feat: implement tags tab, board search execution and markdown export wiring

YKanBan.Tests/TestUtilities/ScriptedDialogService.cs

@@ -0,0 +1,50 @@
+using YKanBan.ViewModels.Dialogs;
+
+namespace YKanBan.Tests.TestUtilities;
+
+/// <summary>
+/// Records every dialog shown and lets a test script answer it. The result
+/// is whatever the dialog closed with; a dialog the script leaves open
+/// counts as dismissed. The save-file dialog answers with
+/// <see cref="SaveFilePath"/>.
+/// </summary>
+internal sealed class ScriptedDialogService : IDialogService
+{
+    public List<DialogViewModelBase> Shown { get; } = [];
+
+    public Func<DialogViewModelBase, Task> Script { get; set; } = _ => Task.CompletedTask;
+
+    public string? SaveFilePath { get; set; }
+
+    public List<string> SuggestedFileNames { get; } = [];
+
+    public async Task<bool> ShowAsync(DialogViewModelBase dialog)
+    {
+        Shown.Add(dialog);
+        bool? result = null;
+        dialog.CloseRequested += (_, closed) => result ??= closed;
+        await Script(dialog);
+        return result ?? false;
+    }
+
+    public Task<string?> PickSaveFilePathAsync(string suggestedFileName)
+    {
+        SuggestedFileNames.Add(suggestedFileName);
+        return Task.FromResult(SaveFilePath);
+    }
+
+    /// <summary>Answers every confirmation dialog with the given choice.</summary>
+    public static Func<DialogViewModelBase, Task> AnswerConfirmations(bool confirm) => dialog =>
+    {
+        if (dialog is ConfirmDialogViewModel confirmation)
+        {
+            if (confirm)
+            {
+                confirmation.ConfirmCommand.Execute(null);
+                return Task.CompletedTask;
+            }
+            return confirmation.CancelCommand.ExecuteAsync(null);
+        }
+        return Task.CompletedTask;
+    };
+}

YKanBan.Tests/ViewModels/BoardViewModelTests.cs

@@ -16,42 +16,6 @@ namespace YKanBan.Tests.ViewModels;
 [TestClass]
 public class BoardViewModelTests
 {
-    /// <summary>
-    /// Records every dialog shown and lets a test script answer it. The result
-    /// is whatever the dialog closed with; a dialog the script leaves open
-    /// counts as dismissed.
-    /// </summary>
-    private sealed class ScriptedDialogService : IDialogService
-    {
-        public List<DialogViewModelBase> Shown { get; } = [];
-
-        public Func<DialogViewModelBase, Task> Script { get; set; } = _ => Task.CompletedTask;
-
-        public async Task<bool> ShowAsync(DialogViewModelBase dialog)
-        {
-            Shown.Add(dialog);
-            bool? result = null;
-            dialog.CloseRequested += (_, closed) => result ??= closed;
-            await Script(dialog);
-            return result ?? false;
-        }
-    }
-
-    /// <summary>Answers every confirmation dialog with the given choice.</summary>
-    private static Func<DialogViewModelBase, Task> AnswerConfirmations(bool confirm) => dialog =>
-    {
-        if (dialog is ConfirmDialogViewModel confirmation)
-        {
-            if (confirm)
-            {
-                confirmation.ConfirmCommand.Execute(null);
-                return Task.CompletedTask;
-            }
-            return confirmation.CancelCommand.ExecuteAsync(null);
-        }
-        return Task.CompletedTask;
-    };
-
     private sealed class Fixture : IDisposable
     {
         public TempDirectory Directory { get; } = new();
@@ -144,7 +108,7 @@ public class BoardViewModelTests
         fixture.Repository.AddCard(column.Id, "", "", []);
         fixture.Repository.AddCard(column.Id, "", "", []);
         BoardViewModel board = fixture.CreateBoard();
-        fixture.Dialogs.Script = AnswerConfirmations(false);
+        fixture.Dialogs.Script = ScriptedDialogService.AnswerConfirmations(false);
 
         await board.Columns[0].DeleteCommand.ExecuteAsync(null);
 
@@ -174,7 +138,7 @@ public class BoardViewModelTests
         ColumnModel column = fixture.Repository.AddColumn("A", "");
         fixture.Repository.AddCard(column.Id, "gone", "", []);
         BoardViewModel board = fixture.CreateBoard();
-        fixture.Dialogs.Script = AnswerConfirmations(true);
+        fixture.Dialogs.Script = ScriptedDialogService.AnswerConfirmations(true);
 
         await board.Columns[0].Cards[0].DeleteCommand.ExecuteAsync(null);
 
@@ -271,11 +235,11 @@ public class BoardViewModelTests
         editor.CloseRequested += (_, result) => closedWith = result;
         editor.Content = "draft";
 
-        fixture.Dialogs.Script = AnswerConfirmations(false);
+        fixture.Dialogs.Script = ScriptedDialogService.AnswerConfirmations(false);
         await editor.RequestCancelAsync();
         Assert.IsNull(closedWith, "Declining the discard keeps the editor open.");
 
-        fixture.Dialogs.Script = AnswerConfirmations(true);
+        fixture.Dialogs.Script = ScriptedDialogService.AnswerConfirmations(true);
         await editor.RequestCancelAsync();
         Assert.IsFalse(closedWith);
         Assert.AreEqual(0, fixture.Repository.GetCards().Count);

