Add ChronoUnit ValueReader (#157)

src/main/scala/net/ceedubs/ficus/Ficus.scala

@@ -18,6 +18,7 @@ trait FicusInstances
     with ISOZonedDateTimeReader
     with PeriodReader
     with LocalDateReader
+    with ChronoUnitReader
     with URIReaders
     with URLReader
     with InetSocketAddressReaders

src/main/scala/net/ceedubs/ficus/readers/AllValueReaderInstances.scala

@@ -12,6 +12,7 @@ trait AllValueReaderInstances
     with TryReader
     with ConfigValueReader
     with PeriodReader
+    with ChronoUnitReader
     with LocalDateReader
 
 object AllValueReaderInstances extends AllValueReaderInstances

src/main/scala/net/ceedubs/ficus/readers/ChronoUnitReader.scala

@@ -0,0 +1,16 @@
+package net.ceedubs.ficus.readers
+
+import com.typesafe.config.Config
+
+import java.time.temporal.ChronoUnit
+
+trait ChronoUnitReader {
+  implicit val chronoUnitReader: ValueReader[ChronoUnit] = new ValueReader[ChronoUnit] {
+
+    /** Reads the value at the path `path` in the Config */
+    override def read(config: Config, path: String): ChronoUnit =
+      ChronoUnit.valueOf(config.getString(path).toUpperCase)
+  }
+}
+
+object ChronoUnitReader extends ChronoUnitReader

src/test/scala/net/ceedubs/ficus/readers/ChronoUnitReaderSpec.scala

@@ -0,0 +1,38 @@
+package net.ceedubs.ficus
+package readers
+
+import java.time.temporal.ChronoUnit
+
+import com.typesafe.config.ConfigFactory
+import Ficus.{chronoUnitReader, toFicusConfig}
+
+class ChronoUnitReaderSpec extends Spec {
+  def is = s2"""
+  The ChronoUnitReader should
+    read a ChronoUnit $readChronoUnit
+    read a lower case ChronoUnit $readChronoUnitLowerCase
+  """
+
+  def readChronoUnit = {
+    val cfg        = ConfigFactory.parseString(s"""
+                                                | foo {
+                                                |    chrono-unit = "MILLIS"
+                                                | }
+       """.stripMargin)
+    val chronoUnit = cfg.as[ChronoUnit]("foo.chrono-unit")
+    val expected   = ChronoUnit.MILLIS
+    chronoUnit should_== expected
+  }
+
+  def readChronoUnitLowerCase = {
+    val cfg        = ConfigFactory.parseString(s"""
+                                                | foo {
+                                                |    chrono-unit = "millis"
+                                                | }
+       """.stripMargin)
+    val chronoUnit = cfg.as[ChronoUnit]("foo.chrono-unit")
+    val expected   = ChronoUnit.MILLIS
+    chronoUnit should_== expected
+  }
+
+}