proof of concept object oriented aproach

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>

oo.py

@@ -0,0 +1,242 @@
+import os
+import tempfile
+
+# FIXME: change these to match your environment
+os.environ['__cdist_base_dir'] = '/home/sar/vcs/cdist'
+# FIXME: testing against the cache, change path
+os.environ['__cdist_out_dir'] = '/home/sar/vcs/cdist/cache/sans-asteven-02.ethz.ch/out'
+
+
+'''
+cd /path/to/dir/with/this/file
+ipython
+
+
+In [1]: import oo
+
+In [2]: t = oo.Type('__mkfs')
+
+In [3]: t.
+t.base_dir             t.is_install           t.list_type_names      t.name                 t.path                 
+t.explorers            t.is_singleton         t.list_types           t.optional_parameters  t.required_parameters  
+
+In [3]: t.path
+Out[3]: '/home/sar/vcs/cdist/conf/type/__mkfs'
+
+In [4]: t.required_parameters
+Out[4]: ['type']
+
+In [5]: t.optional_parameters
+Out[5]: ['device', 'options', 'blocks']
+
+In [6]: t.is
+t.is_install    t.is_singleton  
+
+In [6]: t.is_singleton
+Out[6]: False
+
+In [7]: o = oo.Object(t, 'dev/sda1')
+
+In [8]: o.
+o.base_dir           o.list_object_names  o.list_type_names    o.parameter          o.qualified_name     o.type
+o.changed            o.list_objects       o.object_id          o.path               o.requirements       
+
+In [8]: o.pa
+o.parameter  o.path       
+
+In [8]: o.path
+Out[8]: '/home/sar/vcs/cdist/cache/sans-asteven-02.ethz.ch/out/object/__mkfs/dev/sda1/.cdist'
+
+In [9]: o.changed
+Out[9]: False
+
+In [10]: o.changed = True
+
+In [11]: # creates /home/sar/vcs/cdist/cache/sans-asteven-02.ethz.ch/out/object/__mkfs/dev/sda1/.cdist/changed
+
+In [12]: o.changed
+Out[12]: True
+
+In [13]: o.changed = False
+
+In [14]: # removes /home/sar/vcs/cdist/cache/sans-asteven-02.ethz.ch/out/object/__mkfs/dev/sda1/.cdist/changed
+
+In [15]:
+
+'''
+
+class Type(object):
+
+    @staticmethod
+    def base_dir():
+        """Return the absolute path to the top level directory where types
+        are defined.
+
+        Requires the environment variable '__cdist_base_dir' to be set.
+
+        """
+        return os.path.join(
+            os.environ['__cdist_base_dir'],
+            'conf',
+            'type'
+        )
+
+    @classmethod
+    def list_types(cls):
+        """Return a list of type instances"""
+        for type_name in cls.list_type_names():
+            yield cls(type_name)
+
+    @classmethod
+    def list_type_names(cls):
+        """Return a list of type names"""
+        return os.listdir(cls.base_dir())
+
+
+    def __init__(self, name):
+        self.name = name
+        self.__explorers = None
+        self.__required_parameters = None
+        self.__optional_parameters = None
+
+    def __repr__(self):
+        return '<Type name=%s>' % self.name
+
+    @property
+    def path(self):
+        return os.path.join(
+            self.base_dir(),
+            self.name
+        ) 
+
+    @property
+    def is_singleton(self):
+        """Check whether a type is a singleton."""
+        return os.path.isfile(os.path.join(self.path, "singleton"))
+
+    @property
+    def is_install(self):
+        """Check whether a type is used for installation (if not: for configuration)"""
+        return os.path.isfile(os.path.join(self.path, "install"))
+
+    @property
+    def explorers(self):
+        """Return a list of available explorers"""
+        if not self.__explorers:
+            try:
+                self.__explorers = os.listdir(os.path.join(self.path, "explorer"))
+            except EnvironmentError as e:
+                # error ignored
+                self.__explorers = []
+        return self.__explorers
+
+    @property
+    def required_parameters(self):
+        """Return a list of required parameters"""
+        if not self.__required_parameters:
+            parameters = []
+            try:
+                with open(os.path.join(self.path, "parameter", "required")) as fd:
+                    for line in fd:
+                        parameters.append(line.strip())
+            except EnvironmentError as e:
+                # error ignored
+                pass
+            finally:
+                self.__required_parameters = parameters
+        return self.__required_parameters
+
+    @property
+    def optional_parameters(self):
+        """Return a list of optional parameters"""
+        if not self.__optional_parameters:
+            parameters = []
+            try:
+                with open(os.path.join(self.path, "parameter", "optional")) as fd:
+                    for line in fd:
+                        parameters.append(line.strip())
+            except EnvironmentError as e:
+                # error ignored
+                pass
+            finally:
+                self.__optional_parameters = parameters
+        return self.__optional_parameters
+
+
+class Object(object):
+
+    @staticmethod
+    def base_dir():
+        """Return the absolute path to the top level directory where objects
+        are defined.
+
+        Requires the environment variable '__cdist_out_dir' to be set.
+
+        """
+        base_dir = os.path.join(
+            os.environ['__cdist_out_dir'],
+            'object'
+        )
+        # FIXME: should directory be created elsewhere?
+        if not os.path.isdir(base_dir):
+            os.mkdir(base_dir)
+        return base_dir
+
+    @classmethod
+    def list_objects(cls):
+        """Return a list of object instances"""
+        for object_name in cls.list_object_names():
+            type_name = object_name.split(os.sep)[0]
+            object_id = os.sep.join(object_name.split(os.sep)[1:])
+            yield cls(Type(type_name), object_id=object_id)
+
+    @classmethod
+    def list_type_names(cls):
+        """Return a list of type names"""
+        return os.listdir(cls.base_dir())
+
+    @classmethod
+    def list_object_names(cls):
+        """Return a list of object names"""
+        for path, dirs, files in os.walk(cls.base_dir()):
+            # FIXME: use constant instead of string
+            if '.cdist' in dirs:
+                yield os.path.relpath(path, cls.base_dir())
+
+    def __init__(self, type, object_id=None, parameter=None, requirements=None):
+        self.type = type # instance of Type
+        self.object_id = object_id
+        self.qualified_name = os.path.join(self.type.name, self.object_id)
+        self.parameter = parameter or {}
+        self.requirements = requirements or []
+        
+    def __repr__(self):
+        return '<Object %s>' % self.qualified_name
+
+    @property
+    def path(self):
+        return os.path.join(
+            self.base_dir(),
+            self.qualified_name,
+            '.cdist'
+        )
+
+    @property
+    def changed(self):
+        """Check whether the object has been changed."""
+        return os.path.isfile(os.path.join(self.path, "changed"))
+
+    @changed.setter
+    def changed(self, value):
+        """Change the objects changed status."""
+        path = os.path.join(self.path, "changed")
+        if value:
+            open(path, "w").close()
+        else:
+            try:
+                os.remove(path)
+            except EnvironmentError:
+                # ignore
+                pass
+
+    # FIXME: implement other properties/methods