public static Model.Expression ResolvePath(string path, string scope)
{
if (String.IsNullOrEmpty(path))
{
throw new ArgumentNullException("path");
}
Model.Expression result = null;
// Path may contain any number of member accessors and indexers
// e.g. code.coding[1]
while (true)
{
int firstIndex = path.IndexOfAny(new[] { '.', '[' });
if (firstIndex >= 0)
{
var memberName = path.Substring(0, firstIndex);
if (memberName != String.Empty)
{
result = BuildMemberAccessor(result, memberName, scope);
}
if (path[firstIndex] == '[')
{
var indexOfMatchingBracket = IndexOfMatchingBracket(path, firstIndex);
var indexPath = path.Substring(firstIndex + 1, indexOfMatchingBracket - (firstIndex + 1));
var indexExpression = ResolvePath(indexPath, scope);
// The use of .Get() here assumes the existence of appropriate list types with a Get method.
// This is a T-SQL specific solution to the representation of FHIR within SQL.
// Oracle would likely use a VARRAY, and PostgreSQL would use an array.
// Both those syntaxes would use an Indexer expression here, rather than a Get.
result = new Model.QualifierExpression(result, new Model.CallExpression("Get", new Model.Expression[] { indexExpression }));
if (indexOfMatchingBracket >= (path.Length - 1))
{
break;
}
path = path.Substring(indexOfMatchingBracket + 1);
}
else
{
path = path.Substring(firstIndex + 1);
}
}
else
{
result = BuildMemberAccessor(result, path, scope);
break;
}
}
return(result);
}
private static Model.Expression BuildMemberAccessor(Model.Expression current, string path, string scope)
{
if (path.IsDigit())
{
if (current != null)
{
throw new InvalidOperationException("Only index expressions can be integer literals.");
}
return(new Model.ValueExpression(Int32.Parse(path)));
}
else
{
if (current != null)
{
return(new Model.QualifierExpression(current, new SQLModel.QualifiedFieldExpression(path)));
}
else
{
return(new SQLModel.QualifiedFieldExpression(path, scope));
}
}
}
public static Model.Expression DemoteBooleanValuedExpression(Model.Expression expression)
{
// Although the traditional test for true is "<> 0", we use "= 1" here because A) we have control over how boolean are translated to integers,
// so we know they will always be represented as a 1 or 0, and the use of "=" rather than "<>" is more likely to be optimizable if it hits a sargable scenario. (we stay conjunctive).
return(new Model.BinaryExpression(expression, "iEqual", new Model.ValueExpression(1)));
}