feat: First iteration, multi themes, I18N

public/js/services/storage.js

@@ -0,0 +1,106 @@
+// Persistence in browser cookies.
+//
+// A cookie holds ~4 KB, so a save is base64url-encoded and split in chunks:
+//   ic_save_<theme>_n   -> number of chunks
+//   ic_save_<theme>_0.. -> the chunks
+// Each theme has its own save slot. Preferences (theme, language) are stored
+// in a single small cookie.
+
+import { readCookie, removeCookie, writeCookie } from './cookies.js';
+
+const CHUNK_SIZE = 3000;
+const MAX_CHUNKS = 6;
+const PREFS_KEY = 'ic_prefs';
+const saveKey = (themeId) => `ic_save_${themeId}`;
+
+// ------------------------------------------------------------------ encoding
+
+export function encode(text) {
+  const bytes = new TextEncoder().encode(text);
+  let binary = '';
+  for (const b of bytes) binary += String.fromCharCode(b);
+  return btoa(binary).replaceAll('+', '-').replaceAll('/', '_').replace(/=+$/, '');
+}
+
+export function decode(encoded) {
+  const base64 = encoded.replaceAll('-', '+').replaceAll('_', '/');
+  const binary = atob(base64 + '='.repeat((4 - (base64.length % 4)) % 4));
+  return new TextDecoder().decode(Uint8Array.from(binary, (c) => c.charCodeAt(0)));
+}
+
+// ------------------------------------------------------------------- chunked
+
+function writeChunked(key, text) {
+  const encoded = encode(text);
+  const chunks = [];
+  for (let i = 0; i < encoded.length; i += CHUNK_SIZE) chunks.push(encoded.slice(i, i + CHUNK_SIZE));
+  if (chunks.length > MAX_CHUNKS) throw new Error('save_too_large');
+
+  const previous = Number(readCookie(`${key}_n`)) || 0;
+  chunks.forEach((chunk, i) => writeCookie(`${key}_${i}`, chunk));
+  writeCookie(`${key}_n`, String(chunks.length));
+  for (let i = chunks.length; i < previous; i++) removeCookie(`${key}_${i}`);
+}
+
+function readChunked(key) {
+  const count = Number(readCookie(`${key}_n`));
+  if (!Number.isInteger(count) || count < 1 || count > MAX_CHUNKS) return null;
+  let encoded = '';
+  for (let i = 0; i < count; i++) {
+    const chunk = readCookie(`${key}_${i}`);
+    if (chunk == null) return null;
+    encoded += chunk;
+  }
+  try {
+    return decode(encoded);
+  } catch {
+    return null;
+  }
+}
+
+function removeChunked(key) {
+  const count = Number(readCookie(`${key}_n`)) || 0;
+  for (let i = 0; i < count; i++) removeCookie(`${key}_${i}`);
+  removeCookie(`${key}_n`);
+}
+
+// -------------------------------------------------------------------- public
+
+/** False when the browser refuses cookies (private mode, blocked, ...). */
+export function cookiesAvailable() {
+  try {
+    writeCookie('ic_probe', '1');
+    const ok = readCookie('ic_probe') === '1';
+    removeCookie('ic_probe');
+    return ok;
+  } catch {
+    return false;
+  }
+}
+
+/** Throws if the save does not fit in cookies. */
+export function saveGameText(themeId, text) {
+  writeChunked(saveKey(themeId), text);
+}
+
+export function loadGameText(themeId) {
+  return readChunked(saveKey(themeId));
+}
+
+export function deleteGame(themeId) {
+  removeChunked(saveKey(themeId));
+}
+
+export function savePrefs(prefs) {
+  writeCookie(PREFS_KEY, encode(JSON.stringify(prefs)));
+}
+
+export function loadPrefs() {
+  try {
+    const raw = readCookie(PREFS_KEY);
+    const prefs = raw && JSON.parse(decode(raw));
+    return prefs && typeof prefs === 'object' ? prefs : {};
+  } catch {
+    return {};
+  }
+}