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import type {JSONValue, ToJSON} from './json.js';
import type {ScanItem} from './scan-item.js';
import type {ScanOptions} from './scan-options.js';
import type {DatabaseInfo} from './database-info.js';
import type {
REPMInvoke,
Invoke,
OpenTransactionRequest,
} from './repm-invoker.js';
import {ReadTransactionImpl, WriteTransactionImpl} from './transactions.js';
import type {ReadTransaction, WriteTransaction} from './transactions.js';
type Mutator<Return extends JSONValue | void, Args extends JSONValue> = (
args: Args,
) => Promise<Return | void>;
type MutatorImpl<Return extends JSONValue | void, Args extends JSONValue> = (
tx: WriteTransaction,
args: Args,
) => Promise<Return>;
type BeginSyncResult = {
syncID: string;
syncHead: string;
};
export const httpStatusUnauthorized = 401;
type MaybePromise<T> = T | Promise<T>;
export default class Replicache implements ReadTransaction {
private readonly _batchURL: string;
private _dataLayerAuth: string;
private readonly _diffServerAuth: string;
private readonly _diffServerURL: string;
private readonly _name: string;
private readonly _repmInvoke: REPMInvoke;
private _closed = false;
private _online = true;
protected _opened: Promise<unknown> | null = null;
private _root: Promise<string | undefined> = Promise.resolve(undefined);
private readonly _mutatorRegistry = new Map<
string,
MutatorImpl<JSONValue, JSONValue>
>();
private _syncPromise: Promise<void> | null = null;
private readonly _subscriptions = new Set<Subscription<unknown>>();
protected _syncInterval: number | null = 60_000;
// NodeJS has a non standard setTimeout function :'(
protected _timerId: ReturnType<typeof setTimeout> | 0 = 0;
onSync: ((syncing: boolean) => void) | null = null;
/**
* This gets called when we get an HTTP unauthorized from the client view or
* the batch endpoint. Set this to a function that will ask your user to
* reauthenticate.
*/
getDataLayerAuth:
| (() => MaybePromise<string | null | undefined>)
| null
| undefined = null;
constructor({
batchURL = '',
dataLayerAuth = '',
diffServerAuth = '',
diffServerURL,
name = '',
repmInvoke,
}: {
batchURL?: string;
dataLayerAuth?: string;
diffServerAuth?: string;
diffServerURL: string;
name?: string;
repmInvoke: REPMInvoke;
}) {
this._batchURL = batchURL;
this._dataLayerAuth = dataLayerAuth;
this._diffServerAuth = diffServerAuth;
this._diffServerURL = diffServerURL;
this._name = name;
this._repmInvoke = repmInvoke;
this._open();
}
/**
* Lists information about available local databases.
*/
static async list({
repmInvoke,
}: {
repmInvoke: REPMInvoke;
}): Promise<DatabaseInfo[]> {
const res = await repmInvoke('', 'list');
return res['databases'];
}
private async _open(): Promise<void> {
this._opened = this._repmInvoke(this._name, 'open');
this._root = this._getRoot();
await this._root;
if (this._syncInterval !== null) {
await this.sync();
}
}
/**
* Completely delete a local database. Remote replicas in the group aren't affected.
*/
static async drop(
name: string,
{repmInvoke}: {repmInvoke: REPMInvoke},
): Promise<void> {
await repmInvoke(name, 'drop');
}
get online(): boolean {
return this._online;
}
get closed(): boolean {
return this._closed;
}
/**
* The duration between each `sync`. Set this to `null` to prevent syncing in
* the background.
