use bevy::{
    app::AppExit,
    prelude::*,
};
use bevy_mod_picking::*;
use crate::pieces::*;


pub struct Square {
    pub x: u8,
    pub y: u8,
}

impl Square {
    fn is_white(&self) -> bool {
        (self.x + self.y + 1) % 2 == 0
    }
}


struct PlayerTurn(PieceColor);
impl Default for PlayerTurn {
    fn default() -> Self {
        Self(PieceColor::White)
    }
}


#[derive(Default)]
struct SelectedSquare {
    entity: Option<Entity>,
}

#[derive(Default)]
struct SelectedPiece {
    entity: Option<Entity>,
}


pub struct BoardPlugin;
impl Plugin for BoardPlugin {
    fn build(&self, app: &mut AppBuilder) {
        app.init_resource::<SelectedSquare>()
            .init_resource::<SelectedPiece>()
            .init_resource::<PlayerTurn>()
            .add_startup_system(create_board.system())
            .add_system(select_square.system());
    }
}



fn create_board(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
    mut highlight_colors: ResMut<MeshButtonMaterials>,
) {
    // add meshes and materials
    let mesh = meshes.add(Mesh::from(shape::Plane {size: 1.0}));

    for i in 0..8 {
        for j in 0..8 {
            commands
                .spawn_bundle(PbrBundle {
                    mesh: mesh.clone(),
                    material: if (i + j + 1) % 2 == 0 {
                        materials.add(Color::rgb(1.0, 0.9, 0.9).into())
                    } else {
                        materials.add(Color::rgb(0.0, 0.1, 0.1).into())
                    },
                    transform: Transform::from_translation(Vec3::new(i as f32, 0.0, j as f32)),
                    ..Default::default()
                })
                .insert_bundle(PickableBundle::default())
                .insert(Square {
                    x: i,
                    y: j,
                });
        }
    }

    highlight_colors.hovered  = materials.add(Color::rgb(0.8, 0.3, 0.3).into());
    highlight_colors.pressed  = materials.add(Color::rgb(0.9, 0.5, 0.5).into());
    highlight_colors.selected = materials.add(Color::rgb(0.9, 0.1, 0.1).into());
}


fn select_square(
    mut commands: Commands,
    mouse_button_inputs: Res<Input<MouseButton>>,
    mut selected_square: ResMut<SelectedSquare>,
    mut selected_piece: ResMut<SelectedPiece>,
    mut turn: ResMut<PlayerTurn>,
    mut app_exit_events: EventWriter<AppExit>,
    camera_query: Query<&PickingCamera>,
    squares_query: Query<&Square>,
    mut pieces_query: Query<(Entity, &mut Piece, &Children)>,
) {
    if !mouse_button_inputs.just_pressed(MouseButton::Left) {
        return;
    }

    for camera in camera_query.iter() {
        if let Some((square_entity, _intersection)) = camera.intersect_top() {
            let pieces_entity_vec: Vec<(Entity, Piece, Vec<Entity>)> = pieces_query
                .iter_mut()
                .map(|(entity, piece, children)| {
                    (
                        entity,
                        *piece,
                        children.iter().map(|entity| *entity).collect()
                    )
                })
                .collect();
            let pieces_vec = pieces_query
                .iter_mut()
                .map(|(_, piece, _)| *piece)
                .collect();

            if let Ok(square) = squares_query.get(square_entity) {
                selected_square.entity = Some(square_entity);

                // if a piece is already selected, set it to move
                if let Some(selected_piece_entity) = selected_piece.entity {
                    if let Ok((_piece_entity, mut piece, _)) = pieces_query.get_mut(selected_piece_entity) {
                        if piece.is_move_valid((square.x, square.y), &pieces_vec) {
                            // check to see if we're capturing
                            for (other_entity, other_piece, other_children) in pieces_entity_vec {
                                if other_piece.x == square.x
                                    && other_piece.y == square.y
                                    && other_piece.color != piece.color
                                {
                                    // if the king is taken, exit
                                    if other_piece.piece_type == PieceType::King {
                                        println!(
                                            "{} won! Thanks for playing!",
                                            match turn.0 {
                                                PieceColor::White => "White",
                                                PieceColor::Black => "Black",
                                            }
                                        );
                                        app_exit_events.send(AppExit);
                                    }

                                    // despawn the piece and its children
                                    commands.entity(other_entity).despawn();
                                    for child in other_children {
                                        commands.entity(child).despawn();
                                    }
                                }
                            }

                            // and set it to move
                            piece.x = square.x;
                            piece.y = square.y;

                            turn.0 = match turn.0 {
                                PieceColor::White => PieceColor::Black,
                                PieceColor::Black => PieceColor::White,
                            }
                        }
                    }
                    selected_square.entity = None;
                    selected_piece.entity  = None;
                } else {
                    // otherwise, select the piece (if one) in the selected square
                    for (piece_entity, piece, _) in pieces_query.iter_mut() {
                        if piece.x == square.x
                            && piece.y == square.y
                            && piece.color == turn.0
                        {
                            selected_piece.entity = Some(piece_entity);
                            break;
                        }
                    }
                }
            }
        } else {
            // clicked on nothing, deselect
            selected_square.entity = None;
            selected_piece.entity  = None;
        }
    }
}