import Router from "@koa/router";
import Koa from "koa";

type Constructor<T = {}> = new (...args: any[]) => T;

type Route = {
    method: string;
    path: string;
    fn: any;
};

const routeSymbol = Symbol("routeSymbol");

export function get(path: string) {
    return function getDecorator (originalMethod: any, context: ClassMethodDecoratorContext) {
        if (context.metadata) {
            if (!context.metadata[routeSymbol]) {
                context.metadata[routeSymbol] = [] as Route[];
            }
            context.metadata[routeSymbol].push({method: 'get', path, fn: originalMethod});
        }
        return originalMethod;
    }
}

export function post(path: string) {
    return function getDecorator (originalMethod: any, context: ClassMethodDecoratorContext) {
        if (context.metadata) {
            if (!context.metadata[routeSymbol]) {
                context.metadata[routeSymbol] = [] as Route;
            }
            context.metadata[routeSymbol].push({method: 'post', path, fn: originalMethod});
        }
        return originalMethod;
    }
}

export function middleware(fn: any, path: string = '') {
    return function middlewareDecorator (constructor: any, context: ClassDecoratorContext) {
        if (context.metadata) {
            if (!context.metadata[routeSymbol]) {
                context.metadata[routeSymbol] = [];
            }
            context.metadata[routeSymbol].unshift({method: 'use', path, fn});
        }
        return constructor;
    }
}

export function router(prefix: string) {
    return function routerDecorator<T extends Constructor>(constructor: T, context: ClassDecoratorContext<T>) {
        return class KoaRouter extends constructor {
            public router: Router;
            constructor(...args: any[]) {
                super(...args);
                this.router = new Router({prefix});
                for (const route of context.metadata?.[routeSymbol] || [] satisfies Route[]) switch (route.method) {
                    case "get": this.router.get(route.path, route.fn); break;
                    case "post": this.router.post(route.path, route.fn); break;
                    case 'use': this.router.use(route.fn); break;
                }
            }

            public injectInto(app: Koa) {
                app.use(this.router.routes()).use(this.router.allowedMethods());
            }
        }
    }
}