Enable support for exporting 1D and 2D dataset slices.

app/utils.ts

@@ -5,7 +5,12 @@ import { vscode } from './vscode-api.js';
 // 2 GB = 2 * 1024 * 1024 * 1024 B
 export const MAX_SIZE_IN_BYTES = 2147483648;
 
-export const getExportURL: GetExportURL = (format, dataset, __, value) => {
+export const getExportURL: GetExportURL = (
+  format,
+  dataset,
+  selection,
+  value
+) => {
   if (format === 'json') {
     return async () => {
       vscode.postMessage({
@@ -20,5 +25,62 @@ export const getExportURL: GetExportURL = (format, dataset, __, value) => {
     };
   }
 
+  if (format === 'csv') {
+    // Async function that will be called when the user clicks on a `CSV` export menu entry
+    return async () => {
+      // Generate CSV string from `value` array
+      let csv = '';
+      let dims = [];
+
+      // Record all dataset dimensions with cardinality greater than one,
+      // accounting for subset selection if applicable
+      if (selection) {
+        let subsets = selection.split(',');
+        for (let i = 0; i < subsets.length; i++) {
+          // Because of the user interface, all slices will either be
+          // the full array length or a single value
+          if (subsets[i] === ':' && dataset.shape[i] > 1) {
+            dims.push(dataset.shape[i]);
+          }
+        }
+      } else {
+        dataset.shape.forEach((val) => {
+          if (val > 1) dims.push(val);
+        });
+      }
+
+      // Only provide special handling for 2D dataset outputs
+      if (dims.length == 2) {
+        let k = 0;
+        for (let i = 0; i < dims[0]; i++) {
+          for (let j = 0; j < dims[1] - 1; j++) {
+            csv += `${value[k].toString()}, `;
+            k++;
+          }
+
+          csv += `${value[k].toString()}\n`;
+          k++;
+        }
+      } else {
+        value.forEach((val: any) => {
+          csv += `${val.toString()}\n`;
+        });
+      }
+
+      const finalCsv = csv.slice(0, -1);
+
+      vscode.postMessage({
+        type: MessageType.Export,
+        data: {
+          format,
+          name: dataset.name,
+          payload: finalCsv,
+        },
+      });
+
+      return new Blob(); // doesn't matter as long as it's not falsy
+    };
+  }
+
   return undefined;
 };