using System.IO;

using ICSharpCode.SharpZipLib.Core;
using ICSharpCode.SharpZipLib.Zip;

namespace Fab2ApprovalSystem.Misc;

public class Zipper {

    /// <summary>
    /// Compresses the files in the nominated folder, and creates a zip file on disk named as outPathname.
    /// </summary>

    public void CreateZip(string outPathname, string folderName) {
        // TODO Try and Catch block
        Directory.CreateDirectory(Path.GetDirectoryName(outPathname));

        FileStream fsOut = File.Create(outPathname);
        ZipOutputStream zipStream = new(fsOut);

        zipStream.SetLevel(3); // 0-9, 9 being the highest level of compression

        // This setting will strip the leading part of the folder path in the entries, to
        // make the entries relative to the starting folder.
        // To include the full path for each entry up to the drive root, assign folderOffset = 0.
        int folderOffset = folderName.Length + (folderName.EndsWith("\\") ? 0 : 1);

        CompressFolder(folderName, zipStream, folderOffset);

        zipStream.IsStreamOwner = true; // Makes the Close also Close the underlying stream
        zipStream.Close();
    }

    /// <summary>
    /// Recurses down the folder structure
    /// </summary>

    private void CompressFolder(string path, ZipOutputStream zipStream, int folderOffset) {
        // TODO Try and Catch block
        string[] files = Directory.GetFiles(path);

        foreach (string filename in files) {
            FileInfo fi = new(filename);

            string entryName = filename.Substring(folderOffset); // Makes the name in zip based on the folder
            entryName = ZipEntry.CleanName(entryName); // Removes drive from name and fixes slash direction
            ZipEntry newEntry = new(entryName);
            newEntry.DateTime = fi.LastWriteTime; // Note the zip format stores 2 second granularity

            // Specifying the AESKeySize triggers AES encryption. Allowable values are 0 (off), 128 or 256.
            // A password on the ZipOutputStream is required if using AES.
            //   newEntry.AESKeySize = 256;

            // To permit the zip to be unpacked by built-in extractor in WinXP and Server2003, WinZip 8, Java, and other older code,
            // you need to do one of the following: Specify UseZip64.Off, or set the Size.
            // If the file may be bigger than 4GB, or you do not need WinXP built-in compatibility, you do not need either,
            // but the zip will be in Zip64 format which not all utilities can understand.
            //   zipStream.UseZip64 = UseZip64.Off;
            newEntry.Size = fi.Length;

            zipStream.PutNextEntry(newEntry);

            // Zip the file in buffered chunks
            // the "using" will close the stream even if an exception occurs
            byte[] buffer = new byte[4096];
            using (FileStream streamReader = File.OpenRead(filename)) {
                StreamUtils.Copy(streamReader, zipStream, buffer);
            }
            zipStream.CloseEntry();
        }
        string[] folders = Directory.GetDirectories(path);
        foreach (string folder in folders) {
            CompressFolder(folder, zipStream, folderOffset);
        }
    }

}