From 3c20e8ed4eb5ee934528e6d0d447bb355b92465d Mon Sep 17 00:00:00 2001
From: Ben Wallis <atomyc@gmail.com>
Date: Wed, 28 Apr 2021 22:26:09 +0100
Subject: [PATCH] Reduced sync of TimeOfDay to once per 100 ticks

---
 client/src/lib.rs             | 18 ++++++++++++++----
 server/src/cmd.rs             | 11 +++++++++++
 server/src/sys/entity_sync.rs | 19 +++++++++++--------
 3 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/client/src/lib.rs b/client/src/lib.rs
index a9e1fc582a..a7ef53d2bd 100644
--- a/client/src/lib.rs
+++ b/client/src/lib.rs
@@ -34,7 +34,7 @@ use common::{
     grid::Grid,
     outcome::Outcome,
     recipe::RecipeBook,
-    resources::{DeltaTime, PlayerEntity, TimeOfDay},
+    resources::{PlayerEntity, TimeOfDay},
     terrain::{
         block::Block, map::MapConfig, neighbors, BiomeKind, SitesKind, SpriteKind, TerrainChunk,
         TerrainChunkSize,
@@ -190,6 +190,7 @@ pub struct Client {
     loaded_distance: f32,
 
     pending_chunks: HashMap<Vec2<i32>, Instant>,
+    target_time_of_day: Option<TimeOfDay>,
 }
 
 /// Holds data related to the current players characters, as well as some
@@ -693,6 +694,7 @@ impl Client {
             loaded_distance: 0.0,
 
             pending_chunks: HashMap::new(),
+            target_time_of_day: None,
         })
     }
 
@@ -1449,6 +1451,16 @@ impl Client {
             self.invite = None;
         }
 
+        // Lerp towards the target time of day - this ensures a smooth transition for
+        // large jumps in TimeOfDay such as when using /time
+        if let Some(target_tod) = self.target_time_of_day {
+            let mut tod = self.state.ecs_mut().write_resource::<TimeOfDay>();
+            tod.0 = Lerp::lerp(tod.0, target_tod.0, dt.as_secs_f64());
+            if tod.0 >= target_tod.0 {
+                self.target_time_of_day = None;
+            }
+        }
+
         // 4) Tick the client's LocalState
         self.state.tick(
             dt,
@@ -1716,9 +1728,7 @@ impl Client {
                 }
             },
             ServerGeneral::TimeOfDay(time_of_day) => {
-                let dt = self.state.ecs().read_resource::<DeltaTime>().0;
-                let mut tod = self.state.ecs_mut().write_resource::<TimeOfDay>();
-                tod.0 = Lerp::lerp(tod.0, time_of_day.0, dt as f64);
+                self.target_time_of_day = Some(time_of_day);
             },
             ServerGeneral::EntitySync(entity_sync_package) => {
                 self.state
diff --git a/server/src/cmd.rs b/server/src/cmd.rs
index 9c24866507..47081c6a48 100644
--- a/server/src/cmd.rs
+++ b/server/src/cmd.rs
@@ -714,6 +714,17 @@ fn handle_time(
 
     server.state.mut_resource::<TimeOfDay>().0 = new_time;
 
+    // Update all clients with the new TimeOfDay (without this they would have to
+    // wait for the next 100th tick to receive the update).
+    let mut tod_lazymsg = None;
+    let clients = server.state.ecs().read_storage::<Client>();
+    for client in (&clients).join() {
+        let msg = tod_lazymsg
+            .unwrap_or_else(|| client.prepare(ServerGeneral::TimeOfDay(TimeOfDay(new_time))));
+        let _ = client.send_prepared(&msg);
+        tod_lazymsg = Some(msg);
+    }
+
     if let Some(new_time) =
         NaiveTime::from_num_seconds_from_midnight_opt(((new_time as u64) % 86400) as u32, 0)
     {
diff --git a/server/src/sys/entity_sync.rs b/server/src/sys/entity_sync.rs
index 12a33c4570..964df88283 100644
--- a/server/src/sys/entity_sync.rs
+++ b/server/src/sys/entity_sync.rs
@@ -356,14 +356,17 @@ impl<'a> System<'a> for Sys {
         // Sync resources
         // TODO: doesn't really belong in this system (rename system or create another
         // system?)
-        let mut tof_lazymsg = None;
-        for client in (&clients).join() {
-            let msg = tof_lazymsg
-                .unwrap_or_else(|| client.prepare(ServerGeneral::TimeOfDay(*time_of_day)));
-            // We don't care much about stream errors here since they could just represent
-            // network disconnection, which is handled elsewhere.
-            let _ = client.send_prepared(&msg);
-            tof_lazymsg = Some(msg);
+        const TOD_SYNC_FREQ: u64 = 100;
+        if tick % TOD_SYNC_FREQ == 0 {
+            let mut tod_lazymsg = None;
+            for client in (&clients).join() {
+                let msg = tod_lazymsg
+                    .unwrap_or_else(|| client.prepare(ServerGeneral::TimeOfDay(*time_of_day)));
+                // We don't care much about stream errors here since they could just represent
+                // network disconnection, which is handled elsewhere.
+                let _ = client.send_prepared(&msg);
+                tod_lazymsg = Some(msg);
+            }
         }
     }
 }