Complete phase E1: DayState Fluxor

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude/settings.local.json

@@ -6,7 +6,8 @@
       "Bash(dotnet test:*)",
       "Bash(git checkout:*)",
       "Bash(git add:*)",
-      "Bash(git commit:*)"
+      "Bash(git commit:*)",
+      "Bash(mkdir:*)"
     ]
   }
 }

docs/IMPLEMENTATION_PLAN.md

@@ -341,7 +341,7 @@ NavMenu.razor:
 | ✓ | D2 | Personen | Person Pages | 1 Razor |
 | ✓ | D3 | Expenses | ExpenseState Fluxor | 4 State-Dateien |
 | ✓ | D4 | Expenses | Expense Pages | 1 Razor |
-| ☐ | E1 | Days | DayState Fluxor | 4 State-Dateien |
+| ✓ | E1 | Days | DayState Fluxor | 4 State-Dateien |
 | ☐ | E2 | Days | Days List Page | 1 Razor |
 | ☐ | E3 | Days | Day Details Page | 1 Razor |
 | ☐ | E4 | Days | PersonExpense Management | Components in DayDetails |

src/Koogle.Web/Store/DayState/DayActions.cs

@@ -0,0 +1,171 @@
+using Koogle.Application.DTOs;
+
+namespace Koogle.Web.Store.DayState;
+
+// Load Days Actions
+
+/// <summary>
+/// Action to load all days for the current club.
+/// </summary>
+public record LoadDaysAction(DayFilterDto? Filter = null);
+
+/// <summary>
+/// Action dispatched when days are loaded successfully.
+/// </summary>
+public record LoadDaysSuccessAction(IReadOnlyList<DaySummaryDto> Days);
+
+/// <summary>
+/// Action dispatched when loading days fails.
+/// </summary>
+public record LoadDaysFailureAction(string Error);
+
+// Load Day Details Actions
+
+/// <summary>
+/// Action to load a single day with full details.
+/// </summary>
+public record LoadDayDetailsAction(Guid DayId);
+
+/// <summary>
+/// Action dispatched when day details are loaded successfully.
+/// </summary>
+public record LoadDayDetailsSuccessAction(DayDto Day);
+
+/// <summary>
+/// Action dispatched when loading day details fails.
+/// </summary>
+public record LoadDayDetailsFailureAction(string Error);
+
+// Create Day Actions
+
+/// <summary>
+/// Action to create a new day.
+/// </summary>
+public record CreateDayAction(CreateDayDto Dto);
+
+/// <summary>
+/// Action dispatched when day is created successfully.
+/// </summary>
+public record CreateDaySuccessAction(DayDto Day);
+
+/// <summary>
+/// Action dispatched when creating day fails.
+/// </summary>
+public record CreateDayFailureAction(string Error);
+
+// Update Day Actions
+
+/// <summary>
+/// Action to update an existing day.
+/// </summary>
+public record UpdateDayAction(UpdateDayDto Dto);
+
+/// <summary>
+/// Action dispatched when day is updated successfully.
+/// </summary>
+public record UpdateDaySuccessAction(DayDto Day);
+
+/// <summary>
+/// Action dispatched when updating day fails.
+/// </summary>
+public record UpdateDayFailureAction(string Error);
+
+// Delete Day Actions
+
+/// <summary>
+/// Action to delete a day.
+/// </summary>
+public record DeleteDayAction(Guid Id);
+
+/// <summary>
+/// Action dispatched when day is deleted successfully.
+/// </summary>
+public record DeleteDaySuccessAction(Guid Id);
+
+/// <summary>
+/// Action dispatched when deleting day fails.
+/// </summary>
+public record DeleteDayFailureAction(string Error);
+
+// Participant Actions
+
+/// <summary>
+/// Action to add a participant to a day.
+/// </summary>
+public record AddDayParticipantAction(AddDayParticipantDto Dto);
+
+/// <summary>
+/// Action dispatched when participant is added successfully.
