using Microsoft.AspNetCore.Http;
using System.Text;
using System.Web;
using ZelWiki.Library.Interfaces;

namespace ZelWiki.Library
{
    public static class QueryStringConverter
    {
        /// <summary>
        /// Takes the current page query string and upserts the given order-by field,
        /// if the string already sorts on the given field then the order is inverted (asc/desc).
        /// </summary>
        /// <returns></returns>
        public static string OrderHelper(ISessionState context, string value)
        {
            string orderByKey = "OrderBy";
            string orderByDirectionKey = "OrderByDirection";
            string? currentDirection = "asc";
            var collection = ToDictionary(context.QueryString);

            //Check to see if we are sorting on the value that we are already sorted on, this would mean we need to invert the sort.
            if (collection.TryGetValue(orderByKey, out var currentValue))
            {
                bool invertDirection = string.Equals(currentValue, value, StringComparison.InvariantCultureIgnoreCase);

                if (invertDirection)
                {
                    if (collection.TryGetValue(orderByDirectionKey, out currentDirection))
                    {
                        if (currentDirection == "asc")
                        {
                            currentDirection = "desc";
                        }
                        else
                        {
                            currentDirection = "asc";
                        }
                    }
                }
                else
                {
                    currentDirection = "asc";
                }
            }

            collection.Remove(orderByKey);
            collection.Add(orderByKey, value);

            collection.Remove(orderByDirectionKey);
            collection.Add(orderByDirectionKey, currentDirection ?? "asc");

            return FromCollection(collection);
        }

        /// <summary>
        /// Takes the current page query string and upserts a query key/value, replacing any conflicting query string entry.
        /// </summary>
        /// <param name="queryString"></param>
        /// <param name="name"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static string Upsert(IQueryCollection? queryString, string name, string value)
        {
            var collection = ToDictionary(queryString);
            collection.Remove(name);
            collection.Add(name, value);
            return FromCollection(collection);
        }

        public static Dictionary<string, string> ToDictionary(IQueryCollection? queryString)
        {
            if (queryString == null)
            {
                return new Dictionary<string, string>();
            }

            var dictionary = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

            foreach (var item in queryString)
            {
                //Technically, keys can be duplicated in a IQueryCollection but we do not
                //support this. Use .Single() to throw exception if duplicates are found.
                dictionary.Add(item.Key, item.Value.Single() ?? string.Empty);
            }

            return dictionary;
        }

        public static Dictionary<string, string> ToDictionary(QueryString? queryString)
            => ToDictionary(queryString?.ToString());

        public static Dictionary<string, string> ToDictionary(string? queryString)
        {
            var dictionary = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
            if (string.IsNullOrEmpty(queryString))
            {
                return dictionary;
            }

            // If the query string starts with '?', remove it
            if (queryString.StartsWith('?'))
            {
                queryString = queryString.Substring(1);
            }

            // Split the query string into key-value pairs
            var keyValuePairs = queryString.Split('&');

            foreach (var kvp in keyValuePairs)
            {
                var keyValue = kvp.Split('=');
                if (keyValue.Length == 2)
                {
                    var key = HttpUtility.UrlDecode(keyValue[0]);
                    var value = HttpUtility.UrlDecode(keyValue[1]);
                    dictionary[key] = value;
                }
            }

            return dictionary;
        }

        public static string FromCollection(IQueryCollection? collection)
        {
            if (collection == null || collection.Count == 0)
            {
                return string.Empty;
            }

            var queryString = new StringBuilder();

            foreach (var kvp in collection)
            {
                if (queryString.Length > 0)
                {
                    queryString.Append('&');
                }

                queryString.Append($"{Uri.EscapeDataString(kvp.Key)}={Uri.EscapeDataString(kvp.Value.ToString())}");
            }

            return queryString.ToString();
        }

        public static string FromCollection(Dictionary<string, string>? collection)
        {
            if (collection == null || collection.Count == 0)
            {
                return string.Empty;
            }

            var queryString = new StringBuilder();

            foreach (var kvp in collection)
            {
                if (queryString.Length > 0)
                {
                    queryString.Append('&');
                }
                queryString.Append($"{Uri.EscapeDataString(kvp.Key)}={Uri.EscapeDataString(kvp.Value)}");
            }

            return queryString.ToString();
        }

        public static Dictionary<string, string> Clone(Dictionary<string, string>? original)
        {
            if (original == null)
            {
                return new Dictionary<string, string>();
            }

            var clone = new Dictionary<string, string>(original.Count, original.Comparer);
            foreach (var kvp in original)
            {
                clone.Add(kvp.Key, kvp.Value);
            }
            return clone;
        }
    }
}