sambacc: add smbconf_api module for abstract smbconf operations

The smbconf library provided by Samba allows python code to interact
with Samba's configuration backends. Before adding a module that
uses those libraries directly add a module that provides general
abstractions and interfaces in that vein.

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

sambacc/smbconf_api.py

@@ -0,0 +1,73 @@
+#
+# sambacc: a samba container configuration tool
+# Copyright (C) 2023  John Mulligan
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>
+#
+
+import typing
+
+
+class ConfigStore(typing.Protocol):
+    def __getitem__(self, name: str) -> list[tuple[str, str]]:
+        ...  # pragma: no cover
+
+    def __setitem__(self, name: str, value: list[tuple[str, str]]) -> None:
+        ...  # pragma: no cover
+
+    def __iter__(self) -> typing.Iterator[str]:
+        ...  # pragma: no cover
+
+
+class SimpleConfigStore:
+    def __init__(self) -> None:
+        self._data: dict[str, list[tuple[str, str]]] = {}
+
+    @property
+    def writeable(self) -> bool:
+        """True if using a read-write backend."""
+        return True
+
+    def __getitem__(self, name: str) -> list[tuple[str, str]]:
+        return self._data[name]
+
+    def __setitem__(self, name: str, value: list[tuple[str, str]]) -> None:
+        self._data[name] = value
+
+    def __iter__(self) -> typing.Iterator[str]:
+        return iter(self._data.keys())
+
+    def import_smbconf(
+        self, src: ConfigStore, batch_size: typing.Optional[int] = None
+    ) -> None:
+        """Import content from one SMBConf configuration object into the
+        current SMBConf configuration object.
+
+        batch_size is ignored.
+        """
+        for sname in src:
+            self[sname] = src[sname]
+
+
+def write_store_as_smb_conf(out: typing.IO, conf: ConfigStore) -> None:
+    """Write the configuration store in smb.conf format to `out`."""
+    # unfortunately, AFAIK, there's no way for an smbconf to write
+    # into a an smb.conf/ini style file. We have to do it on our own.
+    # ---
+    # Make sure global section comes first.
+    sections = sorted(conf, key=lambda v: 0 if v == "global" else 1)
+    for sname in sections:
+        out.write(str("\n[{}]\n".format(sname)))
+        for skey, sval in conf[sname]:
+            out.write(str(f"\t{skey} = {sval}\n"))