import json
from dataclasses import dataclass, field
from dataclasses import fields as _fields
from datetime import datetime, timezone
from functools import partial
from types import UnionType
from typing import (
    Annotated,
    Any,
    ClassVar,
    Container,
    Literal,
    Mapping,
    Type,
    TypeVar,
    Union,
    get_args,
    get_origin,
)

from .types import ULID

JSON = int | float | str | None | list["JSON"] | dict[str, "JSON"]
JSONObject = dict[str, JSON]

T = TypeVar("T")


def annotations(tp: Type) -> tuple | None:
    return tp.__metadata__ if hasattr(tp, "__metadata__") else None


def fields(class_or_instance):
    """Like dataclass' `fields` but with extra support for our models.

    This function is a drop-in replacement for dataclass' `fields` and
    SHOULD be used instead of it everywhere.
    This function filters out fields marked as `Relation`.  `Relation`
    fields are meant to allow to store the data referenced by an ID field
    directly on the instance.
    """

    # XXX this might be a little slow (not sure), if so, memoize

    for f in _fields(class_or_instance):
        if f.name == "_is_lazy":
            continue

        if (attn := annotations(f.type)) and _RelationSentinel in attn:
            continue  # Relations are ignored

        yield f


def is_optional(tp: Type) -> bool:
    """Return wether the given type is optional."""
    if not isinstance(tp, UnionType) and get_origin(tp) is not Union:
        return False

    args = get_args(tp)
    return len(args) == 2 and type(None) in args


def optional_type(tp: Type) -> Type | None:
    """Return the wrapped type from an optional type.

    For example this will return `int` for `Optional[int]`.
    Since they're equivalent this also works for other optioning notations, like
    `Union[int, None]` and `int | None`.
    """
    if not isinstance(tp, UnionType) and get_origin(tp) is not Union:
        return None

    args = get_args(tp)
    if len(args) != 2 or type(None) not in args:
        return None

    return args[0] if args[1] is type(None) else args[1]


def optional_fields(o):
    for f in fields(o):
        if is_optional(f.type):
            yield f


json_dump = partial(json.dumps, separators=(",", ":"))


def _id(x: T) -> T:
    return x


def asplain(
    o: object, *, filter_fields: Container[str] | None = None, serialize: bool = False
) -> dict[str, Any]:
    """Return the given model instance as `dict` with JSON compatible plain datatypes.

    If `filter_fields` is given only matching field names will be included in
    the resulting `dict`.
    If `serialize` is `True`, collection types (lists, dicts, etc.) will be
    serialized as strings; this can be useful to store them in a database. Be
    sure to set `serialized=True` when using `fromplain` to successfully restore
    the object.
    """
    validate(o)

    dump = json_dump if serialize else _id

    d: JSONObject = {}
    for f in fields(o):
        if filter_fields is not None and f.name not in filter_fields:
            continue

        target = f.type
        # XXX this doesn't properly support any kind of nested types
        if (otype := optional_type(f.type)) is not None:
            target = otype
        if (otype := get_origin(target)) is not None:
            target = otype

        v = getattr(o, f.name)
        if is_optional(f.type) and v is None:
            d[f.name] = None
        elif target is ULID:
            assert isinstance(v, ULID)
            d[f.name] = str(v)
        elif target in {datetime}:
            assert isinstance(v, datetime)
            d[f.name] = v.isoformat()
        elif target in {set}:
            assert isinstance(v, set)
            d[f.name] = dump(list(sorted(v)))
        elif target in {list}:
            assert isinstance(v, list)
            d[f.name] = dump(list(v))
        elif target in {bool, str, int, float}:
            assert isinstance(
                v, target
            ), f"Type mismatch: {f.name} ({target} != {type(v)})"
            d[f.name] = v
        else:
            raise ValueError(f"Unsupported value type: {f.name}: {type(v)}")

    return d


def fromplain(cls: Type[T], d: Mapping, *, serialized: bool = False) -> T:
    """Return an instance of the given model using the given data.

    If `serialized` is `True`, collection types (lists, dicts, etc.) will be
    deserialized from string. This is the opposite operation of `serialize` for
    `asplain`.
    """
    load = json.loads if serialized else _id

    dd: JSONObject = {}
    for f in fields(cls):
        target = f.type
        otype = optional_type(f.type)
        is_opt = otype is not None
        if is_opt:
            target = otype
        if (xtype := get_origin(target)) is not None:
            target = xtype

        v = d[f.name]
        if is_opt and v is None:
            dd[f.name] = v
        elif isinstance(v, target):
            dd[f.name] = v
        elif target in {set, list}:
            dd[f.name] = target(load(v))
        elif target in {datetime}:
            dd[f.name] = target.fromisoformat(v)
        else:
            dd[f.name] = target(v)

    o = cls(**dd)
    validate(o)
    return o


def validate(o: object) -> None:
    for f in fields(o):
        vtype = type(getattr(o, f.name))
        if vtype is not f.type:
            if get_origin(f.type) is vtype or (
                (isinstance(f.type, UnionType) or get_origin(f.type) is Union)
                and vtype in get_args(f.type)
            ):
                continue
            raise ValueError(f"Invalid value type: {f.name}: {vtype}")


def utcnow():
    return datetime.utcnow().replace(tzinfo=timezone.utc)