YKanBan.Tests/ViewModels/TagsAndSearchViewModelTests.cs

@@ -0,0 +1,400 @@
+using YKanBan.Models;
+using YKanBan.Storage.AppData;
+using YKanBan.Storage.Workspace;
+using YKanBan.Tests.TestUtilities;
+using YKanBan.ViewModels;
+using YKanBan.ViewModels.Board;
+using YKanBan.ViewModels.Dialogs;
+using YKanBan.ViewModels.Tags;
+
+namespace YKanBan.Tests.ViewModels;
+
+/// <summary>
+/// View-model tests of the search bar, the tags tab, the cross-tab refresh and
+/// the export wiring, against a real temporary workspace with a scripted
+/// dialog service.
+/// </summary>
+[TestClass]
+public class TagsAndSearchViewModelTests
+{
+    private sealed class Fixture : IDisposable
+    {
+        public TempDirectory Directory { get; } = new();
+
+        public WorkspaceSession Session { get; }
+
+        public WorkspaceRepository Repository => Session.Repository;
+
+        public AppConfig Config { get; } = new();
+
+        public ScriptedDialogService Dialogs { get; } = new();
+
+        public Fixture()
+        {
+            WorkspaceInitializer.Initialize(Directory.FullPath);
+            Session = WorkspaceSession.Open(Directory.FullPath);
+        }
+
+        public BoardViewModel CreateBoard() => new(Repository, Config, Dialogs);
+
+        public TagsViewModel CreateTags() => new(Repository, Config, Dialogs);
+
+        public WorkspaceViewModel CreateWorkspace() =>
+            new(Session, new Interaction<Unit>(), new Interaction<Unit>(), Config, Dialogs);
+
+        public void Dispose()
+        {
+            Session.Dispose();
+            Directory.Dispose();
+        }
+    }
+
+    private static string[] VisibleTitles(BoardViewModel board) =>
+        board.Columns.SelectMany(column => column.Cards).Select(card => card.Title).Order(StringComparer.Ordinal).ToArray();
+
+    /// <summary>Moves a visible card through its menu command.</summary>
+    private static Task MoveAsync(BoardViewModel board, long cardId, long columnId) =>
+        board.Columns.SelectMany(column => column.Cards).Single(card => card.Card.Id == cardId)
+            .MoveToCommand.ExecuteAsync(columnId);
+
+    #region Search
+
+    [TestMethod]
+    public async Task SearchFiltersCardsAndKeepsEmptyColumns()
+    {
+        using var fixture = new Fixture();
+        ColumnModel first = fixture.Repository.AddColumn("A", "");
+        ColumnModel second = fixture.Repository.AddColumn("B", "");
+        TagModel bug = fixture.Repository.AddTag("bug", new RgbColor(1, 2, 3), "");
+        fixture.Repository.AddCard(first.Id, "crash", "", [bug.Id]);
+        fixture.Repository.AddCard(second.Id, "idea", "", []);
+        BoardViewModel board = fixture.CreateBoard();
+
+        board.SearchText = "tag:BUG";
+        await board.SearchCommand.ExecuteAsync(null);
+
+        CollectionAssert.AreEqual(new[] { "crash" }, VisibleTitles(board));
+        Assert.AreEqual(2, board.Columns.Count);
+        Assert.AreEqual(0, board.Columns[1].CardCount);
+        Assert.IsNotNull(board.ActiveFilter);
+        Assert.AreEqual(0, fixture.Dialogs.Shown.Count);
+    }
+
+    [TestMethod]
+    public async Task InvalidSearchShowsTheErrorAndKeepsTextAndPreviousResult()
+    {
+        using var fixture = new Fixture();
+        ColumnModel column = fixture.Repository.AddColumn("A", "");
+        fixture.Repository.AddCard(column.Id, "alpha", "", []);
+        fixture.Repository.AddCard(column.Id, "beta", "", []);
+        BoardViewModel board = fixture.CreateBoard();
+        board.SearchText = "alpha";
+        await board.SearchCommand.ExecuteAsync(null);
+
+        board.SearchText = "alpha AND";
+        await board.SearchCommand.ExecuteAsync(null);
+
+        var error = (MessageDialogViewModel)fixture.Dialogs.Shown.Single();
+        Assert.AreEqual(Resources.Search_Error_Title, error.Title);
+        Assert.AreEqual("alpha AND", board.SearchText);
+        CollectionAssert.AreEqual(new[] { "alpha" }, VisibleTitles(board));
+    }
+
+    [TestMethod]
+    public async Task WritesRefreshWithTheLastSuccessfulExpressionNotTheBoxText()
+    {
+        using var fixture = new Fixture();
+        ColumnModel first = fixture.Repository.AddColumn("A", "");
+        ColumnModel second = fixture.Repository.AddColumn("B", "");
+        CardModel alpha = fixture.Repository.AddCard(first.Id, "alpha", "", []);
+        fixture.Repository.AddCard(first.Id, "beta", "", []);
+        BoardViewModel board = fixture.CreateBoard();
+        board.SearchText = "alpha";
+        await board.SearchCommand.ExecuteAsync(null);
+
+        board.SearchText = "beta";
+        await MoveAsync(board, alpha.Id, second.Id);
+
+        CollectionAssert.AreEqual(new[] { "alpha" }, VisibleTitles(board));
+        Assert.AreEqual(1, board.Columns[1].CardCount);
+    }
+
+    [TestMethod]
+    public async Task BlankSearchAndClearShowEveryCard()
+    {
+        using var fixture = new Fixture();
+        ColumnModel column = fixture.Repository.AddColumn("A", "");
+        fixture.Repository.AddCard(column.Id, "alpha", "", []);
+        fixture.Repository.AddCard(column.Id, "beta", "", []);
+        BoardViewModel board = fixture.CreateBoard();
+
+        board.SearchText = "alpha";
+        await board.SearchCommand.ExecuteAsync(null);
+        board.SearchText = "   ";
+        await board.SearchCommand.ExecuteAsync(null);
+        Assert.IsNull(board.ActiveFilter);
+        CollectionAssert.AreEqual(new[] { "alpha", "beta" }, VisibleTitles(board));
+
+        board.SearchText = "alpha";
+        await board.SearchCommand.ExecuteAsync(null);
+        Assert.IsTrue(board.HasSearchText);
+        board.ClearSearchCommand.Execute(null);
+
+        Assert.AreEqual("", board.SearchText);
+        Assert.IsFalse(board.HasSearchText);
+        Assert.IsNull(board.ActiveFilter);
+        CollectionAssert.AreEqual(new[] { "alpha", "beta" }, VisibleTitles(board));
+    }
+
+    [TestMethod]
+    public async Task DataWrittenIsRaisedForWritesButNotForSearchOrSort()
+    {
+        using var fixture = new Fixture();
+        ColumnModel first = fixture.Repository.AddColumn("A", "");
+        ColumnModel second = fixture.Repository.AddColumn("B", "");
+        CardModel card = fixture.Repository.AddCard(first.Id, "x", "", []);
+        BoardViewModel board = fixture.CreateBoard();
+        int raised = 0;
+        board.DataWritten += (_, _) => raised++;
+
+        board.SearchText = "x";
+        await board.SearchCommand.ExecuteAsync(null);
+        board.SelectedSort = board.SortOptions[1];
+        Assert.AreEqual(0, raised);
+
+        await MoveAsync(board, card.Id, second.Id);
+        Assert.AreEqual(1, raised);
+    }
+
+    #endregion
+
+    #region Tags tab
+
+    [TestMethod]
+    public void TagsListInIdOrderWithUsageCounts()
+    {
+        using var fixture = new Fixture();
+        ColumnModel column = fixture.Repository.AddColumn("A", "");
+        TagModel bug = fixture.Repository.AddTag("bug", new RgbColor(1, 2, 3), "Broken");
+        TagModel unused = fixture.Repository.AddTag("unused", new RgbColor(4, 5, 6), "");
+        fixture.Repository.AddCard(column.Id, "a", "", [bug.Id]);
+        fixture.Repository.AddCard(column.Id, "b", "", [bug.Id]);
+
+        TagsViewModel tags = fixture.CreateTags();
+
+        CollectionAssert.AreEqual(new[] { bug.Id, unused.Id }, tags.Tags.Select(row => row.Tag.Id).ToArray());
+        CollectionAssert.AreEqual(new long[] { 2, 0 }, tags.Tags.Select(row => row.UsageCount).ToArray());
+        Assert.IsTrue(tags.Tags[0].HasDescription);
+        Assert.AreEqual("#010203", tags.Tags[0].ColorText);
+        Assert.IsFalse(tags.IsEmpty);
+    }
+
+    [TestMethod]
+    public async Task NewTagIsWrittenAndAnnounced()
+    {
+        using var fixture = new Fixture();
+        TagsViewModel tags = fixture.CreateTags();
+        int changed = 0;
+        tags.TagsChanged += (_, _) => changed++;
+        fixture.Dialogs.Script = dialog =>
+        {
+            var editor = (TagEditorDialogViewModel)dialog;
+            editor.Name = "ui";
+            editor.PickSwatchCommand.Execute(TagColors.Palette[2].ToString());
+            editor.Description = "Looks";
+            editor.ConfirmCommand.Execute(null);
+            return Task.CompletedTask;
+        };
+
+        await tags.AddTagCommand.ExecuteAsync(null);
+
+        TagModel created = fixture.Repository.GetTags().Single();
+        Assert.AreEqual("ui", created.Name);
+        Assert.AreEqual(TagColors.Palette[2], created.Color);
+        Assert.AreEqual("Looks", created.Description);
+        Assert.AreEqual(1, tags.Tags.Count);
+        Assert.AreEqual(1, changed);
+    }
+
+    [TestMethod]
+    public async Task TagEditorKeepsTheDialogOpenOnDuplicateNameOrInvalidColor()
+    {
+        using var fixture = new Fixture();
+        fixture.Repository.AddTag("Bug", new RgbColor(1, 2, 3), "");
+        TagsViewModel tags = fixture.CreateTags();
+        TagEditorDialogViewModel? editor = null;
+        bool closed = false;
+        fixture.Dialogs.Script = dialog =>
+        {
+            editor = (TagEditorDialogViewModel)dialog;
+            editor.CloseRequested += (_, _) => closed = true;
+            editor.Name = "bug";
+            editor.ConfirmCommand.Execute(null);
+            return Task.CompletedTask;
+        };
+
+        await tags.AddTagCommand.ExecuteAsync(null);
+
+        Assert.IsNotNull(editor);
+        Assert.IsTrue(editor.HasError);
+        Assert.IsFalse(closed);
+        Assert.AreEqual("bug", editor.Name);
+
+        editor.Name = "other";
+        editor.Color = "red";
+        editor.ConfirmCommand.Execute(null);
+        Assert.AreEqual(Resources.Error_Tag_InvalidColor, editor.ErrorMessage);
+        Assert.IsFalse(closed);
+        Assert.AreEqual(1, fixture.Repository.GetTags().Count);
+    }
+
+    [TestMethod]
+    public async Task EditingATagRenamesRecolorsAndDescribesIt()
+    {
+        using var fixture = new Fixture();
+        TagModel tag = fixture.Repository.AddTag("bug", new RgbColor(1, 2, 3), "");
+        TagsViewModel tags = fixture.CreateTags();
+        fixture.Dialogs.Script = dialog =>
+        {
+            var editor = (TagEditorDialogViewModel)dialog;
+            Assert.AreEqual("bug", editor.Name);
+            Assert.AreEqual("#010203", editor.Color);
+            editor.Name = "defect";
+            editor.Color = "#ABCDEF";
+            editor.Description = "Broken";
+            editor.ConfirmCommand.Execute(null);
+            return Task.CompletedTask;
+        };
+
+        await tags.Tags[0].EditCommand.ExecuteAsync(null);
+
+        TagModel updated = fixture.Repository.GetTags().Single();
+        Assert.AreEqual(tag.Id, updated.Id);
+        Assert.AreEqual("defect", updated.Name);
+        Assert.AreEqual(new RgbColor(0xab, 0xcd, 0xef), updated.Color);
+        Assert.AreEqual("Broken", updated.Description);
+        Assert.AreEqual("defect", tags.Tags[0].Badge.Name);
+    }
+
+    [TestMethod]
+    public async Task DeletingATagAsksFirstAndKeepsTheCards()
+    {
+        using var fixture = new Fixture();
+        ColumnModel column = fixture.Repository.AddColumn("A", "");
+        TagModel bug = fixture.Repository.AddTag("bug", new RgbColor(1, 2, 3), "");
+        CardModel card = fixture.Repository.AddCard(column.Id, "a", "", [bug.Id]);
+        TagsViewModel tags = fixture.CreateTags();
+
+        fixture.Dialogs.Script = ScriptedDialogService.AnswerConfirmations(false);
+        await tags.Tags[0].DeleteCommand.ExecuteAsync(null);
+        Assert.AreEqual(1, fixture.Repository.GetTags().Count);
+
+        fixture.Dialogs.Script = ScriptedDialogService.AnswerConfirmations(true);
+        await tags.Tags[0].DeleteCommand.ExecuteAsync(null);
+
+        Assert.AreEqual(0, fixture.Repository.GetTags().Count);
+        Assert.IsTrue(tags.IsEmpty);
+        CardModel kept = fixture.Repository.GetCard(card.Id)!;
+        Assert.AreEqual(0, kept.Tags.Count);
+    }
+
+    [TestMethod]
+    public async Task DeletingATagWithoutConfirmationShowsNoDialog()
+    {
+        using var fixture = new Fixture();
+        fixture.Repository.AddTag("bug", new RgbColor(1, 2, 3), "");
+        fixture.Config.Confirmations.DeleteTag = false;
+        TagsViewModel tags = fixture.CreateTags();
+
+        await tags.Tags[0].DeleteCommand.ExecuteAsync(null);
+
+        Assert.AreEqual(0, fixture.Dialogs.Shown.Count);
+        Assert.AreEqual(0, fixture.Repository.GetTags().Count);
+    }
+
+    #endregion
+
+    #region Workspace wiring and export
+
+    [TestMethod]
+    public async Task TagWritesRefreshTheBoardAndBoardWritesRefreshTheTags()
+    {
+        using var fixture = new Fixture();
+        ColumnModel first = fixture.Repository.AddColumn("A", "");
+        ColumnModel second = fixture.Repository.AddColumn("B", "");
+        TagModel bug = fixture.Repository.AddTag("bug", new RgbColor(1, 2, 3), "");
+        CardModel card = fixture.Repository.AddCard(first.Id, "a", "", [bug.Id]);
+        WorkspaceViewModel workspace = fixture.CreateWorkspace();
+
+        // A filtered board drops the card once the tag is gone.
+        workspace.Board.SearchText = "tag:bug";
+        await workspace.Board.SearchCommand.ExecuteAsync(null);
+        fixture.Dialogs.Script = ScriptedDialogService.AnswerConfirmations(true);
+        await workspace.Tags.Tags[0].DeleteCommand.ExecuteAsync(null);
+        Assert.AreEqual(0, workspace.Board.Columns.Sum(column => column.CardCount));
+
+        // Re-tag through the repository, then a board write updates the usage count.
+        workspace.Board.ClearSearchCommand.Execute(null);
+        TagModel ui = fixture.Repository.AddTag("ui", new RgbColor(4, 5, 6), "");
+        fixture.Repository.UpdateCard(card.Id, "a", "", [ui.Id]);
+        Assert.AreEqual(0, workspace.Tags.Tags.Count);
+        await MoveAsync(workspace.Board, card.Id, second.Id);
+        Assert.AreEqual(1, workspace.Tags.Tags.Single().UsageCount);
+    }
+
+    [TestMethod]
+    public async Task ExportWritesTheWholeWorkspaceIgnoringTheSearch()
+    {
+        using var fixture = new Fixture();
+        ColumnModel column = fixture.Repository.AddColumn("A", "");
+        fixture.Repository.AddCard(column.Id, "alpha", "", []);
+        fixture.Repository.AddCard(column.Id, "beta", "", []);
+        WorkspaceViewModel workspace = fixture.CreateWorkspace();
+        workspace.Board.SearchText = "alpha";
+        await workspace.Board.SearchCommand.ExecuteAsync(null);
+
+        string path = Path.Combine(fixture.Directory.FullPath, "out.md");
+        fixture.Dialogs.SaveFilePath = path;
+        await workspace.ExportCommand.ExecuteAsync(null);
+
+        string suggested = fixture.Dialogs.SuggestedFileNames.Single();
+        StringAssert.StartsWith(suggested, workspace.WorkspaceName);
+        StringAssert.EndsWith(suggested, ".md");
+        string markdown = File.ReadAllText(path);
+        StringAssert.Contains(markdown, "alpha");
+        StringAssert.Contains(markdown, "beta");
+        byte[] bytes = File.ReadAllBytes(path);
+        Assert.AreNotEqual(0xEF, bytes[0], "The export must not start with a UTF-8 BOM.");
+        Assert.AreEqual(0, fixture.Dialogs.Shown.Count);
+    }
+
+    [TestMethod]
+    public async Task CancelledExportWritesNothing()
+    {
+        using var fixture = new Fixture();
+        WorkspaceViewModel workspace = fixture.CreateWorkspace();
+        fixture.Dialogs.SaveFilePath = null;
+
+        await workspace.ExportCommand.ExecuteAsync(null);
+
+        Assert.AreEqual(1, fixture.Dialogs.SuggestedFileNames.Count);
+        Assert.AreEqual(0, fixture.Dialogs.Shown.Count);
+        Assert.AreEqual(0, System.IO.Directory.GetFiles(fixture.Directory.FullPath, "*.md").Length);
+    }
+
+    [TestMethod]
+    public async Task ExportWriteFailureIsReportedInAMessageDialog()
+    {
+        using var fixture = new Fixture();
+        WorkspaceViewModel workspace = fixture.CreateWorkspace();
+        fixture.Dialogs.SaveFilePath = Path.Combine(fixture.Directory.FullPath, "missing-folder", "out.md");
+
+        await workspace.ExportCommand.ExecuteAsync(null);
+
+        var message = (MessageDialogViewModel)fixture.Dialogs.Shown.Single();
+        Assert.AreEqual(Resources.Export_Failed_Title, message.Title);
+        Assert.IsTrue(message.HasDetails);
+    }
+
+    #endregion
+}

