Add Sync3ObservableList

package.json

@@ -58,6 +58,7 @@
     "@rollup/plugin-commonjs": "^15.0.0",
     "@rollup/plugin-json": "^4.1.0",
     "@rollup/plugin-node-resolve": "^9.0.0",
+    "@types/assert": "^1.5.6",
     "aes-js": "^3.1.2",
     "another-json": "^0.2.0",
     "base64-arraybuffer": "^0.2.0",

src/matrix/Sync3ObservableList.ts

@@ -0,0 +1,183 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import * as assert from "assert";
+import { BaseObservableList } from "../observable/list/BaseObservableList";
+import { ObservableMap } from "../observable/map/ObservableMap.js";
+import { Room } from "./room/Room.js";
+
+// subset of Sync3 functions used in this list; interfaced out for testing
+interface ISync {
+    count(): number;
+    roomAtIndex(i: number): string
+}
+
+/**
+ * An observable list that produces a subset of rooms based on Sync3 responses.
+ */
+export class Sync3ObservableList extends BaseObservableList<Room | null> {
+    sync: ISync;
+    rooms: ObservableMap;
+
+    /**
+     * Construct an observable list that produces Rooms within the sliding window of Sync3 responses
+     * or `null` to indicate that a placeholder room should be used.
+     * @param sync3 The Sync3 class, which tracks up-to-date information on the sliding window / room counts.
+     * @param rooms The entire set of rooms known to the client (e.g from Session.rooms).
+     */
+    constructor(sync3: ISync, rooms: ObservableMap) {
+        super();
+        this.sync = sync3;
+        this.rooms = rooms;
+    }
+
+    get length(): number {
+        return this.sync.count();
+    }
+
+    [Symbol.iterator](): Iterator<Room | null, any, undefined> {
+        let i = 0;
+        return {
+            next: (): any => {
+                // base case
+                if (i >= this.length) {
+                    return {
+                        done: true,
+                    };
+                }
+                let roomId = this.sync.roomAtIndex(i);
+                i += 1;
+                if (!roomId) {
+                    return {
+                        value: null
+                    }
+                }
+                return {
+                    value: this.rooms.get(roomId) || null,
+                }
+            }
+        }
+    }
+}
+
+export function tests() {
+    const makeRooms = function (len) {
+        let rooms: any[] = [];
+        for (let i = 0; i < len; i++) {
+            const roomId = "!room-" + i;
+            rooms.push({
+                id: roomId,
+                data: {
+                    some_key: i,
+                },
+            });
+        }
+        return rooms;
+    }
+
+    const assertList = function (assert, rooms, gotList, wantListRoomIds) {
+        if (wantListRoomIds.length === 0) {
+            assert.equal(gotList.length, 0);
+            for (const room of gotList) {
+                assert.equal(0, 1); // fail
+            }
+            return;
+        }
+        let i = 0;
+        for (const room of gotList) {
+            const wantRoomId = wantListRoomIds[i];
+            const gotRoomId = room ? room.id : null;
+            assert.equal(wantRoomId, gotRoomId);
+            if (wantRoomId !== null && gotRoomId !== null) {
+                assert.deepEqual(room, rooms.get(wantRoomId));
+            }
+            i += 1;
+        }
+    }
+
+    return {
+        "iterator": (assert) => {
+            const rooms = new ObservableMap();
+            let indexToRoomId = {};
+            let roomCount = 0;
+            const sync3 = {
+                count: (): number => {
+                    return roomCount;
+                },
+                roomAtIndex: (i: number): string => {
+                    return indexToRoomId[i];
+                },
+            };
+
+            makeRooms(100).forEach((r) => {
+                rooms.add(r.id, r);
+            });
+            const list = new Sync3ObservableList(sync3, rooms);
+
+            // iterate over the list (0 items) as sync3 has no indexes for the rooms
+            assertList(assert, rooms, list, []);
+
+
+            // 'load' 5 rooms from sync v3 and set the total count to 5 so we load the entire room list in one go!
+            // [R,R,R,R,R]
+            let slidingWindow: any[] = [
+                "!room-50", "!room-53", "!room-1", "!room-52", "!room-97"
+            ]
+            roomCount = 5;
+            for (let i = 0; i < slidingWindow.length; i++) {
+                indexToRoomId[i] = slidingWindow[i];
+            }
+            assertList(assert, rooms, list, slidingWindow);
+
+            // now add 5 more rooms which we don't know about, we should iterate through them with `null` entries
+            // [R,R,R,R,R,P,P,P,P,P] (R=room, P=placeholder)
+            roomCount = 10;
+            assertList(assert, rooms, list, slidingWindow.concat([null, null, null, null, null]));
+
+
+            // now track a window in the middle of the list (5-10)
+            indexToRoomId = {};
+            for (let i = 0; i < slidingWindow.length; i++) {
+                indexToRoomId[i + 5] = slidingWindow[i];
+            }
+            roomCount = 15;
+            // [P,P,P,P,P,R,R,R,R,R,P,P,P,P,P]
+            assertList(assert, rooms, list, [null, null, null, null, null].concat(slidingWindow.concat([null, null, null, null, null])));
+
+
+            // now track multiple ranges
+            const anotherSlidingWindow: any[] = [
+                "!room-30", "!room-33", "!room-36", "!room-29", "!room-21"
+            ]
+            for (let i = 0; i < anotherSlidingWindow.length; i++) {
+                indexToRoomId[i + 15] = anotherSlidingWindow[i];
+            }
+            roomCount = 20;
+            // [P,P,P,P,P,R,R,R,R,R,P,P,P,P,P,R,R,R,R,R]
+            assertList(
+                assert, rooms, list,
+                [null, null, null, null, null].concat(
+                    slidingWindow.concat(
+                        [null, null, null, null, null].concat(
+                            anotherSlidingWindow
+                        )
+                    )
+                )
+            );
+
+        },
+    };
+};

yarn.lock

@@ -1164,6 +1164,11 @@
   resolved "https://registry.yarnpkg.com/@tootallnate/once/-/once-1.1.2.tgz#ccb91445360179a04e7fe6aff78c00ffc1eeaf82"
   integrity sha512-RbzJvlNzmRq5c3O09UipeuXno4tA1FE6ikOjxZK0tuxVv3412l64l5t1W5pj4+rJq9vpkm/kwiR07aZXnsKPxw==
 
+"@types/assert@^1.5.6":
+  version "1.5.6"
+  resolved "https://registry.yarnpkg.com/@types/assert/-/assert-1.5.6.tgz#a8b5a94ce5fb8f4ba65fdc37fc9507609114189e"
+  integrity sha512-Y7gDJiIqb9qKUHfBQYOWGngUpLORtirAVPuj/CWJrU2C6ZM4/y3XLwuwfGMF8s7QzW746LQZx23m0+1FSgjfug==
+
 "@types/cacheable-request@^6.0.1":
   version "6.0.2"
   resolved "https://registry.yarnpkg.com/@types/cacheable-request/-/cacheable-request-6.0.2.tgz#c324da0197de0a98a2312156536ae262429ff6b9"