using System.Diagnostics.Metrics;

namespace StellaOps.Excititor.WebService.Telemetry;

internal sealed class ChunkTelemetry
{
    private readonly Counter<long> _ingestedTotal;
    private readonly Histogram<long> _itemCount;
    private readonly Histogram<long> _payloadBytes;
    private readonly Histogram<double> _latencyMs;

    public ChunkTelemetry(IMeterFactory meterFactory)
    {
        var meter = meterFactory.Create("StellaOps.Excititor.Chunks");
        _ingestedTotal = meter.CreateCounter<long>(
            name: "vex_chunks_ingested_total",
            unit: "chunks",
            description: "Chunks submitted to Excititor VEX ingestion.");
        _itemCount = meter.CreateHistogram<long>(
            name: "vex_chunks_item_count",
            unit: "items",
            description: "Item count per submitted chunk.");
        _payloadBytes = meter.CreateHistogram<long>(
            name: "vex_chunks_payload_bytes",
            unit: "bytes",
            description: "Payload size per submitted chunk.");
        _latencyMs = meter.CreateHistogram<double>(
            name: "vex_chunks_latency_ms",
            unit: "ms",
            description: "End-to-end processing latency per chunk request.");
    }

    public void RecordIngested(string? tenant, string? source, string status, string? reason, long itemCount, long payloadBytes, double latencyMs)
    {
        var tags = new KeyValuePair<string, object?>[]
        {
            new("tenant", tenant ?? string.Empty),
            new("source", source ?? string.Empty),
            new("status", status),
            new("reason", string.IsNullOrWhiteSpace(reason) ? string.Empty : reason)
        };

        var tagSpan = tags.AsSpan();
        _ingestedTotal.Add(1, tagSpan);
        _itemCount.Record(itemCount, tagSpan);
        _payloadBytes.Record(payloadBytes, tagSpan);
        _latencyMs.Record(latencyMs, tagSpan);
    }
}