# Copyright (c) 2022-2024, The ORBIT Project Developers.
# All rights reserved.
#
# SPDX-License-Identifier: BSD-3-Clause

"""Sub-module that provides a wrapper around the Python 3.7 onwards ``dataclasses`` module."""

import inspect
from collections.abc import Callable
from copy import deepcopy
from dataclasses import MISSING, Field, dataclass, field, replace
from typing import Any, ClassVar

from .dict import class_to_dict, update_class_from_dict

_CONFIGCLASS_METHODS = ["to_dict", "from_dict", "replace", "copy"]
"""List of class methods added at runtime to dataclass."""

"""
Wrapper around dataclass.
"""


def __dataclass_transform__():
    """Add annotations decorator for PyLance."""
    return lambda a: a


@__dataclass_transform__()
def configclass(cls, **kwargs):
    """Wrapper around `dataclass` functionality to add extra checks and utilities.

    As of Python 3.7, the standard dataclasses have two main issues which makes them non-generic for
    configuration use-cases. These include:

    1. Requiring a type annotation for all its members.
    2. Requiring explicit usage of :meth:`field(default_factory=...)` to reinitialize mutable variables.

    This function provides a decorator that wraps around Python's `dataclass`_ utility to deal with
    the above two issues. It also provides additional helper functions for dictionary <-> class
    conversion and easily copying class instances.

    Usage:

    .. code-block:: python

        from dataclasses import MISSING

        from omni.isaac.orbit.utils.configclass import configclass


        @configclass
        class ViewerCfg:
            eye: list = [7.5, 7.5, 7.5]  # field missing on purpose
            lookat: list = field(default_factory=[0.0, 0.0, 0.0])


        @configclass
        class EnvCfg:
            num_envs: int = MISSING
            episode_length: int = 2000
            viewer: ViewerCfg = ViewerCfg()

        # create configuration instance
        env_cfg = EnvCfg(num_envs=24)

        # print information as a dictionary
        print(env_cfg.to_dict())

        # create a copy of the configuration
        env_cfg_copy = env_cfg.copy()

        # replace arbitrary fields using keyword arguments
        env_cfg_copy = env_cfg_copy.replace(num_envs=32)

    Args:
        cls: The class to wrap around.
        **kwargs: Additional arguments to pass to :func:`dataclass`.

    Returns:
        The wrapped class.

    .. _dataclass: https://docs.python.org/3/library/dataclasses.html
    """
    # add type annotations
    _add_annotation_types(cls)
    # add field factory
    _process_mutable_types(cls)
    # copy mutable members
    # note: we check if user defined __post_init__ function exists and augment it with our own
    if hasattr(cls, "__post_init__"):
        setattr(cls, "__post_init__", _combined_function(cls.__post_init__, _custom_post_init))
    else:
        setattr(cls, "__post_init__", _custom_post_init)
    # add helper functions for dictionary conversion
    setattr(cls, "to_dict", _class_to_dict)
    setattr(cls, "from_dict", _update_class_from_dict)
    setattr(cls, "replace", _replace_class_with_kwargs)
    setattr(cls, "copy", _copy_class)
    # wrap around dataclass
    cls = dataclass(cls, **kwargs)
    # return wrapped class
    return cls


"""
Dictionary <-> Class operations.

These are redefined here to add new docstrings.
"""


def _class_to_dict(obj: object) -> dict[str, Any]:
    """Convert an object into dictionary recursively.

    Returns:
        Converted dictionary mapping.
    """
    return class_to_dict(obj)


def _update_class_from_dict(obj, data: dict[str, Any]) -> None:
    """Reads a dictionary and sets object variables recursively.

    This function performs in-place update of the class member attributes.

    Args:
        data: Input (nested) dictionary to update from.

    Raises:
        TypeError: When input is not a dictionary.
        ValueError: When dictionary has a value that does not match default config type.
        KeyError: When dictionary has a key that does not exist in the default config type.
    """
    return update_class_from_dict(obj, data, _ns="")


def _replace_class_with_kwargs(obj: object, **kwargs) -> object:
    """Return a new object replacing specified fields with new values.

