import type { ObjectId } from '../bson';
import {
  CONNECTION_CHECK_OUT_FAILED,
  CONNECTION_CHECK_OUT_STARTED,
  CONNECTION_CHECKED_IN,
  CONNECTION_CHECKED_OUT,
  CONNECTION_CLOSED,
  CONNECTION_CREATED,
  CONNECTION_POOL_CLEARED,
  CONNECTION_POOL_CLOSED,
  CONNECTION_POOL_CREATED,
  CONNECTION_POOL_READY,
  CONNECTION_READY
} from '../constants';
import type { MongoError } from '../error';
import { now } from '../utils';
import type { Connection } from './connection';
import type { ConnectionPool, ConnectionPoolOptions } from './connection_pool';

/**
 * The base export class for all monitoring events published from the connection pool
 * @public
 * @category Event
 */
export abstract class ConnectionPoolMonitoringEvent {
  /** A timestamp when the event was created  */
  time: Date;
  /** The address (host/port pair) of the pool */
  address: string;
  /** @internal */
  abstract name:
    | typeof CONNECTION_CHECK_OUT_FAILED
    | typeof CONNECTION_CHECK_OUT_STARTED
    | typeof CONNECTION_CHECKED_IN
    | typeof CONNECTION_CHECKED_OUT
    | typeof CONNECTION_CLOSED
    | typeof CONNECTION_CREATED
    | typeof CONNECTION_POOL_CLEARED
    | typeof CONNECTION_POOL_CLOSED
    | typeof CONNECTION_POOL_CREATED
    | typeof CONNECTION_POOL_READY
    | typeof CONNECTION_READY;

  /** @internal */
  constructor(pool: ConnectionPool) {
    this.time = new Date();
    this.address = pool.address;
  }
}

/**
 * An event published when a connection pool is created
 * @public
 * @category Event
 */
export class ConnectionPoolCreatedEvent extends ConnectionPoolMonitoringEvent {
  /** The options used to create this connection pool */
  options: Pick<
    ConnectionPoolOptions,
    'maxPoolSize' | 'minPoolSize' | 'maxConnecting' | 'maxIdleTimeMS' | 'waitQueueTimeoutMS'
  >;
  /** @internal */
  name = CONNECTION_POOL_CREATED;

  /** @internal */
  constructor(pool: ConnectionPool) {
    super(pool);
    const { maxConnecting, maxPoolSize, minPoolSize, maxIdleTimeMS, waitQueueTimeoutMS } =
      pool.options;
    this.options = { maxConnecting, maxPoolSize, minPoolSize, maxIdleTimeMS, waitQueueTimeoutMS };
  }
}

/**
 * An event published when a connection pool is ready
 * @public
 * @category Event
 */
export class ConnectionPoolReadyEvent extends ConnectionPoolMonitoringEvent {
  /** @internal */
  name = CONNECTION_POOL_READY;

  /** @internal */
  constructor(pool: ConnectionPool) {
    super(pool);
  }
}

/**
 * An event published when a connection pool is closed
 * @public
 * @category Event
 */
export class ConnectionPoolClosedEvent extends ConnectionPoolMonitoringEvent {
  /** @internal */
  name = CONNECTION_POOL_CLOSED;

  /** @internal */
  constructor(pool: ConnectionPool) {
    super(pool);
  }
}

/**
 * An event published when a connection pool creates a new connection
 * @public
 * @category Event
 */
export class ConnectionCreatedEvent extends ConnectionPoolMonitoringEvent {
  /** A monotonically increasing, per-pool id for the newly created connection */
  connectionId: number | '<monitor>';
  /** @internal */
  name = CONNECTION_CREATED;

  /** @internal */
  constructor(pool: ConnectionPool, connection: { id: number | '<monitor>' }) {
    super(pool);
    this.connectionId = connection.id;
  }
}

/**
 * An event published when a connection is ready for use
 * @public
 * @category Event
 */
export class ConnectionReadyEvent extends ConnectionPoolMonitoringEvent {
  /** The id of the connection */
  connectionId: number | '<monitor>';
  /**
   * The time it took to establish the connection.
   * In accordance with the definition of establishment of a connection
   * specified by `ConnectionPoolOptions.maxConnecting`,
   * it is the time elapsed between emitting a `ConnectionCreatedEvent`
   * and emitting this event as part of the same checking out.
   *
   * Naturally, when establishing a connection is part of checking out,
   * this duration is not greater than
   * `ConnectionCheckedOutEvent.duration`.
   */
  durationMS: number;
  /** @internal */
  name = CONNECTION_READY;

