"""
This is the configuration tooling for scikit-build-core. This is build around
the :class:`Source` Protocol. Sources are created with some input (like a toml
file for the :class:`TOMLSource`). Sources also usually have some prefix (like
``tool.scikit-build``) as well. The :class:`SourceChain` holds a collection of
Sources, and is the primary way to use them.

An end user interacts with :class:`SourceChain` via ``.convert_target``, which
takes a Dataclass class and returns an instance with fields populated.

Example of usage::

    sources = SourceChain(TOMLSource("tool", "mypackage", settings=pyproject_dict), ...)
    settings = sources.convert_target(SomeSettingsModel)

    unrecognized_options = list(source.unrecognized_options(SomeSettingsModel)


Naming conventions:

- ``model`` is the complete Dataclass.
- ``target`` is the type to convert a single item to.
- ``settings`` is the input data source (unless it already has a name, like
  ``env``).
- ``options`` are the names of the items in the ``model``, formatted in the
  style of the current Source.
- ``fields`` are the tuple of strings describing a nested field in the
  ``model``.

When setting up your dataclasses, these types are handled:

- ``str``: A string type, nothing special.
- ``bool``: Supports bool in TOML, not handled in envvar/config (so only useful in a Union)
- Any callable (`Path`, `Version`): Passed the string input.
- ``Optional[T]``: Treated like T. Default should be None, since no input format supports None's.
- ``Union[str, ...]``: Supports other input types in TOML form (bool currently). Otherwise a string.
- ``List[T]``: A list of items. `;` separated supported in EnvVar/config forms. T can be a dataclass (TOML only).
- ``Dict[str, T]``: A table of items. TOML supports a layer of nesting. Any is supported as an item type.
- ``Union[list[T], Dict[str, T]]`` (TOML only): A list or dict of items.
- ``Literal[...]``: A list of strings, the result must be in the list.
- ``Annotated[Dict[...], "EnvVar"]``: A dict of items, where each item can be a string or a dict with "env" and "default" keys.

These are supported for JSON schema generation for the TOML, as well.

Integers/floats would be easy to add, but haven't been needed yet.
"""

from __future__ import annotations

import dataclasses
import os
import sys
import typing
from typing import Any, Literal, Protocol, TypeVar, Union

from .._compat.builtins import ExceptionGroup
from .._compat.typing import Annotated, get_args, get_origin

if typing.TYPE_CHECKING:
    from collections.abc import Generator, Iterator, Mapping, Sequence

# Runtime check for PEP 604 union syntax (A | B) support
# types.UnionType only exists in Python 3.10+
if sys.version_info >= (3, 10):
    from types import NoneType
    from types import UnionType as _UnionType
else:
    NoneType = type(None)

    class _UnionType:
        pass


T = TypeVar("T")

__all__ = ["ConfSource", "EnvSource", "Source", "SourceChain", "TOMLSource"]


def __dir__() -> list[str]:
    return __all__


def _dig_strict(_dict: Mapping[str, Any], /, *names: str) -> Any:
    for name in names:
        _dict = _dict[name]
    return _dict


def _process_bool(value: str) -> bool:
    return value.strip().lower() not in {"0", "false", "off", "no", ""}


def _dig_not_strict(_dict: Mapping[str, Any], /, *names: str) -> Any:
    for name in names:
        _dict = _dict.get(name, {})
    return _dict


def _dig_fields(opt: Any, /, *names: str) -> Any:
    for name in names:
        fields = dataclasses.fields(opt)
        types = [x.type for x in fields if x.name == name]
        if len(types) != 1:
            msg = f"Could not access {'.'.join(names)}"
            raise KeyError(msg)
        (opt,) = types
    return opt


def _process_union(target: Any, /) -> Any:
    """
    Filters None out of Unions. If a Union only has one item, return that item.
    """

    origin = get_origin(target)

    if _is_union_type(origin):
        non_none_args = [a for a in get_args(target) if a is not NoneType]
        if len(non_none_args) == 1:
            return non_none_args[0]
        return Union[tuple(non_none_args)]

    return target


def _process_annotated(target: type[Any], /) -> tuple[Any, tuple[Any, ...]]:
    """
    Splits annotated into raw type and annotations. If not annotated, the annotations will be empty.
    """

    origin = get_origin(target)
    if origin is Annotated:
        return get_args(target)[0], get_args(target)[1:]

    return target, ()


