using System;
using System.IO;
using System.Text;
using System.Xml;
using Sprache;
using XNeedle.Parser;
using XNeedle.Parser.Elements;

namespace XNeedle.Transformation
{
    public class ContextFunctions
    {
        public static string hex(Context ctx, double value)
        {
            uint v = (uint)value;
            return $"#x{v:X8}";
        }

        public static int GetLevel(XmlNode node)
        {
            int level = 0;
            XmlNode? currentNode = node;
            while (null != (currentNode = currentNode.ParentNode))
                level++;

            return level;
        }
        public static double crc(Context ctx)
        {
            if (ctx.Node is null)
            {
                return 0;
            }
            int crc = 0xAFFE;

            XmlWriterSettings settings = new XmlWriterSettings();
            settings.Indent = true;
            settings.ConformanceLevel = ConformanceLevel.Document;
            settings.OmitXmlDeclaration = true;

            // This isn't performant, but the whole document has to be rendered
            // for an accurate data stream
            string docrender = "";
            string fragrender = "";
            using (var sw = new StringWriter())
            {
                using (var xw = XmlWriter.Create(sw, settings))
                {
                    if (ctx.Node.OwnerDocument is not null)
                    {
                        ctx.Node.OwnerDocument.WriteContentTo(xw);
                    }
                }
                docrender = sw.ToString();
            }

            settings.Indent = false;
            settings.ConformanceLevel = ConformanceLevel.Fragment;
            using (var sw = new StringWriter())
            {
                using (var xw = XmlWriter.Create(sw, settings))
                {
                    ctx.Node.WriteTo(xw);
                }
                fragrender = sw.ToString();
            }
            string tagname = ctx.Node.Name;
            string anchor = XmlFragParser.OpeningTagAnchor(tagname).Parse(fragrender);
            string preamble = $"<{tagname}{anchor}>";

            //string data = FragXmlParser.ChecksumData(preamble, tagname).TryParse(docrender);

            Console.WriteLine("preamble: " + preamble);

            var crc32 = new System.IO.Hashing.Crc32();
            var bytes = Encoding.UTF8.GetBytes("");
            crc32.Append(bytes);
            crc = BitConverter.ToInt32(crc32.GetCurrentHash());

            return (double)crc;
        }

        public static string text(Context ctx)
        {
            if (ctx.Node is null) return "";
            return ctx.Node.InnerText;
        }

        public static string text(Context ctx, string txt)
        {
            if (ctx.Node is null) return "";
            return ctx.Node.InnerText = txt;
        }

        public static string attr(Context ctx, string name, string value)
        {
            if (ctx.Node is null || ctx.Node.Attributes is null) return "";
            var attr = ctx.Node.Attributes[name];
            if (attr != null)
            {
                attr.Value = value;
            }
            else
            {
                if (ctx.Node.OwnerDocument is null) return "";
                var add = ctx.Node.OwnerDocument.CreateAttribute(name);
                add.Value = value;
                ctx.Node.Attributes.SetNamedItem(add);
            }
            return "";
        }

        public static string attr(Context ctx, string name)
        {
            if (ctx.Node?.Attributes?[name]?.Value is string val)
            {
                return val;
            }
            return "";
        }
    }
}