  /** @internal */
  constructor(pool: ConnectionPool, connection: Connection, connectionCreatedEventTime: number) {
    super(pool);
    this.durationMS = now() - connectionCreatedEventTime;
    this.connectionId = connection.id;
  }
}

/**
 * An event published when a connection is closed
 * @public
 * @category Event
 */
export class ConnectionClosedEvent extends ConnectionPoolMonitoringEvent {
  /** The id of the connection */
  connectionId: number | '<monitor>';
  /** The reason the connection was closed */
  reason: string;
  serviceId?: ObjectId;
  /** @internal */
  name = CONNECTION_CLOSED;
  /** @internal */
  error: MongoError | null;

  /** @internal */
  constructor(
    pool: ConnectionPool,
    connection: Pick<Connection, 'id' | 'serviceId'>,
    reason: 'idle' | 'stale' | 'poolClosed' | 'error',
    error?: MongoError
  ) {
    super(pool);
    this.connectionId = connection.id;
    this.reason = reason;
    this.serviceId = connection.serviceId;
    this.error = error ?? null;
  }
}

/**
 * An event published when a request to check a connection out begins
 * @public
 * @category Event
 */
export class ConnectionCheckOutStartedEvent extends ConnectionPoolMonitoringEvent {
  /** @internal */
  name = CONNECTION_CHECK_OUT_STARTED;

  /** @internal */
  constructor(pool: ConnectionPool) {
    super(pool);
  }
}

/**
 * An event published when a request to check a connection out fails
 * @public
 * @category Event
 */
export class ConnectionCheckOutFailedEvent extends ConnectionPoolMonitoringEvent {
  /** The reason the attempt to check out failed */
  reason: string;
  /** @internal */
  error?: MongoError;
  /** @internal */
  name = CONNECTION_CHECK_OUT_FAILED;
  /**
   * The time it took to check out the connection.
   * More specifically, the time elapsed between
   * emitting a `ConnectionCheckOutStartedEvent`
   * and emitting this event as part of the same check out.
   */
  durationMS: number;

  /** @internal */
  constructor(
    pool: ConnectionPool,
    reason: 'poolClosed' | 'timeout' | 'connectionError',
    checkoutTime: number,
    error?: MongoError
  ) {
    super(pool);
    this.durationMS = now() - checkoutTime;
    this.reason = reason;
    this.error = error;
  }
}

/**
 * An event published when a connection is checked out of the connection pool
 * @public
 * @category Event
 */
export class ConnectionCheckedOutEvent extends ConnectionPoolMonitoringEvent {
  /** The id of the connection */
  connectionId: number | '<monitor>';
  /** @internal */
  name = CONNECTION_CHECKED_OUT;
  /**
   * The time it took to check out the connection.
   * More specifically, the time elapsed between
   * emitting a `ConnectionCheckOutStartedEvent`
   * and emitting this event as part of the same checking out.
   *
   */
  durationMS: number;

  /** @internal */
  constructor(pool: ConnectionPool, connection: Connection, checkoutTime: number) {
    super(pool);
    this.durationMS = now() - checkoutTime;
    this.connectionId = connection.id;
  }
}

/**
 * An event published when a connection is checked into the connection pool
 * @public
 * @category Event
 */
export class ConnectionCheckedInEvent extends ConnectionPoolMonitoringEvent {
  /** The id of the connection */
  connectionId: number | '<monitor>';
  /** @internal */
  name = CONNECTION_CHECKED_IN;

  /** @internal */
  constructor(pool: ConnectionPool, connection: Connection) {
    super(pool);
    this.connectionId = connection.id;
  }
}

/**
 * An event published when a connection pool is cleared
 * @public
 * @category Event
 */
export class ConnectionPoolClearedEvent extends ConnectionPoolMonitoringEvent {
  /** @internal */
  serviceId?: ObjectId;

  interruptInUseConnections?: boolean;
  /** @internal */
  name = CONNECTION_POOL_CLEARED;

  /** @internal */
  constructor(
    pool: ConnectionPool,
    options: { serviceId?: ObjectId; interruptInUseConnections?: boolean } = {}
  ) {
    super(pool);
    this.serviceId = options.serviceId;
    this.interruptInUseConnections = options.interruptInUseConnections;
  }
}