<?php namespace ProcessWire;

/**
 * ProcessWire Page Path History
 *
 * Keeps track of past URLs where pages have lived and automatically 301 redirects
 * to the new location whenever the past URL is accessed. 
 *
 * ProcessWire 3.x, Copyright 2022 by Ryan Cramer
 * https://processwire.com
 * 
 * @method upgrade($fromVersion, $toVersion)
 * @property int $minimumAge
 * @property array|bool $rootSegments
 * 
 *
 */

class PagePathHistory extends WireData implements Module, ConfigurableModule {

	public static function getModuleInfo() {
		return array(
			'title' => 'Page Path History', 
			'version' => 8, 
			'summary' => "Keeps track of past URLs where pages have lived and automatically redirects (301 permanent) to the new location whenever the past URL is accessed.",
			'singular' => true, 
			'autoload' => true, 
		);
	}

	/**
	 * Table created by this module
	 *
	 */
	const dbTableName = 'page_path_history';

	/**
	 * Minimum age in seconds that a page must be before we'll bother remembering its previous path
	 *
	 */
	const minimumAge = 120; 

	/**
	 * Maximum segments to support in a redirect URL
	 *
	 * Used to place a limit on recursion and paths
	 *
	 */
	const maxSegments = 10;

	/**
	 * PagePageHistory module/schema version
	 * 
	 * @var int
	 * 
	 */
	protected $version = 0;

	/**
	 * Construct
	 * 
	 */
	public function __construct() {
		parent::__construct();
		$this->set('minimumAge', self::minimumAge); 
		$this->set('rootSegments', false);
	}

	/**
	 * Initialize the hooks
	 *
	 */
	public function init() {
		$this->pages->addHook('moved', $this, 'hookPageMoved'); 
		$this->pages->addHook('renamed', $this, 'hookPageMoved'); 
		$this->pages->addHook('deleted', $this, 'hookPageDeleted');
		$this->addHook('ProcessPageView::pageNotFound', $this, 'hookPageNotFound'); 
		$this->addHook('Page::addUrl', $this, 'hookPageAddUrl');
		$this->addHook('Page::removeUrl', $this, 'hookPageRemoveUrl');
	}

	/**
	 * Get version of this module/schema
	 * 
	 * @return int
	 * 
	 */
	protected function getVersion() {
		if($this->version) return $this->version;
		$this->version = $this->wire()->modules->getModuleInfoProperty($this, 'version');
		if(!$this->version) $this->version = 1;
		return $this->version;
	}

	/**
	 * Whether or not to consider language_id in page_path_history module table
	 * 
	 * @return Languages|bool Returns Languages object if yes, or boolean false if not
	 * 
	 */
	protected function getLanguages() {
		if($this->getVersion() < 2) return false;
		$languages = $this->wire()->languages;
		return $languages && $languages->hasPageNames() ? $languages : false;
	}

	/**
	 * Given a language ID, name or Language object, return Language object or NULL if not found
	 * 
	 * @param int|string|Language $language
	 * @return Language|null
	 * 
	 */
	protected function getLanguage($language) {
		$languages = $this->getLanguages();
		if(!$languages) return null;
		if($language instanceof Page) {
			// ok
		} else if($language === 0) {
			$language = $languages->getDefault();
		} else if(is_int($language) || ctype_digit("$language")) {
			$language = $languages->get((int) $language);
		} else if(is_string($language) && $language) {
			$language = $languages->get($this->wire()->sanitizer->pageNameUTF8($language));
		}
		if($language && !$language->id) $language = null;
		return $language;
	}

	/**
	 * Set a history path for a page and delete any existing entries for page’s current path
	 * 
	 * @param Page $page
	 * @param string $path
	 * @param Language|int $language
	 * @return bool True on success, or false if path already consumed in history
	 *
	 */
	public function setPathHistory(Page $page, $path, $language = null) {
		
		$database = $this->wire()->database;
		$table = self::dbTableName;
		$result = $this->addPathHistory($page, $path, $language);
		
		if($result) {
			// delete any possible entries that overlap with the $page current path since are no longer applicable
			$query = $database->prepare("DELETE FROM $table WHERE path=:path LIMIT 1");
			$query->bindValue(":path", rtrim($this->wire()->sanitizer->pagePathName($page->path, Sanitizer::toAscii), '/'));
			$query->execute();
		}
		
		return $result;
	}

	/**
	 * Add a history path for a page
	 * 
	 * @param Page $page
	 * @param string $path
	 * @param null|Language $language
	 * @return bool True if path was added, or false if it likely overlaps with an existing path
	 * 
	 */
	public function addPathHistory(Page $page, $path, $language = null) {
	
		$sanitizer = $this->wire()->sanitizer;
		$database = $this->wire()->database;
		$modules = $this->wire()->modules;
		$table = self::dbTableName;
		$path = $sanitizer->pagePathName('/' . trim($path, '/'), Sanitizer::toAscii);
		
