refacto BlogPost

src/PostIt/PostIt.Android/Services/ContactService.Mobile.cs

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+#if ANDROID || IOS
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Maui.ApplicationModel.Communication;
+using Microsoft.Maui.ApplicationModel;
+using Microsoft.Maui.Devices;
+using PostIt.Services;
+using System.Linq;
+
+namespace PostIt.Android.Services;
+
+/// <summary>
+/// Mobile implementation backed by MAUI Essentials
+/// <c>Contacts.Default</c>.
+///
+/// <para>Compiled only for ANDROID and IOS. On desktop targets,
+/// see <c>ContactService.Desktop.cs</c> (the stub that wins at
+/// compile time).</para>
+///
+/// <para>Note: at runtime, this class throws
+/// <c>NotImplementedInReferenceAssemblyException</c> unless
+/// the host application project also references the
+/// platform-specific Microsoft.Maui.Essentials implementation
+/// (typically <c>PostIt.Android</c>). On iOS the same is
+/// required via <c>PostIt.iOS</c>. On desktop the stub is used
+/// and this file is excluded.</para>
+/// </summary>
+public sealed class ContactService : IContactService
+{
+    public async Task<IReadOnlyList<ContactDto>> GetDeviceContactsAsync(CancellationToken ct = default)
+    {
+        if (DeviceInfo.Current.Platform == DevicePlatform.Unknown)
+            return Array.Empty<ContactDto>();
+
+        try
+        {
+            var status = await Permissions.RequestAsync<Permissions.ContactsRead>();
+            if (status != PermissionStatus.Granted)
+                return Array.Empty<ContactDto>();
+
+            var contacts = await Contacts.Default.GetAllAsync();
+            if (contacts is null) return Array.Empty<ContactDto>();
+
+            // Carry the per-contact email list as-is. A real
+            // device contact can carry several addresses (home /
+            // work / other); the UI use case ("invite / add to a
+            // circle") can then decide which address to use, or
+            // let the user pick. The platform-neutral ContactDto
+            // shape is intentionally richer than the Yavsc
+            // directory's single-Email shape — the two flows
+            // answer different questions.
+            var result = new List<ContactDto>(contacts.Count());
+            foreach (var c in contacts)
+            {
+                var emails = ExtractEmails(c.Emails);
+                result.Add(new ContactDto(
+                    c.Id,
+                    c.DisplayName ?? string.Empty,
+                    emails));
+            }
+            return result;
+        }
+        catch (Exception ex)
+        {
+            System.Diagnostics.Debug.WriteLine($"ContactService: {ex.Message}");
+            return Array.Empty<ContactDto>();
+        }
+    }
+
+    private static IReadOnlyList<string> ExtractEmails(IEnumerable<ContactEmail>? emails)
+    {
+        if (emails is null) return Array.Empty<string>();
+        var list = new List<string>();
+        foreach (var e in emails)
+        {
+            if (!string.IsNullOrEmpty(e.EmailAddress))
+                list.Add(e.EmailAddress);
+        }
+        return list;
+    }
+}
+#endif