using System;
using System.Collections.Generic;
using System.IO;
using System.Security;
using System.Security.Principal;
using System.Text;
using System.Web;
using System.Web.UI;

namespace FileSharePortal
{
    public partial class Default : Page
    {
        private const string ShareRoot =
            @"\\LAN-DC1\Fileshare";


        private static readonly Dictionary<string, string> RootFolders =
            new Dictionary<string, string>(
                StringComparer.OrdinalIgnoreCase)
            {
                {
                    "Free Trial Documents",
                    "Dokumente rund um Free Trials"
                },

                {
                    "Sales Ordner",
                    "Dokumente für den Vertrieb"
                },

                {
                    "Technical User Folder",
                    "Technische Dokumente und Unterlagen"
                }
            };


        public string CurrentUser
        {
            get;
            private set;
        }


        public string CurrentPath
        {
            get;
            private set;
        }


        public string BreadcrumbHtml
        {
            get;
            private set;
        }


        public string ContentHtml
        {
            get;
            private set;
        }


        protected void Page_Load(
            object sender,
            EventArgs e)
        {
            Response.Cache.SetCacheability(
                HttpCacheability.NoCache);

            Response.Cache.SetNoStore();


            CurrentUser =
                WindowsIdentity.GetCurrent().Name;


            string relativePath =
                Request.QueryString["path"] ?? "";


            try
            {
                string physicalPath =
                    GetSafePhysicalPath(
                        relativePath);


                CurrentPath =
                    relativePath;


                BreadcrumbHtml =
                    BuildBreadcrumb(
                        relativePath);


                if (
                    string.IsNullOrEmpty(
                        relativePath))
                {
                    ContentHtml =
                        BuildRootFolderList();
                }
                else
                {
                    ContentHtml =
                        BuildDirectoryContents(
                            physicalPath,
                            relativePath);
                }
            }
            catch (UnauthorizedAccessException)
            {
                ContentHtml =
                    BuildError(
                        "Zugriff verweigert",
                        "Sie haben keine Berechtigung auf diesen Bereich zuzugreifen.");
            }
            catch (DirectoryNotFoundException)
            {
                ContentHtml =
                    BuildError(
                        "Ordner nicht gefunden",
                        "Der angeforderte Ordner existiert nicht.");
            }
            catch (SecurityException)
            {
                ContentHtml =
                    BuildError(
                        "Ungültiger Pfad",
                        "Der angeforderte Pfad ist nicht zulässig.");
            }
            catch
            {
                ContentHtml =
                    BuildError(
                        "Fehler",
                        "Der angeforderte Bereich konnte nicht geladen werden.");
            }
        }


        /*
         * ========================================================
         * ORDNER-ICON
         * ========================================================
         */

        private string FolderIconSvg()
        {
            return @"
                <svg
                    viewBox=""0 0 24 24""
                    xmlns=""http://www.w3.org/2000/svg""
                    aria-hidden=""true"">

                    <path
                        d=""M3 6.5C3 5.67 3.67 5 4.5 5H9L11 7H19.5C20.33 7 21 7.67 21 8.5V18.5C21 19.33 20.33 20 19.5 20H4.5C3.67 20 3 19.33 3 18.5V6.5Z""
                        fill=""none""
                        stroke=""currentColor""
                        stroke-width=""1.8""
                        stroke-linejoin=""round"" />

                </svg>";
        }


        /*
         * ========================================================
         * DATEI-ICON
         * ========================================================
         */

        private string FileIconSvg(
            string extension)
        {
            string label =
                "FILE";

            string fill =
                "#6b7280";

            switch (extension)
            {
                case ".pdf":

                    label = "PDF";
                    fill = "#dc2626";

                    break;


                case ".doc":
                case ".docx":

                    label = "WORD";
                    fill = "#2563eb";

                    break;


                case ".xls":
                case ".xlsx":
                case ".xlsm":

                    label = "XLS";
                    fill = "#16a34a";

                    break;


                case ".ppt":
                case ".pptx":

                    label = "PPT";
                    fill = "#ea580c";

                    break;


                case ".zip":
                case ".7z":
                case ".rar":
                case ".tar":
                case ".gz":

                    label = "ZIP";
                    fill = "#7c3aed";

