use super::{ControllerSet, Controls, collisions::kinematic_controller_collisions};
use crate::{GameState, player::PlayerBodyMesh};
use avian3d::{math::*, prelude::*};
use bevy::{ecs::query::Has, prelude::*};

pub struct CharacterControllerPlugin;

impl Plugin for CharacterControllerPlugin {
    fn build(&self, app: &mut App) {
        app.init_resource::<PlayerMovement>();

        app.register_type::<JumpImpulse>();
        app.register_type::<ControllerGravity>();
        app.register_type::<MovementAcceleration>();

        app.add_systems(
            Update,
            (set_movement_flag, update_grounded, apply_gravity, movement)
                .chain()
                .in_set(ControllerSet::ApplyControls)
                .run_if(in_state(GameState::Playing)),
        );
        app.add_systems(
            // Run collision handling after collision detection.
            //
            // NOTE: The collision implementation here is very basic and a bit buggy.
            //       A collide-and-slide algorithm would likely work better.
            PostProcessCollisions,
            kinematic_controller_collisions.run_if(in_state(GameState::Playing)),
        );
    }
}

/// A marker component indicating that an entity is using a character controller.
#[derive(Component)]
pub struct CharacterController;

/// A marker component indicating that an entity is on the ground.
#[derive(Component)]
#[component(storage = "SparseSet")]
pub struct Grounded;

#[derive(Resource, Default)]
pub struct PlayerMovement {
    pub any_direction: bool,
}

/// The acceleration used for character movement.
#[derive(Component, Reflect)]
#[reflect(Component)]
pub struct MovementAcceleration(Scalar);

#[derive(Component, Reflect)]
#[reflect(Component)]
pub struct MovementSpeedFactor(pub f32);

/// The strength of a jump.
#[derive(Component, Reflect)]
#[reflect(Component)]
pub struct JumpImpulse(Scalar);

/// The gravitational acceleration used for a character controller.
#[derive(Component, Reflect)]
#[reflect(Component)]
pub struct ControllerGravity(Vector);

/// The maximum angle a slope can have for a character controller
/// to be able to climb and jump. If the slope is steeper than this angle,
/// the character will slide down.
#[derive(Component, Reflect)]
#[reflect(Component)]
pub struct MaxSlopeAngle(pub Scalar);

/// A bundle that contains the components needed for a basic
/// kinematic character controller.
#[derive(Bundle)]
pub struct CharacterControllerBundle {
    character_controller: CharacterController,
    rigid_body: RigidBody,
    collider: Collider,
    ground_caster: ShapeCaster,
    gravity: ControllerGravity,
    movement: MovementBundle,
}

/// A bundle that contains components for character movement.
#[derive(Bundle)]
pub struct MovementBundle {
    acceleration: MovementAcceleration,
    jump_impulse: JumpImpulse,
    max_slope_angle: MaxSlopeAngle,
    factor: MovementSpeedFactor,
}

impl MovementBundle {
    pub const fn new(acceleration: Scalar, jump_impulse: Scalar, max_slope_angle: Scalar) -> Self {
        Self {
            acceleration: MovementAcceleration(acceleration),
            jump_impulse: JumpImpulse(jump_impulse),
            max_slope_angle: MaxSlopeAngle(max_slope_angle),
            factor: MovementSpeedFactor(1.),
        }
    }
}

impl CharacterControllerBundle {
    pub fn new(collider: Collider, gravity: Vector, movement: MovementBundle) -> Self {
        // Create shape caster as a slightly smaller version of collider
        let mut caster_shape = collider.clone();
        caster_shape.set_scale(Vector::ONE * 0.98, 10);

        Self {
            character_controller: CharacterController,
            rigid_body: RigidBody::Kinematic,
            collider,
            ground_caster: ShapeCaster::new(
                caster_shape,
                Vector::ZERO,
                Quaternion::default(),
                Dir3::NEG_Y,
            )
            .with_max_distance(0.2),
            gravity: ControllerGravity(gravity),
            movement,
        }
    }
}

/// Updates the [`Grounded`] status for character controllers.
fn update_grounded(
    mut commands: Commands,
    mut query: Query<
        (Entity, &ShapeHits, &Rotation, Option<&MaxSlopeAngle>),
        With<CharacterController>,
    >,
) {
    for (entity, hits, rotation, max_slope_angle) in &mut query {
        // The character is grounded if the shape caster has a hit with a normal
        // that isn't too steep.
        let is_grounded = hits.iter().any(|hit| {
            if let Some(angle) = max_slope_angle {
                (rotation * -hit.normal2).angle_between(Vector::Y).abs() <= angle.0
            } else {
                true
            }
        });

        if is_grounded {
            debug!("grounded");
            commands.entity(entity).insert(Grounded);
        } else {
            debug!("not grounded");
            commands.entity(entity).remove::<Grounded>();
        }
    }
}

/// Sets the movement flag, which is an indicator for the rig animation and the braking system.
fn set_movement_flag(mut player_movement: ResMut<PlayerMovement>, controls: Res<Controls>) {
    let mut direction = controls.keyboard_state.move_dir;
    let deadzone = 0.2;

    if let Some(gamepad) = controls.gamepad_state {
        direction += gamepad.move_dir;
    }

    if player_movement.any_direction {
        if direction.length_squared() < deadzone {
            player_movement.any_direction = false;
        }
    } else if direction.length_squared() > deadzone {
        player_movement.any_direction = true;
    }
}

/// Responds to [`MovementAction`] events and moves character controllers accordingly.
fn movement(
    time: Res<Time>,
    controls: Res<Controls>,
    mut controllers: Query<(
        &MovementAcceleration,
        &MovementSpeedFactor,
        &JumpImpulse,
        &mut LinearVelocity,
        Has<Grounded>,
    )>,
    rig_transform_q: Option<Single<&GlobalTransform, With<PlayerBodyMesh>>>,
    mut jump_used: Local<bool>,
) {
    let delta_time = time.delta_secs();

    let mut direction = controls.keyboard_state.move_dir;

    let mut jump_requested = controls.keyboard_state.jump;

    if let Some(gamepad) = controls.gamepad_state {
        direction += gamepad.move_dir;

        jump_requested |= gamepad.jump;
    }

    direction = direction.normalize_or_zero();

    for (movement_acceleration, factor, jump_impulse, mut linear_velocity, is_grounded) in
        &mut controllers
    {
        let mut direction = direction.extend(0.0).xzy();

        if let Some(ref rig_transform) = rig_transform_q {
            direction =
                (rig_transform.forward() * direction.z) + (rig_transform.right() * direction.x);
        }

        linear_velocity.x = -direction.x * movement_acceleration.0 * delta_time * factor.0;
        linear_velocity.z = -direction.z * movement_acceleration.0 * delta_time * factor.0;

        if is_grounded && jump_requested && !*jump_used {
            linear_velocity.y = jump_impulse.0;
            debug!("jump");
            *jump_used = true;
        }

        if !controls.keyboard_state.jump
            && !controls
                .gamepad_state
                .map(|state| state.jump)
                .unwrap_or_default()
        {
            *jump_used = false;
        }
    }
}

/// Applies [`ControllerGravity`] to character controllers.
fn apply_gravity(
    time: Res<Time>,
    mut controllers: Query<(&ControllerGravity, &mut LinearVelocity, Option<&Grounded>)>,
) {
    let delta_time = time.delta_secs();

    for (gravity, mut linear_velocity, grounded) in &mut controllers {
        if grounded.is_none() {
            linear_velocity.0 += gravity.0 * delta_time;
        }
    }
}