using System.Buffers;
using System.Security.Cryptography;
using Blake3;
using StabilityMatrix.Core.Models.Progress;

namespace StabilityMatrix.Core.Helper;

public static class FileHash
{
    public static async Task<string> GetHashAsync(HashAlgorithm hashAlgorithm, Stream stream, byte[] buffer, Action<ulong>? progress = default)
    {
        ulong totalBytesRead = 0;

        using (hashAlgorithm)
        {
            int bytesRead;
            while ((bytesRead = await stream.ReadAsync(buffer)) != 0)
            {
                totalBytesRead += (ulong) bytesRead;
                hashAlgorithm.TransformBlock(buffer, 0, bytesRead, null, 0);
                progress?.Invoke(totalBytesRead);
            }
            hashAlgorithm.TransformFinalBlock(buffer, 0, 0);
            var hash = hashAlgorithm.Hash;
            if (hash == null || hash.Length == 0)
            {
                throw new InvalidOperationException("Hash algorithm did not produce a hash.");
            }
            return BitConverter.ToString(hash).Replace("-", string.Empty).ToLowerInvariant();
        }
    }
    
    public static async Task<string> GetSha256Async(string filePath, IProgress<ProgressReport>? progress = default)
    {
        if (!File.Exists(filePath))
        {
            throw new FileNotFoundException($"Could not find file: {filePath}");
        }

        var totalBytes = Convert.ToUInt64(new FileInfo(filePath).Length);
        var shared = ArrayPool<byte>.Shared;
        var buffer = shared.Rent((int) FileTransfers.GetBufferSize(totalBytes));
        try
        {
            await using var stream = File.OpenRead(filePath);

            var hash = await GetHashAsync(SHA256.Create(), stream, buffer, totalBytesRead =>
            {
                progress?.Report(new ProgressReport(totalBytesRead, totalBytes));
            });
            return hash;
        }
        finally
        {
            shared.Return(buffer);
        }

    }

    public static async Task<string> GetBlake3Async(string filePath, IProgress<ProgressReport>? progress = default)
    {
        if (!File.Exists(filePath))
        {
            throw new FileNotFoundException($"Could not find file: {filePath}");
        }
        
        var totalBytes = Convert.ToUInt64(new FileInfo(filePath).Length);
        var readBytes = 0ul;
        var shared = ArrayPool<byte>.Shared;
        var buffer = shared.Rent((int) FileTransfers.GetBufferSize(totalBytes));
        try
        {
            await using var stream = File.OpenRead(filePath);
            using var hasher = Hasher.New();
            while (true)
            {
                var bytesRead = await stream.ReadAsync(buffer);
                if (bytesRead == 0)
                {
                    break;
                }
                readBytes += (ulong) bytesRead;
                hasher.Update(buffer.AsSpan(0, bytesRead));
                progress?.Report(new ProgressReport(readBytes, totalBytes));
            }
            return hasher.Finalize().ToString();
        }
        finally
        {
            shared.Return(buffer);
        }
    }
}