sba-scouting/rust/src/calc/matchup.rs

use super::league_stats::StatDistribution;
use super::weights::StatWeight;

/// Convert a raw stat value to a standardized score (-3 to +3).
///
/// Uses standard deviation thresholds from the league mean.
/// A value of 0 always returns +3 (best possible).
pub fn standardize_value(value: f64, distribution: &StatDistribution, high_is_better: bool) -> i32 {
    if value == 0.0 {
        return 3;
    }

    let avg = distribution.avg;
    let stdev = distribution.stdev;

    let base_score = if value > avg + 2.0 * stdev {
        -3
    } else if value > avg + stdev {
        -2
    } else if value > avg + 0.33 * stdev {
        -1
    } else if value > avg - 0.33 * stdev {
        0
    } else if value > avg - stdev {
        1
    } else if value > avg - 2.0 * stdev {
        2
    } else {
        3
    };

    if high_is_better { -base_score } else { base_score }
}

/// Calculate weighted score for a single stat.
pub fn calculate_weighted_score(
    value: f64,
    distribution: &StatDistribution,
    stat_weight: &StatWeight,
) -> f64 {
    let std_score = standardize_value(value, distribution, stat_weight.high_is_better);
    std_score as f64 * stat_weight.weight as f64
}

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

    fn dist(avg: f64, stdev: f64) -> StatDistribution {
        StatDistribution { avg, stdev }
    }

    // --- standardize_value tests ---

    #[test]
    fn zero_value_always_returns_3() {
        let d = dist(5.0, 1.0);
        assert_eq!(standardize_value(0.0, &d, true), 3);
        assert_eq!(standardize_value(0.0, &d, false), 3);
    }

    #[test]
    fn value_far_above_mean_is_minus3_base() {
        // value > avg + 2*stdev => base_score = -3
        let d = dist(5.0, 1.0);
        // high_is_better=true: -(-3) = 3
        assert_eq!(standardize_value(7.5, &d, true), 3);
        // high_is_better=false: -3
        assert_eq!(standardize_value(7.5, &d, false), -3);
    }

    #[test]
    fn value_far_below_mean_is_plus3_base() {
        // value <= avg - 2*stdev => base_score = 3
        let d = dist(5.0, 1.0);
        // high_is_better=true: -(3) = -3
        assert_eq!(standardize_value(2.5, &d, true), -3);
        // high_is_better=false: 3
        assert_eq!(standardize_value(2.5, &d, false), 3);
    }

    #[test]
    fn value_at_mean_returns_zero_base() {
        // avg - 0.33*stdev < value < avg + 0.33*stdev => base_score = 0
        let d = dist(5.0, 1.0);
        assert_eq!(standardize_value(5.0, &d, true), 0);
        assert_eq!(standardize_value(5.0, &d, false), 0);
    }

    #[test]
    fn score_ranges_are_symmetric() {
        // Walk through all 7 buckets with a clean distribution
        let d = dist(10.0, 2.0);

        // base_score mapping (raw, not flipped):
        //   > 14.0 (avg+2*std) => -3
        //   > 12.0 (avg+std)   => -2
        //   > 10.66 (avg+0.33*std) => -1
        //   > 9.34 (avg-0.33*std)  => 0
        //   > 8.0 (avg-std)    => 1
        //   > 6.0 (avg-2*std)  => 2
        //   <= 6.0             => 3

        // Test with high_is_better=false (no flip)
        assert_eq!(standardize_value(15.0, &d, false), -3);
        assert_eq!(standardize_value(13.0, &d, false), -2);
        assert_eq!(standardize_value(11.0, &d, false), -1);
        assert_eq!(standardize_value(10.0, &d, false), 0);
        assert_eq!(standardize_value(9.0, &d, false), 1);
        assert_eq!(standardize_value(7.0, &d, false), 2);
        assert_eq!(standardize_value(5.0, &d, false), 3);
    }

    // --- calculate_weighted_score tests ---

    #[test]
    fn weighted_score_multiplies_std_by_weight() {
        let d = dist(10.0, 2.0);
        let w = StatWeight { weight: 5, high_is_better: true };
        // value=15.0 => base=-3, flipped=3 => 3*5=15.0
        assert!((calculate_weighted_score(15.0, &d, &w) - 15.0).abs() < f64::EPSILON);
    }

    #[test]
    fn weighted_score_zero_value() {
        let d = dist(10.0, 2.0);
        let w = StatWeight { weight: 3, high_is_better: false };
        // value=0.0 => always 3 => 3*3=9.0
        assert!((calculate_weighted_score(0.0, &d, &w) - 9.0).abs() < f64::EPSILON);
    }
}