Improve image cache. Close #326

lib/foundation/cache_manager.dart

@@ -21,7 +21,7 @@ class CacheManager {
 
   int _limitSize = 2 * 1024 * 1024 * 1024;
 
-  CacheManager._create(){
+  CacheManager._create() {
     Directory(cachePath).createSync(recursive: true);
     _db = sqlite3.open('${App.dataPath}/cache.db');
     _db.execute('''
@@ -33,100 +33,102 @@ class CacheManager {
         type TEXT
       )
     ''');
-    compute((path) => Directory(path).size, cachePath)
-        .then((value) => _currentSize = value);
+    compute((path) => Directory(path).size, cachePath).then((value) {
+      _currentSize = value;
+      checkCache();
+    });
   }
 
+  /// Get the singleton instance of CacheManager.
   factory CacheManager() => instance ??= CacheManager._create();
 
   /// set cache size limit in MB
-  void setLimitSize(int size){
+  void setLimitSize(int size) {
     _limitSize = size * 1024 * 1024;
   }
 
-  void setType(String key, String? type){
-    _db.execute('''
-      UPDATE cache
-      SET type = ?
-      WHERE key = ?
-    ''', [type, key]);
-  }
-
-  String? getType(String key){
-    var res = _db.select('''
-      SELECT type FROM cache
-      WHERE key = ?
-    ''', [key]);
-    if(res.isEmpty){
-      return null;
-    }
-    return res.first[0];
-  }
-
-  Future<void> writeCache(String key, List<int> data, [int duration = 7 * 24 * 60 * 60 * 1000]) async{
+  /// Write cache to disk.
+  Future<void> writeCache(String key, List<int> data,
+      [int duration = 7 * 24 * 60 * 60 * 1000]) async {
     this.dir++;
     this.dir %= 100;
     var dir = this.dir;
-    var name = md5.convert(Uint8List.fromList(key.codeUnits)).toString();
+    var name = md5.convert(key.codeUnits).toString();
     var file = File('$cachePath/$dir/$name');
-    while(await file.exists()){
-      name = md5.convert(Uint8List.fromList(name.codeUnits)).toString();
-      file = File('$cachePath/$dir/$name');
-    }
     await file.create(recursive: true);
     await file.writeAsBytes(data);
     var expires = DateTime.now().millisecondsSinceEpoch + duration;
     _db.execute('''
       INSERT OR REPLACE INTO cache (key, dir, name, expires) VALUES (?, ?, ?, ?)
     ''', [key, dir.toString(), name, expires]);
-    if(_currentSize != null) {
+    if (_currentSize != null) {
       _currentSize = _currentSize! + data.length;
     }
     checkCacheIfRequired();
   }
 
-  Future<CachingFile> openWrite(String key) async{
-    this.dir++;
-    this.dir %= 100;
-    var dir = this.dir;
-    var name = md5.convert(Uint8List.fromList(key.codeUnits)).toString();
-    var file = File('$cachePath/$dir/$name');
-    while(await file.exists()){
-      name = md5.convert(Uint8List.fromList(name.codeUnits)).toString();
-      file = File('$cachePath/$dir/$name');
-    }
-    await file.create(recursive: true);
-    return CachingFile._(key, dir.toString(), name, file);
-  }
-
-  Future<File?> findCache(String key) async{
+  /// Find cache by key.
+  /// If cache is expired, it will be deleted and return null.
+  /// If cache is not found, it will return null.
+  /// If cache is found, it will return the file, and update the expires time.
+  Future<File?> findCache(String key) async {
     var res = _db.select('''
       SELECT * FROM cache
       WHERE key = ?
     ''', [key]);
-    if(res.isEmpty){
+    if (res.isEmpty) {
       return null;
     }
     var row = res.first;
     var dir = row[1] as String;
     var name = row[2] as String;
+    var expires = row[3] as int;
     var file = File('$cachePath/$dir/$name');
-    if(await file.exists()){
+    var now = DateTime.now().millisecondsSinceEpoch;
+    if (expires < now) {
+      // expired
+      _db.execute('''
+        DELETE FROM cache
+        WHERE key = ?
+      ''', [key]);
+      if (await file.exists()) {
+        await file.delete();
+      }
+      return null;
+    }
+    if (await file.exists()) {
+      // update time
+      var expires = now + 7 * 24 * 60 * 60 * 1000;
+      _db.execute('''
+        UPDATE cache
+        SET expires = ?
+        WHERE key = ?
+      ''', [expires, key]);
       return file;
+    } else {
+      _db.execute('''
+        DELETE FROM cache
+        WHERE key = ?
+      ''', [key]);
     }
     return null;
   }
 
   bool _isChecking = false;
 
+  /// Check cache size and delete expired cache.
+  /// Only check cache if current size is greater than limit size.
   void checkCacheIfRequired() {
-    if(_currentSize != null && _currentSize! > _limitSize){
+    if (_currentSize != null && _currentSize! > _limitSize) {
       checkCache();
     }
   }
 
