new module appconfig.py

gluon/contrib/appconfig.py

@@ -0,0 +1,123 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+"""
+Read from configuration files easily without hurting performances
+
+USAGE:
+During development you can load a config file either in .ini or .json
+format (by default app/private/appconfig.ini or app/private/appconfig.json)
+The result is a dict holding the configured values. Passing reload=True
+is meant only for development: in production, leave reload to False and all
+values will be cached
+
+from gluon.contrib.appconfig import AppConfig
+myconfig = AppConfig(path_to_configfile, reload=False)
+
+print myconfig['db']['uri']
+
+The returned dict can walk with "dot notation" an arbitrarely nested dict
+
+print myconfig.take('db.uri')
+
+You can even pass a cast function, i.e.
+
+print myconfig.take('auth.expiration', cast=int)
+
+Once the value has been fetched (and casted) it won't change until the process
+is restarted (or reload=True is passed).
+
+"""
+import thread
+import os
+from ConfigParser import SafeConfigParser
+from gluon import current
+from gluon.serializers import json_parser
+
+locker = thread.allocate_lock()
+
+
+def AppConfig(*args, **vars):
+
+    locker.acquire()
+    reload_ = vars.pop('reload', False)
+    try:
+        instance_name = 'AppConfig_' + current.request.application
+        if reload_ or not hasattr(AppConfig, instance_name):
+            setattr(AppConfig, instance_name, AppConfigLoader(*args, **vars))
+        return getattr(AppConfig, instance_name).settings
+    finally:
+        locker.release()
+
+
+class AppConfigDict(dict):
+    """
+    dict that has a .take() method to fetch nested values and puts
+    them into cache
+    """
+
+    def __init__(self, *args, **kwargs):
+        dict.__init__(self, *args, **kwargs)
+        self.int_cache = {}
+
+    def take(self, path, cast=None):
+        parts = path.split('.')
+        if path in self.int_cache:
+            return self.int_cache[path]
+        value = self
+        walking = []
+        for part in parts:
+            if part not in value:
+                raise BaseException("%s not in config [%s]" %
+                    (part, '-->'.join(walking)))
+            value = value[part]
+            walking.append(part)
+        if cast is None:
+            self.int_cache[path] = value
+        else:
+            try:
+                value = cast(value)
+                self.int_cache[path] = value
+            except (ValueError, TypeError):
+                raise BaseException("%s can't be converted to %s" %
+                 (value, cast))
+        return value
+
+
+class AppConfigLoader(object):
+
+    def __init__(self, configfile=None):
+        if not configfile:
+            priv_folder = os.path.join(current.request.folder, 'private')
+            configfile = os.path.join(priv_folder, 'appconfig.ini')
+            if not os.path.isfile(configfile):
+                configfile = os.path.join(priv_folder, 'appconfig.json')
+                if not os.path.isfile(configfile):
+                    configfile = None
+        if not configfile or not os.path.isfile(configfile):
+            raise BaseException("Config file not found")
+        self.file = configfile
+        self.ctype = os.path.splitext(configfile)[1][1:]
+        self.settings = None
+        self.read_config()
+
+    def read_config_ini(self):
+        config = SafeConfigParser()
+        config.read(self.file)
+        settings = {}
+        for section in config.sections():
+            settings[section] = {}
+            for option in config.options(section):
+                settings[section][option] = config.get(section, option)
+        self.settings = AppConfigDict(settings)
+
+    def read_config_json(self):
+        with open(self.file, 'r') as c:
+            self.settings = AppConfigDict(json_parser.load(c))
+
+    def read_config(self):
+        if self.settings is None:
+            try:
+                getattr(self, 'read_config_' + self.ctype)()
+            except AttributeError:
+                raise BaseException("Unsupported config file format")
+        return self.settings

gluon/tests/test_contribs.py

@@ -4,14 +4,24 @@
 """ Unit tests for contribs """
 
 import unittest
+import os
 from fix_path import fix_sys_path
 
 fix_sys_path(__file__)
 
+from gluon.storage import Storage
+import gluon.contrib.fpdf as fpdf
+import gluon.contrib.pyfpdf as pyfpdf
+from gluon.contrib.appconfig import AppConfig
 
-from utils import md5_hash
-import contrib.fpdf as fpdf
-import contrib.pyfpdf as pyfpdf
+
+def setUpModule():
+    pass
+
+
+def tearDownModule():
+    if os.path.isfile('appconfig.json'):
+        os.unlink('appconfig.json')
 
 
 class TestContribs(unittest.TestCase):
@@ -35,6 +45,28 @@ class TestContribs(unittest.TestCase):
         self.assertTrue(fpdf.FPDF_VERSION in pdf_out, 'version string')
         self.assertTrue('hello world' in pdf_out, 'sample message')
 
+    def test_appconfig(self):
+        """
+        Test for the appconfig module
+        """
+        from gluon import current
+        s = Storage({'application': 'admin',
+                     'folder': 'applications/admin'})
+        current.request = s
+        simple_config = '{"config1" : "abc", "config2" : "bcd", "config3" : { "key1" : 1, "key2" : 2} }'
+        with open('appconfig.json', 'w') as g:
+            g.write(simple_config)
+        myappconfig = AppConfig('appconfig.json')
+        self.assertEqual(myappconfig['config1'], 'abc')
+        self.assertEqual(myappconfig['config2'], 'bcd')
+        self.assertEqual(myappconfig.take('config1'), 'abc')
+        self.assertEqual(myappconfig.take('config3.key1', cast=str), '1')
+        # once parsed, can't be casted to other types
+        self.assertEqual(myappconfig.take('config3.key1', cast=int), '1')
+
+        self.assertEqual(myappconfig.take('config3.key2'), 2)
+        
+        current.request = {}
 
 if __name__ == '__main__':
     unittest.main()