websql-configurable/lib/websql/WebSQLTransaction.js

WebSQL Database API, implemented for Node using sqlite3

import noop from 'noop-fn';
import Queue from 'tiny-queue';
import immediate from 'immediate';
import WebSQLResultSet from './WebSQLResultSet.js';

function errorUnhandled() {
  return true; // a non-truthy return indicates error was handled
}

// WebSQL has some bizarre behavior regarding insertId/rowsAffected. To try
// to match the observed behavior of Chrome/Safari as much as possible, we
// sniff the SQL message to try to massage the returned insertId/rowsAffected.
// This helps us pass the tests, although it's error-prone and should
// probably be revised.
function massageSQLResult(sql, insertId, rowsAffected, rows) {
  if (/^\s*UPDATE\b/i.test(sql)) {
    // insertId is always undefined for "UPDATE" statements
    insertId = void 0;
  } else if (/^\s*CREATE\s+TABLE\b/i.test(sql)) {
    // WebSQL always returns an insertId of 0 for "CREATE TABLE" statements
    insertId = 0;
    rowsAffected = 0;
  } else if (/^\s*DROP\s+TABLE\b/i.test(sql)) {
    // WebSQL always returns insertId=undefined and rowsAffected=0
    // for "DROP TABLE" statements. Go figure.
    insertId = void 0;
    rowsAffected = 0;
  } else if (!/^\s*INSERT\b/i.test(sql)) {
    // for all non-inserts (deletes, etc.) insertId is always undefined
    // ¯\_(ツ)_/¯
    insertId = void 0;
  }
  return new WebSQLResultSet(insertId, rowsAffected, rows);
}

function SQLTask(sql, args, sqlCallback, sqlErrorCallback) {
  this.sql = sql;
  this.args = args;
  this.sqlCallback = sqlCallback;
  this.sqlErrorCallback = sqlErrorCallback;
}

function runBatch(self, batch) {

  function onDone() {
    self._running = false;
    runAllSql(self);
  }

  var readOnly = self._websqlDatabase._currentTask.readOnly;

  self._websqlDatabase._db.exec(batch, readOnly, function (err, results) {
    /* istanbul ignore next */
    if (err) {
      self._error = err;
      return onDone();
    }
    for (var i = 0; i < results.length; i++) {
      var res = results[i];
      var batchTask = batch[i];
      if (res.error) {
        if (batchTask.sqlErrorCallback(self, res.error)) {
          // user didn't handle the error
          self._error = res.error;
          return onDone();
        }
      } else {
        try {
          batchTask.sqlCallback(self, massageSQLResult(
            batch[i].sql, res.insertId, res.rowsAffected, res.rows));
        } catch (err) {
          self._error = err;
          runAllSql(self);
        }
      }
    }
    onDone();
  });
}

function runAllSql(self) {
  if (self._running || self._complete) {
    return;
  }
  if (self._error || !self._sqlQueue.length) {
    self._complete = true;
    return self._websqlDatabase._onTransactionComplete(self._error);
  }
  self._running = true;
  var batch = [];
  var task;
  while ((task = self._sqlQueue.shift())) {
    batch.push(task);
  }
  runBatch(self, batch);
}

function executeSql(self, sql, args, sqlCallback, sqlErrorCallback, executeDelay) {
  self._sqlQueue.push(new SQLTask(sql, args, sqlCallback, sqlErrorCallback));
  if (self._runningTimeout) {
    return;
  }
  self._runningTimeout = true;
  executeDelay(function () {
    self._runningTimeout = false;
    runAllSql(self);
  });
}

function WebSQLTransaction(websqlDatabase, executeDelay) {
  this._websqlDatabase = websqlDatabase;
  this._error = null;
  this._complete = false;
  this._runningTimeout = false;
  this._executeDelay = executeDelay || immediate;
  this._sqlQueue = new Queue();
  if (!websqlDatabase._currentTask.readOnly) {
    // Since we serialize all access to the database, there is no need to
    // run read-only tasks in a transaction. This is a perf boost.
    this._sqlQueue.push(new SQLTask('BEGIN;', [], noop, noop));
  }
}

/**
 * @param {string} sql
 * @param {ObjectArray} args
 * @param {SQLStatementCallback} sqlCallback
 * @param {SQLStatementErrorCallback} sqlErrorCallback
 */
WebSQLTransaction.prototype.executeSql = function (sql, args, sqlCallback, sqlErrorCallback) {
  args = Array.isArray(args) ? args : [];
  sqlCallback = typeof sqlCallback === 'function' ? sqlCallback : noop;
  sqlErrorCallback = typeof sqlErrorCallback === 'function' ? sqlErrorCallback : errorUnhandled;

  executeSql(this, sql, args, sqlCallback, sqlErrorCallback, this._executeDelay);
};

WebSQLTransaction.prototype._checkDone = function () {
  runAllSql(this);
};

export default WebSQLTransaction;