package db

import cats.data.NonEmptyList
import cats.effect._
import cats.implicits._
import doobie._
import doobie.implicits._

import java.time.format.DateTimeFormatter
import java.time.{LocalDate, LocalDateTime, OffsetDateTime}
import doobie.postgres.implicits._
import org.typelevel.log4cats.Logger
import org.typelevel.log4cats.slf4j.Slf4jLogger
import parse.Aggregate.{AggregateKey, AggregateValue, DoubleValue, TimeDoubleList, UserQuery}
import parse.{Parser, WeatherStationData}

import java.time.temporal.ChronoUnit
import scala.util.matching.Regex

object PostgresService {
  def of(transactor: Transactor[IO]): IO[PostgresService] = {
    Slf4jLogger.create[IO].map(logger => new PostgresService(transactor, logger))
  }
}

class PostgresService(transactor: Transactor[IO], log: Logger[IO]) {
  def save(fileName: String, content: String): IO[String] = {
    val YearPattern: Regex = """(\d{4})\d{4}_\d{4}\.csv""".r

    def extractYear(filename: String): Option[String] = {
      YearPattern.findFirstMatchIn(filename).map(_.group(1))
    }

    extractYear(fileName) match {
      case Some(year) =>
        val strLines = content.split(System.lineSeparator()).toList
        val weatherStationData = strLines.flatMap(line => Parser.parseLine(line, year))
        insertInWeatherTable(weatherStationData)
          .attempt
          .flatMap {
            case Left(error) => log.error(s"Write db '$fileName' failed with error: ${error.getMessage}") *> IO.raiseError(error)
            case Right(rowCount) => log.info(s"write rows: $rowCount file: $fileName in year: $year").as(fileName)
          }

      case None =>
        IO.raiseError(new RuntimeException(s"Could not extract year from file name: $fileName"))
    }
  }

  def queryCountry(from: LocalDateTime, to: LocalDateTime, fieldList: NonEmptyList[String]): IO[Map[String, (Option[Double], Option[Double], Option[Double], Option[Double])]] = {
    def queryForField(field: String, from: LocalDateTime, to: LocalDateTime): ConnectionIO[(String, (Option[Double], Option[Double], Option[Double], Option[Double]))] =
    {
      val query =
        fr"SELECT " ++
          fr" ROUND(CAST(MIN(" ++ Fragment.const(field) ++ fr") AS NUMERIC), 1), " ++
          fr" ROUND(CAST(MAX(" ++ Fragment.const(field) ++ fr") AS NUMERIC), 1), " ++
          fr" ROUND(CAST(AVG(" ++ Fragment.const(field) ++ fr") AS NUMERIC), 1), " ++
          fr" ROUND(CAST(SUM(" ++ Fragment.const(field) ++ fr") AS NUMERIC), 1)" ++
          fr" FROM weather" ++
          fr" WHERE dateTime BETWEEN $from AND $to"

      query.query[(Option[Double], Option[Double], Option[Double], Option[Double])]
        .unique
        .map { case (min, max, avg, sum) =>
          field -> (min, max, avg, sum)
        }
    }

    fieldList.toList.traverse { field =>
      queryForField(field, from, to).transact(transactor)
    }.map(_.toMap)
  }

  def query(userQuery: UserQuery):  IO[Map[String, Option[AggregateValue]]] = {
    if (userQuery.field == "phenomena") { // this handles strings
      // TODO query list and distinct values from phenomena
      IO(Map()) // empty result
    } else if (List(
      AggregateKey.Max,
      AggregateKey.Min,
      AggregateKey.Avg,
      AggregateKey.Sum,
      AggregateKey.Distinct
    ).contains(userQuery.key)) {
      val query =
        fr"SELECT city, ROUND(CAST(" ++ Fragment.const(userQuery.key.toString.toUpperCase) ++ fr"(" ++ Fragment.const(userQuery.field) ++ fr") AS NUMERIC), 1) AS value" ++
          fr" FROM weather" ++
          fr" WHERE " ++ Fragments.in(fr"city", userQuery.cities) ++
          fr" AND dateTime BETWEEN ${userQuery.from} AND ${userQuery.to}" ++
          fr" GROUP BY city"

