# order.ludic - the roll's order and its pages. Forty frames is a pile in taking order; once a frame
# has a grade the useful question is which are the best. The index is mapped, never the roll resorted.
export const PHOTO_NEWEST: int = 0
export const PHOTO_BEST: int = 1
export const PHOTO_BY_SUBJECT: int = 2
export const PHOTO_PAGE: int = 8


export function photo_sort(photo_st: PhotoState) -> int { return photo_st.pht_sort }
export function photo_sort_next(photo_st: mut PhotoState) -> void { photo_st.pht_sort = (photo_st.pht_sort + 1) % 3 }
export function photo_sort_set(photo_st: mut PhotoState, s: int) -> void { photo_st.pht_sort = Math.clamp(s, 0, 2) }

# the roll in the chosen order: newest first, best first, or by subject
export function photo_order(photo_st: mut PhotoState) -> []int {
  List.clear(photo_st.pht_order)
  for i in 0 .. photo_st.pht_n { push(photo_st.pht_order, i) }
  if photo_st.pht_sort == PHOTO_NEWEST {
    for i in 0 .. photo_st.pht_n { photo_st.pht_order[i] = photo_st.pht_n - 1 - i }
    return photo_st.pht_order
  }
  for i in 0 .. photo_st.pht_n {
    var best = i
    for k in i + 1 .. photo_st.pht_n { if pht_before(photo_st, photo_st.pht_order[k], photo_st.pht_order[best]) { best = k } }
    let t = photo_st.pht_order[i]
    photo_st.pht_order[i] = photo_st.pht_order[best]
    photo_st.pht_order[best] = t
  }
  return photo_st.pht_order
}

function pht_before(photo_st: PhotoState, a: int, b: int) -> bool {
  if photo_st.pht_sort == PHOTO_BEST { return photo_st.pht_grade[a] > photo_st.pht_grade[b] }
  return photo_st.pht_mask[a] < photo_st.pht_mask[b]
}

export function photo_pages(photo_st: PhotoState) -> int { return (photo_st.pht_n + PHOTO_PAGE - 1) / PHOTO_PAGE }
export function photo_page_now(photo_st: PhotoState) -> int { return photo_st.pht_page }
export function photo_page_step(photo_st: mut PhotoState, d: int) -> void { photo_st.pht_page = Math.clamp(photo_st.pht_page + d, 0, Math.max(photo_pages(photo_st) - 1, 0)) }

# a page of the roll, in its order; the page is held inside the roll
export function photo_page_list(photo_st: mut PhotoState) -> []int {
  let out = photo_st.pht_page_out
  List.clear(out)
  if photo_st.pht_n == 0 { return out }
  let order = photo_order(photo_st)
  if photo_st.pht_page >= photo_pages(photo_st) { photo_st.pht_page = photo_pages(photo_st) - 1 }
  for k in 0 .. PHOTO_PAGE {
    let oi = photo_st.pht_page * PHOTO_PAGE + k
    if oi < photo_st.pht_n { push(photo_st.pht_page_out, order[oi]) }
  }
  return out
}