+/// </summary>
+public record AddDayParticipantSuccessAction(DayDto Day);
+
+/// <summary>
+/// Action dispatched when adding participant fails.
+/// </summary>
+public record AddDayParticipantFailureAction(string Error);
+
+/// <summary>
+/// Action to remove a participant from a day.
+/// </summary>
+public record RemoveDayParticipantAction(RemoveDayParticipantDto Dto);
+
+/// <summary>
+/// Action dispatched when participant is removed successfully.
+/// </summary>
+public record RemoveDayParticipantSuccessAction(DayDto Day);
+
+/// <summary>
+/// Action dispatched when removing participant fails.
+/// </summary>
+public record RemoveDayParticipantFailureAction(string Error);
+
+// Status Actions
+
+/// <summary>
+/// Action to advance day status (New → Started → Closed).
+/// </summary>
+public record AdvanceDayStatusAction(Guid DayId);
+
+/// <summary>
+/// Action dispatched when status is advanced successfully.
+/// </summary>
+public record AdvanceDayStatusSuccessAction(DayDto Day);
+
+/// <summary>
+/// Action dispatched when advancing status fails.
+/// </summary>
+public record AdvanceDayStatusFailureAction(string Error);
+
+// Available Persons Actions
+
+/// <summary>
+/// Action to load available persons for participant selection.
+/// </summary>
+public record LoadAvailablePersonsAction;
+
+/// <summary>
+/// Action dispatched when available persons are loaded successfully.
+/// </summary>
+public record LoadAvailablePersonsSuccessAction(IReadOnlyList<PersonDto> Persons);
+
+/// <summary>
+/// Action dispatched when loading available persons fails.
+/// </summary>
+public record LoadAvailablePersonsFailureAction(string Error);
+
+// Selection and Error Actions
+
+/// <summary>
+/// Action to select a day for editing.
+/// </summary>
+public record SelectDayAction(DayDto? Day);
+
+/// <summary>
+/// Action to clear day error state.
+/// </summary>
+public record ClearDayErrorAction;
+
+/// <summary>
+/// Action to set filter for day list.
+/// </summary>
+public record SetDayFilterAction(DayFilterDto? Filter);

src/Koogle.Web/Store/DayState/DayEffects.cs

@@ -0,0 +1,221 @@
+using Fluxor;
+using Koogle.Application.Interfaces;
+
+namespace Koogle.Web.Store.DayState;
+
+/// <summary>
+/// Side effects for day state management.
+/// Handles async operations like API calls.
+/// </summary>
+public class DayEffects
+{
+    private readonly IDayService _dayService;
+    private readonly IPersonService _personService;
+    private readonly ILogger<DayEffects> _logger;
+
+    /// <summary>
+    /// Initializes a new instance of the DayEffects class.
+    /// </summary>
+    public DayEffects(IDayService dayService, IPersonService personService, ILogger<DayEffects> logger)
+    {
+        _dayService = dayService;
+        _personService = personService;
+        _logger = logger;
+    }
+
+    /// <summary>
+    /// Handles LoadDaysAction - loads all days from service.
+    /// </summary>
+    [EffectMethod]
+    public async Task HandleLoadDays(LoadDaysAction action, IDispatcher dispatcher)
+    {
+        try
+        {
+            _logger.LogDebug("Loading days with filter {@Filter}", action.Filter);
+            var result = await _dayService.GetAllAsync(action.Filter);
+            dispatcher.Dispatch(new LoadDaysSuccessAction(result.Items));
+            _logger.LogInformation("Loaded {Count} days", result.Items.Count);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to load days");
+            dispatcher.Dispatch(new LoadDaysFailureAction(ex.Message));
+        }
+    }
+
+    /// <summary>
+    /// Handles LoadDayDetailsAction - loads day details from service.