      query.query[(String, Option[Double])]
        .to[List]
        .transact(transactor)
        .map { resultList =>
          resultList.map {
            case (city, maybeValue) =>
              city -> maybeValue.map(DoubleValue)
          }.toMap: Map[String, Option[AggregateValue]]
        }
    } else if (userQuery.key == AggregateKey.List) {
      val byField = userQuery.field match {
        case "tempMax" => "MAX(tempMax)"
        case "tempMin" => "MIN(tempMin)"
        case "tempAvg" => "AVG(tempAvg)"
        case "precipitation" => "SUM(precipitation)"
        case "windAvg" => "AVG(windAvg)"
        case "windMax" => "MAX(windMax)"
        case "visibilityMin" => "MIN(visibilityMin)"
        case "visibilityAvg" => "AVG(visibilityAvg)"
        case "snowAvg" => "AVG(snowAvg)"
        case "atmPressure" => "AVG(atmPressure)"
        case "dewPoint" => "AVG(dewPoint)"
        case "humidity" => "AVG(humidity)"
        case "sunDuration" => "SUM(sunDuration)"
      }

      val selectField = if(userQuery.granularity == ChronoUnit.HOURS) userQuery.field else byField;
      val selectTime = userQuery.granularity match {
        case ChronoUnit.HOURS => "dateTime"
        case ChronoUnit.DAYS => "DATE(dateTime)"
        case ChronoUnit.MONTHS => "TO_CHAR(DATE_TRUNC('month', dateTime), 'YYYY-MM')"
        case ChronoUnit.YEARS => "TO_CHAR(DATE_TRUNC('year', dateTime), 'YYYY')"
        case _ => ""
      }
      val groupBy = if(userQuery.granularity == ChronoUnit.HOURS) "" else "GROUP BY city, " + selectTime;

      val query =
        fr"SELECT city, " ++ Fragment.const(selectTime) ++ fr" as time, ROUND(CAST(" ++ Fragment.const(selectField) ++ fr" AS NUMERIC), 1) as value" ++
        fr" FROM weather" ++
        fr" WHERE " ++ Fragments.in(fr"city", userQuery.cities) ++
        fr" AND dateTime BETWEEN ${userQuery.from} AND ${userQuery.to}" ++
        fr" " ++  Fragment.const(groupBy) ++
        fr" ORDER BY city, time;"


      /*
      SELECT city, dateTime, tempmax
      FROM weather
      WHERE city IN ('Rīga', 'Rēzekne', 'Kolka')
      AND dateTime BETWEEN '2023-12-10' AND '2023-12-14'
      ORDER BY city, dateTime;

      SELECT city, DATE(dateTime) as day, MAX(tempmax) as max_temp
      FROM weather
      WHERE city IN ('Rīga', 'Rēzekne', 'Kolka')
      AND dateTime BETWEEN '2023-12-10' AND '2023-12-14'
      GROUP BY city, DATE(dateTime)
      ORDER BY city, day;

      SELECT city, TO_CHAR(DATE_TRUNC('month', dateTime), 'YYYY-MM') as month, MAX(tempmax) as max_temp
      FROM weather
      WHERE city IN ('Rīga', 'Rēzekne', 'Kolka')
      AND dateTime BETWEEN '2023-01-01' AND '2023-12-31'
      GROUP BY city, TO_CHAR(DATE_TRUNC('month', dateTime), 'YYYY-MM')
      ORDER BY city, month;

      SELECT city, TO_CHAR(DATE_TRUNC('year', dateTime), 'YYYY') as year, MAX(tempmax) as max_temp
      FROM weather
      WHERE city IN ('Rīga', 'Rēzekne', 'Kolka')
      AND dateTime BETWEEN '2023-01-01' AND '2023-12-31'
      GROUP BY city, TO_CHAR(DATE_TRUNC('year', dateTime), 'YYYY')
      ORDER BY city, year;
       */

      query.query[(String, String, Option[Double])]
        .to[List]
        .transact(transactor)
        .map { resultList =>
          resultList
            .groupBy(_._1)
            .view.mapValues { list =>
            TimeDoubleList(list.map { case (_, date, maybeValue) =>
              (date, maybeValue)
            }).some
          }
            .toMap: Map[String, Option[AggregateValue]]
        }

    } else {
      IO(Map()) // empty result
    }
  }

  def getDatesByMonths(monthList: List[LocalDate]): IO[List[LocalDate]] = {
    val monthYearPairs = monthList.map { localDate =>
      val month = localDate.atStartOfDay.getMonthValue
      val year = localDate.atStartOfDay.getYear
      (month, year)
    }

    val whereClauses = monthYearPairs.map {
      case (month, year) => fr"(EXTRACT(MONTH FROM dateTime) = $month AND EXTRACT(YEAR FROM dateTime) = $year)"
    }

    val combinedWhereClause = whereClauses.intercalate(fr" OR ")