*/
get syncInterval(): number | null {
return this._syncInterval;
}
set syncInterval(duration: number | null) {
if (this._timerId !== 0) {
clearTimeout(this._timerId);
this._timerId = 0;
}
this._syncInterval = duration;
this._scheduleSync();
}
private _scheduleSync(): void {
if (this._syncInterval !== null) {
this._timerId = setTimeout(() => this.sync(), this._syncInterval);
}
}
async close(): Promise<void> {
this._closed = true;
const p = this._invoke('close');
// Clear timer
// Clear subscriptions
for (const subscription of this._subscriptions) {
subscription.controller.close();
}
this._subscriptions.clear();
await p;
}
private async _getRoot(): Promise<string | undefined> {
if (this._closed) {
return undefined;
}
const res = await this._invoke('getRoot');
return res.root;
}
private async _checkChange(root: string | undefined): Promise<void> {
const currentRoot = await this._root; // instantaneous except maybe first time
if (root !== undefined && root !== currentRoot) {
this._root = Promise.resolve(root);
await this._fireOnChange();
}
}
private _invoke: Invoke = async (
rpc: string,
args?: JSONValue | ToJSON,
): Promise<JSONValue> => {
await this._opened;
return await this._repmInvoke(this._name, rpc, args);
};
/** Get a single value from the database. */
get(key: string): Promise<JSONValue | undefined> {
return this.query(tx => tx.get(key));
}
/** Determines if a single key is present in the database. */
has(key: string): Promise<boolean> {
return this.query(tx => tx.has(key));
}
/** Gets many values from the database. */
scan({prefix = '', start, limit = 50}: ScanOptions = {}): Promise<
Iterable<ScanItem>
> {
return this.query(tx => tx.scan({prefix, start, limit}));
}
private async _sync(): Promise<void> {
try {
const beginSyncResult = await this._beginSync();
if (beginSyncResult.syncHead !== '00000000000000000000000000000000') {
await this._maybeEndSync(beginSyncResult);
}
this._online = true;
} catch (e) {
// We purposely don't rethrow here because a common case is that an
// exception is from beginSync() and we are offline. We don't want such
// cases to look so exceptional in the console output.
//
// TODO: we can rethrow here once replicache-internal is improved to not
// treat offlineness as an error.
console.info('Error: $e');
this._online = false;
}
}
protected async _beginSync(): Promise<BeginSyncResult> {
const beginSyncResult = await this._invoke('beginSync', {
batchPushURL: this._batchURL,
diffServerURL: this._diffServerURL,
dataLayerAuth: this._dataLayerAuth,
diffServerAuth: this._diffServerAuth,
});
const {syncInfo} = beginSyncResult;
let reauth = false;
function checkStatus(
data: {httpStatusCode?: number; errorMessage?: string},
serverName: string,
) {
const {httpStatusCode, errorMessage} = data;
if (errorMessage !== '') {
console.error(
`Got error response from ${serverName} server: ${httpStatusCode}: ${errorMessage}`,
);
}
if (httpStatusCode === httpStatusUnauthorized) {
reauth = true;
}
}
const {batchPushInfo} = syncInfo;
if (batchPushInfo) {
checkStatus(batchPushInfo, 'batch');
const mutationInfos = batchPushInfo.batchPushResponse.mutationInfos;
if (mutationInfos != null) {
for (const mutationInfo of mutationInfos) {
console.error(
`MutationInfo: ID: ${mutationInfo.id}, Error: ${mutationInfo.error}`,
);
}
}
}
checkStatus(syncInfo.clientViewInfo, 'client view');
if (reauth && this.getDataLayerAuth) {
const dataLayerAuth = await this.getDataLayerAuth();
if (dataLayerAuth != null) {
this._dataLayerAuth = dataLayerAuth;
// Try again now instead of waiting for another 5 seconds.
return await this._beginSync();
}
}
const syncHead = beginSyncResult.syncHead;
const {syncID} = syncInfo;
return {syncID, syncHead};
}
protected async _maybeEndSync(
beginSyncResult: BeginSyncResult,
): Promise<void> {
if (this._closed) {
return;
}
let {syncHead} = beginSyncResult;
const {replayMutations} = await this._invoke(
'maybeEndSync',
beginSyncResult,
);
if (!replayMutations || replayMutations.length === 0) {
// All done.
