using System.Globalization;
using Microsoft.Data.Sqlite;
using VoiceCat.Crypto;

namespace VoiceCat.Server.Data;

public sealed record Account(long Id, string Username, bool IsAdmin, long CreatedAt, long LastLogin);

public sealed partial class AccountStore : IDisposable
{
    static AccountStore() => SQLitePCL.Batteries_V2.Init();
    private readonly string connectionString;
    private readonly PasswordHasher hasher = new();
    private readonly SemaphoreSlim passwordWorkers = new(2);
    private bool disposed;
    private const string DummyHash = "$argon2id$v=19$m=65536,t=2,p=1$AAECAwQFBgcICQoLDA0ODw$Ki9tdSYqOtze3s3LAS6gv6I0buTIh2abdjWzY3GeLiE";

    public AccountStore(string path)
    {
        connectionString = new SqliteConnectionStringBuilder { DataSource = Path.GetFullPath(path), Pooling = false, DefaultTimeout = 5 }.ToString();
        using var connection = Open();
        using var setup = connection.CreateCommand();
        setup.CommandText = "PRAGMA journal_mode=WAL; PRAGMA synchronous=NORMAL; CREATE TABLE IF NOT EXISTS server_meta (key TEXT PRIMARY KEY, value TEXT NOT NULL);";
        setup.ExecuteNonQuery();
        using var transaction = connection.BeginTransaction();
        using var version = connection.CreateCommand();
        version.Transaction = transaction;
        version.CommandText = "SELECT value FROM server_meta WHERE key='schema_version'";
        object? stored = version.ExecuteScalar();
        if (stored is not null && (!int.TryParse((string)stored, NumberStyles.None, CultureInfo.InvariantCulture, out int revision) || revision is < 1 or > 2))
            throw new InvalidDataException("Unsupported server database schema version.");
        using var resource = typeof(AccountStore).Assembly.GetManifestResourceStream("VoiceCat.Server.Data.schema.sql")!;
        using var reader = new StreamReader(resource);
        using var migrate = connection.CreateCommand();
        migrate.Transaction = transaction;
        migrate.CommandText = reader.ReadToEnd() + "INSERT INTO server_meta (key,value) VALUES ('schema_version','2') ON CONFLICT(key) DO UPDATE SET value='2';";
        migrate.ExecuteNonQuery();
        transaction.Commit();
    }

    private SqliteConnection Open()
    {
        ObjectDisposedException.ThrowIf(disposed, this);
        var connection = new SqliteConnection(connectionString);
        try { connection.Open(); return connection; }
        catch { connection.Dispose(); throw; }
    }

    public async Task<Account> CreateAccountAsync(string username, string password, bool isAdmin = false, CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrEmpty(username);
        if (username.Length > 128) throw new ArgumentException("Username exceeds 128 characters.", nameof(username));
        string hash = await PasswordWorkAsync(() => hasher.Hash(password), cancellationToken).ConfigureAwait(false);
        cancellationToken.ThrowIfCancellationRequested();
        using var connection = Open();
        using var command = connection.CreateCommand();
        long created = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
        command.CommandText = "INSERT INTO accounts (username,pw_hash,is_admin,created_at) VALUES ($user,$hash,$admin,$created) RETURNING id";
        command.Parameters.AddWithValue("$user", username);
        command.Parameters.AddWithValue("$hash", hash);
        command.Parameters.AddWithValue("$admin", isAdmin ? 1 : 0);
        command.Parameters.AddWithValue("$created", created);
        return new((long)command.ExecuteScalar()!, username, isAdmin, created, 0);
    }

