<?php

/**
 * Represents a single comment object.
 *
 * @property string  $Name
 * @property string  $Comment
 * @property string  $Email
 * @property string  $URL
 * @property string  $BaseClass
 * @property boolean $Moderated
 * @property boolean $IsSpam      True if the comment is known as spam
 * @property integer $ParentID    ID of the parent page / dataobject
 * @property boolean $AllowHtml   If true, treat $Comment as HTML instead of plain text
 * @property string  $SecretToken Secret admin token required to provide moderation links between sessions
 *
 * @method HasManyList ChildComments() List of child comments
 * @method Member Author() Member object who created this comment
 *
 * @package comments
 */
class Comment extends DataObject {
	/**
	 * @var array
	 */
	private static $db = array(
		'Name' => 'Varchar(200)',
		'Comment' => 'Text',
		'Email' => 'Varchar(200)',
		'URL' => 'Varchar(255)',
		'BaseClass' => 'Varchar(200)',
		'Moderated' => 'Boolean(0)',
		'IsSpam' => 'Boolean(0)',
		'ParentID' => 'Int',
		'AllowHtml' => 'Boolean',
		'SecretToken' => 'Varchar(255)',
	);

	private static $has_one = array(
		'Author' => 'Member',
	);

	private static $default_sort = '"Created" DESC';

	private static $defaults = array(
		'Moderated' => 0,
		'IsSpam' => 0,
	);

	private static $casting = array(
		'Title' => 'Varchar',
		'ParentTitle' => 'Varchar',
		'ParentClassName' => 'Varchar',
		'AuthorName' => 'Varchar',
		'RSSName' => 'Varchar',
		'DeleteLink' => 'Varchar',
		'SpamLink' => 'Varchar',
		'HamLink' => 'Varchar',
		'ApproveLink' => 'Varchar',
		'Permalink' => 'Varchar',
	);

	private static $searchable_fields = array(
		'Name',
		'Email',
		'Comment',
		'Created',
		'BaseClass',
	);

	private static $summary_fields = array(
		'Name' => 'Submitted By',
		'Email' => 'Email',
		'Comment' => 'Comment',
		'Created' => 'Date Posted',
		'ParentTitle' => 'Post',
		'IsSpam' => 'Is Spam',
	);

	public function onBeforeWrite() {
		parent::onBeforeWrite();

		// Sanitize HTML, because its expected to be passed to the template unescaped later
		if($this->AllowHtml) {
			$this->Comment = $this->purifyHtml($this->Comment);
		}
	}

	/**
	 * @return Comment_SecurityToken
	 */
	public function getSecurityToken() {
		return Injector::inst()->createWithArgs('Comment_SecurityToken', array($this));
	}

	/**
	 * Migrates the old {@link PageComment} objects to {@link Comment}
	 */
	public function requireDefaultRecords() {
		parent::requireDefaultRecords();

		if(DB::getConn()->hasTable('PageComment')) {
			$comments = DB::query('SELECT * FROM "PageComment"');

			if($comments) {
				while($pageComment = $comments->nextRecord()) {
					// create a new comment from the older page comment
					$comment = new Comment();
					$comment->update($pageComment);

					// set the variables which have changed
					$comment->BaseClass = 'SiteTree';
					$comment->URL = (isset($pageComment['CommenterURL'])) ? $pageComment['CommenterURL'] : '';
					if((int) $pageComment['NeedsModeration'] == 0) $comment->Moderated = true;

					$comment->write();
				}
			}

			DB::alteration_message('Migrated PageComment to Comment', 'changed');
			DB::getConn()->dontRequireTable('PageComment');
		}
	}

	/**
	 * Return a link to this comment
	 *
	 * @param string $action
	 *
	 * @return string link to this comment.
	 */
	public function Link($action = '') {
		if($parent = $this->getParent()) {
			return $parent->Link($action) . '#' . $this->Permalink();
		}
	}

	/**
	 * Returns the permalink for this {@link Comment}. Inserted into
	 * the ID tag of the comment
	 *
	 * @return string
	 */
	public function Permalink() {
		$prefix = $this->getOption('comment_permalink_prefix');
		return $prefix . $this->ID;
	}

