public void AddPolicyEdge(object state, DfaNode node)
{
if (PolicyEdges == null)
{
PolicyEdges = new Dictionary <object, DfaNode>();
}
PolicyEdges.Add(state, node);
}
public void AddLiteral(string literal, DfaNode node)
{
if (Literals == null)
{
Literals = new Dictionary <string, DfaNode>(StringComparer.OrdinalIgnoreCase);
}
Literals.Add(literal, node);
}
public DfaNode BuildDfaTree()
{
// We build the tree by doing a BFS over the list of entries. This is important
// because a 'parameter' node can also traverse the same paths that literal nodes
// traverse. This means that we need to order the entries first, or else we will
// miss possible edges in the DFA.
_endpoints.Sort(_comparer);
// Since we're doing a BFS we will process each 'level' of the tree in stages
// this list will hold the set of items we need to process at the current
// stage.
var work = new List <(MatcherEndpoint endpoint, List <DfaNode> parents)>();
var root = new DfaNode()
{
Depth = 0, Label = "/"
};
// To prepare for this we need to compute the max depth, as well as
// a seed list of items to process (entry, root).
var maxDepth = 0;
for (var i = 0; i < _endpoints.Count; i++)
{
var endpoint = _endpoints[i];
maxDepth = Math.Max(maxDepth, endpoint.RoutePattern.PathSegments.Count);
work.Add((endpoint, new List <DfaNode>()
{
root,
}));
}
// Now we process the entries a level at a time.
for (var depth = 0; depth <= maxDepth; depth++)
{
// As we process items, collect the next set of items.
var nextWork = new List <(MatcherEndpoint endpoint, List <DfaNode> parents)>();
for (var i = 0; i < work.Count; i++)
{
var(endpoint, parents) = work[i];
if (!HasAdditionalRequiredSegments(endpoint, depth))
{
for (var j = 0; j < parents.Count; j++)
{
var parent = parents[j];
parent.Matches.Add(endpoint);
}
}
// Find the parents of this edge at the current depth
var nextParents = new List <DfaNode>();
var segment = GetCurrentSegment(endpoint, depth);
if (segment == null)
{
continue;
}
for (var j = 0; j < parents.Count; j++)
{
var parent = parents[j];
var part = segment.Parts[0];
if (segment.IsSimple && part is RoutePatternLiteralPart literalPart)
{
var literal = literalPart.Content;
if (!parent.Literals.TryGetValue(literal, out var next))
{
next = new DfaNode()
{
Depth = parent.Depth + 1,
Label = parent.Label + literal + "/",
};
parent.Literals.Add(literal, next);
}
nextParents.Add(next);
}
else if (segment.IsSimple && part is RoutePatternParameterPart parameterPart && parameterPart.IsCatchAll)
{
// A catch all should traverse all literal nodes as well as parameter nodes
// we don't need to create the parameter node here because of ordering
// all catchalls will be processed after all parameters.
nextParents.AddRange(parent.Literals.Values);
if (parent.Parameters != null)
{
nextParents.Add(parent.Parameters);
}
// We also create a 'catchall' here. We don't do further traversals
// on the catchall node because only catchalls can end up here. The
// catchall node allows us to capture an unlimited amount of segments
// and also to match a zero-length segment, which a parameter node
// doesn't allow.
if (parent.CatchAll == null)
{
parent.CatchAll = new DfaNode()
{
Depth = parent.Depth + 1,
Label = parent.Label + "{*...}/",
};
// The catchall node just loops.
parent.CatchAll.Parameters = parent.CatchAll;
parent.CatchAll.CatchAll = parent.CatchAll;
}
parent.CatchAll.Matches.Add(endpoint);
}