import os from 'os';
import { gzip } from 'zlib';
import retry from 'async-retry';
import { defaultUsageReportingSignature } from 'apollo-graphql';
import { Report, ReportHeader, Trace } from 'apollo-reporting-protobuf';
import { Response, fetch, Headers } from 'apollo-server-env';
import {
  GraphQLRequestListener,
  GraphQLServerListener,
} from 'apollo-server-plugin-base';
import {
  GraphQLRequestContext,
  GraphQLServiceContext,
  GraphQLRequestContextDidResolveOperation,
  GraphQLRequestContextDidEncounterErrors,
  GraphQLRequestContextWillSendResponse,
  GraphQLRequestContextDidResolveSource,
} from 'apollo-server-types';
import { createSignatureCache, signatureCacheKey } from './signatureCache';
import {
  ApolloServerPluginUsageReportingOptions,
  SendValuesBaseOptions,
} from './options';
import { dateToProtoTimestamp, TraceTreeBuilder } from '../traceTreeBuilder';
import { makeTraceDetails } from './traceDetails';
import { GraphQLSchema, printSchema } from 'graphql';
import { computeCoreSchemaHash } from '../schemaReporting';
import type { InternalApolloServerPlugin } from '../internalPlugin';
import { OurReport } from './stats';
import { CacheScope } from 'apollo-cache-control';
import { defaultSendOperationsAsTrace } from './defaultSendOperationsAsTrace';

const reportHeaderDefaults = {
  hostname: os.hostname(),
  agentVersion: `apollo-server-core@${
    require('../../../package.json').version
  }`,
  runtimeVersion: `node ${process.version}`,
  // XXX not actually uname, but what node has easily.
  uname: `${os.platform()}, ${os.type()}, ${os.release()}, ${os.arch()})`,
};

class ReportData {
  report!: OurReport;
  readonly header: ReportHeader;
  constructor(executableSchemaId: string, graphRef: string) {
    this.header = new ReportHeader({
      ...reportHeaderDefaults,
      executableSchemaId,
      graphRef,
    });
    this.reset();
  }
  reset() {
    this.report = new OurReport(this.header);
  }
}

export function ApolloServerPluginUsageReporting<TContext>(
  options: ApolloServerPluginUsageReportingOptions<TContext> = Object.create(
    null,
  ),
): InternalApolloServerPlugin {
  let requestDidStartHandler: (
    requestContext: GraphQLRequestContext<TContext>,
  ) => GraphQLRequestListener<TContext>;
  return {
    __internal_plugin_id__() {
      return 'UsageReporting';
    },

    // We want to be able to access locals from `serverWillStart` in our `requestDidStart`, thus
    // this little hack. (Perhaps we should also allow GraphQLServerListener to contain
    // a requestDidStart?)
    requestDidStart(requestContext: GraphQLRequestContext<TContext>) {
      if (!requestDidStartHandler) {
        throw Error(
          'The usage reporting plugin has been asked to handle a request before the ' +
            'server has started. See https://github.com/apollographql/apollo-server/issues/4588 ' +
            'for more details.',
        );
      }
      return requestDidStartHandler(requestContext);
    },

    serverWillStart({
      logger: serverLogger,
      apollo,
      serverlessFramework,
    }: GraphQLServiceContext): GraphQLServerListener {
      // Use the plugin-specific logger if one is provided; otherwise the general server one.
      const logger = options.logger ?? serverLogger;
      const { key, graphRef } = apollo;
      if (!(key && graphRef)) {
        throw new Error(
          "You've enabled usage reporting via ApolloServerPluginUsageReporting, " +
            'but you also need to provide your Apollo API key and graph ref, via ' +
            'the APOLLO_KEY/APOLLO_GRAPH_REF environment ' +
            'variables or via `new ApolloServer({apollo: {key, graphRef})`.',
        );
      }

      logger.info(
        'Apollo usage reporting starting! See your graph at ' +
          `https://studio.apollographql.com/graph/${encodeURI(graphRef)}/`,
      );

