Melee 'facing' code updated to client derived function

These new functions are derived from the client
The need was because the old function sometimes didn't line
up with the client generated messages.

zone/mob.cpp

@@ -5046,3 +5046,52 @@ void Mob::ProcessSpecialAbilities(const std::string str) {
 		}
 	}
 }
+
+// derived from client to keep these functions more consistent
+// if anything seems weird, blame SoE
+bool Mob::IsFacingMob(Mob *other)
+{
+	float angle = HeadingAngleToMob(other);
+	// what the client uses appears to be 2x our internal heading
+	float heading = GetHeading() * 2.0;
+
+	if (angle > 472.0 && heading < 40.0)
+		angle = heading;
+	if (angle < 40.0 && heading > 472.0)
+		angle = heading;
+
+	if (fabs(angle - heading) <= 80.0)
+		return true;
+
+	return false;
+}
+
+// All numbers derived from the client
+float Mob::HeadingAngleToMob(Mob *other)
+{
+	float mob_x = other->GetX();
+	float mob_y = other->GetY();
+	float this_x = GetX();
+	float this_y = GetY();
+
+	float y_diff = fabs(this_y - mob_y);
+	float x_diff = fabs(this_x - mob_x);
+	if (y_diff < 0.0000009999999974752427)
+		y_diff = 0.0000009999999974752427;
+
+	float angle = atan2(x_diff, y_diff) * 180.0 * 0.3183099014828645; // angle, nice "pi"
+
+	// return the right thing based on relative quadrant
+	// I'm sure this could be improved for readability, but whatever
+	if (this_y >= mob_y) {
+		if (mob_x >= this_x)
+			return (90.0 - angle + 90.0) * 511.5 * 0.0027777778;
+		if (mob_x <= this_x)
+			return (angle + 180.0) * 511.5 * 0.0027777778;
+	}
+	if (this_y > mob_y || mob_x > this_x)
+		return angle * 511.5 * 0.0027777778;
+	else
+		return (90.0 - angle + 270.0) * 511.5 * 0.0027777778;
+}
+