1from __future__ import annotations
 2
 3from ..._utils import is_dict, is_list
 4
 5
 6def accumulate_delta(acc: dict[object, object], delta: dict[object, object]) -> dict[object, object]:
 7    for key, delta_value in delta.items():
 8        if key not in acc:
 9            acc[key] = delta_value
10            continue
11
12        acc_value = acc[key]
13        if acc_value is None:
14            acc[key] = delta_value
15            continue
16
17        # the `index` property is used in arrays of objects so it should
18        # not be accumulated like other values e.g.
19        # [{'foo': 'bar', 'index': 0}]
20        #
21        # the same applies to `type` properties as they're used for
22        # discriminated unions
23        if key == "index" or key == "type":
24            acc[key] = delta_value
25            continue
26
27        if isinstance(acc_value, str) and isinstance(delta_value, str):
28            acc_value += delta_value
29        elif isinstance(acc_value, (int, float)) and isinstance(delta_value, (int, float)):
30            acc_value += delta_value
31        elif is_dict(acc_value) and is_dict(delta_value):
32            acc_value = accumulate_delta(acc_value, delta_value)
33        elif is_list(acc_value) and is_list(delta_value):
34            # for lists of non-dictionary items we'll only ever get new entries
35            # in the array, existing entries will never be changed
36            if all(isinstance(x, (str, int, float)) for x in acc_value):
37                acc_value.extend(delta_value)
38                continue
39
40            for delta_entry in delta_value:
41                if not is_dict(delta_entry):
42                    raise TypeError(f"Unexpected list delta entry is not a dictionary: {delta_entry}")
43
44                try:
45                    index = delta_entry["index"]
46                except KeyError as exc:
47                    raise RuntimeError(f"Expected list delta entry to have an `index` key; {delta_entry}") from exc
48
49                if not isinstance(index, int):
50                    raise TypeError(f"Unexpected, list delta entry `index` value is not an integer; {index}")
51
52                try:
53                    acc_entry = acc_value[index]
54                except IndexError:
55                    acc_value.insert(index, delta_entry)
56                else:
57                    if not is_dict(acc_entry):
58                        raise TypeError("not handled yet")
59
60                    acc_value[index] = accumulate_delta(acc_entry, delta_entry)
61
62        acc[key] = acc_value
63
64    return acc