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//! Detector configuration and the config-version fingerprint.
//!
//! The fingerprint goes into the envelope: *same input + same fingerprint ⇒
//! same bytes*. Any change to a threshold that could change output also changes
//! the fingerprint, so an agent can tell "the data changed" from "the tool's
//! configuration changed."
use serde::{Deserialize, Serialize};
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DetectConfig {
/// Modified z-score threshold for the point detector (Iglewicz–Hoaglin
/// default is 3.5).
pub point_threshold: f64,
/// Minimum count of finite numeric values a column needs before the point
/// detector will assess it. Below this, statistics are unreliable.
pub point_min_n: usize,
/// Significance level for the KS and chi-square drift tests. A column is
/// flagged when the test's p-value falls below this.
pub dist_alpha: f64,
/// Population Stability Index threshold; PSI above this signals drift
/// (0.1 ≈ moderate, 0.2 ≈ significant by convention).
pub psi_threshold: f64,
/// Number of (baseline-quantile) bins used for PSI.
pub psi_bins: usize,
/// Minimum sample size (per side) before a distributional test runs.
pub dist_min_n: usize,
/// Null fraction above which the structural detector flags a column.
pub struct_null_rate: f64,
/// Significance level for the Mahalanobis multivariate test (per row).
/// Smaller than the per-column α because every row is tested.
pub mv_alpha: f64,
/// Minimum number of complete (no-missing) rows before the multivariate
/// detector will estimate a covariance and run.
pub mv_min_n: usize,
/// Relative ridge added to the covariance diagonal for numerical stability
/// (handles collinear / zero-variance columns). Scaled by the mean variance.
pub mv_ridge: f64,
/// Seasonal period for the contextual detector. `0` (or `1`) disables it —
/// seasonality is never guessed, so without a declared period the detector
/// reports honest absence.
pub ctx_period: usize,
/// Modified z-score threshold within a seasonal subseries.
pub ctx_threshold: f64,
/// Minimum finite values a phase needs before it is assessed.
pub ctx_min_per_phase: usize,
/// Minimum length of an ordered numeric column before the collective
/// (change-point) detector will run.
pub coll_min_n: usize,
/// Standardized mean-shift threshold for the collective detector. Set
/// conservatively because the change point is chosen by maximization.
pub coll_threshold: f64,
/// Column to assess for metronomic cadence (interpreted as event times).
/// `None` disables the cadence detector — which timestamps mean "time" is
/// never guessed, so without this it reports honest absence.
pub cadence_column: Option<String>,
/// Coefficient-of-variation threshold below which inter-arrival intervals
/// are flagged as suspiciously regular (automated).
pub cad_max_cv: f64,
/// Minimum number of intervals before cadence is assessed.
pub cad_min_n: usize,
}
impl Default for DetectConfig {
fn default() -> Self {
DetectConfig {
point_threshold: 3.5,
point_min_n: 8,
dist_alpha: 0.05,
psi_threshold: 0.2,
psi_bins: 10,
dist_min_n: 20,
struct_null_rate: 0.5,
mv_alpha: 0.001,
mv_min_n: 20,
mv_ridge: 1e-9,
ctx_period: 0,
ctx_threshold: 3.5,
ctx_min_per_phase: 4,
coll_min_n: 20,
coll_threshold: 5.0,
cadence_column: None,
cad_max_cv: 0.05,
cad_min_n: 20,
}
}
}
impl DetectConfig {
/// A stable, human-legible fingerprint of the settings that affect output.
/// Deterministic: no wall-clock, no environment.
pub fn version(&self) -> String {
format!(
"anomalyx-cfg/5;pt={:.4};ptn={};da={:.4};psi={:.4};psib={};dmn={};snr={:.4};mva={:.5};mvn={};mvr={:e};cxp={};cxt={:.4};cxm={};cln={};clt={:.4};cdc={};cdcv={:.4};cdn={}",
self.point_threshold,
self.point_min_n,
self.dist_alpha,
self.psi_threshold,
self.psi_bins,
self.dist_min_n,
self.struct_null_rate,
self.mv_alpha,
self.mv_min_n,
self.mv_ridge,
self.ctx_period,
self.ctx_threshold,
self.ctx_min_per_phase,
self.coll_min_n,
self.coll_threshold,
self.cadence_column.as_deref().unwrap_or(""),
self.cad_max_cv,
self.cad_min_n,
)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn version_is_stable_and_reflects_changes() {
let a = DetectConfig::default();
let b = DetectConfig::default();
assert_eq!(a.version(), b.version());
let c = DetectConfig {
point_threshold: 4.0,
..DetectConfig::default()
};
assert_ne!(a.version(), c.version());
}
}