Merge pull request #3 from quephird/improve_app_protocol

Output filename is now that of the class name with the ppm extension.

Sources/ScintillaLib/ScintillaApp.swift

@@ -8,16 +8,18 @@
 import Foundation
 
 public protocol ScintillaApp {
-    var filename: String { get set }
-    @WorldBuilder var body: (Light, Camera, [Shape]) { get }
+    @WorldBuilder var body: World { get }
 
     init()
 }
 
 extension ScintillaApp {
     public static func main() {
         let instance = Self()
-        let canvas = World { return instance.body }.render()
-        canvas.save(to: instance.filename)
+        let instanceBody = instance.body
+        let canvas = instanceBody.render()
+
+        let outputFilename = String(describing: self) + ".ppm"
+        canvas.save(to: outputFilename)
     }
 }

Sources/ScintillaLib/World.swift

@@ -14,11 +14,8 @@ public struct World {
     var camera: Camera
     var objects: [Shape]
 
-    public init(@WorldBuilder builder: () -> (Light, Camera, [Shape])) {
-        let (light, camera, shapes) = builder()
-        self.light = light
-        self.camera = camera
-        self.objects = shapes
+    public init(@WorldBuilder builder: () -> World) {
+        self = builder()
     }
 
     public init(_ light: Light, _ camera: Camera, @ShapeBuilder builder: () -> [Shape]) {

Sources/ScintillaLib/WorldBuilder.swift

@@ -7,6 +7,11 @@
 
 @resultBuilder
 public enum WorldBuilder {
+    public static func buildFinalResult(_ component: (Light, Camera, [Shape])) -> World {
+        let (light, camera, shapes) = component
+        return World(light, camera, shapes)
+    }
+
     public static func buildBlock(_ light: Light, _ camera: Camera, _ shapes: [Shape]...) -> (Light, Camera, [Shape]) {
         return (light, camera, Array(shapes.joined()))
     }