+    /// </summary>
+    [EffectMethod]
+    public async Task HandleLoadDayDetails(LoadDayDetailsAction action, IDispatcher dispatcher)
+    {
+        try
+        {
+            _logger.LogDebug("Loading day details for {DayId}", action.DayId);
+            var day = await _dayService.GetByIdAsync(action.DayId);
+
+            if (day is null)
+            {
+                dispatcher.Dispatch(new LoadDayDetailsFailureAction("Spieltag nicht gefunden."));
+                return;
+            }
+
+            dispatcher.Dispatch(new LoadDayDetailsSuccessAction(day));
+            _logger.LogInformation("Loaded day details for {DayId}", action.DayId);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to load day details for {DayId}", action.DayId);
+            dispatcher.Dispatch(new LoadDayDetailsFailureAction(ex.Message));
+        }
+    }
+
+    /// <summary>
+    /// Handles CreateDayAction - creates a new day.
+    /// </summary>
+    [EffectMethod]
+    public async Task HandleCreateDay(CreateDayAction action, IDispatcher dispatcher)
+    {
+        try
+        {
+            _logger.LogDebug("Creating day for {PostDate}", action.Dto.PostDate);
+            var day = await _dayService.CreateAsync(action.Dto);
+            dispatcher.Dispatch(new CreateDaySuccessAction(day));
+            _logger.LogInformation("Created day {Id} for {PostDate}", day.Id, day.PostDate);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to create day for {PostDate}", action.Dto.PostDate);
+            dispatcher.Dispatch(new CreateDayFailureAction(ex.Message));
+        }
+    }
+
+    /// <summary>
+    /// Handles UpdateDayAction - updates an existing day.
+    /// </summary>
+    [EffectMethod]
+    public async Task HandleUpdateDay(UpdateDayAction action, IDispatcher dispatcher)
+    {
+        try
+        {
+            _logger.LogDebug("Updating day {Id}", action.Dto.Id);
+            var day = await _dayService.UpdateAsync(action.Dto);
+            dispatcher.Dispatch(new UpdateDaySuccessAction(day));
+            _logger.LogInformation("Updated day {Id}", day.Id);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to update day {Id}", action.Dto.Id);
+            dispatcher.Dispatch(new UpdateDayFailureAction(ex.Message));
+        }
+    }
+
+    /// <summary>
+    /// Handles DeleteDayAction - deletes a day.
+    /// </summary>
+    [EffectMethod]
+    public async Task HandleDeleteDay(DeleteDayAction action, IDispatcher dispatcher)
+    {
+        try
+        {
+            _logger.LogDebug("Deleting day {Id}", action.Id);
+            var success = await _dayService.DeleteAsync(action.Id);
+
+            if (success)
+            {
+                dispatcher.Dispatch(new DeleteDaySuccessAction(action.Id));
+                _logger.LogInformation("Deleted day {Id}", action.Id);
+            }
+            else
+            {
+                dispatcher.Dispatch(new DeleteDayFailureAction("Spieltag konnte nicht gelöscht werden."));
+                _logger.LogWarning("Failed to delete day {Id} - not found or already deleted", action.Id);
+            }
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to delete day {Id}", action.Id);
+            dispatcher.Dispatch(new DeleteDayFailureAction(ex.Message));
+        }
+    }
+
+    /// <summary>
+    /// Handles AddDayParticipantAction - adds participant to day.
+    /// </summary>
+    [EffectMethod]
+    public async Task HandleAddDayParticipant(AddDayParticipantAction action, IDispatcher dispatcher)
+    {
+        try
+        {
+            _logger.LogDebug("Adding participant {PersonId} to day {DayId}", action.Dto.PersonId, action.Dto.DayId);
+            var day = await _dayService.AddParticipantAsync(action.Dto);
+            dispatcher.Dispatch(new AddDayParticipantSuccessAction(day));
+            _logger.LogInformation("Added participant {PersonId} to day {DayId}", action.Dto.PersonId, action.Dto.DayId);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to add participant {PersonId} to day {DayId}", action.Dto.PersonId, action.Dto.DayId);
+            dispatcher.Dispatch(new AddDayParticipantFailureAction(ex.Message));
+        }
+    }
+
+    /// <summary>
+    /// Handles RemoveDayParticipantAction - removes participant from day.
