<?php

declare(strict_types=1);

/**
 * This file is part of CodeIgniter 4 framework.
 *
 * (c) CodeIgniter Foundation <admin@codeigniter.com>
 *
 * For the full copyright and license information, please view
 * the LICENSE file that was distributed with this source code.
 */

namespace CodeIgniter\Router;

use CodeIgniter\Exceptions\PageNotFoundException;
use CodeIgniter\Router\Exceptions\MethodNotFoundException;
use Config\Routing;
use ReflectionClass;
use ReflectionException;

/**
 * New Secure Router for Auto-Routing
 *
 * @see \CodeIgniter\Router\AutoRouterImprovedTest
 */
final class AutoRouterImproved implements AutoRouterInterface
{
    /**
     * Sub-directory that contains the requested controller class.
     */
    private ?string $directory = null;

    /**
     * The name of the controller class.
     */
    private string $controller;

    /**
     * The name of the method to use.
     */
    private string $method;

    /**
     * An array of params to the controller method.
     *
     * @var list<string>
     */
    private array $params = [];

    /**
     *  Whether to translate dashes in URIs for controller/method to CamelCase.
     *  E.g., blog-controller -> BlogController
     */
    private readonly bool $translateUriToCamelCase;

    /**
     * The namespace for controllers.
     */
    private string $namespace;

    /**
     * Map of URI segments and namespaces.
     *
     * The key is the first URI segment. The value is the controller namespace.
     * E.g.,
     *   [
     *       'blog' => 'Acme\Blog\Controllers',
     *   ]
     *
     * @var array [ uri_segment => namespace ]
     */
    private array $moduleRoutes;

    /**
     * The URI segments.
     *
     * @var list<string>
     */
    private array $segments = [];

    /**
     * The position of the Controller in the URI segments.
     * Null for the default controller.
     */
    private ?int $controllerPos = null;

    /**
     * The position of the Method in the URI segments.
     * Null for the default method.
     */
    private ?int $methodPos = null;

    /**
     * The position of the first Parameter in the URI segments.
     * Null for the no parameters.
     */
    private ?int $paramPos = null;

    /**
     * The current URI
     */
    private ?string $uri = null;

    /**
     * @param list<class-string> $protectedControllers
     * @param string             $defaultController    Short classname
     */
    public function __construct(
        /**
         * List of controllers in Defined Routes that should not be accessed via this Auto-Routing.
         */
        private readonly array $protectedControllers,
        string $namespace,
        private readonly string $defaultController,
        /**
         * The name of the default method without HTTP verb prefix.
         */
        private readonly string $defaultMethod,
        /**
         * Whether dashes in URI's should be converted
         * to underscores when determining method names.
         */
        private readonly bool $translateURIDashes
    ) {
        $this->namespace = rtrim($namespace, '\\');

        $routingConfig                 = config(Routing::class);
        $this->moduleRoutes            = $routingConfig->moduleRoutes;
        $this->translateUriToCamelCase = $routingConfig->translateUriToCamelCase;

        // Set the default values
        $this->controller = $this->defaultController;
    }

    private function createSegments(string $uri): array
    {
        $segments = explode('/', $uri);
        $segments = array_filter($segments, static fn ($segment): bool => $segment !== '');

        // numerically reindex the array, removing gaps
        return array_values($segments);
    }

    /**
     * Search for the first controller corresponding to the URI segment.
     *
     * If there is a controller corresponding to the first segment, the search
     * ends there. The remaining segments are parameters to the controller.
     *
     * @return bool true if a controller class is found.
     */
    private function searchFirstController(): bool
    {
        $segments = $this->segments;

        $controller = '\\' . $this->namespace;

        $controllerPos = -1;

        while ($segments !== []) {
            $segment = array_shift($segments);
            $controllerPos++;

            $class = $this->translateURI($segment);

            // as soon as we encounter any segment that is not PSR-4 compliant, stop searching
            if (! $this->isValidSegment($class)) {
                return false;
            }

            $controller .= '\\' . $class;

            if (class_exists($controller)) {
                $this->controller    = $controller;
                $this->controllerPos = $controllerPos;

                $this->checkUriForController($controller);

                // The first item may be a method name.
                $this->params = $segments;
                if ($segments !== []) {
                    $this->paramPos = $this->controllerPos + 1;
                }

                return true;
            }
        }

        return false;
    }

    /**
     * Search for the last default controller corresponding to the URI segments.
     *
     * @return bool true if a controller class is found.
     */
    private function searchLastDefaultController(): bool
    {
        $segments = $this->segments;

        $segmentCount = count($this->segments);
        $paramPos     = null;
        $params       = [];

        while ($segments !== []) {
            if ($segmentCount > count($segments)) {
                $paramPos = count($segments);
            }

            $namespaces = array_map(
                fn ($segment): string => $this->translateURI($segment),
                $segments
            );

