private static bool IsSegmentValid(Context context, List <RoutePatternPart> parts)
{
// If a segment has multiple parts, then it can't contain a catch all.
for (var i = 0; i < parts.Count; i++)
{
var part = parts[i];
if (part is RoutePatternParameterPart parameter && parameter.IsCatchAll && parts.Count > 1)
{
context.Error = Resources.TemplateRoute_CannotHaveCatchAllInMultiSegment;
return(false);
}
}
// if a segment has multiple parts, then only the last one parameter can be optional
// if it is following a optional seperator.
for (var i = 0; i < parts.Count; i++)
{
var part = parts[i];
if (part is RoutePatternParameterPart parameter && parameter.IsOptional && parts.Count > 1)
{
// This optional parameter is the last part in the segment
if (i == parts.Count - 1)
{
var previousPart = parts[i - 1];
if (!previousPart.IsLiteral && !previousPart.IsSeparator)
{
// The optional parameter is preceded by something that is not a literal or separator
// Example of error message:
// "In the segment '{RouteValue}{param?}', the optional parameter 'param' is preceded
// by an invalid segment '{RouteValue}'. Only a period (.) can precede an optional parameter.
context.Error = Resources.FormatTemplateRoute_OptionalParameterCanbBePrecededByPeriod(
RoutePatternPathSegment.DebuggerToString(parts),
parameter.Name,
parts[i - 1].DebuggerToString());
return(false);
}
else if (previousPart is RoutePatternLiteralPart literal && literal.Content != PeriodString)
{
// The optional parameter is preceded by a literal other than period.
// Example of error message:
// "In the segment '{RouteValue}-{param?}', the optional parameter 'param' is preceded
// by an invalid segment '-'. Only a period (.) can precede an optional parameter.
context.Error = Resources.FormatTemplateRoute_OptionalParameterCanbBePrecededByPeriod(
RoutePatternPathSegment.DebuggerToString(parts),
parameter.Name,
parts[i - 1].DebuggerToString());
return(false);
}
parts[i - 1] = RoutePatternFactory.SeparatorPart(((RoutePatternLiteralPart)previousPart).Content);
}
else
{
// This optional parameter is not the last one in the segment
// Example:
// An optional parameter must be at the end of the segment. In the segment '{RouteValue?})',
// optional parameter 'RouteValue' is followed by ')'
context.Error = Resources.FormatTemplateRoute_OptionalParameterHasTobeTheLast(
RoutePatternPathSegment.DebuggerToString(parts),
parameter.Name,
parts[i + 1].DebuggerToString());
return(false);
}
}
}
// A segment cannot contain two consecutive parameters
var isLastSegmentParameter = false;
for (var i = 0; i < parts.Count; i++)
{
var part = parts[i];
if (part.IsParameter && isLastSegmentParameter)
{
context.Error = Resources.TemplateRoute_CannotHaveConsecutiveParameters;
return(false);
}
isLastSegmentParameter = part.IsParameter;
}
return(true);
}