pub mod join;

use crate::attachment::{Joint, JointOf, Joints, PartInShip, Peer, SnapOf, SnapOfJoint};
use crate::ecs::{DragRequestEvent, Part, Player, PlayerStorage};
use crate::server::system_sets::PlayerInputSet;
use crate::server::ConnectedNetworkEntity;
use crate::prelude::*;
use crate::server::world_config::WorldConfigResource;
use bevy_replicon::prelude::{ClientId, FromClient};
use std::f32::consts::PI;

pub fn player_management_plugin(app: &mut App) {
    app.add_systems(
        Update,
        (
            join::handle_pending_players,
            join::handle_new_players,
            magic_fuel_regen,
            dragging,
        )
            .in_set(PlayerInputSet),
    );
    app.add_systems(Update, complete_partial_disconnects);
}

#[derive(Component)]
struct PartiallyDisconnected;

/// Partial Disconnects are created when a part is disconnected to indicate that a disconnect has started.
/// Disconnects cannot be completed until the next tick, after relevant Peer relationships have been removed.
/// This system does this by performing a flood search to determine if the 'partial-disconnected' parts still have
/// a valid path to hearty; if they do not, they are removed from the ship.
fn complete_partial_disconnects(
    partial_disconnected_parts: Query<Entity, With<PartiallyDisconnected>>,
    mut q_joints: Query<&Joints>,
    mut q_maybe_peer: Query<Option<&Peer>>,
    mut q_joint_of_part: Query<&JointOf>,
    mut q_is_hearty: Query<Option<&Player>>,
    dc_q_joints: Query<(&Joint, &JointOf, &Transform, Option<&Peer>, Entity)>,
    dc_q_only_joints: Query<&Joints>,

    mut commands: Commands,
) {
    for partially_disconnected_part in &partial_disconnected_parts {

        trace!(?partially_disconnected_part, "completing partial disconnect from previous tick");
        commands.entity(partially_disconnected_part).remove::<PartiallyDisconnected>();

        // is it still connected to hearty?
        let mut search_visited_joints = vec![];
        let can_reach_hearty = can_reach_hearty(
            partially_disconnected_part,
            q_joints.reborrow(),
            q_maybe_peer.reborrow(),
            q_joint_of_part.reborrow(),
            q_is_hearty.reborrow(),
            &mut search_visited_joints,
            true
        );
        if can_reach_hearty {
            // great, leave them alone
            continue;
        }
        // this part cannot reach hearty
        // trigger a disconnect on them to propagate the disconnection

        let mut disconnect_queue = vec![];
        commands.entity(partially_disconnected_part).remove::<PartInShip>(); // they're no longer in the ship, remove them from the meta
        disconnect_part(
            (partially_disconnected_part, if let Ok(j) = q_joints.get(partially_disconnected_part) { j } else {
                warn!(?partially_disconnected_part, "part does not have a Joints? this should be impossible...");
                continue;
            }),
            &dc_q_joints,
            &dc_q_only_joints,
            &mut disconnect_queue,
            commands.reborrow()
        );
        commands.entity(partially_disconnected_part).remove::<PartiallyDisconnected>();
    }
}

/// Determine if a part has a path to hearty by performing a depth-first search
/// TODO: This can be very slow on large ships- the path propagation model will be significantly faster
/// TODO: Ask core for an explanation of what the path propagation model is if you want to implement this
fn can_reach_hearty(
    part: Entity,

    mut q_joints: Query<&Joints>,
    mut q_maybe_peer: Query<Option<&Peer>>,
    mut q_joint_of_part: Query<&JointOf>,
    mut q_is_hearty: Query<Option<&Player>>,

    visited_joints: &mut Vec<Entity>,

    is_top_of_recursion: bool
) -> bool {
    // Are we hearty?
    if let Ok(Some(_)) = q_is_hearty.get(part) {
        debug!("partial detach DFS: visited {} joints => we are hearty! @ {:?}", visited_joints.len(), part);
        return true;
    }

    // Get the joints of this entity
    let Ok(our_joints) = q_joints.get(part).cloned() else {
        warn!("part does not have a Joints? this should be impossible...");
        return false;
    };

    // Iterate over each joint:
    // if it's Hearty: great! we're connected
    // if it's another part: recurse to it
    // if it's not connected: lame, move on
    'to_next_joint: for joint in &**our_joints {
        // mark that we've visited this joint, so we don't come back to it later
        visited_joints.push(*joint);

        // does this joint have a peer?
        let maybe_peer = q_maybe_peer.get(*joint).expect("cannot fail");

        if let Some(peer_info) = maybe_peer {
            // we have a peer! figure out what it's connected to...
            let other_parts_joint = peer_info.peer_joint_entity_id;
            // have we visited this joint already?
            if visited_joints.contains(&other_parts_joint) {
                // if so, move on
                continue 'to_next_joint;
            }
            // we have not, find it's parent part
            let other_part = q_joint_of_part.get(other_parts_joint).expect("joint is missing JointOf").0;
            // is this part Hearty?
            let maybe_is_hearty = q_is_hearty.get(other_part).expect("cannot fail");
            if maybe_is_hearty.is_some() {
                // yay! found hearty
                debug!("partial detach DFS: visited {} joints => found hearty @ {:?}", visited_joints.len(), other_part);
                debug!("-> via {:?}", part);
                return true;
            }
            // not hearty. but can the other part reach hearty?
            let can_other_part_reach = can_reach_hearty(
                other_part,
                q_joints.reborrow(),
                q_maybe_peer.reborrow(),
                q_joint_of_part.reborrow(),
                q_is_hearty.reborrow(),
                visited_joints,
                false
            );
            if can_other_part_reach {
                // great, they are connected
                // log that we're in the path, then bubble up
                debug!("-> via {:?}", part);
                return true;
            }

