using System;
using System.Globalization;
using System.IO;
using System.Text;
using LibGit2Sharp.Core;

namespace LibGit2Sharp
{
    /// <summary>
    /// Logic for tar archiving (not the actual tar format, but the overal logic related to tar+git) is taken
    /// from https://github.com/git/git/blob/master/archive-tar.c.
    /// </summary>
    internal class TarArchiver : ArchiverBase, IDisposable
    {
        private readonly TarWriter writer;

        public TarArchiver(FileStream output)
        {
            writer = new TarWriter(output);
        }

        #region Overrides of ArchiverBase

        public override void BeforeArchiving(Tree tree, ObjectId oid, DateTimeOffset modificationTime)
        {
            if (oid == null)
            {
                return;
            }

            // Store the sha in the pax_global_header
            using (var stream = new MemoryStream(Encoding.ASCII.GetBytes(
                string.Format(CultureInfo.InvariantCulture, "52 comment={0}\n", oid.Sha))))
            {
                writer.Write("pax_global_header", stream, modificationTime, "666".OctalToInt32(),
                    "0", "0", 'g', "root", "root", "0", "0", oid.Sha, false);
            }
        }

        protected override void AddTreeEntry(string path, TreeEntry entry, DateTimeOffset modificationTime)
        {
            switch (entry.Mode)
            {
                case Mode.GitLink:
                case Mode.Directory:
                    writer.Write(path + "/", null, modificationTime, "775".OctalToInt32(),
                        "0", "0", '5', "root", "root", "0", "0", entry.TargetId.Sha, false);
                    break;
                case Mode.ExecutableFile:
                case Mode.NonExecutableFile:
                case Mode.NonExecutableGroupWritableFile:
                    var blob = ((Blob) entry.Target);

                    WriteStream(path, entry, modificationTime,
                        () => blob.IsBinary ? blob.GetContentStream() : blob.GetContentStream(new FilteringOptions(path)));
                    break;
                case Mode.SymbolicLink:
                    using (Stream contentStream = ((Blob)entry.Target).GetContentStream(new FilteringOptions(path)))
                    {
                        writer.Write(path, contentStream, modificationTime, "777".OctalToInt32(),
                            "0", "0", '2', "root", "root", "0", "0", entry.TargetId.Sha, true);
                    }
                    break;
                default:
                    throw new InvalidOperationException(
                        string.Format(CultureInfo.InvariantCulture, "Unsupported file mode: {0} (sha1: {1}).", entry.Mode, entry.TargetId.Sha));
            }
        }

        private void WriteStream(string path, TreeEntry entry, DateTimeOffset modificationTime, Func<Stream> streamer)
        {
            using (Stream contentStream = streamer())
            {
                writer.Write(path, contentStream, modificationTime,
                    (entry.Mode == Mode.ExecutableFile) ? "775".OctalToInt32() : "664".OctalToInt32(),
                    "0", "0", '0', "root", "root", "0", "0", entry.TargetId.Sha, false);
            }
        }

        #endregion

        #region Implementation of IDisposable

        public void Dispose()
        {
            writer.Dispose();
        }

        #endregion
    }
}