PouchDB snapshot implementation

packages/code-studio/src/console/command-history/CommandHistory.jsx

@@ -156,30 +156,23 @@ class CommandHistory extends Component {
    * If they're not within the current viewport, will fetch them from the table
    * @returns {Promise<string[]>} Array of selected commands
    */
-  getSelectedCommands() {
+  async getSelectedCommands() {
     const { items, offset, selectedRanges } = this.state;
     const ranges = selectedRanges.slice().sort((a, b) => a[0] - b[0]);
 
-    return this.pending.add(
-      new Promise((resolve, reject) => {
-        if (ranges.length === 0) {
-          resolve([]);
-        } else if (
-          ranges[0][0] >= offset &&
-          ranges[ranges.length - 1][1] < offset + items.length
-        ) {
-          // All ranges are in the current viewport, just copy the data we've already got
-          resolve(
-            CommandHistory.getCommandsFromViewport(items, offset, ranges)
-          );
-        } else {
-          // TODO: core#376 Allow copying outside of current viewport
-          reject(
-            new Error('Unable to copy commands outside of current viewport')
-          );
-        }
-      })
-    );
+    if (ranges.length === 0) {
+      return [];
+    }
+    if (
+      ranges[0][0] >= offset &&
+      ranges[ranges.length - 1][1] < offset + items.length
+    ) {
+      // All ranges are in the current viewport, just copy the data we've already got
+      return CommandHistory.getCommandsFromViewport(items, offset, ranges);
+    }
+    const { table } = this.props;
+    const snapshot = await this.pending.add(table.getSnapshot(ranges));
+    return [...snapshot.added].map(index => snapshot.get(index)?.name ?? '');
   }
 
   /**
@@ -353,7 +346,10 @@ CommandHistory.propTypes = {
   language: PropTypes.string.isRequired,
   sendToConsole: PropTypes.func.isRequired,
   sendToNotebook: PropTypes.func.isRequired,
-  table: PropTypes.shape({ size: PropTypes.number }).isRequired,
+  table: PropTypes.shape({
+    size: PropTypes.number,
+    getSnapshot: PropTypes.func.isRequired,
+  }).isRequired,
 };
 
 export default CommandHistory;

packages/code-studio/src/console/command-history/PouchStorageTable.ts

@@ -11,6 +11,7 @@ import {
   StorageTableListener,
   StorageItemSuccessErrorListener,
   StorageItemSuccessListener,
+  StorageSnapshot,
 } from './StorageTable';
 
 const log = Log.module('PouchStorageTable');
@@ -252,6 +253,58 @@ export class PouchStorageTable<T extends StorageItem = StorageItem>
 
     return item;
   }
+
+  async getSnapshot(
+    sortedRanges: [number, number][]
+  ): Promise<StorageSnapshot<T>> {
+    if (!this.currentViewport) {
+      throw new Error('Viewport not set');
+    }
+    const { currentViewport: viewport } = this;
+
+    const itemMap: Map<number, T> = new Map();
+    const indexes: number[] = [];
+    let lastIndex = -1;
+
+    await Promise.all(
+      sortedRanges.map(async ([from, to]) => {
+        const limit = to - from + 1;
+        return this.db
+          .find({
+            selector: selectorWithSearch(viewport.search),
+            skip: from,
+            limit,
+            sort: this.sort,
+            fields: ['id', 'name'],
+          })
+          .then(findSnapshotResult => {
+            for (let i = 0; i < limit; i += 1) {
+              const index = from + i;
+              indexes.push(index);
+              itemMap.set(index, findSnapshotResult.docs[i]);
+            }
+          });
+      })
+    );
+
+    function iterator() {
+      return {
+        hasNext: () => lastIndex + 1 < indexes.length,
+        next: () => {
+          lastIndex += 1;
+          return {
+            value: indexes[lastIndex],
+            done: lastIndex >= indexes.length,
+          };
+        },
+      };
+    }
+
+    return {
+      added: { [Symbol.iterator]: iterator },
+      get: (index: number) => itemMap.get(index),
+    };
+  }
 }
 
 export default PouchStorageTable;

packages/code-studio/src/console/command-history/StorageTable.ts

@@ -36,6 +36,11 @@ export type StorageTableListener = () => void;
 
 export type StorageListenerRemover = () => void;
 
+export type StorageSnapshot<T> = {
+  added: Iterable<number>;
+  get(index: number): T | undefined;
+};
+
 /**
  * A table for getting a list of items from storage, with id/name pairs
  * Can search the table with a case insensitive search
@@ -57,6 +62,7 @@ export interface StorageTable<T extends StorageItem = StorageItem> {
     id: string,
     listener: StorageItemListener<T>
   ): StorageListenerRemover;
+  getSnapshot(sortedRanges: [number, number][]): Promise<StorageSnapshot<T>>;
   close(): void;
 }