    (
      fr"""
        SELECT DISTINCT DATE(dateTime)
        FROM weather
        WHERE """ ++ combinedWhereClause
    )
      .query[LocalDate]
      .to[List]
      .transact(transactor)
  }

  def getDateTimeEntries(dateTime: LocalDateTime): IO[List[String]] = {
    val columnNames = List("City; TempMax; TempMin; TempAvg; Precipitation; WindAvg; WindMax; VisibilityMin; VisibilityAvg; SnowAvg; AtmPressure; DewPoint; Humidity; SunDuration; Phenomena")
    val result = fr"""
        SELECT city || ';' || COALESCE(tempmax::text, '' ) || ';' || COALESCE(tempmin::text, '' ) || ';' || COALESCE(tempavg::text, '' ) || ';' || COALESCE(precipitation::text, '' ) || ';' || COALESCE(windavg::text, '' ) || ';' || COALESCE(windmax::text, '' ) || ';' || COALESCE(tempmax::text, '' ) || ';' || COALESCE(visibilitymin::text, '' ) || ';' || COALESCE(visibilityavg::text, '' ) || ';' || COALESCE(snowavg::text, '' ) || ';' || COALESCE(atmpressure::text, '' ) || ';' || COALESCE(dewpoint::text, '' ) || ';' || COALESCE(humidity::text, '' ) || ';' || COALESCE(sunduration::text, '' )  || ';' || array_to_string(phenomena, ', ')
        FROM weather
        WHERE dateTime = $dateTime
        ORDER BY city
      """
        .query[String]
        .to[List]
        .transact(transactor)

    result.map(columnNames ++ _)
  }

  def getDateFileNames(date: LocalDate): IO[List[String]] = {
    val year = date.atStartOfDay.getYear
    val month = date.atStartOfDay.getMonthValue
    val day = date.atStartOfDay.getDayOfMonth
    val whereClauses = fr"(EXTRACT(DAY FROM dateTime) = $day AND EXTRACT(MONTH FROM dateTime) = $month AND EXTRACT(YEAR FROM dateTime) = $year)"
    val formatter = DateTimeFormatter.ofPattern("yyyyMMdd_HH00")

    (
      fr"""
          SELECT DISTINCT dateTime
          FROM weather
          WHERE """ ++ whereClauses ++
        fr"ORDER BY dateTime"
    )
      .query[OffsetDateTime]
      .to[List]
      .transact(transactor)
      .map { dateTimes =>
        dateTimes.map(dateTime =>
          dateTime.format(formatter)
        )
      }
  }

  def getResourceContent(path: String): IO[String] = {
    val streamResource = Resource.make(IO(getClass.getResourceAsStream(path))) { stream =>
      IO(stream.close()).handleErrorWith(_ => IO.unit)
    }

    streamResource.use { stream =>
      IO(scala.io.Source.fromInputStream(stream).mkString)
    }
  }

  def createWeatherTable: IO[Int] = {
    for {
      createTableSql <- getResourceContent("/db/create_weather_table.sql")
      result <- Update0(createTableSql, None).run.transact(transactor)
    } yield result
  }

  implicit val doubleOptionMeta: Meta[Option[Double]] = Meta[Double].imap(Option(_))(_.getOrElse(Double.NaN))

  def insertInWeatherTable(data: List[WeatherStationData]): IO[Int] = {
      getResourceContent("/db/insert_weather_table.sql").flatMap { insertTableSql =>
        val insertData = data.map(line => {
          val w = line.weather
          (line.timestamp, line.city, w.tempMax, w.tempMin, w.tempAvg, w.precipitation, w.windAvg, w.windMax, w.visibilityMin, w.visibilityAvg, w.snowAvg, w.atmPressure, w.dewPoint, w.humidity, w.sunDuration, w.phenomena)
        })

        Update[(LocalDateTime, String, Option[Double], Option[Double], Option[Double], Option[Double], Option[Double], Option[Double], Option[Double], Option[Double], Option[Double], Option[Double], Option[Double], Option[Double], Option[Double], List[String])](insertTableSql)
          .updateMany(insertData)
          .transact(transactor)
      }
  }
}