	/**
	 * Translate the form field labels for the CMS administration
	 *
	 * @param boolean $includerelations
	 *
	 * @return array
	 */
	public function fieldLabels($includerelations = true) {
		$labels = parent::fieldLabels($includerelations);

		$labels['Name'] = _t('Comment.NAME', 'Author Name');
		$labels['Comment'] = _t('Comment.COMMENT', 'Comment');
		$labels['Email'] = _t('Comment.EMAIL', 'Email');
		$labels['URL'] = _t('Comment.URL', 'URL');
		$labels['IsSpam'] = _t('Comment.ISSPAM', 'Spam?');
		$labels['Moderated'] = _t('Comment.MODERATED', 'Moderated?');
		$labels['ParentTitle'] = _t('Comment.PARENTTITLE', 'Parent');
		$labels['Created'] = _t('Comment.CREATED', 'Date posted');

		return $labels;
	}

	/**
	 * Get the commenting option
	 *
	 * @param string $key
	 *
	 * @return mixed Result if the setting is available, or null otherwise
	 */
	public function getOption($key) {
		// If possible use the current record
		$record = $this->getParent();
		if(!$record && $this->BaseClass) {
			// Otherwise a singleton of that record
			$record = singleton($this->BaseClass);
		} elseif(!$record) {
			// Otherwise just use the default options
			$record = singleton('CommentsExtension');
		}

		return $record->getCommentsOption($key);
	}

	/**
	 * Returns the parent {@link DataObject} this comment is attached too
	 *
	 * @return DataObject
	 */
	public function getParent() {
		return $this->BaseClass && $this->ParentID
			? DataObject::get_by_id($this->BaseClass, $this->ParentID, true)
			: null;
	}


	/**
	 * Returns a string to help identify the parent of the comment
	 *
	 * @return string
	 */
	public function getParentTitle() {
		if($parent = $this->getParent()) {
			return $parent->Title ?: ($parent->ClassName . ' #' . $parent->ID);
		}
	}

	/**
	 * Comment-parent classnames obviously vary, return the parent classname
	 *
	 * @return string
	 */
	public function getParentClassName() {
		return $this->BaseClass;
	}

	public function castingHelper($field) {
		// Safely escape the comment
		if($field === 'EscapedComment') {
			return $this->AllowHtml ? 'HTMLText' : 'Varchar';
		}
		return parent::castingHelper($field);
	}

	/**
	 * Content to be safely escaped on the frontend
	 *
	 * @return string
	 */
	public function getEscapedComment() {
		return $this->Comment;
	}

	/**
	 * Return whether this comment is a preview (has not been written to the db)
	 *
	 * @return boolean
	 */
	public function isPreview() {
		return !$this->exists();
	}

	/**
	 * @todo needs to compare to the new {@link Commenting} configuration API
	 *
	 * @param Member $member
	 *
	 * @return bool
	 */
	public function canCreate($member = null) {
		return false;
	}

	/**
	 * Checks for association with a page, and {@link SiteTree->ProvidePermission}
	 * flag being set to true.
	 *
	 * @param Member $member
	 *
	 * @return Boolean
	 */
	public function canView($member = null) {
		if(!$member) $member = Member::currentUser();

		// Standard mechanism for accepting permission changes from decorators
		$extended = $this->extendedCan('canView', $member);
		if($extended !== null) return $extended;

		// Allow admin
		if(Permission::checkMember($member, 'CMS_ACCESS_CommentAdmin')) return true;

		// Check if parent has comments and can be viewed
		$parent = $this->getParent();
		return $parent && $parent->ProvideComments && $parent->canView($member);
	}

	/**
	 * Checks for "CMS_ACCESS_CommentAdmin" permission codes and
	 * {@link canView()}.
	 *
	 * @param Member $member
	 *
	 * @return Boolean
	 */
	public function canEdit($member = null) {
		if(!$member) $member = Member::currentUser();

		// Standard mechanism for accepting permission changes from decorators
		$extended = $this->extendedCan('canEdit', $member);
		if($extended !== null) return $extended;

		if(!$this->canView($member)) return false;

		return (bool) Permission::checkMember($member, 'CMS_ACCESS_CommentAdmin');
	}

	/**
	 * Checks for "CMS_ACCESS_CommentAdmin" permission codes and
	 * {@link canEdit()}.
	 *
	 * @param Member $member
	 *
	 * @return Boolean
	 */
	public function canDelete($member = null) {
		if(!$member) $member = Member::currentUser();

