server: Add Address model

server/app/com/xsn/explorer/models/Address.scala

@@ -0,0 +1,32 @@
+package com.xsn.explorer.models
+
+import play.api.libs.json._
+
+class Address private (val string: String) extends AnyVal
+
+object Address {
+
+  private val pattern = "^[a-zA-Z0-9]{34}$".r.pattern
+
+  def from(string: String): Option[Address] = {
+    if (pattern.matcher(string).matches()) {
+      Some(new Address(string))
+    } else {
+      None
+    }
+  }
+
+  implicit val reads: Reads[Address] = Reads { json =>
+    json.validate[String].flatMap { string =>
+      from(string)
+          .map(JsSuccess.apply(_))
+          .getOrElse {
+            JsError.apply("Invalid address")
+          }
+    }
+  }
+
+  implicit val writes: Writes[Address] = Writes { obj =>
+    JsString(obj.string)
+  }
+}