xn/Transformation/Rule.cs

using System.Collections.Generic;
using System.Xml;
using System.Xml.Linq;
using System.Xml.XPath;
using XNeedle;
using XNeedle.Parser.Elements;

namespace XNeedle.Transformation
{
    public class Rule : Part
    {
        public required string XPathSelector { get; set; }
        public required IEnumerable<Part> Body;

        public void Transform(XDocument xml, SourceLocation sloc)
        {
            var context = new Context();
            context.Node = xml.Root;
            context.SLoc = sloc;
            Operate(context);
        }

        public override void Operate(Context ctx)
        {
            var nodes = ctx.Node?.XPathSelectElements(XPathSelector);
            if(nodes is null || nodes.Count() == 0)
            {
                var nullCtx = ctx.Clone();
                nullCtx.Node = null;
                nullCtx.SLoc = ctx.SLoc.WithLineNumber(-1);
                foreach (var b in Body)
                {
                    b.Operate(nullCtx);
                }
                return;
            }
  
            foreach (XElement n in nodes)
            {
                var loopCtx = ctx.Clone();
                loopCtx.Node = n;
                var lineInfo = (IXmlLineInfo)n;
                loopCtx.SLoc = ctx.SLoc.WithLineNumber(lineInfo.HasLineInfo() ? lineInfo.LineNumber : -1);
                foreach (var b in Body)
                {
                    b.Operate(loopCtx);
                }
            }
        }
    }
}