# run.ludic - the sky moving on. Only the machine that owns the world runs the spells; every
# machine eases the ground's wetness and makes its own lightning out of a storm it is told of.
function wx_turn(weather_st: mut WeatherState) -> void {
  let was = weather_st.wx_state
  weather_st.wx_state = weather_st.wx_next
  weather_st.wx_next = wx_pick_next(weather_st, weather_st.wx_state)
  weather_st.wx_left = wx_spell_hours(weather_st, weather_st.wx_state)
  if weather_st.wx_forced {
    weather_st.wx_forced = false
    let least = Math.max(5.0, WeatherWorld.front_hours())
    if weather_st.wx_left < least { weather_st.wx_left = least }
  }
  if weather_st.wx_state == was { return }
  # a front going through and leaving clear sky behind it: the light people get up for
  if weather_st.wx_kinds[weather_st.wx_state].clear and weather_st.wx_kinds[was].wet and not wx_night() {
    weather_st.wx_clear_t = 0.6
    wx_fact(weather_st, WEATHER_CLEARED, weather_st.wx_state, was)
  }
  wx_fact(weather_st, WEATHER_BEGAN, weather_st.wx_state, was)
}

function wx_wind_tick(weather_st: mut WeatherState, dt: float) -> void {
  let kd = weather_st.wx_kinds[weather_st.wx_state]
  weather_st.wx_wind = weather_st.wx_wind + (kd.wind - weather_st.wx_wind) * Math.min(1.0, dt * 0.3)
  var want = kd.wind_dir
  if want < 0.0 {
    let h = wx_hours()
    want = weather_st.wx_down_dir
    if h > weather_st.wx_up_from and h < weather_st.wx_up_to { want = weather_st.wx_up_dir }
  }
  let r = dt * 0.12
  weather_st.wx_dir = wx_wrap(weather_st.wx_dir + Math.clamp(wx_wrap(want - weather_st.wx_dir), -r, r))
}

# the spells: the story's lean, the clock running down, the edges eased, the wind
function wx_spells(weather_st: mut WeatherState, dt: float, gh: float) -> void {
  wx_apply_bias(weather_st)
  weather_st.wx_left = weather_st.wx_left - gh
  if weather_st.wx_left < 0.0 { wx_turn(weather_st) }
  var want = 1.0
  if weather_st.wx_kinds[weather_st.wx_state].clear { want = 0.0 }
  if weather_st.wx_left < 0.5 and weather_st.wx_kinds[weather_st.wx_next].clear { want = 0.0 }
  weather_st.wx_amount = weather_st.wx_amount + (want - weather_st.wx_amount) * Math.min(1.0, dt * 0.5)
  wx_wind_tick(weather_st, dt)
  if weather_st.wx_clear_t > 0.0 { weather_st.wx_clear_t = weather_st.wx_clear_t - gh }
}

# soaking is faster than drying: a downpour wets the ground in under a minute, and it takes
# several to give it back
function wx_ground_tick(weather_st: mut WeatherState, dt: float) -> void {
  let want = weather_st.wx_kinds[weather_st.wx_state].soak * weather_st.wx_amount
  var k = dt * 0.10
  if want < weather_st.wx_ground { k = dt * 0.020 }
  weather_st.wx_ground = weather_st.wx_ground + (want - weather_st.wx_ground) * Math.clamp(k, 0.0, 1.0)
}

function wx_storm_tick(weather_st: mut WeatherState, dt: float) -> void {
  weather_st.wx_flash = weather_st.wx_flash * Math.max(0.0, 1.0 - dt * 9.0)
  if not weather_st.wx_kinds[weather_st.wx_state].thunder or weather_st.wx_amount < 0.5 { return }
  weather_st.wx_thunder_t = weather_st.wx_thunder_t - dt
  if weather_st.wx_thunder_t < 0.0 {
    weather_st.wx_thunder_t = rng_span(weather_st.wx_dice, 9.0, 34.0)
    weather_st.wx_flash = 1.0
    wx_fact(weather_st, WEATHER_THUNDER, weather_st.wx_state, weather_st.wx_state)
  }
}

# one step: `dt` real seconds and `gh` game hours
export function weather_run(weather_st: mut WeatherState, dt: float, gh: float) -> void {
  if weather_kind_count(weather_st) == 0 { return }
  if wx_owns() { wx_spells(weather_st, dt, gh) }
  wx_ground_tick(weather_st, dt)
  wx_storm_tick(weather_st, dt)
  if weather_wet(weather_st) { weather_st.wx_wet_today = true }
}