frontend/src/shared/api/resource-query.ts

import {
	type QueryClient,
	type QueryFunctionContext,
	type QueryKey,
	useQueryClient,
	type UseQueryOptions,
	type UseQueryResult,
} from "@tanstack/react-query";
import { useEffect } from "react";

import type { components } from "./generated/schema";

import { useAuthenticatedQuery } from "./authenticated-query";
import { getAuthenticatedSessionSnapshot } from "./client";
import { ApiErrorCode, apiErrorCode, isApiErrorCode } from "./problem-details";

const accessEpochs = new WeakMap<QueryClient, Map<string, number>>();

type InvestmentResourceMeta = components["schemas"]["InvestmentResourceMetaDto"];

type Resource = {
	data: unknown;
	meta: InvestmentResourceMeta;
};

function invalidateResourceAccess(
	client: QueryClient,
	group: string,
	error: unknown,
) {
	const errorCode = apiErrorCode(error);
	if (
		[
			ApiErrorCode.Forbidden,
			ApiErrorCode.InvalidTbankToken,
			ApiErrorCode.NotFound,
			ApiErrorCode.TbankNotConnected,
		].every(code => !isApiErrorCode(errorCode, code))
	)
		return;
	const epochs = accessEpochs.get(client) ?? new Map<string, number>();
	accessEpochs.set(client, epochs);
	epochs.set(group, (epochs.get(group) ?? 0) + 1);

	const affected = {
		predicate: (cached: { meta?: Record<string, unknown> }) =>
			cached.meta?.accessGroup === group,
	};

	void client.cancelQueries(affected);
	for (const cached of client.getQueryCache().findAll(affected))
		cached.setState({
			data: undefined,
			dataUpdatedAt: 0,
			error: error as Error,
			fetchStatus: "idle",
			status: "error",
		});
}

function unwrapResourceResult<T extends Resource, E>(
	result: UseQueryResult<T, E>,
) {
	const isMissing = result.isSuccess && result.data.data === null;
	const data: T["data"] | undefined = result.data?.data;
	const meta: T["meta"] | undefined = result.data?.meta;

	const status: UseQueryResult<T, E>["status"] = isMissing
		? "pending"
		: result.status;

	// Project resource fields; refetch still returns the transport envelope.
	return {
		...result,
		data: data ?? undefined,
		isPending: result.isPending || isMissing,
		isSuccess: result.isSuccess && !isMissing,
		meta,
		status,
		transport: {
			error: result.error,
			fetchStatus: result.fetchStatus,
			status: result.status,
		},
	};
}

// Observation changes transport mode, never the generated cache identity.
function useResourceQuery<T extends Resource, E, K extends QueryKey>(
	options: UseQueryOptions<T, E, T, K>,
) {
	const client = useQueryClient();

	const group
		= typeof options.meta?.accessGroup === "string"
			? options.meta.accessGroup
			: undefined;

	let epochs = accessEpochs.get(client);

	if (!epochs) {
		epochs = new Map();
		accessEpochs.set(client, epochs);
	}

	const groupEpochs = epochs;
	const queryFunction = options.queryFn;

	const guarded
		= typeof queryFunction === "function"
			? async (context: QueryFunctionContext<K>) => {
				const epoch = group ? (groupEpochs.get(group) ?? 0) : 0;
				const result = await queryFunction(context);
				if (group && epoch !== (groupEpochs.get(group) ?? 0))
					throw new DOMException("Access changed", "AbortError");

				return result;
			}
			: queryFunction;

	const query = useAuthenticatedQuery({ ...options, queryFn: guarded });
	useEffect(() => {
		if (group) invalidateResourceAccess(client, group, query.error);
	}, [client, group, query.error]);

	const observe = async (expectedStateVersion?: string) => {
		const queryFunction = guarded;
		if (
			typeof queryFunction !== "function"
			|| !query.isEnabled
			|| !getAuthenticatedSessionSnapshot()
		)
			return;
		// Cancellation is synchronous; start the replacement in the same boundary.
		void client.cancelQueries({ exact: true, queryKey: options.queryKey });

		return client.query({
			...options,
			queryFn: async (context: QueryFunctionContext<K>) => {
				const [method, path, input] = context.queryKey;

				const init = input as
					undefined
					| { params?: { query?: Record<string, unknown> } };

				const queryKey = [
					method,
					path,
					{
						...init,
						params: {
							...init?.params,
							query: { ...init?.params?.query, sync: "observe" },
						},
					},
				] as unknown as K;

				const response = await queryFunction({ ...context, queryKey });

				if (
					expectedStateVersion
					&& response.meta.stateVersion !== expectedStateVersion
				) {
					// One more observational read; never turn a stale notification into an import.
					const current = await queryFunction({ ...context, queryKey });
					if (current.meta.stateVersion !== expectedStateVersion)
						throw new DOMException("Resource changed", "AbortError");

					return current;
				}

				return response;
			},
			retry: false,
			// Observation validates raw resource metadata, before any observer projection.
			select: undefined,
			staleTime: 0,
		});
	};

	return {
		...unwrapResourceResult(query),
		observe,
		queryKey: options.queryKey,
	};
}

export {
	invalidateResourceAccess,
	type InvestmentResourceMeta,
	unwrapResourceResult,
	useResourceQuery,
};