homework_8 - Юн Вадим

homeworks/homework_8/src/main/scala/Exercises.scala

@@ -1,3 +1,39 @@
 import scala.util.Try
+import scala.util.matching.Regex
+
 object Exercises {
+
+  val regSome = new Regex("""Some\((\S+)\)""")
+
+  trait Read[T] {
+    def read(str: String): Either[String, T]
+  }
+
+  implicit class ImplicitRead(str: String) {
+    def read[T]()(implicit read: Read[T]): Either[String, T] = read.read(str)
+  }
+
+  object Read {
+    def read[T](str: String)(implicit read: Read[T]): Either[String, T] = read.read(str)
+
+    implicit object readString extends Read[String] {
+      def read(str: String): Either[String, String] = Right(str)
+    }
+
+    implicit object readInt extends Read[Int] {
+      def read(str: String): Either[String, Int] = Try(str.toInt).toOption match {
+        case Some(value) => Right(value)
+        case None => Left("failed to parse")
+      }
+    }
+
+    implicit def readOption[T: Read]: Read[Option[T]] = {
+      case regSome(value) => value.read[T] match {
+        case Right(value) => Right(Some(value))
+        case Left(_) => Left("failed to read option")
+      }
+      case "None" => Right(None)
+      case _ => Left("Unexpected")
+    }
+  }
 }