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//! Reference-point policies for temporal sample alignment.
//!
//! SPDX-License-Identifier: MIT OR Apache-2.0
/// How lag-aligned samples choose their contemporaneous origin row.
#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash, Default)]
pub enum ReferencePointPolicy {
/// Origin at row `max_lag` so every lag in `0..=max_lag` is in-bounds
/// (default stationary series alignment).
#[default]
SeriesOrigin,
/// Absolute origin row; effective samples are
/// `origin_row .. series_len` clipped so lags stay in-bounds.
AbsoluteOrigin {
/// Row treated as contemporaneous lag-0.
origin_row: usize,
},
}
impl ReferencePointPolicy {
/// Base contemporaneous row and effective sample count for a series.
///
/// # Errors
///
/// Empty series, `max_lag` too large, or origin out of range.
pub fn base_and_n(
self,
series_len: usize,
max_lag: u32,
) -> Result<(usize, usize), crate::error::DataError> {
use crate::error::DataError;
if series_len == 0 {
return Err(DataError::InvalidArgument { message: "empty time series".into() });
}
let max_lag_usize = max_lag as usize;
if max_lag_usize >= series_len {
return Err(DataError::InvalidArgument {
message: "max_lag must be strictly less than series length".into(),
});
}
match self {
Self::SeriesOrigin => {
let base = max_lag_usize;
Ok((base, series_len - base))
}
Self::AbsoluteOrigin { origin_row } => {
if origin_row < max_lag_usize || origin_row >= series_len {
return Err(DataError::InvalidArgument {
message: "absolute origin must satisfy max_lag <= origin < series_len"
.into(),
});
}
Ok((origin_row, series_len - origin_row))
}
}
}
}