using System;
using System.IO;

namespace Packaging.Targets.IO
{
    /// <summary>
    /// Represents a <c>Tar</c> archive.
    /// </summary>
    public class TarFile : ArchiveFile
    {
        private TarHeader entryHeader;

        /// <summary>
        /// Initializes a new instance of the <see cref="TarFile"/> class.
        /// </summary>
        /// <param name="stream">
        /// A <see cref="Stream"/> which represents the tar file.
        /// </param>
        /// <param name="leaveOpen">
        /// <see langword="true"/> to leave the underlying <paramref name="stream"/> open when this <see cref="TarFile"/>
        /// is disposed of; otherwise, <see langword="false"/>.
        /// </param>
        public TarFile(Stream stream, bool leaveOpen)
            : base(stream, leaveOpen)
        {
        }

        /// <summary>
        /// Gets the link target of this file.
        /// </summary>
        public string LinkName
        {
            get;
            private set;
        }

        /// <inheritdoc/>
        public override bool Read()
        {
            this.Align(512);
            this.EntryStream?.Dispose();
            this.EntryStream = null;

            this.entryHeader = this.Stream.ReadStruct<TarHeader>();
            this.FileHeader = this.entryHeader;
            this.FileName = this.entryHeader.FileName;
            this.LinkName = this.entryHeader.LinkName;

            // There are two empty blocks at the end of the file.
            if (string.IsNullOrEmpty(this.entryHeader.Magic))
            {
                return false;
            }

            if (this.entryHeader.Magic != "ustar")
            {
                throw new InvalidDataException("The magic for the file entry is invalid");
            }

            this.Align(512);

            // TODO: Validate Checksum
            this.EntryStream = new SubStream(this.Stream, this.Stream.Position, this.entryHeader.FileSize, leaveParentOpen: true);

            if (this.entryHeader.TypeFlag == TarTypeFlag.LongName)
            {
                var longFileName = this.ReadAsUtf8String();
                var read = this.Read();
                this.FileName = longFileName;

                return read;
            }
            else if (this.entryHeader.TypeFlag == TarTypeFlag.LongLink)
            {
                var longLinkName = this.ReadAsUtf8String();
                var read = this.Read();
                this.LinkName = longLinkName;
                return read;
            }
            else
            {
                return true;
            }
        }
    }
}