From 96940f0527c3f073f61475ce717fc11a927b2b3a Mon Sep 17 00:00:00 2001
From: Damien Elmes <gpg@ankiweb.net>
Date: Tue, 9 Mar 2021 10:58:55 +1000
Subject: [PATCH] undo support for config entries

---
 rslib/src/collection.rs                |   2 +-
 rslib/src/config/bool.rs               |   2 +-
 rslib/src/config/deck.rs               |   6 +-
 rslib/src/config/mod.rs                |  60 +++++++++----
 rslib/src/config/notetype.rs           |   4 +-
 rslib/src/config/string.rs             |   2 +-
 rslib/src/config/undo.rs               | 111 +++++++++++++++++++++++++
 rslib/src/dbcheck.rs                   |   2 +-
 rslib/src/notetype/cardgen.rs          |   7 +-
 rslib/src/notetype/stock.rs            |  15 ++--
 rslib/src/scheduler/answering/mod.rs   |   2 +-
 rslib/src/scheduler/mod.rs             |   8 +-
 rslib/src/stats/card.rs                |   2 +-
 rslib/src/stats/graphs.rs              |   4 +-
 rslib/src/stats/today.rs               |   7 +-
 rslib/src/storage/config/get_entry.sql |   5 ++
 rslib/src/storage/config/mod.rs        |  38 ++++++---
 rslib/src/sync/mod.rs                  |   4 +-
 rslib/src/undo/changes.rs              |  15 +++-
 19 files changed, 237 insertions(+), 59 deletions(-)
 create mode 100644 rslib/src/config/undo.rs
 create mode 100644 rslib/src/storage/config/get_entry.sql

diff --git a/rslib/src/collection.rs b/rslib/src/collection.rs
index 90db7fd8a..bb701f9b6 100644
--- a/rslib/src/collection.rs
+++ b/rslib/src/collection.rs
@@ -44,7 +44,7 @@ pub fn open_collection<P: Into<PathBuf>>(
 #[cfg(test)]
 pub fn open_test_collection() -> Collection {
     use crate::config::SchedulerVersion;
-    let col = open_test_collection_with_server(false);
+    let mut col = open_test_collection_with_server(false);
     // our unit tests assume v2 is the default, but at the time of writing v1
     // is still the default
     col.set_scheduler_version_config_key(SchedulerVersion::V2)
diff --git a/rslib/src/config/bool.rs b/rslib/src/config/bool.rs
index 150eeaacb..06f13e31e 100644
--- a/rslib/src/config/bool.rs
+++ b/rslib/src/config/bool.rs
@@ -61,7 +61,7 @@ impl Collection {
         }
     }
 
-    pub(crate) fn set_bool(&self, key: BoolKey, value: bool) -> Result<()> {
+    pub(crate) fn set_bool(&mut self, key: BoolKey, value: bool) -> Result<()> {
         self.set_config(key, &value)
     }
 }
diff --git a/rslib/src/config/deck.rs b/rslib/src/config/deck.rs
index b11b7b5ca..22c7b8694 100644
--- a/rslib/src/config/deck.rs
+++ b/rslib/src/config/deck.rs
@@ -34,7 +34,11 @@ impl Collection {
         self.get_config_optional(key.as_str())
     }
 
-    pub(crate) fn set_last_notetype_for_deck(&self, did: DeckID, ntid: NoteTypeID) -> Result<()> {
+    pub(crate) fn set_last_notetype_for_deck(
+        &mut self,
+        did: DeckID,
+        ntid: NoteTypeID,
+    ) -> Result<()> {
         let key = DeckConfigKey::LastNotetype.for_deck(did);
         self.set_config(key.as_str(), &ntid)
     }
diff --git a/rslib/src/config/mod.rs b/rslib/src/config/mod.rs
index a70553234..12c0ced95 100644
--- a/rslib/src/config/mod.rs
+++ b/rslib/src/config/mod.rs
@@ -6,6 +6,7 @@ mod deck;
 mod notetype;
 pub(crate) mod schema11;
 mod string;
+pub(crate) mod undo;
 
 pub use self::{bool::BoolKey, string::StringKey};
 use crate::prelude::*;
@@ -15,6 +16,26 @@ use serde_repr::{Deserialize_repr, Serialize_repr};
 use slog::warn;
 use strum::IntoStaticStr;
 
