import os from 'os';
import type { InternalApolloServerPlugin } from '../../internalPlugin';
import { v4 as uuidv4 } from 'uuid';
import { printSchema, validateSchema, buildSchema } from 'graphql';
import type { fetch } from 'apollo-server-env';
import { SchemaReporter } from './schemaReporter';
import createSHA from '../../utils/createSHA';
import { schemaIsFederated } from '../schemaIsFederated';
import type { SchemaReport } from './generated/operations';

export interface ApolloServerPluginSchemaReportingOptions {
  /**
   * The schema reporter waits before starting reporting.
   * By default, the report waits some random amount of time between 0 and 10 seconds.
   * A longer interval leads to more staggered starts which means it is less likely
   * multiple servers will get asked to upload the same schema.
   *
   * If this server runs in lambda or in other constrained environments it would be useful
   * to decrease the schema reporting max wait time to be less than default.
   *
   * This number will be the max for the range in ms that the schema reporter will
   * wait before starting to report.
   */
  initialDelayMaxMs?: number;
  /**
   * Override the reported schema that is reported to the Apollo registry. This
   * schema does not go through any normalizations and the string is directly
   * sent to the Apollo registry. This can be useful for comments or other
   * ordering and whitespace changes that get stripped when generating a
   * `GraphQLSchema`.
   *
   * **If you pass this option to this plugin, you should explicitly configure
   * `ApolloServerPluginUsageReporting` and pass the same value to its
   * `overrideReportedSchema` option.** This ensures that the schema ID
   * associated with requests reported by the usage reporting plugin matches the
   * schema ID that this plugin reports. For example:
   *
   * ```js
   * new ApolloServer({
   *   plugins: [
   *     ApolloServerPluginSchemaReporting({overrideReportedSchema: schema}),
   *     ApolloServerPluginUsageReporting({overrideReportedSchema: schema}),
   *   ],
   * })
   * ```
   */
  overrideReportedSchema?: string;
  /**
   * The URL to use for reporting schemas. Primarily for testing and internal
   * Apollo use.
   */
  endpointUrl?: string;
  /**
   * Specifies which Fetch API implementation to use when reporting schemas.
   */
  fetcher?: typeof fetch;
}

export function ApolloServerPluginSchemaReporting(
  {
    initialDelayMaxMs,
    overrideReportedSchema,
    endpointUrl,
    fetcher,
  }: ApolloServerPluginSchemaReportingOptions = Object.create(null),
): InternalApolloServerPlugin {
  const bootId = uuidv4();

  return {
    __internal_plugin_id__() {
      return 'SchemaReporting';
    },
    async serverWillStart({ apollo, schema, logger }) {
      const { key, graphRef } = apollo;
      if (!key) {
        throw Error(
          'To use ApolloServerPluginSchemaReporting, you must provide an Apollo API ' +
            'key, via the APOLLO_KEY environment variable or via `new ApolloServer({apollo: {key})`',
        );
      }
      if (!graphRef) {
        // This error is a bit imprecise as you can also specify ID and variant separately,
        // or rely on API-key parsing (before AS3), but this is "best practices".
        throw Error(
          'To use ApolloServerPluginSchemaReporting, you must provide your graph ref (eg, ' +
            "'my-graph-id@my-graph-variant'). Try setting the APOLLO_GRAPH_REF environment " +
            'variable or passing `new ApolloServer({apollo: {graphRef}})`.',
        );
      }

      // Ensure a provided override schema can be parsed and validated
      if (overrideReportedSchema) {
        try {
          const validationErrors = validateSchema(
            buildSchema(overrideReportedSchema, { noLocation: true }),
          );
          if (validationErrors.length) {
            throw new Error(
              validationErrors.map((error) => error.message).join('\n'),
            );
          }
        } catch (err) {
          throw new Error(
            'The schema provided to overrideReportedSchema failed to parse or ' +
              `validate: ${(err as Error).message}`,
          );
        }
      }

      if (schemaIsFederated(schema)) {
        throw Error(
          [
            'Schema reporting is not yet compatible with federated services.',
            "If you're interested in using schema reporting with federated",
            'services, please contact Apollo support. To set up managed federation, see',
            'https://go.apollo.dev/s/managed-federation',
          ].join(' '),
        );
      }

      if (endpointUrl !== undefined) {
        logger.info(
          `Apollo schema reporting: schema reporting URL override: ${endpointUrl}`,
        );
      }

      const baseSchemaReport: Omit<SchemaReport, 'coreSchemaHash'> = {
        bootId,
        graphRef,
        // The infra environment in which this edge server is running, e.g. localhost, Kubernetes
        // Length must be <= 256 characters.
        platform: process.env.APOLLO_SERVER_PLATFORM || 'local',
        runtimeVersion: `node ${process.version}`,
        // An identifier used to distinguish the version of the server code such as git or docker sha.
        // Length must be <= 256 characters
        userVersion: process.env.APOLLO_SERVER_USER_VERSION,
        // "An identifier for the server instance. Length must be <= 256 characters.
        serverId:
          process.env.APOLLO_SERVER_ID || process.env.HOSTNAME || os.hostname(),
        libraryVersion: `apollo-server-core@${
          require('../../../package.json').version
        }`,
      };
      let currentSchemaReporter: SchemaReporter | undefined;

      return {
        schemaDidLoadOrUpdate({ apiSchema, coreSupergraphSdl }): void {
          if (overrideReportedSchema !== undefined) {
            if (currentSchemaReporter) {
              // When the schema to report has been overridden, there is no need
              // to create a new schema reporter.
              return;
            } else {
              logger.info(
                'Apollo schema reporting: schema to report has been overridden',
              );
            }
          }

          const coreSchema =
            overrideReportedSchema ??
            coreSupergraphSdl ??
            printSchema(apiSchema);
          const coreSchemaHash = computeCoreSchemaHash(coreSchema);
          const schemaReport: SchemaReport = {
            ...baseSchemaReport,
            coreSchemaHash,
          };

          currentSchemaReporter?.stop();
          currentSchemaReporter = new SchemaReporter({
            schemaReport,
            coreSchema,
            apiKey: key,
            endpointUrl,
            logger,
            // Jitter the startup between 0 and 10 seconds
            initialReportingDelayInMs: Math.floor(
              Math.random() * (initialDelayMaxMs ?? 10_000),
            ),
            fallbackReportingDelayInMs: 20_000,
            fetcher,
          });
          currentSchemaReporter.start();

          logger.info(
            'Apollo schema reporting: reporting a new schema to Studio! See your graph at ' +
              `https://studio.apollographql.com/graph/${encodeURI(
                graphRef,
              )}/ with server info ${JSON.stringify(schemaReport)}`,
          );
        },
        async serverWillStop() {
          currentSchemaReporter?.stop();
        },
      };
    },
  };
}

export function computeCoreSchemaHash(schema: string): string {
  return createSHA('sha256').update(schema).digest('hex');
}