import { Deferrable } from 'sequelize/lib/deferrable';
import { Logging } from 'sequelize/lib/model';
import { Sequelize } from 'sequelize/lib/sequelize';

/**
 * The transaction object is used to identify a running transaction. It is created by calling
 * `Sequelize.transaction()`.
 *
 * To run a query under a transaction, you should pass the transaction in the options object.
 */
export class Transaction {
  constructor(sequelize: Sequelize, options: TransactionOptions);

  /**
   * Commit the transaction
   */
  public commit(): Promise<void>;

  /**
   * Rollback (abort) the transaction
   */
  public rollback(): Promise<void>;

  /**
   * Adds hook that is run after a transaction is committed
   */
  public afterCommit(fn: (transaction: this) => void | Promise<void>): void;

  /**
   * Returns possible options for row locking
   */
  static get LOCK(): typeof LOCK;

  /**
   * Same as its static version, but can also be called on instances of
   * transactions to get possible options for row locking directly from the
   * instance.
   */
  get LOCK(): typeof LOCK;
}

// tslint:disable-next-line no-namespace
export namespace Transaction {
  /**
   * Isolations levels can be set per-transaction by passing `options.isolationLevel` to `sequelize.transaction`.
   * Default to `REPEATABLE_READ` but you can override the default isolation level by passing `options.isolationLevel` in `new Sequelize`.
   *
   * The possible isolations levels to use when starting a transaction:
   *
   * ```js
   * {
   *   READ_UNCOMMITTED: "READ UNCOMMITTED",
   *   READ_COMMITTED: "READ COMMITTED",
   *   REPEATABLE_READ: "REPEATABLE READ",
   *   SERIALIZABLE: "SERIALIZABLE"
   * }
   * ```
   *
   * Pass in the desired level as the first argument:
   *
   * ```js
   * try {
   *   await sequelize.transaction({isolationLevel: Sequelize.Transaction.SERIALIZABLE}, transaction => {
   *      // your transactions
   *   });
   *   // transaction has been committed. Do something after the commit if required.
   * } catch(err) {
   *   // do something with the err.
   * }
   * ```
   */
  enum ISOLATION_LEVELS {
    READ_UNCOMMITTED = 'READ UNCOMMITTED',
    READ_COMMITTED = 'READ COMMITTED',
    REPEATABLE_READ = 'REPEATABLE READ',
    SERIALIZABLE = 'SERIALIZABLE',
  }

  enum TYPES {
    DEFERRED = 'DEFERRED',
    IMMEDIATE = 'IMMEDIATE',
    EXCLUSIVE = 'EXCLUSIVE',
  }
}

/**
 * Possible options for row locking. Used in conjunction with `find` calls:
 *
 * ```js
 * t1 // is a transaction
 * t1.LOCK.UPDATE,
 * t1.LOCK.SHARE,
 * t1.LOCK.KEY_SHARE, // Postgres 9.3+ only
 * t1.LOCK.NO_KEY_UPDATE // Postgres 9.3+ only
 * ```
 *
 * Usage:
 * ```js
 * t1 // is a transaction
 * Model.findAll({
 *   where: ...,
 *   transaction: t1,
 *   lock: t1.LOCK...
 * });
 * ```
 *
 * Postgres also supports specific locks while eager loading by using OF:
 * ```js
 * UserModel.findAll({
 *   where: ...,
 *   include: [TaskModel, ...],
 *   transaction: t1,
 *   lock: {
 *   level: t1.LOCK...,
 *   of: UserModel
 *   }
 * });
 * ```
 * UserModel will be locked but TaskModel won't!
 */
export enum LOCK {
  UPDATE = 'UPDATE',
  SHARE = 'SHARE',
  /**
   * Postgres 9.3+ only
   */
  KEY_SHARE = 'KEY SHARE',
  /**
   * Postgres 9.3+ only
   */
  NO_KEY_UPDATE = 'NO KEY UPDATE',
}

/**
 * Options provided when the transaction is created
 */
export interface TransactionOptions extends Logging {
  autocommit?: boolean;
  isolationLevel?: Transaction.ISOLATION_LEVELS;
  type?: Transaction.TYPES;
  deferrable?: string | Deferrable;
  readOnly?: boolean;
  /**
   * Parent transaction.
   */
  transaction?: Transaction | null;
}

export default Transaction;
