages) {
    subpages = Object.entries(gallery.subpages).map(([name, value]) => {
      if (Array.isArray(value)) {
        return {
          name,
          slug: slugify(name),
          albumIds: processAlbumEntries(value, `subpage "${name}"`),
          enabled: true,
        };
      }
      const sp = value as SubpageObjectValue;
      const albumEntries = sp.albums || [];
      const albumZoom: Record<string, boolean> = {};
      return {
        name,
        slug: slugify(name),
        title: sp.title,
        subtitle: sp.subtitle,
        albumIds: processAlbumEntries(
          albumEntries,
          `subpage "${name}"`,
          parseLocation(sp.location, `subpage "${name}" location`),
          albumZoom,
        ),
        password: sp.password,
        proofing: sp.proofing,
        zoom: typeof sp.zoom === 'boolean' ? sp.zoom : undefined,
        ...(Object.keys(albumZoom).length ? { albumZoom } : {}),
        essayFile: sp.essayFile,
        essayText: sp.essayText,
        enabled: sp.enabled !== false,
        hidden: sp.hidden === true,
        ...buildSubpageGrids(sp.grid, sp.coverGrid),
      };
    });
  }

  if (!Array.isArray(gallery.subpages)) {
    for (const sp of subpages) nav.push({ type: 'subpage', slug: sp.slug });
  }

  const subpageAlbumIds = new Set(subpages.flatMap((sp) => sp.albumIds));
  const allAlbumIds = [...new Set([...standaloneAlbumIds, ...subpageAlbumIds])];
  const standaloneAlbums = standaloneAlbumIds.filter((id) => !subpageAlbumIds.has(id));

  // Every consumer that resolves a slug takes the first match — getAlbumBySlug,
  // the sitemap, findPassword — so two subpages that slugify alike leave the
  // second unreachable and its password / albums resolved from the first
  // (#632). slugify() folds diacritics and punctuation, so distinct names
  // collide easily: "Portfolio 2024" and "Portfolio-2024" both become
  // "portfolio-2024".
  const subpagesBySlug = new Map<string, string[]>();
  for (const sp of subpages) {
    const names = subpagesBySlug.get(sp.slug) ?? [];
    names.push(sp.name);
    subpagesBySlug.set(sp.slug, names);
  }
  for (const [slug, names] of subpagesBySlug) {
    if (names.length > 1) {
      throw new Error(
        `Subpages ${names.map((n) => `"${n}"`).join(' and ')} all produce the slug "${slug}". ` +
          `Rename one so their URLs do not collide.`,
      );
    }
  }

  // Same rule applies to albums that share a route (standalone albums among
  // themselves, or one subpage's albums including its sections). Only a title
  // override is known here without asking Immich — an album that keeps its
  // Immich name can still collide, which is what the doctor's equivalent
  // check, run against the live album list, is for.
  const checkAlbumOverrideCollisions = (context: string, ids: string[]) => {
    const named = ids
      .map((id) => ({ id, name: albumOverrides[id] }))
      .filter((a): a is { id: string; name: string } => !!a.name);
    for (const { slug, albums } of findAlbumSlugCollisions(named)) {
      throw new Error(
        `${context}: albums titled ${albums.map((a) => `"${a.name}"`).join(' and ')} all produce ` +
          `the slug "${slug}". Give one a different title override.`,
      );
    }
  };
  checkAlbumOverrideCollisions('gallery.yaml albums', standaloneAlbums);
  for (const sp of subpages) {
    checkAlbumOverrideCollisions(`subpage "${sp.name}"`, sp.albumIds);
  }

  return {
    albums: allAlbumIds,
    standaloneAlbums,
    subpages,
    nav,
    albumOverrides,
    albumDescriptions,
    albumPasswords,
    albumHeroImages,
    albumSortModes,
    albumManualOrders,
    albumGrids,
    albumCoverPositions,
    albumDownloads,
    standaloneAlbumZoom,
    albumLocationPrecision,
  };
}

/** Whether content/about.md exists — the About page has nothing to show without it. */
function aboutContentExists(): boolean {
  try {
    return fs.existsSync(path.join(process.cwd(), 'content', 'about.md'));
  } catch {
    return false;
  }
}

/**
 * Everything deriveConfig() reads, as one string: the path and mtime of each
 * file (or `-` when it is absent) and the parsed environment.
 */
function configInputs(): string {
  const content = path.join(process.cwd(), 'content');
  const files = [
    installFilePath(),
    path.join(content, 'gallery.yaml'),
    path.join(content, 'settings.yaml'),
    path.join(content, 'about.md'),
  ];
  // throwIfNoEntry: a missing file is the normal case for install.json and
  // about.md, and building an ENOENT error costs more than the stat.
  // turbopackIgnore: `file` is not statically resolvable, so without the
  // comment Turbopack traces the whole project into .next/standalone. Only
  // the mtime is read here; the files themselves are loaded elsewhere.
  const stamps = files.map(
    (file) =>
      `${file}@${fs.statSync(/* turbopackIgnore: true */ file, { throwIfNoEntry: false })?.mtimeMs ?? '-'}`,
  );
  return `${stamps.join('|')}|${JSON.stringify(env)}`;
}

