added caching for span details api responses, also pre-calling of span details endpoint for each match after fetching IGC data

lib/pangea/choreographer/controllers/igc_controller.dart

@@ -19,14 +19,37 @@ import '../../repo/tokens_repo.dart';
 import '../../utils/error_handler.dart';
 import '../../utils/overlay.dart';
 
+class _SpanDetailsCacheItem {
+  SpanDetailsRepoReqAndRes data;
+
+  _SpanDetailsCacheItem({required this.data});
+}
+
 class IgcController {
   Choreographer choreographer;
   IGCTextData? igcTextData;
   Object? igcError;
 
   Completer<IGCTextData> igcCompleter = Completer();
+  final Map<int, _SpanDetailsCacheItem> _cache = {};
+  Timer? _cacheClearTimer;
 
-  IgcController(this.choreographer);
+  IgcController(this.choreographer) {
+    _initializeCacheClearing();
+  }
+
+  void _initializeCacheClearing() {
+    const duration = Duration(minutes: 2);
+    _cacheClearTimer = Timer.periodic(duration, (Timer t) => _clearCache());
+  }
+
+  void _clearCache() {
+    _cache.clear();
+  }
+
+  void dispose() {
+    _cacheClearTimer?.cancel();
+  }
 
   Future<void> getIGCTextData({required bool tokensOnly}) async {
     try {
@@ -80,6 +103,14 @@ class IgcController {
 
       igcTextData = igcTextDataResponse;
 
+      // After fetching igc data, pre-call span details for each match optimistically.
+      // This will make the loading of span details faster for the user
+      if (igcTextData?.matches.isNotEmpty ?? false) {
+        for (int i = 0; i < igcTextData!.matches.length; i++) {
+          getSpanDetails(i);
+        }
+      }
+
       debugPrint("igc text ${igcTextData.toString()}");
     } catch (err, stack) {
       debugger(when: kDebugMode);
@@ -99,18 +130,38 @@ class IgcController {
       debugger(when: kDebugMode);
       return;
     }
-    final SpanData span = igcTextData!.matches[matchIndex].match;
 
-    final SpanDetailsRepoReqAndRes response = await SpanDataRepo.getSpanDetails(
-      await choreographer.accessToken,
-      request: SpanDetailsRepoReqAndRes(
-        userL1: choreographer.l1LangCode!,
-        userL2: choreographer.l2LangCode!,
-        enableIGC: choreographer.igcEnabled,
-        enableIT: choreographer.itEnabled,
-        span: span,
-      ),
+    /// Retrieves the span data from the `igcTextData` matches at the specified `matchIndex`.
+    /// Creates a `SpanDetailsRepoReqAndRes` object with the retrieved span data and other parameters.
+    /// Generates a cache key based on the created `SpanDetailsRepoReqAndRes` object.
+    final SpanData span = igcTextData!.matches[matchIndex].match;
+    final req = SpanDetailsRepoReqAndRes(
+      userL1: choreographer.l1LangCode!,
+      userL2: choreographer.l2LangCode!,
+      enableIGC: choreographer.igcEnabled,
+      enableIT: choreographer.itEnabled,
+      span: span,
     );
+    final int cacheKey = req.hashCode;
+
+    /// Retrieves the [SpanDetailsRepoReqAndRes] response from the cache if it exists,
+    /// otherwise makes an API call to get the response and stores it in the cache.
+    SpanDetailsRepoReqAndRes response;
+    if (_cache.containsKey(cacheKey)) {
+      response = _cache[cacheKey]!.data;
+    } else {
+      response = await SpanDataRepo.getSpanDetails(
+        await choreographer.accessToken,
+        request: SpanDetailsRepoReqAndRes(
+          userL1: choreographer.l1LangCode!,
+          userL2: choreographer.l2LangCode!,
+          enableIGC: choreographer.igcEnabled,
+          enableIT: choreographer.itEnabled,
+          span: span,
+        ),
+      );
+      _cache[cacheKey] = _SpanDetailsCacheItem(data: response);
+    }
 
     try {
       igcTextData!.matches[matchIndex].match = response.span;

lib/pangea/repo/span_data_repo.dart

@@ -72,6 +72,24 @@ class SpanDetailsRepoReqAndRes {
         enableIGC: json['enable_igc'] as bool,
         span: SpanData.fromJson(json['span']),
       );
+
+  /// Overrides the equality operator to compare two [SpanDetailsRepoReqAndRes] objects.
+  /// Returns true if the objects are identical or have the same property
+  /// values (based on the results of the toJson function), false otherwise.
+  @override
+  bool operator ==(Object other) {
+    if (identical(this, other)) return true;
+    if (other is! SpanDetailsRepoReqAndRes) return false;
+
+    return toJson().toString() == other.toJson().toString();
+  }
+
+  /// Overrides the hashCode getter to generate a hash code for the [SpanDetailsRepoReqAndRes] object.
+  /// Used as keys in response cache in igc_controller.
+  @override
+  int get hashCode {
+    return toJson().toString().hashCode;
+  }
 }
 
 final spanDataRepomockSpan = SpanData(