feat(board): edit task deadlines

TaskTracker.Api/Pages/Board.cshtml.cs

@@ -151,7 +151,7 @@ public class BoardModel : PageModel
         return await ReturnBoardContentAsync();
     }
 
-    public async Task<IActionResult> OnPostCreateTaskAsync(string title, string? category)
+    public async Task<IActionResult> OnPostCreateTaskAsync(string title, string? category, DateTime? dueAt)
     {
         if (string.IsNullOrWhiteSpace(title))
             return BadRequest("Title is required.");
@@ -161,6 +161,7 @@ public class BoardModel : PageModel
             Title = title.Trim(),
             Category = category,
             Status = WorkTaskStatus.Pending,
+            DueAt = TaskDeadline.FromLocalInput(dueAt, TimeZoneInfo.Local),
         };
         await _taskRepo.CreateAsync(task);
 
@@ -176,7 +177,7 @@ public class BoardModel : PageModel
     }
 
     // Update task fields (inline edit)
-    public async Task<IActionResult> OnPutUpdateTaskAsync(int id, string? title, string? description, string? category, int? estimatedMinutes)
+    public async Task<IActionResult> OnPutUpdateTaskAsync(int id, string? title, string? description, string? category, int? estimatedMinutes, DateTime? dueAt, bool clearDueAt)
     {
         var task = await _taskRepo.GetByIdAsync(id);
         if (task is null) return NotFound();
@@ -185,6 +186,8 @@ public class BoardModel : PageModel
         if (description is not null) task.Description = description;
         if (category is not null) task.Category = category;
         if (estimatedMinutes.HasValue) task.EstimatedMinutes = estimatedMinutes;
+        if (clearDueAt) task.DueAt = null;
+        else if (dueAt.HasValue) task.DueAt = TaskDeadline.FromLocalInput(dueAt, TimeZoneInfo.Local);
 
         await _taskRepo.UpdateAsync(task);
         return Partial("Partials/_TaskDetail", task);

TaskTracker.Api/Pages/Partials/_CreateTaskForm.cshtml

@@ -8,4 +8,10 @@
            placeholder="New task..."
            class="input"
            autocomplete="off" />
+    <label for="new-task-deadline" class="sr-only">Deadline</label>
+    <input id="new-task-deadline"
+           type="datetime-local"
+           name="dueAt"
+           class="input"
+           aria-label="Deadline" />
 </form>

TaskTracker.Api/Pages/Partials/_TaskDetail.cshtml

@@ -14,6 +14,7 @@
     var (statusColor, statusLabel) = statusColors[Model.Status];
     var catColor = BoardModel.GetCategoryColor(Model.Category);
     var elapsed = BoardModel.FormatElapsed(Model.StartedAt, Model.CompletedAt);
+    var deadlineLocalValue = Model.DueAt?.LocalDateTime.ToString("yyyy-MM-ddTHH:mm");
 
     double? progressPercent = null;
     if (Model.EstimatedMinutes.HasValue && Model.StartedAt.HasValue)
@@ -139,6 +140,31 @@
                     <span style="color: var(--color-text-primary); font-variant-numeric: tabular-nums;">@elapsed</span>
                 </div>
 
+                <div style="display: flex; justify-content: space-between; align-items: center; font-size: 13px;">
+                    <span style="color: var(--color-text-secondary);">Deadline</span>
+                    <div class="inline-edit" id="edit-deadline" style="text-align: right;">
+                        <span class="inline-edit-display inline-edit-display--field"
+                              onclick="startEdit('deadline')"
+                              style="color: var(--color-text-primary); font-variant-numeric: tabular-nums; padding: 2px 8px;">
+                            @(deadlineLocalValue ?? "--")
+                        </span>
+                        <form class="inline-edit-form" style="display:none"
+                              hx-put="/board?handler=UpdateTask&id=@Model.Id"
+                              hx-target="#detail-panel"
+                              hx-swap="innerHTML">
+                            <label for="task-deadline-@Model.Id" class="sr-only">Deadline</label>
+                            <input id="task-deadline-@Model.Id" type="datetime-local" name="dueAt"
+                                   value="@deadlineLocalValue" class="inline-edit-input"
+                                   aria-label="Deadline" />
+                            <div style="display: flex; gap: 6px; margin-top: 6px;">
+                                <button type="submit" class="btn btn--sm btn--primary">Save</button>
+                                <button type="button" class="btn btn--sm btn--ghost" onclick="cancelEdit('deadline')">Cancel</button>
+                                <button type="submit" name="clearDueAt" value="true" class="btn btn--sm btn--ghost">Clear deadline</button>
+                            </div>
+                        </form>
+                    </div>
+                </div>
+
                 <div style="display: flex; justify-content: space-between; align-items: center; font-size: 13px;">
                     <span style="color: var(--color-text-secondary);">Estimate</span>
                     <div class="inline-edit" id="edit-estimate" style="text-align: right;">

