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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"
}
}
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