use bevy::input::mouse::{MouseScrollUnit, MouseWheel};
use bevy::prelude::*;
use bevy::window::PrimaryWindow;

pub fn input_plugin(app: &mut App) {
    app
        .insert_resource(ShipEditorDrag::default())
        .add_systems(Update, on_scroll)
        .add_systems(Update, on_click)
        .add_systems(Update, drag);
}

#[derive(Resource, Default)]
struct ShipEditorDrag {
    is_dragging: bool,
    init_cursor_pos: Vec2,
    init_camera_pos: Vec2,
}

fn on_scroll(
    mut scroll_events: MessageReader<MouseWheel>,
    mut camera: Single<(&mut Transform, &mut Projection), With<Camera2d>>,
    window: Single<&Window, With<PrimaryWindow>>,
) {
    let Some(cursor_pos) = window.cursor_position() else { return };
    let cursor_pos = cursor_pos.with_y(-cursor_pos.y);

    let mut transform = camera.0.clone();
    let Projection::Orthographic(ref mut projection) = *camera.1 else { return };
    for ev in scroll_events.read() {
        match ev.unit {
            MouseScrollUnit::Line | MouseScrollUnit::Pixel => {
                if ev.y > 0.0 {
                    let mut rel_pos = vec2(window.width() / 2.0, -window.height() / 2.0) - cursor_pos;
                    rel_pos *= projection.scale;
                    projection.scale *= 0.95;
                    let scaled_rel_pos = rel_pos * 0.95;
                    transform.translation += scaled_rel_pos.extend(0.0) - rel_pos.extend(0.0);
                } else {
                    let mut rel_pos = vec2(window.width() / 2.0, -window.height() / 2.0) - cursor_pos;
                    rel_pos *= projection.scale;
                    projection.scale *= 1.05;
                    let scaled_rel_pos = rel_pos * 1.05;
                    transform.translation += scaled_rel_pos.extend(0.0) - rel_pos.extend(0.0);
                }
            }
        }
    }
    *camera.0 = transform;
}

fn on_click(
    ev: Res<ButtonInput<MouseButton>>,
    mut drag: ResMut<ShipEditorDrag>,
    camera: Single<&Transform, With<Camera2d>>,
    window: Single<&Window, With<PrimaryWindow>>,
) {
    let Some(cursor_pos) = window.cursor_position() else { return };
    if ev.just_pressed(MouseButton::Left) {
        drag.is_dragging = true;
        drag.init_cursor_pos = cursor_pos.with_y(-cursor_pos.y);
        drag.init_camera_pos = camera.translation.truncate();
    }
    if ev.just_released(MouseButton::Left) {
        drag.is_dragging = false;
    }
}

fn drag(
    drag: ResMut<ShipEditorDrag>,
    mut camera: Single<(&mut Transform, &Projection), With<Camera2d>>,
    window: Single<&Window, With<PrimaryWindow>>,
) {
    if !drag.is_dragging { return }
    let Some(cursor) = window.cursor_position() else { return };
    let projection = camera.1.clone();
    let Projection::Orthographic(projection) = projection else { return };
    let transform = &mut camera.0;

    transform.translation = drag.init_camera_pos.extend(0.0) - (cursor.with_y(-cursor.y) - drag.init_cursor_pos).extend(0.0)*projection.scale;
}