// OpenTelemetry bootstrap: sends traces, metrics and logs to the LGTM
// stack's OTLP/HTTP collector at http://localhost:4318. Must be required
// before any other module so auto-instrumentation can patch http/express/pg.
const { NodeSDK } = require('@opentelemetry/sdk-node')
const { getNodeAutoInstrumentations } = require('@opentelemetry/auto-instrumentations-node')
const { OTLPTraceExporter } = require('@opentelemetry/exporter-trace-otlp-http')
const { OTLPMetricExporter } = require('@opentelemetry/exporter-metrics-otlp-http')
const { OTLPLogExporter } = require('@opentelemetry/exporter-logs-otlp-http')
const { PeriodicExportingMetricReader } = require('@opentelemetry/sdk-metrics')
const { BatchLogRecordProcessor } = require('@opentelemetry/sdk-logs')
const { resourceFromAttributes } = require('@opentelemetry/resources')
const { ATTR_SERVICE_NAME, ATTR_SERVICE_VERSION } = require('@opentelemetry/semantic-conventions')
const { logs } = require('@opentelemetry/api-logs')

const endpoint = process.env.OTEL_EXPORTER_OTLP_ENDPOINT || 'http://localhost:4318'

const resource = resourceFromAttributes({
  [ATTR_SERVICE_NAME]: 'hn-reader-api',
  [ATTR_SERVICE_VERSION]: '1.0.0',
})

const sdk = new NodeSDK({
  resource,
  traceExporter: new OTLPTraceExporter({ url: `${endpoint}/v1/traces` }),
  metricReader: new PeriodicExportingMetricReader({
    exporter: new OTLPMetricExporter({ url: `${endpoint}/v1/metrics` }),
    exportIntervalMillis: 15000,
  }),
  logRecordProcessors: [
    new BatchLogRecordProcessor(new OTLPLogExporter({ url: `${endpoint}/v1/logs` })),
  ],
  instrumentations: [
    getNodeAutoInstrumentations({
      '@opentelemetry/instrumentation-fs': { enabled: false },
    }),
  ],
})

sdk.start()

process.on('SIGTERM', () => sdk.shutdown().finally(() => process.exit(0)))

const otelLogger = logs.getLogger('hn-reader-api')

// Small structured logger: prints to stdout (captured by journald) and
// emits an OTLP log record so logs show up alongside traces in Grafana.
function log(severity, message, attributes = {}) {
  const line = `[${severity}] ${message} ${Object.keys(attributes).length ? JSON.stringify(attributes) : ''}`
  if (severity === 'ERROR') console.error(line)
  else console.log(line)

  otelLogger.emit({
    severityText: severity,
    body: message,
    attributes,
  })
}

module.exports = { log }