/**
 * Minimal collector plugin base (Phase 3 / EXTENDING.md).
 *
 * Subclasses implement `collect()` → sample batch, call `start()` to schedule.
 */
import { EventEmitter } from 'events'
import { SAMPLE_INTERVAL_MS } from '../../../shared/metrics.js'

export class CollectorPlugin extends EventEmitter {
  /**
   * @param {{ name: string, intervalMs?: number }} opts
   */
  constructor(opts) {
    super()
    this.name = opts.name || 'plugin'
    this.intervalMs = opts.intervalMs || Number(process.env.PEARDATA_SAMPLE_MS) || SAMPLE_INTERVAL_MS
    this._timer = null
  }

  /** @returns {boolean} */
  isEnabled() {
    return false
  }

  /**
   * @returns {Promise<Array<{ chart: string, context: string, ts: number, values: Record<string, number|null> }>>|Array}
   */
  async collect() {
    return []
  }

  start() {
    if (this._timer || !this.isEnabled()) return
    const tick = async () => {
      try {
        const batch = await this.collect()
        if (batch?.length) this.emit('samples', batch)
      } catch (err) {
        this.emit('error', err)
      }
    }
    tick()
    this._timer = setInterval(tick, this.intervalMs)
    if (typeof this._timer.unref === 'function') this._timer.unref()
  }

  stop() {
    if (this._timer) {
      clearInterval(this._timer)
      this._timer = null
    }
  }
}