extract server transform and validation helpers

server/contentTransforms.js

@@ -0,0 +1,27 @@
+import path from "path";
+
+export function normalizeBackgroundTileId(value, idToSymbol = null) {
+  const normalizedId = String(value || "").trim();
+  if (!normalizedId) {
+    return "";
+  }
+  if (idToSymbol instanceof Map && idToSymbol.size > 0 && !idToSymbol.has(normalizedId)) {
+    return "";
+  }
+  return normalizedId;
+}
+
+export function areRowsOnlyFillChar(rows, fillChar = ".") {
+  if (!Array.isArray(rows) || rows.length === 0) {
+    return true;
+  }
+  return rows.every((row) => {
+    const normalizedRow = String(row || "");
+    return normalizedRow.length === 0 || normalizedRow.split("").every((ch) => ch === fillChar);
+  });
+}
+
+export function resolveContentPath(contentRoot, relativePath) {
+  const normalized = String(relativePath || "").replace(/\\/g, "/").replace(/^\/+/, "");
+  return path.resolve(contentRoot, normalized);
+}