import sys
from datetime import UTC, datetime
from pathlib import Path
from types import ModuleType
from uuid import UUID

import msgspec

from kanta import ChangeRecord, Kanta


class User(msgspec.Struct):
    name: str = ""
    age: int = 0


class Data(msgspec.Struct):
    users: dict[str, User] = {}
    counter: int = 0


class ExoticData(msgspec.Struct, omit_defaults=False):
    uuid_values: dict[str, UUID] = {}
    uuid_keys: dict[UUID, int] = {}
    datetime_values: dict[str, datetime] = {}
    datetime_keys: dict[datetime, int] = {}
    bytes_values: dict[str, bytes] = {}
    bytes_keys: dict[bytes, int] = {}


class EvolvableDataV1(msgspec.Struct, omit_defaults=False):
    counter: int = 0


class EvolvableDataV2(msgspec.Struct, omit_defaults=False):
    counter: int = 0
    enabled: bool = True


def make_kanta(path: Path, data_or_type, format_config, **kwargs):
    _, serializer_cls = format_config
    root = data_or_type() if isinstance(data_or_type, type) else data_or_type
    return Kanta(
        str(path),
        root,
        serializer=serializer_cls(),
        **kwargs,
    )


def seed_single_change(path: Path, change: ChangeRecord, format_config) -> None:
    _, serializer_cls = format_config
    serializer = serializer_cls()
    framer = serializer.framer_cls()
    payload = serializer.encode(change)
    path.write_bytes(framer.frame_change(payload, record_offset=0))


def change_actions(path: Path, format_config) -> list[str]:
    _, serializer_cls = format_config
    serializer = serializer_cls()
    framer = serializer.framer_cls()
    actions: list[str] = []
    for is_snapshot, payload, _, _ in framer.iter_records(path.read_bytes(), 0):
        if is_snapshot:
            continue
        rec = serializer.decode(payload, type=ChangeRecord)
        actions.append(rec.a)
    return actions


def make_migrations_module(name: str, fn_name: str, fn):
    mod = ModuleType(name)
    mod.__dict__[fn_name] = fn
    sys.modules[name] = mod
    return mod


def fixed_change(action: str, diff: dict, *, version: int = 0) -> ChangeRecord:
    return ChangeRecord(
        ts=datetime(2026, 1, 1, tzinfo=UTC), a=action, v=version, diff=diff
    )