move observable values each in their own file

src/domain/navigation/Navigation.js

@@ -14,7 +14,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableValue, ObservableValue} from "../../observable/ObservableValue";
+import {ObservableValue} from "../../observable/value/ObservableValue";
+import {BaseObservableValue} from "../../observable/value/BaseObservableValue";
 
 export class Navigation {
     constructor(allowsChild) {

src/domain/session/RoomGridViewModel.js

@@ -186,7 +186,7 @@ export class RoomGridViewModel extends ViewModel {
 }
 
 import {createNavigation} from "../navigation/index.js";
-import {ObservableValue} from "../../observable/ObservableValue";
+import {ObservableValue} from "../../observable/value/ObservableValue";
 
 export function tests() { 
     class RoomVMMock {

src/domain/session/RoomViewModelObservable.js

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {ObservableValue} from "../../observable/ObservableValue";
+import {ObservableValue} from "../../observable/value/ObservableValue";
 import {RoomStatus} from "../../matrix/room/common";
 
 /**

src/domain/session/room/timeline/ReactionsViewModel.js

@@ -189,7 +189,7 @@ import {HomeServer as MockHomeServer} from "../../../../mocks/HomeServer.js";
 // other imports
 import {BaseMessageTile} from "./tiles/BaseMessageTile.js";
 import {MappedList} from "../../../../observable/list/MappedList";
-import {ObservableValue} from "../../../../observable/ObservableValue";
+import {ObservableValue} from "../../../../observable/value/ObservableValue";
 import {PowerLevels} from "../../../../matrix/room/PowerLevels.js";
 
 export function tests() {

src/domain/session/settings/KeyBackupViewModel.js

@@ -17,6 +17,7 @@ limitations under the License.
 import {ViewModel} from "../../ViewModel";
 import {KeyType} from "../../../matrix/ssss/index";
 import {createEnum} from "../../../utils/enum";
+import {FlatMapObservableValue} from "../../../observable/value/FlatMapObservableValue";
 
 export const Status = createEnum("Enabled", "SetupKey", "SetupPhrase", "Pending", "NewVersionAvailable"); 
 export const BackupWriteStatus = createEnum("Writing", "Stopped", "Done", "Pending"); 
@@ -29,8 +30,8 @@ export class KeyBackupViewModel extends ViewModel {
         this._isBusy = false;
         this._dehydratedDeviceId = undefined;
         this._status = undefined;
-        this._backupOperation = this._session.keyBackup.flatMap(keyBackup => keyBackup.operationInProgress);
+        this._backupOperation = new FlatMapObservableValue(this._session.keyBackup, keyBackup => keyBackup.operationInProgress);
-        this._progress = this._backupOperation.flatMap(op => op.progress);
+        this._progress = new FlatMapObservableValue(this._backupOperation, op => op.progress);
         this.track(this._backupOperation.subscribe(() => {
             // see if needsNewKey might be set
             this._reevaluateStatus();

src/lib.ts

@@ -46,8 +46,6 @@ export {
     ConcatList,
     ObservableMap
 } from "./observable/index";
-export {
+export {BaseObservableValue} from "./observable/value/BaseObservableValue";
-    BaseObservableValue,
+export {ObservableValue} from "./observable/value/ObservableValue";
-    ObservableValue,
+export {RetainedObservableValue} from "./observable/value/RetainedObservableValue";
-    RetainedObservableValue
-} from "./observable/ObservableValue";

src/matrix/Client.js

@@ -18,7 +18,7 @@ limitations under the License.
 import {createEnum} from "../utils/enum";
 import {lookupHomeserver} from "./well-known.js";
 import {AbortableOperation} from "../utils/AbortableOperation";
-import {ObservableValue} from "../observable/ObservableValue";
+import {ObservableValue} from "../observable/value/ObservableValue";
 import {HomeServerApi} from "./net/HomeServerApi";
 import {Reconnector, ConnectionStatus} from "./net/Reconnector";
 import {ExponentialRetryDelay} from "./net/ExponentialRetryDelay";

