using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace StellaOps.Provcache;

public sealed partial class ProvcacheService
{
    /// <inheritdoc />
    public async Task<ProvcacheMetrics> GetMetricsAsync(CancellationToken cancellationToken = default)
    {
        var stats = await _repository.GetStatisticsAsync(cancellationToken).ConfigureAwait(false);

        ProvcacheTelemetry.SetItemsCount(stats.TotalEntries);

        double avgLatency, p99Latency;
        lock (_metricsLock)
        {
            avgLatency = _latencies.Count > 0 ? _latencies.Average() : 0;
            p99Latency = _latencies.Count > 0
                ? _latencies.OrderBy(x => x).ElementAt((int)(_latencies.Count * 0.99))
                : 0;
        }

        return new ProvcacheMetrics
        {
            TotalRequests = Interlocked.Read(ref _totalRequests),
            TotalHits = Interlocked.Read(ref _totalHits),
            TotalMisses = Interlocked.Read(ref _totalMisses),
            TotalInvalidations = Interlocked.Read(ref _totalInvalidations),
            CurrentEntryCount = stats.TotalEntries,
            AvgLatencyMs = avgLatency,
            P99LatencyMs = p99Latency,
            ValkeyCacheHealthy = true, // TODO: Add health check
            PostgresRepositoryHealthy = true, // TODO: Add health check
            CollectedAt = _timeProvider.GetUtcNow()
        };
    }
}