<%@ WebHandler Language="C#" Class="GetItems" %>

using System;
using System.Web;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web.Script.Serialization;

public class GetItems : IHttpHandler
{
    public void ProcessRequest(HttpContext context)
    {
        context.Response.Clear();
        context.Response.ContentType = "application/json";
        context.Response.ContentEncoding = Encoding.UTF8;
        context.Response.TrySkipIisCustomErrors = true;

        try
        {
            List<FileMetadata> fileList = GetFileList("/", "*");

            JavaScriptSerializer serializer = new JavaScriptSerializer
            {
                MaxJsonLength = int.MaxValue
            };

            context.Response.StatusCode = 200;
            context.Response.Write(serializer.Serialize(fileList));
        }
        catch (Exception ex)
        {
            context.Response.StatusCode = 500;

            JavaScriptSerializer serializer = new JavaScriptSerializer();

            context.Response.Write(serializer.Serialize(new
            {
                error = "Unable to retrieve the file list.",
                details = ex.Message
            }));
        }

        context.ApplicationInstance.CompleteRequest();
    }

    private List<FileMetadata> GetFileList(string directories, string extension)
    {
        List<FileMetadata> fileList = new List<FileMetadata>();

        string docRoot = HttpContext.Current.Server
            .MapPath("/")
            .TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);

        foreach (string directory in directories.Split(','))
        {
            string virtualDirectory = directory.Trim();

            if (string.IsNullOrWhiteSpace(virtualDirectory))
            {
                continue;
            }

            string fullPath = HttpContext.Current.Server.MapPath(virtualDirectory);

            if (!Directory.Exists(fullPath))
            {
                continue;
            }

            string searchPattern =
                string.IsNullOrWhiteSpace(extension) || extension == "*"
                    ? "*.*"
                    : "*." + extension.TrimStart('.');

            IEnumerable<string> files = Directory.EnumerateFiles(
                fullPath,
                searchPattern,
                SearchOption.AllDirectories
            );

            foreach (string file in files.Distinct(StringComparer.OrdinalIgnoreCase))
            {
                FileInfo fileInfo = new FileInfo(file);

                string relativePath = file.Substring(docRoot.Length)
                    .Replace("\\", "/");

                if (!relativePath.StartsWith("/"))
                {
                    relativePath = "/" + relativePath;
                }

                fileList.Add(new FileMetadata
                {
                    path = relativePath,
                    last_modified = fileInfo.LastWriteTime.ToString(
                        "yyyy-MM-dd HH:mm:ss"
                    )
                });
            }
        }

        return fileList
            .OrderBy(file => file.path, StringComparer.OrdinalIgnoreCase)
            .ToList();
    }

    public class FileMetadata
    {
        public string path { get; set; }
        public string last_modified { get; set; }
    }

    public bool IsReusable
    {
        get { return false; }
    }
}