Added support for configurable engine preferences (#3)

README.adoc

@@ -1,5 +1,7 @@
 = Travesty
-:issueBaseUrl: https://github.com/mikolak-net/travesty/issues/
+:repoBaseUrl: https://github.com/mikolak-net/travesty
+:fileBrowseBaseUrl: {repoBaseUrl}/blob/master/
+:issueBaseUrl: {repoBaseUrl}/issues/
 :toc:
 
 image:https://travis-ci.org/mikolak-net/travesty.svg?branch=master["Build Status", link="https://travis-ci.org/mikolak-net/travesty"]
@@ -139,6 +141,8 @@ The graph/diagram generated from the `Traversal` object does not correspond 1:1
 by `travesty`, for maximum portability, is also the slowest one. While generating the graph is always fast,
 rendering the diagram may take up to ~10 seconds.
 
+If you would like to try switching to a faster engine, see {fileBrowseBaseUrl}src/main/resources/reference.conf[`reference.conf`] for more info.
+
 === Tight coupling with Akka Stream's internals
 
 As mentioned before, `travesty` uses the internal API for graph/diagram generation. This is why the

src/main/resources/reference.conf

@@ -1,3 +1,5 @@
 travesty {
     cache.shape-cache-ttl = 5 minutes
+    #JDK is most platform-independent, but slowest. CommandLine is fastest, but requires external dependencies
+    engines = [JDK, V8, CommandLine]
 }

src/main/scala/net/mikolak/travesty/Api.scala

@@ -3,18 +3,20 @@ package net.mikolak.travesty
 import java.awt.image.BufferedImage
 import java.io.File
 
-import akka.stream.{ClosedShape, Graph, StreamDeconstructorProxy}
+import akka.stream.StreamDeconstructorProxy
 import gremlin.scala._
-import guru.nidi.graphviz.engine.{Graphviz, GraphvizCmdLineEngine, GraphvizJdkEngine, GraphvizV8Engine}
-import net.mikolak.travesty._
+import guru.nidi.graphviz.engine.Graphviz
+import net.mikolak.travesty.render.TypeNameSimplifier
+import net.mikolak.travesty.setup.GraphvizEngineType
+
 import org.log4s._
-import render.TypeNameSimplifier
 
 import scala.reflect.runtime.universe._
 
 private[travesty] class Api(deconstruct: StreamDeconstructorProxy,
                             typeNameSimplifier: TypeNameSimplifier,
-                            lowLevelApi: VizGraphProcessor) {
+                            lowLevelApi: VizGraphProcessor,
+                            engines: List[GraphvizEngineType.Value]) {
 
   private val logger = getLogger
 
@@ -49,6 +51,8 @@ private[travesty] class Api(deconstruct: StreamDeconstructorProxy,
   }
 
   { //initialize GraphViz engine
-    Graphviz.useEngine(new GraphvizJdkEngine, new GraphvizV8Engine, new GraphvizCmdLineEngine())
+    import GraphvizEngineType._
+    val first :: rest = engines.map(_.instantiate())
+    Graphviz.useEngine(first, rest: _*)
   }
 }

src/main/scala/net/mikolak/travesty/setup/GraphvizEngineType.scala

@@ -0,0 +1,14 @@
+package net.mikolak.travesty.setup
+
+import guru.nidi.graphviz.engine.{AbstractGraphvizEngine, GraphvizCmdLineEngine, GraphvizJdkEngine, GraphvizV8Engine}
+
+object GraphvizEngineType extends Enumeration {
+
+  protected case class Val(instantiate: () => AbstractGraphvizEngine) extends super.Val
+  implicit def valueToPlanetVal(x: Value): Val = x.asInstanceOf[Val]
+
+  val CommandLine = Val(() => new GraphvizCmdLineEngine())
+  val JDK         = Val(() => new GraphvizJdkEngine)
+  val V8          = Val(() => new GraphvizV8Engine)
+
+}

src/main/scala/net/mikolak/travesty/setup/TravestyConfig.scala

@@ -2,6 +2,6 @@ package net.mikolak.travesty.setup
 
 import scala.concurrent.duration.FiniteDuration
 
-private[travesty] case class TravestyConfig(cache: CacheConfig)
+private[travesty] case class TravestyConfig(cache: CacheConfig, engines: List[GraphvizEngineType.Value])
 
 private[travesty] case class CacheConfig(shapeCacheTtl: FiniteDuration)

src/main/scala/net/mikolak/travesty/setup/Wiring.scala

@@ -8,12 +8,14 @@ import net.ceedubs.ficus.readers.ArbitraryTypeReader._
 import net.mikolak.travesty.render.TypeNameSimplifier
 import net.mikolak.travesty.{Api, Registry, VizGraphProcessor}
 import net.ceedubs.ficus.readers.namemappers.implicits.hyphenCase
+import net.ceedubs.ficus.readers.EnumerationReader._
 
 private[travesty] object Wiring {
 
   lazy val baseConfig = ConfigFactory.load()
   lazy val config     = baseConfig.as[TravestyConfig]("travesty")
   import config.cache
+  import config.engines
 
   lazy val registry                 = wire[Registry]
   lazy val streamDeconstructorProxy = wire[StreamDeconstructorProxy]