YKanBan/Assets/Locales/Resources.resx

@@ -340,4 +340,52 @@
   <data name="Error_Operation_Message" xml:space="preserve">
     <value>The change could not be written to the workspace. The board shows the stored state.</value>
   </data>
+  <data name="TagEditor_TitleNew" xml:space="preserve">
+    <value>New tag</value>
+  </data>
+  <data name="TagEditor_TitleEdit" xml:space="preserve">
+    <value>Edit tag</value>
+  </data>
+  <data name="TagEditor_ColorLabel" xml:space="preserve">
+    <value>Color</value>
+  </data>
+  <data name="Tags_AddTag" xml:space="preserve">
+    <value>New tag</value>
+  </data>
+  <data name="Tags_Summary" xml:space="preserve">
+    <value>{0} tag(s)</value>
+  </data>
+  <data name="Tags_UsageCount" xml:space="preserve">
+    <value>{0} card(s)</value>
+  </data>
+  <data name="Tags_Empty" xml:space="preserve">
+    <value>No tags yet.</value>
+  </data>
+  <data name="Confirm_DeleteTag" xml:space="preserve">
+    <value>Delete tag "{0}"? It will be removed from {1} card(s).</value>
+  </data>
+  <data name="Board_SearchWatermark" xml:space="preserve">
+    <value>Search, e.g. tag:bug OR title:login</value>
+  </data>
+  <data name="Board_Search" xml:space="preserve">
+    <value>Search</value>
+  </data>
+  <data name="Board_ClearSearch" xml:space="preserve">
+    <value>Clear</value>
+  </data>
+  <data name="Search_Error_Title" xml:space="preserve">
+    <value>Invalid search</value>
+  </data>
+  <data name="Search_Error_Message" xml:space="preserve">
+    <value>The query expression is invalid. Details: {0}</value>
+  </data>
+  <data name="Export_FileTypeMarkdown" xml:space="preserve">
+    <value>Markdown document</value>
+  </data>
+  <data name="Export_Failed_Title" xml:space="preserve">
+    <value>Export failed</value>
+  </data>
+  <data name="Export_Failed_Message" xml:space="preserve">
+    <value>The export file could not be written.</value>
+  </data>
 </root>