src/matrix/Session.js

@@ -45,7 +45,8 @@ import {
     keyFromDehydratedDeviceKey as createSSSSKeyFromDehydratedDeviceKey
 } from "./ssss/index";
 import {SecretStorage} from "./ssss/SecretStorage";
-import {ObservableValue, RetainedObservableValue} from "../observable/ObservableValue";
+import {ObservableValue} from "../observable/value/ObservableValue";
+import {RetainedObservableValue} from "../observable/value/RetainedObservableValue";
 
 const PICKLE_KEY = "DEFAULT_KEY";
 const PUSHER_KEY = "pusher";
@@ -997,9 +998,18 @@ export function tests() {
 
     return {
         "session data is not modified until after sync": async (assert) => {
-            const session = new Session({storage: createStorageMock({
+            const storage = createStorageMock({
                 sync: {token: "a", filterId: 5}
-            }), sessionInfo: {userId: ""}});
+            });
+            const session = new Session({
+                storage,
+                sessionInfo: {userId: ""},
+                platform: {
+                    clock: {
+                        createTimeout: () => undefined
+                    }
+                }
+            });
             await session.load();
             let syncSet = false;
             const syncTxn = {

src/matrix/Sync.js

@@ -15,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {ObservableValue} from "../observable/ObservableValue";
+import {ObservableValue} from "../observable/value/ObservableValue";
 import {createEnum} from "../utils/enum";
 
 const INCREMENTAL_TIMEOUT = 30000;

src/matrix/e2ee/megolm/keybackup/KeyBackup.ts

@@ -19,7 +19,7 @@ import {StoredRoomKey, keyFromBackup} from "../decryption/RoomKey";
 import {MEGOLM_ALGORITHM} from "../../common";
 import * as Curve25519 from "./Curve25519";
 import {AbortableOperation} from "../../../../utils/AbortableOperation";
-import {ObservableValue} from "../../../../observable/ObservableValue";
+import {ObservableValue} from "../../../../observable/value/ObservableValue";
 
 import {SetAbortableFn} from "../../../../utils/AbortableOperation";
 import type {BackupInfo, SessionData, SessionKeyInfo, SessionInfo, KeyBackupPayload} from "./types";

src/matrix/net/Reconnector.ts

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {ObservableValue} from "../../observable/ObservableValue";
+import {ObservableValue} from "../../observable/value/ObservableValue";
 import type {ExponentialRetryDelay} from "./ExponentialRetryDelay";
 import type {TimeMeasure} from "../../platform/web/dom/Clock.js";
 import type {OnlineStatus} from "../../platform/web/dom/OnlineStatus.js";

src/matrix/room/BaseRoom.js

@@ -29,7 +29,7 @@ import {ObservedEventMap} from "./ObservedEventMap.js";
 import {DecryptionSource} from "../e2ee/common.js";
 import {ensureLogItem} from "../../logging/utils";
 import {PowerLevels} from "./PowerLevels.js";
-import {RetainedObservableValue} from "../../observable/ObservableValue";
+import {RetainedObservableValue} from "../../observable/value/RetainedObservableValue";
 import {TimelineReader} from "./timeline/persistence/TimelineReader";
 
 const EVENT_ENCRYPTED_TYPE = "m.room.encrypted";

src/matrix/room/ObservedEventMap.js

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableValue} from "../../observable/ObservableValue";
+import {BaseObservableValue} from "../../observable/value/BaseObservableValue";
 
 export class ObservedEventMap {
     constructor(notifyEmpty) {

src/mocks/Clock.js

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {ObservableValue} from "../observable/ObservableValue";
+import {ObservableValue} from "../observable/value/ObservableValue";
 
