rxdb/src/plugins/storage-remote/remote.ts

A local-first realtime NoSQL Database for JavaScript applications - https://rxdb.info/

import { filter, Subscription } from 'rxjs';
import type {
    RxStorageInstance,
    RxStorageInstanceCreationParams
} from '../../types/index.d.ts';
import {
    deepEqual,
    ensureNotFalsy,
    RXDB_VERSION
} from '../../plugins/utils/index.ts';
import { createAnswer, createErrorAnswer } from './storage-remote-helpers.ts';
import type {
    MessageFromRemote,
    MessageToRemote,
    RxStorageRemoteExposeSettings,
    RxStorageRemoteExposeSettingsRxDatabase,
    RxStorageRemoteExposeSettingsRxStorage,
    RxStorageRemoteExposeType
} from './storage-remote-types.ts';
import { getChangedDocumentsSince } from '../../rx-storage-helper.ts';
import { newRxError } from '../../rx-error.ts';

/**
 * Run this on the 'remote' part,
 * so that RxStorageMessageChannel can connect to it.
 */
export function exposeRxStorageRemote(settings: RxStorageRemoteExposeSettings): RxStorageRemoteExposeType {
    type InstanceState = {
        storageInstancePromise: Promise<RxStorageInstance<any, any, any>>;
        connectionIds: Set<string>;
        params: RxStorageInstanceCreationParams<any, any>;
    };
    const instanceByFullName: Map<string, InstanceState> = new Map();


    settings.messages$.pipe(
        filter(msg => msg.method === 'custom')
    ).subscribe(async (msg) => {
        if (!settings.customRequestHandler) {
            settings.send(createErrorAnswer(
                msg,
                new Error('Remote storage: cannot resolve custom request because settings.customRequestHandler is not set')
            ));
        } else {
            try {
                const result = await settings.customRequestHandler(msg.params);
                settings.send(createAnswer(msg, result));
            } catch (err: any) {
                settings.send(createErrorAnswer(
                    msg,
                    err
                ));
            }
        }
    });


    function getRxStorageInstance<RxDocType>(params: any): Promise<RxStorageInstance<RxDocType, any, any, any>> {
        if ((settings as RxStorageRemoteExposeSettingsRxStorage).storage) {
            return (settings as RxStorageRemoteExposeSettingsRxStorage).storage.createStorageInstance(params);
        } else if ((settings as RxStorageRemoteExposeSettingsRxDatabase).database) {
            const storageInstances = Array.from((settings as RxStorageRemoteExposeSettingsRxDatabase).database.storageInstances);
            const collectionName = params.collectionName;
            const storageInstance = storageInstances.find(instance => instance.collectionName === collectionName);
            if (!storageInstance) {
                console.dir(storageInstances);
                throw new Error('storageInstance does not exist ' + JSON.stringify({
                    collectionName
                }));
            }
            const schema = params.schema;
            if (!deepEqual(schema, storageInstance.schema)) {
                throw new Error('Wrong schema ' + JSON.stringify({
                    schema,
                    existingSchema: storageInstance.schema
                }));
            }
            return Promise.resolve(storageInstance);
        } else {
            throw new Error('no base given');
        }
    }

    const mustBeRxDBVersion = settings.fakeVersion ? settings.fakeVersion : RXDB_VERSION;
    settings.messages$.pipe(
        filter(msg => msg.method === 'create')
    ).subscribe(async (msg) => {
        if (msg.version !== mustBeRxDBVersion) {
            settings.send(createErrorAnswer(msg, newRxError('RM1', {
                args: {
                    mainVersion: msg.version,
                    remoteVersion: mustBeRxDBVersion
                }
            })));
            return;
        }

        const connectionId = msg.connectionId;

        /**
         * Do an isArray check here
         * for runtime check types to ensure we have
         * instance creation params and not method input params.
        */
        if (Array.isArray(msg.params)) {
            return;
        }
        const params = msg.params;
        const collectionName = params.collectionName;

