Update source files

crates/borders-core/src/ui/mod.rs

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+//! UI/Frontend module for rendering and user interaction
+//!
+//! This module contains all frontend-related concerns including:
+//! - Protocol definitions for frontend-backend communication
+//! - Input handling
+//! - Leaderboard management
+//! - Platform transport abstraction
+
+use std::collections::{HashMap, HashSet};
+use std::sync::{Arc, Mutex};
+
+use bevy_ecs::hierarchy::ChildOf;
+use bevy_ecs::prelude::*;
+
+use crate::game::systems::turn::CurrentTurn;
+use crate::game::{NationId, Ship, TerritoryManager};
+
+pub mod input;
+pub mod leaderboard;
+pub mod plugin;
+pub mod protocol;
+pub mod transport;
+
+// Re-export commonly used types
+pub use input::*;
+pub use leaderboard::*;
+pub use plugin::*;
+pub use protocol::*;
+pub use transport::*;
+
+/// Resource to track currently highlighted nation for visual feedback
+#[derive(Resource, Default, Debug)]
+pub struct NationHighlightState {
+    pub highlighted_nation: Option<NationId>,
+}
+
+/// System that tracks hovered nation and emits highlight events
+pub fn emit_nation_highlight_system(input_state: If<NonSend<Arc<Mutex<InputState>>>>, territory_manager: Option<Res<TerritoryManager>>, mut highlight_state: If<ResMut<NationHighlightState>>, mut backend_messages: MessageWriter<BackendMessage>) {
+    let Ok(input) = input_state.lock() else {
+        return;
+    };
+
+    let Some(territory_manager) = territory_manager else {
+        return;
+    };
+
+    let new_highlighted = if let Some(tile_coord) = input.cursor_tile() {
+        let ownership = territory_manager.get_ownership(tile_coord);
+        ownership.nation_id()
+    } else {
+        None
+    };
+
+    // Only emit if highlight changed
+    if new_highlighted != highlight_state.highlighted_nation {
+        highlight_state.highlighted_nation = new_highlighted;
+        backend_messages.write(BackendMessage::HighlightNation { nation_id: new_highlighted });
+    }
+}
+
+/// Resource to track previous ship states for delta updates
+#[derive(Resource, Default)]
+pub struct ShipStateTracker {
+    /// Map of ship ID to current_path_index
+    ship_indices: HashMap<u32, u32>,
+}
+
+/// System that emits ship update variants to the frontend (delta-based)
+/// - Create: sent when ship first appears
+/// - Move: sent only when current_path_index changes
+/// - Destroy: sent when ship disappears
+pub fn emit_ships_update_system(current_turn: Option<Res<CurrentTurn>>, territory_manager: Option<Res<TerritoryManager>>, ships: Query<(&Ship, &ChildOf)>, player_query: Query<&NationId>, mut ship_tracker: ResMut<ShipStateTracker>, mut backend_messages: MessageWriter<BackendMessage>) {
+    let Some(current_turn) = current_turn else {
+        return;
+    };
+
+    let Some(territory_manager) = territory_manager else {
+        return;
+    };
+
+    let current_ship_ids: HashSet<u32> = ships.iter().map(|(ship, _)| ship.id).collect();
+
+    let mut updates = Vec::new();
+
+    // Detect destroyed ships
+    for &ship_id in ship_tracker.ship_indices.keys() {
+        if !current_ship_ids.contains(&ship_id) {
+            updates.push(ShipUpdateVariant::Destroy { id: ship_id });
+        }
+    }
+
+    // Detect new ships and moved ships
+    for (ship, parent) in ships.iter() {
+        let owner_id = player_query.get(parent.0).copied().unwrap_or(NationId::ZERO);
+
+        // Convert path from U16Vec2 to tile indices
+        let path: Vec<u32> = ship.path.iter().map(|pos| territory_manager.pos_to_index(*pos)).collect();
+
+        match ship_tracker.ship_indices.get(&ship.id) {
+            None => {
+                // New ship - send Create
+                updates.push(ShipUpdateVariant::Create { id: ship.id, owner_id, path, troops: ship.troops });
+                ship_tracker.ship_indices.insert(ship.id, ship.current_path_index as u32);
+            }
+            Some(&prev_index) if prev_index != ship.current_path_index as u32 => {
+                // Ship moved to next tile - send Move
+                updates.push(ShipUpdateVariant::Move { id: ship.id, current_path_index: ship.current_path_index as u32 });
+                ship_tracker.ship_indices.insert(ship.id, ship.current_path_index as u32);
+            }
+            _ => {
+                // No change, do nothing
+            }
+        }
+    }
+
+    // Clean up destroyed ships from tracker
+    ship_tracker.ship_indices.retain(|id, _| current_ship_ids.contains(id));
+
+    // Only send if there are updates
+    if !updates.is_empty() {
+        backend_messages.write(BackendMessage::ShipsUpdate(ShipsUpdatePayload { turn: current_turn.turn.turn_number, updates }));
+    }
+}