using System.Data.Common;
using SQLInsight.Core.Instances;

namespace SQLInsight.Connectivity;

/// <summary>
/// Reads version, edition and key settings from an instance. Works on every version from SQL Server 2000:
/// only <c>SERVERPROPERTY</c> is used, and properties an older version does not know return NULL.
/// </summary>
public static class InstanceProbe
{
    internal const string Query = """
        SELECT
            CAST(SERVERPROPERTY('ServerName') AS nvarchar(256)),
            CAST(SERVERPROPERTY('ProductVersion') AS nvarchar(128)),
            CAST(SERVERPROPERTY('ProductLevel') AS nvarchar(128)),
            CAST(SERVERPROPERTY('ProductUpdateLevel') AS nvarchar(128)),
            CAST(SERVERPROPERTY('Edition') AS nvarchar(128)),
            CAST(SERVERPROPERTY('EngineEdition') AS int),
            CAST(SERVERPROPERTY('IsClustered') AS int),
            CAST(SERVERPROPERTY('IsHadrEnabled') AS int)
        """;

    public static async Task<InstanceInfo> DetectAsync(DbConnection connection, CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(connection);

        await using var command = connection.CreateCommand();
        command.CommandText = Query;
        command.CommandTimeout = 30;

        await using var reader = await command.ExecuteReaderAsync(cancellationToken).ConfigureAwait(false);
        if (!await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
        {
            throw new InvalidOperationException("SERVERPROPERTY returned no rows.");
        }

        var productVersion = GetString(reader, 1);
        if (!SqlServerVersion.TryParse(productVersion, out var version))
        {
            throw new InvalidOperationException($"Could not parse ProductVersion '{productVersion}'.");
        }

        return new InstanceInfo
        {
            ServerName = GetString(reader, 0) ?? string.Empty,
            Version = version,
            ProductLevel = GetString(reader, 2),
            ProductUpdateLevel = GetString(reader, 3),
            Edition = GetString(reader, 4) ?? string.Empty,
            EngineEdition = reader.IsDBNull(5) ? EngineEdition.Unknown : (EngineEdition)reader.GetInt32(5),
            IsClustered = GetBool(reader, 6),
            IsHadrEnabled = GetBool(reader, 7),
        };
    }

    private static string? GetString(DbDataReader reader, int ordinal) =>
        reader.IsDBNull(ordinal) ? null : reader.GetString(ordinal);

    private static bool? GetBool(DbDataReader reader, int ordinal) =>
        reader.IsDBNull(ordinal) ? null : reader.GetInt32(ordinal) == 1;
}