def _get_target_raw_type(target: type[Any] | Any, /) -> Any:
    """
    Takes a type like ``Optional[str]`` and returns str, or ``Optional[Dict[str,
    int]]`` and returns dict. Returns Union for a Union with more than one
    non-none type. Literal is also a valid return. Works through Annotated.
    """

    target, _ = _process_annotated(target)
    target = _process_union(target)
    origin = get_origin(target)
    return origin or target


def _is_union_type(raw_target: Any) -> bool:
    """
    Check if raw_target is a Union type (either ``typing.Union`` or ``types.UnionType``).
    Handles both ``typing.Union[A, B]`` and PEP 604 syntax (``A | B``).
    """
    return raw_target is Union or raw_target is _UnionType


def _get_inner_type(_target: type[Any], /) -> type[Any]:
    """
    Takes a types like ``List[str]`` and returns str,
    or ``Dict[str, int]`` and returns int.
    """

    raw_target = _get_target_raw_type(_target)
    target = _process_union(_target)
    if raw_target is list:
        return get_args(target)[0]  # type: ignore[no-any-return]
    if raw_target is dict:
        return get_args(target)[1]  # type: ignore[no-any-return]
    msg = f"Expected a list or dict, got {target!r}"
    raise AssertionError(msg)


def _nested_dataclass_to_names(
    target: type[Any] | Any, /, *inner: str
) -> Iterator[list[str]]:
    """
    Yields each entry, like ``("a", "b", "c")`` for ``a.b.c``.
    """

    if dataclasses.is_dataclass(target) and isinstance(target, type):
        for field in dataclasses.fields(target):
            yield from _nested_dataclass_to_names(field.type, *inner, field.name)
    else:
        yield list(inner)


def _dict_with_envvar(target: Any, /) -> Any:
    """
    This produces values. Supports "env" and "default" keys.
    """
    if not isinstance(target, dict):
        return target
    env = target["env"]
    default = target.get("default", None)
    value = os.environ.get(env, default)
    if isinstance(default, bool) and isinstance(value, str):
        return _process_bool(value)
    return value


class Source(Protocol):
    def has_item(self, *fields: str, is_dict: bool) -> bool:
        """
        Check if the source contains a chain of fields. For example, ``fields =
        [Field(name="a"), Field(name="b")]`` will check if the source contains the
        key "a.b". ``is_dict`` should be set if it can be nested.
        """
        ...

    def get_item(self, *fields: str, is_dict: bool) -> Any:
        """
        Select an item from a chain of fields. Raises KeyError if
        the there is no item. ``is_dict`` should be set if it can be nested.
        """
        ...

    @classmethod
    def convert(cls, item: Any, target: type[Any] | Any) -> object:
        """
        Convert an ``item`` from the base representation of the source's source
        into a ``target`` type. Raises TypeError if the conversion fails.
        """
        ...

    def unrecognized_options(self, options: object) -> Generator[str, None, None]:
        """
        Given a model, produce an iterator of all unrecognized option names.
        Empty iterator if this can't be computed for the source (like for
        environment variables).
        """
        ...

    def all_option_names(self, target: type[Any]) -> Iterator[str]:
        """
        Given a model, produce a list of all possible names (used for producing
        suggestions).
        """
        ...


class EnvSource:
    """
    This is a source using environment variables.
    """

    def __init__(self, prefix: str, *, env: Mapping[str, str] | None = None) -> None:
        self.env = env or os.environ
        self.prefix = prefix

    def _get_name(self, *fields: str) -> str:
        names = [field.upper() for field in fields]
        return "_".join([self.prefix, *names] if self.prefix else names)

    def has_item(self, *fields: str, is_dict: bool) -> bool:  # noqa: ARG002
        name = self._get_name(*fields)
        return bool(self.env.get(name, ""))

    def get_item(
        self,
        *fields: str,
        is_dict: bool,  # noqa: ARG002
    ) -> str | dict[str, str]:
        name = self._get_name(*fields)
        if name in self.env:
            return self.env[name]
        msg = f"{name!r} not found in environment"
        raise KeyError(msg)