 class Timeout {
     constructor(elapsed, ms) {

src/observable/ObservableValue.ts

@@ -1,248 +0,0 @@
-/*
-Copyright 2020 Bruno Windels <bruno@windels.cloud>
-
-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 {AbortError} from "../utils/error";
-import {BaseObservable} from "./BaseObservable";
-import type {SubscriptionHandle} from "./BaseObservable";
-
-// like an EventEmitter, but doesn't have an event type
-export abstract class BaseObservableValue<T> extends BaseObservable<(value: T) => void> {
-    emit(argument: T) {
-        for (const h of this._handlers) {
-            h(argument);
-        }
-    }
-
-    abstract get(): T;
-
-    waitFor(predicate: (value: T) => boolean): IWaitHandle<T> {
-        if (predicate(this.get())) {
-            return new ResolvedWaitForHandle(Promise.resolve(this.get()));
-        } else {
-            return new WaitForHandle(this, predicate);
-        }
-    }
-
-    flatMap<C>(mapper: (value: T) => (BaseObservableValue<C> | undefined)): BaseObservableValue<C | undefined> {
-        return new FlatMapObservableValue<T, C>(this, mapper);
-    }
-}
-
-interface IWaitHandle<T> {
-    promise: Promise<T>;
-    dispose(): void;
-}
-
-class WaitForHandle<T> implements IWaitHandle<T> {
-    private _promise: Promise<T>
-    private _reject: ((reason?: any) => void) | null;
-    private _subscription: (() => void) | null;
-
-    constructor(observable: BaseObservableValue<T>, predicate: (value: T) => boolean) {
-        this._promise = new Promise((resolve, reject) => {
-            this._reject = reject;
-            this._subscription = observable.subscribe(v => {
-                if (predicate(v)) {
-                    this._reject = null;
-                    resolve(v);
-                    this.dispose();
-                }
-            });
-        });
-    }
-
-    get promise(): Promise<T> {
-        return this._promise;
-    }
-
-    dispose() {
-        if (this._subscription) {
-            this._subscription();
-            this._subscription = null;
-        }
-        if (this._reject) {
-            this._reject(new AbortError());
-            this._reject = null;
-        }
-    }
-}
-
-class ResolvedWaitForHandle<T> implements IWaitHandle<T> {
-    constructor(public promise: Promise<T>) {}
-    dispose() {}
-}
-
-export class ObservableValue<T> extends BaseObservableValue<T> {
-    private _value: T;
-
-    constructor(initialValue: T) {
-        super();
-        this._value = initialValue;
-    }
-
-    get(): T {
-        return this._value;
-    }
-
-    set(value: T): void {
-        if (value !== this._value) {
-            this._value = value;
-            this.emit(this._value);
-        }
-    }
-}
-
-export class RetainedObservableValue<T> extends ObservableValue<T> {
-    private _freeCallback: () => void;
-
-    constructor(initialValue: T, freeCallback: () => void) {
-        super(initialValue);
-        this._freeCallback = freeCallback;
-    }
-
-    onUnsubscribeLast() {
-        super.onUnsubscribeLast();
-        this._freeCallback();
-    }
-}
-
-export class FlatMapObservableValue<P, C> extends BaseObservableValue<C | undefined> {
-    private sourceSubscription?: SubscriptionHandle;
-    private targetSubscription?: SubscriptionHandle;
-
-    constructor(
-        private readonly source: BaseObservableValue<P>,
-        private readonly mapper: (value: P) => (BaseObservableValue<C> | undefined)
-    ) {
-        super();
-    }
-
-    onUnsubscribeLast() {
-        super.onUnsubscribeLast();
-        this.sourceSubscription = this.sourceSubscription!();
-        if (this.targetSubscription) {
-            this.targetSubscription = this.targetSubscription();
-        }
-    }
-
-    onSubscribeFirst() {
-        super.onSubscribeFirst();
-        this.sourceSubscription = this.source.subscribe(() => {
-            this.updateTargetSubscription();
-            this.emit(this.get());
-        });
-        this.updateTargetSubscription();
-    }
-
-    private updateTargetSubscription() {
-        const sourceValue = this.source.get();
-        if (sourceValue) {
-            const target = this.mapper(sourceValue);
-            if (target) {
-                if (!this.targetSubscription) {
-                    this.targetSubscription = target.subscribe(() => this.emit(this.get()));
-                }
-                return;
-            }
-        }
-        // if no sourceValue or target
-        if (this.targetSubscription) {
-            this.targetSubscription = this.targetSubscription();
-        }
-    }
-
-    get(): C | undefined {
-        const sourceValue = this.source.get();
-        if (!sourceValue) {
-            return undefined;
-        }
-        const mapped = this.mapper(sourceValue);
-        return mapped?.get();
-    }
-}
-
-export function tests() {
-    return {
-        "set emits an update": assert => {
-            const a = new ObservableValue<number>(0);
-            let fired = false;
-            const subscription = a.subscribe(v => {
-                fired = true;
-                assert.strictEqual(v, 5);
-            });
-            a.set(5);
-            assert(fired);
-            subscription();
-        },
-        "set doesn't emit if value hasn't changed": assert => {
-            const a = new ObservableValue(5);
-            let fired = false;
-            const subscription = a.subscribe(() => {
-                fired = true;
-            });
-            a.set(5);
-            a.set(5);
-            assert(!fired);
-            subscription();
-        },
-        "waitFor promise resolves on matching update": async assert => {
-            const a = new ObservableValue(5);
-            const handle = a.waitFor(v => v === 6);
-            Promise.resolve().then(() => {
-                a.set(6);
-            });
-            await handle.promise;
-            assert.strictEqual(a.get(), 6);
-        },
-        "waitFor promise rejects when disposed": async assert => {
-            const a = new ObservableValue<number>(0);
-            const handle = a.waitFor(() => false);
-            Promise.resolve().then(() => {
-                handle.dispose();
-            });
-            await assert.rejects(handle.promise, AbortError);
-        },
-        "flatMap.get": assert => {
-            const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
-            const countProxy = a.flatMap(a => a!.count);
-            assert.strictEqual(countProxy.get(), undefined);
-            const count = new ObservableValue<number>(0);
-            a.set({count});
-            assert.strictEqual(countProxy.get(), 0);
-        },
-        "flatMap update from source": assert => {
-            const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
-            const updates: (number | undefined)[] = [];
-            a.flatMap(a => a!.count).subscribe(count => {
-                updates.push(count);
-            });
-            const count = new ObservableValue<number>(0);
-            a.set({count});
-            assert.deepEqual(updates, [0]);
-        },
-        "flatMap update from target": assert => {
-            const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
-            const updates: (number | undefined)[] = [];
-            a.flatMap(a => a!.count).subscribe(count => {
-                updates.push(count);
-            });
-            const count = new ObservableValue<number>(0);
-            a.set({count});
-            count.set(5);
-            assert.deepEqual(updates, [0, 5]);
-        }
-    }
-}

