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

namespace SQLInsight.Collectors.Instance;

/// <summary>
/// SQL Agent jobs from msdb. Uses only the tables granted by the least-privilege script (no msdb functions, which
/// would need EXECUTE); run_date/run_time integers are converted here.
/// </summary>
public sealed class AgentJobCollector : Collector<AgentJobSnapshot>
{
    internal const string RunningSql = "SELECT COUNT(*) FROM sys.dm_exec_sessions WHERE program_name LIKE N'SQLAgent - %'";

    internal const string JobsSql = """
        DECLARE @since int;
        SET @since = CONVERT(int, CONVERT(char(8), DATEADD(day, -1, GETDATE()), 112));
        SELECT j.name, j.enabled, last_run.run_status, last_run.run_date, last_run.run_time,
               failed_step.step_name, LEFT(failed_step.message, 2000), failures.n
        FROM msdb.dbo.sysjobs j
        OUTER APPLY (SELECT TOP (1) h.run_status, h.run_date, h.run_time FROM msdb.dbo.sysjobhistory h
                     WHERE h.job_id = j.job_id AND h.step_id = 0 ORDER BY h.instance_id DESC) last_run
        OUTER APPLY (SELECT TOP (1) h.step_name, h.message FROM msdb.dbo.sysjobhistory h
                     WHERE h.job_id = j.job_id AND h.step_id > 0 AND h.run_status = 0 ORDER BY h.instance_id DESC) failed_step
        OUTER APPLY (SELECT COUNT(*) AS n FROM msdb.dbo.sysjobhistory h
                     WHERE h.job_id = j.job_id AND h.step_id = 0 AND h.run_status = 0 AND h.run_date >= @since) failures
        """;

    public override string Name => "agent-jobs";
    public override TimeSpan DefaultInterval => TimeSpan.FromMinutes(5);
    public override IReadOnlyCollection<Capability> RequiredCapabilities => [Capability.DynamicManagementViews];

    protected override async Task<AgentJobSnapshot> CollectAsync(CollectorContext context, AgentJobSnapshot? previous)
    {
        var ct = context.CancellationToken;
        var sessions = await Db.QueryAsync(context.Connection, RunningSql, r => r.Int(0), ct).ConfigureAwait(false);
        var jobs = await Db.QueryAsync(context.Connection, JobsSql, r => new AgentJob
        {
            Name = r.String(0),
            IsEnabled = r.Bool(1),
            LastRunStatus = r.NullableInt(2),
            LastRunAt = r.IsNull(3) ? null : ToDateTime(r.Int(3), r.Int(4)),
            LastFailedStepName = r.NullableString(5),
            LastFailedStepMessage = r.NullableString(6),
            FailuresLastDay = r.NullableInt(7) ?? 0,
        }, ct).ConfigureAwait(false);

        return new AgentJobSnapshot { CapturedAt = context.Now, IsAgentRunning = sessions[0] > 0, Jobs = jobs };
    }

    /// <summary>msdb stores 2026-09-29 13:05:07 as run_date 20260929 and run_time 130507 (server local time).</summary>
    internal static DateTime? ToDateTime(int runDate, int runTime) =>
        DateTime.TryParseExact(
            runDate.ToString("00000000", CultureInfo.InvariantCulture) + runTime.ToString("000000", CultureInfo.InvariantCulture),
            "yyyyMMddHHmmss", CultureInfo.InvariantCulture, DateTimeStyles.None, out var value)
            ? value
            : null;
}