<?php

/**
 * 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 2.x 
 * Copyright (C) 2014 by Ryan Cramer 
 * Licensed under GNU/GPL v2, see LICENSE.TXT
 * 
 * http://processwire.com
 * 
 *
 */

class PagePathHistory extends WireData implements Module {

	public static function getModuleInfo() {
		return array(
			'title' => 'Page Path History', 
			'version' => 1, 
			'summary' => "Keeps track of past URLs where pages have lived and automatically redirects (301 permament) 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 it's 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; 


	/**
	 * 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'); 
	}

	/**
	 * Hook called when a page is moved or renamed
	 *
	 */
	public function hookPageMoved(HookEvent $event) {

		$page = $event->arguments[0];
		if($page->template == 'admin') return;
		$age = time() - $page->created; 
		if($age < self::minimumAge) return;

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

		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 .= $page->namePrevious; 
			else $path .= $page->name; 


		$database = $this->wire('database');	
	
		$query = $database->prepare("INSERT INTO " . self::dbTableName . " SET path=:path, pages_id=:pages_id, created=NOW()");
		$query->bindValue(":path", $path); 
		$query->bindValue(":pages_id", $page->id, PDO::PARAM_INT);

		try {
			$query->execute();

		} catch(Exception $e) {
			// catch the exception because it means there is already a past URL (duplicate)
		}

		// delete any possible entries that overlap with the $page since are no longer applicable
		$query = $database->prepare("DELETE FROM " . self::dbTableName . " WHERE path=:path LIMIT 1");
		$query->bindValue(":path", rtrim($page->path, '/'));
		$query->execute();
	}

	/**
	 * Hook called upon 404 from ProcessPageView::pageNotFound
	 *
	 */
	public function hookPageNotFound(HookEvent $event) {
		
		$page = $event->arguments[0]; 

		// 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) return; 

		$path = $event->arguments[1];
		$page = $this->getPage($path);

		if($page->id && $page->viewable()) {
			// if a page was found, redirect to it
			$this->session->redirect($page->url);
		}
		
	}

	/**
	 * Given a previously existing path, return the matching Page object or NullPage if not found.
	 *
	 * @param string $path Historical path of page you want to retrieve
	 * @param int $level Recursion level for internal recursive use only
	 * @return Page|NullPage
	 *
	 */
	protected function getPage($path, $level = 0) {

		$page = new NullPage();
		$pathRemoved = '';
		$path = rtrim($path, '/');
		$cnt = 0;
		$database = $this->wire('database');

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

			$query = $database->prepare("SELECT pages_id FROM " . self::dbTableName . " WHERE path=:path");
			$query->bindValue(":path", $path); 
			$query->execute();
			if($query->rowCount() > 0) {
				$pages_id = $query->fetchColumn();
				$page = $this->pages->get((int) $pages_id);
			} else {
				$pos = strrpos($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 = $this->pages->get($path); 
			// if not, then go recursive, trying again
			if(!$page->id && $level < self::maxSegments) $page = $this->getPage($path, $level+1); 
		}
	
		return $page; 	
	}

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

	public function ___install() {

		$sql = 	"CREATE TABLE " . self::dbTableName . " (" . 
				"path VARCHAR(255) NOT NULL, " . 
				"pages_id INT UNSIGNED NOT NULL, " . 
				"created TIMESTAMP NOT NULL, " . 
				"PRIMARY KEY path (path), " . 
				"INDEX pages_id (pages_id), " . 
				"INDEX created (created) " . 
				") ENGINE={$this->config->dbEngine} DEFAULT CHARSET={$this->config->dbCharset}";

		$this->wire('database')->exec($sql); 

	}

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

}