TaskTracker.Api/Pages/Shared/TaskDeadline.cs

@@ -0,0 +1,12 @@
+namespace TaskTracker.Api.Pages;
+
+public static class TaskDeadline
+{
+    public static DateTimeOffset? FromLocalInput(DateTime? localValue, TimeZoneInfo timeZone)
+    {
+        if (!localValue.HasValue) return null;
+
+        var unspecified = DateTime.SpecifyKind(localValue.Value, DateTimeKind.Unspecified);
+        return new DateTimeOffset(unspecified, timeZone.GetUtcOffset(unspecified));
+    }
+}

TaskTracker.Tests/TaskDeadlineConversionTests.cs

@@ -0,0 +1,109 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Microsoft.AspNetCore.Mvc.ViewFeatures;
+using Microsoft.Extensions.DependencyInjection;
+using TaskTracker.Api.Pages;
+using TaskTracker.Core.Entities;
+using TaskTracker.Core.Enums;
+using TaskTracker.Core.Interfaces;
+using Xunit;
+
+namespace TaskTracker.Tests;
+
+public class TaskDeadlineConversionTests
+{
+    [Fact]
+    public void FromLocalInput_uses_the_supplied_time_zone_offset_for_an_unspecified_value()
+    {
+        var timeZone = TimeZoneInfo.CreateCustomTimeZone("TestZone", TimeSpan.FromHours(-4), "Test", "Test");
+        var localValue = new DateTime(2026, 8, 14, 11, 30, 0, DateTimeKind.Utc);
+
+        var dueAt = TaskDeadline.FromLocalInput(localValue, timeZone);
+
+        Assert.Equal(new DateTimeOffset(2026, 8, 14, 11, 30, 0, TimeSpan.FromHours(-4)), dueAt);
+    }
+
+    [Fact]
+    public void FromLocalInput_returns_null_for_a_blank_local_deadline()
+    {
+        var timeZone = TimeZoneInfo.CreateCustomTimeZone("TestZone", TimeSpan.FromHours(2), "Test", "Test");
+
+        var dueAt = TaskDeadline.FromLocalInput(null, timeZone);
+
+        Assert.Null(dueAt);
+    }
+
+    [Fact]
+    public async Task Board_create_assigns_due_at_from_local_deadline()
+    {
+        var repository = new InMemoryTaskRepository();
+        var board = CreateBoard(repository);
+        var localDeadline = new DateTime(2026, 8, 14, 11, 30, 0);
+
+        await board.OnPostCreateTaskAsync("deadline", null, localDeadline);
+
+        var created = Assert.Single(repository.Created);
+        var expected = TaskDeadline.FromLocalInput(localDeadline, TimeZoneInfo.Local);
+        Assert.Equal(expected, created.DueAt);
+    }
+
+    [Fact]
+    public async Task Board_update_explicit_clear_takes_precedence_over_a_supplied_deadline()
+    {
+        var existing = new WorkTask
+        {
+            Id = 1,
+            Title = "existing",
+            Status = WorkTaskStatus.Pending,
+            DueAt = new DateTimeOffset(2026, 8, 14, 11, 30, 0, TimeSpan.FromHours(-4)),
+        };
+        var repository = new InMemoryTaskRepository(existing);
+        var board = CreateBoard(repository);
+
+        var result = await board.OnPutUpdateTaskAsync(1, null, null, null, null, new DateTime(2026, 8, 15, 9, 0, 0), true);
+
+        Assert.IsType<PartialViewResult>(result);
+        Assert.Null(existing.DueAt);
+    }
+
+    private static BoardModel CreateBoard(ITaskRepository repository)
+    {
+        var board = new BoardModel(repository);
+        var services = new ServiceCollection()
+            .AddLogging()
+            .AddMvcCore()
+            .AddViews()
+            .Services
+            .BuildServiceProvider();
+        var httpContext = new DefaultHttpContext { RequestServices = services };
+        var provider = services.GetRequiredService<IModelMetadataProvider>();
+        board.PageContext = new PageContext
+        {
+            HttpContext = httpContext,
+            ViewData = new ViewDataDictionary(provider, new ModelStateDictionary()),
+        };
+        return board;
+    }
+
+    private sealed class InMemoryTaskRepository(params WorkTask[] tasks) : ITaskRepository
+    {
+        private readonly List<WorkTask> _tasks = [.. tasks];
+        public List<WorkTask> Created { get; } = [];
+
+        public Task<List<WorkTask>> GetAllAsync(WorkTaskStatus? status = null, int? parentId = null, bool includeSubTasks = false) =>
+            Task.FromResult(_tasks);
+        public Task<WorkTask?> GetByIdAsync(int id) => Task.FromResult(_tasks.SingleOrDefault(task => task.Id == id));
+        public Task<WorkTask?> GetActiveTaskAsync() => Task.FromResult(_tasks.SingleOrDefault(task => task.Status == WorkTaskStatus.Active));
+        public Task<List<WorkTask>> GetSubTasksAsync(int parentId) => Task.FromResult(_tasks.Where(task => task.ParentTaskId == parentId).ToList());
+        public Task<WorkTask> CreateAsync(WorkTask task)
+        {
+            Created.Add(task);
+            _tasks.Add(task);
+            return Task.FromResult(task);
+        }
+        public Task UpdateAsync(WorkTask task) => Task.CompletedTask;
+        public Task DeleteAsync(int id) => Task.CompletedTask;
+    }
+}