YKanBan/Assets/Locales/Resources.zh-Hans.resx

@@ -340,4 +340,52 @@
   <data name="Error_Operation_Message" xml:space="preserve">
     <value>更改未能写入工作区，看板显示的是已保存的状态。</value>
   </data>
+  <data name="TagEditor_TitleNew" xml:space="preserve">
+    <value>新建标签</value>
+  </data>
+  <data name="TagEditor_TitleEdit" xml:space="preserve">
+    <value>编辑标签</value>
+  </data>
+  <data name="TagEditor_ColorLabel" xml:space="preserve">
+    <value>颜色</value>
+  </data>
+  <data name="Tags_AddTag" xml:space="preserve">
+    <value>新建标签</value>
+  </data>
+  <data name="Tags_Summary" xml:space="preserve">
+    <value>共 {0} 个标签</value>
+  </data>
+  <data name="Tags_UsageCount" xml:space="preserve">
+    <value>{0} 张卡片</value>
+  </data>
+  <data name="Tags_Empty" xml:space="preserve">
+    <value>还没有标签。</value>
+  </data>
+  <data name="Confirm_DeleteTag" xml:space="preserve">
+    <value>删除标签“{0}”？将从 {1} 张卡片移除该标签。</value>
+  </data>
+  <data name="Board_SearchWatermark" xml:space="preserve">
+    <value>搜索，例如 tag:bug OR title:登录</value>
+  </data>
+  <data name="Board_Search" xml:space="preserve">
+    <value>搜索</value>
+  </data>
+  <data name="Board_ClearSearch" xml:space="preserve">
+    <value>清空</value>
+  </data>
+  <data name="Search_Error_Title" xml:space="preserve">
+    <value>搜索表达式错误</value>
+  </data>
+  <data name="Search_Error_Message" xml:space="preserve">
+    <value>查询表达式有误，详情：{0}</value>
+  </data>
+  <data name="Export_FileTypeMarkdown" xml:space="preserve">
+    <value>Markdown 文档</value>
+  </data>
+  <data name="Export_Failed_Title" xml:space="preserve">
+    <value>导出失败</value>
+  </data>
+  <data name="Export_Failed_Message" xml:space="preserve">
+    <value>无法写入导出文件。</value>
+  </data>
 </root>

YKanBan/ViewModels/Board/BoardViewModel.cs

@@ -11,8 +11,12 @@ using YKanBan.ViewModels.Dialogs;
 namespace YKanBan.ViewModels.Board;
 
 /// <summary>
-/// The board tab: the toolbar (new column, column width, card sort) and the
+/// The board tab: the toolbar (search bar, new column, column width, card sort)
-/// columns laid out left to right, each listing its cards top to bottom.
+/// and the columns laid out left to right, each listing its cards top to bottom.
+///
+/// The search runs only on an explicit search (button or Enter), never while
+/// typing. An invalid expression is reported in a message dialog and changes
+/// nothing: the box keeps its text and the board keeps the previous result.
 ///
 /// Every write is followed by <see cref="Refresh"/>, which re-queries with the
 /// most recently successful search expression (<see cref="ActiveFilter"/>), not
@@ -50,6 +54,12 @@ public sealed partial class BoardViewModel : ViewModelBase
         Refresh();
     }
 
+    /// <summary>
+    /// Raised after every board write (the refresh included), so the tags tab
+    /// can update its usage counts.
+    /// </summary>
+    public event EventHandler? DataWritten;
+
     /// <summary>
     /// Gets the columns in id order.
     /// </summary>
@@ -70,6 +80,18 @@ public sealed partial class BoardViewModel : ViewModelBase
     /// </summary>
     public CompiledSearch? ActiveFilter { get; set; }
 
+    /// <summary>
+    /// Gets or sets the search box text; it only takes effect on <see cref="SearchCommand"/>.
+    /// </summary>
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(HasSearchText))]
+    private string searchText = "";
+
+    /// <summary>
+    /// Gets whether the search box holds text (shows the clear button).
+    /// </summary>
+    public bool HasSearchText => SearchText.Length > 0;
+
     /// <summary>
     /// Gets or sets the selected card sort option; changing it is persisted and re-sorts the board.
     /// </summary>
@@ -99,6 +121,43 @@ public sealed partial class BoardViewModel : ViewModelBase
         }
     }
 
+    /// <summary>
+    /// Parses and runs the search box text; blank text shows every card. An
+    /// invalid expression only shows the error dialog.
+    /// </summary>
+    /// <returns>A task completing after the refresh or the error dialog.</returns>
+    [RelayCommand]
+    private async Task SearchAsync()
+    {
+        CompiledSearch? filter;
+        try
+        {
+            SearchNode? query = SearchQueryParser.Parse(SearchText);
+            filter = query is null ? null : SearchSqlCompiler.Compile(query);
+        }
+        catch (SearchSyntaxException exception)
+        {
+            await _dialogs.ShowMessageAsync(
+                Resources.Search_Error_Title,
+                string.Format(Resources.Culture, Resources.Search_Error_Message, exception.Message));
+            return;
+        }
+
+        ActiveFilter = filter;
+        Refresh();
+    }
+
+    /// <summary>
+    /// Empties the search box and shows every card again.
+    /// </summary>
+    [RelayCommand]
+    private void ClearSearch()
+    {
+        SearchText = "";
+        ActiveFilter = null;
+        Refresh();
+    }
+
     /// <summary>
     /// Opens the new-column dialog.
     /// </summary>
@@ -109,7 +168,7 @@ public sealed partial class BoardViewModel : ViewModelBase
         var dialog = new ColumnEditorDialogViewModel(null, (title, description) => _repository.AddColumn(title, description));
         if (await _dialogs.ShowAsync(dialog))
         {
-            Refresh();
+            RefreshAfterWrite();
         }
     }
 
@@ -137,7 +196,7 @@ public sealed partial class BoardViewModel : ViewModelBase
             column, (title, description) => _repository.UpdateColumn(column.Id, title, description));
         if (await _dialogs.ShowAsync(dialog))
         {
-            Refresh();
+            RefreshAfterWrite();
         }
     }
 
@@ -176,7 +235,7 @@ public sealed partial class BoardViewModel : ViewModelBase
         await _dialogs.ShowAsync(editor);
 
         // Refresh even after a cancel: the nested picker may have created tags.
-        Refresh();
+        RefreshAfterWrite();
     }
 
     /// <summary>
@@ -196,7 +255,7 @@ public sealed partial class BoardViewModel : ViewModelBase
         var editor = CardEditorDialogViewModel.ForExistingCard(
             _repository, _dialogs, card, _config.Confirmations.DiscardEdit);
         await _dialogs.ShowAsync(editor);
-        Refresh();
+        RefreshAfterWrite();
     }
 
     /// <summary>
@@ -255,7 +314,16 @@ public sealed partial class BoardViewModel : ViewModelBase
             await _dialogs.ShowMessageAsync(
                 Resources.Error_Operation_Title, Resources.Error_Operation_Message, exception.Message);
         }
+        RefreshAfterWrite();
+    }
+
+    /// <summary>
+    /// Refreshes after a write and announces it.
+    /// </summary>
+    private void RefreshAfterWrite()
+    {
         Refresh();
+        DataWritten?.Invoke(this, EventArgs.Empty);
     }
 
     /// <summary>

YKanBan/ViewModels/Dialogs/IDialogService.cs

@@ -13,6 +13,13 @@ public interface IDialogService
     /// <param name="dialog">The dialog view model; its window is resolved by naming convention.</param>
     /// <returns>The dialog result: <see langword="true"/> when it was accepted.</returns>
     Task<bool> ShowAsync(DialogViewModelBase dialog);
+
+    /// <summary>
+    /// Shows the system save-file dialog for a Markdown file.
+    /// </summary>
+    /// <param name="suggestedFileName">The proposed file name.</param>
+    /// <returns>The chosen local path, or <see langword="null"/> when the user cancelled.</returns>
+    Task<string?> PickSaveFilePathAsync(string suggestedFileName);
 }
 
 /// <summary>

YKanBan/ViewModels/Dialogs/TagColors.cs

@@ -0,0 +1,26 @@
+using YKanBan.Models;
+
+namespace YKanBan.ViewModels.Dialogs;
+
+/// <summary>
+/// The default colors proposed for new tags, shared by the tag picker and the
+/// tag editor.
+/// </summary>
+public static class TagColors
+{
+    /// <summary>
+    /// Gets the palette, offered as swatches and cycled for new-tag defaults.
+    /// </summary>
+    public static IReadOnlyList<RgbColor> Palette { get; } =
+    [
+        new(0xd7, 0x3a, 0x4a), new(0x00, 0x75, 0xca), new(0x0e, 0x8a, 0x16), new(0xfb, 0xca, 0x04),
+        new(0x7c, 0x3a, 0xed), new(0xe9, 0x9b, 0x3c), new(0x00, 0x8b, 0x8b), new(0xcf, 0xd3, 0xd7),
+    ];
+
+    /// <summary>
+    /// Returns the default color of a new tag, cycled by the number of existing tags.
+    /// </summary>
+    /// <param name="existingCount">The number of tags already in the workspace.</param>
+    /// <returns>The proposed color.</returns>
+    public static RgbColor DefaultFor(int existingCount) => Palette[existingCount % Palette.Count];
+}

