using Dapper;
using Kbx.Shared.Experiments.Generated;
using Npgsql;
namespace Kbx.Shared.Experiments;
public sealed class KbxExperimentOverviewQuery(NpgsqlDataSource dataSource)
{
    public async Task<KbxExperimentOverviewResponse> ExecuteAsync(Guid tenantId,CancellationToken ct)
    {
        await using var connection=await dataSource.OpenConnectionAsync(ct);var items=new List<KbxExperimentOverviewRow>();
        foreach(var def in KbxExperimentCatalog.Experiments.Values)
        {
            var runtime=await connection.QuerySingleOrDefaultAsync<RuntimeRow>(new CommandDefinition("select state State,rollout_percent RolloutPercent,kill_switch KillSwitch,updated_at UpdatedAt from kbx.experiment_runtime where tenant_id=@TenantId and experiment_id=@Id",new{TenantId=tenantId,Id=def.Id},cancellationToken:ct));
            var since=runtime?.UpdatedAt ?? DateTimeOffset.UtcNow.AddDays(-30);
            var metrics=(await connection.QueryAsync<MetricRow>(new CommandDefinition("""
              select experiment_variant Variant,
                     count(*) filter(where event_name='experiment.exposed') Exposures,
                     count(*) filter(where event_name='task.complete') TaskCompletions,
                     count(*) filter(where event_name='interaction.execute') Interactions,
                     count(*) filter(where event_name='command.execute') Commands,
                     count(*) filter(where event_name='validation.failed') ValidationFailures,
                     percentile_cont(0.95) within group(order by duration_ms) filter(where event_name='task.complete' and duration_ms is not null) TaskP95
                from kbx.ux_events where tenant_id=@TenantId and experiment_id=@Id and occurred_at>=@Since
               group by experiment_variant;
            """,new{TenantId=tenantId,Id=def.Id,Since=since},cancellationToken:ct))).Select(x=>new KbxExperimentVariantMetric(x.Variant,x.Exposures,x.TaskCompletions,x.TaskCompletions==0?null:Math.Round((double)x.Interactions/x.TaskCompletions,2),x.TaskP95,x.Commands==0?null:Math.Round((double)x.ValidationFailures*100d/x.Commands,2))).ToArray();
            var state=runtime?.State??def.State;var decision=Decide(def,state,runtime?.KillSwitch??false,metrics);
            items.Add(new(def.Id,def.ScreenId,state,runtime?.RolloutPercent??def.RolloutPercent,runtime?.KillSwitch??false,decision,metrics,runtime?.UpdatedAt));
        }
        return new(items);
    }
    private static string Decide(KbxExperimentDefinition def,string state,bool killed,IReadOnlyList<KbxExperimentVariantMetric> rows)
    {
        if(killed||state=="rolled-back")return "rolled-back";var control=rows.FirstOrDefault(x=>x.Variant=="control"),treatment=rows.FirstOrDefault(x=>x.Variant!="control");
        if(control is null||treatment is null||control.Exposures<def.MinExposurePerVariant||treatment.Exposures<def.MinExposurePerVariant)return "inconclusive";
        if(control.TaskCompletionP95Ms is >0 && treatment.TaskCompletionP95Ms>control.TaskCompletionP95Ms*1.20)return "guardrail-breach";
        if(control.ValidationFailureRate is not null&&treatment.ValidationFailureRate>control.ValidationFailureRate+2)return "guardrail-breach";
        if(control.InteractionsPerTask is >0&&treatment.InteractionsPerTask<=control.InteractionsPerTask*(1-def.MinimumImprovementPercent/100d))return "candidate";
        return "neutral";
    }
    private sealed record RuntimeRow(string State,int RolloutPercent,bool KillSwitch,DateTimeOffset UpdatedAt);
    private sealed record MetricRow(string Variant,long Exposures,long TaskCompletions,long Interactions,long Commands,long ValidationFailures,double? TaskP95);
}