/**
 * The site configuration.
 *
 * Admin saves can land in a different worker or process than page rendering,
 * so this cannot be a per-process singleton: freshness comes from the files'
 * mtimes, re-checked on every call (a statSync each). What is cached is the
 * derivation. A render and every image request call this many times over
 * (`immich.config` is a getter), and rebuilding the whole config from the
 * YAML each time cost more than the stats.
 *
 * The inputs are the ones loadYaml() and readInstallFile() already key their
 * own caches on, so this is never staler than they are. Each caller still
 * gets its own copy, exactly as before: nothing can mutate the cached one.
 * A config that throws is not cached, so it throws again on the next call.
 */
export function getConfig(): AppConfig {
  const inputs = configInputs();
  if (derived?.inputs !== inputs) {
    derived = { inputs, config: deriveConfig() };
  }
  return structuredClone(derived.config);
}

function deriveConfig(): AppConfig {
  const { apiUrl, apiKey } = getInstallCredentials();
  const authSecret = resolveAuthSecret();

  // The API URL may already end with /api (a user-supplied env var or a
  // wizard-installed value). Appending unconditionally produces a double
  // suffix and breaks every Immich request.
  const immichApiUrl = apiUrl.endsWith('/api') ? apiUrl : `${apiUrl}/api`;

  const gallery = loadYaml<GalleryYaml>('gallery.yaml');
  const settings = loadYaml<SettingsYaml>('settings.yaml') || {};

  // Two separate faults, deliberately kept apart. Missing credentials mean
  // nothing can reach Immich; a missing gallery.yaml only means the public site
  // has nothing to list yet. Conflating them made a credentialed deployment
  // without gallery.yaml report "Immich disconnected" and locked the admin
  // panel out of the album pickers that would have created the file (#507).
  const needsCredentials = !apiKey || !apiUrl;
  const needsGallery = !gallery;

  if (needsCredentials || needsGallery) {
    // Return dummy config if gallery.yaml is missing
    return {
      immich: { apiUrl: immichApiUrl, apiKey },
      authSecret,
      albums: [],
      standaloneAlbums: [],
      subpages: [],
      nav: [],
      siteTitle: env.SITE_TITLE || 'Immich Folio',
      siteSubtitle: env.SITE_SUBTITLE || 'Setup Required',
      lang: 'en',
      // Nothing to protect yet, and a gate here would sit in front of the
      // setup screen that is trying to tell the operator what is missing.
      sitePassword: '',
      seo: {
        title: 'Setup Required',
        description: 'Please configure Immich Folio',
        titleTemplate: '%s | Setup Required',
        license: '',
        noIndex: true,
        noFollow: true,
      },
      heroImages: [],
      siteUrl: null,
      siteUrlSource: 'none',
      colorMode: 'dark',
      exifOnHover: true,
      exif: resolveExifDisplay(),
      grid: { columns: 3, gap: 12, aspectRatio: '1', layout: 'masonry' },
      gridGapExplicit: false,
      theme: resolveTheme(DEFAULT_PRESET),
      footer: null,
      legal: { enabled: false, name: '', address: '', zipCity: '', country: '' },
      contact: { enabled: false, retentionDays: CONTACT_RETENTION_DEFAULT },
      privacy: { enabled: false },
      map: false,
      transitions: false,
      scrollToTop: false,
      analytics: true,
      proofing: { enabled: false, allowMailto: false },
      aboutEnabled: true,
      zoom: false,
      albumOverrides: {},
      albumDescriptions: {},
      albumPasswords: {},
      albumHeroImages: {},
      albumSortModes: {},
      albumManualOrders: {},
      albumGrids: {},
      albumCoverPositions: {},
      albumDownloads: {},
      standaloneAlbumZoom: {},
      albumLocationPrecision: {},
      navLinks: [],
      cacheTtl: env.CACHE_TTL * 1000,
      staleMaxAge: env.STALE_MAX_AGE * 1000,
      immichTimeoutMs: env.IMMICH_TIMEOUT_MS,
      rateLimitRpm: env.RATE_LIMIT_RPM,
      trustedProxyHops: env.TRUSTED_PROXY_HOPS,
      needsSetup: true,
      needsCredentials,
      needsGallery,
    };
  }

  const theme = resolveTheme(settings.theme);

  const {
    albums: allAlbumIds,
    standaloneAlbums,
    subpages,
    nav,
    albumOverrides,
    albumDescriptions,
    albumPasswords,
    albumHeroImages,
    albumSortModes,
    albumManualOrders,
    albumGrids,
    albumCoverPositions,
    albumDownloads,
    standaloneAlbumZoom,
    albumLocationPrecision,
  } = deriveGallery(gallery);

