feat: pull to refresh m3u playlists

for main playlists page and m3u playlist subpage
ref #125

lib/base/pull_to_refresh.dart

@@ -0,0 +1,94 @@
+import 'package:flutter/material.dart';
+import 'package:get/get.dart';
+
+import 'package:namida/core/icon_fonts/broken_icons.dart';
+
+mixin PullToRefreshMixin<T extends StatefulWidget> on State<T> implements TickerProvider {
+  final turnsTween = Tween<double>(begin: 0.0, end: 1.0);
+  late final animation = AnimationController(vsync: this, duration: Duration.zero);
+  AnimationController get animation2;
+
+  final _minTrigger = 20;
+
+  num get pullNormalizer => 20;
+
+  bool onScrollNotification(ScrollMetricsNotification notification) {
+    final pixels = notification.metrics.pixels;
+    if (pixels < -_minTrigger) {
+      animation.animateTo(((pixels + _minTrigger).abs() / pullNormalizer).clamp(0, 1));
+    } else if (animation.value > 0) {
+      animation.animateTo(0);
+    }
+    return true;
+  }
+
+  double _distanceDragged = 0;
+  bool onVerticalDragUpdate(double dy) {
+    _distanceDragged -= dy;
+    if (_distanceDragged < -_minTrigger) {
+      animation.animateTo(((_distanceDragged + _minTrigger).abs() / pullNormalizer).clamp(0, 1));
+    } else if (animation.value > 0) {
+      animation.animateTo(0);
+    }
+    return true;
+  }
+
+  void onVerticalDragFinish() {
+    animation.animateTo(0, duration: const Duration(milliseconds: 100));
+    _distanceDragged = 0;
+  }
+
+  Future<void> showRefreshingAnimation(Future<void> Function() whileExecuting) async {
+    animation2.repeat();
+    await whileExecuting();
+    await animation2.fling();
+    animation2.stop();
+  }
+
+  Widget get pullToRefreshWidget {
+    return Positioned(
+      left: 0,
+      right: 0,
+      child: AnimatedBuilder(
+        animation: animation,
+        child: CircleAvatar(
+          radius: 24.0,
+          backgroundColor: context.theme.colorScheme.secondaryContainer,
+          child: const Icon(Broken.refresh_2),
+        ),
+        builder: (context, circleAvatar) {
+          final p = animation.value;
+          if (!animation2.isAnimating && p == 0) return const SizedBox();
+          const multiplier = 4.5;
+          const minus = multiplier / 3;
+          return Padding(
+            padding: EdgeInsets.only(top: 12.0 + p * 128.0),
+            child: Transform.rotate(
+              angle: (p * multiplier) - minus,
+              child: AnimatedBuilder(
+                animation: animation2,
+                child: circleAvatar,
+                builder: (context, circleAvatar) {
+                  return Opacity(
+                    opacity: animation2.status == AnimationStatus.forward ? 1.0 : p,
+                    child: RotationTransition(
+                      key: const Key('rotatie'),
+                      turns: turnsTween.animate(animation2),
+                      child: circleAvatar,
+                    ),
+                  );
+                },
+              ),
+            ),
+          );
+        },
+      ),
+    );
+  }
+
+  @override
+  void dispose() {
+    animation.dispose();
+    super.dispose();
+  }
+}

lib/controller/playlist_controller.dart

@@ -249,7 +249,7 @@ class PlaylistController extends PlaylistManager<TrackWithDate> {
     // -- similar name exists, so m3u overrides it
     // -- this can produce in an outdated playlist version in cache
     // -- which will be seen if the m3u file got deleted/renamed
-    await _prepareM3UPlaylists();
+    await prepareM3UPlaylists();
   }
 
   Future<List<Track>> readM3UFiles(Set<String> filesPaths) async {
@@ -270,19 +270,23 @@ class PlaylistController extends PlaylistManager<TrackWithDate> {
     return listy;
   }
 
-  Future<void> _prepareM3UPlaylists() async {
+  Future<void> prepareM3UPlaylists({Set<String> forPaths = const {}}) async {
     final allAvailableDirectories = await Indexer.inst.getAvailableDirectories(strictNoMedia: false);
 
-    final parameters = {
-      'allAvailableDirectories': allAvailableDirectories,
-      'directoriesToExclude': <String>[],
-      'extensions': kM3UPlaylistsExtensions,
-      'respectNoMedia': false,
-    };
-
-    final mapResult = await getFilesTypeIsolate.thready(parameters);
+    late final Set<String> allPaths;
+    if (forPaths.isNotEmpty) {
+      allPaths = forPaths;
+    } else {
+      final parameters = {
+        'allAvailableDirectories': allAvailableDirectories,
+        'directoriesToExclude': <String>[],
+        'extensions': kM3UPlaylistsExtensions,
+        'respectNoMedia': false,
+      };
+      final mapResult = await getFilesTypeIsolate.thready(parameters);
+      allPaths = mapResult['allPaths'] as Set<String>;
+    }
 
-    final allPaths = mapResult['allPaths'] as Set<String>;
     final resBoth = await _parseM3UPlaylistFiles.thready({
       'paths': allPaths,
       'libraryTracks': allTracksInLibrary,