How to use graphql-query-complexity - 5 common examples

function generateAndVisitComplexMethod(maximumComplexity: number): ValidationContext {
      const query = /* graphql */ `
        query {
          sampleQuery {
            complexResolverMethod
          }
        }
      `;
      const ast = parse(query);
      const typeInfo = new TypeInfo(schema);
      const context = new ValidationContext(schema, ast, typeInfo);
      const visitor = new ComplexityVisitor(context, {
        maximumComplexity,
        estimators: [fieldExtensionsEstimator(), simpleEstimator({ defaultComplexity: 1 })],
      });
      visit(ast, visitWithTypeInfo(typeInfo, visitor));
      return context;
    }

import { ApolloServer } from 'apollo-server-express';
import { GraphQLError } from 'graphql';
import depthLimit from 'graphql-depth-limit';
import queryComplexity, {
  simpleEstimator,
} from 'graphql-query-complexity';
import schema from './schema';
import { NODE_ENV, CUSTOM_ENV } from './config/config';

const queryComplexityRule = queryComplexity({
  maximumComplexity: 1000,
  variables: {},
  // eslint-disable-next-line no-console
  createError: (max: number, actual: number) => new GraphQLError(`Query is too complex: ${actual}. Maximum allowed complexity: ${max}`),
  estimators: [
    simpleEstimator({
      defaultComplexity: 1,
    }),
  ],
});


const apolloServer = new ApolloServer({
  schema,
  introspection: NODE_ENV !== 'production' && CUSTOM_ENV !== 'production',
  validationRules: [depthLimit(7), queryComplexityRule],

didResolveOperation({ request, document }: any) {
      const complexity = getComplexity({
        schema,
        query: request.operationName
          ? separateOperations(document)[request.operationName]
          : document,
        variables: request.variables,
        estimators: [fieldConfigEstimator(), simpleEstimator({ defaultComplexity: 1 })],
      })

      if (complexity >= config.server.maxQueryComplexity) {
        throw new Error(
          `Query is too complex: ${complexity}. Maximum allowed complexity: ${config.server.maxQueryComplexity}`
        )
      }

      // This condition will prevent our console from being spammed by apollo playground introspection queries
      if (request.operationName !== 'IntrospectionQuery') {

didResolveOperation({ request, document }) {
            /**
             * This provides GraphQL query analysis to be able to react on complex queries to your GraphQL server.
             * This can be used to protect your GraphQL servers against resource exhaustion and DoS attacks.
             * More documentation can be found at https://github.com/ivome/graphql-query-complexity.
             */
            const complexity = getComplexity({
              // Our built schema
              schema,
              // To calculate query complexity properly,
              // we have to check if the document contains multiple operations
              // and eventually extract it operation from the whole query document.
              query: request.operationName
                ? separateOperations(document)[request.operationName]
                : document,
              // The variables for our GraphQL query
              variables: request.variables,
              // Add any number of estimators. The estimators are invoked in order, the first
              // numeric value that is being returned by an estimator is used as the field complexity.
              // If no estimator returns a value, an exception is raised.
              estimators: [
                // Using fieldExtensionsEstimator is mandatory to make it work with type-graphql.
                fieldExtensionsEstimator(),

didResolveOperation({ request, document }) {
            const complexity = getComplexity({
              schema,
              query: request.operationName
                ? separateOperations(document)[request.operationName]
                : document,
              variables: request.variables,
              estimators: [
                (args) => {
                  if (args.field.complexity !== undefined) {
                    if (isFunction(args.field.complexity)) {
                      return args.field.complexity(args);
                    } else {
                      return args.field.complexity;
                    }
                  }
                },
                simpleEstimator({ defaultComplexity: 1 }),