+    /// </summary>
+    [EffectMethod]
+    public async Task HandleRemoveDayParticipant(RemoveDayParticipantAction action, IDispatcher dispatcher)
+    {
+        try
+        {
+            _logger.LogDebug("Removing participant {PersonId} from day {DayId}", action.Dto.PersonId, action.Dto.DayId);
+            var day = await _dayService.RemoveParticipantAsync(action.Dto);
+            dispatcher.Dispatch(new RemoveDayParticipantSuccessAction(day));
+            _logger.LogInformation("Removed participant {PersonId} from day {DayId}", action.Dto.PersonId, action.Dto.DayId);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to remove participant {PersonId} from day {DayId}", action.Dto.PersonId, action.Dto.DayId);
+            dispatcher.Dispatch(new RemoveDayParticipantFailureAction(ex.Message));
+        }
+    }
+
+    /// <summary>
+    /// Handles AdvanceDayStatusAction - advances day status.
+    /// </summary>
+    [EffectMethod]
+    public async Task HandleAdvanceDayStatus(AdvanceDayStatusAction action, IDispatcher dispatcher)
+    {
+        try
+        {
+            _logger.LogDebug("Advancing status for day {DayId}", action.DayId);
+            var day = await _dayService.AdvanceStatusAsync(action.DayId);
+            dispatcher.Dispatch(new AdvanceDayStatusSuccessAction(day));
+            _logger.LogInformation("Advanced status for day {DayId} to {Status}", action.DayId, day.Status);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to advance status for day {DayId}", action.DayId);
+            dispatcher.Dispatch(new AdvanceDayStatusFailureAction(ex.Message));
+        }
+    }
+
+    /// <summary>
+    /// Handles LoadAvailablePersonsAction - loads all persons for selection.
+    /// </summary>
+    [EffectMethod]
+    public async Task HandleLoadAvailablePersons(LoadAvailablePersonsAction action, IDispatcher dispatcher)
+    {
+        try
+        {
+            _logger.LogDebug("Loading available persons");
+            var persons = await _personService.GetAllAsync();
+            dispatcher.Dispatch(new LoadAvailablePersonsSuccessAction(persons));
+            _logger.LogInformation("Loaded {Count} available persons", persons.Count);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to load available persons");
+            dispatcher.Dispatch(new LoadAvailablePersonsFailureAction(ex.Message));
+        }
+    }
+}

src/Koogle.Web/Store/DayState/DayReducers.cs

@@ -0,0 +1,423 @@
+using Fluxor;
+
+namespace Koogle.Web.Store.DayState;
+
+/// <summary>
+/// Reducers for day state management.
+/// </summary>
+public static class DayReducers
+{
+    // Load Days Reducers
+
+    /// <summary>
+    /// Handles LoadDaysAction - sets loading state and filter.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnLoadDays(DayState state, LoadDaysAction action)
+        => state with
+        {
+            IsLoading = true,
+            Error = null,
+            Filter = action.Filter
+        };
+
+    /// <summary>
+    /// Handles LoadDaysSuccessAction - updates days list.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnLoadDaysSuccess(DayState state, LoadDaysSuccessAction action)
+        => state with
+        {
+            Days = action.Days,
+            IsLoading = false
+        };
+
+    /// <summary>
+    /// Handles LoadDaysFailureAction - sets error state.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnLoadDaysFailure(DayState state, LoadDaysFailureAction action)
+        => state with
+        {
+            IsLoading = false,
+            Error = action.Error
+        };
+
+    // Load Day Details Reducers
+
+    /// <summary>
+    /// Handles LoadDayDetailsAction - sets loading state.
