Consolidate MangaCircus app, scraper, and Compose baseline

scraper/lib/json-file.js

@@ -0,0 +1,30 @@
+'use strict';
+
+const fs = require('fs').promises;
+const path = require('path');
+const crypto = require('crypto');
+
+async function writeJsonAtomic(file, value, io = fs) {
+  const folder = path.dirname(file), name = path.basename(file);
+  const temp = path.join(folder, `.${name}.${crypto.randomUUID()}.tmp`);
+  await io.writeFile(temp, JSON.stringify(value, null, 2) + '\n');
+  try {
+    try { await io.rename(temp, file); return; }
+    catch (error) {
+      if (!['EPERM', 'EACCES', 'EBUSY', 'EEXIST'].includes(error.code)) throw error;
+    }
+    // Windows may refuse rename-over-existing. Keep the old JSON recoverable
+    // until the replacement is safely in place; never delete it first.
+    const backup = path.join(folder, `.old-${name}-${crypto.randomUUID()}`);
+    await io.rename(file, backup);
+    try { await io.rename(temp, file); }
+    catch (error) {
+      try { await io.rename(backup, file); }
+      catch (restoreError) { error.message += `; previous JSON remains at ${backup}: ${restoreError.message}`; }
+      throw error;
+    }
+    await io.rm(backup, { force: true });
+  } finally { await io.rm(temp, { force: true }); }
+}
+
+module.exports = { writeJsonAtomic };