SelectXml.cs

using System.Collections.Generic;
using System.Threading.Tasks;
using System.Xml;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Xml.Functions
{
    public class SelectXml : FunctionTwoScalarVariables
    {
        public SelectXml(ScriptNode Xml, ScriptNode Name, int Start, int Length, Expression Expression)
            : base(Xml, Name, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(SelectXml);
 
        public override string[] DefaultArgumentNames => new string[] { "XML", "XPath" };
 
        public override IElement EvaluateScalar(IElement Argument1, IElement Argument2, Variables Variables)
        {
            object Obj = Argument1.AssociatedObjectValue;
            XmlNodeList Result;
 
            if (Obj is null)
                return ObjectValue.Null;
            else if (Obj is XmlNode N)
                Result = Evaluate(N, Argument2.AssociatedObjectValue?.ToString() ?? string.Empty);
            else
                throw new ScriptRuntimeException("XPath expression only operate on XML.", this);
 
            int i, c = Result.Count;
 
            switch (c)
            {
                case 0:
                    return ObjectValue.Null;
 
                case 1:
                    return ToElement(Result[0]);
 
                default:
                    IElement[] Items = new IElement[c];
 
                    for (i = 0; i < c; i++)
                        Items[i] = ToElement(Result[i]);
 
                    return Operators.Vectors.VectorDefinition.Encapsulate(Items, false, this);
            }
        }
 
        public override Task<IElement> EvaluateScalarAsync(IElement Argument1, IElement Argument2, Variables Variables)
        {
            return Task.FromResult(this.EvaluateScalar(Argument1, Argument2, Variables));
        }
 
        internal static XmlNodeList Evaluate(XmlNode N, string XPath)
        {
            XmlNamespaceManager NamespaceManager;
            XmlNodeList Result;
            XmlElement Root;
 
            if (N is XmlDocument Doc)
            {
                NamespaceManager = new XmlNamespaceManager(Doc.NameTable);
                Root = Doc.DocumentElement;
            }
            else if (N is XmlElement E && !(N.OwnerDocument is null))
            {
                NamespaceManager = new XmlNamespaceManager(N.OwnerDocument.NameTable);
                Root = E;
            }
            else
            {
                NamespaceManager = null;
                Root = null;
            }
 
            if (NamespaceManager is null)
                Result = N.SelectNodes(XPath);
            else
            {
                if (XPath.Contains("default:"))
                {
                    string Namespace = null;
 
                    if (string.IsNullOrEmpty(Root.Prefix) && !string.IsNullOrEmpty(Root.NamespaceURI))
                        Namespace = Root.NamespaceURI;
                    else
                    {
                        LinkedList<XmlElement> ToProcess = new LinkedList<XmlElement>();
 
                        foreach (XmlNode N2 in Root.ChildNodes)
                        {
                            if (N2 is XmlElement E)
                                ToProcess.AddLast(E);
                        }
 
                        while (!(ToProcess.First is null))
                        {
                            Root = ToProcess.First.Value;
                            ToProcess.RemoveFirst();
 
                            if (string.IsNullOrEmpty(Root.Prefix) && !string.IsNullOrEmpty(Root.NamespaceURI))
                            {
                                Namespace = Root.NamespaceURI;
                                break;
                            }
 
                            foreach (XmlNode N2 in Root.ChildNodes)
                            {
                                if (N2 is XmlElement E)
                                    ToProcess.AddLast(E);
                            }
                        }
                    }
 
                    if (!string.IsNullOrEmpty(Namespace) && !NamespaceManager.HasNamespace(Namespace))
                        NamespaceManager.AddNamespace("default", Namespace);
                }
 
                Result = N.SelectNodes(XPath, NamespaceManager);
            }
 
            return Result;
        }
 
        public static IElement ToElement(XmlNode Node)
        {
            if (Node is XmlText Text)
                return ToElement(Text.Value);
            else if (Node is XmlCDataSection CData)
                return ToElement(CData.Value);
            else if (Node is XmlAttribute Attr)
                return ToElement(Attr.Value);
            else
            {
                if (Node.HasChildNodes && Node.FirstChild == Node.LastChild && Node.FirstChild is XmlText Text2)
                    return ToElement(Text2.Value);
                else
                    return new ObjectValue(Node);
            }
        }
 
        private static IElement ToElement(string s)
        {
            if (Expression.TryParse(s, out double d))
                return new DoubleNumber(d);
            else
                return new StringValue(s);
        }
 
    }
}