use std::f32::consts::{FRAC_PI_3, FRAC_PI_4};

use avian3d::{
    dynamics::solver::xpbd::AngularConstraint, parry::mass_properties::MassProperties, prelude::*,
};
use bevy::prelude::{
    Commands, Entity, Quat, Query, Res, ResMut, Time, Transform, Vec3, With, Without,
};

//#[cfg(feature = "inspector")]
//use super::ActionDebugInstant;
use super::{CatControllerSettings, CatControllerState, CyberLean, MovementSettings, Tunneling};
use crate::{
    bike::{CyberBikeBody, CyberSteering, CyberWheel, WheelConfig, BIKE_WHEEL_COLLISION_GROUP},
    input::InputState,
};

fn yaw_to_angle(yaw: f32) -> f32 {
    let v = yaw.powi(5) * FRAC_PI_4;
    if v.is_normal() {
        v
    } else {
        0.0
    }
}

fn rotate_point(pt: &Vec3, rot: &Quat) -> Vec3 {
    // thanks to https://danceswithcode.net/engineeringnotes/quaternions/quaternions.html
    let [x, y, z] = pt.normalize().to_array();
    let qpt = Quat::from_xyzw(x, y, z, 0.0);
    // p' = rot^-1 * qpt * rot
    let rot_qpt = rot.inverse() * qpt * *rot;

    // why does this need to be inverted???
    -Vec3::from_array([rot_qpt.x, rot_qpt.y, rot_qpt.z])
}

/// The gravity vector points from the cyberbike to the center of the planet.
pub(super) fn gravity(
    mut query: Query<(&Transform, &mut ExternalForce), With<CyberBikeBody>>,
    settings: Res<MovementSettings>,
    mut gravity: ResMut<Gravity>,
    #[cfg(feature = "inspector")] mut debug_instant: ResMut<ActionDebugInstant>,
) {
    let (xform, mut forces) = query.single_mut();
    *gravity = Gravity(xform.translation.normalize() * -settings.gravity);
    forces.clear();
}

/// The desired lean angle, given steering input and speed.
pub(super) fn cyber_lean(
    bike_state: Query<(&LinearVelocity, &Transform), With<CyberBikeBody>>,
    wheels: Query<&Transform, With<CyberWheel>>,
    input: Res<InputState>,
    gravity_settings: Res<MovementSettings>,
    mut lean: ResMut<CyberLean>,
) {
    let (velocity, xform) = bike_state.single();
    let vel = velocity.dot(*xform.forward());
    let v_squared = vel.powi(2);
    let steering_angle = yaw_to_angle(input.yaw);
    let wheels: Vec<_> = wheels.iter().map(|w| w.translation).collect();
    let wheel_base = (wheels[0] - wheels[1]).length();
    let radius = wheel_base / steering_angle.tan();
    let gravity = gravity_settings.gravity;
    let v2_r = v_squared / radius;
    let tan_theta = (v2_r / gravity).clamp(-FRAC_PI_3, FRAC_PI_3);

    if tan_theta.is_finite() && !tan_theta.is_subnormal() {
        lean.lean = tan_theta.atan().clamp(-FRAC_PI_4, FRAC_PI_4);
    } else {
        lean.lean = 0.0;
    }
}

/// PID-based controller for stabilizing attitude; keeps the cyberbike upright.
pub(super) fn falling_cat(
    mut bike_query: Query<(&Transform, &mut ExternalTorque, &mut CatControllerState)>,
    time: Res<Time>,
    settings: Res<CatControllerSettings>,
    lean: Res<CyberLean>,
) {
    let (xform, mut torque, mut control_vars) = bike_query.single_mut();
    let world_up = xform.translation.normalize();
    let rot = Quat::from_axis_angle(*xform.back(), lean.lean);
    let target_up = rotate_point(&world_up, &rot).normalize();

    let bike_right = xform.right();

    let roll_error = bike_right.dot(target_up);
    let pitch_error = world_up.dot(*xform.back());

    // only try to correct roll if we're not totally vertical
    if pitch_error.abs() < 0.95 {
        let (derivative, integral) = control_vars.update_roll(roll_error, time.delta_seconds());
        let mag =
            (settings.kp * roll_error) + (settings.ki * integral) + (settings.kd * derivative);
        if mag.is_finite() {
            torque.apply_torque(*xform.back() * mag);
        }
    }
}

/// Apply forces to the cyberbike as a result of input.
pub(super) fn input_forces(
    settings: Res<MovementSettings>,
    input: Res<InputState>,
    time: Res<Time>,
    axle: Query<Entity, With<CyberSteering>>,
    mut braking_query: Query<&mut ExternalTorque, With<CyberWheel>>,
    mut body_query: Query<
        (
            Entity,
            &Transform,
            &ColliderMassProperties,
            &mut ExternalForce,
        ),
        With<CyberBikeBody>,
    >,
) {
    let (bike, xform, mass, mut forces) = body_query.single_mut();
    let dt = time.delta_seconds();

    // thrust
    let thrust = xform.forward() * input.throttle * settings.accel;
    let point = xform.translation + *xform.back();

    *forces.apply_force_at_point(dt * thrust, point, mass.center_of_mass.0);

    // brake + thrust
    for mut motor in braking_query.iter_mut() {
        let factor = if input.brake {
            500.00
        } else {
            input.throttle * settings.accel
        };
        let speed = if input.brake { 0.0 } else { -70.0 };
        let target = dt * factor * speed;
        let torque = target * Vec3::X;
        motor.apply_torque(torque);
    }

    // steering
    let _angle = yaw_to_angle(input.yaw);
    let _axle = axle.single();
    //steering.align_orientation(bike, steering, rotation_difference, lagrange,
    // compliance, dt)
}