use crate::attachment::{Joint, JointOf, Joints, PartInShip, Peer, SnapOf, SnapOfJoint};
use crate::config::planet::Planet;
use crate::ecs::{DragRequestEvent, Part, Player, PlayerStorage, PlayerThrust, ThrustEvent};
use crate::server::part::SpawnPartRequest;
use crate::server::system_sets::PlayerInputSet;
use crate::server::world_config::WorldConfigResource;
use crate::server::{ConnectedGameEntity, ConnectedNetworkEntity};
use bevy::prelude::*;
use bevy_rapier2d::prelude::{ExternalForce, FixedJointBuilder, ImpulseJoint, Velocity};
use bevy_replicon::prelude::{ClientId, FromClient};
use std::f32::consts::PI;

pub fn player_management_plugin(app: &mut App) {
    app.add_systems(
        Update,
        (
            handle_new_players,
            player_thrust,
            magic_fuel_regen,
            (reprocess_reattached_parts, dragging).chain(),
        )
            .in_set(PlayerInputSet),
    );
}

#[derive(Component)]
struct JointNeedsCreation(ImpulseJoint);

fn disconnect_part(
    entity: Entity,
    recursed_entity: Entity,
    joints: &Joints,
    q_joints: Query<&Joints>,
    q_peer: Query<(Entity, &Peer, &JointOf)>,
    mut processed_peers: &mut Vec<Entity>,
    mut commands: Commands,
) {
    trace!(?entity, ?joints, ?processed_peers, "recursive disconnect");
    // recursive disconnect part
    for joint in &**joints {
        let Ok((p_e, other_joint_handle, _)) = q_peer.get(*joint) else {
            continue;
        };
        if processed_peers.contains(&p_e) { continue };
        let other_joint = other_joint_handle.0;

        commands.entity(*joint).remove::<Peer>();
        processed_peers.push(p_e);

        let Ok((p_e_2, _, other_joint_of)) = q_peer.get(other_joint) else {
            continue;
        };

        commands.entity(other_joint).remove::<Peer>();
        processed_peers.push(p_e_2);

        let Ok(joints) = q_joints.get(other_joint_of.0) else {
            continue;
        };
        if other_joint != recursed_entity {
            disconnect_part(other_joint, entity, joints, q_joints, q_peer, processed_peers, commands.reborrow());
        }
    }
    for ppeer in processed_peers {
        commands.entity(*ppeer).remove::<Peer>();
    }
    commands.entity(entity).remove::<ImpulseJoint>();
    commands.entity(entity).remove::<PartInShip>();
}

fn dragging(
    mut events: MessageReader<FromClient<DragRequestEvent>>,
    mut parts: Query<
        (
            &mut Transform,
            Option<&PartInShip>,
            Entity,
            &mut Velocity,
            &Joints,
        ),
        (With<Part>, Without<Joint>),
    >,
    snaps: Query<(&SnapOf, &SnapOfJoint)>,
    joints: Query<(&Joint, &JointOf, &Transform, Option<&Peer>, Entity)>,
    peer: Query<(Entity, &Peer, &JointOf)>,
    q_joints: Query<&Joints>,
    q_joint: Query<&ImpulseJoint>,
    clients: Query<&ConnectedNetworkEntity>,
    mut commands: Commands,
) {
    for FromClient {
        client_id,
        message: event,
    } in events.read()
    {
        let client_entity = match client_id {
            ClientId::Client(e) => e,
            _ => continue,
        };
        let ConnectedNetworkEntity {
            game_entity: player_hearty_entity,
        } = clients.get(*client_entity).unwrap();

        debug!(?event, "got drag request event");

        let mut teleport_to_translation = Vec2::new(0.0, 0.0);
        let mut teleport_to_rotation = Quat::from_rotation_z(0.0);
        let mut new_vel = None;

        if let Some(snap_to) = event.snap_target
            && let Some(peer_snap) = event.peer_snap
        {
            let Ok(snap_on_target) = snaps.get(snap_to) else {
                continue;
            };
            let Ok(snap_on_source) = snaps.get(peer_snap) else {
                continue;
            };

            let Ok(target_joint) = joints.get(snap_on_target.1.0) else {
                continue;
            };
            let Ok(source_joint) = joints.get(snap_on_source.1.0) else {
                continue;
            };

