using System;
using System.Collections.Generic;
using System.Globalization;
using System.Web.Helpers;
using System.Web.Mvc;
using System.Web.WebPages;

namespace LeafWeb.WebCms.Utility
{
    public static class WebGridExtensions
    {
        public static HelperResult PagerList(
            this WebGrid webGrid,
            WebGridPagerModes mode = WebGridPagerModes.NextPrevious | WebGridPagerModes.Numeric,
            string firstText = "First",
            string previousText = "Prev",
            string nextText = "Next",
            string lastText = "Last",
            int numericLinksCount = 5,
            string paginationStyle = null)
        {
            return PagerList(webGrid, mode, firstText, previousText, nextText, lastText, numericLinksCount,
                paginationStyle, true);
        }

        /* bootstrap pagination classes */
        private const string ulClass = "pagination";
        private const string liClass = "page-item";
        private const string aClass = "page-link";

        private static HelperResult PagerList(
            WebGrid webGrid,
            WebGridPagerModes mode,
            string firstText,
            string previousText,
            string nextText,
            string lastText,
            int numericLinksCount,
            string paginationStyle,
            bool explicitlyCalled)
        {
            var currentPage = webGrid.PageIndex;
            var totalPages = webGrid.PageCount;
            var lastPage = totalPages - 1;

            var ul = new TagBuilder("ul");
            ul.AddCssClass(ulClass);
            ul.AddCssClass(paginationStyle);

            var li = new List<TagBuilder>();

            if (webGrid.TotalRowCount <= webGrid.PageCount)
                return new HelperResult(writer => writer.Write(string.Empty));

            if (ModeEnabled(mode, WebGridPagerModes.FirstLast) && totalPages > 1)
            {
                var part = new TagBuilder("li")
                {
                    InnerHtml = GridLink(webGrid, webGrid.GetPageUrl(0), firstText)
                };
                part.AddCssClass(liClass);

                if (currentPage == 0) part.AddCssClass("disabled");

                li.Add(part);
            }

            if (ModeEnabled(mode, WebGridPagerModes.NextPrevious) && totalPages > 1)
            {
                var page = currentPage == 0 ? 0 : currentPage - 1;

                var part = new TagBuilder("li")
                {
                    InnerHtml = GridLink(webGrid, webGrid.GetPageUrl(page), previousText)
                };
                part.AddCssClass(liClass);

                if (currentPage == 0) part.AddCssClass("disabled");

                li.Add(part);
            }

            if (ModeEnabled(mode, WebGridPagerModes.Numeric) && totalPages > 1)
            {
                var last = currentPage + numericLinksCount / 2;
                var first = last - numericLinksCount + 1;
                if (last > lastPage)
                {
                    first -= last - lastPage;
                    last = lastPage;
                }

                if (first < 0)
                {
                    last = Math.Min(last + (0 - first), lastPage);
                    first = 0;
                }

                for (var i = first; i <= last; i++)
                {
                    var pageText = (i + 1).ToString(CultureInfo.InvariantCulture);
                    var part = new TagBuilder("li")
                    {
                        InnerHtml = GridLink(webGrid, webGrid.GetPageUrl(i), pageText)
                    };
                    part.AddCssClass(liClass);

                    if (i == currentPage) part.AddCssClass("active");

                    li.Add(part);
                }
            }

            if (ModeEnabled(mode, WebGridPagerModes.NextPrevious) && totalPages > 1)
            {
                var page = currentPage == lastPage ? lastPage : currentPage + 1;

                var part = new TagBuilder("li")
                {
                    InnerHtml = GridLink(webGrid, webGrid.GetPageUrl(page), nextText)
                };
                part.AddCssClass(liClass);

                if (currentPage == lastPage) part.AddCssClass("disabled");

                li.Add(part);
            }

            if (ModeEnabled(mode, WebGridPagerModes.FirstLast) && totalPages > 1)
            {
                var part = new TagBuilder("li")
                {
                    InnerHtml = GridLink(webGrid, webGrid.GetPageUrl(lastPage), lastText)
                };

                if (currentPage == lastPage) 
                    part.AddCssClass("disabled");

                li.Add(part);
            }

            ul.InnerHtml = string.Join("", li);

            var html = "";
            if (explicitlyCalled && webGrid.IsAjaxEnabled)
            {
                var span = new TagBuilder("span");
                span.MergeAttribute("data-swhgajax", "true");
                span.MergeAttribute("data-swhgcontainer", webGrid.AjaxUpdateContainerId);
                span.MergeAttribute("data-swhgcallback", webGrid.AjaxUpdateCallback);

                span.InnerHtml = ul.ToString();
                html = span.ToString();
            }
            else
            {
                html = ul.ToString();
            }

            return new HelperResult(writer => writer.Write(html));
        }

        private static string GridLink(WebGrid webGrid, string url, string text)
        {
            var builder = new TagBuilder("a");
            builder.SetInnerText(text);
            builder.MergeAttribute("href", url);
            builder.AddCssClass(aClass);
            if (webGrid.IsAjaxEnabled) 
                builder.MergeAttribute("data-swhglnk", "true");
            return builder.ToString(TagRenderMode.Normal);
        }

        private static bool ModeEnabled(WebGridPagerModes mode, WebGridPagerModes modeCheck)
        {
            return (mode & modeCheck) == modeCheck;
        }
    }
}