<?php
/*
 * @copyright   Copyright (C) 2010-2022 Combodo SARL
 * @license     http://opensource.org/licenses/AGPL-3.0
 */

namespace Combodo\iTop\Router;

use utils;

/**
 * Class Router
 *
 * Service to find the corresponding controller / method for a given "route" parameter
 *
 * @author Guillaume Lajarige <guillaume.lajarige@combodo.com>
 * @package Combodo\iTop\Router
 * @since 3.1.0
 * @internal
 */
class Router
{
	/** @var \Combodo\iTop\Router\Router|null Singleton instance */
	protected static ?Router $oSingleton = null;

	/**
	 * @return $this The singleton instance of the router
	 */
	public static function GetInstance()
	{
		if (null === static::$oSingleton) {
			static::$oSingleton = new static();
		}

		return static::$oSingleton;
	}

	/**********************/
	/* Non-static methods */
	/**********************/

	/**
	 * Singleton pattern, can't use the constructor. Use {@see \Combodo\iTop\Router\Router::GetInstance()} instead.
	 *
	 * @return void
	 */
	private function __construct()
	{
		// Don't do anything, we don't want to be initialized
	}

	/**
	 * @param string $sRoute
	 *
	 * @return bool True if there is a matching handler for $sRoute
	 */
	public function CanDispatchRoute(string $sRoute): bool
	{
		return $this->GetDispatchSpecsForRoute($sRoute) !== null;
	}

	/**
	 * Dispatch the current request to the matching handler for $sRoute
	 *
	 * @param string $sRoute
	 *
	 * @return mixed Response from the route's handler, can be anything.
	 *               Even though it can be anything, in most cases, response will either be:
	 *               - A \WebPage for usual backoffice operations
	 *               - null for TwigBase backoffice operations
	 */
	public function DispatchRoute(string $sRoute)
	{
		$aMethodSpecs = $this->GetDispatchSpecsForRoute($sRoute);
		$mResponse = call_user_func_array([new $aMethodSpecs[0](), $aMethodSpecs[1]], []);

		return $mResponse;
	}

	/**
	 * @param string $sRoute
	 *
	 * @return array{sControllerFQCN, sOperationMethodName}|null The FQCN controller and operation method matching $sRoute, null if no matching handler
	 */
	public function GetDispatchSpecsForRoute(string $sRoute)
	{
		$aRouteParts = $this->GetRouteParts($sRoute);
		if (is_null($aRouteParts)) {
			return null;
		}

		$sRouteNamespace = $aRouteParts['namespace'];
		$sRouteOperation = $aRouteParts['operation'];
		$sControllerFQCN = $this->FindControllerFromRouteNamespace($sRouteNamespace);
		if (utils::IsNullOrEmptyString($sControllerFQCN)) {
			return null;
		}

		$sOperationMethodName = $this->MakeOperationMethodNameFromOperation($sRouteOperation);
		$aMethodSpecs = [$sControllerFQCN, $sOperationMethodName];
		if (false === is_callable($aMethodSpecs)) {
			return null;
		}

		return $aMethodSpecs;
	}

	/**
	 * @param string $sRoute
	 *
	 * @return array{namespace: string, operation: string}|null Route parts (namespace and operation) if route can be parsed, null otherwise
	 */
	public function GetRouteParts(string $sRoute)
	{
		if (utils::IsNullOrEmptyString($sRoute)) {
			return null;
		}

		$sRouteNamespace = $this->GetRouteNamespace($sRoute);
		$sRouteOperation = $this->GetRouteOperation($sRoute);
		if (utils::IsNullOrEmptyString($sRouteNamespace) || utils::IsNullOrEmptyString($sRouteOperation)) {
			return null;
		}

		return ['namespace' => $sRouteNamespace, 'operation' => $sRouteOperation];
	}

	/**
	 * @param string $sRoute
	 *
	 * @return string|null Namespace of the route (eg. "object" for "object.modify") if route can be parsed null otherwise
	 */
	public function GetRouteNamespace(string $sRoute): ?string
	{
		$mSeparatorPos = strripos($sRoute, '.', -1);
		if (false === $mSeparatorPos) {
			return null;
		}

		return substr($sRoute, 0, $mSeparatorPos);
	}

	/**
	 * @param string $sRoute
	 *
	 * @return string|null Operation of the route (eg. "modify" for "object.modify") if route can be parsed null otherwise
	 */
	public function GetRouteOperation(string $sRoute): ?string
	{
		$mSeparatorPos = strripos($sRoute, '.', -1);
		if (false === $mSeparatorPos) {
			return null;
		}

		return substr($sRoute, $mSeparatorPos + 1);
	}

	/**
	 * @param string $sRouteNamespace {@see static::$sRouteNamespace}
	 *
	 * @return string|null The FQCN of the controller matching the $sRouteNamespace, null if none matching.
	 */
	protected function FindControllerFromRouteNamespace(string $sRouteNamespace): ?string
	{
		foreach (utils::GetClassesForInterface('Combodo\iTop\Controller\iController', '', ['[\\\\/]lib[\\\\/]', '[\\\\/]node_modules[\\\\/]', '[\\\\/]test[\\\\/]']) as $sControllerFQCN) {
			if ($sControllerFQCN::ROUTE_NAMESPACE === $sRouteNamespace) {
				return $sControllerFQCN;
			}
		}

		return null;
	}

	/**
	 * @param string $sOperation
	 *
	 * @return string The method name for the $sOperation regarding the convention
	 */
	protected function MakeOperationMethodNameFromOperation(string $sOperation): string
	{
		return 'Operation'.utils::ToCamelCase($sOperation);
	}
}