import cron, {validate} from "node-cron";
import {Class} from "../types/Class";
import {randomUUID} from "node:crypto";

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

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

export class EventHandler {
  private eventHandlers: Map<string, Map<string, CallableFunction>> = new Map();

  constructor() {
  }

  public addHandler<T extends Class>(eventName: string, handler: (event: T) => void): string {
    if (!this.eventHandlers.has(eventName)) {
      this.eventHandlers.set(eventName, new Map());
    }

    const id = randomUUID();
    this.eventHandlers.get(eventName)?.set(id, handler);
    return id;
  }
  
  public removeHandler(eventName: string, id: string) {
    if (!this.eventHandlers.has(eventName)) {
      return;
    }
    
    const localEventHandlers = this.eventHandlers.get(eventName);
    if (!localEventHandlers || !localEventHandlers.has(id)) {
      return;
    }
    
    localEventHandlers.delete(id);
  }

  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);
  }
}