+    /// </summary>
+    [ReducerMethod(typeof(LoadDayDetailsAction))]
+    public static DayState OnLoadDayDetails(DayState state)
+        => state with
+        {
+            IsLoading = true,
+            Error = null
+        };
+
+    /// <summary>
+    /// Handles LoadDayDetailsSuccessAction - sets selected day.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnLoadDayDetailsSuccess(DayState state, LoadDayDetailsSuccessAction action)
+        => state with
+        {
+            SelectedDay = action.Day,
+            IsLoading = false
+        };
+
+    /// <summary>
+    /// Handles LoadDayDetailsFailureAction - sets error state.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnLoadDayDetailsFailure(DayState state, LoadDayDetailsFailureAction action)
+        => state with
+        {
+            IsLoading = false,
+            Error = action.Error
+        };
+
+    // Create Day Reducers
+
+    /// <summary>
+    /// Handles CreateDayAction - sets loading state.
+    /// </summary>
+    [ReducerMethod(typeof(CreateDayAction))]
+    public static DayState OnCreateDay(DayState state)
+        => state with
+        {
+            IsLoading = true,
+            Error = null
+        };
+
+    /// <summary>
+    /// Handles CreateDaySuccessAction - adds day summary to list and sets as selected.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnCreateDaySuccess(DayState state, CreateDaySuccessAction action)
+    {
+        var summary = new Application.DTOs.DaySummaryDto
+        {
+            Id = action.Day.Id,
+            PostDate = action.Day.PostDate,
+            Status = action.Day.Status,
+            ParticipantCount = action.Day.ParticipantCount
+        };
+
+        return state with
+        {
+            Days = [.. state.Days, summary],
+            SelectedDay = action.Day,
+            IsLoading = false
+        };
+    }
+
+    /// <summary>
+    /// Handles CreateDayFailureAction - sets error state.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnCreateDayFailure(DayState state, CreateDayFailureAction action)
+        => state with
+        {
+            IsLoading = false,
+            Error = action.Error
+        };
+
+    // Update Day Reducers
+
+    /// <summary>
+    /// Handles UpdateDayAction - sets loading state.
+    /// </summary>
+    [ReducerMethod(typeof(UpdateDayAction))]
+    public static DayState OnUpdateDay(DayState state)
+        => state with
+        {
+            IsLoading = true,
+            Error = null
+        };
+
+    /// <summary>
+    /// Handles UpdateDaySuccessAction - updates day in list and selected day.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnUpdateDaySuccess(DayState state, UpdateDaySuccessAction action)
+    {
+        var updatedDays = state.Days.Select(d =>
+            d.Id == action.Day.Id
+                ? new Application.DTOs.DaySummaryDto
+                {
+                    Id = action.Day.Id,
+                    PostDate = action.Day.PostDate,
+                    Status = action.Day.Status,
+                    ParticipantCount = action.Day.ParticipantCount
+                }
+                : d).ToList();
+
+        return state with
+        {
+            Days = updatedDays,
+            SelectedDay = state.SelectedDay?.Id == action.Day.Id ? action.Day : state.SelectedDay,
+            IsLoading = false
+        };
+    }
+
+    /// <summary>
+    /// Handles UpdateDayFailureAction - sets error state.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnUpdateDayFailure(DayState state, UpdateDayFailureAction action)
+        => state with
+        {
+            IsLoading = false,
+            Error = action.Error
+        };
+
+    // Delete Day Reducers
+
+    /// <summary>
+    /// Handles DeleteDayAction - sets loading state.
+    /// </summary>
+    [ReducerMethod(typeof(DeleteDayAction))]
+    public static DayState OnDeleteDay(DayState state)
+        => state with
+        {
+            IsLoading = true,
+            Error = null
+        };
+
+    /// <summary>
+    /// Handles DeleteDaySuccessAction - removes day from list.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnDeleteDaySuccess(DayState state, DeleteDaySuccessAction action)
+        => state with
+        {
+            Days = state.Days.Where(d => d.Id != action.Id).ToList(),
+            SelectedDay = state.SelectedDay?.Id == action.Id ? null : state.SelectedDay,
+            IsLoading = false
+        };
+
+    /// <summary>
+    /// Handles DeleteDayFailureAction - sets error state.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnDeleteDayFailure(DayState state, DeleteDayFailureAction action)
+        => state with
+        {
+            IsLoading = false,
+            Error = action.Error
+        };
+
+    // Participant Reducers
+
+    /// <summary>
+    /// Handles AddDayParticipantAction - sets loading state.
