arvo 0.9.0

Validated, immutable value objects for common domain types (email, money, identifiers, …)
Documentation 
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use crate::errors::ValidationError;
use crate::traits::ValueObject;
use rust_decimal::Decimal;

/// Input type for [`PositiveDecimal`].
pub type PositiveDecimalInput = Decimal;

/// Output type for [`PositiveDecimal`].
pub type PositiveDecimalOutput = Decimal;

/// A strictly positive decimal number (`Decimal > 0`).
///
/// Zero and negative values are rejected on construction.
///
/// # Example
///
/// ```rust,ignore
/// use arvo::primitives::PositiveDecimal;
/// use arvo::traits::ValueObject;
/// use rust_decimal_macros::dec;
///
/// let price = PositiveDecimal::new(dec!(9.99)).unwrap();
/// assert_eq!(*price.value(), dec!(9.99));
///
/// assert!(PositiveDecimal::new(dec!(0)).is_err());
/// ```
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[cfg_attr(feature = "serde", serde(transparent))]
pub struct PositiveDecimal(Decimal);

impl ValueObject for PositiveDecimal {
    type Input = PositiveDecimalInput;
    type Output = PositiveDecimalOutput;
    type Error = ValidationError;

    fn new(value: Self::Input) -> Result<Self, Self::Error> {
        if value <= Decimal::ZERO {
            return Err(ValidationError::OutOfRange {
                type_name: "PositiveDecimal",
                min: "0 (exclusive)".into(),
                max: "∞".into(),
                actual: value.to_string(),
            });
        }
        Ok(Self(value))
    }

    fn value(&self) -> &Self::Output {
        &self.0
    }

    fn into_inner(self) -> Self::Input {
        self.0
    }
}

impl std::fmt::Display for PositiveDecimal {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use rust_decimal::prelude::FromStr;

    #[test]
    fn accepts_positive_value() {
        let d = PositiveDecimal::new(Decimal::from_str("9.99").unwrap()).unwrap();
        assert_eq!(d.value(), &Decimal::from_str("9.99").unwrap());
    }

    #[test]
    fn rejects_zero() {
        assert!(PositiveDecimal::new(Decimal::ZERO).is_err());
    }

    #[test]
    fn rejects_negative() {
        assert!(PositiveDecimal::new(Decimal::from_str("-1").unwrap()).is_err());
    }
}