		// Standard mechanism for accepting permission changes from decorators
		$extended = $this->extendedCan('canDelete', $member);
		if($extended !== null) return $extended;

		return $this->canEdit($member);
	}

	/**
	 * Return the authors name for the comment
	 *
	 * @return string
	 */
	public function getAuthorName() {
		if($this->Name) {
			return $this->Name;
		} else if($author = $this->Author()) {
			return $author->getName();
		}
	}

	/**
	 * Generate a secure admin-action link authorised for the specified member
	 *
	 * @param string $action An action on CommentingController to link to
	 * @param Member $member The member authorised to invoke this action
	 *
	 * @return string
	 */
	protected function actionLink($action, $member = null) {
		if(!$member) $member = Member::currentUser();
		if(!$member) return false;

		$url = Controller::join_links(
			Director::baseURL(),
			'CommentingController',
			$action,
			$this->ID
		);

		// Limit access for this user
		$token = $this->getSecurityToken();
		return $token->addToUrl($url, $member);
	}

	/**
	 * Link to delete this comment
	 *
	 * @param Member $member
	 *
	 * @return string
	 */
	public function DeleteLink($member = null) {
		if($this->canDelete($member)) {
			return $this->actionLink('delete', $member);
		}
	}

	/**
	 * Link to mark as spam
	 *
	 * @param Member $member
	 *
	 * @return string
	 */
	public function SpamLink($member = null) {
		if($this->canEdit($member) && !$this->IsSpam) {
			return $this->actionLink('spam', $member);
		}
	}

	/**
	 * Link to mark as not-spam (ham)
	 *
	 * @param Member $member
	 *
	 * @return string
	 */
	public function HamLink($member = null) {
		if($this->canEdit($member) && $this->IsSpam) {
			return $this->actionLink('ham', $member);
		}
	}

	/**
	 * Link to approve this comment
	 *
	 * @param Member $member
	 *
	 * @return string
	 */
	public function ApproveLink($member = null) {
		if($this->canEdit($member) && !$this->Moderated) {
			return $this->actionLink('approve', $member);
		}
	}

	/**
	 * @return string
	 */
	public function SpamClass() {
		if($this->IsSpam) {
			return 'spam';
		} else if(!$this->Moderated) {
			return 'unmoderated';
		} else {
			return 'notspam';
		}
	}

	/**
	 * @return string
	 */
	public function getTitle() {
		$title = sprintf(_t('Comment.COMMENTBY', 'Comment by %s', 'Name'), $this->getAuthorName());

		if($parent = $this->getParent()) {
			if($parent->Title) {
				$title .= sprintf(' %s %s', _t('Comment.ON', 'on'), $parent->Title);
			}
		}

		return $title;
	}

	/*
	 * Modify the default fields shown to the user
	 */
	public function getCMSFields() {
		$fields = parent::getCMSFields();

		$hidden = array('ParentID', 'AuthorID', 'BaseClass', 'AllowHtml', 'SecretToken');

		foreach($hidden as $private) {
			$fields->removeByName($private);
		}

		return $fields;
	}

	/**
	 * @param  String $dirtyHtml
	 *
	 * @return String
	 */
	public function purifyHtml($dirtyHtml) {
		$purifier = $this->getHtmlPurifierService();
		return $purifier->purify($dirtyHtml);
	}

	/**
	 * @return HTMLPurifier (or anything with a "purify()" method)
	 */
	public function getHtmlPurifierService() {
		$config = HTMLPurifier_Config::createDefault();
		$config->set('HTML.AllowedElements', $this->getOption('html_allowed_elements'));
		$config->set('AutoFormat.AutoParagraph', true);
		$config->set('AutoFormat.Linkify', true);
		$config->set('URI.DisableExternalResources', true);
		$config->set('Cache.SerializerPath', getTempFolder());
		return new HTMLPurifier($config);
	}

