import * as plugins from '../../plugins.js';
import type { ICommandHandler, IHandlerContext } from '../CommandRouter.js';

/**
 * HelloHandler - Handles hello/isMaster handshake commands
 *
 * This is the first command sent by MongoDB drivers to establish a connection.
 * It returns server capabilities and configuration.
 */
export class HelloHandler implements ICommandHandler {
  async handle(context: IHandlerContext): Promise<plugins.bson.Document> {
    const { command, server } = context;

    // Build response with server capabilities
    const response: plugins.bson.Document = {
      ismaster: true,
      ok: 1,

      // Maximum sizes
      maxBsonObjectSize: 16777216,           // 16 MB
      maxMessageSizeBytes: 48000000,         // 48 MB
      maxWriteBatchSize: 100000,             // 100k documents per batch

      // Timestamps
      localTime: new Date(),

      // Session support
      logicalSessionTimeoutMinutes: 30,

      // Connection info
      connectionId: 1,

      // Wire protocol versions (support MongoDB 3.6 through 7.0)
      minWireVersion: 0,
      maxWireVersion: 21,

      // Server mode
      readOnly: false,

      // Topology info (standalone mode)
      isWritablePrimary: true,

      // Additional info
      topologyVersion: {
        processId: new plugins.bson.ObjectId(),
        counter: plugins.bson.Long.fromNumber(0),
      },
    };

    // Handle hello-specific fields
    if (command.hello || command.hello === 1) {
      response.helloOk = true;
    }

    // Handle client metadata
    if (command.client) {
      // Client is providing metadata about itself
      // We just acknowledge it - no need to do anything special
    }

    // Handle SASL mechanisms query
    if (command.saslSupportedMechs) {
      response.saslSupportedMechs = [
        // We don't actually support auth, but the driver needs to see this
      ];
    }

    // Compression support (none for now)
    if (command.compression) {
      response.compression = [];
    }

    // Server version info
    response.version = '7.0.0';

    return response;
  }
}