// Compute an entity's new position.
// Returns an EntityDiff if the entity has changed, nil otherwise.
func (m *Mover) UpdateEntity(ent *entity.Entity, now message.AbsoluteTick) (req *entity.UpdateRequest, collidesWith interface{}) {
// TODO: remove Mover.lastUpdates?
var last message.AbsoluteTick
var ok bool
if last, ok = m.lastUpdates[ent.Id]; !ok {
last = now
}
m.lastUpdates[ent.Id] = now
dt := time.Duration(now-last) * clock.TickDuration // Convert to seconds
if dt == 0 {
return
}
if dt < 0 {
return // TODO: figure out if it's the right thing to do here
}
speed := ent.Speed
pos := ent.Position
nextPos := speed.GetNextPosition(pos, dt)
if nextPos == nil {
return
}
// Check terrain
// TODO: use brensenham algorithm
// See http://tech-algorithm.com/articles/drawing-line-using-bresenham-algorithm/
route := terrain.GetRouteBetween(pos, nextPos)
stoppedAt, collidesWith := checkRoute(route, ent, m.engine.ctx.Terrain, m.engine.ctx.Entity.List())
if stoppedAt != nil {
// The entity has been stopped while moving
nextPos = stoppedAt
}
newEnt := entity.New()
newEnt.Id = ent.Id
newEnt.Position = nextPos
diff := &message.EntityDiff{Position: true}
req = entity.NewUpdateRequest(now, newEnt, diff)
return
}
func (e *Engine) moveEntities(t message.AbsoluteTick) {
for _, ent := range e.entity.List() {
req, collidesWith := e.mover.UpdateEntity(ent, t)
// [GAME-SPECIFIC] Destroy balls when they collide
if collidesWith != nil && ent.Type == game.BallEntity {
req := entity.NewDeleteRequest(t, ent.Id)
if err := e.entity.AcceptRequest(req); err != nil {
panic(err) // This shouldn't happen
}
// If the ball collides with a player, decrease his health
if collidesWith, ok := collidesWith.(*message.Entity); ok && collidesWith.Type == game.PlayerEntity {
sender := ent.Attributes[game.SenderAttr].(message.EntityId)
if sender != collidesWith.Id {
health := collidesWith.Attributes[game.HealthAttr].(game.Health)
updated := entity.New()
updated.Attributes[game.HealthAttr] = health - 1
diff := message.NewEntityDiff()
diff.Attributes = true
req := entity.NewUpdateRequest(t, updated, diff)
if err := e.entity.AcceptRequest(req); err != nil {
panic(err) // This shouldn't happen
}
}
}
continue
}
if req != nil {
// Let's assume mover already did all security checks
if err := e.entity.AcceptRequest(req); err != nil {
// This should not fail
panic(err)
}
}
}
}