Implement rudimentary module manager

This implements requirements 1 and 5 for the module management system.

5 files changed, 182 insertions, 3 deletions

diff --git a/doc/roadmap.rst b/doc/roadmap.rst
index 8bed427..d78f36d 100644
--- a/doc/roadmap.rst
+++ b/doc/roadmap.rst
@@ -6,10 +6,10 @@
 1.0 (2020 Q3)
 =============
 
-[ ] Module management system
+[/] Module management system
 ----------------------------
 
-* [ ] Track name/revision/namespace, and register with NSMAP
+* [X] Track name/revision/namespace, and register with NSMAP
 
   * Namespace includes prefix, since this is standardised.  i.e.
     ns "urn:ietf:params:xml:ns:yang:ietf-interfaces" -> prefix "if:".
@@ -20,7 +20,7 @@
 
 * [ ] Submodule support?  (possibly post-1.0)
 
-* [ ] Respond to state requests
+* [X] Respond to state requests
 
 
 The module management system will be the heart of ``ncserver``.  Similar to
diff --git a/ncserver/base/__init__.py b/ncserver/base/__init__.py
new file mode 100644
index 0000000..41c96db
--- /dev/null
+++ b/ncserver/base/__init__.py
@@ -0,0 +1,11 @@
+"""
+NETCONF for APK Distributions server:
+    Base functionality.
+
+Copyright © 2020 Adélie Software in the Public Benefit, Inc.
+
+Released under the terms of the NCSA license.  See the LICENSE file included
+with this source distribution for more information.
+
+SPDX-License-Identifier: NCSA
+"""
diff --git a/ncserver/base/modman.py b/ncserver/base/modman.py
new file mode 100644
index 0000000..551c1cd
--- /dev/null
+++ b/ncserver/base/modman.py
@@ -0,0 +1,143 @@
+"""
+NETCONF for APK Distributions server:
+    Module Management System
+
+Copyright © 2020 Adélie Software in the Public Benefit, Inc.
+
+Released under the terms of the NCSA license.  See the LICENSE file included
+with this source distribution for more information.
+
+SPDX-License-Identifier: NCSA
+"""
+
+import hashlib
+
+from logging import getLogger
+from netconf import nsmap_add, util
+from taillight import Signal
+
+from ncserver.base.util import _
+
+
+MODULE_SET_CHANGE_SIGNAL = Signal(('base/ModuleManager', 'module_set_changed'))
+"""Signal fired when the module set changes.  This implies the
+yang-library-change notification should be fired, when this is supported."""
+
+
+class ModuleManager:
+    """Manages the modules for the NETCONF for APK Distributions server.
+
+    :ivar modules:
+        Dictionary of loaded modules.
+
+    :ivar library:
+        Dictionary of loaded YANG models.
+    """
+
+    M_ABI_VERSION = 1
+    M_PREFIX = "yanglib"
+    M_NS = "urn:ietf:params:xml:ns:yang:ietf-yang-library"
+    M_NAME = "ietf-yang-library"
+    M_REVISION = "2019-01-04"
+
+    def __init__(self):
+        self.modules = {'ncserver.base.modman': self}
+        self.library = {'ncserver.base.modman':
+                        '{}@{}'.format(self.M_NAME, self.M_REVISION)}
+        nsmap_add(self.M_PREFIX, self.M_NS)
+        self.logger = getLogger('base/ModuleManager')
+
+    def load_module(self, name):
+        """Load a module.
+
+        :param str name:
+            The name of the module to load.
+
+        :returns:
+            Either the name of the module (if loaded), or None (on error).
+        """
+        if name in self.modules:
+            self.logger.warning(_("Module '%s' is already loaded; skipping"),
+                                name)
+            return name
+
+        self.logger.debug(_("Discovering module '%s'..."), name)
+
+        mod = None
+        try:
+            mod = __import__(name, globals(), locals(), [name], 0)
+        except ImportError:
+            self.logger.error(_("Module '%s' was not found."), name)
+            return None
+
+        if any([getattr(mod, attr, None) is None
+                for attr in ['M_ABI_VERSION', 'M_NS', 'M_PREFIX', 'M_NAME']]):
+            self.logger.error(_("'%s' is not a valid module."), name)
+            return None
+
+        if mod.M_ABI_VERSION != 1:
+            self.logger.error(_("Module '%s' requires ABI version %d."), name,
+                              mod.M_ABI_VERSION)
