ballistics-engine 0.14.1

/// Form factor calculations for drag enhancement
use crate::DragModel;

/// Get default form factor based on bullet type
pub fn get_default_form_factor(bullet_name: &str, drag_model: &DragModel) -> f64 {
    let name_upper = bullet_name.to_uppercase();

    match drag_model {
        DragModel::G1 => {
            if name_upper.contains("MATCH")
                || name_upper.contains("SMK")
                || name_upper.contains("SCENAR")
                || name_upper.contains("BERGER")
            {
                0.90 // Match bullets
            } else if name_upper.contains("VLD")
                || name_upper.contains("HYBRID")
                || name_upper.contains("ELD")
            {
                0.85 // Very low drag bullets
            } else if name_upper.contains("FMJ") {
                1.10 // Full metal jacket
            } else if name_upper.contains("HUNT") || name_upper.contains("SP") {
                1.05 // Hunting bullets
            } else {
                1.00 // Default
            }
        }
        DragModel::G7 => {
            if name_upper.contains("MATCH")
                || name_upper.contains("SMK")
                || name_upper.contains("SCENAR")
            {
                0.95 // Match bullets
            } else if name_upper.contains("VLD") || name_upper.contains("HYBRID") {
                0.90 // Very low drag bullets
            } else if name_upper.contains("FMJ") {
                1.15 // Full metal jacket (less efficient for G7)
            } else {
                1.05 // Default G7
            }
        }
        _ => 1.00, // Default form factor for other models
    }
}

/// Apply form factor to drag coefficient
pub fn apply_form_factor_to_drag(
    cd_base: f64,
    bullet_name: Option<&str>,
    drag_model: &DragModel,
    use_form_factor: bool,
) -> f64 {
    if !use_form_factor {
        return cd_base;
    }

    // Get form factor based on bullet type
    let form_factor = if let Some(name) = bullet_name {
        get_default_form_factor(name, drag_model)
    } else {
        1.0 // No correction if no bullet name
    };

    // Apply form factor to drag coefficient
    cd_base * form_factor
}

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

    #[test]
    fn test_g1_form_factors() {
        let drag_model = DragModel::G1;

        // Match bullets should have lower form factor
        assert_eq!(get_default_form_factor("168gr SMK", &drag_model), 0.90);
        assert_eq!(get_default_form_factor("Berger Match", &drag_model), 0.90);
        assert_eq!(get_default_form_factor("Lapua Scenar", &drag_model), 0.90);

        // VLD bullets should have even lower
        assert_eq!(get_default_form_factor("VLD Target", &drag_model), 0.85);
        assert_eq!(get_default_form_factor("ELD-X", &drag_model), 0.85); // ELD without "Match"
        assert_eq!(get_default_form_factor("Hybrid OTM", &drag_model), 0.85); // Hybrid without "Match"

        // FMJ should have higher form factor
        assert_eq!(get_default_form_factor("M855 FMJ", &drag_model), 1.10);

        // Hunting bullets
        assert_eq!(get_default_form_factor("Hunting SP", &drag_model), 1.05);

        // Default
        assert_eq!(get_default_form_factor("Generic Bullet", &drag_model), 1.00);
    }

    #[test]
    fn test_g7_form_factors() {
        let drag_model = DragModel::G7;

        // Match bullets
        assert_eq!(get_default_form_factor("175gr SMK", &drag_model), 0.95);

        // VLD bullets
        assert_eq!(get_default_form_factor("VLD Hunting", &drag_model), 0.90);

        // FMJ less efficient with G7
        assert_eq!(get_default_form_factor("147gr FMJ", &drag_model), 1.15);

        // Default G7
        assert_eq!(get_default_form_factor("Generic", &drag_model), 1.05);
    }

    #[test]
    fn test_apply_form_factor() {
        let cd_base = 0.5;
        let drag_model = DragModel::G1;

        // With form factor enabled
        let cd_with_ff = apply_form_factor_to_drag(cd_base, Some("168gr SMK"), &drag_model, true);
        assert_eq!(cd_with_ff, 0.5 * 0.90); // 0.45

        // With form factor disabled
        let cd_without_ff =
            apply_form_factor_to_drag(cd_base, Some("168gr SMK"), &drag_model, false);
        assert_eq!(cd_without_ff, 0.5);

        // No bullet name
        let cd_no_name = apply_form_factor_to_drag(cd_base, None, &drag_model, true);
        assert_eq!(cd_no_name, 0.5); // No correction
    }

    #[test]
    fn test_case_insensitive() {
        let drag_model = DragModel::G1;

        // Should work with various cases
        assert_eq!(get_default_form_factor("smk", &drag_model), 0.90);
        assert_eq!(get_default_form_factor("SMK", &drag_model), 0.90);
        assert_eq!(get_default_form_factor("SmK", &drag_model), 0.90);
    }
}