        /**
         * We de-duplicate the storage instances.
         * This makes sense in many environments like
         * electron where on main process contains the storage
         * for multiple renderer processes. Same goes for SharedWorkers etc.
         */
        const fullName = [
            params.databaseName,
            params.collectionName,
            params.schema.version
        ].join('|');
        let state = instanceByFullName.get(fullName);
        if (!state) {
            try {
                state = {
                    /**
                     * We work with a promise here to ensure
                     * that parallel create-calls will still end up
                     * with exactly one instance and not more.
                     */
                    storageInstancePromise: getRxStorageInstance(params),
                    connectionIds: new Set(),
                    params
                };
                instanceByFullName.set(fullName, state);

                /**
                 * Must await the creation here
                 * so that in case of an error,
                 * it knows about the error message and can send
                 * that back to the main process. 
                 */
                await state.storageInstancePromise;
            } catch (err: any) {
                settings.send(createErrorAnswer(msg, err));
                return;
            }
        } else {
            // if instance already existed, ensure that the schema is equal
            if (!deepEqual(params.schema, state.params.schema)) {
                settings.send(createErrorAnswer(msg, new Error('Remote storage: schema not equal to existing storage')));
                return;
            }
        }
        state.connectionIds.add(msg.connectionId);
        const subs: Subscription[] = [];

        const storageInstance = await state.storageInstancePromise;
        /**
         * Automatically subscribe to the changeStream()
         * because we always need them.
         */
        subs.push(
            storageInstance.changeStream().subscribe(changes => {
                const message: MessageFromRemote = {
                    connectionId,
                    answerTo: 'changestream',
                    method: 'changeStream',
                    return: changes
                };
                settings.send(message);
            })
        );

        let connectionClosed = false;
        function closeThisConnection() {
            if (connectionClosed) {
                return;
            }
            connectionClosed = true;
            subs.forEach(sub => sub.unsubscribe());
            ensureNotFalsy(state).connectionIds.delete(connectionId);
            instanceByFullName.delete(fullName);
            /**
             * TODO how to notify the other ports on remove() ?
             */
        }

        // also close the connection when the collection gets closed
        if ((settings as RxStorageRemoteExposeSettingsRxDatabase).database) {
            const database = (settings as RxStorageRemoteExposeSettingsRxDatabase).database;
            const collection = database.collections[collectionName];
            if (collection) {
                collection.onClose.push(() => closeThisConnection());
            } else {
                database.onClose.push(() => closeThisConnection());
            }
        }

        subs.push(
            settings.messages$.pipe(
                filter(subMsg => (subMsg as MessageToRemote).connectionId === connectionId)
            ).subscribe(async (plainMessage) => {
                const message: MessageToRemote = plainMessage as any;
                if (
                    message.method === 'create' ||
                    message.method === 'custom'
                ) {
                    return;
                }
                if (!Array.isArray(message.params)) {
                    return;
                }
                let result;
                try {
                    if (
                        message.method === 'close' &&
                        (settings as RxStorageRemoteExposeSettingsRxDatabase).database
                    ) {
                        /**
                         * Do not close the storageInstance if it was taken from
                         * a running RxDatabase.
                         * In that case we only close the instance
                         * when the RxDatabase gets closed.
                         */
                        settings.send(createAnswer(message, null));
                        return;
                    }
                    /**
                     * On calls to 'close()',
                     * we only close the main instance if there are no other
                     * ports connected.
                     */
                    if (
                        message.method === 'close' &&
                        ensureNotFalsy(state).connectionIds.size > 1
                    ) {
                        settings.send(createAnswer(message, null));
                        ensureNotFalsy(state).connectionIds.delete(connectionId);
                        subs.forEach(sub => sub.unsubscribe());
                        return;
                    }

                    if (message.method === 'getChangedDocumentsSince' && !storageInstance.getChangedDocumentsSince) {
                        result = await getChangedDocumentsSince(
                            storageInstance,
                            message.params[0],
                            message.params[1]
                        );
                    } else {
                        result = await (storageInstance as any)[message.method](
                            message.params[0],
                            message.params[1],
                            message.params[2],
                            message.params[3]
                        );
                    }
                    if (
                        message.method === 'close' ||
                        message.method === 'remove'
                    ) {
                        closeThisConnection();
                    }
                    settings.send(createAnswer(message, result));
                } catch (err: any) {
                    settings.send(createErrorAnswer(message, err));
                }
            })
        );

        settings.send(createAnswer(msg, 'ok'));
    });

    return {
        instanceByFullName
    };
}