computing frame deltas

internal/sim/door.go

@@ -56,6 +56,7 @@ func (d *door) exec(w *world, r *room, p *player, seq int) result {
 		p.Error("failed to add player avatar to tile %v", t)
 	}
 	dest.addPlayer(p)
+	p.fullSync = true
 	return result{}
 }
 

internal/sim/player.go

@@ -13,12 +13,12 @@ import (
 
 type player struct {
 	*blammo.Log
-	//*room
-	name    string
-	outbox  chan wire.Response
-	pending *Request
-	avatar  *entity
-	stop    chan bool
+	name     string
+	outbox   chan wire.Response
+	pending  *Request
+	avatar   *entity
+	stop     chan bool
+	fullSync bool
 }
 
 func (p *player) start(c chan Request, conn *websocket.Conn, r *room) {
@@ -167,6 +167,7 @@ func (p *player) update(dt time.Duration) {}
 type spawnPlayer struct{}
 
 func (s spawnPlayer) exec(w *world, r *room, p *player, seq int) result {
+	p.fullSync = true
 	e := entity{
 		ID:       <-w.nextID,
 		Glyph:    '@',

internal/sim/room.go

@@ -10,8 +10,9 @@ type room struct {
 	*blammo.Log
 	name string
 	math.Rect
-	tiles   []tile
-	players map[string]*player
+	tiles     []tile
+	players   map[string]*player
+	lastFrame wire.Frame
 }
 
 func (r *room) allEntities() map[int]wire.Entity {

internal/sim/world.go

@@ -284,6 +284,12 @@ func (w *world) tick(d time.Duration) {
 			Players:  r.playerAvatars(),
 		}
 
+		delta := r.lastFrame.Diff(frame)
+		if delta != nil {
+			w.Info("%s delta: %s", r.name, delta)
+		}
+		r.lastFrame = frame
+
 		for _, p := range r.players {
 			p.send(wire.Response{Body: frame})
 		}

internal/wire/frame.go

@@ -1,6 +1,13 @@
 package wire
 
-import "github.com/jordanorelli/astro-domu/internal/math"
+import (
+	"bytes"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/jordanorelli/astro-domu/internal/math"
+)
 
 type Frame struct {
 	RoomName string         `json:"room_name"`
@@ -11,6 +18,141 @@ type Frame struct {
 
 func (Frame) NetTag() string { return "frame" }
 
+func (f Frame) Diff(next Frame) *Delta {
+	var delta Delta
+
+	if f.RoomSize != next.RoomSize {
+		rs := next.RoomSize
+		delta.RoomSize = &rs
+	}
+
+	for id, e := range next.Entities {
+		if old, ok := f.Entities[id]; !ok {
+			// a new entity
+			delta.addEntity(e)
+		} else {
+			// an existing entity
+			if e != old {
+				delta.addEntity(e)
+			}
+		}
+	}
+
+	for id, _ := range f.Entities {
+		// entity removed
+		if _, ok := next.Entities[id]; !ok {
+			delta.nullEntity(id)
+		}
+	}
+
+	for name, id := range next.Players {
+		if oldID, ok := f.Players[name]; !ok {
+			// a new player
+			delta.addPlayer(name, id)
+		} else {
+			// an existing player
+			if oldID != id {
+				delta.addPlayer(name, id)
+			}
+		}
+	}
+
+	for name, _ := range f.Players {
+		if _, ok := next.Players[name]; !ok {
+			delta.nullPlayer(name)
+		}
+	}
+	if !delta.IsEmpty() {
+		return &delta
+	}
+	return nil
+}
+
+type Delta struct {
+	RoomSize *math.Rect      `json:"room_size,omitempty"`
+	Entities map[int]*Entity `json:"entities,omitempty"`
+	Players  map[string]*int `json:"players,omitempty"`
+}
+
+func (d Delta) String() string {
+	first := true
+	var buf bytes.Buffer
+	fmt.Fprint(&buf, "Δ{")
+	if d.RoomSize != nil {
+		fmt.Fprintf(&buf, "size(%d,%d@%d,%d)", d.RoomSize.Origin.X, d.RoomSize.Origin.Y, d.RoomSize.Width, d.RoomSize.Height)
+		first = false
+	}
+	if len(d.Entities) > 0 {
+		if !first {
+			buf.WriteString(",")
+		}
+		buf.WriteString("entities<")
+		parts := make([]string, 0, len(d.Entities))
+		for id, e := range d.Entities {
+			if e == nil {
+				parts = append(parts, fmt.Sprintf("-%d", id))
+			} else {
+				parts = append(parts, strconv.Itoa(id))
+			}
+		}
+		buf.WriteString(strings.Join(parts, ","))
+		buf.WriteString(">")
+		first = false
+	}
+	if len(d.Players) > 0 {
+		if !first {
+			buf.WriteString(",")
+		}
+		buf.WriteString("players<")
+		parts := make([]string, 0, len(d.Players))
+		for name, id := range d.Players {
+			if id == nil {
+				parts = append(parts, fmt.Sprintf("-%s", name))
+			} else {
+				parts = append(parts, fmt.Sprintf("+%s", name))
+			}
+		}
+		buf.WriteString(strings.Join(parts, ","))
+		buf.WriteString(">")
+		first = false
+	}
+	return buf.String()
+}
+
+func (Delta) NetTag() string { return "delta" }
+
+func (d *Delta) addEntity(e Entity) {
+	if d.Entities == nil {
+		d.Entities = make(map[int]*Entity)
+	}
+	d.Entities[e.ID] = &e
+}
+
+func (d *Delta) nullEntity(id int) {
+	if d.Entities == nil {
+		d.Entities = make(map[int]*Entity)
+	}
+	d.Entities[id] = nil
+}
+
+func (d *Delta) addPlayer(name string, id int) {
+	if d.Players == nil {
+		d.Players = make(map[string]*int)
+	}
+	d.Players[name] = &id
+}
+
+func (d *Delta) nullPlayer(name string) {
+	if d.Players == nil {
+		d.Players = make(map[string]*int)
+	}
+	d.Players[name] = nil
+}
+
+func (d Delta) IsEmpty() bool {
+	return d.RoomSize == nil && len(d.Entities) == 0 && len(d.Players) == 0
+}
+
 func init() {
 	Register(func() Value { return new(Frame) })
 }