using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CDPShared
{
    public class YellowFile
    {
        private string _filePath;
        public string FileId { get; set; }  // this is actually the FMAP Id internally 
        public string CloudId { get; set; }  // this isn't being used yet.  Gene 2021.11.17
        public string CircleId { get; set; }
        public string TopicId { get; set; }
        public string DecryptionId { get; set; }
        public string OwnerId { get; set; }  // this is a device Id 
        public Int32 RevisionNo { get; set; }
        public Int32 EncryptionMethod { get; set; }
        public UInt64 EncryptedBlockSize { get; set; }
        public DateTime FileAccessTime { get; set; }  // I'm not sure when this gets 'set' or what it should be.  but make it UTC
        public DateTime FileModificationTime { get; set; }  // this should be when the file header was built in UTC
        public DateTime FileStatusTime { get; set; }  // not sure on this one either.
        public string Comment;

        public YellowFile(string filePath)
        {
            _filePath = filePath;
            using (FileStream fsIn = new FileStream(_filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
            {
                ReadHeader(fsIn);
            }
        }
        protected void ReadHeader(FileStream fs)
        {
            BinaryReader br = new BinaryReader(fs);
            var versionBytes = br.ReadBytes(8);  // should be 'Circle1'
            UInt64 encyptedDataPos = br.ReadUInt64();
            FileId = new Guid(br.ReadBytes(16)).ToString();
            CloudId = new Guid(br.ReadBytes(16)).ToString();
            CircleId = new Guid(br.ReadBytes(16)).ToString();
            TopicId = new Guid(br.ReadBytes(16)).ToString();
            DecryptionId = new Guid(br.ReadBytes(16)).ToString();
            OwnerId = new Guid(br.ReadBytes(16)).ToString();

            // the file format has IV being 32 byte, but we only need 16
            br.ReadBytes(16);  // skip over IV
            br.ReadBytes(16);  // skip over the extra 16 bytes

            RevisionNo = br.ReadInt32();
            EncryptionMethod = br.ReadInt32();
            EncryptedBlockSize = br.ReadUInt64();
            FileAccessTime = DateTime.FromBinary(br.ReadInt64());
            FileModificationTime = DateTime.FromBinary(br.ReadInt64());
            FileStatusTime = DateTime.FromBinary(br.ReadInt64());
            Comment = Encoding.Unicode.GetString(br.ReadBytes(256)).Trim('\0');
            br.ReadBytes(40); // reserved
            byte[] hash = br.ReadBytes(32);
            Debug.Assert(fs.Position == 512);
        }

        public void UpdateOwner(string ownerId)
        {
            Guid owner = Guid.Parse(ownerId);
            using (FileStream fs = new FileStream(_filePath, FileMode.Open))
            {
                fs.Position = 96;
                byte[] guidBytes = owner.ToByteArray();
                fs.Write(guidBytes, 0, guidBytes.Length);
            }
        }
    }
}