      // If sendReportsImmediately is not specified, we default to true if we're running
      // with the ApolloServer designed for Lambda or similar. That's because these
      // environments aren't designed around letting us run a background task to
      // send reports later or hook into container destruction to flush buffered reports.
      const sendReportsImmediately =
        options.sendReportsImmediately ?? serverlessFramework;

      // Since calculating the signature for usage reporting is potentially an
      // expensive operation, we'll cache the signatures we generate and re-use
      // them based on repeated traces for the same `queryHash`.
      const signatureCache = createSignatureCache({ logger });

      const reportDataByExecutableSchemaId: {
        [executableSchemaId: string]: ReportData | undefined;
      } = Object.create(null);

      const overriddenExecutableSchemaId = options.overrideReportedSchema
        ? computeCoreSchemaHash(options.overrideReportedSchema)
        : undefined;

      let lastSeenExecutableSchemaToId:
        | {
            executableSchema: GraphQLSchema;
            executableSchemaId: string;
          }
        | undefined;

      let reportTimer: NodeJS.Timer | undefined;
      if (!sendReportsImmediately) {
        reportTimer = setInterval(
          () => sendAllReportsAndReportErrors(),
          options.reportIntervalMs || 10 * 1000,
        );
      }

      let graphMightSupportTraces = true;
      const sendOperationAsTrace =
        options.experimental_sendOperationAsTrace ??
        defaultSendOperationsAsTrace();
      const includeTracesContributingToStats =
        options.internal_includeTracesContributingToStats ?? false;

      let stopped = false;

      function executableSchemaIdForSchema(schema: GraphQLSchema) {
        if (lastSeenExecutableSchemaToId?.executableSchema === schema) {
          return lastSeenExecutableSchemaToId.executableSchemaId;
        }
        const id = computeCoreSchemaHash(printSchema(schema));

        // We override this variable every time we get a new schema so we cache
        // the last seen value. It is a single-entry cache.
        lastSeenExecutableSchemaToId = {
          executableSchema: schema,
          executableSchemaId: id,
        };

        return id;
      }

      const getReportData = (executableSchemaId: string): ReportData => {
        const existing = reportDataByExecutableSchemaId[executableSchemaId];
        if (existing) {
          return existing;
        }
        const reportData = new ReportData(executableSchemaId, graphRef);
        reportDataByExecutableSchemaId[executableSchemaId] = reportData;
        return reportData;
      };

      async function sendAllReportsAndReportErrors(): Promise<void> {
        await Promise.all(
          Object.keys(
            reportDataByExecutableSchemaId,
          ).map((executableSchemaId) =>
            sendReportAndReportErrors(executableSchemaId),
          ),
        );
      }

      async function sendReportAndReportErrors(
        executableSchemaId: string,
      ): Promise<void> {
        return sendReport(executableSchemaId).catch((err) => {
          // This catch block is primarily intended to catch network errors from
          // the retried request itself, which include network errors and non-2xx
          // HTTP errors.
          if (options.reportErrorFunction) {
            options.reportErrorFunction(err);
          } else {
            logger.error(err.message);
          }
        });
      }

      // Needs to be an arrow function to be confident that key is defined.
      const sendReport = async (executableSchemaId: string): Promise<void> => {
        const reportData = getReportData(executableSchemaId);
        const { report } = reportData;
        reportData.reset();

        if (Object.keys(report.tracesPerQuery).length === 0) {
          return;
        }

        // Set the report's overall end time. This is the timestamp that will be
        // associated with the summarized statistics.
        report.endTime = dateToProtoTimestamp(new Date());

        const protobufError = Report.verify(report);
        if (protobufError) {
          throw new Error(`Error encoding report: ${protobufError}`);
        }
        const message = Report.encode(report).finish();

