db.js

'use strict'

var _ = require('lodash')
var config = require('./config')
var mongo = require('monk')(`${config.MONGO_HOST}/${config.MONGO_MAIN_DB}`)

module.exports = mongo

function safeDrop (name) {
  const p = mongo.get(name).drop()
  return p.then(null, () => {
    p.fulfill()
  })
}

module.exports.clear = function () {
  const collectionsToDrop = [].slice.call(arguments)
  return Promise.all(collectionsToDrop.map(safeDrop))
}

module.exports.queryFields = function (fields) {
  let mongoQuery = _.cloneDeep(module.exports.NO_MONGO_ID)
  if (fields) {
    for (let field of fields) {
      mongoQuery.fields[field] = 1
    }
  }
  return mongoQuery
}

module.exports.filterLink = function (name, id) {
  return {[name]: id}
}

// cache to avoid expensive redundant calls to index same fields
var indexCache = {}

module.exports.ensureIndex = function (name, field) {
  if (!indexCache[name]) {
    indexCache[name] = new Set()
  }
  if (!indexCache[name].has(field)) {
    indexCache[name].add(field)
    mongo.get(name).ensureIndex({[field]: 'hashed'})
  }
}

module.exports.NO_MONGO_ID = {fields: {_id: 0}}
module.exports.ID_ONLY = {fields: {id: 1, _id: 0}}