using System;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.AspNetCore.Mvc.Rendering;

namespace AMWD.Common.AspNetCore.Extensions
{
	/// <summary>
	/// Extensions for the HTML (e.g. <see cref="IHtmlHelper"/>).
	/// </summary>
	public static class HtmlExtensions
	{
		/// <summary>
		/// The prefix used to identify JavaScript parts.
		/// </summary>
		public static string JSPrefix { get; set; } = "_JS_";

		/// <summary>
		/// The prefix used to identify CascadingStyleSheet parts.
		/// </summary>
		public static string CSSPrefix { get; set; } = "_CSS_";

		/// <summary>
		/// Add a js snippet.
		/// </summary>
		/// <typeparam name="T">The dynamic type of the <see cref="IHtmlHelper"/>.</typeparam>
		/// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance.</param>
		/// <param name="template">The template to use to add the snippet.</param>
		/// <returns></returns>
		public static T AddJS<T>(this IHtmlHelper<T> htmlHelper, Func<object, HelperResult> template)
		{
			htmlHelper.ViewContext.HttpContext.Items[$"{JSPrefix}{Guid.NewGuid()}"] = template;
			return default;
		}

		/// <summary>
		/// Renders the js snippets into the view.
		/// </summary>
		/// <typeparam name="T">The dynamic type of the <see cref="IHtmlHelper"/>.</typeparam>
		/// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance.</param>
		/// <returns></returns>
		public static T RenderJS<T>(this IHtmlHelper<T> htmlHelper)
		{
			foreach (object key in htmlHelper.ViewContext.HttpContext.Items.Keys)
			{
				if (key.ToString().StartsWith(JSPrefix) && htmlHelper.ViewContext.HttpContext.Items[key] is Func<object, HelperResult> template)
					htmlHelper.ViewContext.Writer.WriteLine(template(null));
			}
			return default;
		}

		/// <summary>
		/// Add a css snippet.
		/// </summary>
		/// <typeparam name="T">The dynamic type of the <see cref="IHtmlHelper"/>.</typeparam>
		/// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance.</param>
		/// <param name="template">The template to use to add the snippet.</param>
		/// <returns></returns>
		public static T AddCSS<T>(this IHtmlHelper<T> htmlHelper, Func<object, HelperResult> template)
		{
			htmlHelper.ViewContext.HttpContext.Items[$"{CSSPrefix}{Guid.NewGuid()}"] = template;
			return default;
		}

		/// <summary>
		/// Renders the css snippets into the view.
		/// </summary>
		/// <typeparam name="T">The dynamic type of the <see cref="IHtmlHelper"/>.</typeparam>
		/// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance.</param>
		/// <returns></returns>
		public static T RenderCSS<T>(this IHtmlHelper<T> htmlHelper)
		{
			foreach (object key in htmlHelper.ViewContext.HttpContext.Items.Keys)
			{
				if (key.ToString().StartsWith(CSSPrefix) && htmlHelper.ViewContext.HttpContext.Items[key] is Func<object, HelperResult> template)
					htmlHelper.ViewContext.Writer.WriteLine(template(null));
			}
			return default;
		}
	}
}