/**
* @flow
* Firestore Transaction representation wrapper
*/
import { getAppEventName, SharedEventEmitter } from '../../utils/events';
import { getLogger } from '../../utils/log';
import { getNativeModule } from '../../utils/native';
import Transaction from './Transaction';
import type Firestore from './';
let transactionId = 0;
/**
* Uses the push id generator to create a transaction id
* @returns {number}
* @private
*/
const generateTransactionId = (): number => transactionId++;
export type TransactionMeta = {
id: number,
stack: string[],
reject?: Function,
resolve?: Function,
transaction: Transaction,
updateFunction: (transaction: Transaction) => Promise<any>,
};
type TransactionEvent = {
id: number,
type: 'update' | 'error' | 'complete',
error: ?{ code: string, message: string },
};
/**
* @class TransactionHandler
*/
export default class TransactionHandler {
_firestore: Firestore;
_pending: {
[number]: {
meta: TransactionMeta,
transaction: Transaction,
},
};
constructor(firestore: Firestore) {
this._pending = {};
this._firestore = firestore;
SharedEventEmitter.addListener(
getAppEventName(this._firestore, 'firestore_transaction_event'),
this._handleTransactionEvent.bind(this)
);
}
/**
* -------------
* INTERNAL API
* -------------
*/
/**
* Add a new transaction and start it natively.
* @param updateFunction
*/
_add(
updateFunction: (transaction: Transaction) => Promise<any>
): Promise<any> {
const id = generateTransactionId();
// $FlowExpectedError: Transaction has to be populated
const meta: TransactionMeta = {
id,
updateFunction,
stack: new Error().stack
.split('\n')
.slice(4)
.join('\n'),
};
this._pending[id] = {
meta,
transaction: new Transaction(this._firestore, meta),
};
// deferred promise
return new Promise((resolve, reject) => {
getNativeModule(this._firestore).transactionBegin(id);
meta.resolve = r => {
resolve(r);
this._remove(id);
};
meta.reject = e => {
reject(e);
this._remove(id);
};
});
}
/**
* Destroys a local instance of a transaction meta
*
* @param id
* @private
*/
_remove(id) {
// todo confirm pending arg no longer needed
getNativeModule(this._firestore).transactionDispose(id);
// TODO may need delaying to next event loop
delete this._pending[id];
}
/**
* -------------
* EVENTS
* -------------
*/
/**
* Handles incoming native transaction events and distributes to correct
* internal handler by event.type
*
* @param event
* @returns {*}
* @private
*/
_handleTransactionEvent(event: TransactionEvent) {
switch (event.type) {
case 'update':
return this._handleUpdate(event);
case 'error':
return this._handleError(event);
case 'complete':
return this._handleComplete(event);
default:
getLogger(this._firestore).warn(
`Unknown transaction event type: '${event.type}'`,
event
);
return undefined;
}
}
/**
* Handles incoming native transaction update events
*
* @param event
* @private
*/
async _handleUpdate(event: TransactionEvent) {
const { id } = event;
// abort if no longer exists js side
Iif (!this._pending[id]) return this._remove(id);
const { meta, transaction } = this._pending[id];
const { updateFunction, reject } = meta;
// clear any saved state from previous transaction runs
transaction._prepare();
let finalError;
let updateFailed;
let pendingResult;
// run the users custom update functionality
try {
const possiblePromise = updateFunction(transaction);
// validate user has returned a promise in their update function
// TODO must it actually return a promise? Can't find any usages of it without one...
Iif (!possiblePromise || !possiblePromise.then) {
finalError = new Error(
'Update function for `firestore.runTransaction(updateFunction)` must return a Promise.'
);
} else {
pendingResult = await possiblePromise;
}
} catch (exception) {
// exception can still be falsey if user `Promise.reject();` 's with no args
// so we track the exception with a updateFailed boolean to ensure no fall-through
updateFailed = true;
finalError = exception;
}
// reject the final promise and remove from native
// update is failed when either the users updateFunction
// throws an error or rejects a promise
if (updateFailed) {
// $FlowExpectedError: Reject will always be present
return reject(finalError);
}
// capture the resolved result as we'll need this
// to resolve the runTransaction() promise when
// native emits that the transaction is final
transaction._pendingResult = pendingResult;
// send the buffered update/set/delete commands for native to process
return getNativeModule(this._firestore).transactionApplyBuffer(
id,
transaction._commandBuffer
);
}
/**
* Handles incoming native transaction error events
*
* @param event
* @private
*/
_handleError(event: TransactionEvent) {
const { id, error } = event;
const { meta } = this._pending[id];
if (meta && error) {
const { code, message } = error;
// build a JS error and replace its stack
// with the captured one at start of transaction
// so it's actually relevant to the user
const errorWithStack = new Error(message);
// $FlowExpectedError: code is needed for Firebase errors
errorWithStack.code = code;
// $FlowExpectedError: stack should be a stack trace
errorWithStack.stack = meta.stack;
// $FlowExpectedError: Reject will always be present
meta.reject(errorWithStack);
}
}
/**
* Handles incoming native transaction complete events
*
* @param event
* @private
*/
_handleComplete(event: TransactionEvent) {
const { id } = event;
const { meta, transaction } = this._pending[id];
Eif (meta) {
const pendingResult = transaction._pendingResult;
// $FlowExpectedError: Resolve will always be present
meta.resolve(pendingResult);
}
}
}
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