Complete refactor (#123)

src/app/state/LocalStorageProperty.ts

@@ -0,0 +1,14 @@
+import { Property } from './Property'
+
+export class LocalStorageProperty extends Property<string> {
+  constructor(private id: string, fallback: string) {
+    super(localStorage.getItem(id) ?? fallback)
+  }
+  set(value: string) {
+    super.set(value)
+    localStorage.setItem(this.id, value)
+  }
+  get(): string {
+    return this.value
+  }
+}

src/app/state/Property.ts

@@ -0,0 +1,40 @@
+import { hexId } from "../Utils"
+
+type PropertyWatcher<T> = (value: T, oldValue: T | null) => void
+type NamedPropertyWatcher<T> = {
+  name: string
+  watcher: PropertyWatcher<T>
+}
+
+export class Property<T> {
+  private watchers: NamedPropertyWatcher<T>[] = []
+
+  constructor(public value: T) {}
+
+  set(value: T) {
+    if (this.value === value) return
+    const oldValue = this.value
+    this.value = value
+    this.watchers.forEach(w => w.watcher(this.value, oldValue))
+  }
+
+  get(): T {
+    return this.value
+  }
+
+  watchRun(watcher: PropertyWatcher<T>, name?: string) {
+    watcher(this.value, null)
+    return this.watch(watcher, name)
+  }
+
+  watch(watcher: PropertyWatcher<T>, name?: string) {
+    name = name ?? hexId()
+    const w = this.watchers.find(w => w.name === name)
+    if (w) {
+      w.watcher = watcher
+    } else {
+      this.watchers.push({ name, watcher })
+    }
+    return this
+  }
+}