using System.Security.Cryptography;
using System.Text;
using Org.BouncyCastle.Crypto.Digests;
using Voicecat.V1;

namespace VoiceCat.Server.Data;

public sealed partial class AccountStore
{
    private static byte[] ChannelDigest(string password, byte[] salt)
    {
        var digest = new Blake2bDigest(salt, 32, null, null);
        byte[] bytes = Encoding.UTF8.GetBytes(password);
        byte[] hash = new byte[32];
        try { digest.BlockUpdate(bytes, 0, bytes.Length); digest.DoFinal(hash, 0); return hash; }
        finally { CryptographicOperations.ZeroMemory(bytes); }
    }

    public bool CheckChannelPassword(uint id, string password)
    {
        using var connection = Open();
        using var command = connection.CreateCommand();
        command.CommandText = "SELECT password_hash FROM channels WHERE id=$id";
        command.Parameters.AddWithValue("$id", id);
        if (command.ExecuteScalar() is not string stored) return false;
        if (stored.Length == 0) return true;
        if (stored.Length != 97 || stored[32] != ':') return false;
        try
        {
            byte[] salt = Convert.FromHexString(stored[..32]);
            return CryptographicOperations.FixedTimeEquals(ChannelDigest(password, salt), Convert.FromHexString(stored[33..]));
        }
        catch (FormatException) { return false; }
    }

    internal Channel SaveChannel(Channel channel, string password, bool create)
    {
        using var connection = Open();
        using var command = connection.CreateCommand();
        string hash = "";
        if (password.Length != 0)
        {
            byte[] salt = RandomNumberGenerator.GetBytes(16);
            hash = Convert.ToHexString(salt).ToLowerInvariant() + ":" + Convert.ToHexString(ChannelDigest(password, salt)).ToLowerInvariant();
        }
        string[] columns = ["parent_id", "name", "topic", "max_users", "type", "sort_order", "audio_codec", "audio_mode", "audio_sample_rate", "audio_bitrate_bps", "audio_frame_ms", "audio_application", "audio_fec", "audio_expected_packet_loss", "audio_dtx", "audio_complexity"];
        var a = channel.Audio;
        object[] values = [channel.ParentId, channel.Name, channel.Topic, channel.MaxUsers, (int)channel.Type, channel.Order, a.Codec, (int)a.Mode, a.SampleRate, a.BitrateBps, a.FrameMs, (int)a.Application, a.Fec, a.ExpectedPacketLoss, a.Dtx, a.Complexity];
        for (int i = 0; i < columns.Length; i++) command.Parameters.AddWithValue("$" + columns[i], values[i]);
        command.Parameters.AddWithValue("$hash", hash);
        command.Parameters.AddWithValue("$id", channel.Id);
        command.CommandText = create
            ? $"INSERT INTO channels ({string.Join(',', columns)},password_hash) VALUES ({string.Join(',', columns.Select(c => "$" + c))},$hash) RETURNING id"
            : $"UPDATE channels SET {string.Join(',', columns.Select(c => c + "=$" + c))},password_hash=CASE WHEN $hash='' THEN password_hash ELSE $hash END WHERE id=$id RETURNING id";
        var saved = channel.Clone();
        saved.Id = checked((uint)(long)(command.ExecuteScalar() ?? throw new InvalidDataException("Channel not found.")));
        saved.PasswordProtected = hash.Length != 0 || !create && CheckChannelPasswordPresent(saved.Id);
        return saved;
    }

    private bool CheckChannelPasswordPresent(uint id)
    {
        using var connection = Open();
        using var command = connection.CreateCommand();
        command.CommandText = "SELECT length(password_hash)>0 FROM channels WHERE id=$id";
        command.Parameters.AddWithValue("$id", id);
        return (long)command.ExecuteScalar()! != 0;
    }

    internal void DeleteChannel(uint id)
    {
        using var connection = Open();
        using var command = connection.CreateCommand();
        command.CommandText = "DELETE FROM channels WHERE id=$id";
        command.Parameters.AddWithValue("$id", id);
        command.ExecuteNonQuery();
    }
}