+    /// </summary>
+    [ReducerMethod(typeof(AddDayParticipantAction))]
+    public static DayState OnAddDayParticipant(DayState state)
+        => state with
+        {
+            IsLoading = true,
+            Error = null
+        };
+
+    /// <summary>
+    /// Handles AddDayParticipantSuccessAction - updates selected day and summary.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnAddDayParticipantSuccess(DayState state, AddDayParticipantSuccessAction action)
+    {
+        var updatedDays = state.Days.Select(d =>
+            d.Id == action.Day.Id
+                ? new Application.DTOs.DaySummaryDto
+                {
+                    Id = action.Day.Id,
+                    PostDate = action.Day.PostDate,
+                    Status = action.Day.Status,
+                    ParticipantCount = action.Day.ParticipantCount
+                }
+                : d).ToList();
+
+        return state with
+        {
+            Days = updatedDays,
+            SelectedDay = action.Day,
+            IsLoading = false
+        };
+    }
+
+    /// <summary>
+    /// Handles AddDayParticipantFailureAction - sets error state.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnAddDayParticipantFailure(DayState state, AddDayParticipantFailureAction action)
+        => state with
+        {
+            IsLoading = false,
+            Error = action.Error
+        };
+
+    /// <summary>
+    /// Handles RemoveDayParticipantAction - sets loading state.
+    /// </summary>
+    [ReducerMethod(typeof(RemoveDayParticipantAction))]
+    public static DayState OnRemoveDayParticipant(DayState state)
+        => state with
+        {
+            IsLoading = true,
+            Error = null
+        };
+
+    /// <summary>
+    /// Handles RemoveDayParticipantSuccessAction - updates selected day and summary.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnRemoveDayParticipantSuccess(DayState state, RemoveDayParticipantSuccessAction action)
+    {
+        var updatedDays = state.Days.Select(d =>
+            d.Id == action.Day.Id
+                ? new Application.DTOs.DaySummaryDto
+                {
+                    Id = action.Day.Id,
+                    PostDate = action.Day.PostDate,
+                    Status = action.Day.Status,
+                    ParticipantCount = action.Day.ParticipantCount
+                }
+                : d).ToList();
+
+        return state with
+        {
+            Days = updatedDays,
+            SelectedDay = action.Day,
+            IsLoading = false
+        };
+    }
+
+    /// <summary>
+    /// Handles RemoveDayParticipantFailureAction - sets error state.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnRemoveDayParticipantFailure(DayState state, RemoveDayParticipantFailureAction action)
+        => state with
+        {
+            IsLoading = false,
+            Error = action.Error
+        };
+
+    // Status Reducers
+
+    /// <summary>
+    /// Handles AdvanceDayStatusAction - sets loading state.
+    /// </summary>
+    [ReducerMethod(typeof(AdvanceDayStatusAction))]
+    public static DayState OnAdvanceDayStatus(DayState state)
+        => state with
+        {
+            IsLoading = true,
+            Error = null
+        };
+
+    /// <summary>
+    /// Handles AdvanceDayStatusSuccessAction - updates day status.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnAdvanceDayStatusSuccess(DayState state, AdvanceDayStatusSuccessAction action)
+    {
+        var updatedDays = state.Days.Select(d =>
+            d.Id == action.Day.Id
+                ? new Application.DTOs.DaySummaryDto
+                {
+                    Id = action.Day.Id,
+                    PostDate = action.Day.PostDate,
+                    Status = action.Day.Status,
+                    ParticipantCount = action.Day.ParticipantCount
+                }
+                : d).ToList();
+
+        return state with
+        {
+            Days = updatedDays,
+            SelectedDay = state.SelectedDay?.Id == action.Day.Id ? action.Day : state.SelectedDay,
+            IsLoading = false
+        };
+    }
+
+    /// <summary>
+    /// Handles AdvanceDayStatusFailureAction - sets error state.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnAdvanceDayStatusFailure(DayState state, AdvanceDayStatusFailureAction action)
+        => state with
+        {
+            IsLoading = false,
+            Error = action.Error
+        };
+
+    // Available Persons Reducers
+
+    /// <summary>
+    /// Handles LoadAvailablePersonsAction - sets loading state.
