From 84ba85b0639e94ebe7ac9b1a4cb9bcb01f1dc730 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tomas=20Franze=CC=81n?= <tomas@tomasf.se>
Date: Sun, 18 Feb 2024 22:09:35 +0100
Subject: [PATCH] Add Environment.Operation

---
 .../Environment/EnvironmentReader.swift       | 12 ++++--
 Sources/SwiftSCAD/Environment/Operation.swift | 38 +++++++++++++++++++
 .../Operations/Boolean/Difference.swift       |  2 +
 Tests/Tests/3DTests.swift                     | 27 +++++++++++++
 4 files changed, 75 insertions(+), 4 deletions(-)
 create mode 100644 Sources/SwiftSCAD/Environment/Operation.swift

diff --git a/Sources/SwiftSCAD/Environment/EnvironmentReader.swift b/Sources/SwiftSCAD/Environment/EnvironmentReader.swift
index d06faa1..8c1771c 100644
--- a/Sources/SwiftSCAD/Environment/EnvironmentReader.swift
+++ b/Sources/SwiftSCAD/Environment/EnvironmentReader.swift
@@ -25,13 +25,17 @@ public func EnvironmentReader(@UnionBuilder3D body: @escaping (Environment) -> a
 }
 
 public extension Geometry2D {
-    func readingEnvironment(@UnionBuilder2D _ body: @escaping (Environment) -> any Geometry2D) -> any Geometry2D {
-        EnvironmentReader2D(body: body)
+    func readingEnvironment(@UnionBuilder2D _ body: @escaping (any Geometry2D, Environment) -> any Geometry2D) -> any Geometry2D {
+        EnvironmentReader2D { environment in
+            body(self, environment)
+        }
     }
 }
 
 public extension Geometry3D {
-    func readingEnvironment(@UnionBuilder3D _ body: @escaping (Environment) -> any Geometry3D) -> any Geometry3D {
-        EnvironmentReader3D(body: body)
+    func readingEnvironment(@UnionBuilder3D _ body: @escaping (any Geometry3D, Environment) -> any Geometry3D) -> any Geometry3D {
+        EnvironmentReader3D { environment in
+            body(self, environment)
+        }
     }
 }
diff --git a/Sources/SwiftSCAD/Environment/Operation.swift b/Sources/SwiftSCAD/Environment/Operation.swift
new file mode 100644
index 0000000..687078a
--- /dev/null
+++ b/Sources/SwiftSCAD/Environment/Operation.swift
@@ -0,0 +1,38 @@
+import Foundation
+
+public extension Environment {
+    private static let key = Environment.ValueKey(rawValue: "SwiftSCAD.Operation")
+
+    enum Operation {
+        case addition
+        case subtraction
+
+        static prefix func !(_ op: Operation) -> Operation {
+            op == .addition ? .subtraction : .addition
+        }
+    }
+
+    var operation: Operation {
+        self[Self.key] as? Operation ?? .addition
+    }
+
+    internal func invertingOperation() -> Environment {
+        setting(key: Self.key, value: !operation)
+    }
+}
+
+internal extension Geometry2D {
+    func invertingOperation() -> any Geometry2D {
+        withEnvironment { environment in
+            environment.invertingOperation()
+        }
+    }
+}
+
+internal extension Geometry3D {
+    func invertingOperation() -> any Geometry3D {
+        withEnvironment { environment in
+            environment.invertingOperation()
+        }
+    }
+}
diff --git a/Sources/SwiftSCAD/Operations/Boolean/Difference.swift b/Sources/SwiftSCAD/Operations/Boolean/Difference.swift
index 2eaa55e..10e489a 100644
--- a/Sources/SwiftSCAD/Operations/Boolean/Difference.swift
+++ b/Sources/SwiftSCAD/Operations/Boolean/Difference.swift
@@ -7,6 +7,7 @@ struct Difference3D: CoreGeometry3D {
     init(positive: any Geometry3D, negative: any Geometry3D) {
         self.positive = positive
         self.negative = negative
+            .invertingOperation()
     }
 
     func call(in environment: Environment) -> SCADCall {
@@ -46,6 +47,7 @@ struct Difference2D: CoreGeometry2D {
     init(positive: any Geometry2D, negative: any Geometry2D) {
         self.positive = positive
         self.negative = negative
+            .invertingOperation()
     }
 
     func call(in environment: Environment) -> SCADCall {
diff --git a/Tests/Tests/3DTests.swift b/Tests/Tests/3DTests.swift
index 7d74d05..a83edfb 100644
--- a/Tests/Tests/3DTests.swift
+++ b/Tests/Tests/3DTests.swift
@@ -19,4 +19,31 @@ final class Geometry3DTests: XCTestCase {
             .adding {}
             .assertEqual(toFile: "empty3d")
     }
+
+    func testOperations() {
+        let testGeometry = Box([1,2,3])
+            .assertOperation(.addition)
+            .subtracting {
+                Sphere(diameter: 3)
+                    .assertOperation(.subtraction)
+                    .subtracting {
+                        Box([1,2,3])
+                            .assertOperation(.addition)
+                    }
+                    .assertOperation(.subtraction)
+            }
+            .assertOperation(.addition)
+
+        _ = testGeometry
+            .scadString(in: .defaultEnvironment)
+    }
+}
+
+extension Geometry3D {
+    func assertOperation(_ expectedOperation: Environment.Operation) -> any Geometry3D {
+        readingEnvironment { geo, environment in
+            XCTAssertEqual(environment.operation, expectedOperation)
+            geo
+        }
+    }
 }