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 = '2019-01-01' // If no date is given, this date will be used as startDate
const rangeEndDate = '2019-12-31'// 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 id, region, lon, lat FROM regions`)

    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 v2 complete. see backend logs for info.`
    return climateObjectArr
}

async function createClimateObjectFrom(src, startDate, endDate) {
    let res
    try {
        res = await axios.get(
            `https://api.meteostat.net/v2/point/daily?lat=${src.lat}&lon=${src.lon}&start=${startDate}&end=${endDate}`,
            {
                headers: {
                    "x-api-key": process.env.METEOSTAT_API_KEY_V2
                }//,
                //httpsAgent: agent
            })
    } catch (error) {
        console.log("error while getting data from meteostat: couldn't find results for following region: ")
        console.log(src.region,"with coords:",src.lon,src.lat)
        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.date.split("-")[0],
            month: element.date.split("-")[1],
            day: element.date.split("-")[2],
            temperature_mean: element.tavg,
            temperature_mean_min: element.tmin,
            temperature_mean_max: element.tmax,
            precipitation: element.prcp,
            rain_days: element.prcp > 2 ? 1:0, // More than 2mm => rainday
            sun_hours: element.tsun/60
        }
        //console.log(result)
        return result
    })
    return retVal
}

async function writeToDatabase(dbConn, climateObjArr) {
    for (const element of climateObjArr) {
        //console.log(element)
        try {
            await dbConn.query(`
      INSERT INTO region_climate_day
      (region_id, year, month, day, temperature_mean, temperature_mean_min, temperature_mean_max, precipitation, sun_hours, rain_days)
      VALUES (${element.region_id}, ${element.year}, ${element.month}, ${element.day}, ${element.temperature_mean}, ${element.temperature_mean_min}, ${element.temperature_mean_max}, ${element.precipitation}, ${element.sun_hours}, ${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}, 
      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)
            }
        }
    }
};

/*
INSERT INTO region_climate
(region_id, YEAR, MONTH, temperature_mean, temperature_mean_min, temperature_mean_max, precipitation, rain_days, sun_hours)
SELECT
region_id,
YEAR,
MONTH,
ROUND(AVG(temperature_mean),2) AS temperature_mean,
MIN(temperature_mean_min) AS temperature_mean_min,
MAX(temperature_mean_max) AS temperature_mean_max,
ROUND(SUM(precipitation),2) AS precipitation,
SUM(rain_days) AS rain_days,
SUM(sun_hours) AS sun_hours
FROM region_climate_day
GROUP BY region_id, YEAR, month
 */