+/// Only used when updating/undoing.
+#[derive(Debug)]
+pub(crate) struct ConfigEntry {
+    pub key: String,
+    pub value: Vec<u8>,
+    pub usn: Usn,
+    pub mtime: TimestampSecs,
+}
+
+impl ConfigEntry {
+    pub(crate) fn boxed(key: &str, value: Vec<u8>, usn: Usn, mtime: TimestampSecs) -> Box<Self> {
+        Box::new(Self {
+            key: key.into(),
+            value,
+            usn,
+            mtime,
+        })
+    }
+}
+
 #[derive(IntoStaticStr)]
 #[strum(serialize_all = "camelCase")]
 pub(crate) enum ConfigKey {
@@ -76,19 +97,24 @@ impl Collection {
         self.get_config_optional(key).unwrap_or_default()
     }
 
-    pub(crate) fn set_config<'a, T: Serialize, K>(&self, key: K, val: &T) -> Result<()>
+    pub(crate) fn set_config<'a, T: Serialize, K>(&mut self, key: K, val: &T) -> Result<()>
     where
         K: Into<&'a str>,
     {
-        self.storage
-            .set_config_value(key.into(), val, self.usn()?, TimestampSecs::now())
+        let entry = ConfigEntry::boxed(
+            key.into(),
+            serde_json::to_vec(val)?,
+            self.usn()?,
+            TimestampSecs::now(),
+        );
+        self.set_config_undoable(entry)
     }
 
-    pub(crate) fn remove_config<'a, K>(&self, key: K) -> Result<()>
+    pub(crate) fn remove_config<'a, K>(&mut self, key: K) -> Result<()>
     where
         K: Into<&'a str>,
     {
-        self.storage.remove_config(key.into())
+        self.remove_config_undoable(key.into())
     }
 
     /// Remove all keys starting with provided prefix, which must end with '_'.
@@ -107,7 +133,7 @@ impl Collection {
         self.get_config_optional(ConfigKey::CreationOffset)
     }
 
-    pub(crate) fn set_creation_utc_offset(&self, mins: Option<i32>) -> Result<()> {
+    pub(crate) fn set_creation_utc_offset(&mut self, mins: Option<i32>) -> Result<()> {
         if let Some(mins) = mins {
             self.set_config(ConfigKey::CreationOffset, &mins)
         } else {
@@ -119,7 +145,7 @@ impl Collection {
         self.get_config_optional(ConfigKey::LocalOffset)
     }
 
-    pub(crate) fn set_configured_utc_offset(&self, mins: i32) -> Result<()> {
+    pub(crate) fn set_configured_utc_offset(&mut self, mins: i32) -> Result<()> {
         self.set_config(ConfigKey::LocalOffset, &mins)
     }
 
@@ -128,7 +154,7 @@ impl Collection {
             .map(|r| r.min(23))
     }
 
-    pub(crate) fn set_v2_rollover(&self, hour: u32) -> Result<()> {
+    pub(crate) fn set_v2_rollover(&mut self, hour: u32) -> Result<()> {
         self.set_config(ConfigKey::Rollover, &hour)
     }
 
@@ -136,7 +162,7 @@ impl Collection {
         self.get_config_default(ConfigKey::NextNewCardPosition)
     }
 
-    pub(crate) fn get_and_update_next_card_position(&self) -> Result<u32> {
+    pub(crate) fn get_and_update_next_card_position(&mut self) -> Result<u32> {
         let pos: u32 = self
             .get_config_optional(ConfigKey::NextNewCardPosition)
             .unwrap_or_default();
@@ -144,7 +170,7 @@ impl Collection {
         Ok(pos)
     }
 
-    pub(crate) fn set_next_card_position(&self, pos: u32) -> Result<()> {
+    pub(crate) fn set_next_card_position(&mut self, pos: u32) -> Result<()> {
         self.set_config(ConfigKey::NextNewCardPosition, &pos)
     }
 
@@ -154,7 +180,7 @@ impl Collection {
     }
 
     /// Caution: this only updates the config setting.
-    pub(crate) fn set_scheduler_version_config_key(&self, ver: SchedulerVersion) -> Result<()> {
+    pub(crate) fn set_scheduler_version_config_key(&mut self, ver: SchedulerVersion) -> Result<()> {
         self.set_config(ConfigKey::SchedulerVersion, &ver)
     }
 
