Files
effect-fc/packages/example/src/todo/TodosState.ts
Julien Valverdé 1dc28ce8c6
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Fix example
2026-04-29 18:02:10 +02:00

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TypeScript

import { KeyValueStore } from "@effect/platform"
import { BrowserKeyValueStore } from "@effect/platform-browser"
import { Chunk, Console, Effect, Option, Schema, Stream, SubscriptionRef } from "effect"
import { Lens, Subscribable } from "effect-fc"
import { Todo } from "@/domain"
export class TodosState extends Effect.Service<TodosState>()("TodosState", {
scoped: Effect.fnUntraced(function*(key: string) {
const kv = yield* KeyValueStore.KeyValueStore
const readFromLocalStorage = Console.log("Reading todos from local storage...").pipe(
Effect.andThen(kv.get(key)),
Effect.andThen(Option.match({
onSome: Schema.decode(
Schema.parseJson(Schema.Chunk(Todo.TodoFromJson))
),
onNone: () => Effect.succeed(Chunk.empty()),
}))
)
const saveToLocalStorage = (todos: Chunk.Chunk<Todo.Todo>) => Effect.andThen(
Console.log("Saving todos to local storage..."),
Chunk.isNonEmpty(todos)
? Effect.andThen(
Schema.encode(
Schema.parseJson(Schema.Chunk(Todo.TodoFromJson))
)(todos),
v => kv.set(key, v),
)
: kv.remove(key)
)
const lens = Lens.fromSubscriptionRef(yield* SubscriptionRef.make(yield* readFromLocalStorage))
yield* Effect.forkScoped(lens.changes.pipe(
Stream.debounce("500 millis"),
Stream.runForEach(saveToLocalStorage),
))
yield* Effect.addFinalizer(() => Lens.get(lens).pipe(
Effect.andThen(saveToLocalStorage),
Effect.ignore,
))
const sizeSubscribable = Subscribable.map(lens, Chunk.size)
const getElementLens = (id: string) => Lens.mapEffect(
lens,
Chunk.findFirst(v => v.id === id),
(a, b) => Effect.flatMap(
Chunk.findFirstIndex(a, v => v.id === id),
i => Chunk.replaceOption(a, i, b),
)
)
const getIndexSubscribable = (id: string) => Subscribable.mapEffect(lens, Chunk.findFirstIndex(v => v.id === id))
const moveLeft = (id: string) => Lens.updateEffect(lens, todos => Effect.Do.pipe(
Effect.bind("index", () => Chunk.findFirstIndex(todos, v => v.id === id)),
Effect.bind("todo", ({ index }) => Chunk.get(todos, index)),
Effect.bind("previous", ({ index }) => Chunk.get(todos, index - 1)),
Effect.andThen(({ todo, index, previous }) => index > 0
? todos.pipe(
Chunk.replace(index, previous),
Chunk.replace(index - 1, todo),
)
: todos
),
))
const moveRight = (id: string) => Lens.updateEffect(lens, todos => Effect.Do.pipe(
Effect.bind("index", () => Chunk.findFirstIndex(todos, v => v.id === id)),
Effect.bind("todo", ({ index }) => Chunk.get(todos, index)),
Effect.bind("next", ({ index }) => Chunk.get(todos, index + 1)),
Effect.andThen(({ todo, index, next }) => index < Chunk.size(todos) - 1
? todos.pipe(
Chunk.replace(index, next),
Chunk.replace(index + 1, todo),
)
: todos
),
))
const remove = (id: string) => Lens.updateEffect(lens, todos => Effect.andThen(
Chunk.findFirstIndex(todos, v => v.id === id),
index => Chunk.remove(todos, index),
))
return {
lens,
sizeSubscribable,
getElementLens,
getIndexSubscribable,
moveLeft,
moveRight,
remove,
} as const
}),
dependencies: [BrowserKeyValueStore.layerLocalStorage],
}) {}