import { VERSION } from '@opentelemetry/core';
import { InstrumentationBase, InstrumentationNodeModuleDefinition } from '@opentelemetry/instrumentation';
import { vercelWaitUntil, logger, flush } from '@sentry/core';
import { DEBUG_BUILD } from '../../debug-build.js';
import { stealthWrap } from './utils.js';

// The reason this "before OTEL" integration even exists is due to timing reasons. We need to be able to register a
// `res.on('close')` handler **after** OTEL registers its own handler (which it uses to end spans), so that we can do
// something (ie. flush) after OTEL has ended a span for a request. If you think about it like an onion:
//
// (Sentry after OTEL instrumentation
//   (OTEL instrumentation
//     (Sentry before OTEL instrumentation
//       (orig HTTP request handler))))
//
// registering an instrumentation before OTEL allows us to do this for incoming requests.

/**
 * A Sentry specific http instrumentation that is applied before the otel instrumentation.
 */
class SentryHttpInstrumentationBeforeOtel extends InstrumentationBase {
   constructor() {
    super('@sentry/instrumentation-http-before-otel', VERSION, {});
  }

  // eslint-disable-next-line jsdoc/require-jsdoc
   init() {
    return [this._getHttpsInstrumentation(), this._getHttpInstrumentation()];
  }

  /** Get the instrumentation for the http module. */
   _getHttpInstrumentation() {
    return new InstrumentationNodeModuleDefinition('http', ['*'], (moduleExports) => {
      // Patch incoming requests
      stealthWrap(moduleExports.Server.prototype, 'emit', this._getPatchIncomingRequestFunction());

      return moduleExports;
    });
  }

  /** Get the instrumentation for the https module. */
   _getHttpsInstrumentation() {
    return new InstrumentationNodeModuleDefinition('https', ['*'], (moduleExports) => {
      // Patch incoming requests
      stealthWrap(moduleExports.Server.prototype, 'emit', this._getPatchIncomingRequestFunction());

      return moduleExports;
    });
  }

  /**
   * Patch the incoming request function for request isolation.
   */
   _getPatchIncomingRequestFunction()

 {
    return (
      original,
    ) => {
      return function incomingRequest( ...args) {
        // Only traces request events
        if (args[0] !== 'request') {
          return original.apply(this, args);
        }

        const response = args[1] ;

        patchResponseToFlushOnServerlessPlatforms(response);

        return original.apply(this, args);
      };
    };
  }
}

function patchResponseToFlushOnServerlessPlatforms(res) {
  // Freely extend this function with other platforms if necessary
  if (process.env.VERCEL) {
    // In some cases res.end does not seem to be defined leading to errors if passed to Proxy
    // https://github.com/getsentry/sentry-javascript/issues/15759
    if (typeof res.end === 'function') {
      let markOnEndDone = () => undefined;
      const onEndDonePromise = new Promise(res => {
        markOnEndDone = res;
      });

      res.on('close', () => {
        markOnEndDone();
      });

      // eslint-disable-next-line @typescript-eslint/unbound-method
      res.end = new Proxy(res.end, {
        apply(target, thisArg, argArray) {
          vercelWaitUntil(
            new Promise(finishWaitUntil => {
              // Define a timeout that unblocks the lambda just to be safe so we're not indefinitely keeping it alive, exploding server bills
              const timeout = setTimeout(() => {
                finishWaitUntil();
              }, 2000);

              onEndDonePromise
                .then(() => {
                  DEBUG_BUILD && logger.log('Flushing events before Vercel Lambda freeze');
                  return flush(2000);
                })
                .then(
                  () => {
                    clearTimeout(timeout);
                    finishWaitUntil();
                  },
                  e => {
                    clearTimeout(timeout);
                    DEBUG_BUILD && logger.log('Error while flushing events for Vercel:\n', e);
                    finishWaitUntil();
                  },
                );
            }),
          );

          return target.apply(thisArg, argArray);
        },
      });
    }
  }
}

export { SentryHttpInstrumentationBeforeOtel };
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