DagLink.cs

using System.IO;
using Google.Protobuf;

namespace Ipfs
{
    /// <summary>
    ///   A link to another node in the IPFS Merkle DAG.
    /// </summary>
    public class DagLink : IMerkleLink
    {
        /// <summary>
        ///   Create a new instance of <see cref="DagLink"/> class.
        /// </summary>
        /// <param name="name">The name associated with the linked node.</param>
        /// <param name="id">The <see cref="Cid"/> of the linked node.</param>
        /// <param name="size">The serialised size (in bytes) of the linked node.</param>
        public DagLink(string? name, Cid id, ulong size)
        {
            Name = name;
            Id = id;
            Size = size;
        }

        /// <summary>
        ///   Creates a new instance of the <see cref="DagLink"/> class from the
        ///   specified <see cref="IMerkleLink"/>.
        /// </summary>
        /// <param name="link">
        ///   Some type of a Merkle link.
        /// </param>
        public DagLink(IMerkleLink link)
        {
            Name = link.Name;
            Id = link.Id;
            Size = link.Size;
        }

        /// <summary>
        ///   Creates a new instance of the <see cref="DagLink"/> class from the
        ///   specified <see cref="Stream"/>.
        /// </summary>
        /// <param name="stream">
        ///   A <see cref="Stream"/> containing the binary representation of the
        ///   <b>DagLink</b>.
        /// </param>
        public DagLink(Stream stream)
        {
            (Name, Id, Size) = Read(stream);
        }

        /// <summary>
        ///   Creates a new instance of the <see cref="DagLink"/> class from the
        ///   specified <see cref="CodedInputStream"/>.
        /// </summary>
        /// <param name="stream">(
        ///   A <see cref="CodedInputStream"/> containing the binary representation of the
        ///   <b>DagLink</b>.
        /// </param>
        public DagLink(CodedInputStream stream)
        {
            (Name, Id, Size) = Read(stream);
        }

        /// <inheritdoc />
        public string? Name { get; private set; }

        /// <inheritdoc />
        public Cid Id { get; private set; }

        /// <inheritdoc />
        public ulong Size { get; private set; }

        /// <summary>
        ///   Writes the binary representation of the link to the specified <see cref="Stream"/>.
        /// </summary>
        /// <param name="stream">
        ///   The <see cref="Stream"/> to write to.
        /// </param>
        public void Write(Stream stream)
        {
            using var cos = new CodedOutputStream(stream, true);
            Write(cos);
        }

        /// <summary>
        ///   Writes the binary representation of the link to the specified <see cref="CodedOutputStream"/>.
        /// </summary>
        /// <param name="stream">
        ///   The <see cref="CodedOutputStream"/> to write to.
        /// </param>
        public void Write(CodedOutputStream stream)
        {
            stream.WriteTag(1, WireFormat.WireType.LengthDelimited);
            Id.Write(stream);

            if (Name is not null)
            {
                stream.WriteTag(2, WireFormat.WireType.LengthDelimited);
                stream.WriteString(Name);
            }

            stream.WriteTag(3, WireFormat.WireType.Varint);
            stream.WriteInt64((long)Size);
        }

        private (string?, Cid, ulong) Read(Stream stream)
        {
            using var cis = new CodedInputStream(stream, true);
            return Read(cis);
        }

        private (string?, Cid, ulong) Read(CodedInputStream stream)
        {
            string? name = null;
            Cid? id = null;
            ulong size = 0;
            while (!stream.IsAtEnd)
            {
                var tag = stream.ReadTag();
                switch (WireFormat.GetTagFieldNumber(tag))
                {
                    case 1:
                        id = Cid.Read(stream);
                        break;
                    case 2:
                        name = stream.ReadString();
                        break;
                    case 3:
                        size = (ulong)stream.ReadInt64();
                        break;
                    default:
                        throw new InvalidDataException("Unknown field number");
                }
            }

            if (id is null)
            {
                throw new InvalidDataException($"Missing CID id from record");
            }

            return (name, id, size);
        }

        /// <summary>
        ///   Returns the IPFS binary representation as a byte array.
        /// </summary>
        /// <returns>
        ///   A byte array.
        /// </returns>
        public byte[] ToArray()
        {
            using var ms = new MemoryStream();
            Write(ms);
            return ms.ToArray();
        }
    }
}