/**
 * Enum for game-wide event types.
 */
export enum Events {
  DAMAGE_DEALT = 'combat:damage_dealt',
  ENTITY_DIED = 'combat:entity_died',
  EVOLVED = 'evolution:evolved',
  MUTATION_GAINED = 'evolution:mutation_gained',
  EXP_GAINED = 'stats:exp_gained',
  LEVEL_UP = 'stats:level_up',
  SKILL_LEARNED = 'skills:learned',
  ATTACK_PERFORMED = 'combat:attack_performed',
  SKILL_COOLDOWN_STARTED = 'skills:cooldown_started',
}

/**
 * Event data types
 */
export interface DamageDealtEvent {
  x: number;
  y: number;
  value: number;
  color: string;
}

export interface MutationGainedEvent {
  name: string;
  description?: string;
}

export interface SkillLearnedEvent {
  id: string;
}

export interface EntityDiedEvent {
  entity: unknown;
}

export interface AttackPerformedEvent {
  entity: unknown;
  angle: number;
}

type EventCallback = (data?: unknown) => void;

/**
 * Lightweight EventBus for pub/sub communication between systems.
 */
export class EventBus {
  private listeners: Map<string, EventCallback[]>;

  constructor() {
    this.listeners = new Map();
  }

  /**
   * Subscribe to an event with a callback.
   * @param event - The event name from the Events enum
   * @param callback - The function to call when the event is emitted
   * @returns An unsubscribe function
   */
  on(event: string, callback: EventCallback): () => void {
    if (!this.listeners.has(event)) {
      this.listeners.set(event, []);
    }
    const callbacks = this.listeners.get(event);
    if (callbacks) {
      callbacks.push(callback);
    }
    return () => this.off(event, callback);
  }

  /**
   * Unsubscribe a specific callback from an event.
   * @param event - The event name
   * @param callback - The original callback function to remove
   */
  off(event: string, callback: EventCallback): void {
    if (!this.listeners.has(event)) return;
    const callbacks = this.listeners.get(event);
    if (callbacks) {
      const index = callbacks.indexOf(callback);
      if (index > -1) {
        callbacks.splice(index, 1);
      }
    }
  }

  /**
   * Emit an event to all subscribers.
   * @param event - The event name
   * @param data - Data to pass to the callbacks
   */
  emit(event: string, data?: unknown): void {
    if (!this.listeners.has(event)) return;
    const callbacks = this.listeners.get(event);
    if (callbacks) {
      callbacks.forEach((callback) => callback(data));
    }
  }
}