<?php

namespace SilverStripe\CMS\Model;

use SilverStripe\Core\Injector\Injector;
use SilverStripe\ORM\DataExtension;
use SilverStripe\ORM\DataObject;
use SilverStripe\ORM\FieldType\DBHTMLText;
use SilverStripe\ORM\ManyManyList;
use SilverStripe\ORM\Versioning\Versioned;
use DOMElement;

/**
 * Adds tracking of links in any HTMLText fields which reference SiteTree or File items.
 *
 * Attaching this to any DataObject will add four fields which contain all links to SiteTree and File items
 * referenced in any HTMLText fields, and two booleans to indicate if there are any broken links. Call
 * augmentSyncLinkTracking to update those fields with any changes to those fields.
 *
 * Note that since both SiteTree and File are versioned, LinkTracking and ImageTracking will
 * only be enabled for the Stage record.
 *
 * {@see SiteTreeFileExtension} for the extension applied to {@see File}
 *
 * @property SiteTree $owner
 *
 * @property bool $HasBrokenFile
 * @property bool $HasBrokenLink
 *
 * @method ManyManyList LinkTracking() List of site pages linked on this page.
 * @method ManyManyList ImageTracking() List of Images linked on this page.
 * @method ManyManyList BackLinkTracking List of site pages that link to this page.
 */
class SiteTreeLinkTracking extends DataExtension {

	/**
	 * @var SiteTreeLinkTracking_Parser
	 */
	protected $parser;

	/**
	 * Inject parser for each page
	 *
	 * @var array
	 * @config
	 */
	private static $dependencies = array(
		'Parser' => '%$SiteTreeLinkTracking_Parser'
	);

	/**
	 * Parser for link tracking
	 *
	 * @return SiteTreeLinkTracking_Parser
	 */
	public function getParser() {
		return $this->parser;
	}

	/**
	 * @param SiteTreeLinkTracking_Parser $parser
	 * @return $this
	 */
	public function setParser($parser) {
		$this->parser = $parser;
		return $this;
	}

	private static $db = array(
		"HasBrokenFile" => "Boolean",
		"HasBrokenLink" => "Boolean"
	);

	private static $many_many = array(
		"LinkTracking" => "SilverStripe\\CMS\\Model\\SiteTree",
		"ImageTracking" => "SilverStripe\\Assets\\File"  // {@see SiteTreeFileExtension}
	);

	private static $belongs_many_many = array(
		"BackLinkTracking" => "SilverStripe\\CMS\\Model\\SiteTree.LinkTracking"
	);

	/**
	 * Tracked images are considered owned by this page
	 *
	 * @config
	 * @var array
	 */
	private static $owns = array(
		"ImageTracking"
	);

	private static $many_many_extraFields = array(
		"LinkTracking" => array("FieldName" => "Varchar"),
		"ImageTracking" => array("FieldName" => "Varchar")
	);

	/**
	 * Scrape the content of a field to detect anly links to local SiteTree pages or files
	 *
	 * @param string $fieldName The name of the field on {@link @owner} to scrape
	 */
	public function trackLinksInField($fieldName) {
		$record = $this->owner;

		$linkedPages = array();
		$linkedFiles = array();

		$htmlValue = Injector::inst()->create('HTMLValue', $record->$fieldName);
		$links = $this->parser->process($htmlValue);

		// Highlight broken links in the content.
		foreach ($links as $link) {
			// Skip links without domelements
			if(!isset($link['DOMReference'])) {
				continue;
			}

			/** @var DOMElement $domReference */
			$domReference = $link['DOMReference'];
			$classStr = trim($domReference->getAttribute('class'));
			if (!$classStr) {
				$classes = array();
			} else {
				$classes = explode(' ', $classStr);
			}

			// Add or remove the broken class from the link, depending on the link status.
			if ($link['Broken']) {
				$classes = array_unique(array_merge($classes, array('ss-broken')));
			} else {
				$classes = array_diff($classes, array('ss-broken'));
			}

			if (!empty($classes)) {
				$domReference->setAttribute('class', implode(' ', $classes));
			} else {
				$domReference->removeAttribute('class');
			}
		}
		$record->$fieldName = $htmlValue->getContent();

		// Populate link tracking for internal links & links to asset files.
		foreach ($links as $link) {
			switch ($link['Type']) {
				case 'sitetree':
					if ($link['Broken']) {
						$record->HasBrokenLink = true;
					} else {
						$linkedPages[] = $link['Target'];
					}
					break;

				case 'file':
				case 'image':
					if ($link['Broken']) {
						$record->HasBrokenFile = true;
					} else {
						$linkedFiles[] = $link['Target'];
					}
					break;

				default:
					if ($link['Broken']) {
						$record->HasBrokenLink = true;
					}
					break;
			}
		}

		// Update the "LinkTracking" many_many
		if($record->ID
			&& $record->getSchema()->manyManyComponent(get_class($record), 'LinkTracking')
			&& ($tracker = $record->LinkTracking())
		) {
			$tracker->removeByFilter(array(
				sprintf('"FieldName" = ? AND "%s" = ?', $tracker->getForeignKey())
					=> array($fieldName, $record->ID)
			));

			if($linkedPages) foreach($linkedPages as $item) {
				$tracker->add($item, array('FieldName' => $fieldName));
			}
		}

		// Update the "ImageTracking" many_many
		if($record->ID
			&& $record->getSchema()->manyManyComponent(get_class($record), 'ImageTracking')
			&& ($tracker = $record->ImageTracking())
		) {
			$tracker->removeByFilter(array(
				sprintf('"FieldName" = ? AND "%s" = ?', $tracker->getForeignKey())
					=> array($fieldName, $record->ID)
			));

			if($linkedFiles) foreach($linkedFiles as $item) {
				$tracker->add($item, array('FieldName' => $fieldName));
			}
		}
	}

	/**
	 * Find HTMLText fields on {@link owner} to scrape for links that need tracking
	 *
	 * @todo Support versioned many_many for per-stage page link tracking
	 */
	public function augmentSyncLinkTracking() {
		// Skip live tracking
		if(Versioned::get_stage() == Versioned::LIVE) {
			return;
		}

		// Reset boolean broken flags
		$this->owner->HasBrokenLink = false;
		$this->owner->HasBrokenFile = false;

		// Build a list of HTMLText fields
		$allFields = DataObject::getSchema()->fieldSpecs($this->owner);
		$htmlFields = array();
		foreach($allFields as $field => $fieldSpec) {
			$fieldObj = $this->owner->dbObject($field);
			if($fieldObj instanceof DBHTMLText) {
				$htmlFields[] = $field;
			}
		}

		foreach($htmlFields as $field) {
			$this->trackLinksInField($field);
		}
	}
}