feat(van-weather): port weather service to Rust

Add a Rust implementation with privacy-masked locations, HTTP retries,
and Home Assistant sensor publishing. Package it with Nix and switch the
systemd service from Python to the compiled binary.

Cargo.toml

@@ -0,0 +1,4 @@
+[workspace]
+resolver = "2"
+
+members = ["rust/*"]

rust/van_weather/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "van-weather"
+version = "0.1.0"
+edition = "2024"
+description = "Fetch privacy-masked weather for a van and publish it to Home Assistant"
+license = "MIT"
+
+[dependencies]
+anyhow = "1.0"
+chrono = "0.4"
+clap = { version = "4.5", features = ["derive", "env"] }
+env_logger = "0.11"
+log = "0.4"
+reqwest = { version = "0.12", default-features = false, features = ["blocking", "json", "rustls-tls"] }
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+
+[lints.clippy]
+all = "deny"
+pedantic = "deny"
+

rust/van_weather/package.nix

@@ -0,0 +1,13 @@
+{ rustPlatform }:
+rustPlatform.buildRustPackage {
+  pname = "van-weather";
+  version = "0.1.0";
+  src = ./.;
+
+  cargoLock.lockFile = ./Cargo.lock;
+
+  meta = {
+    description = "Privacy-masked van weather publisher for Home Assistant";
+    mainProgram = "van-weather";
+  };
+}

