Merge pull request #12 from tomasf/frozen

Add a working frozen()

Sources/SwiftSCAD/Environment/DefaultEnvironment.swift

@@ -4,5 +4,6 @@ internal extension Environment {
     static var defaultEnvironment: Environment {
         Environment()
             .withFacets(.defaults)
+            .addingFreezeContext()
     }
 }

Sources/SwiftSCAD/Operations/Freeze.swift

@@ -1,33 +1,72 @@
 import Foundation
 
+internal extension Environment {
+    static private var environmentKey: Environment.ValueKey = .init(rawValue: "SwiftSCAD.FreezeContext")
+
+    class FreezeContext {
+        var frozenGeometryOutput: [AnyHashable: Any] = [:]
+
+        subscript<T>(_ key: AnyHashable) -> T? {
+            get { frozenGeometryOutput[key] as? T }
+            set { frozenGeometryOutput[key] = newValue }
+        }
+    }
+
+    var freezeContext: FreezeContext? {
+        self[Self.environmentKey] as? FreezeContext
+    }
+
+    func addingFreezeContext() -> Environment {
+        setting(key: Self.environmentKey, value: FreezeContext())
+    }
+}
+
 struct FrozenGeometry2D: Geometry2D {
-    let output: GeometryOutput2D
+    let body: any Geometry2D
+    let key: AnyHashable
 
     func output(in environment: Environment) -> Output {
-        output
+        if let output = environment.freezeContext?[key] as Output? {
+            return output
+        } else {
+            let output = body.output(in: environment)
+            environment.freezeContext?[key] = output
+            return output
+        }
     }
 }
 
 struct FrozenGeometry3D: Geometry3D {
-    let output: GeometryOutput3D
+    let body: any Geometry3D
+    let key: AnyHashable
 
     func output(in environment: Environment) -> Output {
-        output
+        if let output = environment.freezeContext?[key] as Output? {
+            return output
+        } else {
+            let output = body.output(in: environment)
+            environment.freezeContext?[key] = output
+            return output
+        }
     }
 }
 
 public extension Geometry2D {
-    func frozen() -> any Geometry2D {
-        EnvironmentReader { environment in
-            FrozenGeometry2D(output: self.output(in: environment))
-        }
+    func frozen<K: Hashable>(as key: K) -> any Geometry2D {
+        FrozenGeometry2D(body: self, key: key)
+    }
+
+    func frozen(_ file: String = #file, _ line: Int = #line) -> any Geometry2D {
+        FrozenGeometry2D(body: self, key: "\(file):\(line)")
     }
 }
 
 public extension Geometry3D {
-    func frozen() -> any Geometry3D {
-        EnvironmentReader { environment in
-            FrozenGeometry3D(output: self.output(in: environment))
-        }
+    func frozen<K: Hashable>(as key: K) -> any Geometry3D {
+        FrozenGeometry3D(body: self, key: key)
+    }
+
+    func frozen(_ file: String = #file, _ line: Int = #line) -> any Geometry3D {
+        FrozenGeometry3D(body: self, key: "\(file):\(line)")
     }
 }