Router/router.ts

interface RouterContext {
  url: URL;
  params: Record<string, string | undefined>;
  state: Record<string, unknown>;
  pattern: URLPattern;
  request: Request;
}

type Handler = (req: Request, ctx: RouterContext) => Promise<Response> | Response;
type Middleware = (ctx: RouterContext, next: () => Promise<Response>) => Promise<Response>;

interface RouteConfig {
  pattern: URLPattern;
  handlers: { [method: string]: Handler };
}

interface MiddlewareConfig {
  pattern: URLPattern;
  handler: Middleware;
  // Add path for sorting
  path: string;
}

interface RouteConfigurator {
  get(handler: Handler): RouteConfigurator;
  post(handler: Handler): RouteConfigurator;
  put(handler: Handler): RouteConfigurator;
  delete(handler: Handler): RouteConfigurator;
  patch(handler: Handler): RouteConfigurator;
  options(handler: Handler): RouteConfigurator;
}

/**
 * A simple router for Deno
 * 
 * @author Emmaline Autumn
 * 
 * @example
 * ```ts
 * const router = new Router();
 * router.route('/users')
 *   .get((ctx) => {
 *     return new Response('GET /users');
 *   })
 *   .post((ctx) => {
 *     return new Response('POST /users');
 *   });
 *
 * router.route('/users/:id')
 *   .get((ctx) => {
 *     return new Response(`GET /users/${ctx.params.id}`);
 *   })
 *   .put((ctx) => {
 *     return new Response(`PUT /users/${ctx.params.id}`);
 *   })
 *   .delete((ctx) => {
 *     return new Response(`DELETE /users/${ctx.params.id}`);
 *   });
 *
 * router.route('/posts')
 *   .get((ctx) => {
 *     return new Response('GET /posts');
 *   })
 *   .post((ctx) => {
 *     return new Response('POST /posts');
 *   });
 *
 * router.route('/posts/:id')
 *   .get((ctx) => {
 *     return new Response(`GET /posts/${ctx.params.id}`);
 *   })
 *   .put((ctx) => {
 *     return new Response(`PUT /posts/${ctx.params.id}`);
 *   })
 *   .delete((ctx) => {
 *     return new Response(`DELETE /posts/${ctx.params.id}`);
 *   });
 *
 * router.route('/*')
 *   .get((ctx) => {
 *     return new Response('GET /*');
 *   })
 *   .post((ctx) => {
 *     return new Response('POST /*');
 *   });
 *
 * router.use('/users', async (_, next) => {
 *   console.log('Using middleware');
 *   return await next();
 * });
 *
 * Deno.serve({
 *   port: 8000,
 *   handler: router.handle
 * });
 */
export class Router {
  private routes: RouteConfig[] = [];
  private middleware: MiddlewareConfig[] = [];

  route(path: string): RouteConfigurator {
    path = path.startsWith('/') ? path : `/${path}`;
    
    const pattern = new URLPattern({ pathname: path });
    const routeConfig: RouteConfig = {
      pattern,
      handlers: {}
    };
    this.routes.push(routeConfig);

    return {
      get(handler: Handler) {
        routeConfig.handlers['GET'] = handler;
        return this;
      },
      post(handler: Handler) {
        routeConfig.handlers['POST'] = handler;
        return this;
      },
      put(handler: Handler) {
        routeConfig.handlers['PUT'] = handler;
        return this;
      },
      delete(handler: Handler) {
        routeConfig.handlers['DELETE'] = handler;
        return this;
      },
      patch(handler: Handler) {
        routeConfig.handlers['PATCH'] = handler;
        return this;
      },
      options(handler: Handler) {
        routeConfig.handlers['OPTIONS'] = handler;
        return this;
      }
    };
  }

  use(pathOrMiddleware: string | Middleware, middlewareOrRouter?: Middleware | Router): Router {
    // Handle the case where only middleware is provided
    if (typeof pathOrMiddleware === 'function') {
      const pattern = new URLPattern({ pathname: '/*' });
      this.middleware.push({
        pattern,
        handler: pathOrMiddleware,
        path: '/*'
      });
      return this;
    }

    const path = pathOrMiddleware;
    const middleware = middlewareOrRouter;

    if (!middleware) {
      throw new Error('Middleware or Router is required');
    }

    // Normalize the path to handle both exact matches and nested paths
    const normalizedPath = path.startsWith('/') ? path : `/${path}`;
    const isParameterPath = normalizedPath.includes(':');
    const wildcardPath = isParameterPath ? 
      normalizedPath : 
      normalizedPath === '/' ? 
        '/*' : 
        `${normalizedPath.replace(/\/+$/, '')}/*?`;

    if (middleware instanceof Router) {
      // Merge the nested router's routes
      for (const nestedRoute of middleware.routes) {
        const combinedPath = this.combinePaths(path, nestedRoute.pattern.pathname);
        const newPattern = new URLPattern({ pathname: combinedPath });
        
        this.routes.push({
          pattern: newPattern,
          handlers: { ...nestedRoute.handlers }
        });
      }

      // Merge the nested router's middleware
      for (const nestedMiddleware of middleware.middleware) {
        const combinedPath = this.combinePaths(path, nestedMiddleware.path);
        const newPattern = new URLPattern({ pathname: combinedPath });
        
        this.middleware.push({
          pattern: newPattern,
          handler: nestedMiddleware.handler,
          path: combinedPath
        });
      }
    } else {
      // Handle regular middleware
      const pattern = new URLPattern({ pathname: wildcardPath });
      this.middleware.push({
        pattern,