YKanBan/ViewModels/Dialogs/TagEditorDialogViewModel.cs

@@ -0,0 +1,146 @@
+using Avalonia.Media;
+using Avalonia.Media.Immutable;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using YKanBan.Models;
+
+namespace YKanBan.ViewModels.Dialogs;
+
+/// <summary>
+/// The new-tag / edit-tag dialog of the tags tab: name (required, not trimmed),
+/// #RRGGBB color with palette swatches and a live preview, and an optional
+/// description. Confirming writes through the supplied save callback; an invalid
+/// color or a schema-constraint violation (empty or duplicate name) is shown
+/// inside the dialog, which stays open with the user's input intact.
+/// </summary>
+public sealed partial class TagEditorDialogViewModel : DialogViewModelBase
+{
+    private readonly Action<string, RgbColor, string> _save;
+
+    /// <summary>
+    /// Initializes the dialog.
+    /// </summary>
+    /// <param name="existing">The tag being edited, or <see langword="null"/> for a new tag.</param>
+    /// <param name="defaultColor">The color proposed for a new tag.</param>
+    /// <param name="save">Writes the name, color and description; throws the repository's typed exceptions.</param>
+    public TagEditorDialogViewModel(TagModel? existing, RgbColor defaultColor, Action<string, RgbColor, string> save)
+    {
+        _save = save;
+        Title = existing is null ? Resources.TagEditor_TitleNew : Resources.TagEditor_TitleEdit;
+        name = existing?.Name ?? "";
+        color = (existing?.Color ?? defaultColor).ToString();
+        description = existing?.Description ?? "";
+        Swatches = TagColors.Palette.Select(swatch => new ColorSwatch(swatch.ToString(), ToBrush(swatch))).ToList();
+        UpdateColorPreview();
+    }
+
+    /// <summary>
+    /// Gets the localized window title.
+    /// </summary>
+    public string Title { get; }
+
+    /// <summary>
+    /// Gets the palette swatches; clicking one sets <see cref="Color"/>.
+    /// </summary>
+    public IReadOnlyList<ColorSwatch> Swatches { get; }
+
+    /// <summary>
+    /// Gets or sets the tag name being edited (not trimmed).
+    /// </summary>
+    [ObservableProperty]
+    private string name;
+
+    /// <summary>
+    /// Gets or sets the #RRGGBB color text being edited.
+    /// </summary>
+    [ObservableProperty]
+    private string color;
+
+    /// <summary>
+    /// Gets or sets the tag description being edited.
+    /// </summary>
+    [ObservableProperty]
+    private string description;
+
+    /// <summary>
+    /// Gets the preview of <see cref="Color"/>, transparent while it is not valid.
+    /// </summary>
+    [ObservableProperty]
+    private IBrush colorPreview = Brushes.Transparent;
+
+    /// <summary>
+    /// Gets the localized error of the last confirmation, or <see langword="null"/>.
+    /// </summary>
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(HasError))]
+    private string? errorMessage;
+
+    /// <summary>
+    /// Gets whether an error is shown.
+    /// </summary>
+    public bool HasError => ErrorMessage is not null;
+
+    /// <summary>
+    /// Takes a swatch color.
+    /// </summary>
+    /// <param name="hex">The swatch's #RRGGBB text.</param>
+    [RelayCommand]
+    private void PickSwatch(string hex) => Color = hex;
+
+    /// <summary>
+    /// Writes the tag; closes on success, otherwise shows the error.
+    /// </summary>
+    [RelayCommand]
+    private void Confirm()
+    {
+        if (!RgbColor.TryParse(Color, out RgbColor parsed))
+        {
+            ErrorMessage = Resources.Error_Tag_InvalidColor;
+            return;
+        }
+
+        try
+        {
+            _save(Name, parsed, Description);
+        }
+        catch (Exception exception)
+        {
+            ErrorMessage = WriteErrorMessages.Describe(exception);
+            return;
+        }
+        Close(true);
+    }
+
+    /// <summary>
+    /// Closes without writing.
+    /// </summary>
+    [RelayCommand]
+    private Task CancelAsync() => RequestCancelAsync();
+
+    /// <summary>
+    /// Refreshes the color preview.
+    /// </summary>
+    /// <param name="value">The new color text.</param>
+    partial void OnColorChanged(string value) => UpdateColorPreview();
+
+    /// <summary>
+    /// Recomputes <see cref="ColorPreview"/> from <see cref="Color"/>.
+    /// </summary>
+    private void UpdateColorPreview() =>
+        ColorPreview = RgbColor.TryParse(Color, out RgbColor parsed) ? ToBrush(parsed) : Brushes.Transparent;
+
+    /// <summary>
+    /// Creates the thread-agnostic brush of a tag color.
+    /// </summary>
+    /// <param name="value">The color.</param>
+    /// <returns>The brush.</returns>
+    private static IBrush ToBrush(RgbColor value) =>
+        new ImmutableSolidColorBrush(Avalonia.Media.Color.FromRgb(value.R, value.G, value.B));
+}
+
+/// <summary>
+/// A palette swatch of the tag editor.
+/// </summary>
+/// <param name="Hex">The #RRGGBB text.</param>
+/// <param name="Brush">The fill.</param>
+public sealed record ColorSwatch(string Hex, IBrush Brush);

YKanBan/ViewModels/Dialogs/TagPickerDialogViewModel.cs

@@ -21,15 +21,6 @@ namespace YKanBan.ViewModels.Dialogs;
 /// </summary>
 public sealed partial class TagPickerDialogViewModel : DialogViewModelBase
 {
-    /// <summary>
-    /// Default colors proposed for new tags, cycled by the number of existing tags.
-    /// </summary>
-    private static readonly RgbColor[] Palette =
-    [
-        new(0xd7, 0x3a, 0x4a), new(0x00, 0x75, 0xca), new(0x0e, 0x8a, 0x16), new(0xfb, 0xca, 0x04),
-        new(0x7c, 0x3a, 0xed), new(0xe9, 0x9b, 0x3c), new(0x00, 0x8b, 0x8b), new(0xcf, 0xd3, 0xd7),
-    ];
-
     private readonly WorkspaceRepository _repository;
     private readonly IReadOnlyList<TagBadgeViewModel> _available;
 
@@ -48,7 +39,7 @@ public sealed partial class TagPickerDialogViewModel : DialogViewModelBase
             .ToList();
         FilteredTags = new ObservableCollection<TagBadgeViewModel>(_available);
 
-        newColor = Palette[all.Count % Palette.Length].ToString();
+        newColor = TagColors.DefaultFor(all.Count).ToString();
         UpdateColorPreview();
     }
 

YKanBan/ViewModels/Tags/TagRowViewModel.cs

@@ -0,0 +1,77 @@
+using CommunityToolkit.Mvvm.Input;
+using YKanBan.Models;
+using YKanBan.ViewModels.Board;
+
+namespace YKanBan.ViewModels.Tags;
+
+/// <summary>
+/// One row of the tags tab: the colored badge, the description and the usage
+/// count, with edit and delete actions.
+/// </summary>
+public sealed partial class TagRowViewModel : ViewModelBase
+{
+    private readonly TagsViewModel _owner;
+
+    /// <summary>
+    /// Initializes the row.
+    /// </summary>
+    /// <param name="owner">The tags tab performing the actions.</param>
+    /// <param name="tag">The tag shown.</param>
+    /// <param name="usageCount">The number of cards carrying the tag.</param>
+    public TagRowViewModel(TagsViewModel owner, TagModel tag, long usageCount)
+    {
+        _owner = owner;
+        Tag = tag;
+        Badge = new TagBadgeViewModel(tag);
+        UsageCount = usageCount;
+    }
+
+    /// <summary>
+    /// Gets the tag shown.
+    /// </summary>
+    public TagModel Tag { get; }
+
+    /// <summary>
+    /// Gets the colored badge (color + name).
+    /// </summary>
+    public TagBadgeViewModel Badge { get; }
+
+    /// <summary>
+    /// Gets the tag description.
+    /// </summary>
+    public string Description => Tag.Description;
+
+    /// <summary>
+    /// Gets whether the tag has a description.
+    /// </summary>
+    public bool HasDescription => Tag.Description.Length > 0;
+
+    /// <summary>
+    /// Gets the #RRGGBB color text.
+    /// </summary>
+    public string ColorText => Tag.Color.ToString();
+
+    /// <summary>
+    /// Gets the number of cards carrying the tag.
+    /// </summary>
+    public long UsageCount { get; }
+
+    /// <summary>
+    /// Gets the localized usage count, for example "3 cards".
+    /// </summary>
+    public string UsageText => string.Format(Resources.Culture, Resources.Tags_UsageCount, UsageCount);
+
+    /// <summary>
+    /// Opens the edit dialog.
+    /// </summary>
+    /// <returns>A task completing when the dialog closes.</returns>
+    [RelayCommand]
+    private Task EditAsync() => _owner.EditTagAsync(Tag);
+
+    /// <summary>
+    /// Deletes the tag.
+    /// </summary>
+    /// <returns>A task completing when the tag is deleted or the deletion was declined.</returns>
+    [RelayCommand]
+    private Task DeleteAsync() => _owner.DeleteTagAsync(Tag, UsageCount);
+}

