feat: First iteration, multi themes, I18N

public/js/services/saveio.js

@@ -0,0 +1,64 @@
+// Export / import of a save as a JSON or TXT file (or pasted text).
+// Works on every device: download via a Blob link, import via file input or paste.
+
+import { sanitizeState, serializeState } from '../engine/state.js';
+
+const GAME_ID = 'idle-clicker';
+const FORMAT = 1;
+
+export class ImportError extends Error {
+  /** @param {'empty'|'invalid'|'unknown_theme'|'wrong_game'} code */
+  constructor(code) {
+    super(code);
+    this.code = code;
+  }
+}
+
+/** The text a player downloads, copies or pastes back. */
+export function buildExport(themeId, state, now = Date.now()) {
+  return JSON.stringify(
+    {
+      game: GAME_ID,
+      format: FORMAT,
+      theme: themeId,
+      exportedAt: new Date(now).toISOString(),
+      state: JSON.parse(serializeState(state)),
+    },
+    null,
+    2,
+  );
+}
+
+/** Validate imported text. Throws ImportError; never trusts the content. */
+export function parseImport(text, ctx, knownThemeIds) {
+  const trimmed = String(text ?? '').trim().replace(/^/, '');
+  if (!trimmed) throw new ImportError('empty');
+
+  let data;
+  try {
+    data = JSON.parse(trimmed);
+  } catch {
+    throw new ImportError('invalid');
+  }
+  if (data?.game !== GAME_ID || data.format !== FORMAT) throw new ImportError('wrong_game');
+  if (!knownThemeIds.includes(data.theme)) throw new ImportError('unknown_theme');
+
+  const state = sanitizeState(data.state, ctx);
+  if (!state) throw new ImportError('invalid');
+  return { themeId: data.theme, state };
+}
+
+export function downloadText(filename, text, mime = 'application/json') {
+  const url = URL.createObjectURL(new Blob([text], { type: `${mime};charset=utf-8` }));
+  const link = document.createElement('a');
+  link.href = url;
+  link.download = filename;
+  document.body.append(link);
+  link.click();
+  link.remove();
+  setTimeout(() => URL.revokeObjectURL(url), 10_000);
+}
+
+export function readFileText(file) {
+  return file.text();
+}