feat(frontend): add status page for loading dataset

frontend/src/pages/DatasetStatus.tsx

@@ -0,0 +1,111 @@
+import { useEffect, useMemo, useState } from "react";
+import axios from "axios";
+import { useNavigate, useParams } from "react-router-dom";
+import StatsStyling from "../styles/stats_styling";
+
+type DatasetStatusResponse = {
+  status?: "processing" | "complete" | "error";
+  status_message?: string | null;
+  completed_at?: string | null;
+};
+
+const styles = StatsStyling;
+const API_BASE_URL = "http://localhost:5000";
+
+const DatasetStatusPage = () => {
+  const navigate = useNavigate();
+  const { datasetId } = useParams<{ datasetId: string }>();
+  const [loading, setLoading] = useState(true);
+  const [status, setStatus] = useState<DatasetStatusResponse["status"]>("processing");
+  const [statusMessage, setStatusMessage] = useState("");
+  const parsedDatasetId = useMemo(() => Number(datasetId), [datasetId]);
+
+  useEffect(() => {
+    if (!Number.isInteger(parsedDatasetId) || parsedDatasetId <= 0) {
+      setLoading(false);
+      setStatus("error");
+      setStatusMessage("Invalid dataset id.");
+      return;
+    }
+
+    let pollTimer: number | undefined;
+
+    const pollStatus = async () => {
+      try {
+        const response = await axios.get<DatasetStatusResponse>(
+          `${API_BASE_URL}/dataset/${parsedDatasetId}/status`
+        );
+
+        const nextStatus = response.data.status ?? "processing";
+        setStatus(nextStatus);
+        setStatusMessage(String(response.data.status_message ?? ""));
+        setLoading(false);
+
+        if (nextStatus === "complete") {
+          window.setTimeout(() => {
+            navigate("/stats", { replace: true });
+          }, 800);
+        }
+      } catch (error: unknown) {
+        setLoading(false);
+        setStatus("error");
+        if (axios.isAxiosError(error)) {
+          const message = String(error.response?.data?.error || error.message || "Request failed");
+          setStatusMessage(message);
+        } else {
+          setStatusMessage("Unable to fetch dataset status.");
+        }
+      }
+    };
+
+    void pollStatus();
+    pollTimer = window.setInterval(() => {
+      if (status !== "complete" && status !== "error") {
+        void pollStatus();
+      }
+    }, 2000);
+
+    return () => {
+      if (pollTimer) {
+        window.clearInterval(pollTimer);
+      }
+    };
+  }, [navigate, parsedDatasetId, status]);
+
+  const isProcessing = loading || status === "processing";
+  const isError = status === "error";
+
+  return (
+    <div style={styles.page}>
+      <div style={{ ...styles.container, maxWidth: 720 }}>
+        <div style={{ ...styles.card, marginTop: 28 }}>
+          <h1 style={{ margin: 0, fontSize: 28, color: "#111827" }}>
+            {isProcessing ? "Processing dataset..." : isError ? "Dataset processing failed" : "Dataset ready"}
+          </h1>
+
+          <p style={{ ...styles.sectionSubtitle, marginTop: 10 }}>
+            {isProcessing &&
+              "Your dataset is being analyzed. This page will redirect to stats automatically once complete."}
+            {isError && "There was an issue while processing your dataset. Please review the error details."}
+            {status === "complete" && "Processing complete. Redirecting to your stats now..."}
+          </p>
+
+          <div
+            style={{
+              ...styles.card,
+              marginTop: 12,
+              borderColor: isError ? "rgba(185, 28, 28, 0.28)" : "rgba(0,0,0,0.06)",
+              background: isError ? "#fff5f5" : "#ffffff",
+              color: isError ? "#991b1b" : "#374151",
+              boxShadow: "none",
+            }}
+          >
+            {statusMessage || (isProcessing ? "Waiting for updates from the worker queue..." : "No details provided.")}
+          </div>
+        </div>
+      </div>
+    </div>
+  );
+};
+
+export default DatasetStatusPage;