# leave.ludic - a print put down. Each kind is a ring: past its cap the oldest is written over, and
# a slot written over is a new print, unread
function tk_ok(tracks_st: TracksState, kind: int) -> bool { return tracks_st.tk_ring != null and kind >= 0 and kind < tracks_st.tk_kinds }

# a print made at `made` game hours (another machine's, arriving here); the ring index, or -1
export function tracks_leave_at(tracks_st: mut TracksState, kind: int, x: float, z: float, yaw: float, sp: int, legend: bool, maker: int, made: float) -> int {
  if not tk_ok(tracks_st, kind) { return -1 }
  var i = tracks_st.tk_next[kind]
  if tracks_st.tk_count[kind] < tracks_st.tk_cap {
    i = tracks_st.tk_count[kind]
    tracks_st.tk_count[kind] = tracks_st.tk_count[kind] + 1
  }
  tracks_st.tk_next[kind] = (i + 1) % tracks_st.tk_cap
  let t = tracks_st.tk_ring[kind * tracks_st.tk_cap + i]
  t.x = x
  t.z = z
  t.yaw = yaw
  t.sp = sp
  t.legend = legend
  t.maker = maker
  t.made = made
  t.read = false
  TracksWorld.placed(kind, i)
  return i
}

export function tracks_leave(tracks_st: mut TracksState, kind: int, x: float, z: float, yaw: float, sp: int, legend: bool, maker: int) -> int {
  return tracks_leave_at(tracks_st, kind, x, z, yaw, sp, legend, maker, tk_now())
}

# the ground forgets every print (a new world)
export function tracks_clear(tracks_st: mut TracksState) -> void {
  if tracks_st.tk_ring == null { return }
  for k in 0 .. tracks_st.tk_kinds {
    tracks_st.tk_count[k] = 0
    tracks_st.tk_next[k] = 0
  }
  tracks_st.tk_chain = -1
}