using System;
using System.IO;
using System.Linq;
using Microsoft.AspNet.Http;
using Microsoft.AspNet.Mvc;
using Microsoft.AspNet.Mvc.Rendering;
using Microsoft.AspNet.Mvc.ViewEngines;

namespace Yavsc.Helpers
{
    public class TeXString  {

        public class Replacement {
            string target;
            string replacement;
            public Replacement(string target, string replacement){
                this.target=target;
                this.replacement=replacement;
            }
            public string Execute(string source)
            {
                return source.Replace(target,replacement);
            }
        }

        public readonly static Replacement[] SpecialCharsRendering = 
        {
            new Replacement("<","\\textless"),
            new Replacement(">","\\textgreater"),
            new Replacement("©","\\copyright"),
            new Replacement("®","\\textregistered"),
            new Replacement("\\","\\textbackslash"),
            new Replacement("™","\\texttrademark"),
            new Replacement("¶","\\P"),
            new Replacement("|","\\textbar"),
            new Replacement("%","\\%"),
            new Replacement("{","\\{"),
            new Replacement("}","\\}"),
            new Replacement("_","\\_"),
            new Replacement("#","\\#"),
            new Replacement("$","\\$"),
            new Replacement("_","\\_"),
            new Replacement("¿","\\textquestiondown"),
            new Replacement("§","\\S"),
            new Replacement("£","\\pounds"),
            new Replacement("&","\\&"),
            new Replacement("¡","\\textexclamdown"),
            new Replacement("†","\\dag"),
            new Replacement("–","\\textendash")
        };
        string data;
        public TeXString(string str) {
            data = str;
            foreach (var r in SpecialCharsRendering) {
                data = r.Execute(data);
            }
        }
        
        override public string ToString()
        {
            return data;
        }
    }
    public static class TeXHelpers
    {
        public static string NewLinesWith(this string target, string separator)
        { 
            var items = target.Split(new char[] {'\n'}).Where(
                s=> !string.IsNullOrWhiteSpace(s) ) ;

            return string.Join(separator, items);
        }

        public static TeXString ToTeX(string target, string lineSeparator="\n\\\\")
        {
            if (target==null) return null;
            return new TeXString(target.NewLinesWith(lineSeparator));
        }

        public static string RenderViewToString(
            this Controller controller, IViewEngine engine,
            IHttpContextAccessor httpContextAccessor, 
         string viewName, object model)
{
   using (var sw = new StringWriter())
  {
      if (engine == null)
       throw new InvalidOperationException("no engine");
       
    // try to find the specified view
    controller.TryValidateModel(model);
    ViewEngineResult viewResult = engine.FindPartialView(controller.ActionContext, viewName);
    // create the associated context
    ViewContext viewContext = new ViewContext();
    viewContext.ActionDescriptor = controller.ActionContext.ActionDescriptor;
    viewContext.HttpContext = controller.ActionContext.HttpContext;
    viewContext.TempData = controller.TempData;
    viewContext.View = viewResult.View;
    viewContext.Writer = sw;
    
    // write the render view with the given context to the stringwriter
    viewResult.View.RenderAsync(viewContext);
    viewResult.EnsureSuccessful();
    return sw.GetStringBuilder().ToString();
  }
}
    }
}