using SQLInsight.Core.Data;

namespace SQLInsight.Collectors.Instance;

public sealed class ServerCollector : Collector<ServerSnapshot>
{
    public override string Name => "server";
    public override TimeSpan DefaultInterval => TimeSpan.FromMinutes(15);

    protected override async Task<ServerSnapshot> CollectAsync(CollectorContext context, ServerSnapshot? previous)
    {
        var version = context.Instance.Version;
        var ct = context.CancellationToken;

        if (version.Major < 9)
        {
            return await CollectSql2000Async(context).ConfigureAwait(false);
        }

        var memory = version.Major >= 11 ? "physical_memory_kb / 1024" : "physical_memory_in_bytes / 1048576";
        var vmType = version >= new Core.Instances.SqlServerVersion(10, 50, 2500, 0) ? "virtual_machine_type_desc" : "CAST(NULL AS nvarchar(60))";
        var sql = $"""
            SELECT
                {Db.StartTimeExpression(version)},
                cpu_count,
                (SELECT COUNT(*) FROM sys.dm_os_schedulers WHERE status = N'VISIBLE ONLINE'),
                (SELECT COUNT(DISTINCT parent_node_id) FROM sys.dm_os_schedulers WHERE status = N'VISIBLE ONLINE'),
                {memory},
                {vmType}
            FROM sys.dm_os_sys_info
            """;

        var snapshot = await Db.QuerySingleAsync(context.Connection, sql, r => new ServerSnapshot
        {
            CapturedAt = context.Now,
            SqlServerStartTime = r.DateTime(0),
            LogicalCpuCount = r.Int(1),
            VisibleOnlineSchedulers = r.Int(2),
            NumaNodeCount = version.Major >= 10 ? r.Int(3) : null,
            PhysicalMemoryMb = r.Long(4),
            VirtualMachineType = r.NullableString(5),
        }, ct).ConfigureAwait(false);

        return snapshot ?? throw new InvalidOperationException("sys.dm_os_sys_info returned no rows.");
    }

    private static async Task<ServerSnapshot> CollectSql2000Async(CollectorContext context)
    {
        var ct = context.CancellationToken;
        var startTime = await Db.StartTimeAsync(context.Connection, context.Instance.Version, ct).ConfigureAwait(false);

        // xp_msver: Index, Name, Internal_Value, Character_Value.
        var msver = await Db.QueryAsync(context.Connection, "EXEC master.dbo.xp_msver", r => (Name: r.String(1), Value: r.NullableLong(2)), ct)
            .ConfigureAwait(false);
        long? Get(string name) => msver.FirstOrDefault(m => string.Equals(m.Name, name, StringComparison.OrdinalIgnoreCase)).Value;

        return new ServerSnapshot
        {
            CapturedAt = context.Now,
            SqlServerStartTime = startTime,
            LogicalCpuCount = (int)(Get("ProcessorCount") ?? 0),
            PhysicalMemoryMb = Get("PhysicalMemory"),
        };
    }
}