const axios = require('axios')
const _ = require('lodash')

// Constants
// TODO: Automatically retrieve dates via aviable Data from database and get rid of "random" dates
const rangeStartDate = '2019-01' // If no date is given, this date will be used as startDate
const rangeEndDate = '2020-05'// If no date is given, this date will be used as endDate

// TODO: call method periodically, not over API (fine for prototyping, tho)
module.exports = async (dbConn, startDate = rangeStartDate, endDate = rangeEndDate) => {
  console.log('update climate with:', startDate, endDate);

  const result = await dbConn.query(`SELECT * FROM regions WHERE meteostat_id IS NOT NULL`)

  const climateObject = await Promise.all(result.map(src => {
    return createClimateObjectFrom(src, startDate, endDate)
  }))
  const climateObjectArr = climateObject.reduce((total, element) => total.concat(element), [])

  await writeToDatabase(dbConn, climateObjectArr)

  const res = `region_climate update complete. see backend logs for info.`
  return res
}

async function createClimateObjectFrom(src, startDate, endDate) {
  let res
  if (src.meteostat_id === '') {
    console.log("skipping: no meteostat id ")
    return []
  }
  try {
    res = await axios.get(`https://api.meteostat.net/v1/history/monthly?station=${src.meteostat_id}&start=${startDate}&end=${endDate}&key=${process.env.METEOSTAT_API_KEY}`)
  } catch (error) {
    console.log("error while getting data from meteostat: couldn't find results for following region: ")
    console.log(src.region + " with meteostat_id " + src.meteostat_id)
    console.log(error)
    return []
  }
  if (!res.data.data) {
    console.log("skipping: no data for station with meteostat_id " + src.meteostat_id + " (" + src.region + ")")
    return []
  }
  const retVal = res.data.data.map(element => {
    let result = {
      region: src.region,
      region_id: src.id,
      year: element.month.split("-")[0],
      month: element.month.split("-")[1],
      temperature_mean: element.temperature_mean,
      temperature_mean_min: element.temperature_mean_min,
      temperature_mean_max: element.temperature_mean_max,
      precipitation: element.precipitation,
      rain_days: element.raindays,
      sun_hours: element.sunshine,
      humidity: element.humidity ? element.humidity : null
    }
    return result
  })
  return retVal
}

async function writeToDatabase(dbConn, climateObjArr) {
  for (const element of climateObjArr) {
    try {
      await dbConn.query(`
      INSERT INTO region_climate 
      (region_id, year, month, temperature_mean, temperature_mean_min, temperature_mean_max, precipitation, sun_hours, humidity, rain_days)
      VALUES (${element.region_id}, ${element.year}, ${element.month}, ${element.temperature_mean}, ${element.temperature_mean_min}, ${element.temperature_mean_max}, ${element.precipitation}, ${element.sun_hours}, ${element.humidity}, ${element.rain_days})
      ON DUPLICATE KEY UPDATE
      temperature_mean = ${element.temperature_mean}, 
      temperature_mean_min = ${element.temperature_mean_min}, 
      temperature_mean_max = ${element.temperature_mean_max}, 
      precipitation = ${element.precipitation}, 
      sun_hours = ${element.sun_hours}, 
      humidity = ${element.humidity}, 
      rain_days = ${element.rain_days};`)
    } catch (error) {
      if (error.code !== 'ER_DUP_ENTRY') {
        console.log("element which causes problems: ")
        console.log(element)
        console.log("query which causes problems: ")
        console.log(error)
      } else {
        console.log(element.region + ": " + error.sqlMessage)
      }
    }
  }
};