@dataclass
class Progress:
    _table: ClassVar[str] = "progress"

    id: ULID = field(default_factory=ULID)
    type: str = None
    state: str = None
    started: datetime = field(default_factory=utcnow)
    stopped: str | None = None

    @property
    def _state(self) -> dict:
        return json.loads(self.state or "{}")

    @_state.setter
    def _state(self, state: dict):
        self.state = json_dump(state)

    @property
    def percent(self) -> float:
        return self._state["percent"]

    @percent.setter
    def percent(self, percent: float):
        state = self._state
        state["percent"] = percent
        self._state = state

    @property
    def error(self) -> str:
        return self._state.get("error", "")

    @error.setter
    def error(self, error: str):
        state = self._state
        state["error"] = error
        self._state = state


@dataclass
class Movie:
    _table: ClassVar[str] = "movies"

    id: ULID = field(default_factory=ULID)
    title: str = None  # canonical title (usually English)
    original_title: str | None = (
        None  # original title (usually transscribed to latin script)
    )
    release_year: int = None  # canonical release date
    media_type: str = None
    imdb_id: str = None
    imdb_score: int | None = None  # range: [0,100]
    imdb_votes: int | None = None
    runtime: int | None = None  # minutes
    genres: set[str] = None
    created: datetime = field(default_factory=utcnow)
    updated: datetime = field(default_factory=utcnow)

    _is_lazy: bool = field(default=False, init=False, repr=False, compare=False)

    @classmethod
    def lazy(cls, **kwds):
        """Return a new instance without running default factories.

        This is meant purely for optimization purposes, to postpone possibly
        expensive initialization operations.
        """
        # XXX optimize using a metaclass & storing field refs on the class
        kwds.setdefault("id", None)
        kwds.setdefault("created", None)
        kwds.setdefault("updated", None)
        movie = cls(**kwds)
        movie._is_lazy = True
        return movie

    def _lazy_init(self):
        if not self._is_lazy:
            return

        for field in fields(Movie):
            if getattr(self, field.name) is None and callable(field.default_factory):
                setattr(self, field.name, field.default_factory())

        self._is_lazy = False


_RelationSentinel = object()
"""Mark a model field as containing external data.

For each field marked as a Relation there should be another field on the
dataclass containing the ID of the linked data.
The contents of the Relation are ignored or discarded when using
`asplain`, `fromplain`, and `validate`.
"""
Relation = Annotated[T | None, _RelationSentinel]


@dataclass
class Rating:
    _table: ClassVar[str] = "ratings"

    id: ULID = field(default_factory=ULID)

    movie_id: ULID = None
    movie: Relation[Movie] = None

    user_id: ULID = None
    user: Relation["User"] = None

    score: int = None  # range: [0,100]
    rating_date: datetime = None
    favorite: bool | None = None
    finished: bool | None = None

    def __eq__(self, other):
        """Return wether two Ratings are equal.

        This operation compares all fields as expected, except that it
        ignores any field marked as Relation.
        """
        if type(other) is not type(self):
            return False
        return all(
            getattr(self, f.name) == getattr(other, f.name) for f in fields(self)
        )


Access = Literal[
    "r",  # read
    "i",  # index
    "w",  # write
]


@dataclass
class User:
    _table: ClassVar[str] = "users"

    id: ULID = field(default_factory=ULID)
    imdb_id: str = None
    name: str = None  # canonical user name
    secret: str = None
    groups: list[dict[str, str]] = field(default_factory=list)

    def has_access(self, group_id: ULID | str, access: Access = "r"):
        group_id = group_id if isinstance(group_id, str) else str(group_id)
        return any(g["id"] == group_id and access == g["access"] for g in self.groups)

    def set_access(self, group_id: ULID | str, access: Access):
        group_id = group_id if isinstance(group_id, str) else str(group_id)
        for g in self.groups:
            if g["id"] == group_id:
                g["access"] = access
                break
        else:
            self.groups.append({"id": group_id, "access": access})


@dataclass
class Group:
    _table: ClassVar[str] = "groups"

    id: ULID = field(default_factory=ULID)
    name: str = None
    users: list[dict[str, str]] = field(default_factory=list)