Refactor to FileService and PostgresService

src/main/scala/db/PostgresService.scala

@@ -0,0 +1,91 @@
+package db
+
+import cats.data.NonEmptyList
+import cats.effect._
+import doobie._
+import doobie.implicits._
+
+import java.time.format.DateTimeFormatter
+import java.time.{LocalDateTime, ZoneId, ZonedDateTime}
+import doobie.postgres.implicits._
+import org.typelevel.log4cats.Logger
+import org.typelevel.log4cats.slf4j.Slf4jLogger
+
+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 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(): IO[Int] = {
+    val formatter = DateTimeFormatter.ofPattern("yyyyMMdd_HHmm")
+    val dateTime = LocalDateTime.parse("20230516_1500", formatter)
+
+    val rigaZone = ZoneId.of("Europe/Riga")
+    val zonedTime: ZonedDateTime = dateTime.atZone(rigaZone)
+
+    // in pgAdmin run: ```SET TIMEZONE = 'Europe/Riga';```
+
+    for {
+      insertTableSql <- getResourceContent("/db/insert_weather_table.sql")
+      result <- Update[(ZonedDateTime, 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
+      ).run((zonedTime, "Rīga", Some(20.2), Some(8.8), Some(15.6), None, None, None, None, None, None, None, None, None, None, List("hail", "rain"))).transact(transactor)
+    } yield result
+  }
+
+  def selectWeatherTable(): IO[List[(String, Option[Double])]] = {
+    val formatter = DateTimeFormatter.ofPattern("yyyyMMdd_HHmm")
+    val rigaZone = ZoneId.of("Europe/Riga")
+    val from = LocalDateTime.parse("20230516_0100", formatter).atZone(rigaZone)
+    val to = LocalDateTime.parse("20230516_1500", formatter).atZone(rigaZone)
+    val citiesNel = NonEmptyList.of("Rīga", "Rēzekne")
+    val granularity = "HOUR" // "HOUR", "DAY", "MONTH", "YEAR"
+    val columnName = "tempMin"
+
+    val baseQuery =
+      fr"""
+        SELECT
+          city,
+          MIN(""" ++ Fragment.const(columnName) ++ fr""") AS tempMin
+        FROM weather
+        WHERE
+          """ ++ Fragments.in(fr"city", citiesNel) ++ fr"""
+          AND dateTime BETWEEN $from AND $to
+          AND """ ++ Fragment.const(columnName) ++fr""" IS NOT NULL
+        GROUP BY city, EXTRACT(""" ++ Fragment.const(granularity) ++ fr""" FROM dateTime)
+      """
+
+    baseQuery
+      .query[(String, Option[Double])]
+      .to[List]
+      .transact(transactor)
+  }
+
+  def dropWeatherTable(): IO[Int] = {
+    for {
+      dropTableSql <- getResourceContent("/db/drop_weather_table.sql")
+      result <- Update0(dropTableSql, None).run.transact(transactor)
+    } yield result
+  }
+}