"use strict";
/*!
 * Copyright 2017 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
Object.defineProperty(exports, "__esModule", { value: true });
const logger_1 = require("./logger");
/*
 * @module firestore/backoff
 * @private
 *
 * Contains backoff logic to facilitate RPC error handling. This class derives
 * its implementation from the Firestore Mobile Web Client.
 *
 * @see https://github.com/firebase/firebase-js-sdk/blob/master/packages/firestore/src/remote/backoff.ts
 */
/*!
 * The default initial backoff time in milliseconds after an error.
 * Set to 1s according to https://cloud.google.com/apis/design/errors.
 */
const DEFAULT_BACKOFF_INITIAL_DELAY_MS = 1000;
/*!
 * The default maximum backoff time in milliseconds.
 */
const DEFAULT_BACKOFF_MAX_DELAY_MS = 60 * 1000;
/*!
 * The default factor to increase the backup by after each failed attempt.
 */
const DEFAULT_BACKOFF_FACTOR = 1.5;
/*!
 * The default jitter to distribute the backoff attempts by (0 means no
 * randomization, 1.0 means +/-50% randomization).
 */
const DEFAULT_JITTER_FACTOR = 1.0;
/*!
 * The maximum number of retries that will be attempted by backoff
 * before stopping all retry attempts.
 */
exports.MAX_RETRY_ATTEMPTS = 10;
/*!
 * The timeout handler used by `ExponentialBackoff`.
 */
let delayExecution = setTimeout;
/**
 * Allows overriding of the timeout handler used by the exponential backoff
 * implementation. If not invoked, we default to `setTimeout()`.
 *
 * Used only in testing.
 *
 * @private
 * @param {function} handler A handler than matches the API of `setTimeout()`.
 */
function setTimeoutHandler(handler) {
    delayExecution = handler;
}
exports.setTimeoutHandler = setTimeoutHandler;
/**
 * A helper for running delayed tasks following an exponential backoff curve
 * between attempts.
 *
 * Each delay is made up of a "base" delay which follows the exponential
 * backoff curve, and a "jitter" (+/- 50% by default)  that is calculated and
 * added to the base delay. This prevents clients from accidentally
 * synchronizing their delays causing spikes of load to the backend.
 *
 * @private
 */
class ExponentialBackoff {
    constructor(options = {}) {
        /**
         * The number of retries that has been attempted.
         *
         * @private
         */
        this._retryCount = 0;
        /**
         * The backoff delay of the current attempt.
         *
         * @private
         */
        this.currentBaseMs = 0;
        /**
         * Whether we are currently waiting for backoff to complete.
         *
         * @private
         */
        this.awaitingBackoffCompletion = false;
        this.initialDelayMs =
            options.initialDelayMs !== undefined
                ? options.initialDelayMs
                : DEFAULT_BACKOFF_INITIAL_DELAY_MS;
        this.backoffFactor =
            options.backoffFactor !== undefined
                ? options.backoffFactor
                : DEFAULT_BACKOFF_FACTOR;
        this.maxDelayMs =
            options.maxDelayMs !== undefined
                ? options.maxDelayMs
                : DEFAULT_BACKOFF_MAX_DELAY_MS;
        this.jitterFactor =
            options.jitterFactor !== undefined
                ? options.jitterFactor
                : DEFAULT_JITTER_FACTOR;
    }
    /**
     * Resets the backoff delay and retry count.
     *
     * The very next backoffAndWait() will have no delay. If it is called again
     * (i.e. due to an error), initialDelayMs (plus jitter) will be used, and
     * subsequent ones will increase according to the backoffFactor.
     *
     * @private
     */
    reset() {
        this._retryCount = 0;
        this.currentBaseMs = 0;
    }
    /**
     * Resets the backoff delay to the maximum delay (e.g. for use after a
     * RESOURCE_EXHAUSTED error).
     *
     * @private
     */
    resetToMax() {
        this.currentBaseMs = this.maxDelayMs;
    }
    /**
     * Returns a promise that resolves after currentDelayMs, and increases the
     * delay for any subsequent attempts.
     *
     * @return A Promise that resolves when the current delay elapsed.
     * @private
     */
    backoffAndWait() {
        if (this.awaitingBackoffCompletion) {
            return Promise.reject(new Error('A backoff operation is already in progress.'));
        }
        if (this.retryCount > exports.MAX_RETRY_ATTEMPTS) {
            return Promise.reject(new Error('Exceeded maximum number of retries allowed.'));
        }
        // First schedule using the current base (which may be 0 and should be
        // honored as such).
        const delayWithJitterMs = this.currentBaseMs + this.jitterDelayMs();
        if (this.currentBaseMs > 0) {
            logger_1.logger('ExponentialBackoff.backoffAndWait', null, `Backing off for ${delayWithJitterMs} ms ` +
                `(base delay: ${this.currentBaseMs} ms)`);
        }
        // Apply backoff factor to determine next delay and ensure it is within
        // bounds.
        this.currentBaseMs *= this.backoffFactor;
        this.currentBaseMs = Math.max(this.currentBaseMs, this.initialDelayMs);
        this.currentBaseMs = Math.min(this.currentBaseMs, this.maxDelayMs);
        this._retryCount += 1;
        return new Promise(resolve => {
            this.awaitingBackoffCompletion = true;
            delayExecution(() => {
                this.awaitingBackoffCompletion = false;
                resolve();
            }, delayWithJitterMs);
        });
    }
    // Visible for testing.
    get retryCount() {
        return this._retryCount;
    }
    /**
     * Returns a randomized "jitter" delay based on the current base and jitter
     * factor.
     *
     * @returns {number} The jitter to apply based on the current delay.
     * @private
     */
    jitterDelayMs() {
        return (Math.random() - 0.5) * this.jitterFactor * this.currentBaseMs;
    }
}
exports.ExponentialBackoff = ExponentialBackoff;
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