src/observable/value/BaseObservableValue.ts

@@ -0,0 +1,83 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+
+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 {AbortError} from "../../utils/error";
+import {BaseObservable} from "../BaseObservable";
+import type {SubscriptionHandle} from "../BaseObservable";
+import {FlatMapObservableValue} from "./FlatMapObservableValue";
+
+// like an EventEmitter, but doesn't have an event type
+export abstract class BaseObservableValue<T> extends BaseObservable<(value: T) => void> {
+    emit(argument: T) {
+        for (const h of this._handlers) {
+            h(argument);
+        }
+    }
+
+    abstract get(): T;
+
+    waitFor(predicate: (value: T) => boolean): IWaitHandle<T> {
+        if (predicate(this.get())) {
+            return new ResolvedWaitForHandle(Promise.resolve(this.get()));
+        } else {
+            return new WaitForHandle(this, predicate);
+        }
+    }
+}
+
+interface IWaitHandle<T> {
+    promise: Promise<T>;
+    dispose(): void;
+}
+
+class WaitForHandle<T> implements IWaitHandle<T> {
+    private _promise: Promise<T>
+    private _reject: ((reason?: any) => void) | null;
+    private _subscription: (() => void) | null;
+
+    constructor(observable: BaseObservableValue<T>, predicate: (value: T) => boolean) {
+        this._promise = new Promise((resolve, reject) => {
+            this._reject = reject;
+            this._subscription = observable.subscribe(v => {
+                if (predicate(v)) {
+                    this._reject = null;
+                    resolve(v);
+                    this.dispose();
+                }
+            });
+        });
+    }
+
+    get promise(): Promise<T> {
+        return this._promise;
+    }
+
+    dispose() {
+        if (this._subscription) {
+            this._subscription();
+            this._subscription = null;
+        }
+        if (this._reject) {
+            this._reject(new AbortError());
+            this._reject = null;
+        }
+    }
+}
+
+class ResolvedWaitForHandle<T> implements IWaitHandle<T> {
+    constructor(public promise: Promise<T>) {}
+    dispose() {}
+}

