fix: let a debounced settings write see changes made while it waits

DebouncedSaver keeps only the first callback of a burst, and
queueAsyncSave closed over the snapshot taken when it was called. So if
one player toggled a setting and a second toggled two seconds later, the
write that fired at five seconds persisted the first snapshot and dropped
the second player's change - it survived in memory until some later toggle
happened to trigger another write, and was lost on a crash.

Passing a supplier instead means the snapshot is taken when the write
runs, which is what "batched into a single save" was always meant to mean.
ConversionCache already had this shape by passing ::saveToDisk.

The staleness predates the refactor, but bc8010b claimed to have closed
this window; it only moved where the snapshot was built, not when.

Co-Authored-By: Claude <noreply@anthropic.com>

3 files changed, 29 insertions, 4 deletions

diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/settings/PlayerSettingsManager.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/settings/PlayerSettingsManager.kt
index de35c55..9ee8d5a 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/settings/PlayerSettingsManager.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/settings/PlayerSettingsManager.kt
@@ -61,7 +61,7 @@ class PlayerSettingsManager(
      */
     fun updateSettings(settings: PlayerChatSettings) {
         this.settings[settings.uuid] = settings
-        storage.queueAsyncSave(snapshot())
+        storage.queueAsyncSave(::snapshot)
         logger.fine("Updated settings for player ${settings.uuid}")
     }
 
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/settings/YamlPlayerSettingsStorage.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/settings/YamlPlayerSettingsStorage.kt
index 7a727b0..f4d8a6f 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/settings/YamlPlayerSettingsStorage.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/settings/YamlPlayerSettingsStorage.kt
@@ -66,9 +66,11 @@ class YamlPlayerSettingsStorage(
      * Queues an async save operation with 5-second debouncing.
      * Multiple save requests within 5 seconds are batched into a single save.
      *
-     * @param data The settings data to save
+     * @param data Supplies the settings to write. It is called when the write runs rather than
+     *   when it is queued, so the batched write persists every change made during the delay - not
+     *   just the one that started it.
      */
-    fun queueAsyncSave(data: PlayerSettingsData) {
-        saver.request { saveToDisk(data) }
+    fun queueAsyncSave(data: () -> PlayerSettingsData) {
+        saver.request { saveToDisk(data()) }
     }
 }
diff --git a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/settings/PlayerSettingsManagerTest.kt b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/settings/PlayerSettingsManagerTest.kt
index bc716c9..b7e1385 100644
--- a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/settings/PlayerSettingsManagerTest.kt
+++ b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/settings/PlayerSettingsManagerTest.kt
@@ -6,6 +6,7 @@ import dev.m1sk9.lunaticChat.paper.TestUtils
 import dev.m1sk9.lunaticChat.paper.TestUtils.createTestUUID
 import io.mockk.every
 import io.mockk.mockk
+import io.mockk.slot
 import io.mockk.verify
 import kotlin.test.Test
 import kotlin.test.assertEquals
@@ -82,6 +83,28 @@ class PlayerSettingsManagerTest {
     }
 
     @Test
+    fun `a queued save writes changes made after it was queued`() {
+        val (manager, storage, _) = createManager()
+        manager.initialize()
+
+        // Only the first request of a debounced burst survives; the write it schedules must still
+        // see every later change, or those changes exist only in memory until the next write.
+        val scheduled = slot<() -> PlayerSettingsData>()
+        every { storage.queueAsyncSave(capture(scheduled)) } returns Unit
+
+        val first = createTestUUID(1)
+        val second = createTestUUID(2)
+        manager.updateSettings(PlayerChatSettings(uuid = first, japaneseConversionEnabled = false))
+        val pendingWrite = scheduled.captured
+        manager.updateSettings(PlayerChatSettings(uuid = second, japaneseConversionEnabled = false))
+
+        val written = pendingWrite()
+
+        assertEquals(false, written.japaneseConversion[first])
+        assertEquals(false, written.japaneseConversion[second])
+    }
+
+    @Test
     fun `updateSettings should overwrite existing settings`() {
         val playerId = createTestUUID(1)
         val data =