weather_dot_gov_rs/src/dwml.rs

//! Encapsulates the DWML implementation details

use chrono::FixedOffset;
use serde::Deserialize;

/// Top-level structure
#[derive(Debug, Deserialize, PartialEq)]
pub struct Dwml {
    pub head: Head,
    pub data: (Forecast, CurrentObservations),
}

impl Dwml {
    /// Returns the current "high" temperature.
    ///
    /// Panics if the data doesn't show a current high
    pub fn current_maximum(&self) -> TempWithUnit {
        self.forecast()
            .parameters
            .temp_by_type(TempType::Maximum)
            .first()
    }

    /// Returns the current "low" temperature.
    ///
    /// Panics if the data doesn't show a current low
    pub fn current_minimum(&self) -> TempWithUnit {
        self.forecast()
            .parameters
            .temp_by_type(TempType::Minimum)
            .first()
    }

    fn forecast(&self) -> &Forecast {
        &self.data.0
    }
}

impl std::str::FromStr for Dwml {
    type Err = quick_xml::DeError;

    fn from_str(s: &str) -> Result<Self, quick_xml::DeError> {
        quick_xml::de::from_str(s)
    }
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct Head {
    pub product: Product,
    pub source: Source,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct Forecast {
    pub location: Location,
    #[serde(rename = "time-layout")]
    pub time_layout: (TimeLayout, TimeLayout, TimeLayout),
    pub parameters: Parameters,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct Location {
    #[serde(rename = "area-description")]
    pub area_description: Option<String>,
    pub description: Option<String>,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct TimeLayout {
    #[serde(rename = "@time-coordinate")]
    pub time_coordinate: TimeCoordinate,

    #[serde(rename = "layout-key")]
    pub layout_key: TimeLayoutKey,

    #[serde(rename = "start-valid-time")]
    pub start_valid_time: Vec<StartValidTime>,
}

#[derive(Debug, Deserialize, PartialEq)]
pub enum TimeCoordinate {
    #[serde(rename = "local")]
    Local,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct StartValidTime {
    #[serde(rename = "@period-name")]
    pub period_name: String,

    #[serde(rename = "$value")]
    pub value: DateTime,
}

#[derive(Debug, Deserialize, PartialEq)]
#[serde(try_from = "String")]
pub struct DateTime(pub chrono::DateTime<FixedOffset>);
impl TryFrom<String> for DateTime {
    type Error = chrono::ParseError;

    fn try_from(s: String) -> Result<Self, Self::Error> {
        chrono::DateTime::parse_from_rfc3339(&s).map(Self)
    }
}

/// Observations at time of request
///
/// Note that `time-layout` isn't parsed because in San Franscisco it returns a time with no timezone, which makes the schema too complicated. It's in local California time, so we could graft on a timezone from another part of the XML, but why bother.
#[derive(Debug, Deserialize, PartialEq)]
pub struct CurrentObservations {
    pub location: Location,
    pub parameters: CurrentParameters,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct CurrentParameters {
    pub temperature: (Temperature, Temperature),
    pub humidity: Humidity,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct Humidity {
    #[serde(rename = "@type")]
    pub humidity_type: HumidityType,
    pub value: u8,
}

#[derive(Debug, Deserialize, PartialEq)]
pub enum HumidityType {
    #[serde(rename = "relative")]
    Relative,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct Product {
    #[serde(rename = "creation-date")]
    pub creation_date: CreationDate,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct CreationDate {
    #[serde(rename = "@refresh-frequency")]
    pub refresh_frequency: String,

    #[serde(rename = "$value")]
    pub value: String,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct Source {
    #[serde(rename = "production-center")]
    pub production_center: String,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct Parameters {
    pub temperature: [Temperature; 2],

    #[serde(rename = "probability-of-precipitation")]
    pub probability_of_precipitation: ProbabilityOfPrecipitation,

    pub weather: Weather,
}

impl Parameters {
    fn temp_by_type(&self, temp_type: TempType) -> &Temperature {
        for temp in &self.temperature {
            if temp.temp_type == temp_type {
                return temp;
            }
        }
        panic!("Couldn't find a Temperature with the given TempType");
    }
}

pub struct TempWithUnit {
    pub units: TempUnits,
    pub value: i32,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct Temperature {
    #[serde(rename = "@type")]
    pub temp_type: TempType,

    #[serde(rename = "@units")]
    pub units: TempUnits,

    #[serde(rename = "@time-layout")]
    pub time_layout: TimeLayoutKey,

    pub value: Vec<i32>,
}

impl Temperature {
    fn first(&self) -> TempWithUnit {
        let value = *self
            .value
            .first()
            .expect("temperatures should always have at least one value");
        TempWithUnit {
            units: self.units,
            value,
        }
    }
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct ProbabilityOfPrecipitation {
    #[serde(rename = "@time-layout")]
    pub time_layout: TimeLayoutKey,

    pub value: Vec<PrecipitationValue>,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct Weather {
    #[serde(rename = "@time-layout")]
    pub time_layout: TimeLayoutKey,

    #[serde(rename = "weather-conditions")]
    pub weather_conditions: Vec<WeatherCondition>,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct WeatherCondition {
    /// e.g. "Showers Likely" or "Partly Sunny"
    #[serde(rename = "@weather-summary")]
    pub weather_summary: String,
}

// If only there was a percentage that could convey the concept of
// no precipitation.
#[derive(Debug, Deserialize, PartialEq)]
pub struct PrecipitationValue {
    #[serde(rename = "$text")]
    pub value: Option<u32>,
}

#[derive(Clone, Copy, Debug, Deserialize, PartialEq)]
pub enum TempType {
    #[serde(rename = "apparent")]
    Apparent,
    #[serde(rename = "dew point")]
    DewPoint,
    #[serde(rename = "minimum")]
    Minimum,
    #[serde(rename = "maximum")]
    Maximum,
}

#[derive(Clone, Copy, Debug, Deserialize, PartialEq)]
pub enum TempUnits {
    Celsius,
    Fahrenheit,
}

#[derive(Debug, Deserialize, PartialEq)]
pub struct TimeLayoutKey(String);

#[cfg(test)]
mod tests {
    use super::*;
    use anyhow::{Context as _, Result};

    #[test]
    fn empire_city() {
        let s = include_str!("../data/empire_city.xml");
        let dwml: Dwml = quick_xml::de::from_str(s).unwrap();

        assert_eq!(dwml.current_maximum().value, 33);
        assert_eq!(dwml.current_minimum().value, 26);
    }

    #[test]
    fn sunset_city() {
        let s = include_str!("../data/sunset_city.xml");
        let _: Dwml = quick_xml::de::from_str(s).unwrap();
    }

    #[test]
    fn windy_city() {
        let s = include_str!("../data/windy_city.xml");
        let _: Dwml = quick_xml::de::from_str(s).unwrap();
    }

    #[test]
    fn date() -> Result<()> {
        for s in ["2025-01-01T23:00:00-00:00", "2025-01-01T23:00:00-00:00"] {
            let _ = chrono::DateTime::parse_from_rfc3339(s).context(s).unwrap();
        }
        Ok(())
    }
}