# pick.ludic - the next spell, drawn from weights, and how long one lasts. The weights are the
# kind's own unless the world leans on them (a season, a wet week); every draw is this package's
function wx_odds(from: int) -> []float {
  return WeatherWorld.odds(from)
}

# the kind a set of weights lands on; no weights (or all zero) keeps the kind it came from
export function weather_draw_from(w: []float, from: int, roll: float) -> int {
  if w == null { return from }
  var total = 0.0
  for k in 0 .. len(w) { if w[k] > 0.0 { total = total + w[k] } }
  if not (total > 0.0) { return from }
  var at = roll * total
  for k in 0 .. len(w) {
    if w[k] > 0.0 {
      if at < w[k] { return k }
      at = at - w[k]
    }
  }
  return len(w) - 1
}

function wx_pick_next(weather_st: WeatherState, from: int) -> int {
  return weather_draw_from(wx_odds(from), from, rng_float(weather_st.wx_dice))
}

function wx_spell_hours(weather_st: WeatherState, k: int) -> float {
  let kd = weather_st.wx_kinds[k]
  return rng_span(weather_st.wx_dice, kd.spell_lo, kd.spell_hi)
}