feat(buddies): favorite a buddy from the Dive Partners list and detail page

lib/features/buddies/presentation/buddy_dive_share.dart

@@ -0,0 +1,121 @@
+import 'package:flutter/material.dart';
+
+import 'package:submersion/core/providers/provider.dart';
+import 'package:submersion/core/services/export/uddf/uddf_dives_extras.dart';
+import 'package:submersion/core/services/export/uddf/uddf_source_fetch.dart';
+import 'package:submersion/features/buddies/presentation/providers/buddy_providers.dart';
+import 'package:submersion/features/dive_log/domain/entities/dive.dart';
+import 'package:submersion/features/dive_log/presentation/providers/dive_providers.dart';
+import 'package:submersion/features/settings/presentation/providers/export_providers.dart';
+import 'package:submersion/l10n/l10n_extension.dart';
+import 'package:submersion/shared/widgets/export_destination_sheet.dart';
+
+/// Exports every dive shared with [buddyId] as UDDF, via the share sheet or
+/// a save panel depending on the user's choice.
+///
+/// Split out of [BuddyDetailPage] (pure export logic, no UI beyond the
+/// destination sheet and a couple of snackbars) to keep that file under the
+/// project's 800-line guideline.
+Future<void> shareDivesWithBuddy(
+  BuildContext context,
+  WidgetRef ref,
+  String buddyId,
+) async {
+  // Capture the scaffold messenger and l10n before any async gaps
+  final scaffoldMessenger = ScaffoldMessenger.of(context);
+  final l10n = context.l10n;
+
+  final choice = await showExportDestinationSheetWithOptions(
+    context,
+    title: l10n.buddies_action_shareDives,
+    showRawDataToggle: true,
+    showDiveContentToggles: true,
+  );
+  if (choice == null) return;
+  final destination = choice.destination;
+  final options = choice.options;
+
+  // Show preparing message
+  scaffoldMessenger.showSnackBar(
+    SnackBar(
+      content: Text(l10n.buddies_message_preparingExport),
+      duration: const Duration(seconds: 1),
+    ),
+  );
+
+  // Get all dive IDs for this buddy
+  final diveIds = await ref.read(diveIdsForBuddyProvider(buddyId).future);
+
+  if (diveIds.isEmpty) {
+    scaffoldMessenger.hideCurrentSnackBar();
+    scaffoldMessenger.showSnackBar(
+      SnackBar(content: Text(l10n.buddies_message_noDivesToShare)),
+    );
+    return;
+  }
+
+  try {
+    // Fetch all dives
+    final diveRepository = ref.read(diveRepositoryProvider);
+    final dives = <Dive>[];
+    for (final diveId in diveIds) {
+      final dive = await diveRepository.getDiveById(diveId);
+      if (dive != null) {
+        dives.add(dive);
+      }
+    }
+
+    if (dives.isEmpty) {
+      scaffoldMessenger.hideCurrentSnackBar();
+      scaffoldMessenger.showSnackBar(
+        SnackBar(content: Text(l10n.buddies_message_noDivesFound)),
+      );
+      return;
+    }
+
+    // Get unique sites from dives
+    final sites = dives
+        .where((d) => d.site != null)
+        .map((d) => d.site!)
+        .toSet()
+        .toList();
+
+    scaffoldMessenger.hideCurrentSnackBar();
+
+    // Hand the UDDF to the share sheet, or to a save panel on the user's
+    // request. Either way no success snackbar follows: the share sheet and
+    // the save panel each provide their own feedback.
+    final exportService = ref.read(exportServiceProvider);
+    final dataSources = await ref.read(uddfSourceFetchProvider)(
+      dives.map((d) => d.id).toList(growable: false),
+      options,
+    );
+    final extras = await ref.read(uddfDivesExtrasFetchProvider)(
+      dives.map((d) => d.id).toList(growable: false),
+      options,
+    );
+    switch (destination) {
+      case ExportDestination.share:
+        await exportService.exportDivesToUddf(
+          dives,
+          sites: sites,
+          dataSources: dataSources,
+          extras: extras,
+          options: options,
+        );
+      case ExportDestination.saveToFile:
+        await exportService.saveDivesToUddfFile(
+          dives,
+          sites: sites,
+          dataSources: dataSources,
+          extras: extras,
+          options: options,
+        );
+    }
+  } catch (e) {
+    scaffoldMessenger.hideCurrentSnackBar();
+    scaffoldMessenger.showSnackBar(
+      SnackBar(content: Text(l10n.buddies_message_exportFailed(e.toString()))),
+    );
+  }
+}