#!/usr/bin/env bash
# Weather from met.no for the IP-geolocated position.  The last result is
# cached on disk, so re-opening the panel is instant and offline-safe; the
# network is hit at most every 10 minutes.

fallback='{"temp":0,"feelslike":0,"humidity":0,"wind":0,"desc":"Unavailable","icon":"󰖐","city":""}'
cache_dir=${XDG_CACHE_HOME:-$HOME/.cache}/eww
loc_cache=$cache_dir/weather-location.json
wx_cache=$cache_dir/weather.json
interval=600
ua="eww-bar/1.0 cedric.hoelzl@gmail.com"
mkdir -p "$cache_dir"

fresh() { [[ -s $1 ]] && [[ -n $(find "$1" -mmin "-$2" 2>/dev/null) ]]; } # FILE MINUTES

location() {
  fresh "$loc_cache" 60 && { cat "$loc_cache"; return; }
  local data
  if data=$(curl -sf --max-time 5 "http://ip-api.com/json?fields=lat,lon,city"); then
    printf '%s' "$data" | tee "$loc_cache"
  elif [[ -s $loc_cache ]]; then
    cat "$loc_cache"
  else
    return 1
  fi
}

icon_for() {
  case $1 in
    *thunder*) echo "󰖔" ;;
    *snow* | *sleet*) echo "󰖘" ;;
    heavyrain*) echo "󰖖" ;;
    *rain* | *shower*) echo "󰖗" ;;
    fog*) echo "󰖑" ;;
    cloudy*) echo "󰖐" ;;
    partlycloudy*) echo "󰖕" ;;
    fair* | clearsky*) echo "󰖙" ;;
    *) echo "󰖐" ;;
  esac
}

desc_for() {
  local c=$1
  c=${c%_day}; c=${c%_night}; c=${c%_polartwilight}
  case $c in
    clearsky) echo "Clear sky" ;;
    fair) echo "Fair" ;;
    partlycloudy) echo "Partly cloudy" ;;
    cloudy) echo "Cloudy" ;;
    fog) echo "Foggy" ;;
    lightrain) echo "Light rain" ;;
    rain) echo "Rain" ;;
    heavyrain) echo "Heavy rain" ;;
    lightrainshowers) echo "Light showers" ;;
    rainshowers) echo "Rain showers" ;;
    heavyrainshowers) echo "Heavy showers" ;;
    lightrainandthunder) echo "Light rain & thunder" ;;
    rainandthunder) echo "Rain & thunder" ;;
    heavyrainandthunder) echo "Heavy rain & thunder" ;;
    *showersandthunder) echo "Showers & thunder" ;;
    lightsleet | lightsleetshowers) echo "Light sleet" ;;
    sleet | sleetshowers) echo "Sleet" ;;
    heavysleet | heavysleetshowers) echo "Heavy sleet" ;;
    *sleetandthunder) echo "Sleet & thunder" ;;
    lightsnow | lightsnowshowers) echo "Light snow" ;;
    snow | snowshowers) echo "Snow" ;;
    heavysnow | heavysnowshowers) echo "Heavy snow" ;;
    *snowandthunder) echo "Snow & thunder" ;;
    *) echo "$c" ;;
  esac
}

fetch() {
  local loc lat lon city data temp humidity wind code feelslike
  loc=$(location) || return 1
  read -r lat lon city < <(jq -r '"\(.lat) \(.lon) \(.city)"' <<<"$loc")
  data=$(curl -sf --max-time 8 -H "User-Agent: $ua" -H "Accept: application/json" \
    "https://api.met.no/weatherapi/locationforecast/2.0/compact?lat=$lat&lon=$lon") || return 1
  read -r temp humidity wind code < <(jq -r '
    .properties.timeseries[0].data
    | "\(.instant.details.air_temperature | round) \(.instant.details.relative_humidity | round) \(.instant.details.wind_speed * 3.6 | floor) \(.next_1_hours.summary.symbol_code // .next_6_hours.summary.symbol_code // "cloudy")"' <<<"$data")
  [[ -n $temp ]] || return 1
  # Apparent temperature: wind chill below 10 °C, otherwise the air temperature.
  feelslike=$(awk -v t="$temp" -v v="$wind" 'BEGIN {
    if (v > 4.8 && t < 10) printf "%d", 13.12 + 0.6215 * t - 11.37 * (v ^ 0.16) + 0.3965 * t * (v ^ 0.16)
    else printf "%d", t }')
  printf '{"temp":%s,"feelslike":%s,"humidity":%s,"wind":%s,"desc":"%s","icon":"%s","city":"%s"}' \
    "$temp" "$feelslike" "$humidity" "$wind" "$(desc_for "$code")" "$(icon_for "$code")" "$(jstr "$city")"
}

refresh() {
  local out
  if fresh "$wx_cache" $((interval / 60)); then
    emit "$(cat "$wx_cache")"
  elif out=$(fetch); then
    printf '%s\n' "$out" >"$wx_cache"
    emit "$out"
  elif [[ -s $wx_cache ]]; then
    emit "$(cat "$wx_cache")"
  else
    emit "$fallback"
  fi
}

refresh
while sleep "$interval"; do refresh; done