/**
 * Apache mod_status collector (service plugin).
 *
 * Enable: PEARDATA_APACHE=1
 * URL:    PEARDATA_APACHE_URL=http://127.0.0.1/server-status?auto
 *
 * Charts: apache.workers, apache.accesses, apache.traffic
 */
import http from 'http'
import https from 'https'
import { CollectorPlugin } from './plugin.js'
import { registerChart } from '../../../shared/metrics.js'
import logger from '../../utils/logger.js'

const log = logger.child('apache')

const CHART_WORKERS = {
  id: 'apache.workers',
  name: 'apache.workers',
  context: 'apache.workers',
  title: 'Apache workers',
  units: 'workers',
  family: 'apache',
  chartType: 'line',
  priority: 8400,
  plugin: 'apache',
  dimensions: [
    { id: 'BusyWorkers', name: 'BusyWorkers', algorithm: 'absolute' },
    { id: 'IdleWorkers', name: 'IdleWorkers', algorithm: 'absolute' },
  ],
}

const CHART_ACCESSES = {
  id: 'apache.accesses',
  name: 'apache.accesses',
  context: 'apache.accesses',
  title: 'Apache total accesses',
  units: 'accesses/s',
  family: 'apache',
  chartType: 'line',
  priority: 8410,
  plugin: 'apache',
  dimensions: [{ id: 'Total_Accesses', name: 'Total Accesses', algorithm: 'absolute' }],
}

const CHART_TRAFFIC = {
  id: 'apache.traffic',
  name: 'apache.traffic',
  context: 'apache.traffic',
  title: 'Apache traffic',
  units: 'KiB/s',
  family: 'apache',
  chartType: 'line',
  priority: 8420,
  plugin: 'apache',
  dimensions: [{ id: 'Total_kBytes', name: 'Total kBytes', algorithm: 'absolute' }],
}

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

/**
 * Parse Apache server-status?auto body.
 * @param {string} body
 * @returns {{ BusyWorkers: number, IdleWorkers: number, TotalAccesses: number, TotalKBytes: number }|null}
 */
export function parseApacheServerStatus(body) {
  const text = String(body || '')
  const busy = text.match(/BusyWorkers:\s*(\d+)/i)
  const idle = text.match(/IdleWorkers:\s*(\d+)/i)
  const accesses = text.match(/Total Accesses:\s*(\d+)/i)
  const kbytes = text.match(/Total kBytes:\s*(\d+)/i)
  if (!busy || !idle) return null
  return {
    BusyWorkers: Number(busy[1]),
    IdleWorkers: Number(idle[1]),
    TotalAccesses: accesses ? Number(accesses[1]) : 0,
    TotalKBytes: kbytes ? Number(kbytes[1]) : 0,
  }
}

function fetchText(url, timeoutMs = 3000) {
  return new Promise((resolve, reject) => {
    const mod = String(url).startsWith('https') ? https : http
    const req = mod.get(url, (res) => {
      let body = ''
      res.on('data', (c) => {
        body += c
      })
      res.on('end', () => {
        if (res.statusCode && res.statusCode >= 400) {
          reject(new Error(`HTTP ${res.statusCode}`))
          return
        }
        resolve(body)
      })
    })
    req.setTimeout(timeoutMs, () => {
      req.destroy()
      reject(new Error('timeout'))
    })
    req.on('error', reject)
  })
}

export class ApacheCollector extends CollectorPlugin {
  constructor(opts = {}) {
    super({ name: 'apache', intervalMs: opts.intervalMs })
    this.url =
      opts.url || process.env.PEARDATA_APACHE_URL || 'http://127.0.0.1/server-status?auto'
    /** @type {{ accesses: number, kbytes: number, wallMs: number }|null} */
    this._prev = null
  }

  isEnabled() {
    return isApacheEnabled()
  }

  start() {
    if (!this.isEnabled()) return
    registerChart(CHART_WORKERS)
    registerChart(CHART_ACCESSES)
    registerChart(CHART_TRAFFIC)
    log.info('Apache collector started', { url: this.url })
    super.start()
  }

  async collect() {
    const body = await fetchText(this.url)
    const parsed = parseApacheServerStatus(body)
    if (!parsed) throw new Error('unrecognized server-status body')
    const ts = Date.now()

    let accessRate = 0
    let trafficRate = 0
    if (this._prev && ts > this._prev.wallMs) {
      const dt = (ts - this._prev.wallMs) / 1000
      if (dt > 0) {
        accessRate = Math.max(0, (parsed.TotalAccesses - this._prev.accesses) / dt)
        trafficRate = Math.max(0, (parsed.TotalKBytes - this._prev.kbytes) / dt)
      }
    }
    this._prev = {
      accesses: parsed.TotalAccesses,
      kbytes: parsed.TotalKBytes,
      wallMs: ts,
    }

    return [
      {
        chart: 'apache.workers',
        context: 'apache.workers',
        ts,
        values: {
          BusyWorkers: parsed.BusyWorkers,
          IdleWorkers: parsed.IdleWorkers,
        },
      },
      {
        chart: 'apache.accesses',
        context: 'apache.accesses',
        ts,
        values: { Total_Accesses: accessRate },
      },
      {
        chart: 'apache.traffic',
        context: 'apache.traffic',
        ts,
        values: { Total_kBytes: trafficRate },
      },
    ]
  }
}

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

export function getApacheCollector() {
  if (!singleton) singleton = new ApacheCollector()
  return singleton
}