		$selector = "path=$path";
		if($modules->isInstalled('PagePaths')) $selector .= ", id!=$page->id";
		if($this->wire()->pages->count($selector)) return false; 
		
		$language = $this->getLanguage($language);

		$sql = "INSERT INTO $table SET path=:path, pages_id=:pages_id, created=NOW()";
		if($language) $sql .= ', language_id=:language_id';

		$query = $database->prepare($sql);
		$query->bindValue(":path", $path);
		$query->bindValue(":pages_id", $page->id, \PDO::PARAM_INT);
		if($language) $query->bindValue(':language_id', $language->id, \PDO::PARAM_INT);

		try {
			$result = $query->execute();
		} catch(\Exception $e) {
			// ignore the exception because it means there is already a past URL (duplicate)
			$result = false;
		}
		
		$this->addRootSegment($path);
	
		return $result;
	}
	
	/**
	 * Delete path entry for given page and path
	 * 
	 * @param Page $page
	 * @param string $path
	 * @return int
	 * 
	 */
	public function deletePathHistory(Page $page, $path) {
		
		$database = $this->wire()->database;
		$table = self::dbTableName;
		$path = $this->wire()->sanitizer->pagePathName('/' . trim($path, '/'), Sanitizer::toAscii);
		
		$sql = "DELETE FROM $table WHERE path=:path AND pages_id=:pages_id LIMIT 1";
		$query = $database->prepare($sql);
		$query->bindValue(':path', $path);
		$query->bindValue(':pages_id', $page->id, \PDO::PARAM_INT);
		$query->execute();
		
		$cnt = $query->rowCount();
		$query->closeCursor();
		
		return $cnt;
	}
	
	/**
	 * Delete all path history for a given Page or for all pages
	 * 
	 * @param Page|true $page If value of this param is boolean true (rather than Page), all paths for all pages are cleared
	 * @throws WireException if param $page is not of expected type (true or Page)
	 * @since 3.0.178
	 *
	 */
	public function deleteAllPathHistory($page) {
		$database = $this->wire()->database;
		if($page === true) {
			$database->exec('DELETE FROM ' . self::dbTableName);
		} else if($page instanceof Page && $page->id) {
			$query = $database->prepare('DELETE FROM ' . self::dbTableName . ' WHERE pages_id=:pages_id');
			$query->bindValue(':pages_id', $page->id, \PDO::PARAM_INT);
			$query->execute();
		} else {
			throw new WireException("Invalid param: instance of Page or boolean true expected");
		}
		$this->rebuildRootSegments();
	}
	
	/**
	 * Get an array of all paths the given page has previously had, oldest to newest
	 *
	 * For the options argument: 
	 * - Optionally specify a Language instance (or name or ID) to isolate results to a specific language.
	 * - Optionally specify boolean true to return verbose info. 
	 * 
	 * @param Page $page Page to retrieve paths for. 
	 * @param Language|null|array|bool Specify an option below: 
	 *  - `language` (Language|int|string): Limit returned paths to this language. If none specified, then all languages are included.
	 *  - `verbose` (bool): Return associative array for each path with additional info (date and language, if present).
	 *  - `virtual` (bool): Return history that includes auto-determined virtual entries from parent history? (default=true)
	 *     What this does is also include changes to parent pages that would affect overall URL to requested page. 
	 *  - Or you may specify the `language` option for the options argument. 
	 *  - Or you may specify boolean `true` for options argument as a shortcut for the `verbose` option. 
	 * @return array of paths
	 * 
	 */
	public function getPathHistory(Page $page, $options = array()) {
		
		static $level = 0;
		$level++;
		
		$defaults = array(
			'language' => !is_array($options) && !is_bool($options) ? $options : null, 
			'verbose' => is_bool($options) ? $options : false, 
			'virtual' => true, 
		);
		
		$database = $this->wire()->database;
		$sanitizer = $this->wire()->sanitizer;
		$languages = $this->wire()->languages;
		
		$paths = array();
		$options = is_array($options) ? array_merge($defaults, $options) : $defaults;
		
		if($this->getVersion() < 2) {
			$options['language'] = null;
			$allowLanguage = false;
		} else {
			$allowLanguage = $languages && $languages->hasPageNames();
		}
		
		$language = $options['language'] && $allowLanguage ? $this->getLanguage($options['language']) : null;
		$finds = array('pages_id' => $page->id);
		$selects = array('path');
		$wheres = array();
		
		if($options['verbose']) $selects[] = 'created';
		if($options['verbose'] && $allowLanguage) $selects[] = 'language_id';
		if($language) $finds['language_id'] = $language->isDefault() ? 0 : $language->id;
		
		foreach($finds as $col => $value) {
			$wheres[] = "$col=:$col";
		}
	
		$query = $database->prepare(
			'SELECT ' . implode(', ', $selects) . ' FROM ' . self::dbTableName . ' ' . 
			'WHERE ' . implode(' AND ', $wheres) . ' ' . 
			"ORDER BY created"
		);
		
		foreach($finds as $col => $value) {
			$query->bindValue(":$col", $value, \PDO::PARAM_INT); 
		}
		
		try {
			$query->execute();
			
