--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libervia/backend/tools/common/data_format.py	Fri Jun 02 11:49:51 2023 +0200
@@ -0,0 +1,153 @@
+#!/usr/bin/env python3
+
+
+# SAT: a jabber client
+# Copyright (C) 2009-2021 Jérôme Poisson (goffi@goffi.org)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero 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 Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+""" tools common to backend and frontends """
+#  FIXME: json may be more appropriate than manual serialising like done here
+
+from typing import Any
+
+from libervia.backend.core import exceptions
+import json
+
+
+def dict2iter(name, dict_, pop=False):
+    """iterate into a list serialised in a dict
+
+    name is the name of the key.
+    Serialisation is done with [name] [name#1] [name#2] and so on
+    e.g.: if name is 'group', keys are group, group#1, group#2, ...
+    iteration stop at first missing increment
+    Empty values are possible
+    @param name(unicode): name of the key
+    @param dict_(dict): dictionary with the serialised list
+    @param pop(bool): if True, remove the value from dict
+    @return iter: iterate through the deserialised list
+    """
+    if pop:
+        get = lambda d, k: d.pop(k)
+    else:
+        get = lambda d, k: d[k]
+
+    try:
+        yield get(dict_, name)
+    except KeyError:
+        return
+    else:
+        idx = 1
+        while True:
+            try:
+                yield get(dict_, "{}#{}".format(name, idx))
+            except KeyError:
+                return
+            else:
+                idx += 1
+
+
+def dict2iterdict(name, dict_, extra_keys, pop=False):
+    """like dict2iter but yield dictionaries
+
+    params are like in [dict2iter], extra_keys is used for extra dict keys.
+    e.g. dict2iterdict(comments, mb_data, ('node', 'service')) will yield dicts like:
+        {u'comments': u'value1', u'node': u'value2', u'service': u'value3'}
+    """
+    #  FIXME: this format seem overcomplicated, it may be more appropriate to use json here
+    if pop:
+        get = lambda d, k: d.pop(k)
+    else:
+        get = lambda d, k: d[k]
+    for idx, main_value in enumerate(dict2iter(name, dict_, pop=pop)):
+        ret = {name: main_value}
+        for k in extra_keys:
+            ret[k] = get(
+                dict_, "{}{}_{}".format(name, ("#" + str(idx)) if idx else "", k)
+            )
+        yield ret
+
+
+def iter2dict(name, iter_, dict_=None, check_conflict=True):
+    """Fill a dict with values from an iterable
+
+    name is used to serialise iter_, in the same way as in [dict2iter]
+    Build from the tags a dict using the microblog data format.
+
+    @param name(unicode): key to use for serialisation
+        e.g. "group" to have keys "group", "group#1", "group#2", ...
+    @param iter_(iterable): values to store
+    @param dict_(None, dict): dictionary to fill, or None to create one
+    @param check_conflict(bool): if True, raise an exception in case of existing key
+    @return (dict): filled dict, or newly created one
+    @raise exceptions.ConflictError: a needed key already exists
+    """
+    if dict_ is None:
+        dict_ = {}
+    for idx, value in enumerate(iter_):
+        if idx == 0:
+            key = name
+        else:
+            key = "{}#{}".format(name, idx)
+        if check_conflict and key in dict_:
+            raise exceptions.ConflictError
+        dict_[key] = value
+    return dict
+
+
+def get_sub_dict(name, dict_, sep="_"):
+    """get a sub dictionary from a serialised dictionary
+
+    look for keys starting with name, and create a dict with it
+    eg.: if "key" is looked for, {'html': 1, 'key_toto': 2, 'key_titi': 3} will return:
+        {None: 1, toto: 2, titi: 3}
+    @param name(unicode): name of the key
+    @param dict_(dict): dictionary with the serialised list
+    @param sep(unicode): separator used between name and subkey
+    @return iter: iterate through the deserialised items
+    """
+    for k, v in dict_.items():
+        if k.startswith(name):
+            if k == name:
+                yield None, v
+            else:
+                if k[len(name)] != sep:
+                    continue
+                else:
+                    yield k[len(name) + 1 :], v
+
+def serialise(data):
+    """Serialise data so it can be sent to bridge
+
+    @return(unicode): serialised data, can be transmitted as string to the bridge
+    """
+    return json.dumps(data, ensure_ascii=False, default=str)
+
+def deserialise(serialised_data: str, default: Any = None, type_check: type = dict):
+    """Deserialize data from bridge
+
+    @param serialised_data(unicode): data to deserialise
+    @default (object): value to use when serialised data is empty string
+    @param type_check(type): if not None, the deserialised data must be of this type
+    @return(object): deserialised data
+    @raise ValueError: serialised_data is of wrong type
+    """
+    if serialised_data == "":
+        return default
+    ret = json.loads(serialised_data)
+    if type_check is not None and not isinstance(ret, type_check):
+        raise ValueError("Bad data type, was expecting {type_check}, got {real_type}"
+            .format(type_check=type_check, real_type=type(ret)))
+    return ret