/**
 * Hardware sensors via sysfs hwmon + thermal zones.
 *
 * Enable: PEARDATA_SENSORS=1 (default on Linux when unset)
 * Disable: PEARDATA_SENSORS=0
 */
import fs from 'fs'
import path from 'path'
import os from 'os'
import { EventEmitter } from 'events'
import {
  SAMPLE_INTERVAL_MS,
  registerChart,
  makeSensorTempChart,
  makeThermalZoneChart,
} from '../../../shared/metrics.js'
import logger from '../../utils/logger.js'

const log = logger.child('sensors')

export function isSensorsEnabled() {
  const v = process.env.PEARDATA_SENSORS
  if (v === '0' || v === 'off' || v === 'false') return false
  if (v === '1' || v === 'on' || v === 'true') return true
  return os.platform() === 'linux'
}

function readFile(p) {
  try {
    return fs.readFileSync(p, 'utf8')
  } catch {
    return null
  }
}

function makeSensorFanChart(chip, label) {
  const id = `${chip}_${label}`.replace(/[^a-zA-Z0-9_.-]/g, '_').slice(0, 64)
  return {
    id: `sensors.fan.${id}`,
    name: `sensors.fan.${id}`,
    context: 'sensors.fan',
    title: `Fan ${chip} ${label}`,
    units: 'RPM',
    family: chip,
    chartType: 'line',
    priority: 7040,
    plugin: 'sensors',
    dimensions: [{ id: 'rpm', name: 'rpm', algorithm: 'absolute' }],
  }
}

function makeSensorVoltageChart(chip, label) {
  const id = `${chip}_${label}`.replace(/[^a-zA-Z0-9_.-]/g, '_').slice(0, 64)
  return {
    id: `sensors.voltage.${id}`,
    name: `sensors.voltage.${id}`,
    context: 'sensors.voltage',
    title: `Voltage ${chip} ${label}`,
    units: 'mV',
    family: chip,
    chartType: 'line',
    priority: 7050,
    plugin: 'sensors',
    dimensions: [{ id: 'millivolts', name: 'millivolts', algorithm: 'absolute' }],
  }
}

function makeSensorPowerChart(chip, label) {
  const id = `${chip}_${label}`.replace(/[^a-zA-Z0-9_.-]/g, '_').slice(0, 64)
  return {
    id: `sensors.power.${id}`,
    name: `sensors.power.${id}`,
    context: 'sensors.power',
    title: `Power ${chip} ${label}`,
    units: 'microWatts',
    family: chip,
    chartType: 'line',
    priority: 7060,
    plugin: 'sensors',
    dimensions: [{ id: 'microwatts', name: 'microwatts', algorithm: 'absolute' }],
  }
}

/**
 * @returns {Array<{ chartId: string, context: string, values: Record<string, number> }>}
 */
export function sampleSensors() {
  /** @type {Array<{ chartId: string, context: string, values: Record<string, number> }>} */
  const out = []
  const hwmonRoot = '/sys/class/hwmon'
  try {
    const chips = fs.readdirSync(hwmonRoot)
    for (const chip of chips) {
      const dir = path.join(hwmonRoot, chip)
      const name = (readFile(path.join(dir, 'name')) || chip).trim()
      let ents
      try {
        ents = fs.readdirSync(dir)
      } catch {
        continue
      }
      for (const ent of ents) {
        const m = ent.match(/^temp(\d+)_input$/)
        if (!m) continue
        const n = m[1]
        const raw = readFile(path.join(dir, ent))
        if (raw == null) continue
        const milli = Number(raw.trim())
        if (!Number.isFinite(milli)) continue
        const label =
          (readFile(path.join(dir, `temp${n}_label`)) || `temp${n}`).trim() || `temp${n}`
        const def = makeSensorTempChart(name, label)
        registerChart(def)
        out.push({
          chartId: def.id,
          context: def.context,
          values: { temperature: milli / 1000 },
        })
      }
      const fan = ent.match(/^fan(\d+)_input$/)
      if (fan) {
        const n = fan[1]
        const raw = readFile(path.join(dir, ent))
        if (raw == null) continue
        const rpm = Number(raw.trim())
        if (!Number.isFinite(rpm)) continue
        const label =
          (readFile(path.join(dir, `fan${n}_label`)) || `fan${n}`).trim() || `fan${n}`
        const def = makeSensorFanChart(name, label)
        registerChart(def)
        out.push({ chartId: def.id, context: def.context, values: { rpm } })
      }
      const vin = ent.match(/^in(\d+)_input$/)
      if (vin) {
        const n = vin[1]
        const raw = readFile(path.join(dir, ent))
        if (raw == null) continue
        const mv = Number(raw.trim())
        if (!Number.isFinite(mv)) continue
        const label =
          (readFile(path.join(dir, `in${n}_label`)) || `in${n}`).trim() || `in${n}`
        const def = makeSensorVoltageChart(name, label)
        registerChart(def)
        out.push({ chartId: def.id, context: def.context, values: { millivolts: mv } })
      }
      const pwr = ent.match(/^power(\d+)_input$/)
      if (pwr) {
        const n = pwr[1]
        const raw = readFile(path.join(dir, ent))
        if (raw == null) continue
        const uw = Number(raw.trim())
        if (!Number.isFinite(uw)) continue
        const label =
          (readFile(path.join(dir, `power${n}_label`)) || `power${n}`).trim() || `power${n}`
        const def = makeSensorPowerChart(name, label)
        registerChart(def)
        out.push({ chartId: def.id, context: def.context, values: { microwatts: uw } })
      }
    }
  } catch {
    // no hwmon
  }

  const thermalRoot = '/sys/class/thermal'
  try {
    for (const zone of fs.readdirSync(thermalRoot)) {
      if (!zone.startsWith('thermal_zone')) continue
      const dir = path.join(thermalRoot, zone)
      const type = (readFile(path.join(dir, 'type')) || zone).trim()
      const raw = readFile(path.join(dir, 'temp'))
      if (raw == null) continue
      const milli = Number(raw.trim())
      if (!Number.isFinite(milli) || milli === 0) continue
      // some platforms report already in C
      const celsius = milli > 1000 ? milli / 1000 : milli
      const def = makeThermalZoneChart(zone, type)
      registerChart(def)
      out.push({ chartId: def.id, context: def.context, values: { temperature: celsius } })
    }
  } catch {
    // no thermal
  }
  return out
}

export class SensorsCollector extends EventEmitter {
  constructor(opts = {}) {
    super()
    this.intervalMs =
      opts.intervalMs ?? (Number(process.env.PEARDATA_SAMPLE_MS) || SAMPLE_INTERVAL_MS)
    this.timer = null
    this.running = false
  }

  start() {
    if (this.running) return
    this.running = true
    this._tick()
    this.timer = setInterval(() => this._tick(), this.intervalMs)
    if (this.timer.unref) this.timer.unref()
    log.info('Sensors collector started')
  }

  stop() {
    this.running = false
    if (this.timer) clearInterval(this.timer)
    this.timer = null
  }

  _tick() {
    const ts = Date.now()
    const samples = sampleSensors()
    if (!samples.length) return
    const batch = samples.map((s) => ({
      chart: s.chartId,
      context: s.context,
      ts,
      values: s.values,
    }))
    this.emit('samples', batch)
  }
}

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

export function getSensorsCollector() {
  if (!singleton) singleton = new SensorsCollector()
  return singleton
}