            // validation step 1: everything must match. if not, ignore the request
            if snap_on_target.0.0 != target_joint.1.0 {
                warn!(
                    "drag request: mismatched target entities (potential manipulation?), ignoring"
                );
                continue;
            }
            if snap_on_source.0.0 != source_joint.1.0 {
                warn!(
                    "drag request: mismatched source entities (potential manipulation?), ignoring request"
                );
                continue;
            }

            // we've passed initial validation.
            // do not allow drags with the source or destination if they already have a peer (are attached)
            if target_joint.3.is_some() {
                warn!(
                    "drag request: cannot attach to a joint that already has a peer, ignoring request"
                );
                continue;
            }
            if source_joint.3.is_some() {
                warn!(
                    "drag request: dragging from a part that is already attached is currently not supported, ignoring request"
                );
                continue;
            }

            // great, the attachment appears to be valid
            // let's make sure this player is allowed to drag onto this part
            let target_part = {
                let Ok(target_part) = parts.get(target_joint.1.0) else {
                    continue;
                };
                target_part
            };

            let source_part = {
                let Ok(source_part) = parts.get(source_joint.1.0) else {
                    continue;
                };
                source_part
            };

            let allowed = target_joint.1.0 == *player_hearty_entity
                || target_part.1.is_some_and(|u| u.0 == *player_hearty_entity);
            if !allowed {
                warn!("drag request: this player cannot move this part, ignoring request");
                continue;
            }

            // TODO - validate source_part?

            // great, we have a valid peering request

            let did_disconnect = q_joint.get(source_part.2).is_ok();
            let mut dc_queue = vec![];
            disconnect_part(
                source_part.2,
                Entity::PLACEHOLDER,
                source_part.4,
                q_joints,
                peer,
                &mut dc_queue,
                commands.reborrow(),
            );

            // create the peering component...
            commands.entity(source_joint.4).insert(Peer(target_joint.4, true));
            commands.entity(target_joint.4).insert(Peer(source_joint.4, true));

            // propagate PartInShip...

            let part_in_ship = if target_joint.1.0 == *player_hearty_entity {
                PartInShip(*player_hearty_entity)
            } else {
                PartInShip(target_part.1.unwrap().0) // unwrap: checked above (during 'allowed' calculation)
            };

            commands.entity(source_part.2).insert(part_in_ship);

            let target_position = target_part.0.mul_transform(*target_joint.2);

            let rotation = event.set_rotation.to_scaled_axis().z;
            let rotation = Rot2::radians(rotation);

            // create the joint...
            let joint = FixedJointBuilder::new()
                .local_anchor1(target_joint.2.translation.xy())
                .local_basis1(
                    target_joint.0.transform.rotation.to_euler(EulerRot::ZYX).0 + PI
                        - source_joint.0.transform.rotation.to_euler(EulerRot::ZYX).0,
                );

            commands.entity(source_part.2).remove::<ImpulseJoint>();
            if did_disconnect {
                // we disconnected this part this tick, and are performing a "reattachment"
                // (dragging an already attached part from peering point A to peering point B)

                // If we're reattaching to a different part, rapier will ignore our new attachment
                // as it will be seen as a mutation (removing and adding a component in the
                // same tick is considered equivalent to mutation by Bevy).
                // As Rapier does not allow you to mutate the source/destination of a joint,
                // the change will be outright ignored.