@@ -163,7 +189,7 @@ impl Collection {
             .unwrap_or(1200)
     }
 
-    pub(crate) fn set_learn_ahead_secs(&self, secs: u32) -> Result<()> {
+    pub(crate) fn set_learn_ahead_secs(&mut self, secs: u32) -> Result<()> {
         self.set_config(ConfigKey::LearnAheadSecs, &secs)
     }
 
@@ -175,7 +201,7 @@ impl Collection {
         }
     }
 
-    pub(crate) fn set_new_review_mix(&self, mix: NewReviewMix) -> Result<()> {
+    pub(crate) fn set_new_review_mix(&mut self, mix: NewReviewMix) -> Result<()> {
         self.set_config(ConfigKey::NewReviewMix, &(mix as u8))
     }
 
@@ -184,7 +210,7 @@ impl Collection {
             .unwrap_or(Weekday::Sunday)
     }
 
-    pub(crate) fn set_first_day_of_week(&self, weekday: Weekday) -> Result<()> {
+    pub(crate) fn set_first_day_of_week(&mut self, weekday: Weekday) -> Result<()> {
         self.set_config(ConfigKey::FirstDayOfWeek, &weekday)
     }
 
@@ -193,7 +219,7 @@ impl Collection {
             .unwrap_or_default()
     }
 
-    pub(crate) fn set_answer_time_limit_secs(&self, secs: u32) -> Result<()> {
+    pub(crate) fn set_answer_time_limit_secs(&mut self, secs: u32) -> Result<()> {
         self.set_config(ConfigKey::AnswerTimeLimitSecs, &secs)
     }
 
@@ -202,7 +228,7 @@ impl Collection {
             .unwrap_or_default()
     }
 
-    pub(crate) fn set_last_unburied_day(&self, day: u32) -> Result<()> {
+    pub(crate) fn set_last_unburied_day(&mut self, day: u32) -> Result<()> {
         self.set_config(ConfigKey::LastUnburiedDay, &day)
     }
 }
@@ -274,7 +300,7 @@ mod test {
 
     #[test]
     fn get_set() {
-        let col = open_test_collection();
+        let mut col = open_test_collection();
 
         // missing key
         assert_eq!(col.get_config_optional::<Vec<i64>, _>("test"), None);
diff --git a/rslib/src/config/notetype.rs b/rslib/src/config/notetype.rs
index 42b7d1e50..acda970da 100644
--- a/rslib/src/config/notetype.rs
+++ b/rslib/src/config/notetype.rs
@@ -28,7 +28,7 @@ impl Collection {
         self.get_config_optional(ConfigKey::CurrentNoteTypeID)
     }
 
-    pub(crate) fn set_current_notetype_id(&self, ntid: NoteTypeID) -> Result<()> {
+    pub(crate) fn set_current_notetype_id(&mut self, ntid: NoteTypeID) -> Result<()> {
         self.set_config(ConfigKey::CurrentNoteTypeID, &ntid)
     }
 
@@ -41,7 +41,7 @@ impl Collection {
         self.get_config_optional(key.as_str())
     }
 
-    pub(crate) fn set_last_deck_for_notetype(&self, id: NoteTypeID, did: DeckID) -> Result<()> {
+    pub(crate) fn set_last_deck_for_notetype(&mut self, id: NoteTypeID, did: DeckID) -> Result<()> {
         let key = NoteTypeConfigKey::LastDeckAddedTo.for_notetype(id);
         self.set_config(key.as_str(), &did)
     }
diff --git a/rslib/src/config/string.rs b/rslib/src/config/string.rs
index d39f371d8..d5aa918f8 100644
--- a/rslib/src/config/string.rs
+++ b/rslib/src/config/string.rs
@@ -22,7 +22,7 @@ impl Collection {
             .unwrap_or_else(|| default.to_string())
     }
 
