using System.Collections.Generic;
using System.Diagnostics.Metrics;

namespace StellaOps.Scanner.EntryTrace.Diagnostics;

public static class EntryTraceInstrumentation
{
    public static readonly Meter Meter = new("stellaops.scanner.entrytrace", "1.0.0");
}

public sealed class EntryTraceMetrics
{
    private readonly Counter<long> _resolutions;
    private readonly Counter<long> _unresolved;

    public EntryTraceMetrics()
    {
        _resolutions = EntryTraceInstrumentation.Meter.CreateCounter<long>(
            "entrytrace_resolutions_total",
            description: "Number of entry trace attempts by outcome.");
        _unresolved = EntryTraceInstrumentation.Meter.CreateCounter<long>(
            "entrytrace_unresolved_total",
            description: "Number of unresolved entry trace hops by reason.");
    }

    public void RecordOutcome(string imageDigest, string scanId, EntryTraceOutcome outcome)
    {
        _resolutions.Add(1, CreateTags(imageDigest, scanId, ("outcome", outcome.ToString().ToLowerInvariant())));
    }

    public void RecordUnknown(string imageDigest, string scanId, EntryTraceUnknownReason reason)
    {
        _unresolved.Add(1, CreateTags(imageDigest, scanId, ("reason", reason.ToString().ToLowerInvariant())));
    }

    private static KeyValuePair<string, object?>[] CreateTags(string imageDigest, string scanId, params (string Key, object? Value)[] extras)
    {
        var tags = new List<KeyValuePair<string, object?>>(2 + extras.Length)
        {
            new("image", imageDigest),
            new("scan.id", scanId)
        };

        foreach (var extra in extras)
        {
            tags.Add(new KeyValuePair<string, object?>(extra.Key, extra.Value));
        }

        return tags.ToArray();
    }
}