                // Since there is no (easy) way to get the real joint information back out of Rapier,
                // or to force it to accept what it sees as invalid mutation,
                // we need to delay the creation of the new joint by 1 tick so it's noticed by Rapier
                // This component will be swapped out for a real ImpulseJoint on the next tick
                // by `reprocess_reattached_parts` (in this file)
                commands
                    .entity(source_part.2)
                    .insert(JointNeedsCreation(ImpulseJoint::new(target_part.2, joint)));
            } else {
                commands
                    .entity(source_part.2)
                    .insert(ImpulseJoint::new(target_part.2, joint));
            }

            teleport_to_translation = target_position.translation.xy();
            teleport_to_rotation = target_position.rotation
                * source_joint.0.transform.rotation.inverse()
                * Quat::from_rotation_z(PI);
            new_vel = Some(*target_part.3);
            // and we're done!
        } else {
            warn!(
                "blindly accepting non-attachment request, someone should change this eventually"
            );
            warn!("dragging already attached entities may cause inconsistent behavior!!");
            let source_part = parts.get(event.drag_target).unwrap();
            let mut dc_queue = vec![];
            disconnect_part(
                source_part.2,
                Entity::PLACEHOLDER,
                source_part.4,
                q_joints,
                peer,
                &mut dc_queue,
                commands.reborrow(),
            );
            teleport_to_translation = event.drag_to;
            teleport_to_rotation = event.set_rotation;
        }

        let mut part = parts.get_mut(event.drag_target).unwrap();
        part.0.translation.x = teleport_to_translation.x;
        part.0.translation.y = teleport_to_translation.y;
        part.0.rotation = teleport_to_rotation; // client calculates this; no reason to recalculate
        if let Some(new_vel) = new_vel {
            *part.3 = new_vel;
        }
        // ( the math sucks )
    }
}

// LOGIC: **MUST** run BEFORE `dragging`
fn reprocess_reattached_parts(
    reattached: Query<(Entity, &JointNeedsCreation)>,
    mut commands: Commands,
) {
    for (e, j) in &reattached {
        commands
            .entity(e)
            .remove::<JointNeedsCreation>()
            .insert(j.0);
    }
}

fn handle_new_players(
    mut commands: Commands,
    q_new_clients: Query<Entity, Added<ConnectedGameEntity>>,
    world_config: Res<WorldConfigResource>,
    planets: Query<(&Transform, &Planet)>,
    asset_server: Res<AssetServer>,
) {
    let Some(wc) = &world_config.config else {
        return;
    };
    for joined_player in &q_new_clients {
        trace!(?joined_player, "detected joined player!");
        // find earth
        let (spawn_planet_pos, spawn_planet) = planets
            .iter()
            .find(|p| p.1.name == wc.hearty.spawn_at)
            .unwrap_or_else(|| {
                panic!(
                    "spawn planet {} is missing? (check that the planet is named exactly '{}')",
                    wc.hearty.spawn_at, wc.hearty.spawn_at
                )
            });
        let angle = rand::random::<f32>() * std::f32::consts::TAU;
        let offset = spawn_planet.radius + 150.0;
        let mut new_transform =
            Transform::from_xyz(angle.cos() * offset, angle.sin() * offset, 0.0);
        new_transform.rotate_z(angle);
        new_transform.translation += spawn_planet_pos.translation;

        info!(?new_transform, ?joined_player, "set player's position!");

        commands
            .entity(joined_player)
            .insert(new_transform)
            .insert(SpawnPartRequest(
                asset_server.load("config/parts/hearty.part.toml"),
            ))
            .insert(PlayerThrust::default())
            .insert(PlayerStorage {
                fuel_capacity: 25.0,
                fuel: 25.0,
                power_capacity: 25.0,
                power: 25.0,
            })
            .insert(Velocity::default())
            .insert(Player {
                client: joined_player,
            });
    }
}

fn magic_fuel_regen(players: Query<&mut PlayerStorage, With<Player>>, time: Res<Time>) {
    for mut storage in players {
        storage.fuel = (storage.fuel + 5.0 * time.delta_secs()).min(storage.fuel_capacity);
    }
}