        }
    }

    // Exhausted all options; we are not connected to hearty bubble up
    if is_top_of_recursion {
        // print a debug message
        debug!("partial detach DFS: visited {} joints => not connected", visited_joints.len());
    }
    false
}



fn disconnect_part(
    (entity, joints): (Entity, &Joints),
    q_joints: &Query<(&Joint, &JointOf, &Transform, Option<&Peer>, Entity)>,
    q_only_joints: &Query<&Joints>,
    processed_peers: &mut Vec<Entity>,
    mut commands: Commands,
) {
    //trace!(?entity, ?joints, ?processed_peers, "recursive disconnect");
    // loop the joints in the entity
    for joint in joints.iter() {
        // now we have the entity "joint"
        let Ok((_, _, _, peer, _)) = q_joints.get(joint) else {
            continue;
        };
        // don't want to double process a joint
        if processed_peers.contains(&joint) { continue; }

        // we have the peer that holds the physics joint
        let Some(peer) = peer else { continue; };
        commands.entity(joint).remove::<Peer>();
        processed_peers.push(joint);

        let mut physics_joint = commands.entity(peer.physics_joint);
        // the physics joint shouldnt exist anymore
        physics_joint.despawn();

        // delete the other side's peer that exists for some reason
        let Ok((_, other_joint_of, _, _, _)) = q_joints.get(peer.peer_joint_entity_id) else {
            continue;
        };
        commands.entity(peer.peer_joint_entity_id).remove::<Peer>();

        let Ok(_) = q_only_joints.get(other_joint_of.0) else {
            continue
        };
        //commands.entity(other_joint_of.0).remove::<PartInShip>();

        if !processed_peers.contains(&peer.peer_joint_entity_id) {
            disconnect_part((other_joint_of.0, joints), q_joints,
                q_only_joints, processed_peers, commands.reborrow());
        }

        processed_peers.push(peer.peer_joint_entity_id);
    }
    // recursive disconnect part
    //commands.entity(entity).remove::<PartInShip>();
    commands.entity(entity).insert(PartiallyDisconnected);
}

fn dragging(
    mut events: MessageReader<FromClient<DragRequestEvent>>,
    mut parts: Query<
        (
            &mut Transform,
            Option<&PartInShip>,
            Entity,
            &mut LinearVelocity,
            &Joints,
            &mut AngularVelocity,
            &Part,
        ),
        Without<Joint>,
    >,
    snaps: Query<(&SnapOf, &SnapOfJoint)>,
    joints: Query<(&Joint, &JointOf, &Transform, Option<&Peer>, Entity)>,
    q_joints: Query<&Joints>,
    clients: Query<&ConnectedNetworkEntity>,
    q_ls_me: Query<Entity, With<crate::client::Me>>,
    world_config: Res<WorldConfigResource>,
    mut commands: Commands,
) {
    let Some(world_config) = &world_config.config else {
        return;
    };
    for FromClient {
        client_id,
        message: event,
    } in events.read()
    {
        let player_hearty_entity = match client_id {
            ClientId::Client(client_entity) => {
                let ConnectedNetworkEntity {
                    game_entity: player_hearty_entity,
                } = clients.get(*client_entity).unwrap();
                player_hearty_entity
            },
            ClientId::Server => &q_ls_me.iter().next().unwrap()
        };

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

        #[allow(unused_assignments, reason = "false positive")]
        let mut teleport_to_translation = Vec2::new(0.0, 0.0);
        #[allow(unused_assignments, reason = "false positive")]
        let mut teleport_to_rotation = Quat::from_rotation_z(0.0);
        let mut new_linvel = None;
        let mut new_angvel = 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
            // getting attached to (hearty)
            let target_part = {
                let Ok(target_part) = parts.get(target_joint.1.0) else {
                    continue;
                };
                target_part
            };

            // attached (housing)
            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 mut processed = vec![source_joint.4];
            disconnect_part(
                (source_part.2, source_part.4),
                &joints,
                &q_joints,
                &mut processed,
                commands.reborrow(),
            );

            // create the joint...
            let joint = PrismaticJoint::new(target_part.2, source_part.2)
                .with_slider_axis(source_joint.2.translation.xy().normalize())
                .with_local_anchor1(target_joint.2.translation.xy())
                .with_local_basis1(target_joint.0.transform.rotation.to_euler(EulerRot::ZYX).0 + PI
                    - source_joint.0.transform.rotation.to_euler(EulerRot::ZYX).0)
                .with_limits(0.0, 0.0)
                .with_align_compliance(world_config.part.joint_align_compliance)
                .with_angle_compliance(world_config.part.joint_angle_compliance)
                .with_limit_compliance(world_config.part.joint_limit_compliance);
            let joint_damping = JointDamping {
                linear: world_config.part.joint_linear_damping,
                angular: world_config.part.joint_angular_damping,
            };

            let joint_id = commands.spawn((joint, joint_damping)).id();

            // create the peering component...
            commands.entity(source_joint.4).insert(Peer {
                peer_joint_entity_id: target_joint.4,
                processed: true,
                physics_joint: joint_id
            });
            commands.entity(target_joint.4).insert(Peer {
                peer_joint_entity_id: source_joint.4,
                processed: true,
                physics_joint: joint_id
            });

            // 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);

            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_linvel = Some(*target_part.3);
            new_angvel = Some(*target_part.5);
            // 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 processed = vec![];
            disconnect_part(
                (source_part.2, source_part.4),
                &joints,
                &q_joints,
                &mut processed,
                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_linvel {
            *part.3 = new_vel;
        }
        if let Some(new_vel) = new_angvel {
            *part.5 = new_vel;
        }
        // ( the math sucks )
    }
}

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);
    }
}