fix: zero month addition (#1733)

- Add zero month at the begining of each metric on the open page

apps/openpage-api/lib/add-zero-month.ts

@@ -0,0 +1,54 @@
+import { DateTime } from 'luxon';
+
+export interface TransformedData {
+  labels: string[];
+  datasets: Array<{
+    label: string;
+    data: number[];
+  }>;
+}
+
+export function addZeroMonth(transformedData: TransformedData): TransformedData {
+  const result = {
+    labels: [...transformedData.labels],
+    datasets: transformedData.datasets.map((dataset) => ({
+      label: dataset.label,
+      data: [...dataset.data],
+    })),
+  };
+
+  if (result.labels.length === 0) {
+    return result;
+  }
+
+  if (result.datasets.every((dataset) => dataset.data[0] === 0)) {
+    return result;
+  }
+
+  try {
+    let firstMonth = DateTime.fromFormat(result.labels[0], 'MMM yyyy');
+    if (!firstMonth.isValid) {
+      const formats = ['MMM yyyy', 'MMMM yyyy', 'MM/yyyy', 'yyyy-MM'];
+
+      for (const format of formats) {
+        firstMonth = DateTime.fromFormat(result.labels[0], format);
+        if (firstMonth.isValid) break;
+      }
+
+      if (!firstMonth.isValid) {
+        console.warn(`Could not parse date: "${result.labels[0]}"`);
+        return transformedData;
+      }
+    }
+
+    const zeroMonth = firstMonth.minus({ months: 1 }).toFormat('MMM yyyy');
+    result.labels.unshift(zeroMonth);
+    result.datasets.forEach((dataset) => {
+      dataset.data.unshift(0);
+    });
+
+    return result;
+  } catch (error) {
+    return transformedData;
+  }
+}