rust/van_weather/src/main.rs

@@ -0,0 +1,565 @@
+use std::{thread, time::Duration};
+
+use anyhow::{Context, Result, bail};
+use chrono::{DateTime, Utc};
+use clap::Parser;
+use log::{error, info};
+use reqwest::{
+    StatusCode, Url,
+    blocking::{Client, ClientBuilder},
+    header::{AUTHORIZATION, HeaderMap, HeaderValue},
+    retry,
+};
+use serde::Deserialize;
+use serde_json::{Value, json};
+
+const LAT_ENTITY: &str = "sensor.van_last_known_latitude";
+const LON_ENTITY: &str = "sensor.van_last_known_longitude";
+const PIRATE_WEATHER_HOST: &str = "api.pirateweather.net";
+const MASK_DECIMALS: u32 = 1;
+const MASK_FACTOR: f64 = decimal_factor(MASK_DECIMALS);
+const RETRIES_PER_REQUEST: u32 = 2;
+
+const fn decimal_factor(decimals: u32) -> f64 {
+    let mut factor = 1.0;
+    let mut remaining = decimals;
+    while remaining > 0 {
+        factor *= 10.0;
+        remaining -= 1;
+    }
+    factor
+}
+
+#[derive(Debug, Parser)]
+#[command(about, version)]
+struct Args {
+    #[arg(long, env = "HA_URL")]
+    ha_url: String,
+
+    #[arg(long, env = "HA_TOKEN", hide_env_values = true)]
+    ha_token: String,
+
+    #[arg(long, env = "PIRATE_WEATHER_API_KEY", hide_env_values = true)]
+    pirate_weather_api_key: String,
+
+    #[arg(
+        long,
+        default_value_t = 900,
+        value_parser = clap::value_parser!(u64).range(1..)
+    )]
+    interval: u64,
+
+    #[arg(long, default_value = "info", env = "RUST_LOG")]
+    log_level: String,
+}
+
+#[derive(Debug, Deserialize)]
+struct HaState {
+    state: String,
+}
+
+#[derive(Debug)]
+struct HttpClients {
+    home_assistant: Client,
+    pirate_weather: Client,
+}
+
+#[derive(Debug, Default, Deserialize)]
+struct ApiResponse {
+    #[serde(default)]
+    currently: CurrentWeather,
+    #[serde(default)]
+    daily: ForecastBlock<DailyApiForecast>,
+    #[serde(default)]
+    hourly: ForecastBlock<HourlyApiForecast>,
+}
+
+#[derive(Debug, Default, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct CurrentWeather {
+    temperature: Option<f64>,
+    apparent_temperature: Option<f64>,
+    humidity: Option<f64>,
+    wind_speed: Option<f64>,
+    wind_bearing: Option<f64>,
+    icon: Option<String>,
+    pressure: Option<f64>,
+    visibility: Option<f64>,
+    uv_index: Option<f64>,
+    ozone: Option<f64>,
+    nearest_storm_distance: Option<f64>,
+    nearest_storm_bearing: Option<f64>,
+    precip_probability: Option<f64>,
+    cloud_cover: Option<f64>,
+}
+
+#[derive(Debug, Deserialize)]
+struct ForecastBlock<T> {
+    #[serde(default)]
+    data: Vec<T>,
+}
+
+impl<T> Default for ForecastBlock<T> {
+    fn default() -> Self {
+        Self { data: Vec::new() }
+    }
+}
+
+#[derive(Debug, Default, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct DailyApiForecast {
+    time: Option<i64>,
+    icon: Option<String>,
+    temperature_high: Option<f64>,
+    temperature_low: Option<f64>,
+    precip_probability: Option<f64>,
+}
+
+#[derive(Debug, Default, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct HourlyApiForecast {
+    time: Option<i64>,
+    icon: Option<String>,
+    temperature: Option<f64>,
+    precip_probability: Option<f64>,
+}
+
+#[derive(Debug)]
+struct Weather {
+    current: CurrentWeather,
+    daily: Vec<DailyForecast>,
+    hourly: Vec<HourlyForecast>,
+}
+
+#[derive(Debug)]
+struct DailyForecast {
+    datetime: DateTime<Utc>,
+    condition: &'static str,
+    temperature: Option<f64>,
+    templow: Option<f64>,
+    precipitation_probability: Option<f64>,
+}
+
+#[derive(Debug)]
+struct HourlyForecast {
+    datetime: DateTime<Utc>,
+    condition: &'static str,
+    temperature: Option<f64>,
+    precipitation_probability: Option<f64>,
+}
+
+fn main() -> Result<()> {
+    let Args {
+        ha_url,
+        ha_token,
+        pirate_weather_api_key,
+        interval,
+        log_level,
+    } = Args::parse();
+    env_logger::Builder::from_env(env_logger::Env::default().default_filter_or(log_level.as_str()))
+        .init();
+
+    let ha_url = ha_url.trim_end_matches('/').to_owned();
+    let ha_host = Url::parse(&ha_url)
+        .context("HA_URL is not a valid URL")?
+        .host_str()
+        .context("HA_URL has no host")?
+        .to_owned();
+    let clients = HttpClients {
+        home_assistant: build_client(&ha_host, Some(&ha_token))?,
+        pirate_weather: build_client(PIRATE_WEATHER_HOST, None)?,
+    };
+
+    info!("Starting van weather service, polling every {interval}s");
+    loop {
+        if let Err(err) = update_weather(&clients, &ha_url, &pirate_weather_api_key) {
+            error!("Weather update failed: {err:#}");
+        }
+        thread::sleep(Duration::from_secs(interval));
+    }
+}
+
+fn build_client(host: &str, bearer_token: Option<&str>) -> Result<Client> {
+    let policy = retry::for_host(host.to_owned())