-    pub(crate) fn set_string(&self, key: StringKey, val: &str) -> Result<()> {
+    pub(crate) fn set_string(&mut self, key: StringKey, val: &str) -> Result<()> {
         self.set_config(key, &val)
     }
 }
diff --git a/rslib/src/config/undo.rs b/rslib/src/config/undo.rs
new file mode 100644
index 000000000..1aec6d075
--- /dev/null
+++ b/rslib/src/config/undo.rs
@@ -0,0 +1,111 @@
+// Copyright: Ankitects Pty Ltd and contributors
+// License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
+
+use super::ConfigEntry;
+use crate::prelude::*;
+
+#[derive(Debug)]
+pub(crate) enum UndoableConfigChange {
+    Added(Box<ConfigEntry>),
+    Updated(Box<ConfigEntry>),
+    Removed(Box<ConfigEntry>),
+}
+
+impl Collection {
+    pub(crate) fn undo_config_change(&mut self, change: UndoableConfigChange) -> Result<()> {
+        match change {
+            UndoableConfigChange::Added(entry) => self.remove_config_undoable(&entry.key),
+            UndoableConfigChange::Updated(entry) => {
+                let current = self
+                    .storage
+                    .get_config_entry(&entry.key)?
+                    .ok_or_else(|| AnkiError::invalid_input("config disappeared"))?;
+                self.update_config_entry_undoable(entry, current)
+            }
+            UndoableConfigChange::Removed(entry) => self.add_config_entry_undoable(entry),
+        }
+    }
+
+    pub(super) fn set_config_undoable(&mut self, entry: Box<ConfigEntry>) -> Result<()> {
+        if let Some(original) = self.storage.get_config_entry(&entry.key)? {
+            self.update_config_entry_undoable(entry, original)
+        } else {
+            self.add_config_entry_undoable(entry)
+        }
+    }
+
+    pub(super) fn remove_config_undoable(&mut self, key: &str) -> Result<()> {
+        if let Some(current) = self.storage.get_config_entry(key)? {
+            self.save_undo(UndoableConfigChange::Removed(current));
+            self.storage.remove_config(key)?;
+        }
+
+        Ok(())
+    }
+
+    fn add_config_entry_undoable(&mut self, entry: Box<ConfigEntry>) -> Result<()> {
+        self.storage.set_config_entry(&entry)?;
+        self.save_undo(UndoableConfigChange::Added(entry));
+        Ok(())
+    }
+
+    fn update_config_entry_undoable(
+        &mut self,
+        entry: Box<ConfigEntry>,
+        original: Box<ConfigEntry>,
+    ) -> Result<()> {
+        if entry.value != original.value {
+            self.save_undo(UndoableConfigChange::Updated(original));
+            self.storage.set_config_entry(&entry)?;
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::collection::open_test_collection;
+
+    #[test]
+    fn undo() -> Result<()> {
+        let mut col = open_test_collection();
+        // the op kind doesn't matter, we just need undo enabled
+        let op = Some(UndoableOpKind::Bury);
+        // test key
+        let key = BoolKey::NormalizeNoteText;
+
+        // not set by default, but defaults to true
+        assert_eq!(col.get_bool(key), true);
+
+        // first set adds the key
+        col.transact(op, |col| col.set_bool(key, false))?;
+        assert_eq!(col.get_bool(key), false);
+
+        // mutate it twice
+        col.transact(op, |col| col.set_bool(key, true))?;
+        assert_eq!(col.get_bool(key), true);
+        col.transact(op, |col| col.set_bool(key, false))?;
+        assert_eq!(col.get_bool(key), false);
+
+        // when we remove it, it goes back to its default
+        col.transact(op, |col| col.remove_config(key))?;
+        assert_eq!(col.get_bool(key), true);
+
+        // undo the removal
+        col.undo()?;
+        assert_eq!(col.get_bool(key), false);
+
+        // undo the mutations
+        col.undo()?;
+        assert_eq!(col.get_bool(key), true);
+        col.undo()?;
+        assert_eq!(col.get_bool(key), false);
+
+        // and undo the initial add
+        col.undo()?;
+        assert_eq!(col.get_bool(key), true);
+
+        Ok(())
+    }
+}
diff --git a/rslib/src/dbcheck.rs b/rslib/src/dbcheck.rs
index e6c5e50d6..d5668d3a0 100644
--- a/rslib/src/dbcheck.rs
+++ b/rslib/src/dbcheck.rs
@@ -409,7 +409,7 @@ impl Collection {
         Ok(())
     }
 
-    fn update_next_new_position(&self) -> Result<()> {
+    fn update_next_new_position(&mut self) -> Result<()> {
         let pos = self.storage.max_new_card_position().unwrap_or(0);
         self.set_next_card_position(pos)
     }
diff --git a/rslib/src/notetype/cardgen.rs b/rslib/src/notetype/cardgen.rs
index 2e1993794..e89e37ffa 100644
--- a/rslib/src/notetype/cardgen.rs
+++ b/rslib/src/notetype/cardgen.rs
@@ -299,7 +299,12 @@ impl Collection {
 