YKanBan/ViewModels/Tags/TagsViewModel.cs

@@ -0,0 +1,144 @@
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using CommunityToolkit.Mvvm.Input;
+using YKanBan.Models;
+using YKanBan.Storage.AppData;
+using YKanBan.Storage.Workspace;
+using YKanBan.ViewModels.Dialogs;
+
+namespace YKanBan.ViewModels.Tags;
+
+/// <summary>
+/// The tags tab, a tag manager in the style of the GitHub issue labels page:
+/// every tag with its color, name, description and usage count, plus creating,
+/// editing (rename, recolor, describe) and deleting tags. Unreferenced tags are
+/// never cleaned up automatically, so this is where they are removed.
+/// </summary>
+public sealed partial class TagsViewModel : ViewModelBase
+{
+    private readonly WorkspaceRepository _repository;
+    private readonly AppConfig _config;
+    private readonly IDialogService _dialogs;
+
+    /// <summary>
+    /// Initializes the tab and loads it.
+    /// </summary>
+    /// <param name="repository">The workspace repository.</param>
+    /// <param name="config">The live application configuration (delete confirmation).</param>
+    /// <param name="dialogs">The modal dialog service.</param>
+    public TagsViewModel(WorkspaceRepository repository, AppConfig config, IDialogService dialogs)
+    {
+        _repository = repository;
+        _config = config;
+        _dialogs = dialogs;
+        Refresh();
+    }
+
+    /// <summary>
+    /// Raised after every tag write, so the board can show the new names and colors.
+    /// </summary>
+    public event EventHandler? TagsChanged;
+
+    /// <summary>
+    /// Gets the tags in id order.
+    /// </summary>
+    public ObservableCollection<TagRowViewModel> Tags { get; } = [];
+
+    /// <summary>
+    /// Gets the localized total, for example "3 tags".
+    /// </summary>
+    public string Summary => string.Format(Resources.Culture, Resources.Tags_Summary, Tags.Count);
+
+    /// <summary>
+    /// Gets whether the workspace has no tags yet.
+    /// </summary>
+    public bool IsEmpty => Tags.Count == 0;
+
+    /// <summary>
+    /// Reloads the tags with their usage counts.
+    /// </summary>
+    public void Refresh()
+    {
+        Tags.Clear();
+        foreach ((TagModel tag, long usage) in _repository.GetTagsWithUsage())
+        {
+            Tags.Add(new TagRowViewModel(this, tag, usage));
+        }
+        OnPropertyChanged(nameof(Summary));
+        OnPropertyChanged(nameof(IsEmpty));
+    }
+
+    /// <summary>
+    /// Opens the new-tag dialog.
+    /// </summary>
+    /// <returns>A task completing when the dialog closes.</returns>
+    [RelayCommand]
+    private async Task AddTagAsync()
+    {
+        var dialog = new TagEditorDialogViewModel(
+            null,
+            TagColors.DefaultFor(Tags.Count),
+            (name, color, description) => _repository.AddTag(name, color, description));
+        if (await _dialogs.ShowAsync(dialog))
+        {
+            AfterWrite();
+        }
+    }
+
+    /// <summary>
+    /// Opens the edit-tag dialog.
+    /// </summary>
+    /// <param name="tag">The tag to edit.</param>
+    /// <returns>A task completing when the dialog closes.</returns>
+    internal async Task EditTagAsync(TagModel tag)
+    {
+        var dialog = new TagEditorDialogViewModel(
+            tag,
+            tag.Color,
+            (name, color, description) => _repository.UpdateTag(tag.Id, name, color, description));
+        if (await _dialogs.ShowAsync(dialog))
+        {
+            AfterWrite();
+        }
+    }
+
+    /// <summary>
+    /// Deletes a tag (removing it from its cards), asking first when that
+    /// confirmation is enabled.
+    /// </summary>
+    /// <param name="tag">The tag to delete.</param>
+    /// <param name="usageCount">The number of cards carrying it.</param>
+    /// <returns>A task completing when the tag is deleted or the deletion was declined.</returns>
+    internal async Task DeleteTagAsync(TagModel tag, long usageCount)
+    {
+        if (_config.Confirmations.DeleteTag)
+        {
+            string message = string.Format(Resources.Culture, Resources.Confirm_DeleteTag, tag.Name, usageCount);
+            if (!await _dialogs.ConfirmAsync(message, Resources.Common_Delete))
+            {
+                return;
+            }
+        }
+
+        try
+        {
+            _repository.DeleteTag(tag.Id);
+        }
+        catch (Exception exception)
+        {
+            Debug.WriteLine(exception);
+            await _dialogs.ShowMessageAsync(
+                Resources.Error_Operation_Title, Resources.Error_Operation_Message, exception.Message);
+        }
+        AfterWrite();
+    }
+
+    /// <summary>
+    /// Reloads the list and tells the board that tags changed.
+    /// </summary>
+    private void AfterWrite()
+    {
+        Refresh();
+        TagsChanged?.Invoke(this, EventArgs.Empty);
+    }
+}

YKanBan/ViewModels/WorkspaceViewModel.cs

@@ -1,20 +1,26 @@
+using System.Diagnostics;
+using System.Text;
 using CommunityToolkit.Mvvm.Input;
+using YKanBan.Export;
 using YKanBan.Storage.AppData;
 using YKanBan.Storage.Workspace;
 using YKanBan.ViewModels.Board;
 using YKanBan.ViewModels.Dialogs;
+using YKanBan.ViewModels.Tags;
 
 namespace YKanBan.ViewModels;
 
 /// <summary>
 /// The normal workspace view: the top display area (name, path and the export,
-/// settings and about buttons) plus the tags/board tabs. The tab contents are
+/// settings and about buttons) plus the board and tags tabs. A write on either
-/// filled in by the board and tag features.
+/// tab refreshes the other: tag edits change the board's badges and filter
+/// matches, card edits change the tags' usage counts.
 /// </summary>
 public sealed partial class WorkspaceViewModel : ViewModelBase
 {
     private readonly Interaction<Unit> _showSettings;
     private readonly Interaction<Unit> _showAbout;
+    private readonly IDialogService _dialogs;
 
     /// <summary>
     /// Initializes the view for an open workspace.
@@ -23,7 +29,7 @@ public sealed partial class WorkspaceViewModel : ViewModelBase
     /// <param name="showSettings">The interaction that opens the settings dialog.</param>
     /// <param name="showAbout">The interaction that opens the about dialog.</param>
     /// <param name="config">The live application configuration.</param>
-    /// <param name="dialogs">The modal dialog service of the board.</param>
+    /// <param name="dialogs">The modal dialog service.</param>
     public WorkspaceViewModel(
         WorkspaceSession session,
         Interaction<Unit> showSettings,
@@ -36,7 +42,11 @@ public sealed partial class WorkspaceViewModel : ViewModelBase
         WorkspacePath = session.FolderPath;
         _showSettings = showSettings;
         _showAbout = showAbout;
+        _dialogs = dialogs;
         Board = new BoardViewModel(session.Repository, config, dialogs);
+        Tags = new TagsViewModel(session.Repository, config, dialogs);
+        Board.DataWritten += (_, _) => Tags.Refresh();
+        Tags.TagsChanged += (_, _) => Board.Refresh();
     }
 
     /// <summary>
@@ -59,6 +69,11 @@ public sealed partial class WorkspaceViewModel : ViewModelBase
     /// </summary>
     public BoardViewModel Board { get; }
 
+    /// <summary>
+    /// Gets the tags tab.
+    /// </summary>
+    public TagsViewModel Tags { get; }
+
     /// <summary>
     /// Opens the settings dialog through the registered interaction.
     /// </summary>
@@ -72,11 +87,32 @@ public sealed partial class WorkspaceViewModel : ViewModelBase
     private async Task OpenAboutAsync() => await _showAbout.Handle(Unit.Value);
 
     /// <summary>
-    /// Raised by the export button; the export flow is wired up with the export
+    /// Exports the whole workspace to a Markdown file chosen in the system save
-    /// feature.
+    /// dialog. The export ignores the board's search filter and card sort; the
+    /// default file name and all template text follow the UI language.
     /// </summary>
+    /// <returns>A task completing when the file is written or the export was cancelled.</returns>
     [RelayCommand]
-    private static void Export()
+    private async Task ExportAsync()
     {
+        DateTimeOffset exportedAt = DateTimeOffset.Now;
+        string? path = await _dialogs.PickSaveFilePathAsync(MarkdownExporter.BuildFileName(WorkspaceName, exportedAt));
+        if (path is null)
+        {
+            return;
+        }
+
+        try
+        {
+            WorkspaceRepository repository = Session.Repository;
+            string markdown = MarkdownExporter.Export(
+                WorkspaceName, repository.GetColumns(), repository.GetCards(), repository.GetTagsWithUsage(), exportedAt);
+            await File.WriteAllTextAsync(path, markdown, new UTF8Encoding(encoderShouldEmitUTF8Identifier: false));
+        }
+        catch (Exception exception)
+        {
+            Debug.WriteLine(exception);
+            await _dialogs.ShowMessageAsync(Resources.Export_Failed_Title, Resources.Export_Failed_Message, exception.Message);
+        }
     }
 }

