//! Components to customize winit cursor

use crate::{
    converters::convert_system_cursor_icon,
    state::{CursorSource, PendingCursor},
};
#[cfg(feature = "custom_cursor")]
use crate::{
    custom_cursor::{
        calculate_effective_rect, extract_and_transform_rgba_pixels, extract_rgba_pixels,
        transform_hotspot, CustomCursorPlugin,
    },
    state::{CustomCursorCache, CustomCursorCacheKey},
    WinitCustomCursor,
};
use bevy_app::{App, Last, Plugin};
#[cfg(feature = "custom_cursor")]
use bevy_asset::Assets;
#[cfg(feature = "custom_cursor")]
use bevy_ecs::system::Res;
use bevy_ecs::{
    change_detection::DetectChanges,
    component::Component,
    entity::Entity,
    observer::Trigger,
    query::With,
    reflect::ReflectComponent,
    system::{Commands, Local, Query},
    world::{OnRemove, Ref},
};
#[cfg(feature = "custom_cursor")]
use bevy_image::{Image, TextureAtlasLayout};
use bevy_platform_support::collections::HashSet;
use bevy_reflect::{std_traits::ReflectDefault, Reflect};
use bevy_window::{SystemCursorIcon, Window};
#[cfg(feature = "custom_cursor")]
use tracing::warn;

#[cfg(feature = "custom_cursor")]
pub use crate::custom_cursor::{CustomCursor, CustomCursorImage};

pub(crate) struct CursorPlugin;

impl Plugin for CursorPlugin {
    fn build(&self, app: &mut App) {
        #[cfg(feature = "custom_cursor")]
        app.add_plugins(CustomCursorPlugin);

        app.register_type::<CursorIcon>()
            .add_systems(Last, update_cursors);

        app.add_observer(on_remove_cursor_icon);
    }
}

/// Insert into a window entity to set the cursor for that window.
#[derive(Component, Debug, Clone, Reflect, PartialEq, Eq)]
#[reflect(Component, Debug, Default, PartialEq)]
pub enum CursorIcon {
    #[cfg(feature = "custom_cursor")]
    /// Custom cursor image.
    Custom(CustomCursor),
    /// System provided cursor icon.
    System(SystemCursorIcon),
}

impl Default for CursorIcon {
    fn default() -> Self {
        CursorIcon::System(Default::default())
    }
}

impl From<SystemCursorIcon> for CursorIcon {
    fn from(icon: SystemCursorIcon) -> Self {
        CursorIcon::System(icon)
    }
}

fn update_cursors(
    mut commands: Commands,
    windows: Query<(Entity, Ref<CursorIcon>), With<Window>>,
    #[cfg(feature = "custom_cursor")] cursor_cache: Res<CustomCursorCache>,
    #[cfg(feature = "custom_cursor")] images: Res<Assets<Image>>,
    #[cfg(feature = "custom_cursor")] texture_atlases: Res<Assets<TextureAtlasLayout>>,
    mut queue: Local<HashSet<Entity>>,
) {
    for (entity, cursor) in windows.iter() {
        if !(queue.remove(&entity) || cursor.is_changed()) {
            continue;
        }

        let cursor_source = match cursor.as_ref() {
            #[cfg(feature = "custom_cursor")]
            CursorIcon::Custom(CustomCursor::Image(c)) => {
                let CustomCursorImage {
                    handle,
                    texture_atlas,
                    flip_x,
                    flip_y,
                    rect,
                    hotspot,
                } = c;

                let cache_key = CustomCursorCacheKey::Image {
                    id: handle.id(),
                    texture_atlas_layout_id: texture_atlas.as_ref().map(|a| a.layout.id()),
                    texture_atlas_index: texture_atlas.as_ref().map(|a| a.index),
                    flip_x: *flip_x,
                    flip_y: *flip_y,
                    rect: *rect,
                };

                if cursor_cache.0.contains_key(&cache_key) {
                    CursorSource::CustomCached(cache_key)
                } else {
                    let Some(image) = images.get(handle) else {
                        warn!(
                            "Cursor image {handle:?} is not loaded yet and couldn't be used. Trying again next frame."
                        );
                        queue.insert(entity);
                        continue;
                    };

                    let (rect, needs_sub_image) =
                        calculate_effective_rect(&texture_atlases, image, texture_atlas, rect);

                    let (maybe_rgba, hotspot) = if *flip_x || *flip_y || needs_sub_image {
                        (
                            extract_and_transform_rgba_pixels(image, *flip_x, *flip_y, rect),
                            transform_hotspot(*hotspot, *flip_x, *flip_y, rect),
                        )
                    } else {
                        (extract_rgba_pixels(image), *hotspot)
                    };

                    let Some(rgba) = maybe_rgba else {
                        warn!("Cursor image {handle:?} not accepted because it's not rgba8 or rgba32float format");
                        continue;
                    };

                    let source = match WinitCustomCursor::from_rgba(
                        rgba,
                        rect.width() as u16,
                        rect.height() as u16,
                        hotspot.0,
                        hotspot.1,
                    ) {
                        Ok(source) => source,
                        Err(err) => {
                            warn!("Cursor image {handle:?} is invalid: {err}");
                            continue;
                        }
                    };

                    CursorSource::Custom((cache_key, source))
                }
            }
            #[cfg(all(
                feature = "custom_cursor",
                target_family = "wasm",
                target_os = "unknown"
            ))]
            CursorIcon::Custom(CustomCursor::Url(c)) => {
                let cache_key = CustomCursorCacheKey::Url(c.url.clone());

                if cursor_cache.0.contains_key(&cache_key) {
                    CursorSource::CustomCached(cache_key)
                } else {
                    use crate::CustomCursorExtWebSys;
                    let source =
                        WinitCustomCursor::from_url(c.url.clone(), c.hotspot.0, c.hotspot.1);
                    CursorSource::Custom((cache_key, source))
                }
            }
            CursorIcon::System(system_cursor_icon) => {
                CursorSource::System(convert_system_cursor_icon(*system_cursor_icon))
            }
        };

        commands
            .entity(entity)
            .insert(PendingCursor(Some(cursor_source)));
    }
}

/// Resets the cursor to the default icon when `CursorIcon` is removed.
fn on_remove_cursor_icon(trigger: Trigger<OnRemove, CursorIcon>, mut commands: Commands) {
    // Use `try_insert` to avoid panic if the window is being destroyed.
    commands
        .entity(trigger.target())
        .try_insert(PendingCursor(Some(CursorSource::System(
            convert_system_cursor_icon(SystemCursorIcon::Default),
        ))));
}