pouchdb-find/lib/abstract-mapreduce/create-view.js

Easy-to-use query language for PouchDB

'use strict';

var upsert = require('./upsert');
var utils = require('./utils');
var Promise = utils.Promise;

function stringify(input) {
  if (!input) {
    return 'undefined'; // backwards compat for empty reduce
  }
  // for backwards compat with mapreduce, functions/strings are stringified
  // as-is. everything else is JSON-stringified.
  switch (typeof input) {
    case 'function':
      // e.g. a mapreduce map
      return input.toString();
    case 'string':
      // e.g. a mapreduce built-in _reduce function
      return input.toString();
    default:
      // e.g. a JSON object in the case of mango queries
      return JSON.stringify(input);
  }
}

module.exports = function (opts) {
  var sourceDB = opts.db;
  var viewName = opts.viewName;
  var mapFun = opts.map;
  var reduceFun = opts.reduce;
  var temporary = opts.temporary;
  var pluginName = opts.pluginName;

  // the "undefined" part is for backwards compatibility
  var viewSignature = stringify(mapFun) + stringify(reduceFun) +
    'undefined';

  if (!temporary && sourceDB._cachedViews) {
    var cachedView = sourceDB._cachedViews[viewSignature];
    if (cachedView) {
      return Promise.resolve(cachedView);
    }
  }

  return sourceDB.info().then(function (info) {

    var depDbName = info.db_name + '-mrview-' +
      (temporary ? 'temp' : utils.MD5(viewSignature));

    // save the view name in the source PouchDB so it can be cleaned up if necessary
    // (e.g. when the _design doc is deleted, remove all associated view data)
    function diffFunction(doc) {
      doc.views = doc.views || {};
      var fullViewName = viewName;
      if (fullViewName.indexOf('/') === -1) {
        fullViewName = viewName + '/' + viewName;
      }
      var depDbs = doc.views[fullViewName] = doc.views[fullViewName] || {};
      /* istanbul ignore if */
      if (depDbs[depDbName]) {
        return; // no update necessary
      }
      depDbs[depDbName] = true;
      return doc;
    }
    return upsert(sourceDB, '_local/' + pluginName, diffFunction).then(function () {
      return sourceDB.registerDependentDatabase(depDbName).then(function (res) {
        var db = res.db;
        db.auto_compaction = true;
        var view = {
          name: depDbName,
          db: db, 
          sourceDB: sourceDB,
          adapter: sourceDB.adapter,
          mapFun: mapFun,
          reduceFun: reduceFun
        };
        return view.db.get('_local/lastSeq').catch(function (err) {
          /* istanbul ignore if */
          if (err.status !== 404) {
            throw err;
          }
        }).then(function (lastSeqDoc) {
          view.seq = lastSeqDoc ? lastSeqDoc.seq : 0;
          if (!temporary) {
            sourceDB._cachedViews = sourceDB._cachedViews || {};
            sourceDB._cachedViews[viewSignature] = view;
            view.db.on('destroyed', function () {
              delete sourceDB._cachedViews[viewSignature];
            });
          }
          return view;
        });
      });
    });
  });
};