			/** @noinspection PhpAssignmentInConditionInspection */
			while($row = $query->fetch(\PDO::FETCH_ASSOC)) {
				
				$path = $sanitizer->pagePathName($row['path'], Sanitizer::toUTF8);
				
				if($options['verbose']) {
					$value = array('path' => $path);
					$pathDate = $row['created'];
					$value['date'] = $pathDate;
					if($allowLanguage && isset($row['language_id'])) {
						$pathLanguage = $this->getLanguage((int) $row['language_id']);
						$value['language'] = $pathLanguage && $pathLanguage->id ? $pathLanguage : null;
					}
				} else {
					$value = $path;
				}
				
				$paths[$path] = $value;
			}
		} catch(\Exception $e) {
			if(!$this->checkTableSchema()) {
				$this->error($e->getMessage(), Notice::superuser | Notice::log);
			}
		}
		
		if($options['virtual']) {
			// get changes to current and previous parents as well
			foreach($paths as $value) {
				$virtualPaths = $this->getVirtualHistory($page, $value, $options);
				foreach($virtualPaths as $virtualPath => $virtualInfo) {
					if(isset($paths[$virtualPath])) continue;
					$paths[$virtualPath] = $virtualInfo;
				}
			}
			if($level === 1 && $options['verbose']) {
				$paths = $this->sortVerbosePathInfo($paths); 
			}
		}	
	
		$level--;
		
		return array_values($paths);
	}

	/**
	 * Sort verbose paths by date
	 * 
	 * @param array $paths Verbose paths
	 * @param bool $newest Sort newest to oldest? Specify false so sort oldest to newest. (default=true)
	 * @return array
	 * 
	 */
	protected function sortVerbosePathInfo(array $paths, $newest = true) {
		
		$sortPaths = array();
		
		foreach($paths as $value) {
			$date = strtotime($value['date']);
			while(isset($sortPaths[$date])) $date++;
			$sortPaths[$date] = $value;
		}
		
		if($newest) {
			krsort($sortPaths);
		} else {
			ksort($sortPaths);
		}
		
		return $sortPaths;
	}

	/**
	 * Get history which includes entries not actually in pages_paths table reflecting changes to parents
	 * 
	 * @param Page $page
	 * @param string|array $path
	 * @param array $options
	 *
	 * @return array
	 * 
	 */
	protected function getVirtualHistory(Page $page, $path, array $options) {
		
		$paths = array();
		$checkParents = array();
		
		if(is_array($path)) {
			// path is verbose info
			$pathInfo = $path;
			$path = $pathInfo['path'];
		} else {
			// path is string
			$pathInfo = array('path');
		}
	
		// separate page name and parent path
		$parts = explode('/', trim($path, '/'));
		$pageName = array_pop($parts);
		$parentPath = implode('/', $parts);
	
		// if page’s current parent is not homepage, include it 
		if($page->parent_id > 1) {
			$checkParents[] = $page->parent;
		}

		// if historical parent path differs from page’s current parent path, include it
		if($parentPath === '' || $parentPath === '/') {
			// historial parent is root/home
		} else if($parentPath === trim($page->parent()->path(), '/')) {
			// historial parent is the same as current parent
		} else if($parentPath === trim($page->path(), '/')) {
			// historial parent is the page itself
		} else {
			// historial parent may be one we want to check
			$parent = $this->wire()->pages->get("/$parentPath");
			if(!$parent->id) $parent = $this->getPage($parentPath);
			// if parent from path is different from current page parent, include in our list of parents to check
			if($parent->id > 1 && $parent->id != $page->parent_id && $parent->id != $page->id) {
				$checkParents[] = $parent;
			}
		}

		// get paths for each parent 
		foreach($checkParents as $parent) {
			$parentPaths = $this->getVirtualHistoryParent($page, $pageName, $pathInfo, $parent, $options);
			foreach($parentPaths as $parentPath => $parentInfo) {
				if(!isset($paths[$parentPath])) {
					$paths[$parentPath] = $parentInfo;
				}
			}
		}
		
		return $paths;
	}

	/**
	 * Get virtual history for page in context of a specific parent (companion to getVirtualHistory method)
	 * 
	 * @param Page $page
	 * @param string $pageName Historical name (or same as page->name)
	 * @param array|string $pagePathInfo Path or pathInfo array
	 * @param Page $parent
	 * @param array $options
	 * @return array
	 * 
	 */
	protected function getVirtualHistoryParent(Page $page, $pageName, array $pagePathInfo, Page $parent, array $options) {
		
