From e7c743716f1e866ecb14aec5568d90dfe38c99b7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C3=ABl=20Lemaire?= <michael@thunderk.net>
Date: Wed, 13 Dec 2017 00:24:02 +0100
Subject: [PATCH] Fixed bad angle math when looking for ships in arc area

---
 src/core/ArenaLocation.spec.ts    | 12 +++++++-----
 src/core/ArenaLocation.ts         |  7 ++++---
 src/core/actions/TriggerAction.ts |  4 ++--
 3 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/src/core/ArenaLocation.spec.ts b/src/core/ArenaLocation.spec.ts
index d0fb030..b821e91 100644
--- a/src/core/ArenaLocation.spec.ts
+++ b/src/core/ArenaLocation.spec.ts
@@ -5,11 +5,13 @@ module TK.SpaceTac.Specs {
             check.nears(arenaAngle({ x: 0, y: 0 }, { x: 1, y: 1 }), Math.PI / 4);
         })
 
-        test.case("gets an angular distance", check => {
-            check.equals(angularDistance(0.5, 1.5), 1.0);
-            check.nears(angularDistance(0.5, 1.5 + Math.PI * 6), 1.0);
-            check.same(angularDistance(0.5, -0.5), -1.0);
-            check.nears(angularDistance(0.5, -0.3 - Math.PI * 4), -0.8);
+        test.case("computes an angular difference", check => {
+            check.equals(angularDifference(0.5, 1.5), 1.0);
+            check.nears(angularDifference(0.5, 1.5 + Math.PI * 6), 1.0);
+            check.same(angularDifference(0.5, -0.5), -1.0);
+            check.nears(angularDifference(0.5, -0.3 - Math.PI * 4), -0.8);
+            check.nears(angularDifference(-3 * Math.PI / 4, 3 * Math.PI / 4), -Math.PI / 2);
+            check.nears(angularDifference(3 * Math.PI / 4, -3 * Math.PI / 4), Math.PI / 2);
         })
 
         test.case("converts between degrees and radians", check => {
diff --git a/src/core/ArenaLocation.ts b/src/core/ArenaLocation.ts
index 9e0e5ee..59eed53 100644
--- a/src/core/ArenaLocation.ts
+++ b/src/core/ArenaLocation.ts
@@ -59,10 +59,11 @@ module TK.SpaceTac {
     }
 
     /**
-     * Get the "angular distance" between two angles in radians
+     * Get the "angular difference" between two angles in radians, in ]-pi,pi] range.
      */
-    export function angularDistance(angle1: number, angle2: number): number {
-        return (angle2 - angle1) % (Math.PI * 2);
+    export function angularDifference(angle1: number, angle2: number): number {
+        let diff = angle2 - angle1;
+        return diff - Math.PI * 2 * Math.floor((diff + Math.PI) / (Math.PI * 2));
     }
 
     /**
diff --git a/src/core/actions/TriggerAction.ts b/src/core/actions/TriggerAction.ts
index 28d527f..6694089 100644
--- a/src/core/actions/TriggerAction.ts
+++ b/src/core/actions/TriggerAction.ts
@@ -141,7 +141,7 @@ module TK.SpaceTac {
                     if (dist < 0.000001 || dist > this.range) {
                         return false;
                     } else {
-                        return Math.abs(angularDistance(arenaAngle(source, ship.location), angle)) < maxangle;
+                        return Math.abs(angularDifference(arenaAngle(source, ship.location), angle)) < maxangle;
                     }
                 });
             } else {
@@ -195,7 +195,7 @@ module TK.SpaceTac {
             if (arenaDistance(ship.location, target) > 1e-6) {
                 // Face the target
                 let angle = arenaAngle(ship.location, target);
-                if (Math.abs(angularDistance(angle, ship.arena_angle)) > 1e-6) {
+                if (Math.abs(angularDifference(angle, ship.arena_angle)) > 1e-6) {
                     let destination = new ArenaLocationAngle(ship.arena_x, ship.arena_y, angle);
                     let engine = first(ship.listEquipment(SlotType.Engine), () => true);
                     result.push(new ShipMoveDiff(ship, ship.location, destination, engine));