        // Potential follow-up: we can compare message.length to
        // report.sizeEstimator.bytes and use it to "learn" if our estimation is
        // off and adjust it based on what we learn.

        if (options.debugPrintReports) {
          // In terms of verbosity, and as the name of this option suggests,
          // this message is either an "info" or a "debug" level message.
          // However, we are using `warn` here for compatibility reasons since
          // the `debugPrintReports` flag pre-dated the existence of log-levels
          // and changing this to also require `debug: true` (in addition to
          // `debugPrintReports`) just to reach the level of verbosity to
          // produce the output would be a breaking change.  The "warn" level is
          // on by default.  There is a similar theory and comment applied
          // below.
          //
          // We decode the report rather than printing the original `report`
          // so that it includes all of the pre-encoded traces.
          const decodedReport = Report.decode(message);
          logger.warn(
            `Apollo usage report: ${JSON.stringify(decodedReport.toJSON())}`,
          );
        }

        const compressed = await new Promise<Buffer>((resolve, reject) => {
          // The protobuf library gives us a Uint8Array. Node 8's zlib lets us
          // pass it directly; convert for the sake of Node 6. (No support right
          // now for Node 4, which lacks Buffer.from.)
          const messageBuffer = Buffer.from(
            message.buffer as ArrayBuffer,
            message.byteOffset,
            message.byteLength,
          );
          gzip(messageBuffer, (err, gzipResult) => {
            if (err) {
              reject(err);
            } else {
              resolve(gzipResult);
            }
          });
        });

        // Wrap fetcher with async-retry for automatic retrying
        const fetcher = options.fetcher ?? fetch;
        const response: Response = await retry(
          // Retry on network errors and 5xx HTTP
          // responses.
          async () => {
            const curResponse = await fetcher(
              (options.endpointUrl ||
                'https://usage-reporting.api.apollographql.com') +
                '/api/ingress/traces',
              {
                method: 'POST',
                headers: {
                  'user-agent': 'ApolloServerPluginUsageReporting',
                  'x-api-key': key,
                  'content-encoding': 'gzip',
                  accept: 'application/json',
                },
                body: compressed,
                agent: options.requestAgent,
              },
            );

            if (curResponse.status >= 500 && curResponse.status < 600) {
              throw new Error(
                `HTTP status ${curResponse.status}, ${
                  (await curResponse.text()) || '(no body)'
                }`,
              );
            } else {
              return curResponse;
            }
          },
          {
            retries: (options.maxAttempts || 5) - 1,
            minTimeout: options.minimumRetryDelayMs || 100,
            factor: 2,
          },
        ).catch((err: Error) => {
          throw new Error(
            `Error sending report to Apollo servers: ${err.message}`,
          );
        });

        if (response.status < 200 || response.status >= 300) {
          // Note that we don't expect to see a 3xx here because request follows
          // redirects.
          throw new Error(
            `Error sending report to Apollo servers: HTTP status ${
              response.status
            }, ${(await response.text()) || '(no body)'}`,
          );
        }

        if (
          graphMightSupportTraces &&
          response.status === 200 &&
          response.headers
            .get('content-type')
            ?.match(/^\s*application\/json\s*(?:;|$)/i)
        ) {
          const body = await response.text();
          let parsedBody;
          try {
            parsedBody = JSON.parse(body);
          } catch (e) {
            throw new Error(`Error parsing response from Apollo servers: ${e}`);
          }
          if (parsedBody.tracesIgnored === true) {
            logger.debug(
              "This graph's organization does not have access to traces; sending all " +
                'subsequent operations as traces.',
            );
            graphMightSupportTraces = false;
            // XXX We could also parse traces that are already in the current
            // report and convert them to stats if we wanted?
          }
        }
        if (options.debugPrintReports) {
          // In terms of verbosity, and as the name of this option suggests, this
          // message is either an "info" or a "debug" level message.  However,
          // we are using `warn` here for compatibility reasons since the
          // `debugPrintReports` flag pre-dated the existence of log-levels and
          // changing this to also require `debug: true` (in addition to
          // `debugPrintReports`) just to reach the level of verbosity to produce
          // the output would be a breaking change.  The "warn" level is on by
          // default.  There is a similar theory and comment applied above.
          logger.warn(`Apollo usage report: status ${response.status}`);
        }
      };