	/**
	 * Calculate the Gravatar link from the email address
	 *
	 * @return string
	 */
	public function Gravatar() {
		$gravatar = '';
		$use_gravatar = $this->getOption('use_gravatar');
		if($use_gravatar) {
			$gravatar = 'http://www.gravatar.com/avatar/' . md5(strtolower(trim($this->Email)));
			$gravatarsize = $this->getOption('gravatar_size');
			$gravatardefault = $this->getOption('gravatar_default');
			$gravatarrating = $this->getOption('gravatar_rating');
			$gravatar .= '?s=' . $gravatarsize . '&d=' . $gravatardefault . '&r=' . $gravatarrating;
		}

		return $gravatar;
	}
}

/**
 * Provides the ability to generate cryptographically secure tokens for comment moderation
 */
class Comment_SecurityToken {

	private $secret = null;

	/**
	 * @param Comment $comment Comment to generate this token for
	 */
	public function __construct($comment) {
		if(!$comment->SecretToken) {
			$comment->SecretToken = $this->generate();
			$comment->write();
		}
		$this->secret = $comment->SecretToken;
	}

	/**
	 * Generate the token for the given salt and current secret
	 *
	 * @param string $salt
	 *
	 * @return string
	 */
	protected function getToken($salt) {
		return function_exists('hash_pbkdf2')
			? hash_pbkdf2('sha256', $this->secret, $salt, 1000, 30)
			: $this->hash_pbkdf2('sha256', $this->secret, $salt, 100, 30);
	}

	/**
	 * Get the member-specific salt.
	 *
	 * The reason for making the salt specific to a user is that it cannot be "passed in" via a
	 * querystring, requiring the same user to be present at both the link generation and the
	 * controller action.
	 *
	 * @param string $salt   Single use salt
	 * @param Member $member Member object
	 *
	 * @return string Generated salt specific to this member
	 */
	protected function memberSalt($salt, $member) {
		// Fallback to salting with ID in case the member has not one set
		return $salt . ($member->Salt ?: $member->ID);
	}

	/**
	 * @param string $url    Comment action URL
	 * @param Member $member Member to restrict access to this action to
	 *
	 * @return string
	 */
	public function addToUrl($url, $member) {
		$salt = $this->generate(15); // New random salt; Will be passed into url
		// Generate salt specific to this member
		$memberSalt = $this->memberSalt($salt, $member);
		$token = $this->getToken($memberSalt);
		return Controller::join_links(
			$url,
			sprintf(
				'?t=%s&s=%s',
				urlencode($token),
				urlencode($salt)
			)
		);
	}

	/**
	 * @param SS_HTTPRequest $request
	 *
	 * @return boolean
	 */
	public function checkRequest($request) {
		$member = Member::currentUser();
		if(!$member) return false;

		$salt = $request->getVar('s');
		$memberSalt = $this->memberSalt($salt, $member);
		$token = $this->getToken($memberSalt);

		// Ensure tokens match
		return $token === $request->getVar('t');
	}


	/**
	 * Generates new random key
	 *
	 * @param integer $length
	 *
	 * @return string
	 */
	protected function generate($length = null) {
		$generator = new RandomGenerator();
		$result = $generator->randomToken('sha256');
		if($length !== null) return substr($result, 0, $length);
		return $result;
	}

	/*-----------------------------------------------------------
	* PBKDF2 Implementation (described in RFC 2898) from php.net
	*-----------------------------------------------------------
	* @param   string  a   hash algorithm
	* @param   string  p   password
	* @param   string  s   salt
	* @param   int     c   iteration count (use 1000 or higher)
	* @param   int     kl  derived key length
	* @param   int     st  start position of result
	*
	* @return  string  derived key
	*/
	private function hash_pbkdf2($a, $p, $s, $c, $kl, $st = 0) {

		$kb = $st + $kl;     // Key blocks to compute
		$dk = '';          // Derived key

		// Create key
		for($block = 1; $block <= $kb; $block++) {

			// Initial hash for this block
			$ib = $h = hash_hmac($a, $s . pack('N', $block), $p, true);

			// Perform block iterations
			for($i = 1; $i < $c; $i++) {
				// XOR each iterate
				$ib ^= ($h = hash_hmac($a, $h, $p, true));
			}

			$dk .= $ib;   // Append iterated block

		}

		// Return derived key of correct length
		return substr($dk, $st, $kl);
	}
}