     // not sure if entry() can be used due to get_deck_config() returning a result
     #[allow(clippy::map_entry)]
-    fn due_for_deck(&self, did: DeckID, dcid: DeckConfID, cache: &mut CardGenCache) -> Result<u32> {
+    fn due_for_deck(
+        &mut self,
+        did: DeckID,
+        dcid: DeckConfID,
+        cache: &mut CardGenCache,
+    ) -> Result<u32> {
         if !cache.deck_configs.contains_key(&did) {
             let conf = self.get_deck_config(dcid, true)?.unwrap();
             cache.deck_configs.insert(did, conf);
diff --git a/rslib/src/notetype/stock.rs b/rslib/src/notetype/stock.rs
index b124a398b..420cc1b5f 100644
--- a/rslib/src/notetype/stock.rs
+++ b/rslib/src/notetype/stock.rs
@@ -3,8 +3,13 @@
 
 use super::NoteTypeKind;
 use crate::{
-    config::ConfigKey, err::Result, i18n::I18n, i18n::TR, notetype::NoteType,
-    storage::SqliteStorage, timestamp::TimestampSecs,
+    config::{ConfigEntry, ConfigKey},
+    err::Result,
+    i18n::I18n,
+    i18n::TR,
+    notetype::NoteType,
+    storage::SqliteStorage,
+    timestamp::TimestampSecs,
 };
 
 use crate::backend_proto::stock_note_type::Kind;
@@ -14,12 +19,12 @@ impl SqliteStorage {
         for (idx, mut nt) in all_stock_notetypes(i18n).into_iter().enumerate() {
             self.add_new_notetype(&mut nt)?;
             if idx == Kind::Basic as usize {
-                self.set_config_value(
+                self.set_config_entry(&ConfigEntry::boxed(
                     ConfigKey::CurrentNoteTypeID.into(),
-                    &nt.id,
+                    serde_json::to_vec(&nt.id)?,
                     self.usn(false)?,
                     TimestampSecs::now(),
-                )?;
+                ))?;
             }
         }
         Ok(())
diff --git a/rslib/src/scheduler/answering/mod.rs b/rslib/src/scheduler/answering/mod.rs
index c4e80466a..3913bee97 100644
--- a/rslib/src/scheduler/answering/mod.rs
+++ b/rslib/src/scheduler/answering/mod.rs
@@ -193,7 +193,7 @@ impl Collection {
     }
 
     /// Describe the next intervals, to display on the answer buttons.
-    pub fn describe_next_states(&self, choices: NextCardStates) -> Result<Vec<String>> {
+    pub fn describe_next_states(&mut self, choices: NextCardStates) -> Result<Vec<String>> {
         let collapse_time = self.learn_ahead_secs();
         let now = TimestampSecs::now();
         let timing = self.timing_for_timestamp(now)?;
diff --git a/rslib/src/scheduler/mod.rs b/rslib/src/scheduler/mod.rs
index c5e678d43..01b1cda82 100644
--- a/rslib/src/scheduler/mod.rs
+++ b/rslib/src/scheduler/mod.rs
@@ -23,7 +23,7 @@ use timing::{
 };
 
 impl Collection {
-    pub fn timing_today(&self) -> Result<SchedTimingToday> {
+    pub fn timing_today(&mut self) -> Result<SchedTimingToday> {
         self.timing_for_timestamp(TimestampSecs::now())
     }
 
@@ -31,7 +31,7 @@ impl Collection {
         Ok(((self.timing_today()?.days_elapsed as i32) + delta).max(0) as u32)
     }
 
-    pub(crate) fn timing_for_timestamp(&self, now: TimestampSecs) -> Result<SchedTimingToday> {
+    pub(crate) fn timing_for_timestamp(&mut self, now: TimestampSecs) -> Result<SchedTimingToday> {
         let current_utc_offset = self.local_utc_offset_for_user()?;
 
         let rollover_hour = match self.scheduler_version() {
@@ -63,7 +63,7 @@ impl Collection {
     /// ensuring the config reflects the current value.
     /// In the server case, return the value set in the config, and
     /// fall back on UTC if it's missing/invalid.
-    pub(crate) fn local_utc_offset_for_user(&self) -> Result<FixedOffset> {
+    pub(crate) fn local_utc_offset_for_user(&mut self) -> Result<FixedOffset> {
         let config_tz = self
             .get_configured_utc_offset()
             .and_then(|v| FixedOffset::west_opt(v * 60))
@@ -99,7 +99,7 @@ impl Collection {
         }
     }
 
