// OpenTelemetry tracing and logging initialization for the gibbz backend.
// Loaded before HTTP / network modules start serving traffic.
import process from 'node:process';
import { NodeSDK } from '@opentelemetry/sdk-node';
import { getNodeAutoInstrumentations } from '@opentelemetry/auto-instrumentations-node';
import { OTLPTraceExporter } from '@opentelemetry/exporter-trace-otlp-http';
import { OTLPLogExporter } from '@opentelemetry/exporter-logs-otlp-http';
import { BatchLogRecordProcessor } from '@opentelemetry/sdk-logs';
import { resourceFromAttributes } from '@opentelemetry/resources';
import { ATTR_SERVICE_NAME, ATTR_SERVICE_VERSION } from '@opentelemetry/semantic-conventions';

export class Tracing {
  private sdk: NodeSDK | undefined;

  start(
    env: Record<string, string | undefined> = process.env,
    onFatal?: (err: unknown) => void,
  ): void {
    const serviceName = env.OTEL_SERVICE_NAME || 'gibbz';
    const serviceRelease = env.SERVICE_RELEASE || env.OTEL_SERVICE_RELEASE || env.APP_RELEASE || 'dev';
    const environment = env.ENVIRONMENT || env.NODE_ENV || 'production';
    const otelUrl = (env.OTEL_EXPORTER_OTLP_ENDPOINT || env.OTEL_URL || 'https://otel.k6n.net').replace(/\/+$/, '');
    const ingestKey = env.OTEL_INGEST_KEY || '';

    const headers: Record<string, string> = {};
    if (ingestKey) headers['X-Otel-Ingest-Key'] = ingestKey;

    const resource = resourceFromAttributes({
      [ATTR_SERVICE_NAME]: serviceName,
      [ATTR_SERVICE_VERSION]: serviceRelease,
      'service.release': serviceRelease,
      'service.environment': environment,
    });

    const sdk = new NodeSDK({
      resource,
      traceExporter: new OTLPTraceExporter({ url: `${otelUrl}/v1/traces`, headers }),
      logRecordProcessor: new BatchLogRecordProcessor({
        exporter: new OTLPLogExporter({ url: `${otelUrl}/v1/logs`, headers }),
      }),
      instrumentations: [
        getNodeAutoInstrumentations({
          '@opentelemetry/instrumentation-fs': { enabled: false },
        }),
      ],
    });
    this.sdk = sdk;

    try {
      sdk.start();
      console.log(
        `[otel] Initialized OpenTelemetry for ${serviceName} (release: ${serviceRelease}, env: ${environment}) -> ${otelUrl}`,
      );
    } catch (err) {
      console.error('[otel] Failed to start OpenTelemetry SDK:', err);
      onFatal?.(err);
    }

    process.on('SIGTERM', () => {
      this.shutdown()
        .then(() => {
          console.log('[otel] SDK shut down successfully');
          process.exit(0);
        })
        .catch((err) => {
          console.error('[otel] Error shutting down SDK', err);
          process.exit(0);
        });
    });
  }

  async shutdown(): Promise<void> {
    await this.sdk?.shutdown();
  }
}