1 files changed, 68 insertions, 0 deletions
diff --git a/src/main/scala/xyz/driver/pdsuicommon/db/EntityExtractorDerivation.scala b/src/main/scala/xyz/driver/pdsuicommon/db/EntityExtractorDerivation.scala
new file mode 100644
index 0000000..e13ea39
--- /dev/null
+++ b/src/main/scala/xyz/driver/pdsuicommon/db/EntityExtractorDerivation.scala
@@ -0,0 +1,68 @@
+package xyz.driver.pdsuicommon.db
+
+import java.sql.ResultSet
+
+import io.getquill.NamingStrategy
+import io.getquill.dsl.EncodingDsl
+
+import scala.language.experimental.macros
+import scala.reflect.macros.blackbox
+
+trait EntityExtractorDerivation[Naming <: NamingStrategy] {
+  this: EncodingDsl =>
+
+  /**
+    * Simple Quill extractor derivation for [[T]]
+    * Only case classes available. Type parameters is not supported
+    */
+  def entityExtractor[T]: (ResultSet => T) = macro EntityExtractorDerivation.impl[T]
+}
+
+object EntityExtractorDerivation {
+  def impl[T: c.WeakTypeTag](c: blackbox.Context): c.Tree = {
+    import c.universe._
+    val namingStrategy = c.prefix.actualType
+      .baseType(c.weakTypeOf[EntityExtractorDerivation[NamingStrategy]].typeSymbol)
+      .typeArgs
+      .head
+      .typeSymbol
+      .companion
+    val functionBody = {
+      val tpe = weakTypeOf[T]
+      val resultOpt = tpe.decls.collectFirst {
+        // Find first constructor of T
+        case cons: MethodSymbol if cons.isConstructor =>
+          // Create param list for constructor
+          val params = cons.paramLists.flatten.map { param =>
+            val t = param.typeSignature
+            val paramName = param.name.toString
+            val col = q"$namingStrategy.column($paramName)"
+            // Resolve implicit decoders (from SqlContext) and apply ResultSet for each
+            val d = q"implicitly[${c.prefix}.Decoder[$t]]"
+            // Minus 1 cause Quill JDBC decoders make plus one.
+            // ¯\_(ツ)_/¯
+            val i = q"row.findColumn($col) - 1"
+            val decoderName = TermName(paramName + "Decoder")
+            val valueName = TermName(paramName + "Value")
+            (
+              q"val $decoderName = $d",
+              q"val $valueName = $decoderName($i, row)",
+              valueName
+            )
+          }
+          // Call constructor with param list
+          q"""
+            ..${params.map(_._1)}
+            ..${params.map(_._2)}
+            new $tpe(..${params.map(_._3)})
+          """
+      }
+      resultOpt match {
+        case Some(result) => result
+        case None => c.abort(c.enclosingPosition,
+          s"Can not derive extractor for $tpe. Constructor not found.")
+      }
+    }
+    q"(row: java.sql.ResultSet) => $functionBody"
+  }
+}