src/observable/value/FlatMapObservableValue.ts

@@ -0,0 +1,109 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+
+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 {BaseObservableValue} from "./BaseObservableValue";
+import {SubscriptionHandle} from "../BaseObservable";
+
+export class FlatMapObservableValue<P, C> extends BaseObservableValue<C | undefined> {
+    private sourceSubscription?: SubscriptionHandle;
+    private targetSubscription?: SubscriptionHandle;
+
+    constructor(
+        private readonly source: BaseObservableValue<P>,
+        private readonly mapper: (value: P) => (BaseObservableValue<C> | undefined)
+    ) {
+        super();
+    }
+
+    onUnsubscribeLast() {
+        super.onUnsubscribeLast();
+        this.sourceSubscription = this.sourceSubscription!();
+        if (this.targetSubscription) {
+            this.targetSubscription = this.targetSubscription();
+        }
+    }
+
+    onSubscribeFirst() {
+        super.onSubscribeFirst();
+        this.sourceSubscription = this.source.subscribe(() => {
+            this.updateTargetSubscription();
+            this.emit(this.get());
+        });
+        this.updateTargetSubscription();
+    }
+
+    private updateTargetSubscription() {
+        const sourceValue = this.source.get();
+        if (sourceValue) {
+            const target = this.mapper(sourceValue);
+            if (target) {
+                if (!this.targetSubscription) {
+                    this.targetSubscription = target.subscribe(() => this.emit(this.get()));
+                }
+                return;
+            }
+        }
+        // if no sourceValue or target
+        if (this.targetSubscription) {
+            this.targetSubscription = this.targetSubscription();
+        }
+    }
+
+    get(): C | undefined {
+        const sourceValue = this.source.get();
+        if (!sourceValue) {
+            return undefined;
+        }
+        const mapped = this.mapper(sourceValue);
+        return mapped?.get();
+    }
+}
+
+import {ObservableValue} from "./ObservableValue";
+
+export function tests() {
+    return {
+        "flatMap.get": assert => {
+            const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
+            const countProxy = new FlatMapObservableValue(a, a => a!.count);
+            assert.strictEqual(countProxy.get(), undefined);
+            const count = new ObservableValue<number>(0);
+            a.set({count});
+            assert.strictEqual(countProxy.get(), 0);
+        },
+        "flatMap update from source": assert => {
+            const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
+            const updates: (number | undefined)[] = [];
+            new FlatMapObservableValue(a, a => a!.count).subscribe(count => {
+                updates.push(count);
+            });
+            const count = new ObservableValue<number>(0);
+            a.set({count});
+            assert.deepEqual(updates, [0]);
+        },
+        "flatMap update from target": assert => {
+            const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
+            const updates: (number | undefined)[] = [];
+            new FlatMapObservableValue(a, a => a!.count).subscribe(count => {
+                updates.push(count);
+            });
+            const count = new ObservableValue<number>(0);
+            a.set({count});
+            count.set(5);
+            assert.deepEqual(updates, [0, 5]);
+        }
+    }
+}

src/observable/value/ObservableValue.ts

@@ -0,0 +1,82 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+
+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 {AbortError} from "../../utils/error";
+import {BaseObservableValue} from "./BaseObservableValue";
+
+export class ObservableValue<T> extends BaseObservableValue<T> {
+    private _value: T;
+
+    constructor(initialValue: T) {
+        super();
+        this._value = initialValue;
+    }
+
+    get(): T {
+        return this._value;
+    }
+
+    set(value: T): void {
+        if (value !== this._value) {
+            this._value = value;
+            this.emit(this._value);
+        }
+    }
+}
+
+export function tests() {
+    return {
+        "set emits an update": assert => {
+            const a = new ObservableValue<number>(0);
+            let fired = false;
+            const subscription = a.subscribe(v => {
+                fired = true;
+                assert.strictEqual(v, 5);
+            });
+            a.set(5);
+            assert(fired);
+            subscription();
+        },
+        "set doesn't emit if value hasn't changed": assert => {
+            const a = new ObservableValue(5);
+            let fired = false;
+            const subscription = a.subscribe(() => {
+                fired = true;
+            });
+            a.set(5);
+            a.set(5);
+            assert(!fired);
+            subscription();
+        },
+        "waitFor promise resolves on matching update": async assert => {
+            const a = new ObservableValue(5);
+            const handle = a.waitFor(v => v === 6);
+            Promise.resolve().then(() => {
+                a.set(6);
+            });
+            await handle.promise;
+            assert.strictEqual(a.get(), 6);
+        },
+        "waitFor promise rejects when disposed": async assert => {
+            const a = new ObservableValue<number>(0);
+            const handle = a.waitFor(() => false);
+            Promise.resolve().then(() => {
+                handle.dispose();
+            });
+            await assert.rejects(handle.promise, AbortError);
+        }
+    }
+}

