From 828cc12194663f107a08251bbabc256ae0d7c936 Mon Sep 17 00:00:00 2001
From: vlad <vlad@drivergrp.com>
Date: Thu, 8 Dec 2016 18:52:37 -0800
Subject: General GADT json format

---
 src/main/scala/xyz/driver/core/json.scala | 48 +++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

(limited to 'src/main/scala/xyz/driver')

diff --git a/src/main/scala/xyz/driver/core/json.scala b/src/main/scala/xyz/driver/core/json.scala
index 66cae52..277543b 100644
--- a/src/main/scala/xyz/driver/core/json.scala
+++ b/src/main/scala/xyz/driver/core/json.scala
@@ -107,4 +107,52 @@ object json {
       case _               => deserializationError(s"Expected number as ${typeOf[T].getClass.getName}, but got " + json)
     }
   }
+
+  class GadtJsonFormat[T: TypeTag](typeField: String,
+                                   typeValue: PartialFunction[T, String],
+                                   jsonFormat: PartialFunction[String, JsonFormat[_ <: T]])
+      extends RootJsonFormat[T] {
+
+    def write(value: T): JsValue = {
+
+      val valueType = typeValue.applyOrElse(value, { v: T =>
+        deserializationError(s"No Value type for this type of ${typeOf[T].getClass.getName}: " + v)
+      })
+
+      val valueFormat =
+        jsonFormat.applyOrElse(valueType, { f: String =>
+          deserializationError(s"No Json format for this type of $valueType")
+        })
+
+      valueFormat.asInstanceOf[JsonFormat[T]].write(value) match {
+        case JsObject(fields) => JsObject(fields ++ Map(typeField -> JsString(valueType)))
+        case _                => serializationError(s"${typeOf[T].getClass.getName} serialized not to a JSON object")
+      }
+    }
+
+    def read(json: JsValue): T = json match {
+      case JsObject(fields) =>
+        val valueJson = JsObject(fields.filterNot(_._1 == typeField))
+        fields(typeField) match {
+          case JsString(valueType) =>
+            val valueFormat = jsonFormat.applyOrElse(valueType, { t: String =>
+              deserializationError(s"Unknown ${typeOf[T].getClass.getName} type ${fields(typeField)}")
+            })
+            valueFormat.read(valueJson)
+          case _ =>
+            deserializationError(s"Unknown ${typeOf[T].getClass.getName} type ${fields(typeField)}")
+        }
+      case _ =>
+        deserializationError(s"Expected Json Object as ${typeOf[T].getClass.getName}, but got " + json)
+    }
+  }
+
+  object GadtJsonFormat {
+
+    def create[T: TypeTag](typeField: String)(typeValue: PartialFunction[T, String])(
+            jsonFormat: PartialFunction[String, JsonFormat[_ <: T]]) = {
+
+      new GadtJsonFormat[T](typeField, typeValue, jsonFormat)
+    }
+  }
 }
-- 
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