# rail.ludic - the rail: once a pass (a second by default) the most urgent true cards, up to a few,
# muted ones left out; in a tie the registry's order decides
export state HintsState {
  hn_mute: []bool = hn_mutes()
  hn_foreign: []string = new []string      # muted keys with no card in this build, written back as read
  hn_shown: int = 3            # how many the rail holds
  hn_every: float = 1.0        # seconds between passes
  hn_top: []int = hn_slots(3)  # the cards on the rail this pass
  hn_n: int = 0
  hn_t: float = 0.0            # seconds to the next pass
  hn_pick: int = 0             # which chip the key would open
  hn_card: int = -1            # the card being read, or -1
  hn_facts: Queue<HintsFact> = hn_facts__new()
}

export function hints_facts(hints_st: HintsState) -> Queue<HintsFact> {
  return hints_st.hn_facts
}

function hn_fact(hints_st: HintsState, what: int, card: int) -> void {
  var f = q_rec(hints_facts(hints_st))
  if f == null {
    @alloc_ok("past the ring: more of these in a frame than its records, then kept in it")
    f = new HintsFact
    q_ring_add(hints_facts(hints_st), f)
  }
  f.what = what
  f.card = card
  q_push(hints_facts(hints_st), f)
}

# how many the rail holds and how often it is sorted
export function hints_config(hints_st: mut HintsState, shown: int, every: float) -> void {
  hints_st.hn_shown = shown
  hints_st.hn_every = every
  hints_st.hn_top = hn_slots(shown)
}

# the next pass comes on the next tick rather than in a second
export function hints_refresh(hints_st: mut HintsState) -> void { hints_st.hn_t = 0.0 }

export function hints_tick(hints_st: mut HintsState, dt: float) -> void {
  hints_st.hn_t = hints_st.hn_t - dt
  if hints_st.hn_t > 0.0 { return }
  hints_st.hn_t = hints_st.hn_every
  hints_sort(hints_st)
}

# one pass now: the rail re-sorted, the pick kept in range, and the card following its subject
# along the rail - or put down when what it was about stopped being true
export function hints_sort(hints_st: mut HintsState) -> void {
  hints_st.hn_n = 0
  let on = HintsWorld.showing()
  for u in 0 .. 4 {
    let want = HINTS_URGENT - u
    for id in 0 .. HINT_COUNT {
      if not on or hints_st.hn_n >= hints_st.hn_shown { break }
      if Hints[id].urgency != want or hints_muted(hints_st, id) { continue }
      if not HintsWorld.true_now(id) { continue }
      hints_st.hn_top[hints_st.hn_n] = id
      hints_st.hn_n += 1
    }
  }
  if hints_st.hn_pick >= hints_st.hn_n { hints_st.hn_pick = 0 }
  if hints_st.hn_card < 0 { return }
  if not on or hints_muted(hints_st, hints_st.hn_card) or not HintsWorld.true_now(hints_st.hn_card) {
    hints_st.hn_card = -1
    return
  }
  for k in 0 .. hints_st.hn_n { if hints_st.hn_top[k] == hints_st.hn_card { hints_st.hn_pick = k } }
}

# the cards on the rail, most urgent first (empty while the rail is not showing)
export function hints_rail(hints_st: HintsState) -> []int {
  let out = new []int
  if not HintsWorld.showing() { return out }
  for k in 0 .. hints_st.hn_n { push(out, hints_st.hn_top[k]) }
  return out
}

export function hints_count(hints_st: HintsState) -> int { return hints_st.hn_n }

export function hints_at(hints_st: HintsState, k: int) -> int {
  if k < 0 or k >= hints_st.hn_n { return -1 }
  return hints_st.hn_top[k]
}

export function hints_pick(hints_st: HintsState) -> int { return hints_st.hn_pick }

export function hints_hot(hints_st: HintsState, k: int) -> bool { return k == hints_st.hn_pick }

export function hints_reset(hints_st: mut HintsState) -> void {
  hn_empty(hints_st)
  hints_st.hn_n = 0
  hints_st.hn_t = 0.0
  hints_st.hn_pick = 0
  hints_st.hn_card = -1
  q_clear(hints_facts(hints_st))
}
function hn_facts__new() -> Queue<HintsFact> { return queue_new("hints.facts") }