    This is especially useful for frozen classes.  Example usage:

    .. code-block:: python

        @configclass(frozen=True)
        class C:
            x: int
            y: int

        c = C(1, 2)
        c1 = c.replace(x=3)
        assert c1.x == 3 and c1.y == 2

    Args:
        obj: The object to replace.
        **kwargs: The fields to replace and their new values.

    Returns:
        The new object.
    """
    return replace(obj, **kwargs)


def _copy_class(obj: object) -> object:
    """Return a new object with the same fields as the original."""
    return replace(obj)


"""
Private helper functions.
"""


def _add_annotation_types(cls):
    """Add annotations to all elements in the dataclass.

    By definition in Python, a field is defined as a class variable that has a type annotation.

    In case type annotations are not provided, dataclass ignores those members when :func:`__dict__()` is called.
    This function adds these annotations to the class variable to prevent any issues in case the user forgets to
    specify the type annotation.

    This makes the following a feasible operation:

    @dataclass
    class State:
        pos = (0.0, 0.0, 0.0)
           ^^
           If the function is NOT used, the following type-error is returned:
           TypeError: 'pos' is a field but has no type annotation
    """
    # get type hints
    hints = {}
    # iterate over class inheritance
    # we add annotations from base classes first
    for base in reversed(cls.__mro__):
        # check if base is object
        if base is object:
            continue
        # get base class annotations
        ann = base.__dict__.get("__annotations__", {})
        # directly add all annotations from base class
        hints.update(ann)
        # iterate over base class members
        # Note: Do not change this to dir(base) since it orders the members alphabetically.
        #   This is not desirable since the order of the members is important in some cases.
        for key in base.__dict__:
            # get class member
            value = getattr(base, key)
            # skip members
            if _skippable_class_member(key, value, hints):
                continue
            # add type annotations for members that don't have explicit type annotations
            # for these, we deduce the type from the default value
            if not isinstance(value, type):
                if key not in hints:
                    # check if var type is not MISSING
                    # we cannot deduce type from MISSING!
                    if value is MISSING:
                        raise TypeError(
                            f"Missing type annotation for '{key}' in class '{cls.__name__}'."
                            " Please add a type annotation or set a default value."
                        )
                    # add type annotation
                    hints[key] = type(value)
            elif key != value.__name__:
                # note: we don't want to add type annotations for nested configclass. Thus, we check if
                #   the name of the type matches the name of the variable.
                # since Python 3.10, type hints are stored as strings
                hints[key] = f"type[{value.__name__}]"

    # Note: Do not change this line. `cls.__dict__.get("__annotations__", {})` is different from
    #   `cls.__annotations__` because of inheritance.
    cls.__annotations__ = cls.__dict__.get("__annotations__", {})
    cls.__annotations__ = hints


def _process_mutable_types(cls):
    """Initialize all mutable elements through :obj:`dataclasses.Field` to avoid unnecessary complaints.

    By default, dataclass requires usage of :obj:`field(default_factory=...)` to reinitialize mutable objects every time a new
    class instance is created. If a member has a mutable type and it is created without specifying the `field(default_factory=...)`,
    then Python throws an error requiring the usage of `default_factory`.

    Additionally, Python only explicitly checks for field specification when the type is a list, set or dict. This misses the
    use-case where the type is class itself. Thus, the code silently carries a bug with it which can lead to undesirable effects.

    This function deals with this issue

    This makes the following a feasible operation:

    @dataclass
    class State:
        pos: list = [0.0, 0.0, 0.0]
           ^^
           If the function is NOT used, the following value-error is returned:
           ValueError: mutable default <class 'list'> for field pos is not allowed: use default_factory
    """
    # note: Need to set this up in the same order as annotations. Otherwise, it
    #   complains about missing positional arguments.
    ann = cls.__dict__.get("__annotations__", {})

    # iterate over all class members and store them in a dictionary
    class_members = {}
    for base in reversed(cls.__mro__):
        # check if base is object
        if base is object:
            continue
        # iterate over base class members
        for key in base.__dict__:
            # get class member
            f = getattr(base, key)
            # skip members
            if _skippable_class_member(key, f):
                continue
            # store class member if it is not a type or if it is already present in annotations
            if not isinstance(f, type) or key in ann:
                class_members[key] = f
        # iterate over base class data fields
        # in previous call, things that became a dataclass field were removed from class members
        # so we need to add them back here as a dataclass field directly
        for key, f in base.__dict__.get("__dataclass_fields__", {}).items():
            # store class member
            if not isinstance(f, type):
                class_members[key] = f