+            return None
+
+        self.logger.info(_("Loading module '%s' with ABI %d for namespace %s"),
+                         name, mod.M_ABI_VERSION, mod.M_NS)
+
+        self.modules[name] = mod
+        self.library[name] = '{}@{}'.format(mod.M_NAME, mod.M_REVISION)
+        nsmap_add(mod.M_PREFIX, mod.M_NS)
+        return name
+
+    def running(self, node):
+        """Return running configuration information."""
+        # ietf-yang-library is state-only.
+
+    def operational(self, node):
+        """Return configuration and device state information."""
+        module_set_id = hashlib.sha256(','.join(self.modules.keys()).encode())
+        content_id = module_set_id.hexdigest()
+
+        # NDMA-enabled yang-library node.
+        lib = util.subelm(node, 'yanglib:yang-library')
+        modset = util.subelm(lib, 'yanglib:module-set')
+        modset.append(util.leaf_elm('yanglib:name', 'netconfapk'))
+        for module in self.modules.values():
+            # XXX or import-only-module, if it's import-only
+            modnode = util.subelm(modset, 'yanglib:module')
+            modnode.append(util.leaf_elm('yanglib:name', module.M_NAME))
+            modnode.append(util.leaf_elm('yanglib:revision',
+                                         module.M_REVISION))
+            modnode.append(util.leaf_elm('yanglib:namespace', module.M_NS))
+        schema = util.subelm(lib, 'yanglib:schema')
+        schema.append(util.leaf_elm('yanglib:name', 'apkschema'))
+        schema.append(util.leaf_elm('yanglib:module-set', 'netconfapk'))
+
+        for store in ['running', 'operational']:
+            dsnode = util.subelm(lib, 'yanglib:datastore')
+            dsnode.append(util.leaf_elm('name', store))
+            dsnode.append(util.leaf_elm('schema', 'apkschema'))
+
+        lib.append(util.leaf_elm('yanglib:content-id', content_id))
+
+        # Deprecated modules-state node.
+        modstate = util.subelm(node, 'yanglib:modules-state')
+        modstate.append(util.leaf_elm('yanglib:module-set-id', content_id))
+        for module in self.modules.values():
+            modnode = util.subelm(modstate, 'yanglib:module')
+            modnode.append(util.leaf_elm('yanglib:name', module.M_NAME))
+            modnode.append(util.leaf_elm('yanglib:revision',
+                                         module.M_REVISION))
+            modnode.append(util.leaf_elm('yanglib:namespace', module.M_NS))
+            # XXX import-only module support: use 'import'
+            modnode.append(util.leaf_elm('yanglib:conformance-type',
+                                         'implement'))
+
+    def collect_running(self, node):
+        """Collect all available information for the <running> datastore."""
+        for mod in self.modules.values():
+            mod.running(node)
+
+    def collect_operational(self, node):
+        """Collect all available information for the <operational> datastore"""
+        for mod in self.modules.values():
+            mod.operational(node)
diff --git a/ncserver/base/util.py b/ncserver/base/util.py
new file mode 100644
index 0000000..3df076c
--- /dev/null
+++ b/ncserver/base/util.py
@@ -0,0 +1,18 @@
+"""
+NETCONF for APK Distributions server:
+    Base utility functions.
+
+Copyright © 2020 Adélie Software in the Public Benefit, Inc.
+
+Released under the terms of the NCSA license.  See the LICENSE file included
+with this source distribution for more information.
+
+SPDX-License-Identifier: NCSA
+"""
+
+
+def _(the_string):
+    """Translate a user-facing string.
+
+    Currently not implemented, but allows us to implement translation later."""
+    return the_string
diff --git a/print_operational.py b/print_operational.py
new file mode 100644
index 0000000..828075f
--- /dev/null
+++ b/print_operational.py
@@ -0,0 +1,7 @@
+from lxml import etree as et
+from ncserver.base.modman import ModuleManager
+from netconf.util import elm
+mgr = ModuleManager()
+node = elm('nc:data')
+mgr.collect_operational(node)
+print(et.tostring(node, pretty_print=True).decode())