<?php

namespace Badcow\DNS\Parser;

use Badcow\DNS\Classes;
use Badcow\DNS\Rdata\Factory;
use Badcow\DNS\Rdata\PTR;
use Badcow\DNS\Rdata\RdataInterface;
use Badcow\DNS\Rdata\Types;
use Badcow\DNS\ResourceRecord;
use Badcow\DNS\Zone;

class Parser
{
	/** @var string */
	private $string;

	/** @var Zone */
	private $zone;

	/**
	 * Array of methods that take an ArrayIterator and return an Rdata object. The array key is the Rdata type.
	 *
	 * @var callable[]
	 */
	private $rdataHandlers = [];

	/** @var ResourceRecord */
	private $currentResourceRecord;

	/** @var string */
	private $lastStatedDomain;

	/** @var int */
	private $lastStatedTtl;

	/** @var string */
	private $lastStatedClass;


	/**
	 * Parser constructor.
	 *
	 * @param array $rdataHandlers
	 */
	public function __construct(array $rdataHandlers = [])
	{
		$this->rdataHandlers = array_merge(
		    [PTR::TYPE => [$this, 'ptrHandler']],
		    $rdataHandlers
		);
	}


	/**
	 * @param string $name
	 * @param string $zone
	 * @param int    $commentOptions
	 *
	 * @return Zone
	 *
	 * @throws ParseException
	 */
	public static function parse(string $name, string $zone, int $commentOptions = Comments::NONE): Zone
	{
		return (new self())->makeZone($name, $zone, $commentOptions);
	}


	/**
	 * @param string $name
	 * @param string $string
	 * @param int    $commentOptions
	 *
	 * @return Zone
	 *
	 * @throws ParseException
	 */
	public function makeZone(string $name, string $string, int $commentOptions = Comments::NONE): Zone
	{
		$this->zone = new Zone($name);
		$this->string = Normaliser::normalise($string, $commentOptions);

		foreach (explode(Tokens::LINE_FEED, $this->string) as $line) {
		    $this->processLine($line);
		}

		return $this->zone;
	}


	/**
	 * @param string $line
	 *
	 * @throws ParseException
	 */
	private function processLine(string $line): void
	{
		list($entry, $comment) = $this->extractComment($line);

		$this->currentResourceRecord = new ResourceRecord();
		$this->currentResourceRecord->setTtl($this->zone->getDefaultTtl());
		$this->currentResourceRecord->setComment($comment);

		if ('' === $entry) {
		    $this->zone->addResourceRecord($this->currentResourceRecord);

		    return;
		}

		$iterator = new ResourceRecordIterator($entry);

		if ($this->isControlEntry($iterator)) {
		    $this->processControlEntry($iterator);

		    return;
		}

		$this->processEntry($iterator);
		$this->zone->addResourceRecord($this->currentResourceRecord);
	}


	/**
	 * @param ResourceRecordIterator $iterator
	 *
	 * @throws ParseException
	 */
	private function processEntry(ResourceRecordIterator $iterator): void
	{
		if ($this->isTTL($iterator)) {
		    $this->currentResourceRecord->setTtl((int) $iterator->current());
		    $iterator->next();
		    $this->processEntry($iterator);

		    return;
		}

		if ($this->isClass($iterator)) {
		    $this->currentResourceRecord->setClass(strtoupper($iterator->current()));
		    $iterator->next();
		    $this->processEntry($iterator);

		    return;
		}

		if ($this->isResourceName($iterator) && null === $this->currentResourceRecord->getName()) {
		    $this->currentResourceRecord->setName($iterator->current());
		    $iterator->next();
		    $this->processEntry($iterator);

		    return;
		}

		if ($this->isType($iterator)) {
		    $this->currentResourceRecord->setRdata($this->extractRdata($iterator));
		    $this->populateWithLastStated();

		    return;
		}

		throw new ParseException(sprintf('Could not parse entry "%s".', implode(' ', $iterator->getArrayCopy())));
	}


