effect-view/packages/effect-fc/src/Lens.ts

import { Chunk, Effect, Function, Pipeable, Predicate, Readable, Stream, Subscribable, SubscriptionRef } from "effect"


export const LensTypeId: unique symbol = Symbol.for("@effect-fc/Lens/Lens")
export type LensTypeId = typeof LensTypeId

export interface Lens<in out A, in out ER = never, in out EW = never, in out RR = never, in out RW = never>
extends Subscribable.Subscribable<A, ER, RR> {
    readonly [LensTypeId]: LensTypeId

    readonly modify: <B, E1 = never, R1 = never>(
        f: (a: A) => Effect.Effect<readonly [B, A], E1, R1>
    ) => Effect.Effect<B, ER | EW | E1, RR | RW | R1>
}

export class LensImpl<in out A, in out ER = never, in out EW = never, in out RR = never, in out RW = never>
    extends Pipeable.Class() implements Lens<A, ER, EW, RR, RW> {
    readonly [Readable.TypeId]: Readable.TypeId = Readable.TypeId
    readonly [Subscribable.TypeId]: Subscribable.TypeId = Subscribable.TypeId
    readonly [LensTypeId]: LensTypeId = LensTypeId

    constructor(
        readonly get: Effect.Effect<A, ER, RR>,
        readonly changes: Stream.Stream<A, ER, RR>,
        readonly modify: <B, E1 = never, R1 = never>(
            f: (a: A) => Effect.Effect<readonly [B, A], E1, R1>
        ) => Effect.Effect<B, ER | EW | E1, RR | RW | R1>,
    ) {
        super()
    }
}


export const isLens = (u: unknown): u is Lens<unknown, unknown, unknown, unknown, unknown> => Predicate.hasProperty(u, LensTypeId)


export const make = <A, ER, EW, RR, RW>(
    options: {
        readonly get: Effect.Effect<A, ER, RR>
        readonly changes: Stream.Stream<A, ER, RR>
    } & (
        | {
            readonly modify: <B, E1 = never, R1 = never>(
                f: (a: A) => Effect.Effect<readonly [B, A], E1, R1>
            ) => Effect.Effect<B, ER | EW | E1, RR | RW | R1>
        }
        | { readonly set: (a: A) => Effect.Effect<void, EW, RW> }
    )
): Lens<A, ER, EW, RR, RW> => new LensImpl<A, ER, EW, RR, RW>(
    options.get,
    options.changes,
    Predicate.hasProperty(options, "modify")
        ? options.modify
        : <B, E1 = never, R1 = never>(
            f: (a: A) => Effect.Effect<readonly [B, A], E1, R1>
        ) => Effect.flatMap(
            options.get,
            a => Effect.flatMap(f(a), ([b, next]) => Effect.as(options.set(next), b)
        )),
)

/**
 * Creates a `Lens` that directly proxies a `SubscriptionRef`.
 */
export const fromSubscriptionRef = <A>(
    ref: SubscriptionRef.SubscriptionRef<A>
): Lens<A, never, never, never, never> => make({
    get get() { return ref.get },
    get changes() { return ref.changes },
    modify: ref.modifyEffect.bind(ref), // TODO
})

export const unwrap = <A, ER, EW, RR, RW, E1, R1>(
    effect: Effect.Effect<Lens<A, ER, EW, RR, RW>, E1, R1>
): Lens<A, ER | E1, EW | E1, RR | R1, RW | R1> => make({
    get: Effect.flatMap(effect, l => l.get),
    changes: Stream.unwrap(Effect.map(effect, l => l.changes)),
    modify: <B, E2 = never, R2 = never>(
        f: (a: A) => Effect.Effect<readonly [B, A], E2, R2>
    ) => Effect.flatMap(effect, l => l.modify(f)),
})


export const map = <A, ER, EW, RR, RW, B>(
    self: Lens<A, ER, EW, RR, RW>,
    get: (a: NoInfer<A>) => B,
    set: (a: NoInfer<A>, b: B) => NoInfer<A>,
): Lens<B, ER, EW, RR, RW> => make({
    get get() { return Effect.map(self.get, get) },
    get changes() { return Stream.map(self.changes, get) },
    modify: <C, E1 = never, R1 = never>(
        f: (b: B) => Effect.Effect<readonly [C, B], E1, R1>
    ) => self.modify(a =>
        Effect.flatMap(f(get(a)), ([c, next]) => Effect.succeed([c, set(a, next)]))
    ),
})

export const mapEffect = <A, ER, EW, RR, RW, B, EGet = never, RGet = never, ESet = never, RSet = never>(
    self: Lens<A, ER, EW, RR, RW>,
    get: (a: NoInfer<A>) => Effect.Effect<B, EGet, RGet>,
    set: (a: NoInfer<A>, b: B) => Effect.Effect<NoInfer<A>, ESet, RSet>,
): Lens<B, ER | EGet, EW | ESet, RR | RGet, RW | RSet> => make({
    get get() { return Effect.flatMap(self.get, get) },
    get changes() { return Stream.mapEffect(self.changes, get) },
    modify: <C, E1 = never, R1 = never>(
        f: (b: B) => Effect.Effect<readonly [C, B], E1, R1>
    ) => self.modify(a => Effect.flatMap(
        get(a),
        b => Effect.flatMap(
            f(b),
            ([c, bNext]) => Effect.flatMap(
                set(a, bNext),
                nextA => Effect.succeed([c, nextA] as const),
            ),
        )
    )),
})