		$paths = array();
		
		// get path history for this parent
		$parentPaths = $this->getPathHistory($parent, $options);

		// pageNamesDates is array of name => timestamp
		$pageNamesDates = array(
			$pageName => isset($pagePathInfo['date']) ? strtotime($pagePathInfo['date']) : 0
		);

		// if historical name differs from current name, include current name in pageNamesDates
		if($page->name != $pageName) {
			$pageNamesDates[$page->name] = $page->modified;
		}

		// iterate through each of the names this page has had, along with the date that it was changed to it
		foreach($pageNamesDates as $name => $date) {

			// iterate through all possible parent paths
			foreach($parentPaths as $parentPathInfo) {

				$parentPath = $options['verbose'] ? $parentPathInfo['path'] : $parentPathInfo;

				// create path that is historical parent path plus current iteration of page name
				$path = $parentPath . '/' . $name;

				// if we've already got this path, skip it
				if(isset($paths[$path])) continue;

				// non-verbose mode only includes paths
				if(empty($options['verbose'])) {
					$paths[$path] = $path;
					continue;
				}
				
				// if parent change date is older than page change date, then we can skip it
				if(strtotime($parentPathInfo['date']) < $date) continue;
			
				// if path is related to trash do not include it
				if(strpos($path, '/trash/') === 0 || preg_match('!/\d+\.\d+\.\d+_[-_a-z0-9]+!', $path)) {
					continue;
				}
				
				// create verbose info for this entry
				$pathInfo = array(
					'path' => $path,
					'date' => $parentPathInfo['date'],
					'virtual' => $parent->id
				);
				
				// if parent is specific to a language, include that info in the verbose value
				if(isset($parentPathInfo['language'])) {
					$pathInfo['language'] = $parentPathInfo['language'];
				}
				
				$paths[$path] = $pathInfo;
			}
		}
		
		return $paths;
	}

	/**
	 * Get array of info about a path if it is in history
	 * 
	 * If path is found in history, the returned array `id` value will be populated with a positive 
	 * integer of the found page ID. If not found, it will be populated with integer 0. 
	 * 
	 * By default this method attempts to perform exact path matches only. To enable partial matches
	 * of paths that may be appended with additional URL segments, set the `allowUrlSegments` option
	 * to true. Note that it will only apply to matched pages that have templates allowing URL 
	 * segments. 
	 * 
	 * Return array includes:
	 * 
	 * - `id` (int): ID of matched page or 0 if no match.
	 * - `path` (string): Path that was matched.
	 * - `language_id` (int): ID of language for path, if applicable.
	 * - `templates_id` (int): ID of template for page that was matched.
	 * - `parent_id (int): ID of parent for page that was matched.
	 * - `status` (int): Status of the page that was matched.
	 * - `created` (string): Date that this entry was created (ISO-8601 date/time string).
	 * - `name` (string): Name of page that was matched in default language.
	 * - `urlSegmentStr` (string): Portion of path that was identified as URL segments (for partial match).
	 * - `matchType` (string): Contains value “exact” when exact match, “partial” when partial/URL segments 
	 *    match, or blank string when no match.
	 * 
	 * Note that the `urlSegmentStr` and `matchType` properties may only be of interest if the
	 * given `allowUrlSegments` option is set to `true`. 
	 * 
	 * @param string $path
	 * @param array $options
	 *  - `allowUrlSegments` (bool): Allow matching paths with URL segments? (default=false)
	 *     When used, the `urlSegmentStr` return value property will be populated with slash
	 *     separated URL segments that were not part of the matched path, and the `matchType`
	 *     property will contain the value “partial”. 
	 * @return array
	 * @since 3.0.186
	 * 
	 */
	public function getPathInfo($path, array $options = array()) {
		
		$defaults = array(
			'allowUrlSegments' => false,
		);
	
		$options = array_merge($defaults, $options);
		$sanitizer = $this->wire()->sanitizer;
		$templates = $this->wire()->templates;
		$database = $this->wire()->database;
		$config = $this->wire()->config;
		$table = self::dbTableName;
		$path = '/' . trim($path, '/');
		$originalPath = $path; // original path (without ascii conversion)
		$namesUTF8 = $config->pageNameCharset === 'UTF8';
		
		$result = array(
			'id' => 0,
			'path' => $path,
			'language_id' => 0,
			'templates_id' => 0,
			'parent_id' => 0,
			'created' => '',
			'status' => 0,
			'name' => '',
			'matchType' => '',
			'urlSegmentStr' => '',
		);
		
		if($namesUTF8) $path = $sanitizer->pagePathName($path, Sanitizer::toAscii);
		$requestPath = $path; // path that was requested (with ascii conversion)

