Pushing internal layer configuration to a static prepareKeywordArgs()…

… method of provider classes, starting with Proxy, UrlTemplate and Sandwich providers

TileStache/Config.py

@@ -426,17 +426,6 @@ def _parseConfigfileLayer(layer_dict, config, dirpath):
             provider_kwargs['mapfile'] = provider_dict['mapfile']
             provider_kwargs['fonts'] = provider_dict.get('fonts', None)
 
-        elif _class is Providers.Proxy:
-            if 'url' in provider_dict:
-                provider_kwargs['url'] = provider_dict['url']
-            if 'provider' in provider_dict:
-                provider_kwargs['provider_name'] = provider_dict['provider']
-
-        elif _class is Providers.UrlTemplate:
-            provider_kwargs['template'] = provider_dict['template']
-            if 'referer' in provider_dict:
-                provider_kwargs['referer'] = provider_dict['referer']
-
         elif _class is Providers.Vector.Provider:
             provider_kwargs['driver'] = provider_dict['driver']
             provider_kwargs['parameters'] = provider_dict['parameters']
@@ -472,8 +461,8 @@ def _parseConfigfileLayer(layer_dict, config, dirpath):
             if 'layer id key' in provider_dict:
                 provider_kwargs['layer_id_key'] = provider_dict['layer id key']
 
-        elif str(_class) == 'TileStache.Sandwich.Provider':
-            provider_kwargs['stack'] = provider_dict['stack']
+        elif hasattr(_class, 'prepareKeywordArgs'):
+            provider_kwargs.update(_class.prepareKeywordArgs(provider_dict))
 
     elif 'class' in provider_dict:
         _class = loadClassPath(provider_dict['class'])

TileStache/Providers.py

@@ -90,19 +90,22 @@
 import Vector
 import MBTiles
 import Geography
-from .Mapnik import ImageProvider as MapnikImage, GridProvider as MapnikGrid
 
 # Already deprecated; provided for temporary backward-compatibility with
 # old location of Mapnik provider. TODO: remove in next major version.
-Mapnik = MapnikImage
+try:
+    from .Mapnik import ImageProvider as Mapnik
+except ImportError:
+    pass
 
 def getProviderByName(name):
     """ Retrieve a provider object by name.
     
         Raise an exception if the name doesn't work out.
     """
     if name.lower() == 'mapnik':
-        return MapnikImage
+        from .Mapnik import ImageProvider
+        return ImageProvider
 
     elif name.lower() == 'proxy':
         return Proxy
@@ -117,7 +120,8 @@ def getProviderByName(name):
         return MBTiles.Provider
 
     elif name.lower() == 'mapnik grid':
-        return MapnikGrid
+        from .Mapnik import GridProvider
+        return GridProvider
 
     elif name.lower() == 'sandwich':
         import Sandwich
@@ -164,6 +168,20 @@ def __init__(self, layer, url=None, provider_name=None):
         else:
             raise Exception('Missing required url or provider parameter to Proxy provider')
 
+    @staticmethod
+    def prepareKeywordArgs(config_dict):
+        '''
+        '''
+        kwargs = dict()
+
+        if 'url' in config_dict:
+            kwargs['url'] = config_dict['url']
+
+        if 'provider' in config_dict:
+            kwargs['provider_name'] = config_dict['provider']
+
+        return kwargs
+
     def renderTile(self, width, height, srs, coord):
         """
         """
@@ -222,6 +240,17 @@ def __init__(self, layer, template, referer=None):
         self.template = Template(template)
         self.referer = referer
 
+    @staticmethod
+    def prepareKeywordArgs(config_dict):
+        '''
+        '''
+        kwargs = {'template': config_dict['template']}
+
+        if 'referer' in config_dict:
+            kwargs['referer'] = config_dict['referer']
+
+        return kwargs
+
     def renderArea(self, width, height, srs, xmin, ymin, xmax, ymax, zoom):
         """ Return an image for an area.
         

TileStache/Sandwich.py

@@ -143,6 +143,12 @@ def __init__(self, layer, stack):
         self.config = layer.config
         self.stack = stack
 
+    @staticmethod
+    def prepareKeywordArgs(config_dict):
+        '''
+        '''
+        return {'stack': config_dict['stack']}
+
     def renderTile(self, width, height, srs, coord):
 
         rendered = draw_stack(self.stack, coord, self.config, dict())