# set_follow.ludic - moving between states: a `when` edge out of the current state that answers
# true, else the state the code asked for, faded by the edge between them or the target's own blend
function as_follow(pl: AnimPlayer) -> void {
  pl.fresh = false
  let s = AnimSets[pl.set]
  var to = pl.want
  var blend = -1.0
  if s.transitions != null {
    for i in 0 .. len(s.transitions) {
      let tr = s.transitions[i]
      if tr.when == null or not as_leaves(s, tr, pl.state) { continue }
      if tr.when() {
        to = as_state(s, tr.to)
        blend = tr.blend
        break
      }
    }
  }
  if to < 0 or to == pl.state { return }
  if blend < 0.0 { blend = as_blend(s, pl.state, to) }
  pl.state = to
  pl.want = to
  pl.fresh = true
  pl.fade_next = blend
}

function as_leaves(s: AnimSet, tr: AnimTransition, from: int) -> bool {
  return tr.from == "*" or tr.from == s.states[from].key
}

# the edge the code's request crosses, if the graph has one; else the target's own fade
function as_blend(s: AnimSet, from: int, to: int) -> float {
  if s.transitions != null {
    for i in 0 .. len(s.transitions) {
      let tr = s.transitions[i]
      if tr.when == null and tr.via == "" and tr.to == s.states[to].key and as_leaves(s, tr, from) { return tr.blend }
    }
  }
  return s.states[to].blend
}