Initial commit

packages/example/src/todos/services/TodosState.ts

@@ -0,0 +1,44 @@
+import { Todo } from "@/domain"
+import { KeyValueStore } from "@effect/platform"
+import { BrowserKeyValueStore } from "@effect/platform-browser"
+import { PlatformError } from "@effect/platform/Error"
+import { Chunk, Context, Effect, identity, Layer, ParseResult, Ref, Schema, Stream, SubscriptionRef } from "effect"
+
+
+export class TodosState extends Context.Tag("TodosState")<TodosState, {
+    readonly todos: SubscriptionRef.SubscriptionRef<Chunk.Chunk<Todo.Todo>>
+    readonly load: Effect.Effect<void, PlatformError | ParseResult.ParseError>
+    readonly save: Effect.Effect<void, PlatformError | ParseResult.ParseError>
+}>() {}
+
+
+export const make = (key: string) => Layer.effect(TodosState, Effect.gen(function*() {
+    const readFromLocalStorage = KeyValueStore.KeyValueStore.pipe(
+        Effect.flatMap(kv => kv.get(key)),
+        Effect.flatMap(identity),
+        Effect.flatMap(Schema.decode(
+            Schema.compose(Schema.parseJson(), Schema.Chunk(Todo.TodoFromJson))
+        )),
+        Effect.catchTag("NoSuchElementException", () => Effect.succeed(Chunk.empty<Todo.Todo>())),
+        Effect.provide(BrowserKeyValueStore.layerLocalStorage),
+    )
+
+    const writeToLocalStorage = (values: Chunk.Chunk<Todo.Todo>) => KeyValueStore.KeyValueStore.pipe(
+        Effect.flatMap(kv => values.pipe(
+            Schema.encode(
+                Schema.compose(Schema.parseJson(), Schema.Chunk(Todo.TodoFromJson))
+            ),
+            Effect.flatMap(v => kv.set(key, v)),
+        )),
+        Effect.provide(BrowserKeyValueStore.layerLocalStorage),
+    )
+
+    const todos = yield* SubscriptionRef.make(yield* readFromLocalStorage)
+    const load = Effect.flatMap(readFromLocalStorage, v => Ref.set(todos, v))
+    const save = Effect.flatMap(todos, writeToLocalStorage)
+
+    // Sync changes with local storage
+    yield* Effect.forkScoped(Stream.runForEach(todos.changes, writeToLocalStorage))
+
+    return { todos, load, save }
+}))