+        .max_retries_per_request(RETRIES_PER_REQUEST)
+        .classify_fn(|request| {
+            let retryable = request.error().is_some()
+                || request.status().is_some_and(|status| {
+                    status == StatusCode::REQUEST_TIMEOUT
+                        || status == StatusCode::TOO_MANY_REQUESTS
+                        || status.is_server_error()
+                });
+            if retryable {
+                request.retryable()
+            } else {
+                request.success()
+            }
+        });
+
+    let mut builder = ClientBuilder::new()
+        .timeout(Duration::from_secs(30))
+        .retry(policy);
+
+    if let Some(token) = bearer_token {
+        let mut authorization = HeaderValue::from_str(&format!("Bearer {token}"))
+            .context("HA_TOKEN contains invalid header characters")?;
+        authorization.set_sensitive(true);
+        let mut headers = HeaderMap::new();
+        headers.insert(AUTHORIZATION, authorization);
+        builder = builder.default_headers(headers);
+    }
+
+    builder
+        .build()
+        .with_context(|| format!("failed to create HTTP client for {host}"))
+}
+
+fn update_weather(clients: &HttpClients, ha_url: &str, api_key: &str) -> Result<()> {
+    let lat = get_ha_state(&clients.home_assistant, ha_url, LAT_ENTITY)?;
+    let lon = get_ha_state(&clients.home_assistant, ha_url, LON_ENTITY)?;
+    let masked_lat = mask_coordinate(lat);
+    let masked_lon = mask_coordinate(lon);
+    info!("Masked location: {masked_lat}, {masked_lon}");
+
+    let weather = fetch_weather(&clients.pirate_weather, api_key, masked_lat, masked_lon)?;
+    info!(
+        "Weather: {}°F, {}",
+        weather
+            .current
+            .temperature
+            .map_or_else(|| "unknown".to_owned(), |value| value.to_string()),
+        condition(weather.current.icon.as_deref())
+    );
+    post_to_ha(&clients.home_assistant, ha_url, &weather)?;
+    info!("Posted weather to Home Assistant");
+    Ok(())
+}
+
+fn mask_coordinate(value: f64) -> f64 {
+    (value * MASK_FACTOR).round() / MASK_FACTOR
+}
+
+fn get_ha_state(client: &Client, ha_url: &str, entity_id: &str) -> Result<f64> {
+    let HaState { state } = client
+        .get(format!("{ha_url}/api/states/{entity_id}"))
+        .send()
+        .with_context(|| format!("request for {entity_id} failed"))?
+        .error_for_status()
+        .with_context(|| format!("Home Assistant rejected {entity_id} request"))?
+        .json()
+        .context("Home Assistant returned invalid JSON")?;
+
+    if matches!(state.as_str(), "unavailable" | "unknown") {
+        bail!("{entity_id} is {state}");
+    }
+
+    state
+        .parse::<f64>()
+        .with_context(|| format!("{entity_id} state is not numeric: {state}"))
+}
+
+fn fetch_weather(client: &Client, api_key: &str, lat: f64, lon: f64) -> Result<Weather> {
+    let response = client
+        .get(format!(
+            "https://{PIRATE_WEATHER_HOST}/forecast/{api_key}/{lat},{lon}"
+        ))
+        .query(&[("units", "us")])
+        .send()
+        .context("Pirate Weather request failed")?
+        .error_for_status()
+        .context("Pirate Weather rejected request")?;
+    let data = response
+        .json::<ApiResponse>()
+        .context("Pirate Weather returned invalid JSON")?;
+    Ok(parse_weather(data))
+}
+
+fn parse_weather(data: ApiResponse) -> Weather {
+    let daily = data
+        .daily
+        .data
+        .into_iter()
+        .take(8)
+        .filter_map(|day| {
+            timestamp(day.time).map(|datetime| DailyForecast {
+                datetime,
+                condition: condition(day.icon.as_deref()),
+                temperature: day.temperature_high,
+                templow: day.temperature_low,
+                precipitation_probability: day.precip_probability,
+            })
+        })
+        .collect();
+    let hourly = data
+        .hourly
+        .data
+        .into_iter()
+        .take(48)
+        .filter_map(|hour| {
+            timestamp(hour.time).map(|datetime| HourlyForecast {
+                datetime,
+                condition: condition(hour.icon.as_deref()),
+                temperature: hour.temperature,
+                precipitation_probability: hour.precip_probability,
+            })
+        })
+        .collect();
+    Weather {
+        current: data.currently,
+        daily,
+        hourly,
+    }
+}
+
+fn timestamp(value: Option<i64>) -> Option<DateTime<Utc>> {
+    value
+        .filter(|value| *value != 0)
+        .and_then(DateTime::from_timestamp_secs)
+}
+
+fn condition(icon: Option<&str>) -> &'static str {
+    match icon.unwrap_or_default() {
+        "clear-day" => "sunny",
+        "clear-night" => "clear-night",
+        "rain" => "rainy",
