import * as RTE from "fp-ts/ReaderTaskEither";
import * as A from "fp-ts/Array";
import * as s from "fp-ts/string";
import { pipe, constVoid } from "fp-ts/function";

import { deleteNodesForDocumentIds } from "./lib/deleteNodesForDocumentIds";
import { queryDocumentsByIds } from "./lib/queryDocumentsByIds";
import { reportInfo } from "./lib/reportInfo";
import { sourceNodesForDocumentIds } from "./lib/sourceNodesForDocumentIds";
import { touchAllNodes } from "./lib/touchAllNodes";

import { Dependencies, PrismicWebhookBodyApiUpdate } from "./types";

/**
 * Extract all document IDs from a Prismic `api-update` webhook body. All
 * document IDs, including deleted documents, are returned in the same list.
 */
const extractApiUpdateWebhookBodyDocumentIds = (
	webhookBody: PrismicWebhookBodyApiUpdate,
): RTE.ReaderTaskEither<Dependencies, never, string[]> =>
	pipe(
		RTE.ask<Dependencies>(),
		RTE.bindW("documentIds", () => RTE.right(webhookBody.documents)),
		RTE.bindW("releaseDocumentIds", (scope) =>
			pipe(
				[
					...(webhookBody.releases.update || []),
					...(webhookBody.releases.addition || []),
					...(webhookBody.releases.deletion || []),
				],
				A.filter((payload) => payload.id === scope.pluginOptions.releaseID),
				A.chain((payload) => payload.documents),
				RTE.right,
			),
		),
		RTE.map((scope) => [
			...new Set([...scope.documentIds, ...scope.releaseDocumentIds]),
		]),
	);

/**
 * To be executed in the `sourceNodes` API when a Prismic `api-update` webhook
 * is received.
 *
 * This handler is implemented specifically for Gatsby Preview support.
 *
 * This handler performs delta changes to documents that have been updated or deleted.
 *
 * - UPDATED documents: Nodes are updated in the Gatsby data layer.
 * - DELETED documents: Nodes are deleted from the Gatsby data layer.
 *
 * After the handler is complete, the Gatsby data layer should be identical to
 * one that just performed a fresh bootstrap.
 */
export const onWebhookApiUpdate = (
	webhookBody: PrismicWebhookBodyApiUpdate,
): RTE.ReaderTaskEither<Dependencies, Error, void> =>
	pipe(
		RTE.ask<Dependencies>(),
		RTE.chainFirst(() =>
			reportInfo("Received API update webhook. Processing changes."),
		),
		RTE.bind("documentIds", () =>
			extractApiUpdateWebhookBodyDocumentIds(webhookBody),
		),
		RTE.bind("documentsToUpdate", (scope) =>
			queryDocumentsByIds(scope.documentIds),
		),
		RTE.bind("documentIdsToUpdate", (scope) =>
			pipe(
				scope.documentsToUpdate,
				A.map((document) => document.id),
				(ids) => RTE.right(ids),
			),
		),
		// Documents that have been deleted are included in the `documents` field,
		// but they are not marked as deleted. They appear adjacent to documents
		// that still exist but have only been updated.
		//
		// To check if the document was deleted, we query for all documents in the
		// `documents` field and compare the result to that list. Documents that
		// have been deleted will not be returned from the query.
		RTE.bind("documentIdsToDelete", (scope) =>
			pipe(
				scope.documentIds,
				A.difference(s.Eq)(scope.documentIdsToUpdate),
				(ids) => RTE.right(ids),
			),
		),
		RTE.chainFirstW((scope) =>
			reportInfo(
				`Adding or updating the following Prismic documents: [${scope.documentIdsToUpdate
					.map((id) => `"${id}"`)
					.join(", ")}]`,
			),
		),
		RTE.chainFirstW((scope) =>
			reportInfo(
				`Deleting the following Prismic documents: [${scope.documentIdsToDelete
					.map((id) => `"${id}"`)
					.join(", ")}]`,
			),
		),
		RTE.chainFirstW((scope) =>
			deleteNodesForDocumentIds(scope.documentIdsToDelete),
		),
		RTE.chainFirstW((scope) =>
			sourceNodesForDocumentIds(scope.documentIdsToUpdate),
		),
		RTE.chainFirstW((scope) =>
			touchAllNodes({
				exceptPrismicIds: scope.documentIdsToDelete,
			}),
		),
		RTE.map(constVoid),
	);