import { log } from '../helpers/log.js'
import type { TopicHandler } from '../types.js'

const EDGE = 'demo'
const REGISTER_COUNT = 125
const DEMO_CLOUD_INGEST_URL = process.env.DEMO_CLOUD_INGEST_URL as string

type DemoModbusMetric = {
  edge: string
  timestamp: string
  tag: string
  value: number
}

function parseValues(payload: Buffer): number[] {
  const values = JSON.parse(payload.toString('utf8')) as number[]
  assertRegisterCount(values)
  return values
}

function assertRegisterCount(values: number[]): void {
  if (values.length !== REGISTER_COUNT) {
    throw new Error(`Expected ${REGISTER_COUNT} modbus values, got ${values.length}`)
  }
}

function toMetrics(values: number[], timestamp: string): DemoModbusMetric[] {
  return values.map((value, index) => ({
    edge: EDGE,
    timestamp,
    tag: `register-${index}`,
    value,
  }))
}

async function postMetrics(metrics: DemoModbusMetric[]): Promise<void> {
  for (const metric of metrics) {
    const response = await fetch(DEMO_CLOUD_INGEST_URL, {
      method: 'POST',
      headers: {
        'content-type': 'application/json',
        'x-api-key': process.env.CLOUD_INGEST_API_KEY as string,
      },
      body: JSON.stringify(metric),
    })

    if (!response.ok) {
      const text = await response.text()
      throw new Error(text)
    }
  }

  log(`${EDGE}.modbus.posted ${metrics.length} metrics`)
}

export const handleDemoModbus: TopicHandler = async (topic, payload) => {
  log(`${EDGE}.modbus.received ${topic} ${payload.length} bytes`)

  const values = parseValues(payload)
  const metrics = toMetrics(values, new Date().toISOString())
  await postMetrics(metrics)
}