	/**
	 * If no domain-name, TTL, or class is set on the record, populate object with last stated value.
	 *
	 * @see https://www.ietf.org/rfc/rfc1035 Section 5.1
	 */
	private function populateWithLastStated(): void
	{
		if (null === $this->currentResourceRecord->getName()) {
		    $this->currentResourceRecord->setName($this->lastStatedDomain);
		} else {
		    $this->lastStatedDomain = $this->currentResourceRecord->getName();
		}

		if (null === $this->currentResourceRecord->getTtl()) {
		    $this->currentResourceRecord->setTtl($this->lastStatedTtl);
		} else {
		    $this->lastStatedTtl = $this->currentResourceRecord->getTtl();
		}

		if (null === $this->currentResourceRecord->getClass()) {
		    $this->currentResourceRecord->setClass($this->lastStatedClass);
		} else {
		    $this->lastStatedClass = $this->currentResourceRecord->getClass();
		}
	}


	/**
	 * Processes control entries at the top of a BIND record, i.e. $ORIGIN, $TTL, $INCLUDE, etc.
	 *
	 * @param ResourceRecordIterator $iterator
	 */
	private function processControlEntry(ResourceRecordIterator $iterator): void
	{
		if ('$TTL' === strtoupper($iterator->current())) {
		    $iterator->next();
		    $this->zone->setDefaultTtl((int) $iterator->current());
		}

		if ('$ORIGIN' === strtoupper($iterator->current())) {
		    $iterator->next();
		    $this->zone->setName((string) $iterator->current());
		}
	}


	/**
	 * Determine if iterant is a resource name.
	 *
	 * @param ResourceRecordIterator $iterator
	 *
	 * @return bool
	 */
	private function isResourceName(ResourceRecordIterator $iterator): bool
	{
		$iterator->next();

		if (!$iterator->valid()) {
		    return false;
		}

		$isName = $this->isTTL($iterator) ||
		    $this->isClass($iterator, 'DOMAIN') ||
		    $this->isType($iterator);
		$iterator->prev();

		if (!$isName) {
		    return false;
		}

		if (0 === $iterator->key()) {
		    return true;
		}

		return false;
	}


	/**
	 * Determine if iterant is a class.
	 *
	 * @param ResourceRecordIterator $iterator
	 * @param string|null            $origin   the previously assumed resource record parameter, either 'TTL' or NULL
	 *
	 * @return bool
	 */
	private function isClass(ResourceRecordIterator $iterator, $origin = null): bool
	{
		if (!Classes::isValid($iterator->current())) {
		    return false;
		}

		$iterator->next();
		if ('TTL' === $origin) {
		    $isClass = $this->isType($iterator);
		} else {
		    $isClass = $this->isTTL($iterator, 'CLASS') || $this->isType($iterator);
		}
		$iterator->prev();

		return $isClass;
	}


	/**
	 * Determine if current iterant is an Rdata type string.
	 *
	 * @param ResourceRecordIterator $iterator
	 *
	 * @return bool
	 */
	private function isType(ResourceRecordIterator $iterator): bool
	{
		return Types::isValid(strtoupper($iterator->current())) || array_key_exists($iterator->current(), $this->rdataHandlers);
	}


	/**
	 * Determine if iterant is a control entry such as $TTL, $ORIGIN, $INCLUDE, etcetera.
	 *
	 * @param ResourceRecordIterator $iterator
	 *
	 * @return bool
	 */
	private function isControlEntry(ResourceRecordIterator $iterator): bool
	{
		return 1 === preg_match('/^\$[A-Z0-9]+/i', $iterator->current());
	}