            $controller = '\\' . $this->namespace
                . '\\' . implode('\\', $namespaces)
                . '\\' . $this->defaultController;

            if (class_exists($controller)) {
                $this->controller = $controller;
                $this->params     = $params;

                if ($params !== []) {
                    $this->paramPos = $paramPos;
                }

                return true;
            }

            // Prepend the last element in $segments to the beginning of $params.
            array_unshift($params, array_pop($segments));
        }

        // Check for the default controller in Controllers directory.
        $controller = '\\' . $this->namespace
            . '\\' . $this->defaultController;

        if (class_exists($controller)) {
            $this->controller = $controller;
            $this->params     = $params;

            if ($params !== []) {
                $this->paramPos = 0;
            }

            return true;
        }

        return false;
    }

    /**
     * Finds controller, method and params from the URI.
     *
     * @param string $httpVerb HTTP verb like `GET`,`POST`
     *
     * @return array [directory_name, controller_name, controller_method, params]
     */
    public function getRoute(string $uri, string $httpVerb): array
    {
        $this->uri = $uri;
        $httpVerb  = strtolower($httpVerb);

        // Reset Controller method params.
        $this->params = [];

        $defaultMethod = $httpVerb . ucfirst($this->defaultMethod);
        $this->method  = $defaultMethod;

        $this->segments = $this->createSegments($uri);

        // Check for Module Routes.
        if (
            $this->segments !== []
            && array_key_exists($this->segments[0], $this->moduleRoutes)
        ) {
            $uriSegment      = array_shift($this->segments);
            $this->namespace = rtrim($this->moduleRoutes[$uriSegment], '\\');
        }

        if ($this->searchFirstController()) {
            // Controller is found.
            $baseControllerName = class_basename($this->controller);

            // Prevent access to default controller path
            if (
                strtolower($baseControllerName) === strtolower($this->defaultController)
            ) {
                throw new PageNotFoundException(
                    'Cannot access the default controller "' . $this->controller . '" with the controller name URI path.'
                );
            }
        } elseif ($this->searchLastDefaultController()) {
            // The default Controller is found.
            $baseControllerName = class_basename($this->controller);
        } else {
            // No Controller is found.
            throw new PageNotFoundException('No controller is found for: ' . $uri);
        }

        // The first item may be a method name.
        /** @var list<string> $params */
        $params = $this->params;

        $methodParam = array_shift($params);

        $method = '';
        if ($methodParam !== null) {
            $method = $httpVerb . $this->translateURI($methodParam);

            $this->checkUriForMethod($method);
        }

        if ($methodParam !== null && method_exists($this->controller, $method)) {
            // Method is found.
            $this->method = $method;
            $this->params = $params;

            // Update the positions.
            $this->methodPos = $this->paramPos;
            if ($params === []) {
                $this->paramPos = null;
            }
            if ($this->paramPos !== null) {
                $this->paramPos++;
            }

            // Prevent access to default controller's method
            if (strtolower($baseControllerName) === strtolower($this->defaultController)) {
                throw new PageNotFoundException(
                    'Cannot access the default controller "' . $this->controller . '::' . $this->method . '"'
                );
            }

            // Prevent access to default method path
            if (strtolower($this->method) === strtolower($defaultMethod)) {
                throw new PageNotFoundException(
                    'Cannot access the default method "' . $this->method . '" with the method name URI path.'
                );
            }
        } elseif (method_exists($this->controller, $defaultMethod)) {
            // The default method is found.
            $this->method = $defaultMethod;
        } else {
            // No method is found.
            throw PageNotFoundException::forControllerNotFound($this->controller, $method);
        }

        // Ensure the controller is not defined in routes.
        $this->protectDefinedRoutes();

        // Ensure the controller does not have _remap() method.
        $this->checkRemap();

        // Ensure the URI segments for the controller and method do not contain
        // underscores when $translateURIDashes is true.
        $this->checkUnderscore();

        // Check parameter count
        try {
            $this->checkParameters();
        } catch (MethodNotFoundException) {
            throw PageNotFoundException::forControllerNotFound($this->controller, $this->method);
        }

        $this->setDirectory();

        return [$this->directory, $this->controller, $this->method, $this->params];
    }

    /**
     * @internal For test purpose only.
     *
     * @return array<string, int|null>
     */
    public function getPos(): array
    {
        return [
            'controller' => $this->controllerPos,
            'method'     => $this->methodPos,
            'params'     => $this->paramPos,
        ];
    }

    /**
     * Get the directory path from the controller and set it to the property.
     *
     * @return void
     */
    private function setDirectory()
    {
        $segments = explode('\\', trim($this->controller, '\\'));

        // Remove short classname.
        array_pop($segments);

        $namespaces = implode('\\', $segments);

