const Transaction = require('../../execution/transaction');
const debug = require('debug')('knex:tx');

module.exports = class Transaction_MSSQL extends Transaction {
  begin(conn) {
    debug('%s: begin', this.txid);
    return conn.tx_
      .begin(nameToIsolationLevelEnum(this.isolationLevel))
      .then(this._resolver, this._rejecter);
  }

  async savepoint(conn) {
    debug('%s: savepoint at', this.txid);
    return this.query(conn, `SAVE TRANSACTION ${this.txid}`);
  }

  commit(conn, value) {
    this._completed = true;
    debug('%s: commit', this.txid);
    return conn.tx_.commit().then(() => this._resolver(value), this._rejecter);
  }

  release(conn, value) {
    return this._resolver(value);
  }

  rollback(conn, error) {
    this._completed = true;
    debug('%s: rolling back', this.txid);
    return conn.tx_.rollback().then(
      () => {
        let err = error;
        if (error === undefined) {
          if (this.doNotRejectOnRollback) {
            this._resolver();
            return;
          }
          err = new Error(`Transaction rejected with non-error: ${error}`);
        }
        this._rejecter(err);
      },
      (err) => {
        if (error) {
          try {
            err.originalError = error;
          } catch (_err) {
            // This is to handle https://github.com/knex/knex/issues/4128
          }
        }
        return this._rejecter(err);
      }
    );
  }

  async rollbackTo(conn, error) {
    debug('%s: rolling backTo', this.txid);
    await this.query(conn, `ROLLBACK TRANSACTION ${this.txid}`, 2, error);

    this._rejecter(error);
  }

  // Acquire a connection and create a disposer - either using the one passed
  // via config or getting one off the client. The disposer will be called once
  // the original promise is marked completed.
  async acquireConnection(config, cb) {
    const configConnection = config && config.connection;
    const conn =
      (this.outerTx && this.outerTx.conn) ||
      configConnection ||
      (await this.client.acquireConnection());

    try {
      conn.__knexTxId = this.txid;
      if (!this.outerTx) {
        this.conn = conn;
        conn.tx_ = conn.transaction();
      }

      return await cb(conn);
    } finally {
      if (!this.outerTx) {
        if (conn.tx_) {
          if (!this._completed) {
            debug('%s: unreleased transaction', this.txid);
            conn.tx_.rollback();
          }
          conn.tx_ = null;
        }
        this.conn = null;
        if (!configConnection) {
          debug('%s: releasing connection', this.txid);
          this.client.releaseConnection(conn);
        } else {
          debug('%s: not releasing external connection', this.txid);
        }
      }
    }
  }
};

function nameToIsolationLevelEnum(level) {
  if (!level) return;
  level = level.toUpperCase().replace(' ', '_');
  const knownEnum = isolationEnum[level];
  if (!knownEnum) {
    throw new Error(
      `Unknown Isolation level, was expecting one of: ${JSON.stringify(
        humanReadableKeys
      )}`
    );
  }
  return knownEnum;
}

// Based on: https://github.com/tediousjs/node-mssql/blob/master/lib/isolationlevel.js
const isolationEnum = {
  READ_UNCOMMITTED: 0x01,
  READ_COMMITTED: 0x02,
  REPEATABLE_READ: 0x03,
  SERIALIZABLE: 0x04,
  SNAPSHOT: 0x05,
};
const humanReadableKeys = Object.keys(isolationEnum).map((key) =>
  key.toLowerCase().replace('_', ' ')
);