                    break;


                case ".jpg":
                case ".jpeg":
                case ".png":
                case ".gif":
                case ".webp":
                case ".bmp":

                    label = "IMG";
                    fill = "#0891b2";

                    break;


                case ".mp3":
                case ".wav":
                case ".ogg":

                    label = "AUDIO";
                    fill = "#c026d3";

                    break;


                case ".mp4":
                case ".webm":
                case ".ogv":

                    label = "VIDEO";
                    fill = "#9333ea";

                    break;


                case ".txt":
                case ".log":
                case ".csv":
                case ".json":
                case ".xml":

                    label = "TXT";
                    fill = "#64748b";

                    break;


                case ".exe":
                case ".msi":

                    label = "APP";
                    fill = "#475569";

                    break;


                default:

                    label = "FILE";
                    fill = "#6b7280";

                    break;
            }


            return
                "<svg " +
                    "viewBox=\"0 0 64 64\" " +
                    "xmlns=\"http://www.w3.org/2000/svg\" " +
                    "aria-hidden=\"true\">" +

                    "<path " +
                        "d=\"M14 6H38L50 18V56H14Z\" " +
                        "fill=\"#ffffff\" " +
                        "stroke=\"" + fill + "\" " +
                        "stroke-width=\"3\" " +
                        "stroke-linejoin=\"round\" />" +

                    "<path " +
                        "d=\"M38 6V18H50\" " +
                        "fill=\"none\" " +
                        "stroke=\"" + fill + "\" " +
                        "stroke-width=\"3\" " +
                        "stroke-linejoin=\"round\" />" +

                    "<rect " +
                        "x=\"10\" " +
                        "y=\"38\" " +
                        "width=\"44\" " +
                        "height=\"15\" " +
                        "rx=\"4\" " +
                        "fill=\"" + fill + "\" />" +

                    "<text " +
                        "x=\"32\" " +
                        "y=\"49\" " +
                        "text-anchor=\"middle\" " +
                        "font-family=\"Arial, sans-serif\" " +
                        "font-size=\"8\" " +
                        "font-weight=\"700\" " +
                        "fill=\"#ffffff\">" +

                        HttpUtility.HtmlEncode(label) +

                    "</text>" +

                "</svg>";
        }


        /*
         * ========================================================
         * STARTSEITE
         * ========================================================
         */

        private string BuildRootFolderList()
        {
            var html =
                new StringBuilder();


            html.Append(
                "<div class=\"folder-grid\">"
            );


            int visibleFolders = 0;


            foreach (
                KeyValuePair<string, string> folder
                in RootFolders)
            {
                string folderName =
                    folder.Key;


                string path =
                    Path.Combine(
                        ShareRoot,
                        folderName);


                if (!Directory.Exists(path))
                    continue;


                if (!CanBrowseDirectory(path))
                    continue;


                visibleFolders++;


                string encodedPath =
                    HttpUtility.UrlEncode(
                        folderName);


                html.Append(
                    "<a class=\"folder-card\" href=\"?path=" +
                    HttpUtility.HtmlAttributeEncode(
                        encodedPath) +
                    "\">"
                );


                html.Append(
                    "<div class=\"folder-icon\">"
                );


                html.Append(
                    FolderIconSvg()
                );


                html.Append(
                    "</div>"
                );


                html.Append(
                    "<div class=\"folder-content\">"
                );


                html.Append(
                    "<div class=\"folder-title\">" +
                    HttpUtility.HtmlEncode(
                        folderName) +
                    "</div>"
                );


                html.Append(
                    "<div class=\"folder-description\">" +
                    HttpUtility.HtmlEncode(
                        folder.Value) +
                    "</div>"
                );


                html.Append(
                    "</div>"
                );


                html.Append(
                    "<div class=\"folder-arrow\">→</div>"
                );


                html.Append(
                    "</a>"
                );
            }


            html.Append(
                "</div>"
            );


            if (visibleFolders == 0)
            {
                return BuildError(
                    "Keine Bereiche verfügbar",
                    "Für Ihr Benutzerkonto wurden keine zugänglichen Bereiche gefunden.");
            }


            return html.ToString();
        }


        /*
         * ========================================================
         * VERZEICHNISINHALT
         * ========================================================
         */

        private string BuildDirectoryContents(
            string physicalPath,
            string relativePath)
        {
            var html =
                new StringBuilder();


