Create New Connections per #68 (#69)

Enable a prototypical API for creating new connections and datasources from scratch.
This uses ET to do XML manipulation, and is hard coded to "10.0" style integrated connections.

This will go away with the new editor/physical/logical model work underway, but it fixes a bug and will let us play around for now.

Author: t8y8

tableaudocumentapi/connection.py

@@ -3,6 +3,7 @@
 # Connection - A class for writing connections to Tableau files
 #
 ###############################################################################
+import xml.etree.ElementTree as ET
 from tableaudocumentapi.dbclass import is_valid_dbclass
 
 
@@ -33,6 +34,17 @@ def __init__(self, connxml):
     def __repr__(self):
         return "'<Connection server='{}' dbname='{}' @ {}>'".format(self._server, self._dbname, hex(id(self)))
 
+    @classmethod
+    def from_attributes(cls, server, dbname, username, dbclass, authentication=''):
+        root = ET.Element('connection', authentication=authentication)
+        xml = cls(root)
+        xml.server = server
+        xml.dbname = dbname
+        xml.username = username
+        xml.dbclass = dbclass
+
+        return xml
+
     ###########
     # dbname
     ###########
@@ -120,4 +132,4 @@ def dbclass(self, value):
             raise AttributeError("'{}' is not a valid database type".format(value))
 
         self._class = value
-        self._connectionXML.set('dbclass', value)
+        self._connectionXML.set('class', value)

tableaudocumentapi/datasource.py

@@ -5,8 +5,10 @@
 ###############################################################################
 import collections
 import itertools
+import random
 import xml.etree.ElementTree as ET
 import xml.sax.saxutils as sax
+from uuid import uuid4
 
 from tableaudocumentapi import Connection, xfile
 from tableaudocumentapi import Field
@@ -38,6 +40,7 @@ def _is_used_by_worksheet(names, field):
 
 
 class FieldDictionary(MultiLookupDict):
+
     def used_by_sheet(self, name):
         # If we pass in a string, no need to get complicated, just check to see if name is in
         # the field's list of worksheets
@@ -63,7 +66,36 @@ def _column_object_from_metadata_xml(metadata_xml):
     return _ColumnObjectReturnTuple(field_object.id, field_object)
 
 
+def base36encode(number):
+    """Converts an integer into a base36 string."""
+
+    ALPHABET = "0123456789abcdefghijklmnopqrstuvwxyz"
+
+    base36 = ''
+    sign = ''
+
+    if number < 0:
+        sign = '-'
+        number = -number
+
+    if 0 <= number < len(ALPHABET):
+        return sign + ALPHABET[number]
+
+    while number != 0:
+        number, i = divmod(number, len(ALPHABET))
+        base36 = ALPHABET[i] + base36
+
+    return sign + base36
+
+
+def make_unique_name(dbclass):
+    rand_part = base36encode(uuid4().int)
+    name = dbclass + '.' + rand_part
+    return name
+
+
 class ConnectionParser(object):
+
     def __init__(self, datasource_xml, version):
         self._dsxml = datasource_xml
         self._dsversion = version
@@ -116,6 +148,20 @@ def from_file(cls, filename):
         dsxml = xml_open(filename, cls.__name__.lower()).getroot()
         return cls(dsxml, filename)
 
+    @classmethod
+    def from_connections(cls, caption, connections):
+        root = ET.Element('datasource', caption=caption, version='10.0', inline='true')
+        outer_connection = ET.SubElement(root, 'connection')
+        outer_connection.set('class', 'federated')
+        named_conns = ET.SubElement(outer_connection, 'named-connections')
+        for conn in connections:
+            nc = ET.SubElement(named_conns,
+                               'named-connection',
+                               name=make_unique_name(conn.dbclass),
+                               caption=conn.server)
+            nc.append(conn._connectionXML)
+        return cls(root)
+
     def save(self):
         """
         Call finalization code and save file.
@@ -143,6 +189,7 @@ def save_as(self, new_filename):
             Nothing.
 
         """
+
         xfile._save_file(self._filename, self._datasourceTree, new_filename)
 
     ###########

tableaudocumentapi/xfile.py

@@ -104,6 +104,10 @@ def save_into_archive(xml_tree, filename, new_filename=None):
 
 
 def _save_file(container_file, xml_tree, new_filename=None):
+
+    if container_file is None:
+        container_file = new_filename
+
     if zipfile.is_zipfile(container_file):
         save_into_archive(xml_tree, container_file, new_filename)
     else:

test/bvt.py

@@ -74,6 +74,25 @@ def test_bad_dbclass_rasies_attribute_error(self):
         with self.assertRaises(AttributeError):
             conn.dbclass = 'NotReal'
 
+    def test_can_create_connection_from_scratch(self):
+        conn = Connection.from_attributes(
+            server='a', dbname='b', username='c', dbclass='mysql', authentication='d')
+        self.assertEqual(conn.server, 'a')
+        self.assertEqual(conn.dbname, 'b')
+        self.assertEqual(conn.username, 'c')
+        self.assertEqual(conn.dbclass, 'mysql')
+        self.assertEqual(conn.authentication, 'd')
+
+    def test_can_create_datasource_from_connections(self):
+        conn1 = Connection.from_attributes(
+            server='a', dbname='b', username='c', dbclass='mysql', authentication='d')
+        conn2 = Connection.from_attributes(
+            server='1', dbname='2', username='3', dbclass='mysql', authentication='7')
+        ds = Datasource.from_connections('test', connections=[conn1, conn2])
+
+        self.assertEqual(ds.connections[0].server, 'a')
+        self.assertEqual(ds.connections[1].server, '1')
+
 
 class DatasourceModelTests(unittest.TestCase):