using System;
using System.Collections.Generic;
using System.Text;
using System.Collections.Specialized;
using System.Collections;
using System.Web;



namespace BusinessLayer
{
    public class QueryString : NameValueCollection
    {
        private string document;
        public string Document
        {
            get
            {
                return document;
            }
        }
        public QueryString()
        {
        }
        public QueryString(NameValueCollection clone)
            : base(clone)
        {

        }

        //this method has been used to get the current URL of the page 
        public static QueryString FromCurrent()
        {
            //returns the current url from the address bar
            return FromUrl (HttpContext.Current.Request.Url.AbsoluteUri) ;
        }

        /// <summary>
        /// This method has been used to divide the Address URl into characters chunks 
        /// </summary>
        /// <param name="url"></param>
        /// <returns></returns>
        public static QueryString FromUrl(string url)
        {
            //it breaks the address URL in array with separator of ? mark
            //this line breaks the Querystring and page 
            string[] parts = url.Split("?".ToCharArray());
            //instantiate the class object
            QueryString qs = new QueryString();
            //assign the page address to the variable
            qs.document = parts[0];
            //if there is any data in array
            if (parts.Length == 1)
                return qs;
            //breaks the QueryString into characters chunks with separator mark &
            string[] keys = parts[1].Split("&".ToCharArray());
            foreach (string key in keys)
            {
                //again breaks into chunks by + mark
                string[] part = key.Split("=".ToCharArray());
                if (part.Length == 1)
                    qs.Add(part[0], "");
                //adds the QueryString key and value pair to the assigned variable
                qs.Add(part[0], part[1]);
            }
            return qs;


        }
        /// <summary>
        /// This method clear all exceptions in the passed string
        /// </summary>
        /// <param name="except"></param>
        public void ClearAllExcept(string except)
        {
            //calls the method to clear except 
            ClearAllExcept(new string[] { except });

        }
        /// <summary>
        /// this is the usual method which has to call clear all exceptions
        /// </summary>
        /// <param name="except"></param>
        public void ClearAllExcept(string[] except)
        {
            //take an arrayList 
            ArrayList toRemove = new ArrayList();
            foreach (string s in this.AllKeys)
            {
                foreach (string e in except)
                {
                    if (s.ToLower() == e.ToLower())
                        if (!toRemove.Contains(s))
                            toRemove.Add(s);

                }
            }
            foreach (string s in toRemove)
                this.Remove(s);
        }
        /// <summary>
        /// this method adds the key value pairs in QueryString of the URL
        /// </summary>
        /// <param name="name"></param>
        /// <param name="value"></param>
        public override void Add(string name, string value)
        {
            //checks nullability of the name 
            if (this[name] != null)
                //if not null then assign value to it
                this[name] = value;

            else

                base.Add(name, value);

        }



        public override string ToString()
        {

            return ToString(false);

        }


        /// <summary>
        /// this ethod has been used to join all the characters array to the URL 
        /// </summary>
        /// <param name="includeUrl"></param>
        /// <returns></returns>
        public string ToString(bool includeUrl)
        {

            string[] parts = new string[this.Count];

            string[] keys = this.AllKeys;
            //for each keys breaks the URL into chunks
            for (int i = 0; i < keys.Length; i++)

                parts[i] = keys[i] + "=" + HttpContext.Current.Server.UrlEncode(this[keys[i]]);

            string url = String.Join("&", parts);

            if ((url != null || url != String.Empty) && !url.StartsWith("?"))

                url = "?" + url;

            if (includeUrl)

                url = this.document + url;

            return url;

        }

    }
}