<?php

namespace Aws;

use Aws\Api\Parser\Exception\ParserException;
use Exception;
use GuzzleHttp\Promise;
use InvalidArgumentException;
use Psr\Http\Message\RequestInterface;
use Psr\Http\Message\ResponseInterface;
use RuntimeException;

/**
 * Converts an HTTP handler into a Command HTTP handler.
 *
 * HTTP handlers have the following signature:
 *     function(RequestInterface $request, array $options) : PromiseInterface
 *
 * The promise returned form an HTTP handler must resolve to a PSR-7 response
 * object when fulfilled or an error array when rejected. The error array
 * can contain the following data:
 *
 * - exception: (required, Exception) Exception that was encountered.
 * - response: (ResponseInterface) PSR-7 response that was received (if a
 *   response) was received.
 * - connection_error: (bool) True if the error is the result of failing to
 *   connect.
 */
class WrappedHttpHandler {
	private $httpHandler;
	private $parser;
	private $errorParser;
	private $exceptionClass;
	private $collectStats;

	/**
	 * @param callable $httpHandler Function that accepts a request and array
	 *                                 of request options and returns a promise
	 *                                 that fulfills with a response or rejects
	 *                                 with an error array.
	 * @param callable $parser Function that accepts a response object
	 *                                 and returns an AWS result object.
	 * @param callable $errorParser Function that parses a response object
	 *                                 into AWS error data.
	 * @param string $exceptionClass Exception class to throw.
	 * @param bool $collectStats Whether to collect HTTP transfer
	 *                                 information.
	 */
	public function __construct(
		callable $httpHandler,
		callable $parser,
		callable $errorParser,
		$exceptionClass = 'Aws\Exception\AwsException',
		$collectStats = false
	) {
		$this->httpHandler    = $httpHandler;
		$this->parser         = $parser;
		$this->errorParser    = $errorParser;
		$this->exceptionClass = $exceptionClass;
		$this->collectStats   = $collectStats;
	}

	/**
	 * Calls the simpler HTTP specific handler and wraps the returned promise
	 * with AWS specific values (e.g., a result object or AWS exception).
	 *
	 * @param CommandInterface $command Command being executed.
	 * @param RequestInterface $request Request to send.
	 *
	 * @return Promise\PromiseInterface
	 */
	public function __invoke(
		CommandInterface $command,
		RequestInterface $request
	) {
		$fn      = $this->httpHandler;
		$options = $command['@http'] ?: [];
		$stats   = [];
		if ( $this->collectStats || ! empty( $options['collect_stats'] ) ) {
			$options['http_stats_receiver'] = static function (
				array $transferStats
			) use ( &$stats ) {
				$stats = $transferStats;
			};
		} elseif ( isset( $options['http_stats_receiver'] ) ) {
			throw new InvalidArgumentException( 'Providing a custom HTTP stats'
			                                     . ' receiver to Aws\WrappedHttpHandler is not supported.' );
		}

		return Promise\promise_for( $fn( $request, $options ) )
			->then(
				function (
					ResponseInterface $res
				) use ( $command, $request, &$stats ) {
					return $this->parseResponse( $command, $request, $res, $stats );
				},
				function ( $err ) use ( $request, $command, &$stats ) {
					if ( is_array( $err ) ) {
						$err = $this->parseError(
							$err,
							$request,
							$command,
							$stats
						);
					}

					return new Promise\RejectedPromise( $err );
				}
			);
	}

	/**
	 * @param CommandInterface $command
	 * @param RequestInterface $request
	 * @param ResponseInterface $response
	 * @param array $stats
	 *
	 * @return ResultInterface
	 */
	private function parseResponse(
		CommandInterface $command,
		RequestInterface $request,
		ResponseInterface $response,
		array $stats
	) {
		$parser = $this->parser;
		$status = $response->getStatusCode();
		$result = $status < 300
			? $parser( $command, $response )
			: new Result();

		$metadata = [
			'statusCode'    => $status,
			'effectiveUri'  => (string) $request->getUri(),
			'headers'       => [],
			'transferStats' => [],
		];
		if ( ! empty( $stats ) ) {
			$metadata['transferStats']['http'] = [ $stats ];
		}

		// Bring headers into the metadata array.
		foreach ( $response->getHeaders() as $name => $values ) {
			$metadata['headers'][ strtolower( $name ) ] = $values[0];
		}

		$result['@metadata'] = $metadata;

		return $result;
	}

	/**
	 * Parses a rejection into an AWS error.
	 *
	 * @param array $err Rejection error array.
	 * @param RequestInterface $request Request that was sent.
	 * @param CommandInterface $command Command being sent.
	 * @param array $stats Transfer statistics
	 *
	 * @return Exception
	 */
	private function parseError(
		array $err,
		RequestInterface $request,
		CommandInterface $command,
		array $stats
	) {
		if ( ! isset( $err['exception'] ) ) {
			throw new RuntimeException( 'The HTTP handler was rejected without an "exception" key value pair.' );
		}

		$serviceError = "AWS HTTP error: " . $err['exception']->getMessage();

		if ( ! isset( $err['response'] ) ) {
			$parts = [ 'response' => null ];
		} else {
			try {
				$parts        = call_user_func(
					$this->errorParser,
					$err['response'],
					$command
				);
				$serviceError .= " {$parts['code']} ({$parts['type']}): "
				                 . "{$parts['message']} - " . $err['response']->getBody();
			} catch ( ParserException $e ) {
				$parts        = [];
				$serviceError .= ' Unable to parse error information from '
				                 . "response - {$e->getMessage()}";
			}

			$parts['response'] = $err['response'];
		}

		$parts['exception']        = $err['exception'];
		$parts['request']          = $request;
		$parts['connection_error'] = ! empty( $err['connection_error'] );
		$parts['transfer_stats']   = $stats;

		return new $this->exceptionClass(
			sprintf(
				'Error executing "%s" on "%s"; %s',
				$command->getName(),
				$request->getUri(),
				$serviceError
			),
			$command,
			$parts,
			$err['exception']
		);
	}
}
