<?php
/**
 * Copyright 2019 Google Inc.
 *
 * 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.
 */

namespace Google\Cloud\Utils\Test;

use Google\Cloud\Utils\ExponentialBackoff;
use PHPUnit\Framework\TestCase;

class ExponentialBackoffTest extends TestCase
{
    private $delayFunction;

    public function setUp(): void
    {
        $this->delayFunction = function () {
            return;
        };
    }

    /**
     * @dataProvider retriesProvider
     */
    public function testThrowsExceptionAfterFullAttempts($retries, $exception)
    {
        // Expected attempts is the number of retries plus the initial attempt.
        $expectedAttempts = $retries ? $retries + 1 : 4;
        $actualAttempts = 0;
        $hasTriggeredException = false;
        $backoff = new ExponentialBackoff($retries);
        $backoff->setDelayFunction($this->delayFunction);

        try {
            $backoff->execute(function () use (&$actualAttempts, $exception) {
                $actualAttempts++;
                throw $exception;
            });
        } catch (\Exception $ex) {
            $hasTriggeredException = true;
        }

        $this->assertTrue($hasTriggeredException);
        $this->assertEquals($expectedAttempts, $actualAttempts);
    }

    public function retriesProvider()
    {
        $rateLimitExceededMessage = '{"error": {"errors": [{"reason": "rateLimitExceeded"}]}}';
        $userRateLimitExceededMessage = '{"error": {"errors": [{"reason": "userRateLimitExceeded"}]}}';

        return [
            [null, new \Exception('', 500)],
            [2, new \Exception('', 502)],
            [3, new \Exception('', 503)],
            [4, new \Exception('', 504)],
            [5, new \Exception($rateLimitExceededMessage)],
            [6, new \Exception($userRateLimitExceededMessage)]
        ];
    }

    public function testThrowsExceptionWhenRetryFunctionReturnsFalse()
    {
        $actualAttempts = 0;
        $hasTriggeredException = false;
        $retryFunction = function (\Exception $ex) {
            return false;
        };
        $backoff = new ExponentialBackoff(null, $retryFunction);
        $backoff->setDelayFunction($this->delayFunction);

        try {
            $backoff->execute(function () use (&$actualAttempts) {
                $actualAttempts++;
                throw new \Exception();
            });
        } catch (\Exception $ex) {
            $hasTriggeredException = true;
        }

        $this->assertTrue($hasTriggeredException);
        $this->assertEquals(1, $actualAttempts);
    }

    public function testSuccessWithNoRetries()
    {
        $actualAttempts = 0;
        $backoff = new ExponentialBackoff();
        $backoff->setDelayFunction($this->delayFunction);

        $backoff->execute(function () use (&$actualAttempts) {
            $actualAttempts++;
            return;
        });

        $this->assertEquals(1, $actualAttempts);
    }

    public function testCombiningBackoffs()
    {
        $retryCount1 = 0;
        $retryCount2 = 0;
        $executionCount = 0;

        $backoff = new ExponentialBackoff(2, function ($exception) use (&$retryCount1) {
            $retryCount1++;
            return $exception instanceof \DomainException;
        });
        $backoff->setDelayFunction($this->delayFunction);
        $backoff2 = new ExponentialBackoff(1, function ($exception) use (&$retryCount2) {
            $retryCount2++;
            return $exception instanceof \OutOfRangeException;
        });

        $backoff->combine($backoff2);
        $backoff->execute(function () use (&$executionCount) {
            $executionCount++;
            if ($executionCount == 1) {
                throw new \DomainException;
            }
            if ($executionCount == 2) {
                throw new \OutOfRangeException;
            }
            return true;
        });

        $this->assertEquals(2, $retryCount1);
        $this->assertEquals(1, $retryCount2);
        $this->assertEquals(3, $executionCount);
    }

    public function testSetsCalculateDelayFunction()
    {
        $backoff = new ExponentialBackoff();
        $hasTriggeredException = false;
        $actualDelayAmount = 0;
        $expectedDelayAmount = 100;
        $backoff->setDelayFunction(function ($delay) use (&$actualDelayAmount) {
            $actualDelayAmount = $delay;
        });
        $backoff->setCalcDelayFunction(function () use ($expectedDelayAmount) {
            return $expectedDelayAmount;
        });

        try {
            $backoff->execute(function () {
                throw new \Exception();
            });
        } catch (\Exception $ex) {
            $hasTriggeredException = true;
        }

        $this->assertTrue($hasTriggeredException);
        $this->assertEquals($expectedDelayAmount, $actualDelayAmount);
    }

    /**
     * @dataProvider delayProvider
     */
    public function testCalculatesDelay($attempt, $expectedDelayLowerBound, $expectedDelayUpperBound)
    {
        $this->assertThat(
            ExponentialBackoff::calculateDelay($attempt),
            $this->logicalAnd(
                $this->greaterThanOrEqual($expectedDelayLowerBound),
                $this->lessThanOrEqual($expectedDelayUpperBound)
            )
        );
    }

    public function delayProvider()
    {
        return [
            [0, 1000000, 2000000],
            [2, 4000000, 5000000],
            [5, 32000000, 33000000],
            [10, 60000000, 60000000]
        ];
    }
}