		$wheres = array("$table.path=:path");
		$binds['path'] = $requestPath;
		
		if($options['allowUrlSegments']) {
			$n = 0;
			while(strlen($path)) {
				$pos = strrpos($path, '/'); 
				if(!$pos) break;
				$path = substr($path, 0, $pos);
				$wheres[] = "$table.path=:path$n";
				$binds["path$n"] = rtrim($path, '/');
				$n++;
			}
		}
	
		$sql = 
			"SELECT $table.path AS path, $table.pages_id AS id, $table.created AS created, $table.language_id AS language_id, " . 
			"pages.templates_id AS templates_id, pages.parent_id AS parent_id, pages.status AS status, pages.name AS name " . 
			"FROM $table " . 
			"LEFT JOIN pages ON $table.pages_id=pages.id " . 
			"WHERE " . implode(' OR ', $wheres);
		
		
		try {
			$query = $database->prepare($sql);
			foreach($binds as $bindKey => $bindValue) {
				$query->bindValue(":$bindKey", $bindValue);
			}
			$query->execute();
			$rowCount = $query->rowCount();
			$query->closeCursor();
		} catch(\Exception $e) {
			if(!$this->checkTableSchema()) throw $e;
			$rowCount = 0;
			$query = null;
		}
		
		if(!$rowCount || $query) return $result;
		
		$rows = array();
		$pathCounts = array();
		$matchRow = null;
		
		while($row = $query->fetch(\PDO::FETCH_ASSOC)) {
			
			$path = $row['path'];
			
			if($path === $requestPath) {
				// found exact match
				$matchRow = $row;
				break;
			} else {
				// path with urlSegments match
				$rows[$path] = $row;
				$pathCounts[$path] = substr_count($path, '/');
			}
		}
		
		$query->closeCursor();
		
		if($matchRow) {
			// ok found
			$result['matchType'] = 'exact';
		} else {
			// select from multiple matched rows (urlSegments mode only)
			// order by quantity of slashes (most to least)
			arsort($pathCounts);
			// find first row that has a template allowing URL segments
			foreach($pathCounts as $path => $count) {
				$row = $rows[$path];
				$template = $templates->get((int) $row['templates_id']);
				if(!$template || !$template->urlSegments) continue;
				$matchRow = $row;
				$result['matchType'] = 'partial';
				break;
			}
		}
		
		if($matchRow) {
			$result = array_merge($result, $matchRow);
		}
	
		// if no match return now
		if(!$result['id']) return $result;
		
		foreach($result as $key => $value) {
			if($key === 'id' || $key === 'status' || strpos($key, '_id')) {
				$result[$key] = (int) $value;
			} else if($key === 'path' && $namesUTF8) {
				$result['path'] = $sanitizer->pagePathName($value, Sanitizer::toUTF8);
			} else if($key === 'name' && $namesUTF8) {
				$result['name'] = $sanitizer->pageName($value, Sanitizer::toUTF8);
			}
		}
		
		if($result['matchType'] === 'partial') {
			$result['urlSegmentStr'] = trim(substr($originalPath, strlen($result['path'])+1), '/');
		}
		
		return $result;
	}

	/**
	 * Given a previously existing path, return the matching Page object or NullPage if not found.
	 * 
	 * If the path is for a specific language, this method also sets a $page->_language property
	 * containing the Language object the path is for. 
	 *
	 * @param string $path Historical path of page you want to retrieve
	 * @param int $level Recursion level for internal recursive use only
	 * @return Page|NullPage
	 *
	 */
	public function getPage($path, $level = 0) {
		
		$pages = $this->wire()->pages;
		$page = $pages->newNullPage();
		$sanitizer = $this->wire()->sanitizer;
		$languages = $this->getLanguages();
		$database = $this->wire()->database;
		$table = self::dbTableName;
		$pathRemoved = '';
		$cnt = 0;
		
		if(!$level) {
			$path = $sanitizer->pagePathName($path, Sanitizer::toAscii);
			if(!$this->isRootSegment($path)) return $pages->newNullPage();
		}
		
		$path = '/' . trim($path, '/');

		while(strlen($path) && !$page->id && $cnt < self::maxSegments) {

			$sql = "SELECT pages_id ";
			if($languages) $sql .= ", language_id ";
			$sql .= "FROM $table WHERE path=:path";
			$query = $database->prepare($sql);
			$query->bindValue(":path", $path); 
			$error = false;
			
			try {
				$query->execute();
			} catch(\Exception $e) {
				if(strpos($e->getMessage(), '1054') !== false) $this->upgrade(1, 2);
				$this->wire()->log->error('PagePathHistory::getPage() - ' . $e->getMessage());
				$error = true;
			}
			
			if($error) break;
			
			if($query->rowCount() > 0) {
				// found a match
				$row = $query->fetch(\PDO::FETCH_NUM);
				$pages_id = (int) $row[0];
				$language_id = $languages && isset($row[1]) ? $row[1] : 0;
				$page = $this->pages->get((int) $pages_id);
				if($language_id) $page->setQuietly("_language", $this->getLanguage($language_id));
			} else {
				// didn't find a match, we'll pop the last segment off and try again for the parent
				$pos = strrpos($path, '/');
				$pathRemoved = substr($path, $pos) . $pathRemoved;
				$path = substr($path, 0, $pos);
			}
			
