using System;
using System.Collections.Concurrent;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace LightlessSync.Utils;

public static class Crypto
{
    //This buffersize seems to be the best sweetpoint for Linux and Windows
    private const int _bufferSize = 65536;
#pragma warning disable SYSLIB0021 // Type or member is obsolete

    private static readonly ConcurrentDictionary<(string, ushort), string> _hashListPlayersSHA256 = new();
    private static readonly ConcurrentDictionary<string, string> _hashListSHA256 = new(StringComparer.Ordinal);
    private static readonly SHA256CryptoServiceProvider _sha256CryptoProvider = new();

    public static string GetFileHash(this string filePath)
    {
        using SHA1 sha1 = SHA1.Create();
        using FileStream stream = File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete);
        return BitConverter.ToString(sha1.ComputeHash(stream)).Replace("-", "", StringComparison.Ordinal);
    }

    public static async Task<string> GetFileHashAsync(string filePath, CancellationToken cancellationToken = default)
    {
        var stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete, bufferSize: _bufferSize, options: FileOptions.Asynchronous);
        await using (stream.ConfigureAwait(false))
        {
            using var sha1 = SHA1.Create();

            var buffer = new byte[8192];
            int bytesRead;
            while ((bytesRead = await stream.ReadAsync(buffer, cancellationToken).ConfigureAwait(false)) > 0)
            {
                sha1.TransformBlock(buffer, 0, bytesRead, outputBuffer: null, 0);
            }

            sha1.TransformFinalBlock([], 0, 0);

            return Convert.ToHexString(sha1.Hash!);
        }
    }

    public static string GetHash256(this (string, ushort) playerToHash)
    {
        return _hashListPlayersSHA256.GetOrAdd(playerToHash, key => ComputeHashSHA256(key.Item1 + key.Item2.ToString()));
    }

    public static string GetHash256(this string stringToHash)
    {
        return _hashListSHA256.GetOrAdd(stringToHash, ComputeHashSHA256);
    }

    private static string ComputeHashSHA256(string stringToCompute)
    {
        using var sha = SHA256.Create();
        return BitConverter.ToString(sha.ComputeHash(Encoding.UTF8.GetBytes(stringToCompute))).Replace("-", "", StringComparison.Ordinal);
    }
#pragma warning restore SYSLIB0021 // Type or member is obsolete
}