/**
 * Active disk latency probe (embedded, no external ioping binary).
 * Enable: PEARDATA_IOPING=1
 * Path: PEARDATA_IOPING_PATH=/tmp/.peardata-ioping
 */
import fs from 'fs'
import path from 'path'
import os from 'os'
import { CollectorPlugin } from './plugin.js'
import { registerChart } from '../../../shared/metrics.js'

export function isIopingEnabled() {
  const v = process.env.PEARDATA_IOPING
  return v === '1' || v === 'on' || v === 'true'
}

function probePath() {
  return (
    process.env.PEARDATA_IOPING_PATH ||
    path.join(os.tmpdir(), '.peardata-ioping')
  )
}

export class IopingCollector extends CollectorPlugin {
  constructor() {
    super({ name: 'ioping' })
  }

  isEnabled() {
    return isIopingEnabled()
  }

  async collect() {
    const ts = Date.now()
    const p = probePath()
    const buf = Buffer.alloc(4096, 0x5a)
    let latency = 0
    try {
      const t0 = process.hrtime.bigint()
      fs.writeFileSync(p, buf)
      fs.readFileSync(p)
      const t1 = process.hrtime.bigint()
      latency = Number(t1 - t0) / 1e6
      try {
        fs.unlinkSync(p)
      } catch {
        // ignore
      }
    } catch {
      latency = -1
    }
    registerChart({
      id: 'disk.ioping',
      name: 'disk.ioping',
      context: 'disk.ioping',
      title: 'Disk probe latency',
      units: 'milliseconds',
      family: 'ioping',
      chartType: 'line',
      priority: 2100,
      plugin: 'ioping',
      dimensions: [{ id: 'latency', name: 'latency', algorithm: 'absolute' }],
    })
    return [
      {
        chart: 'disk.ioping',
        context: 'disk.ioping',
        ts,
        values: { latency: latency < 0 ? 0 : latency },
      },
    ]
  }
}

let singleton = null
export function getIopingCollector() {
  if (!singleton) singleton = new IopingCollector()
  return singleton
}