src/observable/value/PickMapObservable.ts

@@ -0,0 +1,89 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+
+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 {BaseObservableValue} from "./BaseObservableValue";
+import {BaseObservableMap, IMapObserver} from "../map/BaseObservableMap";
+import {SubscriptionHandle} from "../BaseObservable";
+
+function pickLowestKey<K>(currentKey: K, newKey: K): boolean {
+    return newKey < currentKey;
+}
+
+export class PickMapObservable<K, V> implements IMapObserver<K, V> extends BaseObservableValue<V | undefined> {
+
+    private key?: K;
+    private mapSubscription?: SubscriptionHandle;
+
+    constructor(
+        private readonly map: BaseObservableMap<K, V>,
+        private readonly pickKey: (currentKey: K, newKey: K) => boolean = pickLowestKey
+    ) {
+        super();
+    }
+
+    private trySetKey(newKey: K): boolean {
+        if (this.key === undefined || this.pickKey(this.key, newKey)) {
+            this.key = newKey;
+            return true;
+        }
+        return false;
+    }
+
+    onReset(): void {
+        this.key = undefined;
+        this.emit(this.get());
+    }
+
+    onAdd(key: K, value:V): void {
+        if (this.trySetKey(key)) {
+            this.emit(this.get());
+        }
+    }
+
+    onUpdate(key: K, value: V, params: any): void {}
+
+    onRemove(key: K, value: V): void {
+        if (key === this.key) {
+            this.key = undefined;
+            let changed = false;
+            for (const [key] of this.map) {
+                changed = this.trySetKey(key) || changed;
+            }
+            if (changed) {
+                this.emit(this.get());
+            }
+        }
+    }
+
+    onSubscribeFirst(): void {
+        this.mapSubscription = this.map.subscribe(this);
+        for (const [key] of this.map) {
+            this.trySetKey(key);
+        }
+    }
+
+    onUnsubscribeLast(): void {
+        this.mapSubscription();
+        this.key = undefined;
+    }
+
+    get(): V | undefined {
+        if (this.key !== undefined) {
+            return this.map.get(this.key);
+        }
+        return undefined;
+    }
+}

src/observable/value/RetainedObservableValue.ts

@@ -0,0 +1,31 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+
+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 {ObservableValue} from "./ObservableValue";
+
+export class RetainedObservableValue<T> extends ObservableValue<T> {
+    private _freeCallback: () => void;
+
+    constructor(initialValue: T, freeCallback: () => void) {
+        super(initialValue);
+        this._freeCallback = freeCallback;
+    }
+
+    onUnsubscribeLast() {
+        super.onUnsubscribeLast();
+        this._freeCallback();
+    }
+}

src/platform/web/dom/History.js

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableValue} from "../../../observable/ObservableValue";
+import {BaseObservableValue} from "../../../observable/value/BaseObservableValue";
 
 export class History extends BaseObservableValue {
     handleEvent(event) {

src/platform/web/dom/OnlineStatus.js

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableValue} from "../../../observable/ObservableValue";
+import {BaseObservableValue} from "../../../observable/value/BaseObservableValue";
 
 export class OnlineStatus extends BaseObservableValue {
     constructor() {

src/utils/AbortableOperation.ts

@@ -14,7 +14,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableValue, ObservableValue} from "../observable/ObservableValue";
+import {BaseObservableValue} from "../observable/value/BaseObservableValue";
+import {ObservableValue} from "../observable/value/ObservableValue";
 
 export interface IAbortable {
     abort();