Step 5.3: Create 'Line' class

Author: DAB0mB

resources/scripts/engine/geometry/line.js

@@ -0,0 +1,65 @@
+Engine.Geometry.Line = class Line {
+  // x1 - The first point's x value
+  // y1 - The first point's y value
+  // x1 - The second point's x value
+  // y2 - The second point's y value
+  constructor(x1, y1, x2, y2) {
+    this.x1 = Utils.trim(x1, 9);
+    this.y1 = Utils.trim(y1, 9);
+    this.x2 = Utils.trim(x2, 9);
+    this.y2 = Utils.trim(y2, 9);
+  }
+
+  // Draws the line on the given context
+  draw(context) {
+    context.moveTo(this.x1, this.y1);
+    context.lineTo(this.x2, this.y2);
+  }
+
+  // Gets the matching x value for a given y value
+  getX(y) {
+    let x = Utils.trim((((y - this.y1) * (this.x2 - this.x1)) / (this.y2 - this.y1)) + this.x1, 9);
+    if (isNaN(x) || Utils.isBetween(x, this.x1, this.x2)) return x;
+  }
+
+  // Gets the matching y value for a given x value
+  getY(x) {
+    let y = Utils.trim((((x - this.x1) * (this.y2 - this.y1)) / (this.x2 - this.x1)) + this.y1, 9);
+    if (isNaN(y) || Utils.isBetween(y, this.y1, this.y2)) return y;
+  }
+
+  // Returns if line has given point
+  hasPoint(x, y) {
+    if (!this.boundsHavePoint(x, y)) return false;
+    let m = Utils.trim((this.y2 - this.y1) / (this.x2 - this.x1), 9);
+    return (y - this.y1) / (x - this.x1) == m;
+  }
+
+  // Returns if given point is contained by the bounds aka cage of line
+  boundsHavePoint(x, y) {
+    return Utils.isBetween(x, this.x1, this.x2) &&
+           Utils.isBetween(y, this.y1, this.y2);
+  }
+
+  getIntersection(shape) {
+    if (shape instanceof Engine.Geometry.Line)
+      return this.getLineIntersection(shape);
+  }
+
+  // line - line intersection method
+  getLineIntersection(line) {
+    // Escape if lines are parallel
+    if (!(((this.x1 - this.x2) * (line.y1 - line.y2)) - ((this.y1 - this.y2) * (line.x1 - line.x2)))) return;
+
+    // Intersection point formula
+    let x = Utils.trim(((((this.x1 * this.y2) - (this.y1 * this.x2)) * (line.x1 - line.x2)) - ((this.x1 - this.x2) * ((line.x1 * line.y2) - (line.y1 * line.x2)))) /
+        (((this.x1 - this.x2) * (line.y1 - line.y2)) - ((this.y1 - this.y2) * (line.x1 - line.x2))), 9);
+    let y = Utils.trim(((((this.x1 * this.y2) - (this.y1 * this.x2)) * (line.y1 - line.y2)) - ((this.y1 - this.y2) * ((line.x1 * line.y2) - (line.y1 * line.x2)))) /
+        (((this.x1 - this.x2) * (line.y1 - line.y2)) - ((this.y1 - this.y2) * (line.x1 - line.x2))), 9);
+
+    if (Utils.isBetween(x, this.x1, this.x2) && Utils.isBetween(x, line.x1, line.x2) &&
+        Utils.isBetween(y, this.y1, this.y2) && Utils.isBetween(y, line.y1, line.y2)) {
+      return { x, y };
+    }
+  }
+};

views/game.html

@@ -10,6 +10,7 @@
     <!-- Scripts -->
     <script type="text/javascript" src="/scripts/utils.js"></script>
     <script type="text/javascript" src="/scripts/namespaces.js"></script>
+    <script type="text/javascript" src="/scripts/engine/geometry/line.js"></script>
     <script type="text/javascript" src="/scripts/engine/restorable.js"></script>
     <script type="text/javascript" src="/scripts/engine/font.js"></script>
     <script type="text/javascript" src="/scripts/engine/sprite.js"></script>