fix(urls): enable databases that are not hosted on domain root

Databases can be proxied (nginx, express-pouch, ...) and be hosted
in a sub-path of a domain. This was not taken in account during
the refactoring to use url-parse (commit 7472135).

Fixes pouchdb-community#215

src/utils.js

@@ -6,13 +6,22 @@ import inherits from 'inherits';
 import { btoa } from 'pouchdb-binary-utils';
 
 function getBaseUrl(db) {
+  // Parse database url
+  let url;
   if (typeof db.getUrl === 'function') { // pouchdb pre-6.0.0
-    return urlParse(db.getUrl()).origin;
-  } else if (db.__opts && db.__opts.prefix) { // PouchDB.defaults
-    return db.__opts.prefix;
+    url = urlParse(db.getUrl());
   } else { // pouchdb post-6.0.0
-    return urlParse(db.name).origin;
+    // Use PouchDB.defaults' prefix, if any
+    let prefix = db.__opts && db.__opts.prefix ? db.__opts.prefix + '/' : '';
+    url = urlParse(prefix + db.name);
   }
+
+  // Compute parent path for databases not hosted on domain root (see #215)
+  let path = url.pathname;
+  path = path.endsWith('/') ? path.substring(0, -1) : path;
+  let parentPath = path.split('/').slice(0, -1).join('/');
+
+  return url.origin + parentPath;
 }
 
 function getConfigUrl(db, nodeName) {

test/test.urls.js

@@ -4,15 +4,12 @@ var PouchDB = require('pouchdb-memory');
 var Authentication = require('../lib');
 PouchDB.plugin(Authentication);
 
-var utils = require('./test-utils');
 var chai = require('chai');
 chai.should();
 
-var serverHost = utils.getConfig().serverHost;
-
 describe('urls', function () {
 
-  var hostUrl = serverHost;
+  var hostUrl = 'http://example.com';
   var dbName = 'testdb';
   var dbUrl = hostUrl + '/' + dbName;
 
@@ -47,4 +44,10 @@ describe('urls', function () {
     var usersUrl = db.getUsersDatabaseUrl();
     usersUrl.should.equal(hostUrl + '/_users');
   });
+
+  it('Correct users database url for proxied database urls (issue-215)', function () {
+    var db = new PouchDB(hostUrl + '/db/' + dbName);
+    var usersUrl = db.getUsersDatabaseUrl();
+    usersUrl.should.equal(hostUrl + '/db/_users');
+  });
 });