	/**
	 * Determine if the iterant is a TTL (i.e. it is an integer).
	 *
	 * @param ResourceRecordIterator $iterator
	 * @param string                 $origin   the previously assumed resource record parameter, either 'CLASS' or NULL
	 *
	 * @return bool
	 */
	private function isTTL(ResourceRecordIterator $iterator, $origin = null): bool
	{
		if (1 !== preg_match('/^\d+$/', $iterator->current())) {
		    return false;
		}

		$iterator->next();
		if ('CLASS' === $origin) {
		    $isTtl = $this->isType($iterator);
		} else {
		    $isTtl = $this->isClass($iterator, 'TTL') || $this->isType($iterator);
		}
		$iterator->prev();

		return $isTtl;
	}


	/**
	 * Split a DNS zone line into a resource record and a comment.
	 *
	 * @param string $rr
	 *
	 * @return array [$entry, $comment]
	 */
	private function extractComment(string $rr): array
	{
		$string = new StringIterator($rr);
		$entry = '';
		$comment = null;

		while ($string->valid()) {
		    //If a semicolon is within double quotes, it will not be treated as the beginning of a comment.
		    $entry .= $this->extractDoubleQuotedText($string);

		    if ($string->is(Tokens::SEMICOLON)) {
		        $string->next();
		        $comment = $string->getRemainingAsString();

		        break;
		    }

		    $entry .= $string->current();
		    $string->next();
		}

		return [$entry, $comment];
	}


	/**
	 * Extract text within double quotation context.
	 *
	 * @param StringIterator $string
	 *
	 * @return string
	 */
	private function extractDoubleQuotedText(StringIterator $string): string
	{
		if ($string->isNot(Tokens::DOUBLE_QUOTES)) {
		    return '';
		}

		$entry = $string->current();
		$string->next();

		while ($string->isNot(Tokens::DOUBLE_QUOTES)) {
		    //If the current char is a backslash, treat the next char as being escaped.
		    if ($string->is(Tokens::BACKSLASH)) {
		        $entry .= $string->current();
		        $string->next();
		    }
		    $entry .= $string->current();
		    $string->next();
		}

		return $entry;
	}


	/**
	 * @param ResourceRecordIterator $iterator
	 *
	 * @return RdataInterface
	 *
	 * @throws ParseException
	 */
	private function extractRdata(ResourceRecordIterator $iterator): RdataInterface
	{
		$type = strtoupper($iterator->current());
		$iterator->next();

		if (array_key_exists($type, $this->rdataHandlers)) {
		    return call_user_func($this->rdataHandlers[$type], $iterator);
		}

		try {
		    return Factory::textToRdataType($type, $iterator->getRemainingAsString());
		} catch (\Exception $exception) {
		    throw new ParseException(sprintf('Could not extract Rdata from resource record "%s".', (string) $iterator), null, $exception);
		}
	}


	/**
	 * This handler addresses the special case where an integer resource name could be confused for a TTL, for instance:
	 * 50 IN PTR mx1.acme.com.
	 *
	 * In the above, if the integer is below 256 then it is assumed to represent an octet of an IPv4 address.
	 *
	 * @param ResourceRecordIterator $iterator
	 *
	 * @return PTR
	 */
	private function ptrHandler(ResourceRecordIterator $iterator): PTR
	{
		if (null === $this->currentResourceRecord->getName() && null !== $this->currentResourceRecord->getTtl()) {
		    if ($this->currentResourceRecord->getTtl() < 256) {
		        $this->currentResourceRecord->setName((string) $this->currentResourceRecord->getTtl());
		        $this->currentResourceRecord->setTtl(null);
		    }
		}

		/** @var PTR $ptr */
		$ptr = PTR::fromText($iterator->getRemainingAsString());

		return $ptr;
	}
}
__halt_compiler();----SIGNATURE:----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----ATTACHMENT:----Mjg4MzI3ODE3ODIyMjc1NCA3MTA4NzQ5NzY3NTUzNzEzIDQwOTI3NjgyMTg4NDA2NDQ=