-    pub(crate) fn set_rollover_for_current_scheduler(&self, hour: u8) -> Result<()> {
+    pub(crate) fn set_rollover_for_current_scheduler(&mut self, hour: u8) -> Result<()> {
         match self.scheduler_version() {
             SchedulerVersion::V1 => {
                 self.storage
diff --git a/rslib/src/stats/card.rs b/rslib/src/stats/card.rs
index 549613e4a..f6d58e544 100644
--- a/rslib/src/stats/card.rs
+++ b/rslib/src/stats/card.rs
@@ -126,7 +126,7 @@ impl Collection {
         })
     }
 
-    fn card_stats_to_string(&self, cs: CardStats) -> Result<String> {
+    fn card_stats_to_string(&mut self, cs: CardStats) -> Result<String> {
         let offset = self.local_utc_offset_for_user()?;
         let i18n = &self.i18n;
 
diff --git a/rslib/src/stats/graphs.rs b/rslib/src/stats/graphs.rs
index 084d3a4b2..fb376541c 100644
--- a/rslib/src/stats/graphs.rs
+++ b/rslib/src/stats/graphs.rs
@@ -20,7 +20,7 @@ impl Collection {
         self.graph_data(all, days)
     }
 
-    fn graph_data(&self, all: bool, days: u32) -> Result<pb::GraphsOut> {
+    fn graph_data(&mut self, all: bool, days: u32) -> Result<pb::GraphsOut> {
         let timing = self.timing_today()?;
         let revlog_start = TimestampSecs(if days > 0 {
             timing.next_day_at - (((days as i64) + 1) * 86_400)
@@ -60,7 +60,7 @@ impl Collection {
         })
     }
 
-    pub(crate) fn set_graph_preferences(&self, prefs: pb::GraphPreferences) -> Result<()> {
+    pub(crate) fn set_graph_preferences(&mut self, prefs: pb::GraphPreferences) -> Result<()> {
         self.set_first_day_of_week(match prefs.calendar_first_day_of_week {
             1 => Weekday::Monday,
             5 => Weekday::Friday,
diff --git a/rslib/src/stats/today.rs b/rslib/src/stats/today.rs
index 3886dddfe..0a75d04c4 100644
--- a/rslib/src/stats/today.rs
+++ b/rslib/src/stats/today.rs
@@ -18,10 +18,9 @@ pub fn studied_today(cards: u32, secs: f32, i18n: &I18n) -> String {
 }
 
 impl Collection {
-    pub fn studied_today(&self) -> Result<String> {
-        let today = self
-            .storage
-            .studied_today(self.timing_today()?.next_day_at)?;
+    pub fn studied_today(&mut self) -> Result<String> {
+        let timing = self.timing_today()?;
+        let today = self.storage.studied_today(timing.next_day_at)?;
         Ok(studied_today(today.cards, today.seconds as f32, &self.i18n))
     }
 }
diff --git a/rslib/src/storage/config/get_entry.sql b/rslib/src/storage/config/get_entry.sql
new file mode 100644
index 000000000..be64ae323
--- /dev/null
+++ b/rslib/src/storage/config/get_entry.sql
@@ -0,0 +1,5 @@
+SELECT val,
+  usn,
+  mtime_secs
+FROM config
+WHERE KEY = ?
\ No newline at end of file
diff --git a/rslib/src/storage/config/mod.rs b/rslib/src/storage/config/mod.rs
index 832377a4b..d404002e4 100644
--- a/rslib/src/storage/config/mod.rs
+++ b/rslib/src/storage/config/mod.rs
@@ -2,24 +2,17 @@
 // License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 
 use super::SqliteStorage;
-use crate::{err::Result, timestamp::TimestampSecs, types::Usn};
+use crate::{config::ConfigEntry, err::Result, timestamp::TimestampSecs, types::Usn};
 use rusqlite::{params, NO_PARAMS};
-use serde::{de::DeserializeOwned, Serialize};
+use serde::de::DeserializeOwned;
 use serde_json::Value;
 use std::collections::HashMap;
 
 impl SqliteStorage {
-    pub(crate) fn set_config_value<T: Serialize>(
-        &self,
-        key: &str,
-        val: &T,
-        usn: Usn,
-        mtime: TimestampSecs,
-    ) -> Result<()> {
-        let json = serde_json::to_vec(val)?;
+    pub(crate) fn set_config_entry(&self, entry: &ConfigEntry) -> Result<()> {
         self.db
             .prepare_cached(include_str!("add.sql"))?
-            .execute(params![key, usn, mtime, &json])?;
+            .execute(params![&entry.key, entry.usn, entry.mtime, &entry.value])?;
         Ok(())
     }
 
