rosu-pp 4.0.1

Difficulty and performance calculation for osu!
Documentation 
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use crate::{
    any::difficulty::object::IDifficultyObject,
    osu::difficulty::object::OsuDifficultyObject,
    util::{
        difficulty::{milliseconds_to_bpm, reverse_lerp, smootherstep, smoothstep},
        float_ext::FloatExt,
    },
};

pub struct AimEvaluator;

impl AimEvaluator {
    const WIDE_ANGLE_MULTIPLIER: f64 = 1.5;
    const ACUTE_ANGLE_MULTIPLIER: f64 = 2.55;
    const SLIDER_MULTIPLIER: f64 = 1.35;
    const VELOCITY_CHANGE_MULTIPLIER: f64 = 0.75;
    const WIGGLE_MULTIPLIER: f64 = 1.02;

    #[expect(clippy::too_many_lines, reason = "staying in-sync with lazer")]
    pub fn evaluate_diff_of<'a>(
        curr: &'a OsuDifficultyObject<'a>,
        diff_objects: &'a [OsuDifficultyObject<'a>],
        with_slider_travel_dist: bool,
    ) -> f64 {
        let osu_curr_obj = curr;

        let Some((osu_last_last_obj, osu_last_obj)) = curr
            .previous(1, diff_objects)
            .zip(curr.previous(0, diff_objects))
            .filter(|(_, last)| !(curr.base.is_spinner() || last.base.is_spinner()))
        else {
            return 0.0;
        };

        #[expect(clippy::items_after_statements, reason = "staying in-sync with lazer")]
        const RADIUS: i32 = OsuDifficultyObject::NORMALIZED_RADIUS;
        #[expect(clippy::items_after_statements, reason = "staying in-sync with lazer")]
        const DIAMETER: i32 = OsuDifficultyObject::NORMALIZED_DIAMETER;

        // * Calculate the velocity to the current hitobject, which starts
        // * with a base distance / time assuming the last object is a hitcircle.
        let mut curr_vel = osu_curr_obj.lazy_jump_dist / osu_curr_obj.adjusted_delta_time;

        // * But if the last object is a slider, then we extend the travel
        // * velocity through the slider into the current object.
        if osu_last_obj.base.is_slider() && with_slider_travel_dist {
            // * calculate the slider velocity from slider head to slider end.
            let travel_vel = osu_last_obj.travel_dist / osu_last_obj.travel_time;
            // * calculate the movement velocity from slider end to current object
            let movement_vel = osu_curr_obj.min_jump_dist / osu_curr_obj.min_jump_time;

            // * take the larger total combined velocity.
            curr_vel = curr_vel.max(movement_vel + travel_vel);
        }

        // * As above, do the same for the previous hitobject.
        let mut prev_vel = osu_last_obj.lazy_jump_dist / osu_last_obj.adjusted_delta_time;

        if osu_last_last_obj.base.is_slider() && with_slider_travel_dist {
            let travel_vel = osu_last_last_obj.travel_dist / osu_last_last_obj.travel_time;
            let movement_vel = osu_last_obj.min_jump_dist / osu_last_obj.min_jump_time;

            prev_vel = prev_vel.max(movement_vel + travel_vel);
        }

        let mut wide_angle_bonus = 0.0;
        let mut acute_angle_bonus = 0.0;
        let mut slider_bonus = 0.0;
        let mut vel_change_bonus = 0.0;
        let mut wiggle_bonus = 0.0;

        // * Start strain with regular velocity.
        let mut aim_strain = curr_vel;

        if let Some((curr_angle, last_angle)) = osu_curr_obj.angle.zip(osu_last_obj.angle) {
            // * Rewarding angles, take the smaller velocity as base.
            let angle_bonus = curr_vel.min(prev_vel);

            // * If rhythms are the same.
            if osu_curr_obj
                .adjusted_delta_time
                .max(osu_last_obj.adjusted_delta_time)
                < 1.25
                    * osu_curr_obj
                        .adjusted_delta_time
                        .min(osu_last_obj.adjusted_delta_time)
            {
                acute_angle_bonus = Self::calc_acute_angle_bonus(curr_angle);

                // * Penalize angle repetition.
                acute_angle_bonus *= 0.08
                    + 0.92
                        * (1.0
                            - f64::min(
                                acute_angle_bonus,
                                f64::powf(Self::calc_acute_angle_bonus(last_angle), 3.0),
                            ));

                // * Apply acute angle bonus for BPM above 300 1/2 and distance more than one diameter
                acute_angle_bonus *= angle_bonus
                    * smootherstep(
                        milliseconds_to_bpm(osu_curr_obj.adjusted_delta_time, Some(2)),
                        300.0,
                        400.0,
                    )
                    * smootherstep(
                        osu_curr_obj.lazy_jump_dist,
                        f64::from(DIAMETER),
                        f64::from(DIAMETER * 2),
                    );
            }

            wide_angle_bonus = Self::calc_wide_angle_bonus(curr_angle);