+    /// </summary>
+    [ReducerMethod(typeof(LoadAvailablePersonsAction))]
+    public static DayState OnLoadAvailablePersons(DayState state)
+        => state with
+        {
+            IsLoading = true,
+            Error = null
+        };
+
+    /// <summary>
+    /// Handles LoadAvailablePersonsSuccessAction - sets available persons.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnLoadAvailablePersonsSuccess(DayState state, LoadAvailablePersonsSuccessAction action)
+        => state with
+        {
+            AvailablePersons = action.Persons,
+            IsLoading = false
+        };
+
+    /// <summary>
+    /// Handles LoadAvailablePersonsFailureAction - sets error state.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnLoadAvailablePersonsFailure(DayState state, LoadAvailablePersonsFailureAction action)
+        => state with
+        {
+            IsLoading = false,
+            Error = action.Error
+        };
+
+    // Selection and Error Reducers
+
+    /// <summary>
+    /// Handles SelectDayAction - sets selected day.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnSelectDay(DayState state, SelectDayAction action)
+        => state with
+        {
+            SelectedDay = action.Day
+        };
+
+    /// <summary>
+    /// Handles ClearDayErrorAction - clears error state.
+    /// </summary>
+    [ReducerMethod(typeof(ClearDayErrorAction))]
+    public static DayState OnClearError(DayState state)
+        => state with
+        {
+            Error = null
+        };
+
+    /// <summary>
+    /// Handles SetDayFilterAction - sets filter.
+    /// </summary>
+    [ReducerMethod]
+    public static DayState OnSetDayFilter(DayState state, SetDayFilterAction action)
+        => state with
+        {
+            Filter = action.Filter
+        };
+}

src/Koogle.Web/Store/DayState/DayState.cs

@@ -0,0 +1,59 @@
+using Fluxor;
+using Koogle.Application.DTOs;
+
+namespace Koogle.Web.Store.DayState;
+
+/// <summary>
+/// Fluxor state for day management.
+/// </summary>
+[FeatureState]
+public record DayState
+{
+    /// <summary>
+    /// List of day summaries for the current club.
+    /// </summary>
+    public IReadOnlyList<DaySummaryDto> Days { get; init; } = [];
+
+    /// <summary>
+    /// Currently selected day with full details.
+    /// </summary>
+    public DayDto? SelectedDay { get; init; }
+
+    /// <summary>
+    /// Available persons for participant selection.
+    /// </summary>
+    public IReadOnlyList<PersonDto> AvailablePersons { get; init; } = [];
+
+    /// <summary>
+    /// Current filter for day list.
+    /// </summary>
+    public DayFilterDto? Filter { get; init; }
+
+    /// <summary>
+    /// Indicates whether a day operation is in progress.
+    /// </summary>
+    public bool IsLoading { get; init; }
+
+    /// <summary>
+    /// Error message if operation failed.
+    /// </summary>
+    public string? Error { get; init; }
+
+    /// <summary>
+    /// Private constructor for Fluxor initialization.
+    /// </summary>
+    private DayState() { }
+
+    /// <summary>
+    /// Creates the initial state.
+    /// </summary>
+    public static DayState Initial => new()
+    {
+        Days = [],
+        SelectedDay = null,
+        AvailablePersons = [],
+        Filter = null,
+        IsLoading = false,
+        Error = null
+    };
+}