@@ -41,6 +34,22 @@ impl SqliteStorage {
             .transpose()
     }
 
+    /// Return the raw bytes and other metadata, for undoing.
+    pub(crate) fn get_config_entry(&self, key: &str) -> Result<Option<Box<ConfigEntry>>> {
+        self.db
+            .prepare_cached(include_str!("get_entry.sql"))?
+            .query_and_then(&[key], |row| {
+                Ok(ConfigEntry::boxed(
+                    key,
+                    row.get(0)?,
+                    row.get(1)?,
+                    row.get(2)?,
+                ))
+            })?
+            .next()
+            .transpose()
+    }
+
     /// Prefix is expected to end with '_'.
     pub(crate) fn get_config_prefix(&self, prefix: &str) -> Result<Vec<(String, Vec<u8>)>> {
         let mut end = prefix.to_string();
@@ -70,7 +79,12 @@ impl SqliteStorage {
     ) -> Result<()> {
         self.db.execute("delete from config", NO_PARAMS)?;
         for (key, val) in conf.iter() {
-            self.set_config_value(key, val, usn, mtime)?;
+            self.set_config_entry(&ConfigEntry::boxed(
+                key,
+                serde_json::to_vec(&val)?,
+                usn,
+                mtime,
+            ))?;
         }
         Ok(())
     }
diff --git a/rslib/src/sync/mod.rs b/rslib/src/sync/mod.rs
index 7f43a9c8f..81115e923 100644
--- a/rslib/src/sync/mod.rs
+++ b/rslib/src/sync/mod.rs
@@ -328,8 +328,8 @@ where
             SyncActionRequired::NormalSyncRequired => {
                 self.col.discard_undo_and_study_queues();
                 self.col.storage.begin_trx()?;
-                self.col
-                    .unbury_if_day_rolled_over(self.col.timing_today()?)?;
+                let timing = self.col.timing_today()?;
+                self.col.unbury_if_day_rolled_over(timing)?;
                 match self.normal_sync_inner(state).await {
                     Ok(success) => {
                         self.col.storage.commit_trx()?;
diff --git a/rslib/src/undo/changes.rs b/rslib/src/undo/changes.rs
index bad7efe28..f50eba795 100644
--- a/rslib/src/undo/changes.rs
+++ b/rslib/src/undo/changes.rs
@@ -2,9 +2,10 @@
 // License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 
 use crate::{
-    card::undo::UndoableCardChange, decks::undo::UndoableDeckChange,
-    notes::undo::UndoableNoteChange, prelude::*, revlog::undo::UndoableRevlogChange,
-    scheduler::queue::undo::UndoableQueueChange, tags::undo::UndoableTagChange,
+    card::undo::UndoableCardChange, config::undo::UndoableConfigChange,
+    decks::undo::UndoableDeckChange, notes::undo::UndoableNoteChange, prelude::*,
+    revlog::undo::UndoableRevlogChange, scheduler::queue::undo::UndoableQueueChange,
+    tags::undo::UndoableTagChange,
 };
 
 #[derive(Debug)]
@@ -15,6 +16,7 @@ pub(crate) enum UndoableChange {
     Tag(UndoableTagChange),
     Revlog(UndoableRevlogChange),
     Queue(UndoableQueueChange),
+    Config(UndoableConfigChange),
 }
 
 impl UndoableChange {
@@ -26,6 +28,7 @@ impl UndoableChange {
             UndoableChange::Tag(c) => col.undo_tag_change(c),
             UndoableChange::Revlog(c) => col.undo_revlog_change(c),
             UndoableChange::Queue(c) => col.undo_queue_change(c),
+            UndoableChange::Config(c) => col.undo_config_change(c),
         }
     }
 }
@@ -65,3 +68,9 @@ impl From<UndoableQueueChange> for UndoableChange {
         UndoableChange::Queue(c)
     }
 }
+
+impl From<UndoableConfigChange> for UndoableChange {
+    fn from(c: UndoableConfigChange) -> Self {
+        UndoableChange::Config(c)
+    }
+}