lib/adapters/websql/utils.js

'use strict';

var utils = require('../../utils');
var errors = require('../../deps/errors');

var websqlConstants = require('./constants');

var BY_SEQ_STORE = websqlConstants.BY_SEQ_STORE;
var ATTACH_STORE = websqlConstants.ATTACH_STORE;
var ATTACH_AND_SEQ_STORE = websqlConstants.ATTACH_AND_SEQ_STORE;

// escapeBlob and unescapeBlob are workarounds for a websql bug:
// https://code.google.com/p/chromium/issues/detail?id=422690
// https://bugs.webkit.org/show_bug.cgi?id=137637
// The goal is to never actually insert the \u0000 character
// in the database.
function escapeBlob(str) {
  return str
    .replace(/\u0002/g, '\u0002\u0002')
    .replace(/\u0001/g, '\u0001\u0002')
    .replace(/\u0000/g, '\u0001\u0001');
}

function unescapeBlob(str) {
  return str
    .replace(/\u0001\u0001/g, '\u0000')
    .replace(/\u0001\u0002/g, '\u0001')
    .replace(/\u0002\u0002/g, '\u0002');
}

function stringifyDoc(doc) {
  // don't bother storing the id/rev. it uses lots of space,
  // in persistent map/reduce especially
  delete doc._id;
  delete doc._rev;
  return JSON.stringify(doc);
}

function unstringifyDoc(doc, id, rev) {
  doc = JSON.parse(doc);
  doc._id = id;
  doc._rev = rev;
  return doc;
}

// question mark groups IN queries, e.g. 3 -> '(?,?,?)'
function qMarks(num) {
  var s = '(';
  while (num--) {
    s += '?';
    if (num) {
      s += ',';
    }
  }
  return s + ')';
}

function select(selector, table, joiner, where, orderBy) {
  return 'SELECT ' + selector + ' FROM ' +
    (typeof table === 'string' ? table : table.join(' JOIN ')) +
    (joiner ? (' ON ' + joiner) : '') +
    (where ? (' WHERE ' +
    (typeof where === 'string' ? where : where.join(' AND '))) : '') +
    (orderBy ? (' ORDER BY ' + orderBy) : '');
}

function compactRevs(revs, docId, tx) {

  if (!revs.length) {
    return;
  }

  var numDone = 0;
  var seqs = [];

  function checkDone() {
    if (++numDone === revs.length) { // done
      deleteOrphans();
    }
  }

  function deleteOrphans() {
    // find orphaned attachment digests

    if (!seqs.length) {
      return;
    }

    var sql = 'SELECT DISTINCT digest AS digest FROM ' +
      ATTACH_AND_SEQ_STORE + ' WHERE seq IN ' + qMarks(seqs.length);

    tx.executeSql(sql, seqs, function (tx, res) {

      var digestsToCheck = [];
      for (var i = 0; i < res.rows.length; i++) {
        digestsToCheck.push(res.rows.item(i).digest);
      }
      if (!digestsToCheck.length) {
        return;
      }

      var sql = 'DELETE FROM ' + ATTACH_AND_SEQ_STORE +
        ' WHERE seq IN (' +
        seqs.map(function () { return '?'; }).join(',') +
        ')';
      tx.executeSql(sql, seqs, function (tx) {

        var sql = 'SELECT digest FROM ' + ATTACH_AND_SEQ_STORE +
          ' WHERE digest IN (' +
          digestsToCheck.map(function () { return '?'; }).join(',') +
          ')';
        tx.executeSql(sql, digestsToCheck, function (tx, res) {
          var nonOrphanedDigests = new utils.Set();
          for (var i = 0; i < res.rows.length; i++) {
            nonOrphanedDigests.add(res.rows.item(i).digest);
          }
          digestsToCheck.forEach(function (digest) {
            if (nonOrphanedDigests.has(digest)) {
              return;
            }
            tx.executeSql(
              'DELETE FROM ' + ATTACH_AND_SEQ_STORE + ' WHERE digest=?',
              [digest]);
            tx.executeSql(
              'DELETE FROM ' + ATTACH_STORE + ' WHERE digest=?', [digest]);
          });
        });
      });
    });
  }

  // update by-seq and attach stores in parallel
  revs.forEach(function (rev) {
    var sql = 'SELECT seq FROM ' + BY_SEQ_STORE +
      ' WHERE doc_id=? AND rev=?';

    tx.executeSql(sql, [docId, rev], function (tx, res) {
      if (!res.rows.length) { // already deleted
        return checkDone();
      }
      var seq = res.rows.item(0).seq;
      seqs.push(seq);

      tx.executeSql(
        'DELETE FROM ' + BY_SEQ_STORE + ' WHERE seq=?', [seq], checkDone);
    });
  });
}

function unknownError(callback) {
  return function (event) {
    // event may actually be a SQLError object, so report is as such
    var errorNameMatch = event && event.constructor.toString()
        .match(/function ([^\(]+)/);
    var errorName = (errorNameMatch && errorNameMatch[1]) || event.type;
    var errorReason = event.target || event.message;
    callback(errors.error(errors.WSQ_ERROR, errorReason, errorName));
  };
}

function getSize(opts) {
  if ('size' in opts) {
    // triggers immediate popup in iOS, fixes #2347
    // e.g. 5000001 asks for 5 MB, 10000001 asks for 10 MB,
    return opts.size * 1000000;
  }
  // In iOS, doesn't matter as long as it's <= 5000000.
  // Except that if you request too much, our tests fail
  // because of the native "do you accept?" popup.
  // In Android <=4.3, this value is actually used as an
  // honest-to-god ceiling for data, so we need to
  // set it to a decently high number.
  var isAndroid = /Android/.test(window.navigator.userAgent);
  return isAndroid ? 5000000 : 1; // in PhantomJS, if you use 0 it will crash
}

function createOpenDBFunction() {
  if (typeof sqlitePlugin !== 'undefined') {
    // The SQLite Plugin started deviating pretty heavily from the
    // standard openDatabase() function, as they started adding more features.
    // It's better to just use their "new" format and pass in a big ol'
    // options object.
    return sqlitePlugin.openDatabase.bind(sqlitePlugin);
  }

  if (typeof openDatabase !== 'undefined') {
    return function openDB(opts) {
      // Traditional WebSQL API
      return openDatabase(opts.name, opts.version, opts.description, opts.size);
    };
  }
}

var cachedDatabases = {};

function openDB(opts) {

  var openDBFunction = createOpenDBFunction();

  var db = cachedDatabases[opts.name];
  if (!db) {
    db = cachedDatabases[opts.name] = openDBFunction(opts);
    db._sqlitePlugin = typeof sqlitePlugin !== 'undefined';
  }
  return db;
}

function valid() {
  // SQLitePlugin leaks this global object, which we can use
  // to detect if it's installed or not. The benefit is that it's
  // declared immediately, before the 'deviceready' event has fired.
  return typeof openDatabase !== 'undefined' ||
    typeof SQLitePlugin !== 'undefined';
}

module.exports = {
  escapeBlob: escapeBlob,
  unescapeBlob: unescapeBlob,
  stringifyDoc: stringifyDoc,
  unstringifyDoc: unstringifyDoc,
  qMarks: qMarks,
  select: select,
  compactRevs: compactRevs,
  unknownError: unknownError,
  getSize: getSize,
  openDB: openDB,
  valid: valid
};