Garden watering that skips the run when it rains

1// Rain-aware watering: runs the garden valve on your days, and skips the run2// when it has rained or rain is on the way. Uses the free Open-Meteo forecast.3 4let CONFIG = {5  latitude: -37.81,6  longitude: 144.96,7  waterAt: "06:00",8  waterDays: "Mon,Wed,Fri",9  runMin: 20,10  skipIfRainedMm: 5,11  skipIfForecastMm: 3,12  skipIfChancePct: 70,13  waterIfNoForecast: true,14  switchId: 0,15};16 17// Check the clock every 20 seconds, so the run starts within the minute set.18let CHECK_EVERY_SEC = 20;19// If the forecast doesn't come back, ask once more two minutes later.20let RETRY_SEC = 120;21let DAY_NAMES = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"];22 23let lastRunDate = -1;24let retried = false;25 26// Local date (days since 1970), weekday and "HH:MM", or null before the27// clock has synced.28function localNow() {29  let s = Shelly.getComponentStatus("sys");30  if (s === null || typeof s.unixtime !== "number" || s.time === null) return null;31  let date = Math.floor((s.unixtime + (s.utc_offset || 0)) / 86400);32  // 1 January 1970 was a Thursday.33  return { date: date, weekday: DAY_NAMES[(date + 4) % 7], time: s.time };34}35 36function forecastUrl() {37  // past_days=1 adds yesterday's rain as the first value, today's is second.38  return "https://api.open-meteo.com/v1/forecast?latitude=" + CONFIG.latitude +39    "&longitude=" + CONFIG.longitude +40    "&daily=precipitation_sum,precipitation_probability_max" +41    "&timezone=auto&past_days=1&forecast_days=1";42}43 44function water(reason) {45  print("Watering for " + CONFIG.runMin + " min. " + reason);46  // The relay switches itself off after runMin, so the valve can't be left47  // open if the script stops or the Shelly loses Wi-Fi mid-run.48  Shelly.call("Switch.Set", {49    id: CONFIG.switchId,50    on: true,51    toggle_after: CONFIG.runMin * 60,52  });53}54 55function noForecast(why) {56  if (!retried) {57    retried = true;58    print("Couldn't get the forecast (" + why + "). Trying again in 2 min.");59    Timer.set(RETRY_SEC * 1000, false, fetchForecast);60    return;61  }62  if (CONFIG.waterIfNoForecast) water("No forecast, so watering as scheduled.");63  else print("No forecast, so skipping today's watering.");64}65 66function onForecast(res, err) {67  if (err !== 0 || res.code !== 200) return noForecast("error " + (err !== 0 ? err : res.code));68  let d = null;69  try {70    d = JSON.parse(res.body).daily;71  } catch (e) {72    return noForecast("unreadable reply");73  }74  let rained = d.precipitation_sum[0] || 0;75  let coming = d.precipitation_sum[1] || 0;76  let chance = d.precipitation_probability_max[1] || 0;77  let weather = "Rain yesterday " + rained + " mm, today " + coming + " mm forecast (" +78    chance + "% chance).";79  if (rained >= CONFIG.skipIfRainedMm || coming >= CONFIG.skipIfForecastMm ||80      chance >= CONFIG.skipIfChancePct) {81    print("Skipping today's watering. " + weather);82    return;83  }84  water(weather);85}86 87function fetchForecast() {88  Shelly.call("HTTP.GET", { url: forecastUrl(), timeout: 15 }, onForecast);89}90 91function check() {92  let now = localNow();93  // Without the clock it can't tell the day or the time, so it does nothing.94  if (now === null) return;95  if (now.time !== CONFIG.waterAt || now.date === lastRunDate) return;96  if (CONFIG.waterDays.indexOf(now.weekday) === -1) return;97  lastRunDate = now.date;98  retried = false;99  fetchForecast();100}101 102Timer.set(CHECK_EVERY_SEC * 1000, true, check);103print("Rain-aware watering started. Next run at " + CONFIG.waterAt + " on " +104  CONFIG.waterDays + ".");