TF-3697 Open specific thread detail email

lib/features/thread_detail/presentation/utils/thread_detail_presentation_utils.dart

@@ -2,7 +2,6 @@ import 'dart:math';
 
 import 'package:flutter/material.dart';
 import 'package:jmap_dart_client/jmap/mail/email/email.dart';
-import 'package:model/email/presentation_email.dart';
 
 class ThreadDetailPresentationUtils {
   const ThreadDetailPresentationUtils._();
@@ -11,29 +10,48 @@ class ThreadDetailPresentationUtils {
   static const _defaultLoadSize = 20;
 
   @visibleForTesting
-  static get initialLoadSize => _initialLoadSize;
-  @visibleForTesting
-  static get defaultLoadSize => _defaultLoadSize;
+  static int get defaultLoadSize => _defaultLoadSize;
 
-  static List<EmailId> getEmailIdsToLoad(
-    Map<EmailId, PresentationEmail?> emailIdsPresentation,
-  ) {
-    final validEmailIdsToLoad = emailIdsPresentation.entries
-      .where((entry) => entry.value == null)
-      .map((entry) => entry.key)
-      .toList();
+  static List<EmailId> getFirstLoadEmailIds(
+    List<EmailId> emailIds, {
+    EmailId? selectedEmailId,
+  }) {
+    // Default first, second and last email
+    if (emailIds.length <= 3) return emailIds;
 
-    if (validEmailIdsToLoad.length == emailIdsPresentation.length) {
-      // No email loaded yet
-      return validEmailIdsToLoad.sublist(
-        0,
-        min(validEmailIdsToLoad.length, _initialLoadSize),
-      );
+    if (selectedEmailId == null ||
+        !emailIds.contains(selectedEmailId) ||
+        selectedEmailId == emailIds.first ||
+        selectedEmailId == emailIds.last ||
+        selectedEmailId == emailIds.elementAt(1)) {
+
+      return [
+        ...emailIds.sublist(
+          0,
+          min(emailIds.length, _initialLoadSize),
+        ),
+        emailIds.last,
+      ];
     }
 
-    return validEmailIdsToLoad.sublist(
-      validEmailIdsToLoad.length - min(validEmailIdsToLoad.length, _defaultLoadSize),
-      validEmailIdsToLoad.length,
+    return [
+      emailIds.first,
+      selectedEmailId,
+      emailIds.last,
+    ];
+  }
+
+  static getLoadMoreEmailIds(
+    List<EmailId> emailIds, {
+    bool loadEmailsAfterSelectedEmail = false,
+  }) {
+    if (loadEmailsAfterSelectedEmail) {
+      return emailIds.sublist(0, min(emailIds.length, _defaultLoadSize));
+    }
+
+    return emailIds.sublist(
+      emailIds.length - min(_defaultLoadSize, emailIds.length),
+      emailIds.length,
     );
   }
 }