using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using System.Reflection;
using System.IO;
using System.Xml;
using System.Xml.Linq;

namespace DataDrivenExample
{
    class Constants
    {

        // Public properties -- constants available for use
        //  throughout the program

        public Vector2 Gravity { get; private  set; }
        public float Pi { get; private set; }
        public bool DebugTriggerArea { get; private set; }
        public int ScreenWidth { get; private set; }
        public int ScreenHeight { get; private set; }


        public static Constants GetInstance()
        {
            if (mInstance == null)
            {
                mInstance = new Constants();
                mInstance.LoadConstants("Content/Constants.xml");
            }
            return mInstance;
        }


        // Private methods and data fields, for implementing the static class
        // and reading the constants in from an XML file

        private static Constants mInstance;
        private Constants()
        {
            // Set default values for the constants declared in this class
            // These values can be overriden by the XML file
            Gravity = new Vector2(0, 9.8f);
            Pi = 3.14159f;
        }

        protected void AddConstant(XElement elem)
        {
            XMLParse.AddValueToClassInstance(elem, Constants.GetInstance());
        }

        private void LoadConstants(String constantFile)
        {
            using (XmlReader reader = XmlReader.Create(new StreamReader(constantFile)))
            {
                XDocument xml = XDocument.Load(reader);
                XElement root = xml.Root;
                foreach (XElement elem in root.Elements())
                {
                    AddConstant(elem);
                }
            }
        }
    }
}