private static void ThrowExpectedEdgeButFoundRecursive(MatchPath patternMatchElement, PatternMatchElementExpression elementExpression)
{
throw new InvalidQueryException($"Invalid pattern match syntax: expected element '{patternMatchElement}' to be of type edge, but it is a recursive clause. In a graph query, recursive clause is considered an edge, and should be preceded by a vertex and superseded by edge. (The full expression: '{elementExpression}')");
}
public override void VisitPatternMatchElementExpression(PatternMatchElementExpression elementExpression)
{
var elements = elementExpression.Path;
if (elements.Length == 1)
{
if (elements[0].IsEdge)
{
ThrowExpectedVertexButFoundEdge(elements[0], elementExpression);
}
}
else
{
ThrowIfDuplicateAlias(elements[0]);
if (elements[0].IsEdge && !elements[0].Recursive.HasValue)
{
ThrowExpectedVertexButFoundEdge(elements[0], elementExpression);
}
if (elements[elements.Length - 1].IsEdge && !elements[elements.Length - 1].Recursive.HasValue)
{
ThrowExpectedVertexButFoundEdge(elements[elements.Length - 1], elementExpression);
}
var last = QueryStepElementType.Vertex; //we just verified that the first (or last) is a vertex
for (var i = 1; i < elements.Length; i++)
{
QueryStepElementType next;
var nextIsRecursive = false;
if (elements[i].Recursive.HasValue)
{
var matchPath = elements[i].Recursive.Value.Pattern;
foreach (var path in matchPath)
{
ThrowIfDuplicateAlias(path);
}
next = DetermineEdgeOrVertex(matchPath[0]);
nextIsRecursive = true;
}
else
{
ThrowIfDuplicateAlias(elements[i]);
next = DetermineEdgeOrVertex(elements[i]);
}
switch (last)
{
case QueryStepElementType.Vertex when next != QueryStepElementType.Edge:
if (nextIsRecursive)
{
ThrowExpectedEdgeButFoundRecursive(elements[i], elementExpression);
}
ThrowExpectedEdgeButFoundVertex(elements[i], elementExpression);
break;
case QueryStepElementType.Edge when next != QueryStepElementType.Vertex:
if (nextIsRecursive)
{
ThrowExpectedVertexButFoundRecursive(elements[i], elementExpression);
}
ThrowExpectedVertexButFoundEdge(elements[i], elementExpression);
break;
}
if (elements[i].Recursive.HasValue)
{
var matchPath = elements[i].Recursive.Value.Pattern;
last = DetermineEdgeOrVertex(matchPath[matchPath.Count - 1]);
}
else
{
last = next;
}
}
}
}
private static void ThrowExpectedEdgeButFoundVertex(MatchPath patternMatchElement, PatternMatchElementExpression elementExpression)
{
throw new InvalidQueryException($"Invalid pattern match syntax: expected element '{patternMatchElement}' to be of type edge, but it is an vertex. (The full expression: '{elementExpression}')");
}