      requestDidStartHandler = ({
        logger: requestLogger,
        metrics,
        schema,
        request: { http, variables },
      }): GraphQLRequestListener<TContext> => {
        // Request specific log output should go into the `logger` from the
        // request context when it's provided.
        const logger = requestLogger ?? options.logger ?? serverLogger;
        const treeBuilder: TraceTreeBuilder = new TraceTreeBuilder({
          rewriteError: options.rewriteError,
          logger,
        });
        treeBuilder.startTiming();
        metrics.startHrTime = treeBuilder.startHrTime;
        let graphqlValidationFailure = false;
        let graphqlUnknownOperationName = false;

        if (http) {
          treeBuilder.trace.http = new Trace.HTTP({
            method:
              Trace.HTTP.Method[
                http.method as keyof typeof Trace.HTTP.Method
              ] || Trace.HTTP.Method.UNKNOWN,
            // Host and path are not used anywhere on the backend, so let's not bother
            // trying to parse request.url to get them, which is a potential
            // source of bugs because integrations have different behavior here.
            // On Node's HTTP module, request.url only includes the path
            // (see https://nodejs.org/api/http.html#http_message_url)
            // The same is true on Lambda (where we pass event.path)
            // But on environments like Cloudflare we do get a complete URL.
            host: null,
            path: null,
          });

          if (options.sendHeaders) {
            makeHTTPRequestHeaders(
              treeBuilder.trace.http,
              http.headers,
              options.sendHeaders,
            );
          }
        }

        async function shouldIncludeRequest(
          requestContext:
            | GraphQLRequestContextDidResolveOperation<TContext>
            | GraphQLRequestContextDidEncounterErrors<TContext>,
        ): Promise<void> {
          // This could be hit if we call `shouldIncludeRequest` more than once during a request.
          // such as if `didEncounterError` gets called after `didResolveOperation`.
          if (metrics.captureTraces !== undefined) return;

          if (typeof options.includeRequest !== 'function') {
            // Default case we always report
            metrics.captureTraces = true;
            return;
          }

          metrics.captureTraces = await options.includeRequest(requestContext);

          // Help the user understand they've returned an unexpected value,
          // which might be a subtle mistake.
          if (typeof metrics.captureTraces !== 'boolean') {
            logger.warn(
              "The 'includeRequest' async predicate function must return a boolean value.",
            );
            metrics.captureTraces = true;
          }
        }

        /**
         * Due to a number of exceptions in the request pipeline — which are
         * intended to preserve backwards compatible behavior with the
         * first generation of the request pipeline plugins prior to the
         * introduction of `didEncounterErrors` — we need to have this "didEnd"
         * functionality invoked from two places.  This accounts for the fact
         * that sometimes, under some special-cased error conditions,
         * `willSendResponse` is not invoked.  To zoom in on some of these cases,
         * check the `requestPipeline.ts` for `emitErrorAndThrow`.
         */
        let endDone: boolean = false;
        function didEnd(
          requestContext:
            | GraphQLRequestContextWillSendResponse<TContext>
            // Our didEncounterErrors handler only calls this function if didResolveSource.
            | (GraphQLRequestContextDidEncounterErrors<TContext> &
                GraphQLRequestContextDidResolveSource<TContext>)
            | GraphQLRequestContextDidResolveOperation<TContext>,
        ) {
          if (endDone) return;
          endDone = true;
          treeBuilder.stopTiming();