export const get = <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>): Effect.Effect<A, ER, RR> => self.get

export const set: {
    <A, ER, EW, RR, RW>(value: A): (self: Lens<A, ER, EW, RR, RW>) => Effect.Effect<void, ER | EW, RR | RW>
    <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, value: A): Effect.Effect<void, ER | EW, RR | RW>
} = Function.dual(2, <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, value: A) =>
    self.modify<void, never, never>(() => Effect.succeed([void 0, value] as const)),
)

export const getAndSet: {
    <A, ER, EW, RR, RW>(value: A): (self: Lens<A, ER, EW, RR, RW>) => Effect.Effect<A, ER | EW, RR | RW>
    <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, value: A): Effect.Effect<A, ER | EW, RR | RW>
} = Function.dual(2, <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, value: A) =>
    self.modify<A, never, never>(a => Effect.succeed([a, value] as const)),
)

export const update: {
    <A, ER, EW, RR, RW>(f: (a: A) => A): (self: Lens<A, ER, EW, RR, RW>) => Effect.Effect<void, ER | EW, RR | RW>
    <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => A): Effect.Effect<void, ER | EW, RR | RW>
} = Function.dual(2, <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => A) =>
    self.modify<void, never, never>(a => Effect.succeed([void 0, f(a)] as const)),
)

export const updateEffect: {
    <A, ER, EW, RR, RW, E, R>(f: (a: A) => Effect.Effect<A, E, R>): (self: Lens<A, ER, EW, RR, RW>) => Effect.Effect<void, ER | EW | E, RR | RW | R>
    <A, ER, EW, RR, RW, E, R>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => Effect.Effect<A, E, R>): Effect.Effect<void, ER | EW | E, RR | RW | R>
} = Function.dual(2, <A, ER, EW, RR, RW, E, R>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => Effect.Effect<A, E, R>) =>
    self.modify<void, E, R>(a => Effect.flatMap(
        f(a),
        next => Effect.succeed([void 0, next] as const),
    )),
)

export const getAndUpdate: {
    <A, ER, EW, RR, RW>(f: (a: A) => A): (self: Lens<A, ER, EW, RR, RW>) => Effect.Effect<A, ER | EW, RR | RW>
    <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => A): Effect.Effect<A, ER | EW, RR | RW>
} = Function.dual(2, <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => A) =>
    self.modify<A, never, never>(a => Effect.succeed([a, f(a)] as const)),
)

export const getAndUpdateEffect: {
    <A, ER, EW, RR, RW, E, R>(f: (a: A) => Effect.Effect<A, E, R>): (self: Lens<A, ER, EW, RR, RW>) => Effect.Effect<A, ER | EW | E, RR | RW | R>
    <A, ER, EW, RR, RW, E, R>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => Effect.Effect<A, E, R>): Effect.Effect<A, ER | EW | E, RR | RW | R>
} = Function.dual(2, <A, ER, EW, RR, RW, E, R>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => Effect.Effect<A, E, R>) =>
    self.modify<A, E, R>(a => Effect.flatMap(
        f(a),
        next => Effect.succeed([a, next] as const)
    )),
)

export const setAndGet: {
    <A, ER, EW, RR, RW>(value: A): (self: Lens<A, ER, EW, RR, RW>) => Effect.Effect<A, ER | EW, RR | RW>
    <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, value: A): Effect.Effect<A, ER | EW, RR | RW>
} = Function.dual(2, <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, value: A) =>
    self.modify<A, never, never>(() => Effect.succeed([value, value] as const)),
)

export const updateAndGet: {
    <A, ER, EW, RR, RW>(f: (a: A) => A): (self: Lens<A, ER, EW, RR, RW>) => Effect.Effect<A, ER | EW, RR | RW>
    <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => A): Effect.Effect<A, ER | EW, RR | RW>
} = Function.dual(2, <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => A) =>
    self.modify<A, never, never>(a => {
        const next = f(a)
        return Effect.succeed([next, next] as const)
    }),
)

export const updateAndGetEffect: {
    <A, ER, EW, RR, RW, E, R>(f: (a: A) => Effect.Effect<A, E, R>): (self: Lens<A, ER, EW, RR, RW>) => Effect.Effect<A, ER | EW | E, RR | RW | R>
    <A, ER, EW, RR, RW, E, R>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => Effect.Effect<A, E, R>): Effect.Effect<A, ER | EW | E, RR | RW | R>
} = Function.dual(2, <A, ER, EW, RR, RW, E, R>(self: Lens<A, ER, EW, RR, RW>, f: (a: A) => Effect.Effect<A, E, R>) =>
    self.modify<A, E, R>(a => Effect.flatMap(
        f(a),
        next => Effect.succeed([next, next] as const),
    )),
)


Effect.gen(function*() {
    const myChunkRef = yield* SubscriptionRef.make(Chunk.make(12, 38, 69) as Chunk.Chunk<number>)
    const myChunkLens = fromSubscriptionRef(myChunkRef)
    const chunkValueLens = mapEffect(myChunkLens, Chunk.get(1), (a, b) => Effect.succeed(Chunk.replace(a, 1, b)))

    console.log(yield* myChunkRef.get, yield* chunkValueLens.get)
    // yield* update(myChunkLens, Chunk.replace(1, 22))
    yield* set(chunkValueLens, 22)
    console.log(yield* myChunkRef.get, yield* chunkValueLens.get)
}).pipe(
    Effect.runSync
)