var PouchDB = require('pouchdb')
PouchDB.plugin(require('pouch-resolve-conflicts'))

// The resolve function. This function takes two documents and returns either
// one of them, a changed version of one of them, or nothing. In the latter the
// conflict will not be resolved. If there are more than two conflicting
// versions this function will be called with each version against the former
// result.
function resolveFun (a, b) {
  // cannot merge: return nothing
  if ('foo' in a && 'foo' in b) return
  
  // return one of the docs
  if ('foo' in a) return a
  if ('foo' in b) return b
  
  // return changed doc
  a.foo = 'bar'
  return a
}

var db = new PouchDB('mydb')

db
  // Lets have a conflict
  .bulkDocs({
    docs: [
      { _id: 'mydoc', _rev: '1-one', foo: 'bar' },
      { _id: 'mydoc', _rev: '1-two', bar: 'baz' }
    ],
    new_edits: false
  })
  // Query doc with `conflicts: true`
  .then(function(response) {
    return db.get('mydoc', { conflicts: true })
  })
  // And resolve it
  .then(function(doc) {
    return db.resolveConflicts(doc, resolveFun)
  })

// `resolveFun` can also return a promise:
function resolveFun (a, b) {
  return new Promise(function(resolve, reject) {
    if ('foo' in a && 'foo' in b) return resolve(undefined)

    if ('foo' in a) return resolve(a)
    if ('foo' in b) return resolve(b)

    a.foo = 'bar'
    return resolve(a)
  })
}