using System;
using System.Collections.Generic;
using System.IO;

namespace mutil {

public class Configuration {
    private Dictionary<string,string> configs = new Dictionary<string,string>();
    private string filename;
    private Configuration(string filename) {
        this.filename = filename;
        if (File.Exists(filename)) {
            XmlExtractor xmle = new XmlExtractor();
            xmle.openInput(filename);
            xmle.requireChild("configuration");
            string elem;
            string value;
            Dictionary<string,string> attrs;

            int ctl = xmle.extractElement(XmlExtractor.EC_BEG, out elem, out value, out attrs);
            while (ctl != XmlExtractor.EC_END) {
                if (elem != "entry") throw new ApplicationException("entry tag expected.");
                configs.Add(attrs["key"], value);
                ctl = xmle.extractElement(ctl, out elem, out value, out attrs);
            }
        }
    }
    static private Configuration theInstance = null;
    static public Configuration getInstance(string filename) {
        if (theInstance == null) theInstance = new Configuration(filename);
        return theInstance;
    }
    static public Configuration getInstance() {
        if (theInstance == null) throw new System.Exception("parameter filename missing.");
        return theInstance;
    }
    
    public void Add(string key, string value) {
    	string dummy;
    	if (this.configs.TryGetValue(key, out dummy)) this.configs[key] = value;
    	else this.configs.Add(key, value);
    }
    
    public string Require(string key) {
    	return this.configs[key];
    }

    public string Get(string key) {
    	string value;
    	this.configs.TryGetValue(key, out value);
    	return value;
    }

    public string Get(string key, string defaut) {
    	string value;
    	if (! this.configs.TryGetValue(key, out value)) return defaut;
    	return value;
    }

    ~Configuration() {
        StreamWriter outfile;
        using ( outfile = new StreamWriter (this.filename)) {
            outfile.WriteLine("<configuration>");
            foreach(var config in this.configs) {
                outfile.WriteLine("<entry key=\"{0}\">{1}</entry>", config.Key, config.Value);
            }
            outfile.WriteLine("</configuration>");
        }    
    }
}

}