            // * Penalize angle repetition.
            wide_angle_bonus *= 1.0
                - f64::min(
                    wide_angle_bonus,
                    f64::powf(Self::calc_wide_angle_bonus(last_angle), 3.0),
                );

            // * Apply full wide angle bonus for distance more than one diameter
            wide_angle_bonus *=
                angle_bonus * smootherstep(osu_curr_obj.lazy_jump_dist, 0.0, f64::from(DIAMETER));

            // * Apply wiggle bonus for jumps that are [radius, 3*diameter] in distance, with < 110 angle
            // * https://www.desmos.com/calculator/dp0v0nvowc
            wiggle_bonus = angle_bonus
                * smootherstep(
                    osu_curr_obj.lazy_jump_dist,
                    f64::from(RADIUS),
                    f64::from(DIAMETER),
                )
                * f64::powf(
                    reverse_lerp(
                        osu_curr_obj.lazy_jump_dist,
                        f64::from(DIAMETER * 3),
                        f64::from(DIAMETER),
                    ),
                    1.8,
                )
                * smootherstep(curr_angle, f64::to_radians(110.0), f64::to_radians(60.0))
                * smootherstep(
                    osu_last_obj.lazy_jump_dist,
                    f64::from(RADIUS),
                    f64::from(DIAMETER),
                )
                * f64::powf(
                    reverse_lerp(
                        osu_last_obj.lazy_jump_dist,
                        f64::from(DIAMETER * 3),
                        f64::from(DIAMETER),
                    ),
                    1.8,
                )
                * smootherstep(last_angle, f64::to_radians(110.0), f64::to_radians(60.0));

            if let Some(osu_last_2_obj) = curr.previous(2, diff_objects) {
                let distance =
                    (osu_last_2_obj.base.stacked_pos() - osu_last_obj.base.stacked_pos()).length();

                if distance < 1.0 {
                    wide_angle_bonus *= 1.0 - 0.35 * f64::from(1.0 - distance);
                }
            }
        }

        if prev_vel.max(curr_vel).not_eq(0.0) {
            // * We want to use the average velocity over the whole object when awarding
            // * differences, not the individual jump and slider path velocities.
            prev_vel = (osu_last_obj.lazy_jump_dist + osu_last_last_obj.travel_dist)
                / osu_last_obj.adjusted_delta_time;
            curr_vel = (osu_curr_obj.lazy_jump_dist + osu_last_obj.travel_dist)
                / osu_curr_obj.adjusted_delta_time;

            // * Scale with ratio of difference compared to 0.5 * max dist.
            let dist_ratio = smoothstep(
                (prev_vel - curr_vel).abs() / prev_vel.max(curr_vel),
                0.0,
                1.0,
            );

            // * Reward for % distance up to 125 / strainTime for overlaps where velocity is still changing.
            let overlap_vel_buff = (f64::from(DIAMETER) * 1.25
                / osu_curr_obj
                    .adjusted_delta_time
                    .min(osu_last_obj.adjusted_delta_time))
            .min((prev_vel - curr_vel).abs());

            vel_change_bonus = overlap_vel_buff * dist_ratio;

            // * Penalize for rhythm changes.
            let bonus_base = (osu_curr_obj.adjusted_delta_time)
                .min(osu_last_obj.adjusted_delta_time)
                / (osu_curr_obj.adjusted_delta_time).max(osu_last_obj.adjusted_delta_time);
            vel_change_bonus *= bonus_base.powf(2.0);
        }

        if osu_last_obj.base.is_slider() {
            // * Reward sliders based on velocity.
            slider_bonus = osu_last_obj.travel_dist / osu_last_obj.travel_time;
        }

        aim_strain += wiggle_bonus * Self::WIGGLE_MULTIPLIER;
        aim_strain += vel_change_bonus * Self::VELOCITY_CHANGE_MULTIPLIER;

        // * Add in acute angle bonus or wide angle bonus, whichever is larger.
        aim_strain += (acute_angle_bonus * Self::ACUTE_ANGLE_MULTIPLIER)
            .max(wide_angle_bonus * Self::WIDE_ANGLE_MULTIPLIER);

        aim_strain *= osu_curr_obj.small_circle_bonus;

        // * Add in additional slider velocity bonus.
        if with_slider_travel_dist {
            aim_strain += slider_bonus * Self::SLIDER_MULTIPLIER;
        }

        aim_strain
    }

    const fn calc_wide_angle_bonus(angle: f64) -> f64 {
        smoothstep(angle, f64::to_radians(40.0), f64::to_radians(140.0))
    }

    const fn calc_acute_angle_bonus(angle: f64) -> f64 {
        smoothstep(angle, f64::to_radians(140.0), f64::to_radians(40.0))
    }
}