import { type Connection, type MongoError } from '..';
import { type BSONSerializeOptions, type Document, resolveBSONOptions } from '../bson';
import { type MongoDBResponse } from '../cmap/wire_protocol/responses';
import { type Abortable } from '../mongo_types';
import { ReadPreference, type ReadPreferenceLike } from '../read_preference';
import type { Server, ServerCommandOptions } from '../sdam/server';
import type { ClientSession } from '../sessions';
import { type TimeoutContext } from '../timeout';
import type { MongoDBNamespace } from '../utils';

export const Aspect = {
  READ_OPERATION: Symbol('READ_OPERATION'),
  WRITE_OPERATION: Symbol('WRITE_OPERATION'),
  RETRYABLE: Symbol('RETRYABLE'),
  EXPLAINABLE: Symbol('EXPLAINABLE'),
  SKIP_COLLATION: Symbol('SKIP_COLLATION'),
  CURSOR_CREATING: Symbol('CURSOR_CREATING'),
  MUST_SELECT_SAME_SERVER: Symbol('MUST_SELECT_SAME_SERVER'),
  COMMAND_BATCHING: Symbol('COMMAND_BATCHING'),
  SUPPORTS_RAW_DATA: Symbol('SUPPORTS_RAW_DATA')
} as const;

/** @public */
export type Hint = string | Document;

/** @public */
export interface OperationOptions extends BSONSerializeOptions {
  /** Specify ClientSession for this command */
  session?: ClientSession;
  willRetryWrite?: boolean;

  /** The preferred read preference (ReadPreference.primary, ReadPreference.primary_preferred, ReadPreference.secondary, ReadPreference.secondary_preferred, ReadPreference.nearest). */
  readPreference?: ReadPreferenceLike;

  /** @internal Hints to `executeOperation` that this operation should not unpin on an ended transaction */
  bypassPinningCheck?: boolean;

  /** @internal Hint to `executeOperation` to omit maxTimeMS */
  omitMaxTimeMS?: boolean;

  /**
   * @experimental
   * Specifies the time an operation will run until it throws a timeout error
   */
  timeoutMS?: number;
}

/**
 * This class acts as a parent class for any operation and is responsible for setting this.options,
 * as well as setting and getting a session.
 * Additionally, this class implements `hasAspect`, which determines whether an operation has
 * a specific aspect.
 * @internal
 */
export abstract class AbstractOperation<TResult = any> {
  ns!: MongoDBNamespace;
  readPreference: ReadPreference;
  server!: Server;
  bypassPinningCheck: boolean;

  // BSON serialization options
  bsonOptions?: BSONSerializeOptions;

  options: OperationOptions & Abortable;

  /** Specifies the time an operation will run until it throws a timeout error. */
  timeoutMS?: number;

  private _session: ClientSession | undefined;

  static aspects?: Set<symbol>;

  constructor(options: OperationOptions & Abortable = {}) {
    this.readPreference = this.hasAspect(Aspect.WRITE_OPERATION)
      ? ReadPreference.primary
      : (ReadPreference.fromOptions(options) ?? ReadPreference.primary);

    // Pull the BSON serialize options from the already-resolved options
    this.bsonOptions = resolveBSONOptions(options);

    this._session = options.session != null ? options.session : undefined;

    this.options = options;
    this.bypassPinningCheck = !!options.bypassPinningCheck;
  }

  /** Must match the first key of the command object sent to the server.
  Command name should be stateless (should not use 'this' keyword) */
  abstract get commandName(): string;

  hasAspect(aspect: symbol): boolean {
    const ctor = this.constructor as { aspects?: Set<symbol> };
    if (ctor.aspects == null) {
      return false;
    }

    return ctor.aspects.has(aspect);
  }

  // Make sure the session is not writable from outside this class.
  get session(): ClientSession | undefined {
    return this._session;
  }

  set session(session: ClientSession) {
    this._session = session;
  }

  clearSession() {
    this._session = undefined;
  }

  resetBatch(): boolean {
    return true;
  }

  get canRetryRead(): boolean {
    return this.hasAspect(Aspect.RETRYABLE) && this.hasAspect(Aspect.READ_OPERATION);
  }

  get canRetryWrite(): boolean {
    return this.hasAspect(Aspect.RETRYABLE) && this.hasAspect(Aspect.WRITE_OPERATION);
  }
  abstract SERVER_COMMAND_RESPONSE_TYPE: typeof MongoDBResponse;

  /**
   * Build a raw command document.
   */
  abstract buildCommand(connection: Connection, session?: ClientSession): Document;

  /**
   * Builds an instance of `ServerCommandOptions` to be used for operation execution.
   */
  abstract buildOptions(timeoutContext: TimeoutContext): ServerCommandOptions;

  /**
   * Given an instance of a MongoDBResponse, map the response to the correct result type.  For
   * example, a `CountOperation` might map the response as follows:
   *
   * ```typescript
   *  override handleOk(response: InstanceType<typeof this.SERVER_COMMAND_RESPONSE_TYPE>): TResult {
   *    return response.toObject(this.bsonOptions).n ?? 0;
   *  }
   *
   *  // or, with type safety:
   *  override handleOk(response: InstanceType<typeof this.SERVER_COMMAND_RESPONSE_TYPE>): TResult {
   *    return response.getNumber('n') ?? 0;
   *  }
   * ```
   */
  handleOk(response: InstanceType<typeof this.SERVER_COMMAND_RESPONSE_TYPE>): TResult {
    return response.toObject(this.bsonOptions) as TResult;
  }

  /**
   * Optional.
   *
   * If the operation performs error handling, such as wrapping, renaming the error, or squashing errors
   * this method can be overridden.
   */
  handleError(error: MongoError): TResult | never {
    throw error;
  }
}

export function defineAspects(
  operation: { aspects?: Set<symbol> },
  aspects: symbol | symbol[] | Set<symbol>
): Set<symbol> {
  if (!Array.isArray(aspects) && !(aspects instanceof Set)) {
    aspects = [aspects];
  }

  aspects = new Set(aspects);
  Object.defineProperty(operation, 'aspects', {
    value: aspects,
    writable: false
  });

  return aspects;
}