    # check that all annotations are present in class members
    # note: mainly for debugging purposes
    if len(class_members) != len(ann):
        raise ValueError(
            f"In class '{cls.__name__}', number of annotations ({len(ann)}) does not match number of class members"
            f" ({len(class_members)}). Please check that all class members have type annotations and/or a default"
            " value. If you don't want to specify a default value, please use the literal `dataclasses.MISSING`."
        )
    # iterate over annotations and add field factory for mutable types
    for key in ann:
        # find matching field in class
        value = class_members.get(key, MISSING)
        # check if key belongs to ClassVar
        # in that case, we cannot use default_factory!
        origin = getattr(ann[key], "__origin__", None)
        if origin is ClassVar:
            continue
        # check if f is MISSING
        # note: commented out for now since it causes issue with inheritance
        #   of dataclasses when parent have some positional and some keyword arguments.
        # Ref: https://stackoverflow.com/questions/51575931/class-inheritance-in-python-3-7-dataclasses
        # TODO: check if this is fixed in Python 3.10
        # if f is MISSING:
        #     continue
        if isinstance(value, Field):
            setattr(cls, key, value)
        elif not isinstance(value, type):
            # create field factory for mutable types
            value = field(default_factory=_return_f(value))
            setattr(cls, key, value)


def _custom_post_init(obj):
    """Deepcopy all elements to avoid shared memory issues for mutable objects in dataclasses initialization.

    This function is called explicitly instead of as a part of :func:`_process_mutable_types()` to prevent mapping
    proxy type i.e. a read only proxy for mapping objects. The error is thrown when using hierarchical data-classes
    for configuration.
    """
    for key in dir(obj):
        # skip dunder members
        if key.startswith("__"):
            continue
        # get data member
        value = getattr(obj, key)
        # duplicate data members
        if not callable(value):
            setattr(obj, key, deepcopy(value))


def _combined_function(f1: Callable, f2: Callable) -> Callable:
    """Combine two functions into one.

    Args:
        f1: The first function.
        f2: The second function.

    Returns:
        The combined function.
    """

    def _combined(*args, **kwargs):
        # call both functions
        f1(*args, **kwargs)
        f2(*args, **kwargs)

    return _combined


"""
Helper functions
"""


def _skippable_class_member(key: str, value: Any, hints: dict | None = None) -> bool:
    """Check if the class member should be skipped in configclass processing.

    The following members are skipped:

    * Dunder members: ``__name__``, ``__module__``, ``__qualname__``, ``__annotations__``, ``__dict__``.
    * Manually-added special class functions: From :obj:`_CONFIGCLASS_METHODS`.
    * Members that are already present in the type annotations.
    * Functions bounded to class object or class.

    Args:
        key: The class member name.
        value: The class member value.
        hints: The type hints for the class. Defaults to None, in which case, the
            members existence in type hints are not checked.

    Returns:
        True if the class member should be skipped, False otherwise.
    """
    # skip dunder members
    if key.startswith("__"):
        return True
    # skip manually-added special class functions
    if key in _CONFIGCLASS_METHODS:
        return True
    # check if key is already present
    if hints is not None and key in hints:
        return True
    # skip functions bounded to class
    if callable(value):
        signature = inspect.signature(value)
        if "self" in signature.parameters or "cls" in signature.parameters:
            return True
    # Otherwise, don't skip
    return False


def _return_f(f: Any) -> Callable[[], Any]:
    """Returns default factory function for creating mutable/immutable variables.

    This function should be used to create default factory functions for variables.

    Example:

        .. code-block:: python

            value = field(default_factory=_return_f(value))
            setattr(cls, key, value)
    """

    def _wrap():
        if isinstance(f, Field):
            if f.default_factory is MISSING:
                return deepcopy(f.default)
            else:
                return f.default_factory
        else:
            return f

    return _wrap
