From 3084d02f6605b98bba32d9b1384af038014e1fb1 Mon Sep 17 00:00:00 2001
From: Nolan Darilek <nolan@thewordnerd.info>
Date: Wed, 26 May 2021 14:57:55 -0500
Subject: [PATCH] Separate viewshed updates based on coordinate and
 visibility_blocked.

---
 src/visibility.rs | 116 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 91 insertions(+), 25 deletions(-)

diff --git a/src/visibility.rs b/src/visibility.rs
index ecaba02..26ff09b 100644
--- a/src/visibility.rs
+++ b/src/visibility.rs
@@ -23,7 +23,7 @@ pub struct DontLogWhenVisible;
 #[reflect(Component)]
 pub struct RevealedTiles(pub Vec<bool>);
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub struct Viewshed {
     pub visible: HashSet<(i32, i32)>,
     pub range: u32,
@@ -100,11 +100,11 @@ pub(crate) fn set_visibility_blocked(
 }
 
 #[derive(Default, Deref, DerefMut)]
-struct PreviousIndex(HashMap<Entity, usize>);
+struct PrevIndex(HashMap<Entity, usize>);
 
 fn map_visibility_indexing(
     mut map: Query<(&Map, &mut VisibilityBlocked)>,
-    mut prev_index: ResMut<PreviousIndex>,
+    mut prev_index: ResMut<PrevIndex>,
     query: Query<
         (Entity, &Coordinates),
         (
@@ -135,7 +135,7 @@ fn map_visibility_indexing(
 }
 
 fn remove_blocks_visibility(
-    mut prev_index: ResMut<PreviousIndex>,
+    mut prev_index: ResMut<PrevIndex>,
     mut map: Query<(&Map, &mut VisibilityBlocked)>,
     removed: RemovedComponents<BlocksVisibility>,
     coordinates: Query<&Coordinates>,
@@ -184,33 +184,89 @@ impl InputGrid for VisibilityGrid {
 }
 
 fn update_viewshed(
-    mut viewers: Query<
-        (&mut Viewshed, &Coordinates),
-        Or<(Changed<VisibilityBlocked>, Changed<Coordinates>)>,
-    >,
+    viewshed: &mut Viewshed,
+    start: &Coordinates,
+    map: &Map,
+    visibility_blocked: &VisibilityBlocked,
+) {
+    let mut context: Context<u8> = Context::default();
+    let vision_distance = vision_distance::Circle::new(viewshed.range);
+    let coord = Coord::new(start.x_i32(), start.y_i32());
+    viewshed.visible.clear();
+    let visibility_grid = VisibilityGrid(map.clone(), visibility_blocked.clone());
+    context.for_each_visible(
+        coord,
+        &visibility_grid,
+        &visibility_grid,
+        vision_distance,
+        255,
+        |coord, _directions, _visibility| {
+            viewshed.visible.insert((coord.x, coord.y));
+        },
+    );
+}
+
+fn update_viewshed_for_coordinates(
+    mut viewers: Query<(&mut Viewshed, &Coordinates), Changed<Coordinates>>,
     map: Query<(&Map, &VisibilityBlocked)>,
 ) {
     for (mut viewshed, start) in viewers.iter_mut() {
         for (map, visibility_blocked) in map.iter() {
-            let mut context: Context<u8> = Context::default();
-            let vision_distance = vision_distance::Circle::new(viewshed.range);
-            let coord = Coord::new(start.x_i32(), start.y_i32());
-            viewshed.visible.clear();
-            let visibility_grid = VisibilityGrid(map.clone(), visibility_blocked.clone());
-            context.for_each_visible(
-                coord,
-                &visibility_grid,
-                &visibility_grid,
-                vision_distance,
-                255,
-                |coord, _directions, _visibility| {
-                    viewshed.visible.insert((coord.x, coord.y));
-                },
-            );
+            update_viewshed(&mut viewshed, start, &map, &visibility_blocked);
         }
     }
 }
 
+#[derive(Clone, Debug, Default, Deref, DerefMut)]
+struct PrevVisibilityBlocked(Vec<bool>);
+
+fn visibility_blocked_added(mut prev_visibility_blocked: ResMut<PrevVisibilityBlocked>, added: Query<&VisibilityBlocked, Added<VisibilityBlocked>>) {
+    for visibility_blocked in added.iter() {
+        **prev_visibility_blocked = visibility_blocked.to_vec();
+    }
+}
+
+fn visibility_blocked_removed(mut prev_visibility_blocked: ResMut<PrevVisibilityBlocked>, removed: RemovedComponents<VisibilityBlocked>) {
+    for _ in removed.iter() {
+        prev_visibility_blocked.clear();
+    }
+}
+
+fn update_viewshed_for_visibility_blocked(
+    mut prev_visibility_blocked: ResMut<PrevVisibilityBlocked>,
+    map: Query<(&Map, &VisibilityBlocked), Changed<VisibilityBlocked>>,
+    mut queryset: QuerySet<(
+        Query<(Entity, &Viewshed)>,
+        Query<(&mut Viewshed, &Coordinates)>,
+    )>,
+) {
+    for (map, visibility_blocked) in map.iter() {
+        let mut to_check = vec![];
+        for (index, new) in visibility_blocked.iter().enumerate() {
+            let changed = if let Some(prev) = prev_visibility_blocked.get(index) {
+                prev != new
+            } else {
+                true
+            };
+            if changed {
+                let coords = (index % map.width(), index / map.width());
+                for (entity, viewshed) in queryset.q0().iter() {
+                    if viewshed.is_visible(&coords) {
+                        to_check.push(entity);
+                    }
+                }
+            }
+        }
+        to_check.dedup();
+        for entity in to_check {
+            if let Ok((mut viewshed, coordinates)) = queryset.q1_mut().get_mut(entity) {
+                update_viewshed(&mut viewshed, coordinates, &map, &visibility_blocked);
+            }
+        }
+        **prev_visibility_blocked = visibility_blocked.to_vec();
+    }
+}
+
 fn update_visible_and_revealed_tiles(
     mut map: Query<
         (&Map, &mut RevealedTiles, &mut VisibleTiles),
@@ -301,7 +357,10 @@ impl Plugin for VisibilityPlugin {
         const UPDATE_VISIBILITY_INDEX: &str = "UPDATE_VISIBILITY_INDEX";
         const UPDATE_VIEWSHED: &str = "UPDATE_VIEWSHED";
         const MAP_VISIBILITY: &str = "MAP_VISIBILITY";
-        app.insert_resource(PreviousIndex::default())
+        app.init_resource::<PrevVisibilityBlocked>()
+            .init_resource::<PrevIndex>()
+            .add_system(visibility_blocked_added.system())
+            .add_system_to_stage(CoreStage::PostUpdate, visibility_blocked_removed.system())
             .add_system(add_visibility_indices.system())
             .add_system_to_stage(
                 CoreStage::PostUpdate,
@@ -324,7 +383,14 @@ impl Plugin for VisibilityPlugin {
             )
             .add_system_to_stage(
                 CoreStage::PostUpdate,
-                update_viewshed
+                update_viewshed_for_coordinates
+                    .system()
+                    .label(UPDATE_VIEWSHED)
+                    .after(UPDATE_VISIBILITY_INDEX),
+            )
+            .add_system_to_stage(
+                CoreStage::PostUpdate,
+                update_viewshed_for_visibility_blocked
                     .system()
                     .label(UPDATE_VIEWSHED)
                     .after(UPDATE_VISIBILITY_INDEX),