            /*
             * ZURÜCK
             */
            html.Append(
                "<div class=\"toolbar\">"
            );


            string parentPath =
                GetParentRelativePath(
                    relativePath);


            if (parentPath != null)
            {
                if (
                    string.IsNullOrEmpty(
                        parentPath))
                {
                    html.Append(
                        "<a class=\"back-button\" href=\"./\">" +
                        "← Startseite" +
                        "</a>"
                    );
                }
                else
                {
                    html.Append(
                        "<a class=\"back-button\" href=\"?path=" +
                        HttpUtility.HtmlAttributeEncode(
                            HttpUtility.UrlEncode(
                                parentPath)) +
                        "\">" +
                        "← Zurück" +
                        "</a>"
                    );
                }
            }


            html.Append(
                "</div>"
            );


            var itemHtml =
                new StringBuilder();


            /*
             * ====================================================
             * UNTERORDNER
             * ====================================================
             */

            string[] directories =
                Directory.GetDirectories(
                    physicalPath);


            foreach (
                string directory
                in directories)
            {
                if (!CanBrowseDirectory(directory))
                    continue;


                string directoryName =
                    Path.GetFileName(directory);


                string childRelativePath =
                    CombineRelativePath(
                        relativePath,
                        directoryName);


                itemHtml.Append(
                    "<a class=\"item\" href=\"?path=" +
                    HttpUtility.HtmlAttributeEncode(
                        HttpUtility.UrlEncode(
                            childRelativePath)) +
                    "\">"
                );


                itemHtml.Append(
                    "<div class=\"item-icon\">"
                );


                itemHtml.Append(
                    FolderIconSvg()
                );


                itemHtml.Append(
                    "</div>"
                );


                itemHtml.Append(
                    "<div class=\"item-name\">" +
                    HttpUtility.HtmlEncode(
                        directoryName) +
                    "</div>"
                );


                itemHtml.Append(
                    "<div class=\"item-arrow\">→</div>"
                );


                itemHtml.Append(
                    "</a>"
                );
            }


            /*
             * ====================================================
             * DATEIEN
             * ====================================================
             */

            string[] files =
                Directory.GetFiles(
                    physicalPath);


            foreach (
                string file
                in files)
            {
                /*
                 * Eine Datei muss tatsächlich gelesen werden
                 * können. So erscheinen keine Dateien, auf die
                 * der Benutzer keine Leseberechtigung hat.
                 */
                if (!CanReadFile(file))
                    continue;


                string fileName =
                    Path.GetFileName(file);


                string extension =
                    Path.GetExtension(file)
                    .ToLowerInvariant();


                FileInfo info =
                    new FileInfo(file);


                string fileRelativePath =
                    CombineRelativePath(
                        relativePath,
                        fileName);


                string viewUrl =
                    "View.aspx?path=" +
                    HttpUtility.UrlEncode(
                        fileRelativePath);


                string downloadUrl =
                    "Download.aspx?path=" +
                    HttpUtility.UrlEncode(
                        fileRelativePath);


                /*
                 * Dateizeile
                 */
                itemHtml.Append(
                    "<div class=\"file-row\">"
                );


                /*
                 * Klickbarer Dateibereich
                 */
                itemHtml.Append(
                    "<a class=\"file-main\" href=\"" +
                    HttpUtility.HtmlAttributeEncode(
                        viewUrl) +
                    "\">"
                );


                itemHtml.Append(
                    "<div class=\"item-icon\">"
                );


                itemHtml.Append(
                    FileIconSvg(
                        extension)
                );


                itemHtml.Append(
                    "</div>"
                );


                itemHtml.Append(
                    "<div class=\"file-info\">"
                );


                itemHtml.Append(
                    "<div class=\"file-name\">" +
                    HttpUtility.HtmlEncode(
                        fileName) +
                    "</div>"
                );


                itemHtml.Append(
                    "<div class=\"file-details\">" +
                    HttpUtility.HtmlEncode(
                        GetFileTypeDescription(
                            extension)) +
                    " &nbsp;·&nbsp; " +
                    FormatFileSize(
                        info.Length) +
                    " &nbsp;·&nbsp; " +
                    info.LastWriteTime.ToString(
                        "dd.MM.yyyy HH:mm") +
                    "</div>"
                );


                itemHtml.Append(
                    "</div>"
                );


                itemHtml.Append(
                    "</a>"
                );


