Trait-based initialization and other utilities

Adds the concept of a 'platform', a centralized place in which
environment-specific information will be managed, and provides common
initialization logic for most "standard" apps.

As part of the common initialization, other parts of core have also
been reworked:

- HTTP-related unmarshallers and path matchers have been factored out
  from core.json to a new core.rest.directives package (core.json
  extends those unmarshallers and matchers for backwards
  compatibility)

- CORS handling has also been moved to a dedicated utility trait

- Some custom headers have been moved from raw headers to typed ones
  in core.rest.headers

- The concept of a "reporter" has been introduced. A reporter is a
  context-aware combination of tracing and logging. It is intended to
  issue diagnostic messages that can be traced across service
  boundaries.

Closes #192
Closes #195

1 files changed, 37 insertions, 0 deletions

diff --git a/src/main/scala/xyz/driver/core/init/BuildInfoReflection.scala b/src/main/scala/xyz/driver/core/init/BuildInfoReflection.scala
new file mode 100644
index 0000000..0e53085
--- /dev/null
+++ b/src/main/scala/xyz/driver/core/init/BuildInfoReflection.scala
@@ -0,0 +1,37 @@
+package xyz.driver.core
+package init
+
+import scala.reflect.runtime
+import scala.util.Try
+import scala.util.control.NonFatal
+
+/** Utility object to retrieve fields from static build configuration objects. */
+private[init] object BuildInfoReflection {
+
+  final val BuildInfoName = "xyz.driver.BuildInfo"
+
+  lazy val name: String            = get[String]("name")
+  lazy val version: Option[String] = find[String]("version")
+
+  /** Lookup a given field in the build configuration. This field is required to exist. */
+  private def get[A](fieldName: String): A =
+    try {
+      val mirror   = runtime.currentMirror
+      val module   = mirror.staticModule(BuildInfoName)
+      val instance = mirror.reflectModule(module).instance
+      val accessor = module.info.decl(mirror.universe.TermName(fieldName)).asMethod
+      mirror.reflect(instance).reflectMethod(accessor).apply().asInstanceOf[A]
+    } catch {
+      case NonFatal(err) =>
+        throw new RuntimeException(
+          s"Cannot find field name '$fieldName' in $BuildInfoName. Please define (or generate) a singleton " +
+            s"object with that field. Alternatively, in order to avoid runtime reflection, you may override the " +
+            s"caller with a static value.",
+          err
+        )
+    }
+
+  /** Try finding a given field in the build configuration. If the field does not exist, None is returned. */
+  private def find[A](fieldName: String): Option[A] = Try { get[A](fieldName) }.toOption
+
+}