			$query->closeCursor();
			$cnt++;
		} 

		// if no page was found, then we can stop trying now
		if(!$page->id) return $page; 

		if($cnt > 1) {
			// a parent match was found if our counter is > 1
			$parent = $page; 
			// use the new parent path and add the removed components back on to it
			$path = rtrim($parent->path, '/') . $pathRemoved; 
			// see if it might exist at the new parent's URL
			$page = $pages->getByPath($path, array(
				'useHistory' => false,
				'useLanguages' => $languages ? true : false
			)); 
			if($page->id) {
				// found a page
				$languagePageNames = $languages ? $languages->pageNames() : null;
				if($languagePageNames) {
					$language = $languagePageNames->getPagePathLanguage($path, $page);
					if($language) $page->setQuietly('_language', $language);
				}
			} else if($level < self::maxSegments) {
				// if not, then go recursive, trying again
				$page = $this->getPage($path, $level + 1);
			}
		}
		
		return $page; 	
	}

	/*** ROOT SEGMENTS ***********************************************************/
	
	/**
	 * Get all root segments
	 *
	 * @return array
	 * @since 3.0.186
	 *
	 */
	public function getRootSegments() {
		if(is_array($this->rootSegments)) return $this->rootSegments;
		return $this->rebuildRootSegments();
	}

	/**
	 * Is/was given segment ever a root segment?
	 * 
	 * @param string $segment Segment or path containing it (in ascii format)
	 * @return bool
	 * @since 3.0.186
	 * 
	 */
	public function isRootSegment($segment) {
		$segment = trim($segment, '/');
		if(strpos($segment, '/')) list($segment,) = explode('/', $segment, 2);
		$segments = $this->getRootSegments();
		return in_array($segment, $segments, true);
	}

	/**
	 * Add a root segment
	 *
	 * @param string $segment May be a segment or path to extract it from (in ascii format)
	 * @return bool True if added, false if it was already present
	 * @since 3.0.186
	 *
	 */
	protected function addRootSegment($segment) {
		$segment = trim($segment, '/');
		if(strpos($segment, '/')) list($segment,) = explode('/', $segment, 2);
		$rootSegments = $this->rootSegments;
		if(!is_array($rootSegments)) $rootSegments = array();
		if(in_array($segment, $rootSegments, true)) return false;
		$rootSegments[] = $segment;
		$this->rootSegments = $rootSegments;
		$this->wire()->modules->saveConfig($this, 'rootSegments', $rootSegments);
		return true;
	}

	/**
	 * Rebuild all root segments
	 *
	 * @return array
	 * @since 3.0.186
	 *
	 */
	protected function rebuildRootSegments() {
		$segments = array();
		$sql = 'SELECT path FROM ' . self::dbTableName;
		$query = $this->wire()->database->prepare($sql);
		$query->execute();
		while($row = $query->fetch(\PDO::FETCH_NUM)) {
			$path = trim($row[0], '/');
			list($segment,) = explode('/', $path, 2);
			$segments[$segment] = $segment;
		}
		$query->closeCursor();
		$segments = array_values($segments);
		$this->rootSegments = $segments;
		$this->wire()->modules->saveConfig($this, 'rootSegments', $segments);
		return $segments;
	}
	
	/*** HOOKS *******************************************************************/
	
	/**
	 * Hook called when a page is moved or renamed
	 *
	 * @param HookEvent $event
	 *
	 */
	public function hookPageMoved(HookEvent $event) {

		/** @var Page $page */
		$page = $event->arguments[0];
		/** @var Languages $languages */
		$languages = $this->getLanguages();

		$age = time() - $page->created;
		if($page->template->name === 'admin' || $this->wire()->pages->cloning || $age < $this->minimumAge) return;

		// note that the paths we store have no trailing slash

		if($languages) {
			$parent = $page->parent();
			$parentPrevious = $page->parentPrevious;
			if($parentPrevious && $parentPrevious->id == $parent->id) $parentPrevious = null;
			foreach($languages as $language) {
				/** @var Language $language */
				if($language->isDefault()) continue;
				$namePrevious = $page->get("-name$language");
				if(!$namePrevious && !$parentPrevious) continue;
				if(!$namePrevious) $namePrevious = $page->name;
				$languages->setLanguage($language);
				$pathPrevious = $parentPrevious ? $parentPrevious->path() : $page->parent()->path();
				$pathPrevious = rtrim($pathPrevious, '/') . "/$namePrevious";
				$this->setPathHistory($page, $pathPrevious, $language->id);
				$languages->unsetLanguage();
			}
		}

		if(!$page->namePrevious) {
			// abort saving a former URL if it looks like there isn't going to be one
			if(!$page->parentPrevious || $page->parentPrevious->id == $page->parent->id) return;
		}

		if($page->parentPrevious) {

			// if former or current parent is in trash, then don't bother saving redirects
			if($page->parentPrevious->isTrash() || $page->parent->isTrash()) return;