    @classmethod
    def convert(cls, item: str, target: type[Any] | Any) -> object:
        """
        Convert an item from the environment (always a string) into a target type.
        """
        target, _ = _process_annotated(target)
        raw_target = _get_target_raw_type(target)
        if dataclasses.is_dataclass(raw_target):
            msg = f"Array of dataclasses are not supported in configuration settings ({raw_target})"
            raise TypeError(msg)
        if raw_target is list:
            return [
                cls.convert(i.strip(), _get_inner_type(target)) for i in item.split(";")
            ]
        if raw_target is dict:
            items = (i.strip().split("=") for i in item.split(";"))
            return {k: cls.convert(v, _get_inner_type(target)) for k, v in items}

        if raw_target is bool:
            return _process_bool(item)

        if _is_union_type(raw_target) and str in get_args(target):
            return item

        if _is_union_type(raw_target):
            args = {_get_target_raw_type(t): t for t in get_args(target)}
            if str in args:
                return item
            if dict in args and "=" in item:
                items = (i.strip().split("=") for i in item.split(";"))
                return {
                    k: cls.convert(v, _get_inner_type(args[dict])) for k, v in items
                }
            if list in args:
                return [
                    cls.convert(i.strip(), _get_inner_type(args[list]))
                    for i in item.split(";")
                ]
            msg = f"Can't convert into {target}"
            raise TypeError(msg)

        if raw_target is Literal:
            if item not in get_args(_process_union(target)):
                msg = f"{item!r} not in {get_args(_process_union(target))!r}"
                raise TypeError(msg)
            return item

        if callable(raw_target):
            return raw_target(item)
        msg = f"Can't convert target {target}"
        raise TypeError(msg)

    @staticmethod
    def unrecognized_options(
        options: object,  # noqa: ARG004
    ) -> Generator[str, None, None]:
        yield from ()

    def all_option_names(self, target: type[Any]) -> Iterator[str]:
        prefix = [self.prefix] if self.prefix else []
        for names in _nested_dataclass_to_names(target):
            yield "_".join(prefix + names).upper()


def _unrecognized_dict(
    settings: Mapping[str, Any], options: Any, above: Sequence[str]
) -> Generator[str, None, None]:
    for keystr in settings:
        # We don't have DataclassInstance exposed in typing yet
        matches = [
            x for x in dataclasses.fields(options) if x.name.replace("_", "-") == keystr
        ]
        if not matches:
            yield ".".join((*above, keystr))
            continue
        (inner_option_field,) = matches
        inner_option = inner_option_field.type
        if dataclasses.is_dataclass(inner_option) and isinstance(inner_option, type):
            yield from _unrecognized_dict(
                settings[keystr], inner_option, (*above, keystr)
            )


class ConfSource:
    """
    This is a source for the PEP 517 configuration settings.
    You should initialize it with a dict from PEP 517. a.b will be treated as
    nested dicts. "verify" is a boolean that determines whether unrecognized
    options should be checked for. Only set this to false if this might be sharing
    config options at the same level.

    While most mechanisms (pip, uv, build) only support text, gpep517 allows an
    arbitrary json input, so this currently also handles bools.
    """

    def __init__(
        self,
        *prefixes: str,
        settings: Mapping[str, str | list[str] | bool],
        verify: bool = True,
    ) -> None:
        self.prefixes = prefixes
        self.settings = settings
        self.verify = verify

    def _get_name(self, *fields: str) -> list[str]:
        names = [field.replace("_", "-") for field in fields]
        return [*self.prefixes, *names]

    def has_item(self, *fields: str, is_dict: bool) -> bool:
        names = self._get_name(*fields)
        name = ".".join(names)

        if is_dict:
            return any(k.startswith(f"{name}.") for k in self.settings)

        return name in self.settings

    def get_item(
        self, *fields: str, is_dict: bool
    ) -> str | list[str] | dict[str, str] | bool:
        names = self._get_name(*fields)
        name = ".".join(names)
        if is_dict:
            d = {
                k[len(name) + 1 :]: str(v)
                for k, v in self.settings.items()
                if k.startswith(f"{name}.")
            }
            if d:
                return d
            msg = f"Dict items {name}.* not found in settings"
            raise KeyError(msg)
        if name in self.settings:
            return self.settings[name]

        msg = f"{name!r} not found in configuration settings"
        raise KeyError(msg)

