import * as gatsby from "gatsby";
import * as RTE from "fp-ts/ReaderTaskEither";
import * as TE from "fp-ts/TaskEither";
import * as T from "fp-ts/Task";
import { constVoid, pipe } from "fp-ts/function";

import { preparePluginOptions } from "./lib/preparePluginOptions";
import { sourceNodesForAllDocuments } from "./lib/sourceNodesForAllDocuments";
import { throwError } from "./lib/throwError";

import { Dependencies, UnpreparedPluginOptions } from "./types";
import { buildDependencies } from "./buildDependencies";
import { onWebhook } from "./on-webhook";

/**
 * To be executed in the `sourceNodes` API.
 */
const sourceNodesProgram: RTE.ReaderTaskEither<Dependencies, Error, void> =
	pipe(
		RTE.ask<Dependencies>(),
		RTE.chainW(
			RTE.fromPredicate(
				(deps) =>
					Boolean(
						deps.webhookBody && JSON.stringify(deps.webhookBody) !== "{}",
					),
				constVoid,
			),
		),
		RTE.fold(
			() => sourceNodesForAllDocuments,
			() => onWebhook,
		),
	);

/**
 * Extension point to tell plugins to source nodes.
 *
 * @see https://www.gatsbyjs.com/docs/reference/config-files/gatsby-node/#sourceNodes
 */
export const sourceNodes: NonNullable<
	gatsby.GatsbyNode["sourceNodes"]
> = async (
	gatsbyContext: gatsby.SourceNodesArgs,
	unpreparedPluginOptions: UnpreparedPluginOptions,
) => {
	const pluginOptions = await preparePluginOptions(unpreparedPluginOptions);
	const dependencies = await buildDependencies(gatsbyContext, pluginOptions);

	return await pipe(
		sourceNodesProgram(dependencies),
		TE.fold(throwError, () => T.of(void 0)),
	)();
};