fn player_thrust(
    mut players: Query<(
        &Transform,
        &Part,
        &mut ExternalForce,
        &mut PlayerThrust,
        &mut PlayerStorage,
    )>,
    clients: Query<&ConnectedNetworkEntity>,
    mut thrust_event: MessageReader<FromClient<ThrustEvent>>,
    world_config: Res<WorldConfigResource>,
) {
    for FromClient {
        client_id,
        message: event,
    } in thrust_event.read()
    {
        let client_entity = match client_id {
            ClientId::Client(e) => e,
            _ => continue,
        };
        let ConnectedNetworkEntity { game_entity } = clients.get(*client_entity).unwrap();

        let Ok((_, _, _, mut thrust, _)) = players.get_mut(*game_entity) else {
            continue;
        };

        match *event {
            ThrustEvent::Up(on) => thrust.up = on,
            ThrustEvent::Down(on) => thrust.down = on,
            ThrustEvent::Left(on) => thrust.left = on,
            ThrustEvent::Right(on) => thrust.right = on,
        }
    }
    for (transform, part, mut force, thrust, mut storage) in &mut players {
        let Some(world_config) = &world_config.config else {
            return;
        };

        let forward = (transform.rotation * Vec3::Y).xy();
        let mut external_force = ExternalForce::default();

        // indices are quadrants:
        // 1 | 0
        // --+--
        // 2 | 3
        //
        let mut thrusters = [0.0; 4];

        if thrust.up {
            thrusters[1] = 1.0;
            thrusters[2] = 1.0;
        }
        if thrust.down {
            thrusters[0] = 1.0;
            thrusters[3] = 1.0;
        }
        if thrust.left {
            thrusters[0] = 1.0;
            thrusters[2] = 1.0;
        }
        if thrust.right {
            thrusters[1] = 1.0;
            thrusters[3] = 1.0;
        }

        // prevent fuel wasting when turning while moving forward/reverse
        if thrusters[2] == thrusters[3] && thrusters[3] != 0.0 {
            (thrusters[2], thrusters[3]) = (0.0, 0.0);
        }
        if thrusters[0] == thrusters[1] && thrusters[1] != 0.0 {
            (thrusters[0], thrusters[1]) = (0.0, 0.0);
        }

        let half_size = Vec2::new(
            world_config.part.default_width / 2.0,
            world_config.part.default_height / 2.0,
        )
        .length();
        external_force += ExternalForce::at_point(
            -forward * thrusters[0] * world_config.hearty.thrust,
            transform.translation.xy()
                + half_size
                    * Vec2::new((1.0 * PI / 4.0).cos(), (1.0 * PI / 4.0).sin()).rotate(forward),
            transform.translation.xy(),
        );
        external_force += ExternalForce::at_point(
            forward * thrusters[1] * world_config.hearty.thrust,
            transform.translation.xy()
                + half_size
                    * Vec2::new((3.0 * PI / 4.0).cos(), (3.0 * PI / 4.0).sin()).rotate(forward),
            transform.translation.xy(),
        );
        external_force += ExternalForce::at_point(
            forward * thrusters[2] * world_config.hearty.thrust,
            transform.translation.xy()
                + half_size
                    * Vec2::new((5.0 * PI / 4.0).cos(), (5.0 * PI / 4.0).sin()).rotate(forward),
            transform.translation.xy(),
        );
        external_force += ExternalForce::at_point(
            -forward * thrusters[3] * world_config.hearty.thrust,
            transform.translation.xy()
                + half_size
                    * Vec2::new((7.0 * PI / 4.0).cos(), (7.0 * PI / 4.0).sin()).rotate(forward),
            transform.translation.xy(),
        );
        *force += external_force;

        storage.fuel -=
            thrusters.iter().sum::<f32>() * part.strong_config.thruster.as_ref().unwrap().flow_rate;
    }
}