YKanBan/Views/Board/BoardView.axaml

@@ -13,29 +13,54 @@
 
     <Grid RowDefinitions="Auto,*" RowSpacing="8">
 
-        <!-- Toolbar. The search bar joins on the left with the search feature. -->
+        <!-- Toolbar: search bar on the left; new column, column width and card sort on the right. -->
-        <StackPanel Grid.Row="0" Orientation="Horizontal" HorizontalAlignment="Right" Spacing="8">
+        <Grid Grid.Row="0" ColumnDefinitions="*,Auto" ColumnSpacing="16">
-            <Button Command="{Binding AddColumnCommand}">
+            <StackPanel Grid.Column="0" Orientation="Horizontal" Spacing="8">
-                <StackPanel Orientation="Horizontal" Spacing="6">
+                <TextBox Text="{Binding SearchText}" Width="420"
-                    <icons:PackIconLucide Kind="Plus" Width="16" Height="16"/>
+                         Watermark="{x:Static lang:Resources.Board_SearchWatermark}">
-                    <TextBlock Text="{x:Static lang:Resources.Board_AddColumn}"/>
+                    <TextBox.KeyBindings>
-                </StackPanel>
+                        <KeyBinding Gesture="Enter" Command="{Binding SearchCommand}"/>
-            </Button>
+                    </TextBox.KeyBindings>
-            <Button Command="{Binding AdjustColumnWidthCommand}">
+                    <TextBox.InnerLeftContent>
-                <StackPanel Orientation="Horizontal" Spacing="6">
+                        <icons:PackIconLucide Kind="Search" Width="14" Height="14" Margin="8,0,0,0" Opacity="0.6"
-                    <icons:PackIconLucide Kind="MoveHorizontal" Width="16" Height="16"/>
+                                              VerticalAlignment="Center"/>
-                    <TextBlock Text="{x:Static lang:Resources.Board_ColumnWidth}"/>
+                    </TextBox.InnerLeftContent>
-                </StackPanel>
+                    <TextBox.InnerRightContent>
-            </Button>
+                        <Button Command="{Binding ClearSearchCommand}" IsVisible="{Binding HasSearchText}"
-            <ComboBox ItemsSource="{Binding SortOptions}" SelectedItem="{Binding SelectedSort}" MinWidth="160"
+                                Theme="{StaticResource BorderlessButton}" Padding="6,0"
-                      ToolTip.Tip="{x:Static lang:Resources.Board_Sort}">
+                                MinHeight="0" Height="24" VerticalAlignment="Center"
-                <ComboBox.ItemTemplate>
+                                ToolTip.Tip="{x:Static lang:Resources.Board_ClearSearch}">
-                    <DataTemplate x:DataType="vmBase:OptionItem">
+                            <icons:PackIconLucide Kind="X" Width="14" Height="14"/>
-                        <TextBlock Text="{Binding Label}"/>
+                        </Button>
-                    </DataTemplate>
+                    </TextBox.InnerRightContent>
-                </ComboBox.ItemTemplate>
+                </TextBox>
-            </ComboBox>
+                <Button Command="{Binding SearchCommand}" Classes="Primary">
-        </StackPanel>
+                    <TextBlock Text="{x:Static lang:Resources.Board_Search}"/>
+                </Button>
+            </StackPanel>
+            <StackPanel Grid.Column="1" Orientation="Horizontal" Spacing="8">
+                <Button Command="{Binding AddColumnCommand}">
+                    <StackPanel Orientation="Horizontal" Spacing="6">
+                        <icons:PackIconLucide Kind="Plus" Width="16" Height="16"/>
+                        <TextBlock Text="{x:Static lang:Resources.Board_AddColumn}"/>
+                    </StackPanel>
+                </Button>
+                <Button Command="{Binding AdjustColumnWidthCommand}">
+                    <StackPanel Orientation="Horizontal" Spacing="6">
+                        <icons:PackIconLucide Kind="MoveHorizontal" Width="16" Height="16"/>
+                        <TextBlock Text="{x:Static lang:Resources.Board_ColumnWidth}"/>
+                    </StackPanel>
+                </Button>
+                <ComboBox ItemsSource="{Binding SortOptions}" SelectedItem="{Binding SelectedSort}" MinWidth="160"
+                          ToolTip.Tip="{x:Static lang:Resources.Board_Sort}">
+                    <ComboBox.ItemTemplate>
+                        <DataTemplate x:DataType="vmBase:OptionItem">
+                            <TextBlock Text="{Binding Label}"/>
+                        </DataTemplate>
+                    </ComboBox.ItemTemplate>
+                </ComboBox>
+            </StackPanel>
+        </Grid>
 
         <!-- Columns left to right; each column scrolls its own virtualized card list. -->
         <ScrollViewer Grid.Row="1" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Disabled">

YKanBan/Views/DialogService.cs

@@ -1,4 +1,5 @@
 using Avalonia.Controls;
+using Avalonia.Platform.Storage;
 using YKanBan.ViewModels.Dialogs;
 using YKanBan.Views.Dialogs;
 
@@ -50,6 +51,27 @@ public sealed class DialogService : IDialogService
         }
     }
 
+    /// <inheritdoc/>
+    public async Task<string?> PickSaveFilePathAsync(string suggestedFileName)
+    {
+        if (!_owners.TryPeek(out Window? owner))
+        {
+            throw new InvalidOperationException("The dialog service has no main window attached.");
+        }
+
+        IStorageFile? file = await owner.StorageProvider.SaveFilePickerAsync(new FilePickerSaveOptions
+        {
+            SuggestedFileName = suggestedFileName,
+            DefaultExtension = "md",
+            ShowOverwritePrompt = true,
+            FileTypeChoices =
+            [
+                new FilePickerFileType(YKanBan.Resources.Export_FileTypeMarkdown) { Patterns = ["*.md"] },
+            ],
+        });
+        return file?.TryGetLocalPath();
+    }
+
     /// <summary>
     /// Creates the window class matching a dialog view model by naming convention.
     /// </summary>

YKanBan/Views/Dialogs/ColumnEditorDialog.axaml

@@ -6,7 +6,7 @@
                       x:Class="YKanBan.Views.Dialogs.ColumnEditorDialog"
                       x:DataType="vm:ColumnEditorDialogViewModel"
                       Title="{Binding Title}"
-                      Width="440"
+                      SizeToContent="Height" Width="440"
                       WindowStartupLocation="CenterOwner">
 
     <StackPanel Margin="20" Spacing="14">

YKanBan/Views/Dialogs/TagEditorDialog.axaml

@@ -0,0 +1,61 @@
+<dialogs:DialogWindow xmlns="https://github.com/avaloniaui"
+                      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+                      xmlns:vm="using:YKanBan.ViewModels.Dialogs"
+                      xmlns:dialogs="using:YKanBan.Views.Dialogs"
+                      xmlns:lang="using:YKanBan"
+                      x:Class="YKanBan.Views.Dialogs.TagEditorDialog"
+                      x:DataType="vm:TagEditorDialogViewModel"
+                      x:Name="Root"
+                      Title="{Binding Title}"
+                      SizeToContent="Height" Width="440"
+                      WindowStartupLocation="CenterOwner">
+
+    <StackPanel Margin="20" Spacing="14">
+        <StackPanel Spacing="4">
+            <TextBlock Text="{x:Static lang:Resources.Field_Name}"/>
+            <TextBox Text="{Binding Name}"/>
+        </StackPanel>
+
+        <StackPanel Spacing="6">
+            <TextBlock Text="{x:Static lang:Resources.TagEditor_ColorLabel}"/>
+            <StackPanel Orientation="Horizontal" Spacing="8">
+                <TextBox Text="{Binding Color}" Width="120" Watermark="{x:Static lang:Resources.Field_Color}"/>
+                <Border Width="28" Height="28" CornerRadius="4" Background="{Binding ColorPreview}"
+                        BorderBrush="{DynamicResource PanelBorderBrush}" BorderThickness="1"/>
+            </StackPanel>
+            <ItemsControl ItemsSource="{Binding Swatches}">
+                <ItemsControl.ItemsPanel>
+                    <ItemsPanelTemplate>
+                        <StackPanel Orientation="Horizontal" Spacing="6"/>
+                    </ItemsPanelTemplate>
+                </ItemsControl.ItemsPanel>
+                <ItemsControl.ItemTemplate>
+                    <DataTemplate x:DataType="vm:ColorSwatch">
+                        <Button Command="{Binding #Root.((vm:TagEditorDialogViewModel)DataContext).PickSwatchCommand}"
+                                CommandParameter="{Binding Hex}"
+                                ToolTip.Tip="{Binding Hex}"
+                                Width="24" Height="24" Padding="0" CornerRadius="4"
+                                Background="{Binding Brush}"
+                                BorderBrush="{DynamicResource PanelBorderBrush}" BorderThickness="1"/>
+                    </DataTemplate>
+                </ItemsControl.ItemTemplate>
+            </ItemsControl>
+        </StackPanel>
+
+        <StackPanel Spacing="4">
+            <TextBlock Text="{x:Static lang:Resources.Field_Description}"/>
+            <TextBox Text="{Binding Description}" AcceptsReturn="True" TextWrapping="Wrap"
+                     MinHeight="72" MaxHeight="200"/>
+        </StackPanel>
+
+        <TextBlock Text="{Binding ErrorMessage}" IsVisible="{Binding HasError}"
+                   Foreground="{DynamicResource ErrorTextBrush}" TextWrapping="Wrap"/>
+
+        <StackPanel Orientation="Horizontal" HorizontalAlignment="Right" Spacing="8">
+            <Button Content="{x:Static lang:Resources.Common_Ok}" Command="{Binding ConfirmCommand}"
+                    Classes="Primary" MinWidth="90" IsDefault="True"/>
+            <Button Content="{x:Static lang:Resources.Common_Cancel}" Command="{Binding CancelCommand}"
+                    MinWidth="90" IsCancel="True"/>
+        </StackPanel>
+    </StackPanel>
+</dialogs:DialogWindow>