			// the start of our redirect URL will be the previous parent's URL
			$path = $page->parentPrevious->path;

		} else {
			// the start of our redirect URL will be the current parent's URL (i.e. name changed)
			$path = $page->parent->path;
		}

		if($page->namePrevious) {
			$path = rtrim($path, '/') . '/' . $page->namePrevious;
		} else {
			$path = rtrim($path, '/') . '/' . $page->name;
		}

		// do not save paths that reference recovery format used by trash
		// example: /blog/posts/5134.3096.83_page-name
		if(strpos($path, '.') !== false && strpos($path, '_') !== false) {
			if(preg_match('!/\d+\.\d+\.\d+_!', $path)) return;
		}

		// do not save paths that match any untitled page name
		// example: /blog/posts/untitled-123123
		$untitled = $this->wire()->pages->names()->untitledPageName();
		if(strpos($path, $untitled) !== false) {
			if(preg_match('!/' . preg_quote($untitled) . '[-]!', $path)) return;
		}

		if($languages) $languages->setDefault();
		$this->setPathHistory($page, $path);
		if($languages) $languages->unsetDefault();
	}

	/**
	 * Hook called upon 404 from ProcessPageView::pageNotFound
	 *
	 * @param HookEvent $event
	 *
	 */
	public function hookPageNotFound(HookEvent $event) {

		/** @var Page $page */
		$page = $event->arguments(0);
		/** @var Wire404Exception $exception */
		$exception = $event->arguments(4);

		// If there is a page object set, then it means the 404 was triggered
		// by the user not having access to it, or by the $page's template 
		// throwing a 404 exception. In either case, we don't want to do a 
		// redirect if there is a $page since any 404 is intentional there.
		if($page && $page->id) {
			// it did resolve to a Page: maybe a front-end 404
			if(!$exception) {
				// pageNotFound was called without an Exception
				return;
			} else if($exception->getCode() == Wire404Exception::codeFunction) {
				// the wire404() function was called: allow PagePathHistory
			} else if($exception->getMessage() === "1") {
				// also allow PagePathHistory to operate when: throw new WireException(true);
			} else {
				// likely user didn't have access or intentional 404 that should not redirect
				return;
			}
		}

		$languages = $this->getLanguages();
		$languagePageNames = $languages ? $languages->pageNames() : null;
		if($languagePageNames) {
			// the LanguageSupportPageNames may change the original requested path, so we ask it for the original
			$path = $languagePageNames->getRequestPath();
			$path = $path ? $this->wire()->sanitizer->pagePathName($path) : $event->arguments(1);
		} else {
			$path = $event->arguments(1);
		}

		$page = $this->getPage($path);

		if($page->id && $page->viewable()) {
			// if a page was found, redirect to it...
			$language = $page->get('_language');
			if($language && $languages) {
				// ...optionally for a specific language
				if($page->get("status$language")) {
					$languages->setLanguage($language);
				}
			}
			$this->session->redirect($page->url);
		}
	}

	/**
	 * When a page is deleted, remove it from our redirects list as well
	 * 
	 * @param HookEvent $event
	 *
	 */
	public function hookPageDeleted(HookEvent $event) {
		$page = $event->arguments[0];
		$database = $this->wire()->database;
		$table = self::dbTableName;
		$query = $database->prepare("DELETE FROM $table WHERE pages_id=:pages_id"); 
		$query->bindValue(":pages_id", $page->id, \PDO::PARAM_INT);
		$query->execute();
	}

	/**
	 * Implementation for $page->addUrl($url, [$language]) method
	 * 
	 * @param HookEvent $event
	 * 
	 */
	public function hookPageAddUrl(HookEvent $event) {
		/** @var Page $page */
		$page = $event->object; 
		/** @var string $url */
		$url = $event->arguments(0);
		/** @var Language|null $language */
		$language = $event->arguments(1);
		$event->return = $this->addPathHistory($page, $this->urlToPath($url), $language); 
	}
	
	/**
	 * Implementation for $page->removeUrl($url, [$language]) method
	 *
	 * @param HookEvent $event
	 *
	 */
	public function hookPageRemoveUrl(HookEvent $event) {
		/** @var page $page */
		$page = $event->object;
		/** @var string $url */
		$url = $event->arguments(0);
		$event->return = (bool) $this->deletePathHistory($page, $this->urlToPath($url));
	}
	
