optionstratlib-core 0.24.0

//! Target crate (ADR-0001 D6): **core**. Owns `ClockError`.
//!
//! A build without the `clock` feature has no wall clock, and everything that
//! asks for the current time gets this error rather than a made-up instant: a
//! wrong time would silently price an option wrongly.

use expiration_date::error::ExpirationDateError;
use thiserror::Error;

/// The current time was asked for and this build cannot provide it.
///
/// [`crate::utils::time::now`], [`crate::utils::time::evaluation_time`] and
/// [`crate::utils::time::resolution_base`] return it as such, and
/// `TradeError`, `PositionError`, `ChainError`, `StrategyError` and
/// `TransactionError` have a `Clock` variant for it.
///
/// A time to expiry is different. `years_to_expiration` and its siblings return
/// the `expiration_date` crate's own error, which cannot name this one, so
/// [`ExpirationDateError::InvalidDateTime`] holds its message, and it arrives as
/// `OptionsError::ExpirationDate`, `PricingError::Options`, `GreeksError::ExpirationDate`
/// and so on.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Error)]
#[non_exhaustive]
pub enum ClockError {
    /// The crate was built without the `clock` feature, and the operation has no
    /// explicit time to use instead. A reference datetime stands in for the clock only
    /// where a time to expiry or an expiry date is measured, not where a new record is
    /// stamped.
    #[error(
        "the wall clock is unavailable: this build has no `clock` feature, so pass the time \
         explicitly, through a date argument or the `*_at` form of the call where there is \
         one; a time to expiry can also measure from the thread's reference datetime"
    )]
    Unavailable,
}

impl From<ClockError> for ExpirationDateError {
    #[cold]
    #[inline(never)]
    fn from(err: ClockError) -> Self {
        Self::InvalidDateTime(err.to_string())
    }
}

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

    #[test]
    fn test_clock_error_converts_to_invalid_datetime_keeping_its_message() {
        let message = ClockError::Unavailable.to_string();
        let converted = ExpirationDateError::from(ClockError::Unavailable);
        assert!(
            matches!(converted, ExpirationDateError::InvalidDateTime(ref text) if *text == message)
        );
        assert!(message.contains("wall clock is unavailable"));
    }
}