Added download option for assignment cards

Export PDF Download to hook
Prevented some NaN's

src/hooks/usePDFDownload.tsx

@@ -0,0 +1,60 @@
+import React from "react";
+import axios from "axios";
+import { toast } from "react-toastify";
+import { BsFilePdf } from "react-icons/bs";
+
+type DownloadingPdf = {
+  [key: string]: boolean;
+};
+
+type PdfEndpoint = "stats" | "assignments";
+
+export const usePDFDownload = (endpoint: PdfEndpoint) => {
+  const [downloadingPdf, setDownloadingPdf] = React.useState<DownloadingPdf>(
+    {}
+  );
+
+  const triggerDownload = async (id: string) => {
+    try {
+      setDownloadingPdf((prev) => ({ ...prev, [id]: true }));
+      const res = await axios.post(`/api/${endpoint}/${id}/export`);
+      toast.success("Report ready!");
+      const link = document.createElement("a");
+      link.href = res.data;
+      // download should have worked but there are some CORS issues
+      // https://firebase.google.com/docs/storage/web/download-files#cors_configuration
+      // link.download="report.pdf";
+      link.target = "_blank";
+      link.rel = "noreferrer";
+      link.click();
+      setDownloadingPdf((prev) => ({ ...prev, [id]: false }));
+    } catch (err) {
+      toast.error("Failed to display the report!");
+      console.error(err);
+      setDownloadingPdf((prev) => ({ ...prev, [id]: false }));
+    }
+  };
+
+  const renderIcon = (
+    id: string,
+    downloadClasses: string,
+    loadingClasses: string
+  ) => {
+    if (downloadingPdf[id]) {
+      return (
+        <span className={`${loadingClasses} loading loading-infinity w-6`} />
+      );
+    }
+    return (
+      <BsFilePdf
+        className={`${downloadClasses} text-2xl cursor-pointer`}
+        onClick={(e) => {
+          e.stopPropagation();
+          triggerDownload(id);
+        }}
+      />
+    );
+  };
+
+  return renderIcon;
+};