const fetch = require('node-fetch')

function AWDrone (options) {
  if (!(this instanceof AWDrone))
    return new AWDrone(options)
  
  options = options || {}
  if (!options.express)
    throw new Error('Express not provided to AWDrone');
  if (!options.config)
    throw new Error('Configuration not provided to AWDrone');

  const express = options.express
  const router = express.Router()
  const config = options.config
  const db = options.db
    
  router.get('/', function (req, res) {
    update(db).then( () => {
      res.sendStatus(200)
    }).catch( (err) => {
      res.sendStatus(500)
    })
  })
  
  function refresh () {
    setTimeout(refresh, 60 * 60 * 12)
    update(db)
  }
  
  setTimeout(refresh, 60)

  this._router = router
}

function update (db) {
  return new Promise( (resolve, reject) => {
    const type = 'drone'
    const id = 'drone-statistics'
    db.get(type).get(id).then( data => {
      scrape().then( matches => {
        if (matches.length !== 4) {
          throw new Error('problem retrieving matches')
        }
      
        data.strikes = matches[0]
        data.totalKilled = matches[1]
        data.civiliansKilled = matches[2]
        data.childrenKilled = matches[3]
      
        const resource = db.get(type, id)
        resource.update(id, data).then(function(updated) {
          resolve()
        }).fail( err => { throw err })
      })
      .catch( err => {
        reject(err)
      })
    })    
  })
}

function scrape (cb) {
  return fetch('https://www.thebureauinvestigates.com/projects/drone-war')
  .then(response => {
    return response.text()
  })
  .then(body => {
    const statRegexp = new RegExp('stat__figure">([-0-9,]+)<', 'g')
    const matches = getMatches(body, statRegexp)
    return matches
  })
  .catch( err => {
    return []
  })
}

function getMatches(string, regex, index) {
  index = index || 1
  let matches = []
  let match
  while (match = regex.exec(string)) {
    matches.push(match[index])
  }
  return matches
}

AWDrone.prototype.middleware = function () {
  return this._router
}

module.exports = AWDrone