using System;
using System.Diagnostics.Metrics;

namespace StellaOps.Cli.Telemetry;

internal static class CliMetrics
{
    private static readonly Meter Meter = new("StellaOps.Cli", "1.0.0");

    private static readonly Counter<long> ScannerDownloadCounter = Meter.CreateCounter<long>("stellaops.cli.scanner.download.count");
    private static readonly Counter<long> ScannerInstallCounter = Meter.CreateCounter<long>("stellaops.cli.scanner.install.count");
    private static readonly Counter<long> ScanRunCounter = Meter.CreateCounter<long>("stellaops.cli.scan.run.count");
    private static readonly Counter<long> OfflineKitDownloadCounter = Meter.CreateCounter<long>("stellaops.cli.offline.kit.download.count");
    private static readonly Counter<long> OfflineKitImportCounter = Meter.CreateCounter<long>("stellaops.cli.offline.kit.import.count");
    private static readonly Counter<long> PolicySimulationCounter = Meter.CreateCounter<long>("stellaops.cli.policy.simulate.count");
    private static readonly Counter<long> PolicyActivationCounter = Meter.CreateCounter<long>("stellaops.cli.policy.activate.count");
    private static readonly Counter<long> SourcesDryRunCounter = Meter.CreateCounter<long>("stellaops.cli.sources.dryrun.count");
    private static readonly Counter<long> AocVerifyCounter = Meter.CreateCounter<long>("stellaops.cli.aoc.verify.count");
    private static readonly Counter<long> PolicyFindingsListCounter = Meter.CreateCounter<long>("stellaops.cli.policy.findings.list.count");
    private static readonly Counter<long> PolicyFindingsGetCounter = Meter.CreateCounter<long>("stellaops.cli.policy.findings.get.count");
    private static readonly Counter<long> PolicyFindingsExplainCounter = Meter.CreateCounter<long>("stellaops.cli.policy.findings.explain.count");
    private static readonly Histogram<double> CommandDurationHistogram = Meter.CreateHistogram<double>("stellaops.cli.command.duration.ms");

    public static void RecordScannerDownload(string channel, bool fromCache)
        => ScannerDownloadCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("channel", channel),
            new("cache", fromCache ? "hit" : "miss")
        });

    public static void RecordScannerInstall(string channel)
        => ScannerInstallCounter.Add(1, new KeyValuePair<string, object?>[] { new("channel", channel) });

    public static void RecordScanRun(string runner, int exitCode)
        => ScanRunCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("runner", runner),
            new("exit_code", exitCode)
        });

    public static void RecordOfflineKitDownload(string kind, bool fromCache)
        => OfflineKitDownloadCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("kind", string.IsNullOrWhiteSpace(kind) ? "unknown" : kind),
            new("cache", fromCache ? "hit" : "miss")
        });

    public static void RecordOfflineKitImport(string? status)
        => OfflineKitImportCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("status", string.IsNullOrWhiteSpace(status) ? "queued" : status)
        });

    public static void RecordPolicySimulation(string outcome)
        => PolicySimulationCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("outcome", string.IsNullOrWhiteSpace(outcome) ? "unknown" : outcome)
        });

    public static void RecordPolicyActivation(string outcome)
        => PolicyActivationCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("outcome", string.IsNullOrWhiteSpace(outcome) ? "unknown" : outcome)
        });

    public static void RecordSourcesDryRun(string status)
        => SourcesDryRunCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("status", string.IsNullOrWhiteSpace(status) ? "unknown" : status)
        });

    public static void RecordAocVerify(string outcome)
        => AocVerifyCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("outcome", string.IsNullOrWhiteSpace(outcome) ? "unknown" : outcome)
        });

    public static void RecordPolicyFindingsList(string outcome)
        => PolicyFindingsListCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("outcome", string.IsNullOrWhiteSpace(outcome) ? "unknown" : outcome)
        });

    public static void RecordPolicyFindingsGet(string outcome)
        => PolicyFindingsGetCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("outcome", string.IsNullOrWhiteSpace(outcome) ? "unknown" : outcome)
        });

    public static void RecordPolicyFindingsExplain(string outcome)
        => PolicyFindingsExplainCounter.Add(1, new KeyValuePair<string, object?>[]
        {
            new("outcome", string.IsNullOrWhiteSpace(outcome) ? "unknown" : outcome)
        });

    public static IDisposable MeasureCommandDuration(string command)
    {
        var start = DateTime.UtcNow;
        return new DurationScope(command, start);
    }

    private sealed class DurationScope : IDisposable
    {
        private readonly string _command;
        private readonly DateTime _start;
        private bool _disposed;

        public DurationScope(string command, DateTime start)
        {
            _command = command;
            _start = start;
        }

        public void Dispose()
        {
            if (_disposed)
            {
                return;
            }

            _disposed = true;
            var elapsed = (DateTime.UtcNow - _start).TotalMilliseconds;
            CommandDurationHistogram.Record(elapsed, new KeyValuePair<string, object?>[] { new("command", _command) });
        }
    }
}