using Fleet.Core;
using MoShiro.Backend.Analysis;
using MoShiro.Protocol;

namespace MoShiro.Backend.Application;

/// <summary>请求的指标：导出 id（<c>rtt.p95</c>）与评分 id（<c>score.mc</c>）。</summary>
public sealed record MetricSelection(IReadOnlyList<string> ExportIds, IReadOnlyList<string> ScoreModelIds)
{
    public bool WantsScores => ScoreModelIds.Count > 0;

    public IEnumerable<string> AllIds => ExportIds.Concat(ScoreModelIds.Select(m => "score." + m));

    public static Result<MetricSelection> Resolve(string? metrics, string? presets, int maxMetrics)
    {
        var ids = new List<string>();
        if (presets is not null)
        {
            foreach (string presetId in presets.Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries))
            {
                PresetDef? preset = MetricRegistry.FindPreset(presetId);
                if (preset is null)
                {
                    return Result<MetricSelection>.Fail(MoShiroErrors.UnknownPreset, $"unknown preset {presetId}");
                }

                ids.AddRange(preset.MetricIds);
            }
        }

        if (metrics is not null)
        {
            ids.AddRange(metrics.Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries));
        }

        ids = [.. ids.Distinct(StringComparer.Ordinal)];
        if (ids.Count > maxMetrics)
        {
            return Result<MetricSelection>.Fail(MoShiroErrors.TooManyMetrics, $"at most {maxMetrics} metrics per request");
        }

        var exports = new List<string>();
        var scores = new List<string>();
        foreach (string id in ids)
        {
            if (id.StartsWith("score.", StringComparison.Ordinal))
            {
                string model = id["score.".Length..];
                if (ModelRegistry.Find(model) is null)
                {
                    return Result<MetricSelection>.Fail(MoShiroErrors.UnknownMetric, $"unknown metric {id}");
                }

                scores.Add(model);
            }
            else if (MetricRegistry.TryFindExport(id, out _, out _))
            {
                exports.Add(id);
            }
            else
            {
                return Result<MetricSelection>.Fail(MoShiroErrors.UnknownMetric, $"unknown metric {id}");
            }
        }

        return Result<MetricSelection>.Ok(new MetricSelection(exports, scores));
    }
}

public static class ExportEvaluator
{
    /// <summary>导出指定的值；没有样本的指标不出现在结果里。</summary>
    public static Dictionary<string, double> Evaluate(MetricSet set, IEnumerable<string> exportIds, double durationSeconds)
    {
        var values = new Dictionary<string, double>(StringComparer.Ordinal);
        foreach (string id in exportIds)
        {
            if (MetricRegistry.TryFindExport(id, out MetricDef def, out MetricExport export)
                && set.TryGet(def.Id, out Accumulator acc)
                && MetricDef.Export(acc, export, durationSeconds) is { } value
                && double.IsFinite(value))
            {
                values[id] = value;
            }
        }

        return values;
    }

    public static IEnumerable<string> AllExportIds() => MetricRegistry.AllExports().Select(e => e.Export.Id);
}