<?php

namespace Subcon\Zap\Routing;

use Subcon\Zap\Application;
use Subcon\Zap\Http\Response;

class Router
{
    /**
     * @var Application
     */
    private Application $app;

    /**
     * @var array
     */
    private array $routes;

    /**
     * @var string
     */
    private string $requestUri;

    /**
     * @var string
     */
    private string $requestMethod;

    /**
     * @var array
     */
    private array $requestHeaders;

    /**
     * @param Application $app
     */
    public function __construct(Application $app)
    {
        $this->app = $app;

        //Load routes from cache, or fall back to loading from file
        if($this->loadFromCache(realpath($app->getBasePath('cache')))) {
            return;
        }

        $this->loadFromRouteFile(realpath($app->getBasePath('routes')));
    }

    /**
     * @return void
     */
    public function run(): void
    {
        //Parse request
        $this->requestUri = $this->getRequestUri();
        $this->requestMethod = $this->getRequestMethod();
        $this->requestHeaders ??= $this->getRequestHeaders();

        //Find the first matching route. Only one route will ever be executed.
        $route = $this->findRoute($this->requestUri, $this->requestMethod);

        //If route was found, run it. Otherwise return a 404 response.
        if($route) {
            $response = $this->handleRoute($route);
        } else {
            $response = $this->handleNotFoundResponse();
        }

        //Send response.
        if (!is_a($response, Response::class)) {
            $response = new Response((string) $response);
        }
        $response->send();

        //If the request was a HEAD request, empty the output buffer.
        if ($_SERVER['REQUEST_METHOD'] == 'HEAD') {
            ob_end_clean();
        }
    }

    public function buildCache()
    {
        
    }

    /**
     * Define the current relative URI.
     *
     * @return string
     */
    protected function getRequestUri(): string
    {
        $uri = rawurldecode($_SERVER['REQUEST_URI']);

        // Don't take query params into account on the URL
        if (strstr($uri, '?')) {
            $uri = substr($uri, 0, strpos($uri, '?'));
        }

        // Remove trailing slash + enforce a slash at the start
        return '/' . trim($uri, '/');
    }

    /**
     * Get all request headers.
     *
     * @return array The request headers
     */
    protected function getRequestHeaders(): array
    {
        if(!empty($this->requestHeaders)) return $this->requestHeaders;

        $headers = [];

        // If getallheaders() is available, use that
        if (function_exists('getallheaders')) {
            $headers = getallheaders();

            // getallheaders() can return false if something went wrong
            if ($headers !== false) {
                $this->requestHeaders = $headers;
                return $headers;
            }
        }

        // Method getallheaders() not available or went wrong: manually extract them
        foreach ($_SERVER as $name => $value) {
            if ((substr($name, 0, 5) == 'HTTP_') || ($name == 'CONTENT_TYPE') || ($name == 'CONTENT_LENGTH')) {
                $headers[str_replace([' ', 'Http'], ['-', 'HTTP'], ucwords(strtolower(str_replace('_', ' ', substr($name, 5)))))] = $value;
            }
        }

        $this->requestHeaders = $headers;
        return $headers;
    }

    /**
     * Get the request method used, taking overrides into account.
     *
     * @return string The request method to handle
     */
    protected function getRequestMethod(): string
    {
        // Take the method as found in $_SERVER
        $method = $_SERVER['REQUEST_METHOD'];

        // If it's a HEAD request override it to being GET and prevent any output, as per HTTP Specification
        // @url http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.4
        if ($_SERVER['REQUEST_METHOD'] == 'HEAD') {
            ob_start();
            $method = 'GET';
        }

        // If it's a POST request, check for a method override header
        elseif ($_SERVER['REQUEST_METHOD'] == 'POST') {
            $headers = $this->getRequestHeaders();
            if (isset($headers['X-HTTP-Method-Override']) && in_array($headers['X-HTTP-Method-Override'], array('PUT', 'DELETE', 'PATCH'))) {
                $method = $headers['X-HTTP-Method-Override'];
            }
        }

        return $method;
    }

    protected function loadFromCache(string $cachePath): bool
    {
        if(!file_exists($cachePath) || !file_exists($cachePath . DIRECTORY_SEPARATOR . 'route-cache.php')) {
            return false;
        }

        $this->routes = require $cachePath . DIRECTORY_SEPARATOR . 'route-cache.php';
        return true;
    }

    protected function loadFromRouteFile(string $routePath): void
    {
        if(!file_exists($routePath) || !file_exists($routePath . DIRECTORY_SEPARATOR . 'routes.php')) {
            throw new \RuntimeException('Unable to initialize routes: route file not found.');
        }

        $repository = new Repository();
        $routes = require $routePath . DIRECTORY_SEPARATOR . 'routes.php';

        if(!is_callable($routes)) {
            throw new \RuntimeException('Unable to initialize routes: route file does not contain callable function.');
        }

        //Initialize routes
        call_user_func($routes, $repository);
        $this->routes = $repository->getRoutes();
    }

    protected function findRoute(string $path, string $method): ?Route
    {
        $method = strtoupper($method);

        if(key_exists($method, $this->routes)) {
            foreach($this->routes[$method] as $route) {
                if($route->match($path, $method)) {
                    return $route;
                }
            }
        }

        return null;
    }

    protected function handleRoute(Route $route)
    {
        //Todo: run route middleware and route handler.

        return $route->run();
    }

    protected function handleNotFoundResponse()
    {
        //Do we have an error template?
        $template = $this->app->getViewPath('errors/404.html');
        if(file_exists($template)) {
            ob_start();
            require $template;
            $response = ob_get_clean();

            return new Response($response, 404);
        } else {
            return new Response('Whoops! Could not find that file.', 404);
        }
    }
}