Refactor save return type without Either

README.md

@@ -0,0 +1,38 @@
+# Weather Tool
+
+Tool for downloading historical and real-time data from 33 weather stations in Latvia. It aggregates and displays data for different time periods, cities, and weather parameters.
+
+## Run
+```
+// scala
+sbt run
+
+// web
+cd web/
+npm run dev
+```
+
+**Author:** Guntis Smaukstelis  
+**Mentor:** Jānis Komuls
+
+**Status:** Live  
+**URL:** [https://weather-tool.fly.dev/](https://weather-tool.fly.dev/)  
+**Used By:** State television weather news  
+**Repository:** [https://github.com/guntisdev/WeatherTool](https://github.com/guntisdev/WeatherTool)
+
+## Backend Technologies:
+- cats-effects
+- http4s
+- pureconfig
+- fs2
+- circe
+- scalatest
+
+## Frontend Technologies:
+- SolidJS
+- Vite
+
+## Deployment:
+- Docker
+- Shell script
+- Fly.io

src/main/scala/app/Main.scala

@@ -9,13 +9,17 @@ import server.Server
 object Main extends IOApp {
   def run(args: List[String]): IO[ExitCode] = {
     for {
+      // TODO run in separate thread
       dbService <- DBService.of
       dataService <- DataService.of(dbService)
+
       fetch <- FetchService.of
       fileFetchScheduler <- FileFetchScheduler.of(dataService, fetch)
       schedulerTask = fileFetchScheduler.run.compile.drain
+
       server <- Server.of(dataService, fetch)
       serverTask = server.run
+
       exitCode <- (serverTask, schedulerTask).parMapN((_, _) => ExitCode.Success)
     } yield exitCode
   }

src/main/scala/db/DBService.scala

@@ -40,14 +40,14 @@ class DBService(log: Logger[IO]) extends DataServiceTrait {
     }
   }
 
-  def save(fileName: String, content: String): IO[Either[Throwable, String]] = {
+  def save(fileName: String, content: String): IO[String] = {
     val path = Paths.get(s"$dataPath/$fileName")
     IO(Files.writeString(path, content))
-      .redeemWith(
-        error => IO(Left(error)) // <* log.error(s"Write file '$fileName' failed with error: ${error.getMessage}")
-        ,
-        _ => IO(Right(fileName)) // <* log.info(s"write: $fileName")
-      )
+      .attempt
+      .flatMap {
+        case Left(error) => log.error(s"Write file '$fileName' failed with error: ${error.getMessage}") *> IO.raiseError(error)
+        case Right(_) => log.info(s"write: $fileName").as(fileName)
+      }
   }
 
   def readFile(fileName: String): IO[List[String]] = {

src/main/scala/db/DataService.scala

@@ -9,7 +9,7 @@ import org.typelevel.log4cats.slf4j.Slf4jLogger
 import java.time.{Instant, LocalDate, LocalDateTime, ZoneId}
 
 trait DataServiceTrait {
-  def save(fileName: String, content: String): IO[Either[Throwable, String]]
+  def save(fileName: String, content: String): IO[String]
   def readFile(fileName: String): IO[List[String]]
   def getInRange(from: LocalDateTime, to: LocalDateTime): IO[List[String]]
   def getDates: IO[List[LocalDate]]
@@ -46,14 +46,15 @@ class DataService private(
     }
   }
 
-  def save(fileName: String, content: String): IO[Either[Throwable, String]] = {
-    dbService.save(fileName, content).flatMap {
-      case Right(savedFileName) =>
+  def save(fileName: String, content: String): IO[String] = {
+    dbService.save(fileName, content).redeemWith(
+      error => IO.raiseError(error),
+      savedFileName => {
         state.update(st => st.updated(savedFileName, content.split("\n").toList)) *>
-          filterState *>
-          logState.as(Right(savedFileName))
-      case e@Left(_) => IO.pure(e)
-    }
+            filterState *>
+            logState.as(savedFileName)
+      }
+    ).onError(error => log.info(s"errr... $error"))
   }
 
   def readFile(fileName: String): IO[List[String]] = dbService.readFile(fileName)

src/main/scala/fetch/FileFetchScheduler.scala

@@ -27,10 +27,7 @@ class FileFetchScheduler(dataService: DataServiceTrait, fetch: FetchService, fil
         case Right((name, content)) =>
           dataService.save(name, content).attempt.flatMap {
             case Left(err) => log.error(s"error: $err")
-            case Right(saveResult) => saveResult match {
-              case Left(err) => log.error(s"error: $err")
-              case Right(savedName) => log.info(s"saved: $savedName")
-            }
+            case Right(savedName) => log.info(s"saved: $savedName")
           }
       }
   }

src/main/scala/server/Server.scala

@@ -59,7 +59,7 @@ class Server(dataService: DataService, fetch: FetchService, log: Logger[IO]) {
         fetchServiceError = fetchResultEither.left.toOption.map(e => s"FetchServiceError: ${e.getMessage}").toList
         fetchResult = fetchResultEither.getOrElse(List.empty)
         (fetchErrors, successDownloads) = fetchResult.partitionMap(identity)
-        saveResults <- successDownloads.traverse { case (name, content) => dataService.save(name, content) }
+        saveResults <- successDownloads.traverse { case (name, content) => dataService.save(name, content).attempt }
         (saveErrors, successSaves) = saveResults.partitionMap(identity)
 //        successes = successDownloads.map(s => s"fetched: ${s._1}") ++ successSaves.map(s => s"saved: $s")
         successes = successSaves

src/test/scala/db/DBServiceSpec.scala

@@ -4,6 +4,7 @@ import cats.effect.unsafe.implicits.global
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
+import java.io.IOException
 import java.time.format.DateTimeFormatter
 import java.time.{LocalDate, LocalDateTime}
 
@@ -32,4 +33,26 @@ class DBServiceSpec extends AnyFunSuite with Matchers {
 
     lines.length shouldBe 2142
   }
+
+  test("DBService.save should return correct result") {
+    val dbService = DBService.of.unsafeRunSync()
+    val fileName = "testFile.txt"
+    val fileContent = "test content..."
+
+    dbService.save(fileName, fileContent).unsafeRunSync() shouldEqual fileName
+  }
+
+  test("DBService.save returns error on invalid file name") {
+    val dbService = DBService.of.unsafeRunSync()
+    val fileName = "/invalid/file/name"
+    val fileContent = "test content..."
+
+    val result = dbService.save(fileName, fileContent).attempt.unsafeRunSync()
+
+    result match {
+      case Left(e) =>
+        assert(e.isInstanceOf[IOException])
+      case Right(_) => fail("Expected failure did not occur")
+    }
+  }
 }

src/test/scala/fetch/FileFetchSchedulerSpec.scala

@@ -20,8 +20,8 @@ class FileFetchSchedulerSpec extends AsyncWordSpec with Matchers with IOSuite {
         refScheduler <- Ref.of[IO, Option[Either[Throwable, (String, String)]]](None)
         log <- Slf4jLogger.create[IO]
         dbService = new DBService(log) {
-          override def save(fileName: String, content: String): IO[Either[Throwable, String]] = {
-            refDb.set(Some(fileName)).as(Right(fileName))
+          override def save(fileName: String, content: String): IO[String] = {
+            refDb.set(Some(fileName)).as(fileName)
           }
         }
         fileNameService = new FileNameService {