await this._checkChange(syncHead);
return;
}
// Replay.
for (const mutation of replayMutations) {
const {original} = mutation;
syncHead = await this._replay(
syncHead,
original,
mutation.name,
mutation.args,
);
}
const {syncID} = beginSyncResult;
await this._maybeEndSync({syncID, syncHead});
}
private async _replay<A extends JSONValue>(
basis: string,
original: string,
name: string,
args: A,
): Promise<string> {
const mutatorImpl = this._mutatorRegistry.get(name);
if (!mutatorImpl) {
console.error(`Unknown mutator ${name}`);
return basis;
}
const res = await this._mutate(name, mutatorImpl, args, {
invokeArgs: {
rebaseOpts: {basis, original},
},
shouldCheckChange: false,
});
return res.ref;
}
/**
* Synchronizes this cache with the server. New local mutations are sent to
* the server, and the latest server state is applied to the cache. Any local
* mutations not included in the new server state are replayed. See the
* Replicache design document for more information on sync:
* https://github.com/rocicorp/replicache/blob/master/design.md
*/
async sync(): Promise<void> {
if (this._closed) {
return;
}
if (this._syncPromise !== null) {
await this._syncPromise;
return;
}
if (this._timerId !== 0) {
clearTimeout(this._timerId);
this._timerId = 0;
}
this._fireOnSync(true);
try {
this._syncPromise = this._sync();
await this._syncPromise;
} finally {
this._syncPromise = null;
this._fireOnSync(false);
this._scheduleSync();
}
}
private _fireOnSync(syncing: boolean): void {
queueMicrotask(() => this.onSync?.(syncing));
}
private async _fireOnChange(): Promise<void> {
const subscriptions = [...this._subscriptions];
const results = await this.query(async tx => {
const promises = subscriptions.map(async s => {
// Tag the result so we can deal with success vs error below.
try {
return {ok: true, value: await s.callback(tx)};
} catch (ex) {
return {ok: false, error: ex};
}
});
return await Promise.all(promises);
});
for (let i = 0; i < subscriptions.length; i++) {
const result = results[i];
if (result.ok) {
subscriptions[i].controller.enqueue(result.value);
} else {
subscriptions[i].controller.error(result.error);
// After error the stream is no longer usable.
this._subscriptions.delete(subscriptions[i]);
}
}
}
/**
* Subcribe to changes to the underlying data. This returns a stream that can
* be listened to. Every time the underlying data changes the listener is
* invoked. The listener is also invoked once the first time the subscription
* is added. There is currently no guarantee that the result of this
* subscription changes and it might get called with the same value over and
* over.
*/
subscribe<R>(
callback: (tx: ReadTransaction) => Promise<R>,
): ReadableStream<R> {
let controller: ReadableStreamDefaultController<R>;
const stream = new ReadableStream<R>({
start: async (c: ReadableStreamDefaultController<R>): Promise<void> => {
controller = c;
// One initial call.
const res = await this.query(callback);
c.enqueue(res);
this._subscriptions.add(subscription as Subscription<unknown>);
},
cancel: (): void => {
this._subscriptions.delete(subscription as Subscription<unknown>);
},
});
const subscription = {
callback,
// ReadableStream calls start synchronously so controller is defined here.
// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-ignore
controller,
};
return stream;
}
/**
* Query is used for read transactions. It is recommended to use transactions
* to ensure you get a consistent view across multiple calls to `get`, `has`
* and `scan`.
*/
async query<R>(callback: (tx: ReadTransaction) => Promise<R>): Promise<R> {
const res = await this._invoke('openTransaction', {});
const txId = res['transactionId'];
try {
const tx = new ReadTransactionImpl(this._invoke, txId);
return await callback(tx);
} finally {
// No need to await the response.
this._closeTransaction(txId);
}
}
/**
* Registers a *mutator*, which is used to make changes to the data.
