invr 0.2.3

Declarative data validation engine using invariants executed on Polars DataFrames.
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use crate::infrastructure::polars::kind::PolarsKind;
use crate::invariant::Invariant;
use crate::scope::Scope;
use polars::prelude::*;

///
/// Builds the Polars expression counting rows where the string length
/// is outside the allowed range.
///
/// Required parameters:
/// - `min`: minimum allowed string length (inclusive)
/// - `max`: maximum allowed string length (inclusive)
///
/// Scope:
/// - Requires `Scope::Column`
///
/// Behavior:
/// - Computes `len_chars()` on the target column
/// - Marks rows where length < min OR length > max
/// - Returns the total count of out-of-range rows
///
/// The resulting metric represents the number of invalid-length values.
pub fn plan(inv: &Invariant<PolarsKind>) -> Option<Expr> {
    let Scope::Column { name } = inv.scope() else {
        return None;
    };

    let min: i64 = inv.require_param("min").ok()?.parse().ok()?;
    let max: i64 = inv.require_param("max").ok()?.parse().ok()?;

    let len = col(name).str().len_chars();

    let too_short = len.clone().lt(lit(min));
    let too_long = len.gt(lit(max));

    Some(too_short.or(too_long).sum())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::domain::invariant::value_object::id::InvariantId;
    use std::collections::BTreeMap;

    fn make_invariant(min: i64, max: i64) -> Invariant<PolarsKind> {
        let id = InvariantId::new("string_length_between_test").unwrap();
        let mut params = BTreeMap::new();
        params.insert("min".to_string(), min.to_string());
        params.insert("max".to_string(), max.to_string());

        Invariant::new(
            id,
            PolarsKind::StringLengthBetween,
            Scope::Column {
                name: "a".to_string(),
            },
        )
        .with_params(params)
    }

    fn df(values: Vec<&str>) -> DataFrame {
        let height = values.len();
        let series = Series::new("a".into(), values);
        DataFrame::new(height, vec![series.into()]).unwrap()
    }

    #[test]
    fn test_plan_returns_expr() {
        let inv = make_invariant(2, 5);
        assert!(plan(&inv).is_some());
    }

    #[test]
    fn test_no_violation_when_lengths_in_range() {
        let df = df(vec!["ab", "abcd", "abc"]);
        let inv = make_invariant(2, 5);

        let result = df.lazy().select([plan(&inv).unwrap()]).collect().unwrap();

        let count = result.columns()[0]
            .get(0)
            .unwrap()
            .try_extract::<i64>()
            .unwrap();

        assert_eq!(count, 0);
    }

    #[test]
    fn test_violation_when_length_out_of_range() {
        let df = df(vec!["a", "abcdef", "abc"]); // too short + too long
        let inv = make_invariant(2, 5);

        let result = df.lazy().select([plan(&inv).unwrap()]).collect().unwrap();

        let count = result.columns()[0]
            .get(0)
            .unwrap()
            .try_extract::<i64>()
            .unwrap();

        assert_eq!(count, 2);
    }

    #[test]
    fn test_wrong_scope_returns_none() {
        let id = InvariantId::new("wrong_scope").unwrap();
        let inv = Invariant::new(id, PolarsKind::StringLengthBetween, Scope::Dataset);

        assert!(plan(&inv).is_none());
    }
}