          if (metrics.captureTraces === undefined) {
            logger.warn(
              'captureTrace is undefined at the end of the request. This is a bug in ApolloServerPluginUsageReporting.',
            );
          }

          if (metrics.captureTraces === false) return;

          treeBuilder.trace.fullQueryCacheHit = !!metrics.responseCacheHit;
          treeBuilder.trace.forbiddenOperation = !!metrics.forbiddenOperation;
          treeBuilder.trace.registeredOperation = !!metrics.registeredOperation;

          if (requestContext.overallCachePolicy) {
            treeBuilder.trace.cachePolicy = new Trace.CachePolicy({
              scope:
                requestContext.overallCachePolicy.scope === CacheScope.Private
                  ? Trace.CachePolicy.Scope.PRIVATE
                  : requestContext.overallCachePolicy.scope ===
                    CacheScope.Public
                  ? Trace.CachePolicy.Scope.PUBLIC
                  : Trace.CachePolicy.Scope.UNKNOWN,
              // Convert from seconds to ns.
              maxAgeNs: requestContext.overallCachePolicy.maxAge * 1e9,
            });
          }

          // If operation resolution (parsing and validating the document followed
          // by selecting the correct operation) resulted in the population of the
          // `operationName`, we'll use that. (For anonymous operations,
          // `requestContext.operationName` is null, which we represent here as
          // the empty string.)
          //
          // If the user explicitly specified an `operationName` in their request
          // but operation resolution failed (due to parse or validation errors or
          // because there is no operation with that name in the document), we
          // still put _that_ user-supplied `operationName` in the trace. This
          // allows the error to be better understood in Studio. (We are
          // considering changing the behavior of `operationName` in these 3 error
          // cases; https://github.com/apollographql/apollo-server/pull/3465)
          const operationName =
            requestContext.operationName ||
            requestContext.request.operationName ||
            '';

          // If this was a federated operation and we're the gateway, add the query plan
          // to the trace.
          if (metrics.queryPlanTrace) {
            treeBuilder.trace.queryPlan = metrics.queryPlanTrace;
          }

          // Intentionally un-awaited so as not to block the response.  Any
          // errors will be logged, but will not manifest a user-facing error.
          // The logger in this case is a request specific logger OR the logger
          // defined by the plugin if that's unavailable.  The request-specific
          // logger is preferred since this is very much coupled directly to a
          // client-triggered action which might be more granularly tagged by
          // logging implementations.
          addTrace().catch(logger.error);

          async function addTrace(): Promise<void> {
            // Ignore traces that come in after stop().
            if (stopped) {
              return;
            }

            // Ensure that the caller of addTrace (which does not await it) is
            // not blocked. We use setImmediate rather than process.nextTick or
            // just relying on the Promise microtask queue because setImmediate
            // comes after IO, which is what we want.
            await new Promise((res) => setImmediate(res));

            const executableSchemaId =
              overriddenExecutableSchemaId ??
              executableSchemaIdForSchema(schema);

            const reportData = getReportData(executableSchemaId);
            const { report } = reportData;
            const { trace } = treeBuilder;

            let statsReportKey: string | undefined = undefined;
            if (!requestContext.document) {
              statsReportKey = `## GraphQLParseFailure\n`;
            } else if (graphqlValidationFailure) {
              statsReportKey = `## GraphQLValidationFailure\n`;
            } else if (graphqlUnknownOperationName) {
              statsReportKey = `## GraphQLUnknownOperationName\n`;
            }

            if (statsReportKey) {
              if (options.sendUnexecutableOperationDocuments) {
                trace.unexecutedOperationBody = requestContext.source;
                trace.unexecutedOperationName = operationName;
              }
            } else {
              const signature = getTraceSignature();
              statsReportKey = `# ${operationName || '-'}\n${signature}`;
            }

            const protobufError = Trace.verify(trace);
            if (protobufError) {
              throw new Error(`Error encoding trace: ${protobufError}`);
            }

            report.addTrace({
              statsReportKey,
              trace,
              asTrace:
                graphMightSupportTraces &&
                sendOperationAsTrace(trace, statsReportKey),
              includeTracesContributingToStats,
            });

