//! This example illustrates the various features of Bevy UI using bevy_bundletree::BundleTree.

use bevy::{
    a11y::{
        accesskit::{NodeBuilder, Role},
        AccessibilityNode,
    }, color::palettes::css::GREEN, input::mouse::{MouseScrollUnit, MouseWheel}, prelude::*, winit::WinitSettings
};

use bevy_bundletree::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        // Only run the app when there is user input. This will significantly reduce CPU/GPU use.
        .insert_resource(WinitSettings::desktop_app())
        .add_systems(Startup, setup)
        .add_systems(Update, mouse_scroll)
        .run();
}


/// Define an enum to represent all possible node types in the UI tree.
#[allow(clippy::large_enum_variant)]
#[derive(IntoBundleTree, BundleEnum)]
enum UiNode {
    Node(NodeBundle),
    Text(TextBundle),
    TextNode((NodeBundle, Text)),
    LabelText((TextBundle, Label)),
    AccessibilityLabelText((TextBundle, Label, AccessibilityNode)),
    AccessibilityScrollList((NodeBundle, ScrollingList, AccessibilityNode)),
    ImageNode((NodeBundle, UiImage)),
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    // Camera
    commands.spawn(Camera2dBundle::default());

    let tree: BundleTree<UiNode> =
    // Root node
    NodeBundle {
        style: Style {
            width: Val::Percent(100.0),
            height: Val::Percent(100.0),
            justify_content: JustifyContent::SpaceBetween,
            ..default()
        },
        ..default()
    }.with_children([
        // Left vertical fill (border)
        NodeBundle {
            style: Style {
                width: Val::Px(200.),
                border: UiRect::all(Val::Px(2.)),
                ..default()
            },
            background_color: Color::srgb(0.65, 0.65, 0.65).into(),
            ..default()
        }.with_children([
            // Left vertical fill (content)
            NodeBundle {
                style: Style {
                    width: Val::Percent(100.),
                    ..default()
                },
                background_color: Color::srgb(0.15, 0.15, 0.15).into(),
                ..default()
            }.with_children([
                    // Text
                    BundleTree::new((TextBundle::from_section(
                        "Text Example",
                        TextStyle {
                            font: asset_server.load("fonts/FiraSans-Bold.ttf"),
                            font_size: 30.0,
                            ..default()
                        },
                    )
                    .with_style(Style {
                        margin: UiRect::all(Val::Px(5.)),
                        ..default()
                    }),
                    // Because this is a distinct label widget and
                    // not button/list item text, this is necessary
                    // for accessibility to treat the text accordingly.
                    Label,
                ))]),
            