    public async Task<Account?> AuthenticateAsync(string username, string password, CancellationToken cancellationToken = default)
    {
        string? hash = null;
        Account? account = null;
        using (var connection = Open())
        using (var command = connection.CreateCommand())
        {
            command.CommandText = "SELECT id,pw_hash,is_admin,created_at,last_login FROM accounts WHERE username=$user";
            command.Parameters.AddWithValue("$user", username);
            using var reader = command.ExecuteReader();
            if (reader.Read())
            {
                hash = reader.GetString(1);
                account = new(reader.GetInt64(0), username, reader.GetInt64(2) != 0, reader.GetInt64(3), reader.GetInt64(4));
            }
        }
        bool verified = await PasswordWorkAsync(() => hasher.Verify(password, hash ?? DummyHash), cancellationToken).ConfigureAwait(false);
        if (hash is null || !verified) return null;
        cancellationToken.ThrowIfCancellationRequested();
        using var updated = Open();
        using var update = updated.CreateCommand();
        long login = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
        update.CommandText = "UPDATE accounts SET last_login=$login WHERE id=$id AND pw_hash=$hash";
        update.Parameters.AddWithValue("$login", login);
        update.Parameters.AddWithValue("$id", account!.Id);
        update.Parameters.AddWithValue("$hash", hash);
        return update.ExecuteNonQuery() == 1 ? account with { LastLogin = login } : null;
    }

    private async Task<T> PasswordWorkAsync<T>(Func<T> work, CancellationToken cancellationToken)
    {
        ObjectDisposedException.ThrowIf(disposed, this);
        await passwordWorkers.WaitAsync(cancellationToken).ConfigureAwait(false);
        try { return await Task.Run(work, cancellationToken).ConfigureAwait(false); }
        finally { passwordWorkers.Release(); }
    }

    public void Dispose() => disposed = true;

    public IReadOnlyList<Voicecat.V1.Channel> LoadChannels()
    {
        using var connection = Open();
        using var transaction = connection.BeginTransaction();
        using var seed = connection.CreateCommand();
        seed.Transaction = transaction;
        seed.CommandText = "SELECT COUNT(*) FROM channels";
        bool empty = (long)seed.ExecuteScalar()! == 0;
        seed.CommandText = """
            INSERT INTO channels (id,name,max_users) VALUES (1,'Lobby',20);
            INSERT INTO channels (id,name,audio_mode,audio_bitrate_bps,audio_application,audio_fec,audio_expected_packet_loss,audio_dtx,audio_complexity,sort_order)
            VALUES (2,'Music Room',1,128000,1,0,0,0,8,1);
            """;
        if (empty) seed.ExecuteNonQuery();
        transaction.Commit();
        using var command = connection.CreateCommand();
        command.CommandText = """
            SELECT id,parent_id,name,topic,password_hash,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
            FROM channels ORDER BY sort_order,id
            """;
        using var reader = command.ExecuteReader();
        var channels = new List<Voicecat.V1.Channel>();
        while (reader.Read())
        {
            channels.Add(new()
            {
                Id = checked((uint)reader.GetInt64(0)), ParentId = checked((uint)reader.GetInt64(1)),
                Name = reader.GetString(2), Topic = reader.GetString(3), PasswordProtected = reader.GetString(4).Length != 0,
                MaxUsers = checked((uint)reader.GetInt64(5)), Type = (Voicecat.V1.ChannelType)reader.GetInt32(6), Order = reader.GetInt32(7),
                Audio = new()
                {
                    Codec = checked((uint)reader.GetInt64(8)), Mode = (Voicecat.V1.ChannelMode)reader.GetInt32(9),
                    SampleRate = checked((uint)reader.GetInt64(10)), BitrateBps = checked((uint)reader.GetInt64(11)),
                    FrameMs = checked((uint)reader.GetInt64(12)), Application = (Voicecat.V1.OpusApplication)reader.GetInt32(13),
                    Fec = reader.GetInt32(14) != 0, ExpectedPacketLoss = checked((uint)reader.GetInt64(15)),
                    Dtx = reader.GetInt32(16) != 0, Complexity = checked((uint)reader.GetInt64(17))
                }
            });
        }
        return channels;
    }

    public bool IsBanned(string subjectType, string subject)
    {
        using var connection = Open();
        using var command = connection.CreateCommand();
        command.CommandText = "SELECT 1 FROM bans WHERE subject_type=$type AND subject=$subject AND (expires_at=0 OR expires_at>$now) LIMIT 1";
        command.Parameters.AddWithValue("$type", subjectType);
        command.Parameters.AddWithValue("$subject", subject);
        command.Parameters.AddWithValue("$now", DateTimeOffset.UtcNow.ToUnixTimeSeconds());
        return command.ExecuteScalar() is not null;
    }
}