/// <summary>
/// Gets whether the navigator from a <see cref="SectionsNavigatorRequestType.ReportSectionStateChanged"/> request is active.
/// </summary>
/// <param name="sectionsNavigatorState"></param>
/// <param name="stackNavigator">The stack navigator that caused the <see cref="SectionsNavigatorRequestType.ReportSectionStateChanged"/> request if it's active. Null otherwhise.</param>
/// <returns>Returns true when the <see cref="IStackNavigator"/> that caused the current <see cref="SectionsNavigatorRequestType.ReportSectionStateChanged"/> is currently active. False otherwise.</returns>
public static bool IsStackNavigatorFromSectionsRequestActive(this SectionsNavigatorState sectionsNavigatorState, out IStackNavigator stackNavigator)
{
var sectionsNavigatorRequest = sectionsNavigatorState.LastRequest;
var modalName = sectionsNavigatorRequest.ModalName;
if (modalName != null)
{
stackNavigator = sectionsNavigatorState.Modals.FirstOrDefault(m => m.Name == modalName);
if (stackNavigator == null)
{
return(false);
}
else
{
return(stackNavigator == sectionsNavigatorState.ActiveModal);
}
}
else
{
var sectionName = sectionsNavigatorRequest.SectionName;
stackNavigator = sectionsNavigatorState.Sections[sectionName];
// Don't consider the section active if a Modal is active.
return(stackNavigator == sectionsNavigatorState.ActiveSection && sectionsNavigatorState.ActiveModal == null);
}
}
public SectionsNavigatorState(
SectionsNavigatorState state,
NavigatorRequestState lastRequestState,
SectionsNavigatorRequest lastRequest)
: this(state.Sections, state.ActiveSection, state.Modals, lastRequestState, lastRequest)
{
}
/// <summary>
/// Creates a new instance of <see cref="SectionsNavigatorBase"/>.
/// </summary>
/// <param name="defaultSections">The sections reachable by <see cref="SetActiveSection(CancellationToken, SectionsNavigatorRequest)"/> mapped by their name.</param>
public SectionsNavigatorBase(IReadOnlyDictionary <string, ISectionStackNavigator> defaultSections)
{
_logger = GetLogger();
State = new SectionsNavigatorState(
sections: defaultSections ?? new Dictionary <string, ISectionStackNavigator>(),
activeSection: null,
modals: new List <IModalStackNavigator>(),
lastRequestState: NavigatorRequestState.Processed,
lastRequest: null);
foreach (var section in defaultSections.Values)
{
section.StateChanged += OnSectionStateChanged;
}
}
public SectionsNavigatorEventArgs(SectionsNavigatorState previousState, SectionsNavigatorState currentState)
{
PreviousState = previousState;
CurrentState = currentState;
}
/// <summary>
/// Gets the type of the next page ViewModel assuming the current <paramref name="sectionsNavigatorState"/> has a <see cref="NavigatorRequestState.Processing"/> request.
/// Since the next page doesn't exist at that time, it's calculated using the request's type, parameters, and the current state.
/// </summary>
public static Type GetNextViewModelType(this SectionsNavigatorState sectionsNavigatorState)
{
if (sectionsNavigatorState.LastRequestState != NavigatorRequestState.Processing)
{
throw new InvalidOperationException("Can't get the next ViewModel on a processed request.");
}
var currentVM = sectionsNavigatorState.GetActiveStackNavigator()?.State.Stack.LastOrDefault()?.Request.ViewModelType;
var sectionsRequest = sectionsNavigatorState.LastRequest;
switch (sectionsRequest.RequestType)
{
case SectionsNavigatorRequestType.ReportSectionStateChanged:
return(GetNextFromReportSectionStateChanged());
case SectionsNavigatorRequestType.OpenModal:
return(GetNextFromOpenModal());
case SectionsNavigatorRequestType.CloseModal:
return(GetNextFromCloseModal());
case SectionsNavigatorRequestType.SetActiveSection:
return(GetNextFromSetActiveSection());
default:
throw new NotSupportedException($"The request type {sectionsRequest.RequestType} is not supported.");
}
Type GetNextFromReportSectionStateChanged()
{
if (sectionsNavigatorState.IsStackNavigatorFromSectionsRequestActive(out var stackNavigator))
{
// If the current request is on the active frame, we know that the request will change the next page.
