Fix "cross" detection on firing in some cases

Fixes #578

internal/server/aof.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"math"
 	"net"
 	"os"
 	"sort"
@@ -14,7 +15,7 @@ import (
 	"time"
 
 	"github.com/tidwall/buntdb"
-	"github.com/tidwall/geojson"
+	"github.com/tidwall/geojson/geometry"
 	"github.com/tidwall/gjson"
 	"github.com/tidwall/redcon"
 	"github.com/tidwall/resp"
@@ -213,11 +214,23 @@ func (s *Server) getQueueCandidates(d *commandDetails) []*Hook {
 		}
 	}
 	// search the hook spatial tree
-	for _, obj := range []geojson.Object{d.obj, d.oldObj} {
-		if obj == nil {
-			continue
+	// build a rectangle that fills the old and new which will be enough to
+	// handle "enter", "inside", "exit", and "cross" detections.
+	var rect geometry.Rect
+	if d.oldObj != nil {
+		rect = d.oldObj.Rect()
+		if d.obj != nil {
+			r2 := d.obj.Rect()
+			rect.Min.X = math.Min(rect.Min.X, r2.Min.X)
+			rect.Min.Y = math.Min(rect.Min.Y, r2.Min.Y)
+			rect.Max.X = math.Max(rect.Max.X, r2.Max.X)
+			rect.Max.Y = math.Max(rect.Max.Y, r2.Max.Y)
+		}
+	} else if d.obj != nil {
+		rect = d.obj.Rect()
+	} else {
+		return candidates
 	}
-		rect := obj.Rect()
 	s.hookTree.Search(
 		[2]float64{rect.Min.X, rect.Min.Y},
 		[2]float64{rect.Max.X, rect.Max.Y},
@@ -239,7 +252,6 @@ func (s *Server) getQueueCandidates(d *commandDetails) []*Hook {
 			return true
 		},
 	)
-	}
 	return candidates
 }