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

namespace SQLInsight.Collectors.Instance;

/// <summary>
/// The instance's setup for the configuration page and its change log: collation, services and accounts, Instant File
/// Initialization, Lock Pages in Memory, tempdb files and default paths, plus <c>sp_configure</c> and trace flags for
/// the fingerprint. Changes are computed against the previous collection, which the agent restores from the repository
/// after a restart, so a change made while the agent was down is still reported.
/// </summary>
public sealed class InstanceConfigurationCollector : Collector<InstanceConfigurationSnapshot>
{
    // SERVERPROPERTY returns NULL for properties an older version does not know, so this runs everywhere.
    internal const string PropertiesSql = """
        SELECT CAST(SERVERPROPERTY('ProductVersion') AS nvarchar(128)), CAST(SERVERPROPERTY('ProductLevel') AS nvarchar(128)),
               CAST(SERVERPROPERTY('Edition') AS nvarchar(128)), CAST(SERVERPROPERTY('Collation') AS nvarchar(128)),
               CAST(SERVERPROPERTY('InstanceDefaultDataPath') AS nvarchar(260)), CAST(SERVERPROPERTY('InstanceDefaultLogPath') AS nvarchar(260))
        """;

    // Which optional columns this build has: Instant File Initialization and the memory model came in service packs.
    internal const string ColumnsSql = """
        SELECT COL_LENGTH('sys.dm_server_services', 'instant_file_initialization_enabled'), COL_LENGTH('sys.dm_os_sys_info', 'sql_memory_model_desc')
        """;

    internal const string TempdbSql = """
        SELECT name, type_desc, CAST(size AS bigint) / 128, growth, is_percent_growth, max_size
        FROM sys.master_files WHERE database_id = 2 ORDER BY file_id
        """;

    internal const string MemoryModelSql = "SELECT sql_memory_model_desc FROM sys.dm_os_sys_info";

    /// <param name="instantFileInitialization">Whether this build has the instant_file_initialization_enabled column.</param>
    internal static string BuildServicesSql(bool instantFileInitialization)
    {
        var ifi = instantFileInitialization ? "instant_file_initialization_enabled" : "CAST(NULL AS nvarchar(1))";
        return $"SELECT servicename, service_account, startup_type_desc, status_desc, {ifi} FROM sys.dm_server_services";
    }

    public override string Name => "instance-config";
    public override TimeSpan DefaultInterval => TimeSpan.FromMinutes(15);

    protected override async Task<InstanceConfigurationSnapshot> CollectAsync(CollectorContext context, InstanceConfigurationSnapshot? previous)
    {
        var ct = context.CancellationToken;
        var connection = context.Connection;
        var properties = (await Db.QueryAsync(connection, PropertiesSql, r => (Version: r.NullableString(0), Level: r.NullableString(1),
            Edition: r.NullableString(2), Collation: r.NullableString(3), DataPath: r.NullableString(4), LogPath: r.NullableString(5)), ct).ConfigureAwait(false)).FirstOrDefault();

        var snapshot = new InstanceConfigurationSnapshot
        {
            CapturedAt = context.Now,
            ProductVersion = properties.Version,
            ProductLevel = properties.Level,
            Edition = properties.Edition,
            Collation = properties.Collation,
            DefaultDataPath = properties.DataPath,
            DefaultLogPath = properties.LogPath,
        };

        if (context.Instance.Version.Major >= 9)
        {
            var tempdb = await Db.QueryAsync(connection, TempdbSql, r => new TempdbFile(
                r.String(0), r.String(1), r.Long(2), Growth(r.Long(3), r.Bool(4)), MaxSize(r.Long(5))), ct).ConfigureAwait(false);
            snapshot = snapshot with { TempdbFiles = tempdb };
        }

        if (context.Capabilities.Has(Capability.VolumeStats))
        {
            var columns = (await Db.QueryAsync(connection, ColumnsSql, r => (Ifi: r.NullableInt(0) is not null, Memory: r.NullableInt(1) is not null), ct).ConfigureAwait(false)).FirstOrDefault();
            var services = await Db.QueryAsync(connection, BuildServicesSql(columns.Ifi),
                r => new ServiceInfo(r.String(0), r.NullableString(1), r.NullableString(2), r.NullableString(3), YesNo(r.NullableString(4))), ct).ConfigureAwait(false);
            var memoryModel = columns.Memory
                ? (await Db.QueryAsync(connection, MemoryModelSql, r => r.NullableString(0), ct).ConfigureAwait(false)).FirstOrDefault()
                : null;
            snapshot = snapshot with
            {
                Services = services,
                ServicesAvailable = true,
                InstantFileInitialization = services.FirstOrDefault(s => s.Name.StartsWith("SQL Server (", StringComparison.OrdinalIgnoreCase))?.InstantFileInitialization,
                MemoryModel = memoryModel,
            };
        }

        var options = await Db.QueryAsync(connection, context.Instance.Version.Major >= 9 ? ConfigurationCollector.Sql2005 : ConfigurationCollector.Sql2000,
            r => new ConfigurationOption(r.String(0), r.Long(1), r.Long(2)), ct).ConfigureAwait(false);
        var flags = await TraceFlagCollector.ReadGlobalFlagsAsync(connection, ct).ConfigureAwait(false);

        var items = ConfigurationFingerprint.Items(snapshot, options, flags);
        var changes = previous is null ? [] : ConfigurationFingerprint.Diff(previous.Items, items, context.Now);
        var recent = (previous?.RecentChanges ?? []).Where(c => context.Now - c.DetectedAt < ConfigurationFingerprint.RecentWindow).Concat(changes).ToList();
        return snapshot with { Items = items, Changes = changes, RecentChanges = recent };
    }

    private static string Growth(long growth, bool percent) =>
        growth == 0 ? "ingen" : percent ? $"{growth} %" : $"{(growth / 128).ToString(CultureInfo.InvariantCulture)} MB";

    private static string MaxSize(long maxSize) =>
        maxSize is -1 or 268435456 ? "ubegrænset" : $"{(maxSize / 128).ToString(CultureInfo.InvariantCulture)} MB";

    private static bool? YesNo(string? value) => value switch
    {
        "Y" or "y" => true,
        "N" or "n" => false,
        _ => null,
    };
}