/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */

import type { IRouter, Logger } from '@kbn/core/server';
import { streamFactory } from '@kbn/ml-response-stream/server';

import { simpleStringStreamRequestBodySchema } from './schemas/simple_string_stream';
import { RESPONSE_STREAM_API_ENDPOINT } from '../../common/api';

function timeout(ms: number) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

export const defineSimpleStringStreamRoute = (router: IRouter, logger: Logger) => {
  router.versioned
    .post({
      path: RESPONSE_STREAM_API_ENDPOINT.SIMPLE_STRING_STREAM,
      access: 'internal',
    })
    .addVersion(
      {
        version: '1',
        validate: {
          request: {
            body: simpleStringStreamRequestBodySchema,
          },
        },
      },
      async (context, request, response) => {
        const maxTimeoutMs = request.body.timeout ?? 250;

        let shouldStop = false;
        request.events.aborted$.subscribe(() => {
          shouldStop = true;
        });
        request.events.completed$.subscribe(() => {
          shouldStop = true;
        });

        const { end, push, responseWithHeaders } = streamFactory(
          request.headers,
          logger,
          request.body.compressResponse
        );

        const text =
          'Elasticsearch is a search engine based on the Lucene library. It provides a distributed, multitenant-capable full-text search engine with an HTTP web interface and schema-free JSON documents. Elasticsearch is developed in Java and is dual-licensed under the source-available Server Side Public License and the Elastic license, while other parts fall under the proprietary (source-available) Elastic License. Official clients are available in Java, .NET (C#), PHP, Python, Apache Groovy, Ruby and many other languages. According to the DB-Engines ranking, Elasticsearch is the most popular enterprise search engine.';

        const tokens = text.split(' ');

        async function pushStreamUpdate() {
          try {
            if (shouldStop) {
              end();
              return;
            }

            const token = tokens.shift();

            if (token !== undefined) {
              push(`${token} `);
              await timeout(Math.floor(Math.random() * maxTimeoutMs));

              if (!shouldStop) {
                void pushStreamUpdate();
              }
            } else {
              end();
            }
          } catch (e) {
            logger.error(`There was an error: ${e.toString()}`);
          }
        }

        // do not call this using `await` so it will run asynchronously while we return the stream already.
        void pushStreamUpdate();

        return response.ok(responseWithHeaders);
      }
    );
};