+        "snow" => "snowy",
+        "sleet" => "snowy-rainy",
+        "wind" => "windy",
+        "fog" => "fog",
+        "partly-cloudy-day" | "partly-cloudy-night" => "partlycloudy",
+        _ => "cloudy",
+    }
+}
+
+fn post_to_ha(client: &Client, ha_url: &str, weather: &Weather) -> Result<()> {
+    for (entity_id, payload) in weather_updates(weather) {
+        let response = client
+            .post(format!("{ha_url}/api/states/{entity_id}"))
+            .json(&payload)
+            .send()
+            .with_context(|| format!("failed to post {entity_id}"))?;
+        ensure_success(response.status(), &entity_id)?;
+    }
+    Ok(())
+}
+
+fn ensure_success(status: StatusCode, entity_id: &str) -> Result<()> {
+    if status.is_success() {
+        Ok(())
+    } else {
+        bail!("Home Assistant rejected {entity_id} update with {status}")
+    }
+}
+
+#[allow(clippy::too_many_lines)]
+fn weather_updates(weather: &Weather) -> Vec<(String, Value)> {
+    let current = &weather.current;
+    let mut updates = vec![
+        sensor(
+            "sensor.van_weather_condition",
+            Some(json!(condition(current.icon.as_deref()))),
+            json!({"friendly_name": "Van Weather Condition"}),
+        ),
+        sensor(
+            "sensor.van_weather_temperature",
+            current.temperature.map(|value| json!(value)),
+            json!({"unit_of_measurement": "°F", "device_class": "temperature"}),
+        ),
+        sensor(
+            "sensor.van_weather_apparent_temperature",
+            current.apparent_temperature.map(|value| json!(value)),
+            json!({"unit_of_measurement": "°F", "device_class": "temperature"}),
+        ),
+        sensor(
+            "sensor.van_weather_humidity",
+            Some(json!(percent(current.humidity))),
+            json!({"unit_of_measurement": "%", "device_class": "humidity"}),
+        ),
+        sensor(
+            "sensor.van_weather_pressure",
+            current.pressure.map(|value| json!(value)),
+            json!({"unit_of_measurement": "mbar", "device_class": "pressure"}),
+        ),
+        sensor(
+            "sensor.van_weather_wind_speed",
+            current.wind_speed.map(|value| json!(value)),
+            json!({"unit_of_measurement": "mph", "device_class": "wind_speed"}),
+        ),
+        sensor(
+            "sensor.van_weather_wind_bearing",
+            current.wind_bearing.map(|value| json!(value)),
+            json!({"unit_of_measurement": "°"}),
+        ),
+        sensor(
+            "sensor.van_weather_visibility",
+            current.visibility.map(|value| json!(value)),
+            json!({"unit_of_measurement": "mi"}),
+        ),
+        sensor(
+            "sensor.van_weather_uv_index",
+            current.uv_index.map(|value| json!(value)),
+            json!({"friendly_name": "Van Weather UV Index", "icon": "mdi:sun-wireless"}),
+        ),
+        sensor(
+            "sensor.van_weather_ozone",
+            current.ozone.map(|value| json!(value)),
+            json!({"unit_of_measurement": "DU", "icon": "mdi:earth"}),
+        ),
+        sensor(
+            "sensor.van_weather_nearest_storm_distance",
+            current.nearest_storm_distance.map(|value| json!(value)),
+            json!({"unit_of_measurement": "mi", "icon": "mdi:weather-lightning"}),
+        ),
+        sensor(
+            "sensor.van_weather_nearest_storm_bearing",
+            current.nearest_storm_bearing.map(|value| json!(value)),
+            json!({"unit_of_measurement": "°", "icon": "mdi:weather-lightning"}),
+        ),
+        sensor(
+            "sensor.van_weather_precip_probability",
+            Some(json!(percent(current.precip_probability))),
+            json!({"unit_of_measurement": "%", "icon": "mdi:weather-rainy"}),
+        ),
+        sensor(
+            "sensor.van_weather_cloud_cover",
+            Some(json!(percent(current.cloud_cover))),
+            json!({"unit_of_measurement": "%", "icon": "mdi:weather-cloudy"}),
+        ),
+    ]
+    .into_iter()
+    .flatten()
+    .collect::<Vec<_>>();
+
+    let daily = weather
+        .daily
+        .iter()
+        .map(|forecast| {
+            json!({
+                "datetime": forecast.datetime.to_rfc3339(),
+                "condition": forecast.condition,
+                "temperature": forecast.temperature,
+                "templow": forecast.templow,
+                "precipitation_probability": percent(forecast.precipitation_probability),
+            })
+        })
+        .collect::<Vec<_>>();
+    updates.push((
+        "sensor.van_weather_forecast_daily".to_owned(),
+        json!({"state": daily.len(), "attributes": {"forecast": daily}}),
+    ));
+
+    let hourly = weather
+        .hourly
+        .iter()
+        .map(|forecast| {
+            json!({