                /*
                 * Separater Download-Button
                 */
                itemHtml.Append(
                    "<a class=\"download\" href=\"" +
                    HttpUtility.HtmlAttributeEncode(
                        downloadUrl) +
                    "\">" +
                    "Download" +
                    "</a>"
                );


                itemHtml.Append(
                    "</div>"
                );
            }


            if (itemHtml.Length == 0)
            {
                html.Append(
                    "<div class=\"empty\">" +
                    "Dieser Ordner enthält keine für Sie sichtbaren Dateien oder Ordner." +
                    "</div>"
                );

                return html.ToString();
            }


            html.Append(
                "<div class=\"item-list\">"
            );


            html.Append(
                itemHtml.ToString()
            );


            html.Append(
                "</div>"
            );


            return html.ToString();
        }


        /*
         * ========================================================
         * DATEILESEBERECHTIGUNG
         * ========================================================
         */

        private bool CanReadFile(
            string path)
        {
            try
            {
                using (
                    FileStream stream =
                        new FileStream(
                            path,
                            FileMode.Open,
                            FileAccess.Read,
                            FileShare.ReadWrite |
                            FileShare.Delete))
                {
                }


                return true;
            }
            catch
            {
                return false;
            }
        }


        /*
         * ========================================================
         * DATEITYP BESCHREIBUNG
         * ========================================================
         */

        private string GetFileTypeDescription(
            string extension)
        {
            switch (extension)
            {
                case ".pdf":
                    return "PDF-Dokument";


                case ".doc":
                case ".docx":
                    return "Word-Dokument";


                case ".xls":
                case ".xlsx":
                case ".xlsm":
                    return "Excel-Tabelle";


                case ".ppt":
                case ".pptx":
                    return "PowerPoint-Präsentation";


                case ".jpg":
                case ".jpeg":
                case ".png":
                case ".gif":
                case ".webp":
                case ".bmp":
                    return "Bild";


                case ".mp3":
                case ".wav":
                case ".ogg":
                    return "Audiodatei";


                case ".mp4":
                case ".webm":
                case ".ogv":
                    return "Videodatei";


                case ".txt":
                    return "Textdatei";


                case ".csv":
                    return "CSV-Datei";


                case ".json":
                    return "JSON-Datei";


                case ".xml":
                    return "XML-Datei";


                case ".log":
                    return "Logdatei";


                case ".zip":
                case ".7z":
                case ".rar":
                case ".tar":
                case ".gz":
                    return "Archiv";


                case ".exe":
                    return "Anwendung";


                case ".msi":
                    return "Installationspaket";


                default:

                    if (
                        string.IsNullOrEmpty(
                            extension))
                    {
                        return "Datei";
                    }


                    return
                        extension
                        .TrimStart('.')
                        .ToUpperInvariant();
            }
        }


        /*
         * ========================================================
         * BREADCRUMB
         * ========================================================
         */

        private string BuildBreadcrumb(
            string relativePath)
        {
            var html =
                new StringBuilder();


            html.Append(
                "<div class=\"breadcrumb\">"
            );


            html.Append(
                "<a href=\"./\">FileShare</a>"
            );


            if (
                !string.IsNullOrEmpty(
                    relativePath))
            {
                string[] parts =
                    relativePath.Split(
                        new[] { '\\' },
                        StringSplitOptions.RemoveEmptyEntries);


                string accumulated =
                    "";


                for (
                    int i = 0;
                    i < parts.Length;
                    i++)
                {
                    accumulated =
                        CombineRelativePath(
                            accumulated,
                            parts[i]);


                    html.Append(
                        "<span>/</span>"
                    );


                    if (
                        i ==
                        parts.Length - 1)
                    {
                        html.Append(
                            "<strong>" +
                            HttpUtility.HtmlEncode(
                                parts[i]) +
                            "</strong>"
                        );
                    }
                    else
                    {
                        html.Append(
                            "<a href=\"?path=" +
                            HttpUtility.HtmlAttributeEncode(
                                HttpUtility.UrlEncode(
                                    accumulated)) +
                            "\">" +
                            HttpUtility.HtmlEncode(
                                parts[i]) +
                            "</a>"
                        );
                    }
                }
            }


