using System.IO;
using System.Text;

using SabreTools.IO;
using SabreTools.Core;
using SabreTools.FileTypes.Aaru;

namespace SabreTools.FileTypes
{
    /// <summary>
    /// AaruFormat code is based on the Aaru project
    /// See https://github.com/aaru-dps/Aaru/tree/master/Aaru.Images/AaruFormat
    /// </summary>
    public class AaruFormat : BaseFile
    {
        #region Private instance variables

        #region Header

        protected ulong Identifier;                     // 'AARUFRMT' (0x544D524655524141)
        protected string Application;                   // Name of application that created image
        protected byte ImageMajorVersion;               // Image format major version
        protected byte ImageMinorVersion;               // Image format minor version
        protected byte ApplicationMajorVersion;         // Major version of application that created image
        protected byte ApplicationMinorVersion;         // Minor version of application that created image
        protected AaruMediaType MediaType;              // Media type contained in image
        protected ulong IndexOffset;                    // Offset to index
        protected long CreationTime;                    // Windows filetime of creation time
        protected long LastWrittenTime;                 // Windows filetime of last written time

        #endregion

        #region Internal Values

        protected IndexHeader IndexHeader;
        protected IndexEntry[] IndexEntries;

        #endregion

        #endregion // Private instance variables

        #region Constructors

        /// <summary>
        /// Create a new AaruFormat from an input file
        /// </summary>
        /// <param name="filename">Filename respresenting the AaruFormat file</param>
        public static AaruFormat Create(string filename)
        {
            using (FileStream fs = File.OpenRead(filename))
            {
                return Create(fs);
            }
        }

        /// <summary>
        /// Create a new AaruFormat from an input stream
        /// </summary>
        /// <param name="aarustream">Stream representing the AaruFormat file</param>
        public static AaruFormat Create(Stream aarustream)
        {
            try
            {
                // Validate that this is actually a valid AaruFormat (by magic string alone)
                bool validated = ValidateHeader(aarustream);
                aarustream.SeekIfPossible(); // Seek back to start
                if (!validated)
                    return null;

                // Read and retrun the current AaruFormat
                AaruFormat generated = Deserialize(aarustream);
                if (generated != null)
                    generated.Type = FileType.AaruFormat;

                return generated;
            }
            catch
            {
                return null;
            }
        }

        #endregion

        #region Header Parsing

        /// <summary>
        /// Validate we start with the right magic number
        /// </summary>
        public static bool ValidateHeader(Stream aarustream)
        {
            // Read the magic string
            byte[] magicBytes = new byte[8];
            int read = aarustream.Read(magicBytes, 0, 8);

            // If we didn't read the magic fully, we don't have an AaruFormat
            if (read < 8)
                return false;

            // If the bytes don't match, we don't have an AaruFormat
            if (!magicBytes.StartsWith(Constants.AaruFormatSignature))
                return false;

            return true;
        }

        /// <summary>
        /// Read a stream as an AaruFormat
        /// </summary>
        /// <param name="stream">AaruFormat file as a stream</param>
        /// <returns>Populated AaruFormat file, null on failure</returns>
        public static AaruFormat Deserialize(Stream stream)
        {
            try
            {
                AaruFormat aif = new AaruFormat();

                using (BinaryReader br = new BinaryReader(stream, Encoding.Default, true))
                {
                    aif.Identifier = br.ReadUInt64();
                    aif.Application = Encoding.Unicode.GetString(br.ReadBytes(64), 0, 64);
                    aif.ImageMajorVersion = br.ReadByte();
                    aif.ImageMinorVersion = br.ReadByte();
                    aif.ApplicationMajorVersion = br.ReadByte();
                    aif.ApplicationMinorVersion = br.ReadByte();
                    aif.MediaType = (AaruMediaType)br.ReadUInt32();
                    aif.IndexOffset = br.ReadUInt64();
                    aif.CreationTime = br.ReadInt64();
                    aif.LastWrittenTime = br.ReadInt64();

                    // If the offset is bigger than the stream, we can't read it
                    if (aif.IndexOffset > (ulong)stream.Length)
                        return null;

                    // Otherwise, we read in the index header
                    stream.Seek((long)aif.IndexOffset, SeekOrigin.Begin);
                    aif.IndexHeader = IndexHeader.Deserialize(stream);
                    if (aif.IndexHeader.entries == 0)
                        return null;

                    // Get the list of entries
                    aif.IndexEntries = new IndexEntry[aif.IndexHeader.entries];
                    for (ushort index = 0; index < aif.IndexHeader.entries; index++)
                    {
                        aif.IndexEntries[index] = IndexEntry.Deserialize(stream);
                        switch (aif.IndexEntries[index].blockType)
                        {
                            // We don't do anything with these block types currently
                            case AaruBlockType.DataBlock:
                            case AaruBlockType.DeDuplicationTable:
                            case AaruBlockType.Index:
                            case AaruBlockType.Index2:
                            case AaruBlockType.GeometryBlock:
                            case AaruBlockType.MetadataBlock:
                            case AaruBlockType.TracksBlock:
                            case AaruBlockType.CicmBlock:
                            case AaruBlockType.DataPositionMeasurementBlock:
                            case AaruBlockType.SnapshotBlock:
                            case AaruBlockType.ParentBlock:
                            case AaruBlockType.DumpHardwareBlock:
                            case AaruBlockType.TapeFileBlock:
                            case AaruBlockType.TapePartitionBlock:
                            case AaruBlockType.CompactDiscIndexesBlock:
                                // No-op
                                break;

                            // Read in all available hashes
                            case AaruBlockType.ChecksumBlock:
                                // If the offset is bigger than the stream, we can't read it
                                if (aif.IndexEntries[index].offset > (ulong)stream.Length)
                                    return null;

                                // Otherwise, we read in the block
                                stream.Seek((long)aif.IndexEntries[index].offset, SeekOrigin.Begin);
                                ChecksumHeader checksumHeader = ChecksumHeader.Deserialize(stream);
                                if (checksumHeader.entries == 0)
                                    return null;

                                // Read through each and pick out the ones we care about
                                for (byte entry = 0; entry < checksumHeader.entries; entry++)
                                {
                                    ChecksumEntry checksumEntry = ChecksumEntry.Deserialize(stream);
                                    if (checksumEntry == null)
                                        continue;

                                    switch (checksumEntry.type)
                                    {
                                        case AaruChecksumAlgorithm.Invalid:
                                            break;
                                        case AaruChecksumAlgorithm.Md5:
                                            aif.MD5 = checksumEntry.checksum;
                                            break;
                                        case AaruChecksumAlgorithm.Sha1:
                                            aif.SHA1 = checksumEntry.checksum;
                                            break;
                                        case AaruChecksumAlgorithm.Sha256:
                                            aif.SHA256 = checksumEntry.checksum;
                                            break;
                                        case AaruChecksumAlgorithm.SpamSum:
                                            aif.SpamSum = checksumEntry.checksum;
                                            break;
                                    }
                                }

                                // Once we got hashes, we return early
                                return aif;
                        }
                    }
                }

                return aif;
            }
            catch
            {
                // We don't care what the error was at this point
                return null;
            }
        }

        #endregion
    }
}