public async Task Show(ScreenDefinition <TViewModel> screen, string parameter = null, ViewModelCreator <TViewModel> viewModelCreator = null)
{
var screenInstance = new ScreenInstance <TViewModel>(screen, parameter, viewModelCreator);
var result = _navigationGraph.FindBestStack(_navigationStack, screenInstance).ToList();
System.Diagnostics.Debug.WriteLine($"Navigating to {screen.RelativeRoute}");
System.Diagnostics.Debug.WriteLine($"\tUse stack: {string.Join(", ", result.Select(x => x.ToString()))}");
await UpdateNavigationStack(result);
}
public IList <ScreenInstance <TViewModel> > FindBestStack(List <ScreenInstance <TViewModel> > currentStack, ScreenInstance <TViewModel> screen)
{
if (!_nodePerScreenIds.TryGetValue(screen.Definition.Id, out var destinationNode))
{
throw new InvalidOperationException("This screen has not been registered");
}
var destinationScreen = new ScreenNode <TViewModel>(destinationNode, screen);
var currentScreenStack = currentStack.ConvertAll(x => new ScreenNode <TViewModel>(_nodePerScreenIds[x.Definition.Id], x));
// If nothing is on navigation stack,
// we need to find a path in the tree to get to the screen, a simple BFS will works, just need to take the multi entry points into account
// Else
// We need to find the shortest path to go from the current screen to the other
// correct way links must have priority (but if a down links is taken, only down links can taken after that)
// can only take up links that are in the navigation stack
return(FindPathToScreenWithBFS(currentScreenStack, destinationScreen).ConvertAll(x => x.ScreenInstance));
}
public IList <ScreenInstance <TViewModel> > FindWithRoute(string route)
{
if (string.IsNullOrWhiteSpace(route))
{
throw new InvalidOperationException("Route must not be empty or null");
}
//TODO: can set up a cache with found route in order to help the system
string[] routeParts = route.Split(new[] { '/' }, StringSplitOptions.RemoveEmptyEntries);
(List <ScreenInstance <TViewModel> > resultNodes, _, bool resultAmbiguity) = FindBest(_entryPoints, routeParts, 0);
if (resultAmbiguity)
{
throw new InvalidOperationException($"Ambiguous route {route}, specify parameter name if needed");
}
return(resultNodes);
(List <ScreenInstance <TViewModel> > nodes, int score, bool ambiguity) FindBest(List <Node <TViewModel> > nodes, string[] parts, int index)
{
(List <ScreenInstance <TViewModel> > nodes, int score)result = (null, 0);
bool ambiguity = false;
for (int i = 0; i < nodes.Count; i++)
{
(List <ScreenInstance <TViewModel> > nodes, int score, bool ambiguity)proposal = FindForRoute(nodes[i], parts, index);
if (proposal.nodes is null || result.score > proposal.score)
{
continue;
}
if (result.score == proposal.score && result.score > 0)
{
ambiguity = true;
continue;
}
ambiguity = proposal.ambiguity;
result = (proposal.nodes, proposal.score);
}
return(result.nodes, result.score, ambiguity);
}
(List <ScreenInstance <TViewModel> > nodes, int score, bool ambiguity) FindForRoute(Node <TViewModel> currentNode, string[] parts, int index)
{
(int currentNodeScore, string routeParameter) = RoutePartScore(currentNode, parts[index]);
if (currentNodeScore == 0)
{
return(null, 0, false);
}
var current = new ScreenInstance <TViewModel>(currentNode.Screen, routeParameter, null);
if (index + 1 == parts.Length)
{
return(new List <ScreenInstance <TViewModel> >
{
current
}, currentNodeScore, false);
}
(List <ScreenInstance <TViewModel> > nodes, int score, bool ambiguity)result = FindBest(currentNode.NextNodes, parts, index + 1);
result.nodes.Insert(0, current);
return(result);
}
(int score, string parameter) RoutePartScore(Node <TViewModel> node, string part)
{
if (node.Screen.IsParameterRoute)
{
if (part.StartsWith($"{node.Screen.ParameterName}:"))
{
// if parameter name match, the score is higher than general scoring
return(3, part.Substring(node.Screen.ParameterName.Length + 1));
}
// this is a parameterized route so it can match but with a lower score
return(1, part);
}
if (part == node.Screen.RelativeRoute)
{
return(4, null);
}
return(0, null);
}
}
protected bool Equals(ScreenInstance <TViewModel> other)
{
return(Equals(Definition.Id, other.Definition.Id) &&
string.Equals(Parameter, other.Parameter));
}