    @classmethod
    def convert(
        cls, item: str | list[str] | dict[str, str] | bool, target: type[Any] | Any
    ) -> object:
        target, _ = _process_annotated(target)
        raw_target = _get_target_raw_type(target)
        if dataclasses.is_dataclass(raw_target):
            msg = f"Array of dataclasses are not supported in configuration settings ({raw_target})"
            raise TypeError(msg)
        if raw_target is list:
            if isinstance(item, list):
                return [cls.convert(i, _get_inner_type(target)) for i in item]
            if isinstance(item, (dict, bool)):
                msg = f"Expected {target}, got {type(item)}"
                raise TypeError(msg)
            return [
                cls.convert(i.strip(), _get_inner_type(target)) for i in item.split(";")
            ]
        if raw_target is dict:
            assert not isinstance(item, (str, list, bool))
            return {k: cls.convert(v, _get_inner_type(target)) for k, v in item.items()}
        if _is_union_type(raw_target):
            args = {_get_target_raw_type(t): t for t in get_args(target)}
            if str in args:
                return item
            if dict in args and isinstance(item, dict):
                return {
                    k: cls.convert(v, _get_inner_type(args[dict]))
                    for k, v in item.items()
                }
            if list in args and isinstance(item, list):
                return [cls.convert(i, _get_inner_type(args[list])) for i in item]
            msg = f"Can't convert into {target}"
            raise TypeError(msg)
        if isinstance(item, (list, dict)):
            msg = f"Expected {target}, got {type(item).__name__}"
            raise TypeError(msg)
        if raw_target is bool:
            return item if isinstance(item, bool) else _process_bool(item)
        if raw_target is Literal:
            if item not in get_args(_process_union(target)):
                msg = f"{item!r} not in {get_args(_process_union(target))!r}"
                raise TypeError(msg)
            return item
        if callable(raw_target):
            return raw_target(item)
        msg = f"Can't convert target {target}"
        raise TypeError(msg)

    def unrecognized_options(self, options: object) -> Generator[str, None, None]:
        if not self.verify:
            return
        for keystr in self.settings:
            keys = keystr.replace("-", "_").split(".")[len(self.prefixes) :]
            try:
                outer_option = _dig_fields(options, *keys[:-1])
            except KeyError:
                yield ".".join(keystr.split(".")[:-1])
                continue
            if dataclasses.is_dataclass(outer_option):
                try:
                    _dig_fields(outer_option, keys[-1])
                except KeyError:
                    yield keystr
                    continue
            if _get_target_raw_type(outer_option) is dict:
                continue

    def all_option_names(self, target: type[Any]) -> Iterator[str]:
        for names in _nested_dataclass_to_names(target):
            dash_names = [name.replace("_", "-") for name in names]
            yield ".".join((*self.prefixes, *dash_names))


class TOMLSource:
    def __init__(self, *prefixes: str, settings: Mapping[str, Any]) -> None:
        self.prefixes = prefixes
        self.settings = _dig_not_strict(settings, *prefixes)

    @staticmethod
    def _get_name(*fields: str) -> list[str]:
        return [field.replace("_", "-") for field in fields]

    def has_item(self, *fields: str, is_dict: bool) -> bool:  # noqa: ARG002
        names = self._get_name(*fields)
        try:
            _dig_strict(self.settings, *names)
        except KeyError:
            return False
        return True

    def get_item(self, *fields: str, is_dict: bool) -> Any:  # noqa: ARG002
        names = self._get_name(*fields)
        try:
            return _dig_strict(self.settings, *names)
        except KeyError:
            msg = f"{names!r} not found in configuration settings"
            raise KeyError(msg) from None

    @classmethod
    def convert(cls, item: Any, target: type[Any] | Any) -> object:
        """
        Convert an ``item`` from TOML into a ``target`` type.
        """
        target, annotations = _process_annotated(target)
        raw_target = _get_target_raw_type(target)
        if dataclasses.is_dataclass(raw_target) and isinstance(raw_target, type):
            fields = dataclasses.fields(raw_target)
            values = ((k.replace("-", "_"), v) for k, v in item.items())
            return raw_target(
                **{
                    k: cls.convert(v, *[f.type for f in fields if f.name == k])
                    for k, v in values
                }
            )
        if raw_target is list:
            if not isinstance(item, list):
                msg = f"Expected {target}, got {type(item).__name__}"
                raise TypeError(msg)
            return [cls.convert(it, _get_inner_type(target)) for it in item]
        if raw_target is dict:
            if not isinstance(item, dict):
                msg = f"Expected {target}, got {type(item).__name__}"
                raise TypeError(msg)
            if annotations == ("EnvVar",):
                return {
                    k: cls.convert(_dict_with_envvar(v), _get_inner_type(target))
                    for k, v in item.items()
                    if _dict_with_envvar(v) is not None
                }
            return {k: cls.convert(v, _get_inner_type(target)) for k, v in item.items()}
        if raw_target is Any:
            return item
        if _is_union_type(raw_target):
            args = {_get_target_raw_type(t): t for t in get_args(target)}
            if type(item) in args:
                if isinstance(item, dict):
                    return {
                        k: cls.convert(v, _get_inner_type(args[dict]))
                        for k, v in item.items()
                    }
                if isinstance(item, list):
                    return [cls.convert(i, _get_inner_type(args[list])) for i in item]
                return item
        if raw_target is Literal:
            if item not in get_args(_process_union(target)):
                msg = f"{item!r} not in {get_args(_process_union(target))!r}"
                raise TypeError(msg)
            return item
        if callable(raw_target):
            return raw_target(item)
        msg = f"Can't convert target {target}"
        raise TypeError(msg)