var stackRequest = stackNavigator.State.LastRequest;
switch (stackRequest.RequestType)
{
case StackNavigatorRequestType.NavigateForward:
return(stackRequest.ViewModelType);
case StackNavigatorRequestType.NavigateBack:
return(stackNavigator.State.Stack[stackNavigator.State.Stack.Count - 2].Request.ViewModelType);
case StackNavigatorRequestType.Clear:
return(null);
case StackNavigatorRequestType.RemoveEntry:
// RemoveEntry is only used to remove previous pages (not the current page), so it doesn't change the current VM.
return(currentVM);
default:
throw new NotSupportedException($"The request type {stackRequest.RequestType} is not supported.");
}
}
else
{
// If the current request isn't on the active frame, then it's done in the background and doesn't affect the active page
return(currentVM);
}
}
Type GetNextFromOpenModal()
{
if (sectionsRequest.ModalPriority.HasValue)
{
// If the priority is specified, the new modal could be opened behind an existing one.
if ((sectionsNavigatorState.ActiveModal?.Priority ?? 0) >= sectionsRequest.ModalPriority.Value)
{
// If the priority of the new modal is above the active one's, the new modal will be the active one.
return(sectionsRequest.NewModalStackNavigationRequest.ViewModelType);
}
else
{
// If not, the new modal opens in background.
return(currentVM);
}
}
else
{
// If the priority isn't specified, the new modal will be the active one.
return(sectionsRequest.NewModalStackNavigationRequest.ViewModelType);
}
}
Type GetNextFromCloseModal()
{
var closingModal = sectionsNavigatorState.Modals.FirstOrDefault(m => m.Name == sectionsRequest.ModalName || m.Priority == sectionsRequest.ModalPriority) ?? sectionsNavigatorState.ActiveModal;
if (closingModal == sectionsNavigatorState.ActiveModal)
{
// If the active modal is closing, the next stack is either another modal or a section.
var modalUnderTheClosingOne = sectionsNavigatorState.Modals.FirstOrDefault(m => m.Priority < closingModal.Priority);
if (modalUnderTheClosingOne == null)
{
return(sectionsNavigatorState.ActiveSection.State.Stack.LastOrDefault()?.Request.ViewModelType);
}
else
{
return(modalUnderTheClosingOne.State.Stack.LastOrDefault()?.Request.ViewModelType);
}
}
else
{
// If not, the modal closes in background and the next ViewModel doesn't change.
return(currentVM);
}
}
Type GetNextFromSetActiveSection()
{
if (sectionsNavigatorState.Modals.Any())
{
// If there are modals, changing sections doesn't change the active VM.
return(currentVM);
}
else
{
if (sectionsNavigatorState.Sections.TryGetValue(sectionsRequest.SectionName, out var sectionNavigator))
{
// If there is a section associated to the request, return that section's current VM.
return(sectionNavigator.State.Stack.LastOrDefault()?.Request.ViewModelType);
}
else
{
// If not, the request will fail. We fallback to the current VM.
return(currentVM);
}
}
}
}
/// <summary>
/// Gets whether there is an active ViewModel in a <see cref="SectionsNavigatorState"/>.
/// </summary>
/// <param name="sectionsNavigatorState"></param>
/// <returns>True if there is an active ViewModel. False otherwise.</returns>
public static bool HasActiveViewModel(this SectionsNavigatorState sectionsNavigatorState)
{
return((sectionsNavigatorState.ActiveModal?.State.Stack.Any() ?? false) || (sectionsNavigatorState.ActiveSection?.State.Stack.Any() ?? false));
}
/// <summary>
/// Gets the ViewModel type of the last item of the active <see cref="IStackNavigator"/> of this <see cref="SectionsNavigatorState"/>.
/// </summary>
public static Type GetLastViewModelType(this SectionsNavigatorState state)
{
return(state.GetActiveStackNavigator()?.State.Stack.LastOrDefault()?.ViewModel.GetType());
}
/// <summary>
/// Gets the active <see cref="IStackNavigator"/> of this <see cref="SectionsNavigatorState"/>.
/// The result can be null is no navigator is active.
/// </summary>
public static IStackNavigator GetActiveStackNavigator(this SectionsNavigatorState sectionsNavigatorState)
{
return((IStackNavigator)sectionsNavigatorState.ActiveModal ?? sectionsNavigatorState.ActiveSection);
}