+                "datetime": forecast.datetime.to_rfc3339(),
+                "condition": forecast.condition,
+                "temperature": forecast.temperature,
+                "precipitation_probability": percent(forecast.precipitation_probability),
+            })
+        })
+        .collect::<Vec<_>>();
+    updates.push((
+        "sensor.van_weather_forecast_hourly".to_owned(),
+        json!({"state": hourly.len(), "attributes": {"forecast": hourly}}),
+    ));
+    updates
+}
+
+fn sensor(entity_id: &str, state: Option<Value>, attributes: Value) -> Option<(String, Value)> {
+    state.map(|state| {
+        let mut payload = serde_json::Map::new();
+        payload.insert("state".to_owned(), state);
+        payload.insert("attributes".to_owned(), attributes);
+        (entity_id.to_owned(), Value::Object(payload))
+    })
+}
+
+#[allow(clippy::cast_possible_truncation)]
+fn percent(value: Option<f64>) -> i64 {
+    // Preserve Python's int(probability * 100) behavior for Home Assistant.
+    (value.unwrap_or_default() * 100.0) as i64
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn maps_conditions_for_home_assistant() {
+        assert_eq!(condition(Some("clear-day")), "sunny");
+        assert_eq!(condition(Some("sleet")), "snowy-rainy");
+        assert_eq!(condition(Some("partly-cloudy-night")), "partlycloudy");
+        assert_eq!(condition(Some("unexpected")), "cloudy");
+        assert_eq!(condition(None), "cloudy");
+    }
+
+    #[test]
+    fn parses_api_response_and_builds_compatible_payloads() {
+        let response: ApiResponse = serde_json::from_value(json!({
+            "currently": {
+                "temperature": 72.5,
+                "humidity": 0.67,
+                "icon": "clear-day",
+                "precipProbability": 0.129,
+                "cloudCover": 0.4,
+                "summary": "Fine"
+            },
+            "daily": {"data": [{
+                "time": 1_700_000_000,
+                "icon": "rain",
+                "temperatureHigh": 75.0,
+                "temperatureLow": 52.0,
+                "precipProbability": 0.8
+            }]},
+            "hourly": {"data": [{
+                "time": 1_700_000_000,
+                "icon": "fog",
+                "temperature": 61.0,
+                "precipProbability": 0.05
+            }]}
+        }))
+        .unwrap();
+
+        let weather = parse_weather(response);
+        let updates = weather_updates(&weather);
+        let find = |id: &str| updates.iter().find(|(entity, _)| entity == id).unwrap();
+
+        assert_eq!(find("sensor.van_weather_condition").1["state"], "sunny");
+        assert_eq!(find("sensor.van_weather_humidity").1["state"], 67);
+        assert_eq!(find("sensor.van_weather_precip_probability").1["state"], 12);
+        assert_eq!(find("sensor.van_weather_forecast_daily").1["state"], 1);
+        assert_eq!(
+            find("sensor.van_weather_forecast_daily").1["attributes"]["forecast"][0]["condition"],
+            "rainy"
+        );
+        assert_eq!(find("sensor.van_weather_forecast_hourly").1["state"], 1);
+    }
+
+    #[test]
+    fn omits_missing_optional_current_sensors_but_keeps_percentage_sensors() {
+        let weather = parse_weather(ApiResponse::default());
+        let updates = weather_updates(&weather);
+
+        assert!(
+            !updates
+                .iter()
+                .any(|(id, _)| id == "sensor.van_weather_temperature")
+        );
+        assert_eq!(
+            updates
+                .iter()
+                .find(|(id, _)| id == "sensor.van_weather_humidity")
+                .unwrap()
+                .1["state"],
+            0
+        );
+    }
+
+    #[test]
+    fn masks_coordinates_to_about_eleven_kilometres() {
+        assert!((mask_coordinate(37.7749) - 37.8).abs() < f64::EPSILON);
+        assert!((mask_coordinate(-122.4194) - (-122.4)).abs() < f64::EPSILON);
+    }
+}

systems/brain/services/van_weather.nix

@@ -1,8 +1,10 @@
 {
   pkgs,
-  inputs,
   ...
 }:
+let
+  van-weather = pkgs.callPackage ../../../rust/van_weather/package.nix { };
+in
 {
   systemd.services.van-weather = {
     description = "Van Weather Service";
@@ -13,13 +15,9 @@
     requires = [ "home-assistant.service" ];
     wantedBy = [ "multi-user.target" ];
 
-    environment = {
-      PYTHONPATH = "${inputs.self}/";
-    };
-
     serviceConfig = {
       Type = "simple";
-      ExecStart = "${pkgs.my_python}/bin/python -m python.van_weather.main";
+      ExecStart = "${van-weather}/bin/van-weather";
       EnvironmentFile = "/etc/van_weather.env";
       Restart = "on-failure";
       RestartSec = "5s";
@@ -29,7 +27,6 @@
       ProtectSystem = "strict";
       ProtectHome = "read-only";
       PrivateTmp = true;
-      ReadOnlyPaths = [ "${inputs.self}" ];
     };
   };
 }