UoW

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Web.Mvc;
using System.Web.Routing;

/*
 * TODO:
 * auto_discovery_link_tag
 * cache_asset_timestamps
 * cache_asset_timestamps=
 * register_javascript_expansion
 * register_javascript_include_default
 * register_stylesheet_expansion
 */

namespace MvcApplication1 {
    public static class HtmlExtensions {

        public static string ASSETS_DIR = "~/Content";
        public static string JAVASCRIPTS_DIR = ASSETS_DIR + "/js";
        public static string STYLESHEETS_DIR = ASSETS_DIR + "/css";
        public static string IMAGES_DIR = ASSETS_DIR + "/img";
        public static string[] JAVASCRIPT_DEFAULT_SOURCES = new [] { "jquery" };
        public static string[] STYLESHEET_DEFAULT_SOURCES = new [] { "" };

        public static string ScriptPath(this HtmlHelper html, string src) {
            return html.AssetPath(src, JAVASCRIPTS_DIR, "js");
        }

        public static string Script(this HtmlHelper html) {
            return MultipleAssets(html.Script, MergeList(JAVASCRIPT_DEFAULT_SOURCES, "application"));
        }

        public static string Script(this HtmlHelper html, params string[] sources) {
            return MultipleAssets(html.Script, sources);
        }
        
        public static string Script(this HtmlHelper html, string src) {
            if(string.IsNullOrEmpty(src)) return string.Empty;

            var tag = new TagBuilder("script");
            tag.MergeAttribute("type", "text/javascript");
            tag.MergeAttribute("src", html.ScriptPath(src));

            return tag.ToString(TagRenderMode.Normal);
        }

        public static string StylePath(this HtmlHelper html, string href) {
            return html.AssetPath(href, STYLESHEETS_DIR, "css");
        }

        public static string Style(this HtmlHelper html) {
            return MultipleAssets(html.Style, MergeList(STYLESHEET_DEFAULT_SOURCES, "application"));
        }

        public static string Style(this HtmlHelper html, params string[] styles) {
            return MultipleAssets(html.Style, styles);
        }

        public static string Style(this HtmlHelper html, string href) {
            if(string.IsNullOrEmpty(href)) return string.Empty;

            var tag = new TagBuilder("link");
            tag.MergeAttribute("rel", "stylesheet");
            tag.MergeAttribute("type", "text/css");
            tag.MergeAttribute("href", html.StylePath(href));

            return tag.ToString(TagRenderMode.SelfClosing);
        }

        public static string ImagePath(this HtmlHelper html, string src) {
            return html.AssetPath(src, IMAGES_DIR, "png");
        }

        public static string Image(this HtmlHelper html, string src) {
            return html.Image(src, null);
        }

        public static string Image(this HtmlHelper html, string src, object htmlAttributes) {
            if(string.IsNullOrEmpty(src)) return string.Empty;

            var tag = new TagBuilder("img");
            tag.MergeAttributes(new RouteValueDictionary(htmlAttributes));
            tag.MergeAttribute("src", html.ImagePath(src));

            return tag.ToString(TagRenderMode.SelfClosing);
        }

        private static string Timestamp(this HtmlHelper html, string path) {
            var local = html.ViewContext.HttpContext.Server.MapPath(path);
            return File.Exists(local) ? File.GetLastWriteTimeUtc(local).ToString("yyyyMMddhhmmssfff") : string.Empty;
        }

        private static string CombinePath(params string[] paths) {
            return paths.Aggregate(Path.Combine).Replace(@"\", "/");
        }
        
        private static string AssetPath(this HtmlHelper html, string path, string dir, string ext) {
            if(string.IsNullOrEmpty(path)) return string.Empty;

            var url = path;
            if(string.IsNullOrEmpty(Path.GetExtension(path))) url += "." + ext;

            Uri uri;
            if(Uri.TryCreate(url, UriKind.Absolute, out uri) && uri.Scheme != "file") return url;

            if(!url.StartsWith("~") && !url.StartsWith("/")) url = CombinePath(dir, url);
            url += "?" + html.Timestamp(url);

            var root = html.ViewContext.HttpContext.Request.ApplicationPath;
            if(url.StartsWith("~")) url = CombinePath(root, url.Substring(2));

            return url;
        }

        private static string MultipleAssets(Func<string, string> func, params string[] sources) {
            return string.Join("\n", sources.Select(func).ToArray());
        }

        private static T[] MergeList<T>(IEnumerable<T> first, params T[] others) {
            return new List<T>(first).Concat(others).ToArray();
        }

    }
}