import { Context, Effect } from "effect" type EffectMethod = (...args: ReadonlyArray) => Effect.Effect type ServiceUse = { readonly [Key in keyof Shape as Shape[Key] extends EffectMethod ? Key : never]: Shape[Key] extends ( ...args: infer Args ) => infer Return ? Args extends ReadonlyArray ? Return extends Effect.Effect ? (...args: Args) => Effect.Effect : never : never : never } export const serviceUse = (tag: Context.Service) => { const cache = new Map Effect.Effect>() // This is the only dynamic boundary: TypeScript knows the accessor shape, // but Proxy property names are runtime values. const access = new Proxy( {}, { get: (_, key) => { if (typeof key !== "string") return undefined const cached = cache.get(key) if (cached) return cached const accessor = (...args: unknown[]) => tag.use((service) => { // oxlint-disable-next-line typescript-eslint/no-unsafe-type-assertion -- Proxy keys are checked at runtime. const method = service[key as keyof Shape] if (typeof method !== "function") return Effect.die(new Error(`Service method not found: ${key}`)) // oxlint-disable-next-line typescript-eslint/no-unsafe-type-assertion -- ServiceUse exposes only Effect-returning methods. return (method as (...args: unknown[]) => Effect.Effect)(...args) }) cache.set(key, accessor) return accessor }, }, ) // oxlint-disable-next-line typescript-eslint/no-unsafe-type-assertion -- Proxy implements the mapped accessor surface lazily. return access as ServiceUse }