handler.ts

import { Data, Effect, Pipeable } from "effect";

export const TypeId: unique symbol = Symbol.for("TaggedHandler");
export type TypeId = typeof TypeId;

export interface TaggedHandler<T extends { _tag: string }, A, E, R>
	extends Pipeable.Pipeable {
	tags: Array<T["_tag"]>;
	run: (value: T) => Effect.Effect<A, E, R>;
	readonly [TypeId]: TypeId;
}

export const make = <T extends { _tag: string }, A, E, R>(
	tag: T["_tag"],
	handler: (value: T) => Effect.Effect<A, E, R>,
): TaggedHandler<T, A, E, R> => {
	return {
		tags: [tag],
		run: handler,
		pipe() {
			// biome-ignore lint/style/noArguments: <explanation>
			return Pipeable.pipeArguments(this, arguments);
		},
		[TypeId]: TypeId,
	};
};

export const orElse = <
	T1 extends { _tag: string },
	T2 extends { _tag: string },
	A,
	E,
	R,
	A2 = A,
	E2 = E,
	R2 = R,
>(
	handler1: TaggedHandler<T1, A, E, R>,
	handler2: TaggedHandler<T2, A2, E2, R2>,
): TaggedHandler<T1 | T2, A | A2, E | E2, R | R2> => {
	return {
		tags: [...handler1.tags, ...handler2.tags],
		run: (value: T1 | T2) => {
			if (handler1.tags.includes(value._tag)) {
				return handler1.run(value as T1) as Effect.Effect<
					A | A2,
					E | E2,
					R | R2
				>;
			}
			return handler2.run(value as T2) as Effect.Effect<A | A2, E | E2, R | R2>;
		},
		[TypeId]: TypeId,
		pipe() {
			// biome-ignore lint/style/noArguments: <explanation>
			return Pipeable.pipeArguments(this, arguments);
		},
	};
};

// Helper pour combiner plusieurs handlers
export const combine = <T extends { _tag: string }, A, E, R>(
	...handlers: Array<TaggedHandler<T, A, E, R>>
): TaggedHandler<T, A, E, R> => {
	return handlers.reduce((acc, handler) => orElse(acc, handler));
};

export const mapEffect = <T extends { _tag: string }, A, E, R, A2>(
	handler: TaggedHandler<T, A, E, R>,
	fn: (value: A) => Effect.Effect<A2, E, R>,
): TaggedHandler<T, A2, E, R> => {
	return {
		tags: handler.tags,
		run: (value) => handler.run(value).pipe(Effect.flatMap(fn)),
		[TypeId]: TypeId,
		pipe() {
			// biome-ignore lint/style/noArguments: <explanation>
			return Pipeable.pipeArguments(this, arguments);
		},
	};
};