/* eslint-disable no-console */
const os = require('os')
const ExpressCompression = require('compression')
const promClient = require('prom-client')
const promWrapper = require('./prom_wrapper')
const tracing = require('./tracing')

const DEFAULT_APP_NAME = 'unknown'

const { collectDefaultMetrics } = promWrapper
const destructors = []

require('./uv_threadpool_size')

/**
 * Configure the metrics module
 */
function configure(opts = {}) {
  const appName = opts.appName || DEFAULT_APP_NAME
  const hostname = os.hostname()
  promClient.register.setDefaultLabels({ app: appName, host: hostname })
  if (opts.ttlInMinutes) {
    promWrapper.ttlInMinutes = opts.ttlInMinutes
  }
}

let initialized = false

/**
 * Configure the metrics module and start the default metrics collectors and
 * profiling agents.
 */
function initialize(appName, opts = {}) {
  if (initialized) {
    return
  }
  appName = appName || DEFAULT_APP_NAME
  if (tracing.tracingEnabled()) {
    tracing.initialize(appName)
  }
  configure({ ...opts, appName })
  collectDefaultMetrics({ timeout: 5000, prefix: '' })
  promWrapper.setupSweeping()

  console.log(`ENABLE_TRACE_AGENT set to ${process.env.ENABLE_TRACE_AGENT}`)
  if (process.env.ENABLE_TRACE_AGENT === 'true') {
    console.log('starting google trace agent')
    const traceAgent = require('@google-cloud/trace-agent')

    const traceOpts = { ignoreUrls: [/^\/status/, /^\/health_check/] }
    traceAgent.start(traceOpts)
  }

  console.log(`ENABLE_DEBUG_AGENT set to ${process.env.ENABLE_DEBUG_AGENT}`)
  if (process.env.ENABLE_DEBUG_AGENT === 'true') {
    console.log('starting google debug agent')
    const debugAgent = require('@google-cloud/debug-agent')
    debugAgent.start({
      allowExpressions: true,
      serviceContext: {
        service: appName,
        version: process.env.BUILD_VERSION,
      },
    })
  }

  console.log(`ENABLE_PROFILE_AGENT set to ${process.env.ENABLE_PROFILE_AGENT}`)
  if (process.env.ENABLE_PROFILE_AGENT === 'true') {
    console.log('starting google profile agent')
    const profiler = require('@google-cloud/profiler')
    profiler.start({
      serviceContext: {
        service: appName,
        version: process.env.BUILD_VERSION,
      },
    })
  }

  inc('process_startup')
  initialized = true
}

function registerDestructor(func) {
  destructors.push(func)
}

function injectMetricsRoute(app) {
  app.get(
    '/metrics',
    ExpressCompression({
      level: parseInt(process.env.METRICS_COMPRESSION_LEVEL || '1', 10),
    }),
    function (req, res, next) {
      res.set('Content-Type', promWrapper.registry.contentType)
      promWrapper.registry
        .metrics()
        .then(metrics => {
          res.end(metrics)
        })
        .catch(err => {
          next(err)
        })
    }
  )
}

function buildPromKey(key) {
  return key.replace(/[^a-zA-Z0-9]/g, '_')
}

function sanitizeValue(value) {
  return parseFloat(value)
}

function set(key, value, sampleRate = 1) {
  console.log('counts are not currently supported')
}

function inc(key, sampleRate = 1, labels = {}) {
  if (arguments.length === 2 && typeof sampleRate === 'object') {
    labels = sampleRate
  }

  key = buildPromKey(key)
  promWrapper.metric('counter', key, labels).inc(labels)
  if (process.env.DEBUG_METRICS) {
    console.log('doing inc', key, labels)
  }
}

function count(key, count, sampleRate = 1, labels = {}) {
  if (arguments.length === 3 && typeof sampleRate === 'object') {
    labels = sampleRate
  }

  key = buildPromKey(key)
  promWrapper.metric('counter', key, labels).inc(labels, count)
  if (process.env.DEBUG_METRICS) {
    console.log('doing count/inc', key, labels)
  }
}

function summary(key, value, labels = {}) {
  key = buildPromKey(key)
  promWrapper.metric('summary', key, labels).observe(labels, value)
  if (process.env.DEBUG_METRICS) {
    console.log('doing summary', key, value, labels)
  }
}

function timing(key, timeSpan, sampleRate = 1, labels = {}) {
  if (arguments.length === 3 && typeof sampleRate === 'object') {
    labels = sampleRate
  }

  key = buildPromKey('timer_' + key)
  promWrapper.metric('summary', key, labels).observe(labels, timeSpan)
  if (process.env.DEBUG_METRICS) {
    console.log('doing timing', key, labels)
  }
}

function histogram(key, value, buckets, labels = {}) {
  key = buildPromKey('histogram_' + key)
  promWrapper.metric('histogram', key, labels, buckets).observe(labels, value)
  if (process.env.DEBUG_METRICS) {
    console.log('doing histogram', key, buckets, labels)
  }
}

class Timer {
  constructor(key, sampleRate = 1, labels = {}, buckets) {
    if (typeof sampleRate === 'object') {
      // called with (key, labels, buckets)
      if (arguments.length === 3) {
        buckets = labels
        labels = sampleRate
      }

      // called with (key, labels)
      if (arguments.length === 2) {
        labels = sampleRate
      }

      sampleRate = 1 // default value to pass to timing function
    }

    this.start = new Date()
    key = buildPromKey(key)
    this.key = key
    this.sampleRate = sampleRate
    this.labels = labels
    this.buckets = buckets
  }

  done() {
    const timeSpan = new Date() - this.start
    if (this.buckets) {
      histogram(this.key, timeSpan, this.buckets, this.labels)
    } else {
      timing(this.key, timeSpan, this.sampleRate, this.labels)
    }
    return timeSpan
  }
}

function gauge(key, value, sampleRate = 1, labels = {}) {
  if (arguments.length === 3 && typeof sampleRate === 'object') {
    labels = sampleRate
  }

  key = buildPromKey(key)
  promWrapper.metric('gauge', key, labels).set(labels, sanitizeValue(value))
  if (process.env.DEBUG_METRICS) {
    console.log('doing gauge', key, labels)
  }
}

function globalGauge(key, value, sampleRate = 1, labels = {}) {
  key = buildPromKey(key)
  labels = { host: 'global', ...labels }
  promWrapper.metric('gauge', key, labels).set(labels, sanitizeValue(value))
}

function close() {
  for (const func of destructors) {
    func()
  }
}

module.exports.configure = configure
module.exports.initialize = initialize
module.exports.registerDestructor = registerDestructor
module.exports.injectMetricsRoute = injectMetricsRoute
module.exports.buildPromKey = buildPromKey
module.exports.sanitizeValue = sanitizeValue
module.exports.set = set
module.exports.inc = inc
module.exports.count = count
module.exports.summary = summary
module.exports.timing = timing
module.exports.histogram = histogram
module.exports.Timer = Timer
module.exports.gauge = gauge
module.exports.globalGauge = globalGauge
module.exports.close = close
module.exports.prom = promClient
module.exports.register = promWrapper.registry

module.exports.http = require('./http')
module.exports.open_sockets = require('./open_sockets')
module.exports.event_loop = require('./event_loop')
module.exports.memory = require('./memory')
module.exports.mongodb = require('./mongodb')
module.exports.timeAsyncMethod = require('./timeAsyncMethod')