        $dir = str_replace(
            '\\',
            '/',
            ltrim(substr($namespaces, strlen($this->namespace)), '\\')
        );

        if ($dir !== '') {
            $this->directory = $dir . '/';
        }
    }

    private function protectDefinedRoutes(): void
    {
        $controller = strtolower($this->controller);

        foreach ($this->protectedControllers as $controllerInRoutes) {
            $routeLowerCase = strtolower($controllerInRoutes);

            if ($routeLowerCase === $controller) {
                throw new PageNotFoundException(
                    'Cannot access the controller in Defined Routes. Controller: ' . $controllerInRoutes
                );
            }
        }
    }

    private function checkParameters(): void
    {
        try {
            $refClass = new ReflectionClass($this->controller);
        } catch (ReflectionException) {
            throw PageNotFoundException::forControllerNotFound($this->controller, $this->method);
        }

        try {
            $refMethod = $refClass->getMethod($this->method);
            $refParams = $refMethod->getParameters();
        } catch (ReflectionException) {
            throw new MethodNotFoundException();
        }

        if (! $refMethod->isPublic()) {
            throw new MethodNotFoundException();
        }

        if (count($refParams) < count($this->params)) {
            throw new PageNotFoundException(
                'The param count in the URI are greater than the controller method params.'
                . ' Handler:' . $this->controller . '::' . $this->method
                . ', URI:' . $this->uri
            );
        }
    }

    private function checkRemap(): void
    {
        try {
            $refClass = new ReflectionClass($this->controller);
            $refClass->getMethod('_remap');

            throw new PageNotFoundException(
                'AutoRouterImproved does not support `_remap()` method.'
                . ' Controller:' . $this->controller
            );
        } catch (ReflectionException) {
            // Do nothing.
        }
    }

    private function checkUnderscore(): void
    {
        if ($this->translateURIDashes === false) {
            return;
        }

        $paramPos = $this->paramPos ?? count($this->segments);

        for ($i = 0; $i < $paramPos; $i++) {
            if (str_contains($this->segments[$i], '_')) {
                throw new PageNotFoundException(
                    'AutoRouterImproved prohibits access to the URI'
                    . ' containing underscores ("' . $this->segments[$i] . '")'
                    . ' when $translateURIDashes is enabled.'
                    . ' Please use the dash.'
                    . ' Handler:' . $this->controller . '::' . $this->method
                    . ', URI:' . $this->uri
                );
            }
        }
    }

    /**
     * Check URI for controller for $translateUriToCamelCase
     *
     * @param string $classname Controller classname that is generated from URI.
     *                          The case may be a bit incorrect.
     */
    private function checkUriForController(string $classname): void
    {
        if ($this->translateUriToCamelCase === false) {
            return;
        }

        if (! in_array(ltrim($classname, '\\'), get_declared_classes(), true)) {
            throw new PageNotFoundException(
                '"' . $classname . '" is not found.'
            );
        }
    }

    /**
     * Check URI for method for $translateUriToCamelCase
     *
     * @param string $method Controller method name that is generated from URI.
     *                       The case may be a bit incorrect.
     */
    private function checkUriForMethod(string $method): void
    {
        if ($this->translateUriToCamelCase === false) {
            return;
        }

        if (
            // For example, if `getSomeMethod()` exists in the controller, only
            // the URI `controller/some-method` should be accessible. But if a
            // visitor navigates to the URI `controller/somemethod`, `getSomemethod()`
            // will be checked, and `method_exists()` will return true because
            // method names in PHP are case-insensitive.
            method_exists($this->controller, $method)
            // But we do not permit `controller/somemethod`, so check the exact
            // method name.
            && ! in_array($method, get_class_methods($this->controller), true)
        ) {
            throw new PageNotFoundException(
                '"' . $this->controller . '::' . $method . '()" is not found.'
            );
        }
    }

    /**
     * Returns true if the supplied $segment string represents a valid PSR-4 compliant namespace/directory segment
     *
     * regex comes from https://www.php.net/manual/en/language.variables.basics.php
     */
    private function isValidSegment(string $segment): bool
    {
        return (bool) preg_match('/^[a-zA-Z_\x80-\xff][a-zA-Z0-9_\x80-\xff]*$/', $segment);
    }

    /**
     * Translates URI segment to CamelCase or replaces `-` with `_`.
     */
    private function translateURI(string $segment): string
    {
        if ($this->translateUriToCamelCase) {
            if (strtolower($segment) !== $segment) {
                throw new PageNotFoundException(
                    'AutoRouterImproved prohibits access to the URI'
                    . ' containing uppercase letters ("' . $segment . '")'
                    . ' when $translateUriToCamelCase is enabled.'
                    . ' Please use the dash.'
                    . ' URI:' . $this->uri
                );
            }

            if (str_contains($segment, '--')) {
                throw new PageNotFoundException(
                    'AutoRouterImproved prohibits access to the URI'
                    . ' containing double dash ("' . $segment . '")'
                    . ' when $translateUriToCamelCase is enabled.'
                    . ' Please use the single dash.'
                    . ' URI:' . $this->uri
                );
            }

            return str_replace(
                ' ',
                '',
                ucwords(
                    preg_replace('/[\-]+/', ' ', $segment)
                )
            );
        }

        $segment = ucfirst($segment);

        if ($this->translateURIDashes) {
            return str_replace('-', '_', $segment);
        }

        return $segment;
    }
}