  // Last-resort title in the site's own language rather than a hardcoded
  // English "Gallery" (#696).
  const defaultTitle = env.SITE_TITLE || getDictionary(resolveLocale(settings.lang)).common.gallery;
  const siteSeoTitle = settings.seo?.title || settings.title || defaultTitle;

  return {
    immich: { apiUrl: immichApiUrl, apiKey },
    authSecret,
    albums: allAlbumIds,
    standaloneAlbums,
    subpages,
    nav,
    siteTitle: settings.title ?? defaultTitle,
    siteSubtitle: settings.subtitle ?? env.SITE_SUBTITLE,
    lang: settings.lang ?? 'en',
    // Env wins, so a deployment can rotate the site password without touching
    // settings.yaml — the same precedence the Immich credentials use.
    sitePassword: env.SITE_PASSWORD ?? settings.sitePassword ?? '',
    seo: {
      title: siteSeoTitle,
      description:
        settings.seo?.description ||
        settings.subtitle ||
        env.SITE_SUBTITLE ||
        'A curated photography portfolio',
      titleTemplate: settings.seo?.titleTemplate || `%s | ${siteSeoTitle}`,
      noIndex: settings.seo?.noIndex === true,
      noFollow: settings.seo?.noFollow === true,
      license: settings.seo?.license?.trim() || '',
    },
    heroImages: gallery.hero
      ? (Array.isArray(gallery.hero) ? gallery.hero : [gallery.hero])
          .map((id) => validateUuid(id, 'gallery.yaml hero'))
          .filter((id): id is string => id !== null)
      : [],
    ...(() => {
      const site = resolveSiteUrl(settings.url, env.SITE_URL);
      return { siteUrl: site.url, siteUrlSource: site.source };
    })(),
    colorMode: resolveColorMode(settings.mode),
    exifOnHover: settings.exifOnHover !== false,
    exif: resolveExifDisplay(settings.exif, settings.exifOnHover),
    grid: {
      columns:
        settings.grid?.columns != null
          ? clamp(settings.grid.columns, PHOTO_GRID_COLUMNS_MIN, PHOTO_GRID_COLUMNS_MAX)
          : 3,
      gap: settings.grid?.gap != null ? clamp(settings.grid.gap, 0, PHOTO_GRID_GAP_MAX) : 12,
      aspectRatio: settings.grid?.aspectRatio ?? '1',
      layout: (VALID_LAYOUTS.includes(settings.grid?.layout ?? '')
        ? settings.grid!.layout
        : 'masonry') as GridConfig['layout'],
    },
    gridGapExplicit: settings.grid?.gap != null,
    theme,
    footer: settings.footer
      ? {
          name: settings.footer.name,
          instagram: settings.footer.instagram,
          email: settings.footer.email,
          website: settings.footer.website,
        }
      : null,
    legal: resolveLegal(settings.legal),
    contact: resolveContact(settings.contact, env.CONTACT_NOTIFY_URL),
    privacy: { enabled: settings.privacy?.enabled !== false },
    map: settings.map === true,
    transitions: settings.transitions !== false,
    scrollToTop: settings.scrollToTop !== false,
    analytics: settings.analytics !== false,
    proofing: {
      enabled: settings.proofing?.enabled !== false,
      allowMailto: settings.proofing?.allowMailto !== false,
      // `proofing.email`, else the footer contact email (#736); absent hides
      // the dialog's email button.
      email: resolveProofingEmail(settings.proofing?.email, settings.footer?.email),
    },
    protection: settings.protection,
    watermark: settings.watermark,
    // The setting alone is not enough: about.md does not exist until someone
    // writes it, so a fresh install put a nav link in front of an empty page
    // (#518). `enabled: false` still hides it even when the file is there.
    aboutEnabled: settings.about?.enabled !== false && aboutContentExists(),
    // Opt-in: zoom serves originals, which a portfolio must not start doing
    // because an upgrade added the feature (#467).
    zoom: settings.zoom === true,
    albumOverrides,
    albumDescriptions,
    albumPasswords,
    albumHeroImages,
    albumSortModes,
    albumManualOrders,
    albumGrids,
    albumCoverPositions,
    albumDownloads,
    standaloneAlbumZoom,
    albumLocationPrecision,
    navLinks: sanitizeNavLinks(settings.navLinks),
    cacheTtl: env.CACHE_TTL * 1000,
    staleMaxAge: env.STALE_MAX_AGE * 1000,
    immichTimeoutMs: env.IMMICH_TIMEOUT_MS,
    rateLimitRpm: env.RATE_LIMIT_RPM,
    trustedProxyHops: env.TRUSTED_PROXY_HOPS,
    needsSetup: false,
    needsCredentials: false,
    needsGallery: false,
  };
}