<?php

/**
 * Add a route to the route tree. The route must be a URI path, and contain dynamic segments
 * using a colon prefix. (:id, :slug, etc)
 *
 * Example:
 * `router_add($routes, 'GET', '/posts/:id', function($id) { echo "Viewing post $id"; });`
 */
function router_add(array &$routes, string $method, string $route, callable $handler): void
{
	// Expand the route into segments and make dynamic segments into a common placeholder
	$segments = array_map(function($segment) {
		return str_starts_with($segment, ':') ? ':x' : $segment;
	}, explode('/', trim($route, '/')));

	// Push each segment into the routes array as a node, except if this is the root node
	$node = &$routes;
	foreach ($segments as $segment) {
		// skip an empty segment, which allows us to register handlers for the root node
		if ($segment === '') continue;
		$node = &$node[$segment]; // build the node tree as we go
	}

	// Add the handler to the last node
	$node[$method] = $handler;
}

/**
 * Perform a lookup in the route tree for a given method and URI. Returns an array with a result code,
 * a handler if found, and any dynamic parameters. Codes are 200 for success, 404 for not found, and
 * 405 for method not allowed.
 *
 * @return array ['code', 'handler', 'params']
 */
function router_lookup(array $routes, string $method, string $uri): array
{
	// node is a reference to our current location in the node tree
	$node = $routes;

	// params will hold any dynamic segments we find
	$params = [];

	// if the URI is just a slash, we can return the handler for the root node
	if ($uri === '/') {
		return isset($node[$method])
			? ['code' => 200, 'handler' => $node[$method], 'params' => null]
			: ['code' => 405, 'handler' => null, 'params' => null];
	}

	// We'll split up the URI into segments and traverse the node tree
	foreach (explode('/', trim($uri, '/')) as $segment) {
		// if there is a node for this segment, move to it
		if (isset($node[$segment])) {
			$node = $node[$segment];
			continue;
		}

		// if there is a dynamic segment, move to it and store the value
		if (isset($node[':x'])) {
			$params[] = $segment;
			$node = $node[':x'];
			continue;
		}

		// if we can't find a node for this segment, return 404
		return ['code' => 404, 'handler' => null, 'params' => []];
	}

	// if we found a handler for the method, return it and any params. if not, return a 405
	return isset($node[$method])
		? ['code' => 200, 'handler' => $node[$method], 'params' => $params ?? []]
		: ['code' => 405, 'handler' => null, 'params' => []];
}

/**
 * Register a GET route
 */
function router_get(array &$routes, string $route, callable $handler): void
{
	router_add($routes, 'GET', $route, $handler);
}

/**
 * Register a POST route
 */
function router_post(array &$routes, string $route, callable $handler): void
{
	router_add($routes, 'POST', $route, $handler);
}

/**
 * Register a PUT route
 */
function router_put(array &$routes, string $route, callable $handler): void
{
	router_add($routes, 'PUT', $route, $handler);
}

/**
 * Register a DELETE route
 */
function router_delete(array &$routes, string $route, callable $handler): void
{
	router_add($routes, 'DELETE', $route, $handler);
}

/**
 * Register a PATCH route
 */
function router_patch(array &$routes, string $route, callable $handler): void
{
	router_add($routes, 'PATCH', $route, $handler);
}

/**
 * Handle a router error by setting the response code and echoing an error message
 */
function router_error(int $code): void
{
	http_response_code($code);
	echo match ($code) {
		403 => 'Forbidden',
		404 => 'Not Found',
		405 => 'Method Not Allowed',
		418 => 'I\'m a teapot',
		default => 'Unknown Error',
	};
	exit;
}