private static async Task LeaveCurrentNodeAsync(IBlockIterationState blockState, INavigationContext context)
{
if (blockState.CurrentNode is null)
{
return;
}
await blockState.CurrentNode.LeaveAsync(context);
}
private static INode?GetNextNode(IBlock block, IBlockIterationState blockState)
{
var nextIndex = blockState.CurrentNodeIndex.HasValue ? blockState.CurrentNodeIndex.Value + 1 : 0;
if (nextIndex >= block.Nodes.Count)
{
blockState.CurrentNodeIndex = null;
blockState.CurrentNode = null;
return(null);
}
var node = block.Nodes[nextIndex];
blockState.CurrentNodeIndex = nextIndex;
blockState.CurrentNode = node;
return(node);
}
private static INode?GetNextValidNode(IBlock block, INavigationContext context, IBlockIterationState blockState)
{
for (; ;)
{
var item = GetNextNode(block, blockState);
if (item == null)
{
return(null);
}
if (item.When == null || item.When.Evaluate(context.Variables))
{
if (item.ChildBlock is null || item.ChildBlock.While is null || item.ChildBlock.While.Evaluate(context.Variables))
{
return(item);
}
}
blockState.BackwardStack.Push(BlockedNode.Instance);
}
}
private static async Task <INode?> MoveNextAsync(IBlock block, INavigationContext context, IBlockIterationState blockState)
{
await LeaveCurrentNodeAsync(blockState, context);
var item = GetNextValidNode(block, context, blockState);
if (item is null)
{
return(null);
}
var reverseState = await item.EnterAsync(context);
blockState.BackwardStack.Push(reverseState);
return(item);
}
private static async Task <INode?> MovePreviousAsync(IBlock block, INavigationContext context, IBlockIterationState blockState)
{
await LeaveCurrentNodeAsync(blockState, context);
var index = blockState.CurrentNodeIndex ?? (block.Nodes.Count - 1);
for (; ;)
{
if (!blockState.BackwardStack.TryPop(out var state))
{
blockState.CurrentNodeIndex = null;
blockState.CurrentNode = null;
return(null);
}
if (state is not BlockedNode)
{
var node = block.Nodes[index];
blockState.CurrentNodeIndex = blockState.CurrentNodeIndex = index > 0 ? index - 1: null;
blockState.CurrentNode = node;
await node.EnterAsync(context, state);
return(node);
}
index--;
}
}
