packages/node_modules/pouchdb-generate-replication-id/src/index.js

import Promise from 'pouchdb-promise';
import { binaryMd5 } from 'pouchdb-md5';
import { btoa } from 'pouchdb-binary-utils';

function sortObjectPropertiesByKey(queryParams) {
  return Object.keys(queryParams).sort().reduce(function (result, key) {
    result[key] = queryParams[key];
    return result;
  }, {});
}

// Generate a unique id particular to this replication.
// Not guaranteed to align perfectly with CouchDB's rep ids.
function generateReplicationId(src, target, opts) {
  var docIds = opts.doc_ids ? opts.doc_ids.sort() : '';
  var filterFun = opts.filter ? opts.filter.toString() : '';
  var queryParams = '';
  var filterViewName =  '';

  if (opts.filter && opts.query_params) {
    queryParams = JSON.stringify(sortObjectPropertiesByKey(opts.query_params));
  }

  if (opts.filter && opts.filter === '_view') {
    filterViewName = opts.view.toString();
  }

  return Promise.all([src.id(), target.id()]).then(function (res) {
    var queryData = res[0] + res[1] + filterFun + filterViewName +
      queryParams + docIds;
    if (process.env.POUCHDB_LITE) {
      // do a simple btoa algorithm, not a full md5sum
      return Promise.resolve('_local/' + btoa(queryData));
    } else {
      return new Promise(function (resolve) {
        binaryMd5(queryData, resolve);
      }).then(function (md5sum) {
        // can't use straight-up md5 alphabet, because
        // the char '/' is interpreted as being for attachments,
        // and + is also not url-safe
        md5sum = md5sum.replace(/\//g, '.').replace(/\+/g, '_');
        return '_local/' + md5sum;
      });
    }
  });
}

export default generateReplicationId;