            // If the buffer gets big (according to our estimate), send.
            if (
              sendReportsImmediately ||
              report.sizeEstimator.bytes >=
                (options.maxUncompressedReportSize || 4 * 1024 * 1024)
            ) {
              await sendReportAndReportErrors(executableSchemaId);
            }
          }

          function getTraceSignature(): string {
            if (!requestContext.document) {
              // This shouldn't happen: no document means parse failure, which
              // uses its own special statsReportKey.
              throw new Error('No document?');
            }

            const cacheKey = signatureCacheKey(
              requestContext.queryHash,
              operationName,
            );

            // If we didn't have the signature in the cache, we'll resort to
            // calculating it.
            const cachedSignature = signatureCache.get(cacheKey);

            if (cachedSignature) {
              return cachedSignature;
            }

            const generatedSignature = (
              options.calculateSignature || defaultUsageReportingSignature
            )(requestContext.document, operationName);

            // Note that this cache is always an in-memory cache.
            // If we replace it with a more generic async cache, we should
            // not await the write operation.
            signatureCache.set(cacheKey, generatedSignature);

            return generatedSignature;
          }
        }

        // While we start the tracing as soon as possible, we only actually report
        // traces when we have resolved the source.  This is largely because of
        // the APQ negotiation that takes place before that resolution happens.
        // This is effectively bypassing the reporting of:
        //   - PersistedQueryNotFoundError
        //   - PersistedQueryNotSupportedError
        //   - InvalidGraphQLRequestError
        let didResolveSource: boolean = false;

        return {
          didResolveSource(requestContext) {
            didResolveSource = true;

            if (metrics.persistedQueryHit) {
              treeBuilder.trace.persistedQueryHit = true;
            }
            if (metrics.persistedQueryRegister) {
              treeBuilder.trace.persistedQueryRegister = true;
            }

            if (variables) {
              treeBuilder.trace.details = makeTraceDetails(
                variables,
                options.sendVariableValues,
                requestContext.source,
              );
            }

            const clientInfo = (
              options.generateClientInfo || defaultGenerateClientInfo
            )(requestContext);
            if (clientInfo) {
              // While there is a clientAddress protobuf field, the backend
              // doesn't pay attention to it yet, so we'll ignore it for now.
              const {
                clientName,
                clientVersion,
                clientReferenceId,
              } = clientInfo;
              // the backend makes the choice of mapping clientName => clientReferenceId if
              // no custom reference id is provided
              treeBuilder.trace.clientVersion = clientVersion || '';
              treeBuilder.trace.clientReferenceId = clientReferenceId || '';
              treeBuilder.trace.clientName = clientName || '';
            }
          },
          validationDidStart() {
            return (validationErrors?: ReadonlyArray<Error>) => {
              graphqlValidationFailure = validationErrors
                ? validationErrors.length !== 0
                : false;
            };
          },
          async didResolveOperation(requestContext) {
            // If operation is undefined then `getOperationAST` returned null
            // and an unknown operation was specified.
            graphqlUnknownOperationName =
              requestContext.operation === undefined;
            await shouldIncludeRequest(requestContext);

            if (metrics.captureTraces === false) {
              // End early if we aren't going to send the trace so we continue to
              // run the tree builder.
              didEnd(requestContext);
            }
          },
          executionDidStart() {
            // If we stopped tracing early, return undefined so we don't trace
            // an object
            if (endDone) return;

            return {
              willResolveField({ info }) {
                return treeBuilder.willResolveField(info);
                // We could save the error into the trace during the end handler, but
                // it won't have all the information that graphql-js adds to it later,
                // like 'locations'.
              },
            };
          },
          willSendResponse(requestContext) {
            // shouldTraceOperation will be called before this in `didResolveOperation`
            // so we don't need to call it again here.

