map-reduce.ts
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map-reduce.ts
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	import {
	App,
	Collection,
	CalculatedField,
	Item,
	SubjectPathEquiv,
	ActionName,
	Context,
	} from "../../../main";

	type ParamGetter<T> = (context: Context, item: Item) => Promise<T> \| T;

	type ParamOrGetter<T> = T \| ParamGetter<T>;

	type MapReduceParams<ReturnType, IntermediateValue = any> = {
	source: {
	subject_path: ParamOrGetter<SubjectPathEquiv>;
	action_name: ParamOrGetter<ActionName>;
	params: ParamOrGetter<any>;
	};
	map: (items: Item[]) => IntermediateValue[];
	reduce: [(intermediate: IntermediateValue[]) => ReturnType, any];
	};

	export default class MapReduce<
	ReturnType,
	IntermediateValue
	> extends CalculatedField<ReturnType> {
	name = "map-reduce";
	params: MapReduceParams<ReturnType, IntermediateValue>;
	constructor(
	app: App,
	collection: Collection,
	params: MapReduceParams<ReturnType, IntermediateValue>
	) {
	super(app, collection);
	this.params = params;
	}
	async calculate(context: Context, item: Item) {
	const action_arguments = [
	context,
	this.params.source.subject_path,
	this.params.source.action_name,
	this.params.source.params,
	].map(function (element) {
	if (element instanceof Function) {
	return element(context, item);
	} else {
	return element;
	}
	});
	const fulfilled_params = Promise.all(action_arguments);

	return (await this.app.runAction.apply(App, fulfilled_params))
	.map(this.params.map)
	.reduce(this.params.reduce[0], this.params.reduce[1]);
	}
	}