/**
 * NATS monitoring endpoint collector.
 * Enable: PEARDATA_NATS=1
 * URL: PEARDATA_NATS_URL=http://127.0.0.1:8222
 */
import { CollectorPlugin } from './plugin.js'
import { registerChart } from '../../../shared/metrics.js'

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

function base() {
  return (process.env.PEARDATA_NATS_URL || 'http://127.0.0.1:8222').replace(/\/$/, '')
}

export class NatsCollector extends CollectorPlugin {
  constructor() {
    super({ name: 'nats' })
  }

  isEnabled() {
    return isNatsEnabled()
  }

  async collect() {
    const ts = Date.now()
    registerChart({
      id: 'nats.up',
      name: 'nats.up',
      context: 'nats.up',
      title: 'NATS up',
      units: 'boolean',
      family: 'nats',
      chartType: 'line',
      priority: 8850,
      plugin: 'nats',
      dimensions: [{ id: 'up', name: 'up', algorithm: 'absolute' }],
    })
    try {
      const res = await fetch(`${base()}/varz`, { signal: AbortSignal.timeout(2000) })
      if (!res.ok) throw new Error(String(res.status))
      const j = await res.json()
      registerChart({
        id: 'nats.connections',
        name: 'nats.connections',
        context: 'nats.connections',
        title: 'NATS connections',
        units: 'connections',
        family: 'nats',
        chartType: 'line',
        priority: 8860,
        plugin: 'nats',
        dimensions: [
          { id: 'connections', name: 'connections', algorithm: 'absolute' },
          { id: 'routes', name: 'routes', algorithm: 'absolute' },
          { id: 'remotes', name: 'remotes', algorithm: 'absolute' },
        ],
      })
      registerChart({
        id: 'nats.messages',
        name: 'nats.messages',
        context: 'nats.messages',
        title: 'NATS messages',
        units: 'messages',
        family: 'nats',
        chartType: 'line',
        priority: 8870,
        plugin: 'nats',
        dimensions: [
          { id: 'in_msgs', name: 'in_msgs', algorithm: 'absolute' },
          { id: 'out_msgs', name: 'out_msgs', algorithm: 'absolute' },
        ],
      })
      return [
        { chart: 'nats.up', context: 'nats.up', ts, values: { up: 1 } },
        {
          chart: 'nats.connections',
          context: 'nats.connections',
          ts,
          values: {
            connections: j.connections || 0,
            routes: j.routes || 0,
            remotes: j.remotes || 0,
          },
        },
        {
          chart: 'nats.messages',
          context: 'nats.messages',
          ts,
          values: { in_msgs: j.in_msgs || 0, out_msgs: j.out_msgs || 0 },
        },
      ]
    } catch {
      return [{ chart: 'nats.up', context: 'nats.up', ts, values: { up: 0 } }]
    }
  }
}

let singleton = null
export function getNatsCollector() {
  if (!singleton) singleton = new NatsCollector()
  return singleton
}