        handler: middleware,
        path: wildcardPath
      });
    }

    return this;
  }

  handle = async (req: Request): Promise<Response> => {
    const url = new URL(req.url);
    const method = req.method;

    // Find the matching route
    const matchedRoute = this.findMatchingRoute(url);
    if (!matchedRoute) {
      return new Response('Not Found', { status: 404 });
    }

    const handler = matchedRoute.config.handlers[method];
    if (!handler) {
      return new Response('Method Not Allowed', { status: 405 });
    }

    // Get matching middleware and sort by path specificity
    const matchingMiddleware = this.getMatchingMiddleware(url);

    // Create the base context object
    const baseCtx: RouterContext = {
      url,
      params: {},
      state: {},
      pattern: matchedRoute.config.pattern,
      request: req
    };

    // Combine route parameters with the base context
    baseCtx.params = {
      ...baseCtx.params,
      ...matchedRoute.params
    };

    // Execute middleware chain
    let index = 0;
    const executeMiddleware = async (): Promise<Response> => {
      if (index < matchingMiddleware.length) {
        const { middleware, params } = matchingMiddleware[index++];
        // Create a new context for each middleware with its specific parameters
        const middlewareCtx: RouterContext = {
          ...baseCtx,
          params: { ...baseCtx.params, ...params },
          pattern: middleware.pattern
        };
        return await middleware.handler(middlewareCtx, executeMiddleware);
      }
      // Final handler gets the accumulated parameters
      return await handler(req, baseCtx);
    };

    try {
      return await executeMiddleware();
    } catch (error) {
      console.error('Error handling request:', error);
      return new Response('Internal Server Error', { status: 500 });
    }
  }

  private findMatchingRoute(url: URL): { config: RouteConfig; params: Record<string, string | undefined> } | null {
    for (const route of this.routes) {
      const result = route.pattern.exec(url);
      if (result) {
        return {
          config: route,
          params: result.pathname.groups
        };
      }
    }
    return null;
  }

  private getMatchingMiddleware(url: URL): Array<{ 
    middleware: MiddlewareConfig; 
    params: Record<string, string> 
  }> {
    const matches = this.middleware
      .map(mw => {
        const result = mw.pattern.exec(url) ?? mw.pattern.exec(url.href + '/');
        // console.log(url, mw.pattern, result);
        if (result) {
          return {
            middleware: mw,
            params: result.pathname.groups
          };
        }
        return null;
      })
      .filter((item): item is { 
        middleware: MiddlewareConfig; 
        params: Record<string, string> 
      } => item !== null);

    // Sort middleware by path specificity
    return matches.sort((a, b) => {
      const pathA = a.middleware.path;
      const pathB = b.middleware.path;

      // Global middleware comes first
      if (pathA === '/*' && pathB !== '/*') return -1;
      if (pathB === '/*' && pathA !== '/*') return 1;

      // More specific paths (with more segments) come later
      const segmentsA = pathA.split('/').length;
      const segmentsB = pathB.split('/').length;
      
      if (segmentsA !== segmentsB) {
        return segmentsA - segmentsB;
      }

      // If same number of segments, longer paths are more specific
      return pathA.length - pathB.length;
    });
  }

  private combinePaths(basePath: string, routePath: string): string {
    const normalizedBase = basePath.replace(/\/+$/, '').replace(/^\/*/, '/');
    const normalizedRoute = routePath.replace(/^\/*/, '');
    return normalizedBase === '/' ? `/${normalizedRoute}` : `${normalizedBase}/${normalizedRoute}`;
  }
}

export default Router;

if (import.meta.main) {
  console.log('Starting server...');
  const router = new Router();
  router.route('/users')
    .get((ctx) => {
      return new Response('GET /users');
    })
    // .post((ctx) => {
    //   return new Response('POST /users');
    // });

  // router.route('/users/:id')
  //   .get((ctx) => {
  //     return new Response(`GET /users/${ctx.params.id}`);
  //   })
  //   .put((ctx) => {
  //     return new Response(`PUT /users/${ctx.params.id}`);
  //   })
  //   .delete((ctx) => {
  //     return new Response(`DELETE /users/${ctx.params.id}`);
  //   });

  // router.route('/posts')
  //   .get((ctx) => {
  //     return new Response('GET /posts');
  //   })
  //   .post((ctx) => {
  //     return new Response('POST /posts');
  //   });

  // router.route('/posts/:id')
  //   .get((ctx) => {
  //     return new Response(`GET /posts/${ctx.params.id}`);
  //   })
  //   .put((ctx) => {
  //     return new Response(`PUT /posts/${ctx.params.id}`);
  //   })
  //   .delete((ctx) => {
  //     return new Response(`DELETE /posts/${ctx.params.id}`);
  //   });

  // router.route('/*')
  //   .get((ctx) => {
  //     return new Response('GET /*');
  //   })
  //   .post((ctx) => {
  //     return new Response('POST /*');
  //   });

  router.use('/users', async (_, next) => {
    console.log('Using middleware');
    return await next();
  });

  Deno.serve({
    port: 8000,
    
    handler: router.handle
  });
}