AppleScript codegen + pretty-print with Effect

main.ts

import * as Arr from "effect/Array";
import * as Data from "effect/Data";
import * as Effect from "effect/Effect";
import * as Fn from "effect/Function";
import * as Match from "effect/Match";
import * as Option from "effect/Option";

export function render<E = never, C = never>(node: Node<E, C>) {
	return resolveNode(node).pipe(Effect.provide(RenderService.Default));
}

function resolveNode<E = never, C = never>(
	node: Node<E, C>,
): Effect.Effect<string, E, C | RenderService> {
	return Match.value(node).pipe(
		Match.when(Match.string, (s) => {
			return RenderService.use((r) => {
				if (r.lineStart) {
					return `${"\t".repeat(r.indenation)}${s}`;
				}

				return s;
			});
		}),
		Match.tag("Indent", (s) => resolveNode(s.node).pipe(RenderService.indent)),
		Match.tag("InlineSequence", (s) =>
			Fn.pipe(
				s.nodes,
				Arr.map((node, i) => {
					if (i === 0) {
						return resolveNode(node);
					}

					return resolveNode(node).pipe(
						RenderService.update(() => ({ lineStart: false })),
					);
				}),
				Effect.all,
				Effect.map((s) => s.join("")),
			),
		),
		Match.tag("Sequence", (s) =>
			Fn.pipe(
				s.nodes,
				Arr.filterMap((node) =>
					Option.fromNullable(node).pipe(
						Option.map(resolveNode),
						Option.map(RenderService.update(() => ({ lineStart: true }))),
					),
				),
				Effect.all,
				Effect.map((s) => s.join("\n")),
			),
		),
		Match.when(Effect.isEffect, (s) => s.pipe(Effect.flatMap(resolveNode))),
		Match.exhaustive,
	);
}

class Indent<E, C> extends Data.TaggedClass("Indent")<{
	readonly node: Node<E, C>;
}> {}
export function indent<E = never, C = never>(node: Node<E, C>) {
	return new Indent({ node });
}

class InlineSequence<E, C> extends Data.TaggedClass("InlineSequence")<{
	readonly nodes: ReadonlyArray<Node<E, C>>;
}> {}
export function inline<E = never, C = never>(
	...nodes: InlineSequence<E, C>["nodes"]
) {
	return new InlineSequence({ nodes });
}

class Sequence<E, C> extends Data.TaggedClass("Sequence")<{
	readonly nodes: ReadonlyArray<Node<E, C> | null | undefined>;
}> {}
export function seq<E = never, C = never>(...nodes: Sequence<E, C>["nodes"]) {
	return new Sequence({ nodes });
}

type Node<E, C> =
	| string
	| Indent<E, C>
	| InlineSequence<E, C>
	| Sequence<E, C>
	| Effect.Effect<Node<E, C>, E, C | RenderService>;

class RenderService extends Effect.Service<RenderService>()("RenderService", {
	sync() {
		return {
			indenation: 0,
			lineStart: true,
		};
	},
}) {
	static update(fn: (service: RenderService) => Partial<RenderService>) {
		return Effect.updateService(RenderService, (r) => {
			const updated = fn(r);
			return RenderService.make({
				lineStart: updated.lineStart ?? r.lineStart,
				indenation: updated.indenation ?? r.indenation,
			});
		});
	}

	static indent = RenderService.update((r) => ({
		indenation: r.indenation + 1,
	}));
}

export function condition<E = never, C = never>(
	predicate: Node<E, C>,
	ifTrue: Node<E, C>,
	ifFalse?: Node<E, C>,
) {
	return seq(
		inline("if ", predicate, " then"),
		indent(ifTrue),
		ifFalse ? seq("else", indent(ifFalse)) : null,
		"end if",
	);
}

export function tell<E = never, C = never>(who: Node<E, C>, what: Node<E, C>) {
	return seq(inline("tell ", who), indent(what), "end tell");
}

export function isRunning(appName: string) {
	return `application "${appName}" is running`;
}

export function exists<E = never, C = never>(what: Node<E, C>) {
	return inline("exists ", what);
}

export function repeatUntil<E = never, C = never>(
	predicate: Node<E, C>,
	body: Node<E, C>,
) {
	return seq(
		inline("repeat until (", predicate, ")"),
		indent(body),
		"end repeat",
	);
}