/**
 * The Site's own name, tagline, icon and display switches. These started in
 * `config/<site>.site.json`, which meant a rebuild and a redeploy to change the
 * restaurant's name; they are content now, like the categories, and the config
 * is only the seed for a Site that has never been opened.
 *
 * The uploaded icon is a fixed path so its URL never changes when it is
 * replaced: the data directory owns `brand/icon.svg` and this file records the
 * switches around it.
 */

import { mkdir, readFile, rm, writeFile } from 'node:fs/promises';
import path from 'node:path';
import type { SiteConfig } from '../config.ts';
import { writeJsonAtomic } from './manifest.ts';

export const ICON_URL = '/brand/icon.svg';

const MAX_ICON_BYTES = 256 * 1024;

export class IdentityError extends Error {
  readonly status: number;

  constructor(message: string, status = 400) {
    super(message);
    this.name = 'IdentityError';
    this.status = status;
  }
}

export interface SiteIdentity {
  name: string;
  tagline: string | null;
  /** Whether the customer-facing pages say when a menu was published. */
  showDates: boolean;
  /** True when an uploaded icon is in place. */
  hasIcon: boolean;
}

interface StoredIdentity {
  name: string;
  tagline: string | null;
  showDates: boolean;
}

function cleanText(value: unknown, where: string): string {
  if (typeof value !== 'string' || value.trim() === '') {
    throw new IdentityError(`${where} cannot be empty`);
  }
  return value.trim().replace(/\s+/g, ' ');
}

function parse(raw: unknown): StoredIdentity {
  if (typeof raw !== 'object' || raw === null || Array.isArray(raw)) {
    throw new IdentityError('site.json must be an object');
  }
  const candidate = raw as Record<string, unknown>;
  return {
    name: cleanText(candidate['name'], 'name'),
    tagline:
      typeof candidate['tagline'] === 'string' && candidate['tagline'].trim() !== ''
        ? candidate['tagline'].trim()
        : null,
    showDates: candidate['showDates'] !== false,
  };
}

/**
 * An SVG is a document, not a picture: it can carry script and event handlers
 * that would run with this origin's authority. Only an authenticated owner can
 * upload one, but a stolen or careless icon should still not be a way to run
 * code in a customer's browser, so the file is reduced to shapes and the route
 * that serves it forbids everything else.
 */
export function sanitiseIcon(source: string): string {
  const withoutComments = source.replace(/<!--[\s\S]*?-->/g, '');
  const withoutForbidden = withoutComments
    .replace(/<\s*(script|foreignObject|iframe|object|embed|style)\b[\s\S]*?<\s*\/\s*\1\s*>/gi, '')
    .replace(/<\s*(script|foreignObject|iframe|object|embed|style)\b[^>]*\/?>/gi, '')
    .replace(/\son[a-z]+\s*=\s*("[^"]*"|'[^']*'|[^\s>]+)/gi, '')
    .replace(/(href|xlink:href)\s*=\s*("\s*javascript:[^"]*"|'\s*javascript:[^']*')/gi, '');
  return withoutForbidden.trim();
}

export interface IdentityStoreOptions {
  dataDir: string;
  seed: SiteConfig['brand'] & { showDates?: boolean };
}

export class IdentityStore {
  readonly file: string;
  readonly iconFile: string;

  private readonly seed: StoredIdentity;
  private stored: StoredIdentity | null = null;
  private iconPresent = false;

  constructor(options: IdentityStoreOptions) {
    this.file = path.join(options.dataDir, 'site.json');
    this.iconFile = path.join(options.dataDir, 'brand', 'icon.svg');
    this.seed = {
      name: options.seed.name,
      tagline: options.seed.tagline,
      showDates: options.seed.showDates ?? true,
    };
  }

  async load(): Promise<void> {
    if (this.stored !== null) return;
    try {
      this.stored = parse(JSON.parse(await readFile(this.file, 'utf8')));
    } catch (error) {
      if ((error as NodeJS.ErrnoException).code !== 'ENOENT') {
        throw new IdentityError(
          `${this.file} could not be read: ${error instanceof Error ? error.message : String(error)}`,
        );
      }
      this.stored = { ...this.seed };
      await this.save(this.stored);
    }
    try {
      await readFile(this.iconFile);
      this.iconPresent = true;
    } catch {
      this.iconPresent = false;
    }
  }

  view(): SiteIdentity {
    const stored = this.require();
    return { ...stored, hasIcon: this.iconPresent };
  }

  /** The Site as the renderers want it: seeded config, overlaid with identity. */
  apply(config: SiteConfig): SiteConfig {
    const identity = this.view();
    return {
      ...config,
      brand: {
        name: identity.name,
        tagline: identity.tagline,
        logo: identity.hasIcon ? ICON_URL : config.brand.logo,
      },
      display: { showDates: identity.showDates },
    };
  }

  async update(patch: { name?: string; tagline?: string | null; showDates?: boolean }): Promise<SiteIdentity> {
    const current = this.require();
    const next: StoredIdentity = {
      name: patch.name === undefined ? current.name : cleanText(patch.name, 'name'),
      tagline:
        patch.tagline === undefined
          ? current.tagline
          : patch.tagline === null || patch.tagline.trim() === ''
            ? null
            : patch.tagline.trim(),
      showDates: patch.showDates === undefined ? current.showDates : patch.showDates,
    };
    await this.save(next);
    return this.view();
  }

  async putIcon(upload: Buffer): Promise<void> {
    if (upload.byteLength === 0) throw new IdentityError('that file is empty');
    if (upload.byteLength > MAX_ICON_BYTES) {
      throw new IdentityError(`an icon has to be under ${Math.round(MAX_ICON_BYTES / 1024)} KB`);
    }
    const text = upload.toString('utf8');
    if (!/<svg[\s>]/i.test(text)) throw new IdentityError('that file is not an SVG');
    if (!/<\/svg>/i.test(text)) throw new IdentityError('that SVG looks truncated');

    await mkdir(path.dirname(this.iconFile), { recursive: true });
    await writeFile(this.iconFile, sanitiseIcon(text), { mode: 0o644 });
    this.iconPresent = true;
  }

  async removeIcon(): Promise<void> {
    await rm(this.iconFile, { force: true });
    this.iconPresent = false;
  }

  iconPath(): string {
    return this.iconFile;
  }

  private require(): StoredIdentity {
    if (this.stored === null) throw new Error('IdentityStore.load() has not been awaited');
    return this.stored;
  }

  private async save(next: StoredIdentity): Promise<void> {
    await writeJsonAtomic(this.file, next);
    this.stored = next;
  }
}