        ]),
        // Right vertical fill
        NodeBundle {
            style: Style {
                flex_direction: FlexDirection::Column,
                justify_content: JustifyContent::Center,
                align_items: AlignItems::Center,
                width: Val::Px(200.),
                ..default()
            },
            background_color: Color::srgb(0.15, 0.15, 0.15).into(),
            ..default()
        }.with_children([
            // Title
            (
                TextBundle::from_section(
                "Scrolling list",
                TextStyle {
                    font: asset_server.load("fonts/FiraSans-Bold.ttf"),
                    font_size: 25.,
                        ..default()
                    },
                ),
                Label
            ).into_tree(),
            // List with hidden overflow
            NodeBundle {
                style: Style {
                    flex_direction: FlexDirection::Column,
                    align_self: AlignSelf::Stretch,
                    height: Val::Percent(50.),
                    overflow: Overflow::clip_y(),
                    ..default()
                },
                background_color: Color::srgb(0.10, 0.10, 0.10).into(),
                ..default()
            }.with_children([
                // Moving panel
                (
                    NodeBundle {
                        style: Style {
                            flex_direction: FlexDirection::Column,
                            align_items: AlignItems::Center,
                            ..default()
                        },
                        ..default()
                    },
                    ScrollingList::default(),
                    AccessibilityNode(NodeBuilder::new(Role::List)),
                ).with_children({
                    // List items
                    let mut children = Vec::new();
                    for i in 0..30 {
                        children.push(BundleTree::new((
                            TextBundle::from_section(
                                format!("Item {i}"),
                                TextStyle {
                                    font: asset_server
                                        .load("fonts/FiraSans-Bold.ttf"),
                                    font_size: 20.,
                                    ..default()
                                },
                            ),
                            Label,
                            AccessibilityNode(NodeBuilder::new(Role::ListItem)),
                        )));
                    }
                    children
                })
            ])
        ]),
        // Node
        NodeBundle {
            style: Style {
                width: Val::Px(200.0),
                height: Val::Px(200.0),
                position_type: PositionType::Absolute,
                left: Val::Px(210.),
                bottom: Val::Px(10.),
                border: UiRect::all(Val::Px(20.)),
                ..default()
            },
            border_color: GREEN.into(),
            background_color: Color::srgb(0.4, 0.4, 1.).into(),
            ..default()
        }.with_children([
            BundleTree::new(NodeBundle {
                style: Style {
                    width: Val::Percent(100.0),
                    height: Val::Percent(100.0),
                    ..default()
                },
                background_color: Color::srgb(0.8, 0.8, 1.).into(),
                ..default()
            })
        ]),
        // Render order test: reddest in the back, whitest in the front (flex center)
        NodeBundle {
            style: Style {
                width: Val::Percent(100.0),
                height: Val::Percent(100.0),
                position_type: PositionType::Absolute,
                align_items: AlignItems::Center,
                justify_content: JustifyContent::Center,
                ..default()
            },
            ..default()
        }.with_children([
            NodeBundle {
                style: Style {
                    width: Val::Px(100.0),
                    height: Val::Px(100.0),
                    ..default()
                },
                background_color: Color::srgb(1.0, 0.0, 0.).into(),
                ..default()
            }.with_children([
                NodeBundle {
                    style: Style {
                        // Take the size of the parent node.
                        width: Val::Percent(100.0),
                        height: Val::Percent(100.0),
                        position_type: PositionType::Absolute,
                        left: Val::Px(20.),
                        bottom: Val::Px(20.),
                        ..default()
                    },
                    background_color: Color::srgb(1.0, 0.3, 0.3).into(),
                    ..default()
                }.into_tree(),
                NodeBundle {
                    style: Style {
                        width: Val::Percent(100.0),
                        height: Val::Percent(100.0),
                        position_type: PositionType::Absolute,
                        left: Val::Px(40.),
                        bottom: Val::Px(40.),
                        ..default()
                    },
                    background_color: Color::srgb(1.0, 0.5, 0.5).into(),
                    ..default()
                }.into_tree(),
                NodeBundle {
                    style: Style {
                        width: Val::Percent(100.0),
                        height: Val::Percent(100.0),
                        position_type: PositionType::Absolute,
                        left: Val::Px(60.),
                        bottom: Val::Px(60.),
                        ..default()
                    },
                    background_color: Color::srgb(1.0, 0.7, 0.7).into(),
                    ..default()
                }.into_tree(),
                // Alpha test
                NodeBundle {
                    style: Style {
                        width: Val::Percent(100.0),
                        height: Val::Percent(100.0),
                        position_type: PositionType::Absolute,
                        left: Val::Px(80.),
                        bottom: Val::Px(80.),
                        ..default()
                    },
                    background_color: Color::srgba(1.0, 0.9, 0.9, 0.4).into(),
                    ..default()
                }.into_tree()
            ])
        ]),
        // Bevy logo (flex center)
        NodeBundle {
            style: Style {
                width: Val::Percent(100.0),
                position_type: PositionType::Absolute,
                justify_content: JustifyContent::Center,
                align_items: AlignItems::FlexStart,
                ..default()
            },
            ..default()
        }.with_children([
            // Bevy logo (image)
            // A `NodeBundle` is used to display the logo the image as an `ImageBundle` can't automatically
            // size itself with a child node present.
            (
                NodeBundle {
                    style: Style {
                        width: Val::Px(500.0),
                        height: Val::Px(125.0),
                        margin: UiRect::top(Val::VMin(5.)),
                        ..default()
                    },
                    // a `NodeBundle` is transparent by default, so to see the image we have to its color to `WHITE`
                    background_color: Color::WHITE.into(),
                    ..default()
                },
                UiImage::new(asset_server.load("branding/bevy_logo_dark_big.png"))
            ).with_children([
                // Alt text
                // This UI node takes up no space in the layout and the `Text` component is used by the accessibility module
                // and is not rendered.
                (
                    NodeBundle {
                        style: Style {
                            display: Display::None,
                            ..Default::default()
                        },
                        ..Default::default()
                    },
                    Text::from_section("Bevy logo", TextStyle::default()),
                ).into_tree()
        ])])
    ]);
    commands.spawn_tree(tree);
}

#[derive(Component, Default)]
struct ScrollingList {
    position: f32,
}

fn mouse_scroll(
    mut mouse_wheel_events: EventReader<MouseWheel>,
    mut query_list: Query<(&mut ScrollingList, &mut Style, &Parent, &Node)>,
    query_node: Query<&Node>,
) {
    for mouse_wheel_event in mouse_wheel_events.read() {
        for (mut scrolling_list, mut style, parent, list_node) in &mut query_list {
            let items_height = list_node.size().y;
            let container_height = query_node.get(parent.get()).unwrap().size().y;

            let max_scroll = (items_height - container_height).max(0.);

            let dy = match mouse_wheel_event.unit {
                MouseScrollUnit::Line => mouse_wheel_event.y * 20.,
                MouseScrollUnit::Pixel => mouse_wheel_event.y,
            };

            scrolling_list.position += dy;
            scrolling_list.position = scrolling_list.position.clamp(-max_scroll, 0.);
            style.top = Val::Px(scrolling_list.position);
        }
    }
}