	/*** MODULE ******************************************************************/

	/**
	 * Given URL that may include a root subdirectory, convert it to path relative to root subdirectory
	 * 
	 * @param string $url
	 * @return string
	 * 
	 */
	protected function urlToPath($url) {
		$rootUrl = $this->wire()->config->urls->root;
		if(strlen($rootUrl) > 1 && strpos($url, $rootUrl) === 0) {
			$path = substr($url, strlen($rootUrl) - 1);
		} else {
			$path = $url;
		}
		return $path;
	}

	/**
	 * Check table schema and update as needed
	 * 
	 * @return bool True if schema updated, false if not
	 * 
	 */
	protected function checkTableSchema() {
		
		$database = $this->wire()->database;
		$table = self::dbTableName;
		$updated = false;
		
		if(!$database->columnExists($table, 'language_id')) {
			try {
				$database->exec("ALTER TABLE $table ADD language_id INT UNSIGNED DEFAULT 0");
				$this->message("Added 'language_id' column to table $table", Notice::debug); 
				$updated = true;
			} catch(\Exception $e) {
				$this->error($e->getMessage(), Notice::superuser | Notice::log);
			}
		}
		
		return $updated;
	}

	/**
	 * Install
	 * 
	 */
	public function ___install() {
	
		$database = $this->wire()->database;
		$len = $database->getMaxIndexLength();
		$table = self::dbTableName;
	
		if($database->tableExists($table)) {
			$this->checkTableSchema();
			return;
		}

		$sql = 	
			"CREATE TABLE $table (" . 
			"path VARCHAR($len) NOT NULL, " . 
			"pages_id INT UNSIGNED NOT NULL, " .
			"language_id INT UNSIGNED DEFAULT 0, " . // v2
			"created TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP, " . 
			"PRIMARY KEY path (path), " . 
			"INDEX pages_id (pages_id), " . 
			"INDEX created (created) " . 
			") ENGINE={$this->config->dbEngine} DEFAULT CHARSET={$this->config->dbCharset}";

		$database->exec($sql);
	}

	/**
	 * Uninstall
	 * 
	 */
	public function ___uninstall() {
		$this->wire()->database->query("DROP TABLE " . self::dbTableName); 
	}

	/**
	 * Upgrade PagePathHistory module schema
	 * 
	 * @param int $fromVersion
	 * @param int $toVersion
	 * 
	 */
	public function ___upgrade($fromVersion, $toVersion) {
		if($this->checkTableSchema()) { 
			if($fromVersion != $toVersion) $this->message("PagePathHistory v$fromVersion => v$toVersion");
		}
		$this->rebuildRootSegments();
	}

	/**
	 * Module config
	 * 
	 * @param InputfieldWrapper $inputfields
	 * 
	 */
	public function getModuleConfigInputfields(InputfieldWrapper $inputfields) {
		$modules = $this->wire()->modules;
		
		/** @var InputfieldInteger $f */
		$f = $modules->get('InputfieldInteger');
		$f->attr('name', 'minimumAge');
		$f->label = $this->_('Minimum age (seconds)');
		$f->description = $this->_('Start recording history for a page this many seconds after it has been created. At least 2 or more seconds recommended.');
		$f->notes = sprintf($this->_('Default: %s'), self::minimumAge);
		$f->val((int) $this->minimumAge);
		$f->required = true;
		$inputfields->add($f);
		
		$query = $this->wire()->database->query('SELECT COUNT(*) FROM ' . self::dbTableName);
		$numPaths = (int) $query->fetchColumn();
		$query->closeCursor();

		if($numPaths) {
			$input = $this->wire()->input;
			$deleteNow = $input->post('_deleteAll') && $input->post('_deleteAllConfirm') === "$numPaths";
			
			if($deleteNow) {
				$this->deleteAllPathHistory(true);
				$inputfields->message(sprintf($this->_('Deleted %d historical page paths'), $numPaths));
				$numPaths = 0;
			}

			/** @var InputfieldCheckbox $f */
			$f = $modules->get('InputfieldCheckbox');
			$f->attr('name', '_deleteAll');
			$f->attr('value', 1);
			$f->label = $this->_('Delete all page path history?');
			$f->description = sprintf($this->_('There are currently %d historical page paths in the database.'), $numPaths);
			$f->collapsed = Inputfield::collapsedYes;
			$inputfields->add($f);

			/** @var InputfieldCheckbox $f */
			$f = $modules->get('InputfieldCheckbox');
			$f->attr('name', '_deleteAllConfirm');
			$f->attr('value', 1);
			$f->label = $this->_('Are you sure?');
			$f->description = $this->_('This information is used for automatic redirects and more. It cannot be recovered once deleted. Check the box to confirm you really want to do this.');
			$f->showIf = '_deleteAll=1';
			$f->val($numPaths);
			$inputfields->add($f);
		}
	}

}