using System;
using System.Collections.Generic;
using System.Text;
using System.Xml;

namespace xCommons.Helpers {
    public partial class XMLToJSONHelper {
        //
        #region Actions ...
        public static string ToJSON (string xml) {
            //
            XmlDocument doc = new XmlDocument ();
            doc.LoadXml (xml);

            //
            return XmlToJSON (doc);
        }

        public static string XmlToJSON (XmlDocument xmlDoc) {
            //
            StringBuilder sbJSON = new StringBuilder ();

            //
            sbJSON.Append ("{ ");
            XmlToJSONnode (sbJSON, xmlDoc.DocumentElement, true);
            sbJSON.Append ("}");

            //
            return sbJSON.ToString ();
        }
        #endregion

        //
        #region Private ...
        //
        private static void XmlToJSONnode (StringBuilder sbJSON, XmlElement node, bool showNodeName) {
            //
            if (showNodeName) {
                sbJSON.Append ("\"" + SafeJSON (node.Name) + "\": ");
            }

            //
            sbJSON.Append ("{");

            //
            // Build a sorted list of key-value pairs
            //  where   key is case-sensitive nodeName
            //          value is an ArrayList of string or XmlElement
            //  so that we know whether the nodeName is an array or not.
            SortedList<string, object> childNodeNames = new SortedList<string, object> ();

            //
            //  Add in all node attributes
            if (node.Attributes != null)
                foreach (XmlAttribute attr in node.Attributes)
                    StoreChildNode (childNodeNames, attr.Name, attr.InnerText);

            //
            //  Add in all nodes
            foreach (XmlNode cnode in node.ChildNodes) {
                //
                if (cnode is XmlText) {
                    StoreChildNode (childNodeNames, "value", cnode.InnerText);
                } else if (cnode is XmlElement) {
                    StoreChildNode (childNodeNames, cnode.Name, cnode);
                }
            }

            //
            // Now output all stored info
            foreach (string childname in childNodeNames.Keys) {
                //
                List<object> alChild = (List<object>) childNodeNames[childname];
                if (alChild.Count == 1) {
                    OutputNode (childname, alChild[0], sbJSON, true);
                } else {
                    //
                    sbJSON.Append (" \"" + SafeJSON (childname) + "\": [ ");

                    //
                    foreach (object Child in alChild) {
                        OutputNode (childname, Child, sbJSON, false);
                    }

                    //
                    sbJSON.Remove (sbJSON.Length - 2, 2);
                    sbJSON.Append (" ], ");
                }
            }

            //
            sbJSON.Remove (sbJSON.Length - 2, 2);
            sbJSON.Append (" }");
        }

        //
        //  StoreChildNode: Store data associated with each nodeName
        //                  so that we know whether the nodeName is an array or not.
        private static void StoreChildNode (SortedList<string, object> childNodeNames, string nodeName, object nodeValue) {
            //
            // Pre-process contraction of XmlElement-s
            if (nodeValue is XmlElement) {
                //
                // Convert  <aa></aa> into "aa":null
                //          <aa>xx</aa> into "aa":"xx"
                XmlNode cnode = (XmlNode) nodeValue;
                if (cnode.Attributes.Count == 0) {
                    //
                    XmlNodeList children = cnode.ChildNodes;
                    if (children.Count == 0) {
                        nodeValue = null;
                    } else if (children.Count == 1 && (children[0] is XmlText)) {
                        nodeValue = ((XmlText) (children[0])).InnerText;
                    }
                }
            }

            //
            // Add nodeValue to ArrayList associated with each nodeName
            // If nodeName doesn't exist then add it
            List<object> ValuesAL;

            //
            if (childNodeNames.ContainsKey (nodeName)) {
                ValuesAL = (List<object>) childNodeNames[nodeName];
            } else {
                //
                ValuesAL = new List<object> ();
                childNodeNames[nodeName] = ValuesAL;
            }

            //
            ValuesAL.Add (nodeValue);
        }

        //
        private static void OutputNode (string childname, object alChild, StringBuilder sbJSON, bool showNodeName) {
            if (alChild == null) {
                if (showNodeName)
                    sbJSON.Append ("\"" + SafeJSON (childname) + "\": ");
                sbJSON.Append ("null");
            } else if (alChild is string) {
                if (showNodeName)
                    sbJSON.Append ("\"" + SafeJSON (childname) + "\": ");
                string sChild = (string) alChild;
                sChild = sChild.Trim ();
                sbJSON.Append ("\"" + SafeJSON (sChild) + "\"");
            } else
                XmlToJSONnode (sbJSON, (XmlElement) alChild, showNodeName);
            sbJSON.Append (", ");
        }

        //
        // Make a string safe for JSON
        private static string SafeJSON (string sIn) {
            //
            StringBuilder sbOut = new StringBuilder (sIn.Length);
            foreach (char ch in sIn) {
                //
                if (Char.IsControl (ch) || ch == '\'') {
                    //
                    int ich = (int) ch;
                    sbOut.Append (@"\u" + ich.ToString ("x4"));
                    continue;
                } else if (ch == '\"' || ch == '\\' || ch == '/') {
                    sbOut.Append ('\\');
                }

                //
                sbOut.Append (ch);
            }

            //
            return sbOut.ToString ();
        }
        #endregion        
    }
}