packages/node_modules/pouchdb-core/src/parseAdapter.js

import PouchDB from './constructor';
import { guardedConsole, hasLocalStorage } from 'pouchdb-utils';

function parseAdapter(name, opts) {
  var match = name.match(/([a-z\-]*):\/\/(.*)/);
  if (match) {
    // the http adapter expects the fully qualified name
    name = /http(s?)/.test(match[1]) ? match[1] + '://' + match[2] : match[2];
    return {name: name, adapter: match[1]};
  }

  if (process.env.POUCHDB_LITE) {
    adapterName = 'idb';
  } else {
    // check for browsers that have been upgraded from websql-only to websql+idb
    var skipIdb = 'idb' in PouchDB.adapters &&
      'websql' in PouchDB.adapters &&
      hasLocalStorage() &&
      localStorage['_pouch__websqldb_' + PouchDB.prefix + name];

    var adapterName;

    if (opts.adapter) {
      adapterName = opts.adapter;
    } else if (typeof opts !== 'undefined' && opts.db) {
      adapterName = 'leveldb';
    } else { // automatically determine adapter
      for (var i = 0; i < PouchDB.preferredAdapters.length; ++i) {
        adapterName = PouchDB.preferredAdapters[i];
        /* istanbul ignore if */
        if (!process.env.POUCHDB_LITE && skipIdb && adapterName === 'idb') {
          // log it, because this can be confusing during development
          guardedConsole('log', 'PouchDB is downgrading "' + name + '" to WebSQL to' +
            ' avoid data loss, because it was already opened with WebSQL.');
          continue; // keep using websql to avoid user data loss
        }
        break;
      }
    }
  }

  var adapter = PouchDB.adapters[adapterName];

  // if adapter is invalid, then an error will be thrown later
  var usePrefix = (adapter && 'use_prefix' in adapter) ?
    adapter.use_prefix : true;

  return {
    name: usePrefix ? (PouchDB.prefix + name) : name,
    adapter: adapterName
  };
}

export default parseAdapter;