Challenge 3 — Solution

Task: Extend the Router class to support route parameters, e.g.
registering "/posts/{id}" and matching a real URL like "/posts/42" by
extracting 42 and passing it as an argument to the controller method.
Use a regular expression (Intermediate Chapter 9) to implement the
matching.

<?php
    namespace App;

    class Router {
        private array $routes = [];

        public function get(string $path, array $handler) {
            $this->routes[$path] = $handler;
        }

        public function dispatch(string $uri) {
            foreach ($this->routes as $path => $handler) {
                $pattern = $this->convertToRegex($path);

                if (preg_match($pattern, $uri, $matches)) {
                    array_shift($matches); // remove the full match at index 0, keep only captured params

                    [$controllerClass, $method] = $handler;
                    $controller = new $controllerClass();
                    $controller->$method(...$matches);
                    return;
                }
            }

            http_response_code(404);
            echo "404 Not Found";
        }

        private function convertToRegex(string $path): string {
            // Replace {id}, {slug}, etc. with a capturing group matching
            // one or more non-slash characters
            $pattern = preg_replace('/\{[a-zA-Z_]+\}/', '([^/]+)', $path);
            return '#^' . $pattern . '$#';
        }
    }

    // Usage:
    // $router->get('/posts/{id}', [PostController::class, 'show']);
    // A request to "/posts/42" now calls PostController->show('42')
?>


Output (conceptual — demonstrating the matching logic in isolation):
Registered route "/posts/{id}" converts to regex "#^/posts/([^/]+)$#"
Matching "/posts/42" against it captures "42" into $matches[1]
After array_shift(), $matches becomes ["42"]
$controller->show(...["42"]) calls show('42') — the id is now available inside the controller method

Notes:
- convertToRegex() uses preg_replace() (Intermediate Chapter 9) to turn
  any {paramName} placeholder into a capturing group ([^/]+), which
  matches any run of characters that isn't a forward slash - so a
  route like "/posts/{id}" correctly matches "/posts/42" but not
  "/posts/42/edit" (which would need its own separate route).
- array_shift($matches) removes preg_match()'s own index 0 (the whole
  matched string), leaving only the actual captured parameter values -
  exactly the distinction Intermediate Chapter 9's own capturing-groups
  section explained between $matches[0] and $matches[1] onward.
- ...$matches (the splat operator, also used in Challenge 2 of Chapter
  2) unpacks the captured values as individual arguments to the
  controller method - so a route with two parameters, like
  "/posts/{id}/comments/{commentId}", would correctly call the method
  with two separate arguments in order.
- The original exact-match dispatch() (a simple isset() lookup) had to
  be replaced with a foreach loop trying each registered route's own
  regex pattern in turn, since parameterized routes can no longer be
  matched with a single direct array-key lookup.