Build fixed Faktiska production workflow

src/main/scala/db/PostgresService.scala

@@ -28,6 +28,18 @@ object PostgresService {
 }
 
 class PostgresService(transactor: Transactor[IO], log: Logger[IO]) {
+  def queryLatestTemperatures(cities: NonEmptyList[String]): IO[List[(String, LocalDateTime, Option[Double])]] = {
+    val query =
+      fr"SELECT DISTINCT ON (city) city, dateTime, tempAvg" ++
+        fr" FROM weather" ++
+        fr" WHERE " ++ Fragments.in(fr"city", cities) ++
+        fr" ORDER BY city, dateTime DESC"
+
+    query.query[(String, LocalDateTime, Option[Double])]
+      .to[List]
+      .transact(transactor)
+  }
+
   def save(fileName: String, content: String): IO[String] = {
     val YearPattern: Regex = """(\d{4})\d{4}_\d{4}\.csv""".r
 

src/main/scala/server/Server.scala

@@ -49,6 +49,7 @@ class Server(postgresService: PostgresService, dataService: DataService, fetch:
   }
 
   private case class ResponseWrapper(result: Map[String, Option[Aggregate.AggregateValue]], query: UserQuery)
+  private case class LatestTemperature(city: String, observedAt: String, value: Option[Double])
 
   private val apiRoutes = HttpRoutes.of[IO] {
     // http://0.0.0.0:8080/api/show/lvgmc-forecast/Latvija_LTV_pilsetas_tekosa_dn.csv
@@ -127,6 +128,12 @@ class Server(postgresService: PostgresService, dataService: DataService, fetch:
         .map(result => ResponseWrapper(result, userQuery))
         .flatMap(responseWrapper => Ok(responseWrapper.asJson.pretty))
 
+    // Latest observation-time temperatures for a fixed production station set.
+    case GET -> Root / "query" / "latest-temperatures" / CityList(cities) =>
+      postgresService.queryLatestTemperatures(cities)
+        .map(_.map { case (city, observedAt, value) => LatestTemperature(city, observedAt.toString, value) })
+        .flatMap(result => Ok(result.asJson.pretty))
+
     // http://0.0.0.0:8080/api/query/city/Kolka/20230414_2200-20230501_1230/allFields
     case GET -> Root / "query" / "city" / (city: String) / DateTimeRange(from, to) / "allFields" =>
       postgresService.queryCityAllFields(city, from, to).flatMap(result => Ok(result.asJson))