Persist quick send history safely

android/app/src/main/kotlin/com/wirelesstextsyncer/wireless_text_syncer_android/QuickSendActivity.kt

@@ -21,6 +21,7 @@ import android.widget.ImageView
 import android.widget.LinearLayout
 import android.widget.Switch
 import android.widget.TextView
+import org.json.JSONArray
 
 class QuickSendActivity : Activity() {
     private lateinit var input: EditText
@@ -459,6 +460,7 @@ class QuickSendActivity : Activity() {
         }
 
         if (ConnectionService.sendText(text) && (!appendEnter || ConnectionService.sendEnter())) {
+            saveHistory(text)
             sendButton.background = roundedDrawable(Color.rgb(22, 163, 74), dp(26).toFloat())
             sendIcon.setImageResource(R.drawable.ic_check_24)
             sendIcon.setColorFilter(Color.WHITE, PorterDuff.Mode.SRC_IN)
@@ -472,6 +474,45 @@ class QuickSendActivity : Activity() {
         }
     }
 
+    private fun saveHistory(text: String) {
+        if (text.trim().isEmpty()) {
+            return
+        }
+
+        val prefs = getSharedPreferences(PREFS, Context.MODE_PRIVATE)
+        val currentHistory = readHistory()
+        val nextHistory = linkedSetOf(text)
+        currentHistory
+            .filter { it != text }
+            .take(MAX_HISTORY_ITEMS - 1)
+            .forEach { nextHistory.add(it) }
+
+        prefs.edit()
+            .putString(KEY_HISTORY, JSON_LIST_PREFIX + JSONArray(nextHistory.toList()).toString())
+            .apply()
+    }
+
+    private fun readHistory(): List<String> {
+        val rawValue = getSharedPreferences(PREFS, Context.MODE_PRIVATE).all[KEY_HISTORY]
+        return when (rawValue) {
+            is String -> decodeHistoryString(rawValue)
+            is Set<*> -> rawValue.filterIsInstance<String>()
+            else -> emptyList()
+        }
+    }
+
+    private fun decodeHistoryString(value: String): List<String> {
+        if (!value.startsWith(JSON_LIST_PREFIX)) {
+            return emptyList()
+        }
+
+        return runCatching {
+            val array = JSONArray(value.substring(JSON_LIST_PREFIX.length))
+            List(array.length()) { index -> array.optString(index) }
+                .filter { it.isNotEmpty() }
+        }.getOrDefault(emptyList())
+    }
+
     private fun toggleAppendEnter() {
         setAppendEnter(!appendEnter)
     }
@@ -529,5 +570,8 @@ class QuickSendActivity : Activity() {
     companion object {
         private const val PREFS = "FlutterSharedPreferences"
         private const val KEY_APPEND_ENTER = "flutter.append_enter"
+        private const val KEY_HISTORY = "flutter.send_history"
+        private const val JSON_LIST_PREFIX = "VGhpcyBpcyB0aGUgcHJlZml4IGZvciBhIGxpc3Qu!"
+        private const val MAX_HISTORY_ITEMS = 10
     }
 }

lib/main.dart

@@ -221,7 +221,7 @@ class _InputSyncPageState extends State<InputSyncPage>
   @override
   void didChangeAppLifecycleState(AppLifecycleState state) {
     if (state == AppLifecycleState.resumed) {
-      unawaited(_syncAppendEnterFromPrefs());
+      unawaited(_syncSharedPrefsFromDisk());
     }
   }
 
@@ -239,7 +239,7 @@ class _InputSyncPageState extends State<InputSyncPage>
           prefs.getString(_portKey) ?? nativeState.port.toString();
       clearAfterSend = prefs.getBool(_clearAfterSendKey) ?? false;
       appendEnter = prefs.getBool(_appendEnterKey) ?? false;
-      sendHistory = prefs.getStringList(_historyKey) ?? [];
+      sendHistory = _readHistory(prefs);
       connection = nativeState;
       headerExpanded = !nativeState.connected;
     });
@@ -459,17 +459,44 @@ class _InputSyncPageState extends State<InputSyncPage>
     });
   }
 
-  Future<void> _syncAppendEnterFromPrefs() async {
+  Future<void> _syncSharedPrefsFromDisk() async {
     final prefs = await SharedPreferences.getInstance();
     await prefs.reload();
     final nextAppendEnter = prefs.getBool(_appendEnterKey) ?? false;
-    if (!mounted || nextAppendEnter == appendEnter) {
+    final nextHistory = _readHistory(prefs);
+    if (!mounted) {
       return;
     }
 
-    setState(() {
+    if (nextAppendEnter != appendEnter ||
-      appendEnter = nextAppendEnter;
+        !_stringListsEqual(nextHistory, sendHistory)) {
-    });
+      setState(() {
+        appendEnter = nextAppendEnter;
+        sendHistory = nextHistory;
+      });
+    }
+  }
+
+  bool _stringListsEqual(List<String> left, List<String> right) {
+    if (left.length != right.length) {
+      return false;
+    }
+
+    for (var index = 0; index < left.length; index += 1) {
+      if (left[index] != right[index]) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  List<String> _readHistory(SharedPreferences prefs) {
+    try {
+      return prefs.getStringList(_historyKey) ?? [];
+    } catch (_) {
+      return [];
+    }
   }
 
   void _restoreHistory(String text) {