Proyectos de Subversion Moodle

<?php

namespace Aws;

use GuzzleHttp\Promise;

/**

 * Iterator that yields each page of results of a pageable operation.

 */

class ResultPaginator implements \Iterator

{

    /** @var AwsClientInterface Client performing operations. */

    private $client;

    /** @var string Name of the operation being paginated. */

    private $operation;

    /** @var array Args for the operation. */

    private $args;

    /** @var array Configuration for the paginator. */

    private $config;

    /** @var Result Most recent result from the client. */

    private $result;

    /** @var string|array Next token to use for pagination. */

    private $nextToken;

    /** @var int Number of operations/requests performed. */

    private $requestCount = 0;

    /**

     * @param AwsClientInterface $client

     * @param string             $operation

     * @param array              $args

     * @param array              $config

     */

    public function __construct(

        AwsClientInterface $client,

        $operation,

        array $args,

        array $config

    ) {

        $this->client = $client;

        $this->operation = $operation;

        $this->args = $args;

        $this->config = $config;

        MetricsBuilder::appendMetricsCaptureMiddleware(

            $this->client->getHandlerList(),

            MetricsBuilder::PAGINATOR

        );

    }

    /**

     * Runs a paginator asynchronously and uses a callback to handle results.

     *

     * The callback should have the signature: function (Aws\Result $result).

     * A non-null return value from the callback will be yielded by the

     * promise. This means that you can return promises from the callback that

     * will need to be resolved before continuing iteration over the remaining

     * items, essentially merging in other promises to the iteration. The last

     * non-null value returned by the callback will be the result that fulfills

     * the promise to any downstream promises.

     *

     * @param callable $handleResult Callback for handling each page of results.

     *                               The callback accepts the result that was

     *                               yielded as a single argument. If the

     *                               callback returns a promise, the promise

     *                               will be merged into the coroutine.

     *

     * @return Promise\Promise

     */

    public function each(callable $handleResult)

    {

        return Promise\Coroutine::of(function () use ($handleResult) {

            $nextToken = null;

            do {

                $command = $this->createNextCommand($this->args, $nextToken);

                $result = (yield $this->client->executeAsync($command));

                $nextToken = $this->determineNextToken($result);

                $retVal = $handleResult($result);

                if ($retVal !== null) {

                    yield Promise\Create::promiseFor($retVal);

                }

            } while ($nextToken);

        });

    }

    /**

     * Returns an iterator that iterates over the values of applying a JMESPath

     * search to each result yielded by the iterator as a flat sequence.

     *

     * @param string $expression JMESPath expression to apply to each result.

     *

     * @return \Iterator

     */

    public function search($expression)

    {

        // Apply JMESPath expression on each result, but as a flat sequence.

        return flatmap($this, function (Result $result) use ($expression) {

            return (array) $result->search($expression);

        });

    }

    /**

     * @return Result

     */

    #[\ReturnTypeWillChange]

    public function current()

    {

        return $this->valid() ? $this->result : false;

    }

    /**

     * @return mixed

     */

    #[\ReturnTypeWillChange]

    public function key()

    {

        return $this->valid() ? $this->requestCount - 1 : null;

    }

    /**

     * @return void

     */

    #[\ReturnTypeWillChange]

    public function next()

    {

        $this->result = null;

    }

    /**

     * @return bool

     */

    #[\ReturnTypeWillChange]

    public function valid()

    {

        if ($this->result) {

            return true;

        }

        if ($this->nextToken || !$this->requestCount) {

            //Forward/backward paging can result in a case where the last page's nextforwardtoken

            //is the same as the one that came before it.  This can cause an infinite loop.

            $hasBidirectionalPaging = $this->config['output_token'] === 'nextForwardToken';

            if ($hasBidirectionalPaging && $this->nextToken) {

                $tokenKey = $this->config['input_token'];

                $previousToken = $this->nextToken[$tokenKey];

            }

            $this->result = $this->client->execute(

                $this->createNextCommand($this->args, $this->nextToken)

            );

            $this->nextToken = $this->determineNextToken($this->result);

            if (isset($previousToken)

                && $previousToken === $this->nextToken[$tokenKey]

            ) {

                return false;

            }

            $this->requestCount++;

            return true;

        }

        return false;

    }

    /**

     * @return void

     */

    #[\ReturnTypeWillChange]

    public function rewind()

    {

        $this->requestCount = 0;

        $this->nextToken = null;

        $this->result = null;

    }

    private function createNextCommand(array $args, ?array $nextToken = null)

    {

        return $this->client->getCommand($this->operation, array_merge($args, ($nextToken ?: [])));

    }

    private function determineNextToken(Result $result)

    {

        if (!$this->config['output_token']) {

            return null;

        }

        if ($this->config['more_results']

            && !$result->search($this->config['more_results'])

        ) {

            return null;

        }

        $nextToken = is_scalar($this->config['output_token'])

            ? [$this->config['input_token'] => $this->config['output_token']]

            : array_combine($this->config['input_token'], $this->config['output_token']);

        return array_filter(array_map(function ($outputToken) use ($result) {

            return $result->search($outputToken);

        }, $nextToken));

    }

}