Make obstacles know how to minify themselves

including a fix for using pointers instead of values.

obstacle.go

@@ -1,6 +1,7 @@
 package server
 
 import (
+	"encoding/json"
 	"math"
 	"math/rand"
 
@@ -13,6 +14,30 @@ type Obstacle struct {
 	Hp     int      `json:"-"`
 }
 
+func (o *Obstacle) MarshalJSON() ([]byte, error) {
+	payload := [4]float64{
+		o.Bounds.A.X,
+		o.Bounds.A.Y,
+
+		o.Bounds.B.X,
+		o.Bounds.B.Y,
+	}
+	return json.Marshal(payload)
+}
+
+func (o *Obstacle) UnmarshalJSON(incoming []byte) error {
+	payload := [4]float64{}
+	err := json.Unmarshal(incoming, &payload)
+	if err != nil {
+		return err
+	}
+	o.Bounds = v.AABB2d{
+		A: v.Point2d{X: payload[0], Y: payload[1]},
+		B: v.Point2d{X: payload[2], Y: payload[3]},
+	}
+	return nil
+}
+
 func (o Obstacle) distance_from_point(p v.Point2d) float64 {
 	dist := math.MaxFloat32
 
@@ -24,21 +49,6 @@ func (o Obstacle) distance_from_point(p v.Point2d) float64 {
 	return dist
 }
 
-func (o Obstacle) minify() [4]int {
-	out := [4]int{int(o.Bounds.A.X), int(o.Bounds.A.Y), int(o.Bounds.B.X), int(o.Bounds.B.Y)}
-	return out
-}
-
-// MinifyObstacles is a function used to convert []osbstacles into more tightly
-// packed [][4]int for smaller json payloads
-func MinifyObstacles(o []Obstacle) [][4]int {
-	out := [][4]int{}
-	for i := range o {
-		out = append(out, o[i].minify())
-	}
-	return out
-}
-
 // GenerateObstacles returns a slice of (count) obstacles within a region
 // bounded by width, height.
 func GenerateObstacles(count int, width, height float64) []Obstacle {