/**
 * SMART disk health collector via smartctl.
 *
 * Enable: PEARDATA_SMART=1
 *
 * Charts: smart.temp.{dev}, smart.reallocated.{dev}
 */
import { execFile } from 'child_process'
import { promisify } from 'util'
import { CollectorPlugin } from './plugin.js'
import { registerChart } from '../../../shared/metrics.js'
import logger from '../../utils/logger.js'

const log = logger.child('smart')
const execFileAsync = promisify(execFile)

const DEVICE_TIMEOUT_MS = 2000

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

/**
 * @param {string} dev
 */
function sanitizeDev(dev) {
  return String(dev)
    .replace(/[^a-zA-Z0-9_.-]/g, '_')
    .replace(/^_+|_+$/g, '')
    .slice(0, 64)
}

/**
 * @param {string} dev
 * @param {'temp'|'reallocated'} kind
 */
function makeSmartChart(dev, kind) {
  const safe = sanitizeDev(dev)
  const id = kind === 'temp' ? `smart.temp.${safe}` : `smart.reallocated.${safe}`
  return {
    id,
    name: id,
    context: kind === 'temp' ? 'smart.temperature' : 'smart.reallocated',
    title: kind === 'temp' ? `SMART temperature ${dev}` : `SMART reallocated ${dev}`,
    units: kind === 'temp' ? 'Celsius' : 'sectors',
    family: safe,
    chartType: 'line',
    priority: kind === 'temp' ? 7100 : 7110,
    plugin: 'smart',
    dimensions: [{ id: 'value', name: 'value', algorithm: 'absolute' }],
  }
}

/**
 * @param {number} timeoutMs
 * @returns {Promise<string[]|null>}
 */
export async function scanSmartDevices(timeoutMs = DEVICE_TIMEOUT_MS) {
  try {
    const { stdout } = await execFileAsync('smartctl', ['--scan'], {
      timeout: timeoutMs,
      encoding: 'utf8',
    })
    /** @type {string[]} */
    const devs = []
    for (const line of String(stdout || '').split('\n')) {
      const parts = line.trim().split(/\s+/)
      if (parts[0] && !parts[0].startsWith('#')) devs.push(parts[0])
    }
    return devs.length ? devs : null
  } catch {
    return null
  }
}

/**
 * @param {string} dev
 * @returns {Promise<{ temp: number|null, reallocated: number|null }|null>}
 */
export async function readSmartAttributes(dev) {
  try {
    const { stdout } = await execFileAsync('smartctl', ['-A', '-j', dev], {
      timeout: DEVICE_TIMEOUT_MS,
      encoding: 'utf8',
    })
    const json = JSON.parse(stdout)
    const attrs = json?.ata_smart_attributes?.table || json?.table || []
    let temp = null
    let reallocated = null
    for (const a of attrs) {
      const id = a.id ?? a.attr_id
      const val = a.raw?.value ?? a.raw_value ?? a.value
      if (id === 194 || a.name === 'Temperature_Celsius') temp = Number(val)
      if (id === 5 || a.name === 'Reallocated_Sector_Ct') reallocated = Number(val)
    }
    if (temp == null && json?.temperature?.current != null) temp = Number(json.temperature.current)
    return { temp: Number.isFinite(temp) ? temp : null, reallocated: Number.isFinite(reallocated) ? reallocated : null }
  } catch {
    try {
      const { stdout } = await execFileAsync('smartctl', ['-A', dev], {
        timeout: DEVICE_TIMEOUT_MS,
        encoding: 'utf8',
      })
      let temp = null
      let reallocated = null
      for (const line of String(stdout || '').split('\n')) {
        const m = line.match(/^\s*(\d+)\s+(\S+)\s+\S+\s+\S+\s+\S+\s+\S+\s+\S+\s+(\d+)/)
        if (!m) continue
        const id = Number(m[1])
        const val = Number(m[3])
        if (id === 194) temp = val
        if (id === 5) reallocated = val
      }
      return {
        temp: Number.isFinite(temp) ? temp : null,
        reallocated: Number.isFinite(reallocated) ? reallocated : null,
      }
    } catch {
      return null
    }
  }
}

export class SmartCollector extends CollectorPlugin {
  constructor(opts = {}) {
    super({ name: 'smart', intervalMs: opts.intervalMs })
    /** @type {string[]|null} */
    this.devices = null
  }

  isEnabled() {
    return isSmartEnabled()
  }

  start() {
    if (!this.isEnabled()) return
    log.info('SMART collector started')
    super.start()
  }

  async collect() {
    if (this.devices === null) {
      this.devices = (await scanSmartDevices()) || []
      if (!this.devices.length) {
        log.info('smartctl unavailable or no devices — collector idle')
        return []
      }
    }
    const ts = Date.now()
    /** @type {Array<{ chart: string, context: string, ts: number, values: Record<string, number|null> }>} */
    const batch = []
    for (const dev of this.devices) {
      const attrs = await readSmartAttributes(dev)
      if (!attrs) continue
      if (attrs.temp != null) {
        const def = makeSmartChart(dev, 'temp')
        registerChart(def)
        batch.push({
          chart: def.id,
          context: def.context,
          ts,
          values: { value: attrs.temp },
        })
      }
      if (attrs.reallocated != null) {
        const def = makeSmartChart(dev, 'reallocated')
        registerChart(def)
        batch.push({
          chart: def.id,
          context: def.context,
          ts,
          values: { value: attrs.reallocated },
        })
      }
    }
    return batch
  }
}

/** @type {SmartCollector|null} */
let singleton = null

export function getSmartCollector() {
  if (!singleton) singleton = new SmartCollector()
  return singleton
}