            // See comment above for why `didEnd` must be called in two hooks.
            didEnd(requestContext);
          },
          async didEncounterErrors(requestContext) {
            // Search above for a comment about "didResolveSource" to see which
            // of the pre-source-resolution errors we are intentionally avoiding.
            if (!didResolveSource || endDone) return;
            treeBuilder.didEncounterErrors(requestContext.errors);

            // This will exit early if we have already set metrics.captureTraces
            await shouldIncludeRequest(requestContext);

            // See comment above for why `didEnd` must be called in two hooks.
            // The type assertion is valid becaus we check didResolveSource above.
            didEnd(
              requestContext as GraphQLRequestContextDidEncounterErrors<
                TContext
              > &
                GraphQLRequestContextDidResolveSource<TContext>,
            );
          },
        };
      };

      return {
        async serverWillStop() {
          if (reportTimer) {
            clearInterval(reportTimer);
            reportTimer = undefined;
          }

          stopped = true;
          await sendAllReportsAndReportErrors();
        },
      };
    },
  };
}

export function makeHTTPRequestHeaders(
  http: Trace.IHTTP,
  headers: Headers,
  sendHeaders?: SendValuesBaseOptions,
): void {
  if (
    !sendHeaders ||
    ('none' in sendHeaders && sendHeaders.none) ||
    ('all' in sendHeaders && !sendHeaders.all)
  ) {
    return;
  }
  for (const [key, value] of headers) {
    const lowerCaseKey = key.toLowerCase();
    if (
      ('exceptNames' in sendHeaders &&
        // We assume that most users only have a few headers to hide, or will
        // just set {none: true} ; we can change this linear-time
        // operation if it causes real performance issues.
        sendHeaders.exceptNames.some((exceptHeader) => {
          // Headers are case-insensitive, and should be compared as such.
          return exceptHeader.toLowerCase() === lowerCaseKey;
        })) ||
      ('onlyNames' in sendHeaders &&
        !sendHeaders.onlyNames.some((header) => {
          return header.toLowerCase() === lowerCaseKey;
        }))
    ) {
      continue;
    }

    switch (key) {
      case 'authorization':
      case 'cookie':
      case 'set-cookie':
        break;
      default:
        http!.requestHeaders![key] = new Trace.HTTP.Values({
          value: [value],
        });
    }
  }
}

function defaultGenerateClientInfo({ request }: GraphQLRequestContext) {
  const clientNameHeaderKey = 'apollographql-client-name';
  const clientReferenceIdHeaderKey = 'apollographql-client-reference-id';
  const clientVersionHeaderKey = 'apollographql-client-version';

  // Default to using the `apollo-client-x` header fields if present.
  // If none are present, fallback on the `clientInfo` query extension
  // for backwards compatibility.
  // The default value if neither header values nor query extension is
  // set is the empty String for all fields (as per protobuf defaults)
  if (
    request.http?.headers?.get(clientNameHeaderKey) ||
    request.http?.headers?.get(clientVersionHeaderKey) ||
    request.http?.headers?.get(clientReferenceIdHeaderKey)
  ) {
    return {
      clientName: request.http?.headers?.get(clientNameHeaderKey),
      clientVersion: request.http?.headers?.get(clientVersionHeaderKey),
      clientReferenceId: request.http?.headers?.get(clientReferenceIdHeaderKey),
    };
  } else if (request.extensions?.clientInfo) {
    return request.extensions.clientInfo;
  } else {
    return {};
  }
}

// This plugin does nothing, but it ensures that ApolloServer won't try
// to add a default ApolloServerPluginUsageReporting.
export function ApolloServerPluginUsageReportingDisabled(): InternalApolloServerPlugin {
  return {
    __internal_plugin_id__() {
      return 'UsageReporting';
    },
  };
}
