1 files changed, 60 insertions, 0 deletions
diff --git a/core/src/main/scala/forge/eval/PathRef.scala b/core/src/main/scala/forge/eval/PathRef.scala
new file mode 100644
index 00000000..1c9bc700
--- /dev/null
+++ b/core/src/main/scala/forge/eval/PathRef.scala
@@ -0,0 +1,60 @@
+package forge.eval
+
+import java.io.IOException
+import java.nio.file.attribute.BasicFileAttributes
+import java.nio.file.{FileVisitResult, FileVisitor}
+import java.nio.{file => jnio}
+import java.security.MessageDigest
+
+import ammonite.ops.Path
+import forge.util.JsonFormatters
+import play.api.libs.json.{Format, Json}
+
+
+/**
+  * A wrapper around `ammonite.ops.Path` that calculates it's hashcode based
+  * on the contents of the filesystem underneath it. Used to ensure filesystem
+  * changes can bust caches which are keyed off hashcodes.
+  */
+case class PathRef(path: ammonite.ops.Path){
+  val md5Hash = {
+    val digest = MessageDigest.getInstance("MD5")
+
+    val buffer = new Array[Byte](16 * 1024)
+    jnio.Files.walkFileTree(
+      path.toNIO,
+      new FileVisitor[jnio.Path] {
+        def preVisitDirectory(dir: jnio.Path, attrs: BasicFileAttributes) = {
+          digest.update(dir.toAbsolutePath.toString.getBytes)
+          FileVisitResult.CONTINUE
+        }
+
+        def visitFile(file: jnio.Path, attrs: BasicFileAttributes) = {
+          digest.update(file.toAbsolutePath.toString.getBytes)
+          val is = jnio.Files.newInputStream(file)
+          def rec(): Unit = {
+            val length = is.read(buffer)
+            if (length != -1){
+              digest.update(buffer, 0, length)
+              rec()
+            }
+          }
+          rec()
+          FileVisitResult.CONTINUE
+        }
+
+        def visitFileFailed(file: jnio.Path, exc: IOException) = FileVisitResult.CONTINUE
+        def postVisitDirectory(dir: jnio.Path, exc: IOException) = FileVisitResult.CONTINUE
+      }
+    )
+
+    java.util.Arrays.hashCode(digest.digest())
+
+  }
+  override def hashCode() = md5Hash
+}
+
+object PathRef{
+  private implicit val pathFormat: Format[Path] = JsonFormatters.pathFormat
+  implicit def jsonFormatter: Format[PathRef] = Json.format
+}