*
* ## Replays
*
* Mutators run once when they are initially invoked, but they might also be
* *replayed* multiple times during sync. As such mutators should not modify
* application state directly. Also, it is important that the set of
* registered mutator names only grows over time. If Replicache syncs and
* needed mutator is not registered, it will substitute a no-op mutator, but
* this might be a poor user experience.
*
* ## Server application
*
* During sync, a description of each mutation is sent to the server's [batch
* endpoint](https://github.com/rocicorp/replicache/blob/master/README.md#step-5-upstream-sync)
* where it is applied. Once the mutation has been applied successfully, as
* indicated by the [client
* view](https://github.com/rocicorp/replicache/blob/master/README.md#step-2-downstream-sync)'s
* `lastMutationId` field, the local version of the mutation is removed. See
* the [design
* doc](https://github.com/rocicorp/replicache/blob/master/design.md) for
* additional details on the sync protocol.
*
* ## Transactionality
*
* Mutators are atomic: all their changes are applied together, or none are.
* Throwing an exception aborts the transaction. Otherwise, it is committed.
* As with [query] and [subscribe] all reads will see a consistent view of
* the cache while they run.
*/
register<Return extends JSONValue | void, Args extends JSONValue>(
name: string,
mutatorImpl: MutatorImpl<Return, Args>,
): Mutator<Return, Args> {
this._mutatorRegistry.set(
name,
(mutatorImpl as unknown) as MutatorImpl<JSONValue, JSONValue>,
);
return async (args: Args): Promise<Return> =>
(await this._mutate(name, mutatorImpl, args, {shouldCheckChange: true}))
.result;
}
private async _mutate<R extends JSONValue | void, A extends JSONValue>(
name: string,
mutatorImpl: MutatorImpl<R, A>,
args: A,
{
invokeArgs,
shouldCheckChange,
}: {invokeArgs?: OpenTransactionRequest; shouldCheckChange: boolean},
): Promise<{result: R; ref: string}> {
let actualInvokeArgs: OpenTransactionRequest = {args, name};
if (invokeArgs !== undefined) {
actualInvokeArgs = {...actualInvokeArgs, ...invokeArgs};
}
const {transactionId} = await this._invoke(
'openTransaction',
actualInvokeArgs,
);
let result: R;
try {
const tx = new WriteTransactionImpl(this._invoke, transactionId);
result = await mutatorImpl(tx, args);
} catch (ex) {
// No need to await the response.
this._closeTransaction(transactionId);
throw ex;
}
const commitRes = await this._invoke('commitTransaction', {
transactionId,
});
if (commitRes.retryCommit) {
return await this._mutate(name, mutatorImpl, args, {
invokeArgs,
shouldCheckChange,
});
}
const {ref} = commitRes;
if (shouldCheckChange) {
await this._checkChange(ref);
}
return {result, ref};
}
private async _closeTransaction(txId: number): Promise<void> {
try {
await this._invoke('closeTransaction', {transactionId: txId});
} catch (ex) {
console.error('Failed to close transaction', ex);
}
}
}
export class ReplicacheTest extends Replicache {
static async new({
batchURL,
dataLayerAuth,
diffServerAuth,
diffServerURL,
name = '',
repmInvoke,
}: {
diffServerURL: string;
batchURL?: string;
dataLayerAuth?: string;
diffServerAuth?: string;
name?: string;
repmInvoke: REPMInvoke;
}): Promise<ReplicacheTest> {
const rep = new ReplicacheTest({
batchURL,
dataLayerAuth,
diffServerAuth,
diffServerURL,
name,
repmInvoke,
});
await rep._opened;
// await this._root;
return rep;
}
/** @override */
protected _syncInterval: number | null = null;
beginSync(): Promise<BeginSyncResult> {
return super._beginSync();
}
maybeEndSync(beginSyncResult: BeginSyncResult): Promise<void> {
return super._maybeEndSync(beginSyncResult);
}
}
type Subscription<R> = {
callback: (tx: ReadTransaction) => Promise<R>;
controller: ReadableStreamDefaultController<R>;
};