-  Future<void> checkCache() async{
-    if(_isChecking){
+  /// Check cache size and delete expired cache.
+  /// If current size is greater than limit size,
+  /// delete cache until current size is less than limit size.
+  Future<void> checkCache() async {
+    if (_isChecking) {
       return;
     }
     _isChecking = true;
@@ -134,11 +136,13 @@ class CacheManager {
       SELECT * FROM cache
       WHERE expires < ?
     ''', [DateTime.now().millisecondsSinceEpoch]);
-    for(var row in res){
+    for (var row in res) {
       var dir = row[1] as String;
       var name = row[2] as String;
       var file = File('$cachePath/$dir/$name');
-      if(await file.exists()){
+      if (await file.exists()) {
+        var size = await file.length();
+        _currentSize = _currentSize! - size;
         await file.delete();
       }
     }
@@ -147,26 +151,18 @@ class CacheManager {
       WHERE expires < ?
     ''', [DateTime.now().millisecondsSinceEpoch]);
 
-    int count = 0;
-    var res2 = _db.select('''
-      SELECT COUNT(*) FROM cache
-    ''');
-    if(res2.isNotEmpty){
-      count = res2.first[0] as int;
-    }
-
-    while((_currentSize != null && _currentSize! > _limitSize) ||  count > 2000){
+    while (_currentSize != null && _currentSize! > _limitSize) {
       var res = _db.select('''
         SELECT * FROM cache
         ORDER BY expires ASC
         limit 10
       ''');
-      for(var row in res){
+      for (var row in res) {
         var key = row[0] as String;
         var dir = row[1] as String;
         var name = row[2] as String;
         var file = File('$cachePath/$dir/$name');
-        if(await file.exists()){
+        if (await file.exists()) {
           var size = await file.length();
           await file.delete();
           _db.execute('''
@@ -174,7 +170,7 @@ class CacheManager {
             WHERE key = ?
           ''', [key]);
           _currentSize = _currentSize! - size;
-          if(_currentSize! <= _limitSize){
+          if (_currentSize! <= _limitSize) {
             break;
           }
         } else {
@@ -183,18 +179,18 @@ class CacheManager {
             WHERE key = ?
           ''', [key]);
         }
-        count--;
       }
     }
     _isChecking = false;
   }
 
-  Future<void> delete(String key) async{
+  /// Delete cache by key.
+  Future<void> delete(String key) async {
     var res = _db.select('''
       SELECT * FROM cache
       WHERE key = ?
     ''', [key]);
-    if(res.isEmpty){
+    if (res.isEmpty) {
       return;
     }
     var row = res.first;
@@ -202,7 +198,7 @@ class CacheManager {
     var name = row[2] as String;
     var file = File('$cachePath/$dir/$name');
     var fileSize = 0;
-    if(await file.exists()){
+    if (await file.exists()) {
       fileSize = await file.length();
       await file.delete();
     }
@@ -210,11 +206,12 @@ class CacheManager {
       DELETE FROM cache
       WHERE key = ?
     ''', [key]);
-    if(_currentSize != null) {
+    if (_currentSize != null) {
       _currentSize = _currentSize! - fileSize;
     }
   }
 
+  /// Delete all cache.
   Future<void> clear() async {
     await Directory(cachePath).delete(recursive: true);
     Directory(cachePath).createSync(recursive: true);
@@ -223,75 +220,4 @@ class CacheManager {
     ''');
     _currentSize = 0;
   }
-
-  Future<void> deleteKeyword(String keyword) async{
-    var res = _db.select('''
-      SELECT * FROM cache
-      WHERE key LIKE ?
-    ''', ['%$keyword%']);
-    for(var row in res){
-      var key = row[0] as String;
-      var dir = row[1] as String;
-      var name = row[2] as String;
-      var file = File('$cachePath/$dir/$name');
-      var fileSize = 0;
-      if(await file.exists()){
-        fileSize = await file.length();
-        try {
-          await file.delete();
-        }
-        finally {}
-      }
-      _db.execute('''
-        DELETE FROM cache
-        WHERE key = ?
-      ''', [key]);
-      if(_currentSize != null) {
-        _currentSize = _currentSize! - fileSize;
-      }
-    }
-  }
 }
-
-class CachingFile{
-  CachingFile._(this.key, this.dir, this.name, this.file);
-
-  final String key;
-
-  final String dir;
-
-  final String name;
-
-  final File file;
-
-  final List<int> _buffer = [];
-
-  Future<void> writeBytes(List<int> data) async{
-    _buffer.addAll(data);
-    if(_buffer.length > 1024 * 1024){
-      await file.writeAsBytes(_buffer, mode: FileMode.append);
-      _buffer.clear();
-    }
-  }
-
-  Future<void> close() async{
-    if(_buffer.isNotEmpty){
-      await file.writeAsBytes(_buffer, mode: FileMode.append);
-    }
-    CacheManager()._db.execute('''
-      INSERT OR REPLACE INTO cache (key, dir, name, expires) VALUES (?, ?, ?, ?)
-    ''', [key, dir, name, DateTime.now().millisecondsSinceEpoch + 7 * 24 * 60 * 60 * 1000]);
-    CacheManager().checkCacheIfRequired();
-  }
-
-  Future<void> cancel() async{
-    await file.deleteIgnoreError();
-  }
-
-  void reset() {
-    _buffer.clear();
-    if(file.existsSync()) {
-      file.deleteSync();
-    }
-  }
-}