@sveltejs/kit/src/runtime/client/remote-functions/command.js

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/** @import { RemoteCommand, RemoteQueryOverride } from '@sveltejs/kit' */
/** @import { RemoteFunctionResponse } from 'types' */
/** @import { Query } from './query.svelte.js' */
import { app_dir } from '__sveltekit/paths';
import * as devalue from 'devalue';
import { HttpError } from '@sveltejs/kit/internal';
import { app } from '../client.js';
import { stringify_remote_arg } from '../../shared.js';
import { refresh_queries, release_overrides } from './shared.svelte.js';

/**
 * Client-version of the `command` function from `$app/server`.
 * @param {string} id
 * @returns {RemoteCommand<any, any>}
 */
export function command(id) {
	// Careful: This function MUST be synchronous (can't use the async keyword) because the return type has to be a promise with an updates() method.
	// If we make it async, the return type will be a promise that resolves to a promise with an updates() method, which is not what we want.
	return (arg) => {
		/** @type {Array<Query<any> | RemoteQueryOverride>} */
		let updates = [];

		/** @type {Promise<any> & { updates: (...args: any[]) => any }} */
		const promise = (async () => {
			// Wait a tick to give room for the `updates` method to be called
			await Promise.resolve();

			const response = await fetch(`/${app_dir}/remote/${id}`, {
				method: 'POST',
				body: JSON.stringify({
					payload: stringify_remote_arg(arg, app.hooks.transport),
					refreshes: updates.map((u) => u._key)
				}),
				headers: {
					'Content-Type': 'application/json'
				}
			});

			if (!response.ok) {
				release_overrides(updates);
				// We only end up here in case of a network error or if the server has an internal error
				// (which shouldn't happen because we handle errors on the server and always send a 200 response)
				throw new Error('Failed to execute remote function');
			}

			const result = /** @type {RemoteFunctionResponse} */ (await response.json());
			if (result.type === 'redirect') {
				release_overrides(updates);
				throw new Error(
					'Redirects are not allowed in commands. Return a result instead and use goto on the client'
				);
			} else if (result.type === 'error') {
				release_overrides(updates);
				throw new HttpError(result.status ?? 500, result.error);
			} else {
				refresh_queries(result.refreshes, updates);

				return devalue.parse(result.result, app.decoders);
			}
		})();

		promise.updates = (/** @type {any} */ ...args) => {
			updates = args;
			// @ts-expect-error Don't allow updates to be called multiple times
			delete promise.updates;
			return promise;
		};

		return promise;
	};
}