proxy.ts

/* In a config object :
{
    "endpoints": {
        "createUser": {
            "path": "/users",
            "method": "POST"
        }
        "listUsers": {
            "path": "/users",
            "method": "GET"
        }
    }
}
*/

interface Api {
    listUsers(): Promise<User[]>;
    createUser(params: { body: Omit<User, "uuid"> }): Promise<void>;
}

class Service {
    private readonly serviceName = "";
    public readonly api: Api;
    
    constructor(
        private readonly config: Config,
        private readonly permissionService: PersmissionService,
        private readonly http: HttpClient,
    ) {
        this.api = this.buildProxy((name, ...args: any[]) => this.request(name, args[0]));
    }
    
    private async request<T>(route: keyof Api, params: { body?: unknown, path?: string }): Promise<T> {
        // use imagination here, completely fake code
        const method = this.config.endpoints[route].method;
        const token = await this.permissionService.getTokenAsync(this.serviceName);
        return this.http.request(this.serviceName, { path, method, payload: { body, token } });
    }

    private buildProxy<T>(action: (route: keyof T, ...args: unknown[})): T {
        return new Proxy(
            {},
            {
                get: (_target, name: string) => (...arg: unknown[]) => action(name as keyof T, ...arg),
            }
        ) as T;
    }
}

const service: Service = buildService();
await service.api.createUser({ /* */ });
const users = await service.api.listUsers();