Tools to diff data

diff.py

"""
Copyright 2024 Dustin Oprea

MIT LICENSE

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
"""

def dynamic_retrieve(cached_entities, want_ids, entities_getter):
    """Retrieve the entities that we don't yet have.

    `cached_entities`: A dictionary of IDs to entities. It will start as an
    empty dictionary but will fill over time between successive calls.

    `want_ids`: A list of IDs

    `entities_getter`:
        A callback that takes a list of ID and returns a list/generator of 2-
        tuples of IDs and entities
    """

# TODO(dustin): Add test

    final_entities = {}
    missing_entity_ids = []
    for id_ in want_ids:
        try:
            entity = cached_entities[id_]
        except KeyError:
            pass
        else:
            final_entities[id_] = entity
            continue

        missing_entity_ids.append(id_)

    if missing_entity_ids:
        retrieved_entities = entities_getter(missing_entity_ids)

        for id_, entity in retrieved_entities:
            cached_entities[id_] = entity
            final_entities[id_] = entity

    return final_entities


def compare_lists(a, b):

    a_s = set(a)
    b_s = set(b)

    created_s = b_s - a_s
    removed_s = a_s - b_s
    unchanged_s = a_s & b_s

    return list(created_s), list(removed_s), list(unchanged_s)

def compare_dictionaries(a, b):

    a_list = [
        tuple(pair)
        for pair
        in a.items()
    ]

    b_list = [
        tuple(pair)
        for pair
        in b.items()
    ]

    created_list, removed_list, unchanged_list = compare_lists(a_list, b_list)


    # Results will be dictionaries

    created = dict(created_list)
    removed = dict(removed_list)
    unchanged = dict(unchanged_list)


    # Determine changed members

    changed_list = set(created.keys()) & set(removed.keys())

    changed = {}
    if changed_list:
        for changed_key in changed_list:
            changed[changed_key] = (removed[changed_key], created[changed_key])

            del removed[changed_key]
            del created[changed_key]


    return created, removed, changed, unchanged