import cron from "node-cron";
import {Nullable} from "../types/Nullable";
import {Class, ClassNamed} from "../types/Class";  

export type EventConfiguration = {
  name: string, 
  maxExecutions?: number,
}

export interface TimedEvent {
  configuration: EventConfiguration,
  cronExpression: string,
  execute: () => void
}

export class EventHandler {
  private eventHandlers: Map<string, CallableFunction[]> = new Map();
  
  constructor() {
  }
  
  public addHandler<T extends Class>(eventName: string, handler: (event: T) => void) {
    if (!this.eventHandlers.has(eventName)) {
      this.eventHandlers.set(eventName, []);
    }
    
    this.eventHandlers.get(eventName)?.push(handler);
  }
  
  public dispatch<T extends Class>(event: T) {
    const eventName = event.constructor.name;
    if (!this.eventHandlers.has(eventName)) {
      return;
    }
    
    this.eventHandlers.get(eventName)?.forEach((handler) => {
      handler(event);
    })
  }
  
  public addTimed(event: TimedEvent) {
    if (!cron.validate(event.cronExpression)) {
      throw new Error(`Can't create event with name '${event.configuration.name}': Invalid cron expression.`)
    }
    
    cron.schedule(event.cronExpression, event.execute.bind(event), event.configuration);
  }
}