YKanBan/Views/Dialogs/TagEditorDialog.axaml.cs

@@ -0,0 +1,9 @@
+namespace YKanBan.Views.Dialogs;
+
+public partial class TagEditorDialog : DialogWindow
+{
+    public TagEditorDialog()
+    {
+        InitializeComponent();
+    }
+}

YKanBan/Views/Tags/TagsView.axaml

@@ -0,0 +1,76 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:vm="using:YKanBan.ViewModels.Tags"
+             xmlns:lang="using:YKanBan"
+             xmlns:icons="using:IconPacks.Avalonia.Lucide"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             mc:Ignorable="d" d:DesignWidth="1000" d:DesignHeight="600"
+             x:Class="YKanBan.Views.Tags.TagsView"
+             x:DataType="vm:TagsViewModel">
+
+    <Grid RowDefinitions="Auto,*" RowSpacing="8">
+
+        <!-- Toolbar: tag total on the left, new tag on the right. -->
+        <Grid Grid.Row="0" ColumnDefinitions="*,Auto">
+            <TextBlock Grid.Column="0" Text="{Binding Summary}" VerticalAlignment="Center" Opacity="0.7"/>
+            <Button Grid.Column="1" Command="{Binding AddTagCommand}">
+                <StackPanel Orientation="Horizontal" Spacing="6">
+                    <icons:PackIconLucide Kind="Plus" Width="16" Height="16"/>
+                    <TextBlock Text="{x:Static lang:Resources.Tags_AddTag}"/>
+                </StackPanel>
+            </Button>
+        </Grid>
+
+        <!-- Tag list: badge, description, usage count, edit and delete. -->
+        <Border Grid.Row="1" BorderBrush="{DynamicResource PanelBorderBrush}" BorderThickness="1" CornerRadius="6">
+            <Panel>
+                <ItemsControl ItemsSource="{Binding Tags}">
+                    <ItemsControl.Template>
+                        <ControlTemplate>
+                            <ScrollViewer HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Auto">
+                                <ItemsPresenter Name="PART_ItemsPresenter" ItemsPanel="{TemplateBinding ItemsPanel}"/>
+                            </ScrollViewer>
+                        </ControlTemplate>
+                    </ItemsControl.Template>
+                    <ItemsControl.ItemsPanel>
+                        <ItemsPanelTemplate>
+                            <VirtualizingStackPanel/>
+                        </ItemsPanelTemplate>
+                    </ItemsControl.ItemsPanel>
+                    <ItemsControl.ItemTemplate>
+                        <DataTemplate x:DataType="vm:TagRowViewModel">
+                            <Border BorderBrush="{DynamicResource PanelBorderBrush}" BorderThickness="0,0,0,1"
+                                    Padding="16,10">
+                                <Grid ColumnDefinitions="240,*,Auto,Auto" ColumnSpacing="16">
+                                    <Border Grid.Column="0" HorizontalAlignment="Left" VerticalAlignment="Center"
+                                            Background="{Binding Badge.Background}" CornerRadius="10" Padding="10,2"
+                                            ToolTip.Tip="{Binding ColorText}">
+                                        <TextBlock Text="{Binding Badge.Name}" Foreground="{Binding Badge.Foreground}"
+                                                   FontSize="12" TextTrimming="CharacterEllipsis"/>
+                                    </Border>
+                                    <TextBlock Grid.Column="1" Text="{Binding Description}" VerticalAlignment="Center"
+                                               Opacity="0.75" TextTrimming="CharacterEllipsis"/>
+                                    <TextBlock Grid.Column="2" Text="{Binding UsageText}" VerticalAlignment="Center"
+                                               Opacity="0.7"/>
+                                    <StackPanel Grid.Column="3" Orientation="Horizontal" Spacing="4">
+                                        <Button Command="{Binding EditCommand}" Theme="{StaticResource BorderlessButton}"
+                                                Padding="6" ToolTip.Tip="{x:Static lang:Resources.Menu_Edit}">
+                                            <icons:PackIconLucide Kind="Pencil" Width="14" Height="14"/>
+                                        </Button>
+                                        <Button Command="{Binding DeleteCommand}" Theme="{StaticResource BorderlessButton}"
+                                                Padding="6" ToolTip.Tip="{x:Static lang:Resources.Menu_Delete}">
+                                            <icons:PackIconLucide Kind="Trash2" Width="14" Height="14"/>
+                                        </Button>
+                                    </StackPanel>
+                                </Grid>
+                            </Border>
+                        </DataTemplate>
+                    </ItemsControl.ItemTemplate>
+                </ItemsControl>
+                <TextBlock Text="{x:Static lang:Resources.Tags_Empty}" IsVisible="{Binding IsEmpty}"
+                           HorizontalAlignment="Center" VerticalAlignment="Center" Opacity="0.6"/>
+            </Panel>
+        </Border>
+    </Grid>
+</UserControl>

YKanBan/Views/Tags/TagsView.axaml.cs

@@ -0,0 +1,11 @@
+using Avalonia.Controls;
+
+namespace YKanBan.Views.Tags;
+
+public partial class TagsView : UserControl
+{
+    public TagsView()
+    {
+        InitializeComponent();
+    }
+}

YKanBan/Views/WorkspaceView.axaml

@@ -48,12 +48,14 @@
             </Grid>
         </Border>
 
-        <!-- Board and tags tabs; the tags tab is filled in by the tag feature. -->
+        <!-- Board and tags tabs. -->
         <TabControl Grid.Row="1" Margin="8">
             <TabItem Header="{x:Static lang:Resources.Tab_Board}">
                 <ContentControl Content="{Binding Board}" Margin="0,8,0,0"/>
             </TabItem>
-            <TabItem Header="{x:Static lang:Resources.Tab_Tags}"/>
+            <TabItem Header="{x:Static lang:Resources.Tab_Tags}">
+                <ContentControl Content="{Binding Tags}" Margin="0,8,0,0"/>
+            </TabItem>
         </TabControl>
 
     </Grid>

docs/PLAN.md

@@ -374,7 +374,7 @@ phrase  := '"' 任意文本 '"'   （内部支持转义：\" → 字面引号，
 | M4 GUI 框架 | 已完成 | 主题/图标接入、主窗口布局（顶部区 + TabControl + 全窗口错误页体系）、设置/关于模态；全 UI 文本资源化（硬规则生效）、语言设置项、RTL/FlowDirection 检测；亮/暗/跟随系统主题基础设施与设置项、ThemeDictionaries 颜色硬规则 | 人工 |
 | **M4R v1.9 回补** | 已完成 | 见下方清单 | 本地 Windows build + test 通过；新增页面人工 |
 | M5 看板界面 | 已完成（待人工验收） | 看板 tab 全部交互与模态（含约束冲突模态内提示、卡片列表虚拟化、嵌套模态新建标签立即写库、写库后按最近成功表达式刷新） | 人工 |
-| M6 标签与搜索集成 | 待办 | 标签 tab、搜索执行与空列保留、导出接线（含文件名/时间戳 i18n 模式） | 人工 |
+| M6 标签与搜索集成 | 已完成（待人工验收） | 标签 tab、搜索执行与空列保留、导出接线（含文件名/时间戳 i18n 模式） | 人工 |
 | M7 发布与文档 | 待办 | 单一 workflow（4 RID 矩阵 build→test→artifact，osx-x64 用 Intel 运行器）文件就绪（结构自查）、根目录 USAGE.md、README（引用 USAGE.md）、人工验收清单（含语言切换重启生效、导出语言跟随界面、主题三态切换、app.json 多实例脏写四项） | workflow 结构自查通过；实际触发与产物验证视网络条件推迟 |
 
 **M4R 清单**（v1.9 对已完成里程碑的回补，进入 M5 前完成）：