refactor router to improve route registration and handler management

src/router.ts

@@ -5,7 +5,7 @@ import Tpl from "./template.js";
 import { Request, Response, Handler } from "./types.js";
 
 export default class Router {
-  private routes: Map<RegExp | string, { [key: string]: Handler | Handler[] }>;
+  private routes: Map<RegExp | string, { [key: string]: Handler[] }>;
   private tpl?: Tpl;
   private mimes: Map<string, string>;
 
@@ -42,7 +42,7 @@ export default class Router {
    */
   group(basePath: string | RegExp, callback: (methods: any) => void): this {
     const self = this;
-  
+
     const methods = {
       get(path: string | RegExp, ...handlers: Handler[]) {
         const fullPath = self.combinePaths(basePath, path);
@@ -67,10 +67,10 @@ export default class Router {
     };
   
     callback(methods);
-  
+
     return this;
   }
-  
+
   /**
    * Combines a base path and a sub path into a single path.
    * @param basePath - The base path or RegExp.
@@ -86,7 +86,7 @@ export default class Router {
       return new RegExp(`${basePath.replace(/\/$/, "")}${subPath.source}`);
     if(basePath instanceof RegExp && subPath instanceof RegExp)
       return new RegExp(`${basePath.source}${subPath.source}`);
-  
+
     throw new TypeError("Invalid path types. Both basePath and subPath must be either string or RegExp.");
   }
 
@@ -179,14 +179,13 @@ export default class Router {
   private registerRoute(
     path: string | RegExp,
     method: string,
-    handlers: Handler[]
+    handler: Handler[]
   ): this {
-    if(!this.routes.has(path)) {
-      this.routes.set(path, {});
-    }
-  
-    this.routes.get(path)![method] = handlers.flat();
-  
+    const route: { [key: string]: Handler[] } = this.routes.get(path) ?? {
+      [ method ]: handler
+    };
+    this.routes.set(path, route);
+
     console.log("route set:", method.toUpperCase(), path);
     this.sortRoutes();
     return this;
@@ -199,10 +198,12 @@ export default class Router {
    * @returns The matching route or undefined.
    */
   getRoute(path: string, method: string): any {
-    method = method.toLowerCase();
-    return [...this.routes.entries()].find(r => {
-      return (typeof r[0] === "string" ? r[0] === path : r[0].exec?.(path)) && r[1][method];
-    });
+    return [...this.routes.entries()]
+      .find(r => typeof r[0] === "string"
+        ? r[0] === path
+        : r[0].exec?.(path)
+       && r[1][method.toLowerCase()]
+    );
   }
 
   /**