# text_ring.ludic - a fixed ring of text buffers written in place: a line made per event (a notice)
# takes the next slot, so a game shows as many as it has slots and allocates nothing after the ring
# is made. What a slot hands out is good until the ring comes round to it again - size the ring to
# what can be showing at once
export property TextRing {
  slots: []pointer = new []pointer
  cap: int = 0
  at: int = 0
}

export function tr_new(n: int, cap: int) -> TextRing {
  let r = new TextRing
  r.cap = Math.max(cap, 2)
  for i in 0 .. Math.max(n, 1) {
    var p: pointer = null
    unsafe { p = bytes(r.cap) }
    push(r.slots, p)
  }
  return r
}

# the buffer's text in the ring's next slot, cut to the slot's size, as a string
export function tr_put(r: TextRing, sb: StrBuf) -> string {
  let p = r.slots[r.at]
  r.at = (r.at + 1) % len(r.slots)
  let n = Math.min(sb.n, r.cap - 1)
  unsafe {
    for i in 0 .. n { p[i] = sb.b[i] }
    p[n] = 0
  }
  return p
}

export function tr_slots(r: TextRing) -> int { return len(r.slots) }