<?php
/// CRIMSON --- A simple PHP framework.
/// Copyright © 2024 Freya Murphy <contact@freyacat.org>
///
/// This file is part of CRIMSON.
///
/// CRIMSON is free software; you can redistribute it and/or modify it
/// under the terms of the GNU General Public License as published by
/// the Free Software Foundation; either version 3 of the License, or (at
/// your option) any later version.
///
/// CRIMSON is distributed in the hope that it will be useful, but
/// WITHOUT ANY WARRANTY; without even the implied warranty of
/// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
/// GNU General Public License for more details.
///
/// You should have received a copy of the GNU General Public License
/// along with CRIMSON. If not, see <http://www.gnu.org/licenses/>.

class Router extends Base {

	// if the website is ready to accept requests
	// (protects against users requesting unready resources)
	private bool $ready;
	// if the router is currently in an error handler
	private bool $in_err;
	// The parsed request. Contains the following fields.
	//
	// NAME   | TYPE   | DEFAULT | DESCRIPTION
	// ------------------------------------------------------------
	// app     | string | 'index' | The first part of the uri, selects which
	//         |        |         | controller will be called.
	// slug    | string | 'index' | The second part of the uri, slects
	//         |        |         | which method will be called.
	// args    | array  | []      | Rest of uri parts. Arguments passed to
	//         |        |         | the method.
	// uri     | array? |         | From PHP's parse_url($uri_str).
	// uri_str | string |         | The URI given in the HTML request.
	// method  | string |         | The HTTP method.
	// ip      | string |         | The requesting IP.
	public final array $req;

	/**
	 * Creates the crimson router.
	 *
	 * => Checks if crimson is ready to route requests.
	 * => Defines self as ROUTER.
	 */
	function __construct()
	{
		// are we ready?
		$this->ready = $this->ready_check();
		// get request
		$this->in_err = FALSE;
		$this->req = $this->get_req();
		// ROUTER is used by Controller in error($code) function
		define('ROUTER', $this);
		// fail if URI is invalid (get_req does not check this)
		if (!$this->req['uri'])
			$this->handle_error(400); // does not return!
	}

	/**
	 * Cheks if crimson is ready to route requests.
	 * => Checks if the database is ready (if enabled).
	 */
	private function ready_check(): bool {
	       	// assume we are ready unless told otherwise
		$ready = TRUE;
		// check db
		if ($ready && getenv('POSTGRES_ENABLED') === 'true') {
			$ready = file_exists('/var/run/crimson/db_ready');
		}
		// return result
		return $ready;
	}

	/**
	 * @param string $path - the current request path
	 * Gets the current route
	 * @return array<string,mixed>
	 */
	private function get_req_route($path): array
	{
		// trim the path
		$path = trim($path);
		// remove first '/'
		$path = substr($path, 1);

		// get modified route
		$routes = CONFIG['routes'];
		foreach ($routes as $key => $value) {
			$key = "/^{$key}$/";
			if (!preg_match($key, $path, $matches))
				continue;

			$path = $value;

			for ($i = 1; $i < count($matches); $i++) {
				$path = str_replace(
					"\\{$i}",
					$matches[$i],
					$path);
			}

			break;
		}

		// get path parts
		$parts = explode('/', $path);
		if ($path == '')
			$parts = [];
		// get the length
		$len = count($parts);
		// get route info
		$route = array();
		$route['app']  = $len > 0 ? $parts[0] : 'index';
		$route['slug'] = $len > 1 ? $parts[1] : 'index';
		$route['args'] = array_slice($parts, 2);

		return $route;
	}

	/**
	 * Gets the users ip
	 */
	private function get_ip(): ?string
	{
		$headers = array (
			'HTTP_CLIENT_IP',
			'HTTP_X_FORWARDED_FOR',
			'HTTP_X_FORWARDED',
			'HTTP_FORWARDED_FOR',
			'HTTP_FORWARDED',
			'HTTP_X_REAL_IP',
			'REMOTE_ADDR'
		);
		foreach ($headers as $header) {
			if (isset($_SERVER[$header]))
				return $_SERVER[$header];
		}
		return NULL;
	}

	/**
	 * Gets the curret request info.
	 * Does not fail in invalid uri. Must be handeled by
	 * caller function.
	 * @return array<string,mixed>
 	 */
	private function get_req(): array
	{
		$method = $_SERVER['REQUEST_METHOD'];
		$uri_str = $_SERVER['REQUEST_URI'];
		$uri = parse_url($uri_str);

		$path = '';
		if ($uri && array_key_exists('path', $uri))
			$path = $uri['path'];

		return array_merge(
			array(
				'uri' => $uri,
				'uri_str' => $uri_str,
				'method' => $method,
				'ip' => $this->get_ip()
			),
			$this->get_req_route($path),
		);
	}

	/**
	 * Handles a router error code
	 * @param int $code - the http error code
	 */
	public function handle_error(int $code): never
	{
		// if in_err is set RIGHT NOW, this means the user specified
		// error hook errored itself. To prevent error recursion we do
		// not want to run it again!
		$force_builtin = $this->in_err;
		// Sets the in_err catch to true, read comment above to why.
		$this->in_err = TRUE;
		CRIMSON_HOOK('error', [$this->req, $code], $force_builtin);
		// error hook is type never, but CRIMSON_HOOK is type void
		CRIMSON_DIE();
	}

	/**
	 * @param array $req
	 * @param array<int,mixed> $req
	 */
	public function handle_req(): never
	{
		// block requests if we are not ready
		if ($this->ready === FALSE)
			$this->handle_error(503);

		// run pre route hook
		CRIMSON_HOOK('pre_route', [$this]);

		// load the controller
		$controller = $this->load_controller($this->req['app']);
		if (!$controller)
			$this->handle_error(404);

		// find the function that matches our request
		// format: /controller/fn_name/fn_arg1/fn_arg2/.../fn_argN
		$handler = NULL;
		try {
			$cls = new ReflectionClass($controller);
			$mds = $cls->getMethods(ReflectionMethod::IS_PUBLIC);
			foreach ($mds as $md) {
				if ($md->name !== $this->req['slug'])
					continue;
				if (count($md->getParameters()) !=
					count($this->req['args']))
					continue;
				$handler = $md;
				break;
			}
		} catch (Exception $_e) {}

		// return 404 if no handler found
		if (!$handler)
			$this->handle_error(404);

		try {
			$handler->invokeArgs($controller, $this->req['args']);
		} catch (Exception $_e) {};

		// sanity check
		CRIMSON_DIE();
	}

}