<?php

namespace YaySMTP\Aws3\Aws;

use YaySMTP\Aws3\Aws\Exception\AwsException;
use YaySMTP\Aws3\GuzzleHttp\Promise;
use YaySMTP\Aws3\GuzzleHttp\Promise\PromisorInterface;
use YaySMTP\Aws3\GuzzleHttp\Promise\RejectedPromise;

/**
 * "Waiters" are associated with an AWS resource (e.g., EC2 instance), and poll
 * that resource and until it is in a particular state.
 * The Waiter object produces a promise that is either a.) resolved once the
 * waiting conditions are met, or b.) rejected if the waiting conditions cannot
 * be met or has exceeded the number of allowed attempts at meeting the
 * conditions. You can use waiters in a blocking or non-blocking way, depending
 * on whether you call wait() on the promise.
 * The configuration for the waiter must include information about the operation
 * and the conditions for wait completion.
 */
class Waiter implements \YaySMTP\Aws3\GuzzleHttp\Promise\PromisorInterface {
  /** @var AwsClientInterface Client used to execute each attempt. */
  private $client;
  /** @var string Name of the waiter. */
  private $name;
  /** @var array Params to use with each attempt operation. */
  private $args;
  /** @var array Waiter configuration. */
  private $config;
  /** @var array Default configuration options. */
  private static $defaults = ['initDelay' => 0, 'before' => null];
  /** @var array Required configuration options. */
  private static $required = ['acceptors', 'delay', 'maxAttempts', 'operation'];
  /**
   * The array of configuration options include:
   *
   * - acceptors: (array) Array of acceptor options
   * - delay: (int) Number of seconds to delay between attempts
   * - maxAttempts: (int) Maximum number of attempts before failing
   * - operation: (string) Name of the API operation to use for polling
   * - before: (callable) Invoked before attempts. Accepts command and tries.
   *
   * @param AwsClientInterface $client Client used to execute commands.
   * @param string             $name   Waiter name.
   * @param array              $args   Command arguments.
   * @param array              $config Waiter config that overrides defaults.
   *
   * @throws \InvalidArgumentException if the configuration is incomplete.
   */
  public function __construct(\YaySMTP\Aws3\Aws\AwsClientInterface $client, $name, array $args = [], array $config = []) {
    $this->client = $client;
    $this->name = $name;
    $this->args = $args;
    // Prepare and validate config.
    $this->config = $config + self::$defaults;
    foreach (self::$required as $key) {
      if (!isset($this->config[$key])) {
        throw new \InvalidArgumentException('The provided waiter configuration was incomplete.');
      }
    }
    if ($this->config['before'] && !is_callable($this->config['before'])) {
      throw new \InvalidArgumentException('The provided "before" callback is not callable.');
    }
  }
  public function promise() {
    return \YaySMTP\Aws3\GuzzleHttp\Promise\coroutine(function () {
      $name = $this->config['operation'];
      for ($state = 'retry', $attempt = 1; $state === 'retry'; $attempt++) {
        // Execute the operation.
        $args = $this->getArgsForAttempt($attempt);
        $command = $this->client->getCommand($name, $args);
        try {
          if ($this->config['before']) {
            $this->config['before']($command, $attempt);
          }
          $result = (yield $this->client->executeAsync($command));
        } catch (AwsException $e) {
          $result = $e;
        }
        // Determine the waiter's state and what to do next.
        $state = $this->determineState($result);
        if ($state === 'success') {
          (yield $command);
        } elseif ($state === 'failed') {
          $msg = "The {$this->name} waiter entered a failure state.";
          if ($result instanceof \Exception) {
            $msg .= ' Reason: ' . $result->getMessage();
          }
          (yield new \YaySMTP\Aws3\GuzzleHttp\Promise\RejectedPromise(new \RuntimeException($msg)));
        } elseif ($state === 'retry' && $attempt >= $this->config['maxAttempts']) {
          $state = 'failed';
          (yield new \YaySMTP\Aws3\GuzzleHttp\Promise\RejectedPromise(new \RuntimeException("The {$this->name} waiter failed after attempt #{$attempt}.")));
        }
      }
    });
  }
  /**
   * Gets the operation arguments for the attempt, including the delay.
   *
   * @param $attempt Number of the current attempt.
   *
   * @return mixed integer
   */
  private function getArgsForAttempt($attempt) {
    $args = $this->args;
    // Determine the delay.
    $delay = $attempt === 1 ? $this->config['initDelay'] : $this->config['delay'];
    if (is_callable($delay)) {
      $delay = $delay($attempt);
    }
    // Set the delay. (Note: handlers except delay in milliseconds.)
    if (!isset($args['@http'])) {
      $args['@http'] = [];
    }
    $args['@http']['delay'] = $delay * 1000;
    return $args;
  }
  /**
   * Determines the state of the waiter attempt, based on the result of
   * polling the resource. A waiter can have the state of "success", "failed",
   * or "retry".
   *
   * @param mixed $result
   *
   * @return string Will be "success", "failed", or "retry"
   */
  private function determineState($result) {
    foreach ($this->config['acceptors'] as $acceptor) {
      $matcher = 'matches' . ucfirst($acceptor['matcher']);
      if ($this->{$matcher}($result, $acceptor)) {
        return $acceptor['state'];
      }
    }
    return $result instanceof \Exception ? 'failed' : 'retry';
  }
  /**
   * @param Result $result   Result or exception.
   * @param array  $acceptor Acceptor configuration being checked.
   *
   * @return bool
   */
  private function matchesPath($result, array $acceptor) {
    return !$result instanceof ResultInterface ? false : $acceptor['expected'] == $result->search($acceptor['argument']);
  }
  /**
   * @param Result $result   Result or exception.
   * @param array  $acceptor Acceptor configuration being checked.
   *
   * @return bool
   */
  private function matchesPathAll($result, array $acceptor) {
    if (!$result instanceof ResultInterface) {
      return false;
    }
    $actuals = $result->search($acceptor['argument']) ?: [];
    foreach ($actuals as $actual) {
      if ($actual != $acceptor['expected']) {
        return false;
      }
    }
    return true;
  }
  /**
   * @param Result $result   Result or exception.
   * @param array  $acceptor Acceptor configuration being checked.
   *
   * @return bool
   */
  private function matchesPathAny($result, array $acceptor) {
    if (!$result instanceof ResultInterface) {
      return false;
    }
    $actuals = $result->search($acceptor['argument']) ?: [];
    foreach ($actuals as $actual) {
      if ($actual == $acceptor['expected']) {
        return true;
      }
    }
    return false;
  }
  /**
   * @param Result $result   Result or exception.
   * @param array  $acceptor Acceptor configuration being checked.
   *
   * @return bool
   */
  private function matchesStatus($result, array $acceptor) {
    if ($result instanceof ResultInterface) {
      return $acceptor['expected'] == $result['@metadata']['statusCode'];
    }
    if ($result instanceof AwsException && ($response = $result->getResponse())) {
      return $acceptor['expected'] == $response->getStatusCode();
    }
    return false;
  }
  /**
   * @param Result $result   Result or exception.
   * @param array  $acceptor Acceptor configuration being checked.
   *
   * @return bool
   */
  private function matchesError($result, array $acceptor) {
    if ($result instanceof AwsException) {
      return $result->isConnectionError() || $result->getAwsErrorCode() == $acceptor['expected'];
    }
    return false;
  }
}