            html.Append(
                "</div>"
            );


            return html.ToString();
        }


        /*
         * ========================================================
         * BERECHTIGUNG ORDNERVERZEICHNIS
         * ========================================================
         */

        private bool CanBrowseDirectory(
            string path)
        {
            try
            {
                using (
                    var enumerator =
                        Directory
                            .EnumerateFileSystemEntries(
                                path)
                            .GetEnumerator())
                {
                    enumerator.MoveNext();
                }


                return true;
            }
            catch
            {
                return false;
            }
        }


        /*
         * ========================================================
         * SICHEREN ORDNERPFAD ERMITTELN
         * ========================================================
         */

        private string GetSafePhysicalPath(
            string relativePath)
        {
            if (
                string.IsNullOrWhiteSpace(
                    relativePath))
            {
                return ShareRoot;
            }


            string decoded =
                HttpUtility.UrlDecode(
                    relativePath);


            decoded =
                decoded.Replace(
                    '/',
                    '\\');


            if (
                decoded.StartsWith("\\") ||
                decoded.Contains(":"))
            {
                throw new SecurityException();
            }


            string[] parts =
                decoded.Split(
                    new[] { '\\' },
                    StringSplitOptions.RemoveEmptyEntries);


            foreach (
                string part
                in parts)
            {
                if (
                    part == "." ||
                    part == "..")
                {
                    throw new SecurityException();
                }
            }


            string fullPath =
                Path.GetFullPath(
                    Path.Combine(
                        ShareRoot,
                        decoded));


            string normalizedRoot =
                Path.GetFullPath(
                    ShareRoot)
                .TrimEnd('\\') +
                "\\";


            if (
                !fullPath.StartsWith(
                    normalizedRoot,
                    StringComparison.OrdinalIgnoreCase))
            {
                throw new SecurityException();
            }


            if (
                !Directory.Exists(
                    fullPath))
            {
                throw new DirectoryNotFoundException();
            }


            if (!CanBrowseDirectory(fullPath))
            {
                throw new UnauthorizedAccessException();
            }


            return fullPath;
        }


        /*
         * ========================================================
         * PARENT
         * ========================================================
         */

        private string GetParentRelativePath(
            string path)
        {
            if (
                string.IsNullOrEmpty(
                    path))
            {
                return null;
            }


            int position =
                path.LastIndexOf('\\');


            if (position < 0)
            {
                return "";
            }


            return path.Substring(
                0,
                position);
        }


        /*
         * ========================================================
         * RELATIVEN PFAD ZUSAMMENBAUEN
         * ========================================================
         */

        private string CombineRelativePath(
            string parent,
            string child)
        {
            if (
                string.IsNullOrEmpty(
                    parent))
            {
                return child;
            }


            return
                parent.TrimEnd('\\') +
                "\\" +
                child;
        }


        /*
         * ========================================================
         * DATEIGRÖSSE
         * ========================================================
         */

        private string FormatFileSize(
            long bytes)
        {
            if (bytes < 1024)
            {
                return bytes + " B";
            }


            if (bytes < 1024 * 1024)
            {
                return
                    (bytes / 1024.0)
                    .ToString("0.0") +
                    " KB";
            }


            if (
                bytes <
                1024L * 1024L * 1024L)
            {
                return
                    (bytes /
                     1024.0 /
                     1024.0)
                    .ToString("0.0") +
                    " MB";
            }


            return
                (bytes /
                 1024.0 /
                 1024.0 /
                 1024.0)
                .ToString("0.0") +
                " GB";
        }


        /*
         * ========================================================
         * FEHLER
         * ========================================================
         */

        private string BuildError(
            string title,
            string message)
        {
            return
                "<div class=\"error\">" +

                "<h3>" +
                HttpUtility.HtmlEncode(
                    title) +
                "</h3>" +

                "<p>" +
                HttpUtility.HtmlEncode(
                    message) +
                "</p>" +

                "</div>";
        }
    }
}