    def unrecognized_options(self, options: object) -> Generator[str, None, None]:
        yield from _unrecognized_dict(self.settings, options, self.prefixes)

    def all_option_names(self, target: type[Any]) -> Iterator[str]:
        for names in _nested_dataclass_to_names(target):
            dash_names = [name.replace("_", "-") for name in names]
            yield ".".join((*self.prefixes, *dash_names))


class SourceChain:
    def __init__(self, *sources: Source, prefixes: Sequence[str] = ()) -> None:
        """
        Combine a collection of sources into a single object that can run
        ``convert_target(dataclass)``.  An optional list of prefixes can be
        given that will be prepended (dot separated) to error messages.
        """
        self.sources = sources
        self.prefixes = prefixes

    def __getitem__(self, index: int) -> Source:
        return self.sources[index]

    def has_item(self, *fields: str, is_dict: bool) -> bool:
        return any(source.has_item(*fields, is_dict=is_dict) for source in self.sources)

    def get_item(self, *fields: str, is_dict: bool) -> Any:
        for source in self.sources:
            if source.has_item(*fields, is_dict=is_dict):
                return source.get_item(*fields, is_dict=is_dict)
        msg = f"{fields!r} not found in any source"
        raise KeyError(msg)

    def convert_target(self, target: type[T], *prefixes: str) -> T:
        """
        Given a dataclass type, create an object of that dataclass filled
        with the values in the sources.
        """

        errors = []
        prep: dict[str, Any] = {}
        for field in dataclasses.fields(target):  # type: ignore[arg-type]
            if dataclasses.is_dataclass(field.type) and isinstance(field.type, type):
                try:
                    prep[field.name] = self.convert_target(
                        field.type, *prefixes, field.name
                    )
                except Exception as e:  # noqa: BLE001
                    name = ".".join([*self.prefixes, *prefixes, field.name])
                    e.__notes__ = [*getattr(e, "__notes__", []), f"Field: {name}"]  # type: ignore[attr-defined]
                    errors.append(e)
                continue

            is_dict = _get_target_raw_type(field.type) is dict

            for source in self.sources:
                if source.has_item(*prefixes, field.name, is_dict=is_dict):
                    simple = source.get_item(*prefixes, field.name, is_dict=is_dict)
                    try:
                        tmp = source.convert(simple, field.type)
                    except Exception as e:  # noqa: BLE001
                        name = ".".join([*self.prefixes, *prefixes, field.name])
                        e.__notes__ = [*getattr(e, "__notes__", []), f"Field {name}"]  # type: ignore[attr-defined]
                        errors.append(e)
                        prep[field.name] = None
                        break

                    if is_dict:
                        assert isinstance(tmp, dict), f"{field.name} must be a dict"
                        prep[field.name] = {**tmp, **prep.get(field.name, {})}
                        continue

                    prep[field.name] = tmp
                    break

            if field.name in prep:
                continue

            if field.default is not dataclasses.MISSING:
                prep[field.name] = field.default
                continue
            if field.default_factory is not dataclasses.MISSING:
                prep[field.name] = field.default_factory()
                continue

            errors.append(ValueError(f"Missing value for {field.name!r}"))

        if errors:
            prefix_str = ".".join([*self.prefixes, *prefixes])
            msg = f"Failed converting {prefix_str}"
            raise ExceptionGroup(msg, errors)

        return target(**prep)

    def unrecognized_options(self, options: object) -> Generator[str, None, None]:
        for source in self.sources:
            yield from source.unrecognized_options(options)


if typing.TYPE_CHECKING:
    _: Source = typing.cast("EnvSource", None)
    _ = typing.cast("ConfSource", None)
    _ = typing.cast("TOMLSource", None)