<?php

namespace Aws\Api\Parser;

use Aws\Api\Parser\Exception\ParserException;
use Aws\Api\StructureShape;
use Aws\Exception\EventStreamDataException;
use Iterator;
use Psr\Http\Message\StreamInterface;

/**
 * @internal Implements a decoder for a binary encoded event stream that will
 * decode, validate, and provide individual events from the stream.
 */
class EventParsingIterator implements Iterator {
	/** @var StreamInterface */
	private $decodingIterator;

	/** @var StructureShape */
	private $shape;

	/** @var AbstractParser */
	private $parser;

	public function __construct(
		StreamInterface $stream,
		StructureShape $shape,
		AbstractParser $parser
	) {
		$this->decodingIterator = new DecodingEventStreamIterator( $stream );
		$this->shape            = $shape;
		$this->parser           = $parser;
	}

	public function current() {
		return $this->parseEvent( $this->decodingIterator->current() );
	}

	private function parseEvent( array $event ) {
		if ( ! empty( $event['headers'][':message-type'] ) ) {
			if ( $event['headers'][':message-type'] === 'error' ) {
				return $this->parseError( $event );
			}
			if ( $event['headers'][':message-type'] !== 'event' ) {
				throw new ParserException( 'Failed to parse unknown message type.' );
			}
		}

		if ( empty( $event['headers'][':event-type'] ) ) {
			throw new ParserException( 'Failed to parse without event type.' );
		}
		$eventShape = $this->shape->getMember( $event['headers'][':event-type'] );

		$parsedEvent = [];
		foreach ( $eventShape['members'] as $shape => $details ) {
			if ( ! empty( $details['eventpayload'] ) ) {
				$payloadShape = $eventShape->getMember( $shape );
				if ( $payloadShape['type'] === 'blob' ) {
					$parsedEvent[ $shape ] = $event['payload'];
				} else {
					$parsedEvent[ $shape ] = $this->parser->parseMemberFromStream(
						$event['payload'],
						$payloadShape,
						null
					);
				}
			} else {
				$parsedEvent[ $shape ] = $event['headers'][ $shape ];
			}
		}

		return [
			$event['headers'][':event-type'] => $parsedEvent
		];
	}

	private function parseError( array $event ) {
		throw new EventStreamDataException(
			$event['headers'][':error-code'],
			$event['headers'][':error-message']
		);
	}

	public function key() {
		return $this->decodingIterator->key();
	}

	public function next() {
		$this->decodingIterator->next();
	}

	public function rewind() {
		$this->decodingIterator->rewind();
	}

	public function valid() {
		return $this->decodingIterator->valid();
	}
}