CollisionHelpers extraction and tests

.eslintrc.yml

@@ -168,7 +168,7 @@ rules:
   no-whitespace-before-property: error
   no-with: error
   nonblock-statement-body-position: error
-  object-curly-newline: error
+  object-curly-newline: off
   object-curly-spacing: error
   object-property-newline: error
   object-shorthand: error

lib/aa-rectangle.js

@@ -1,5 +1,7 @@
 'use strict';
 
+const {segmentsCollide} = require('./collision-helpers');
+
 let AARectangleId = 0;
 
 class AARectangle {
@@ -50,14 +52,6 @@ class AARectangle {
     return this._x;
   }
 
-  // get x1 () {
-  //   return this._x - (this._width / 2) + (this.translateX * this.orientationX);
-  // }
-
-  // get x2 () {
-  //   return this._x + (this._width / 2) + (this.translateX * this.orientationX);
-  // }
-
   set x (value) {
     this._x = value || 0;
   }
@@ -66,14 +60,6 @@ class AARectangle {
     return this._y;
   }
 
-  // get y1 () {
-  //   return this._y - (this._height / 2) + (this.translateY * this.orientationY);
-  // }
-
-  // get y2 () {
-  //   return this._y + (this._height / 2) + (this.translateY * this.orientationY);
-  // }
-
   set y (value) {
     this._y = value || 0;
   }
@@ -95,10 +81,14 @@ class AARectangle {
     }
     this.globalX = globalX;
     this.globalY = globalY;
-    this.globalX1 = globalX - (this._width / 2) + (this.translateX * this.orientationX);
-    this.globalX2 = globalX + (this._width / 2) + (this.translateX * this.orientationX);
-    this.globalY1 = globalY - (this._height / 2) + (this.translateY * this.orientationY);
-    this.globalY2 = globalY + (this._height / 2) + (this.translateY * this.orientationY);
+    const halfX = this._width / 2;
+    const extraX = this.translateX * this.orientationX;
+    this.globalX1 = globalX - halfX + extraX;
+    this.globalX2 = globalX + halfX + extraX;
+    const halfY = this._height / 2;
+    const extraY = this.translateY * this.orientationY;
+    this.globalY1 = globalY - halfY + extraY;
+    this.globalY2 = globalY + halfY + extraY;
   }
 
   add (box) {
@@ -141,13 +131,6 @@ class AARectangle {
 
 }
 
-// Helpers
-
-function segmentsCollide (segment1_start, segment1_end, segment2_start, segment2_end) {
-  return segment1_end >= segment2_start &&
-         segment1_start <= segment2_end;
-}
-
 function parseDimensionValue (value) {
   let newValue = value || 1;
   if (newValue < 0) {

lib/collision-helpers.js

@@ -0,0 +1,8 @@
+'use strict';
+
+module.exports = {segmentsCollide};
+
+function segmentsCollide (segment1_start, segment1_end, segment2_start, segment2_end) {
+  return segment1_end >= segment2_start &&
+         segment1_start <= segment2_end;
+}

test/collision-helpers.js

@@ -0,0 +1,32 @@
+'use strict';
+
+const {segmentsCollide} = require('../lib/collision-helpers');
+const expect = require('chai').expect;
+
+describe('CollisionHelpers', function () {
+
+  describe('.segmentsCollide', function () {
+
+    it('returns true if segments touch', function () {
+      expect(segmentsCollide(1, 2, 2, 3)).to.equal(true);
+      expect(segmentsCollide(2, 3, 1, 2)).to.equal(true);
+    });
+
+    it('returns true if segments intersect', function () {
+      expect(segmentsCollide(1, 2.5, 2, 3)).to.equal(true);
+      expect(segmentsCollide(1.9, 3, 1, 2)).to.equal(true);
+    });
+
+    it('returns true if one segment is inside the other', function () {
+      expect(segmentsCollide(1, 5, 2, 3)).to.equal(true);
+      expect(segmentsCollide(2, 3, 1, 5)).to.equal(true);
+    });
+
+    it('returns false if segments do not touch or intersect', function () {
+      expect(segmentsCollide(1, 2, 3, 4)).to.equal(false);
+      expect(segmentsCollide(3, 4, 1, 2)).to.equal(false);
+    });
+
+  });
+
+});