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from datetime import datetime
from typing import Any, Callable, Collection, Dict, Mapping, TypeVar

from airflow import settings
from airflow.utils.context import Context, lazy_mapping_from_context

R = TypeVar("R")

DEFAULT_FORMAT_PREFIX = 'airflow.ctx.'
ENV_VAR_FORMAT_PREFIX = 'AIRFLOW_CTX_'

AIRFLOW_VAR_NAME_FORMAT_MAPPING = {
    'AIRFLOW_CONTEXT_DAG_ID': {
        'default': f'{DEFAULT_FORMAT_PREFIX}dag_id',
        'env_var_format': f'{ENV_VAR_FORMAT_PREFIX}DAG_ID',
    },
    'AIRFLOW_CONTEXT_TASK_ID': {
        'default': f'{DEFAULT_FORMAT_PREFIX}task_id',
        'env_var_format': f'{ENV_VAR_FORMAT_PREFIX}TASK_ID',
    },
    'AIRFLOW_CONTEXT_EXECUTION_DATE': {
        'default': f'{DEFAULT_FORMAT_PREFIX}execution_date',
        'env_var_format': f'{ENV_VAR_FORMAT_PREFIX}EXECUTION_DATE',
    },
    'AIRFLOW_CONTEXT_TRY_NUMBER': {
        'default': f'{DEFAULT_FORMAT_PREFIX}try_number',
        'env_var_format': f'{ENV_VAR_FORMAT_PREFIX}TRY_NUMBER',
    },
    'AIRFLOW_CONTEXT_DAG_RUN_ID': {
        'default': f'{DEFAULT_FORMAT_PREFIX}dag_run_id',
        'env_var_format': f'{ENV_VAR_FORMAT_PREFIX}DAG_RUN_ID',
    },
    'AIRFLOW_CONTEXT_DAG_OWNER': {
        'default': f'{DEFAULT_FORMAT_PREFIX}dag_owner',
        'env_var_format': f'{ENV_VAR_FORMAT_PREFIX}DAG_OWNER',
    },
    'AIRFLOW_CONTEXT_DAG_EMAIL': {
        'default': f'{DEFAULT_FORMAT_PREFIX}dag_email',
        'env_var_format': f'{ENV_VAR_FORMAT_PREFIX}DAG_EMAIL',
    },
}


def context_to_airflow_vars(context: Mapping[str, Any], in_env_var_format: bool = False) -> Dict[str, str]:
    """
    Given a context, this function provides a dictionary of values that can be used to
    externally reconstruct relations between dags, dag_runs, tasks and task_instances.
    Default to abc.def.ghi format and can be made to ABC_DEF_GHI format if
    in_env_var_format is set to True.

    :param context: The context for the task_instance of interest.
    :param in_env_var_format: If returned vars should be in ABC_DEF_GHI format.
    :return: task_instance context as dict.
    """
    params = {}
    if in_env_var_format:
        name_format = 'env_var_format'
    else:
        name_format = 'default'

    task = context.get('task')
    task_instance = context.get('task_instance')
    dag_run = context.get('dag_run')

    ops = [
        (task, 'email', 'AIRFLOW_CONTEXT_DAG_EMAIL'),
        (task, 'owner', 'AIRFLOW_CONTEXT_DAG_OWNER'),
        (task_instance, 'dag_id', 'AIRFLOW_CONTEXT_DAG_ID'),
        (task_instance, 'task_id', 'AIRFLOW_CONTEXT_TASK_ID'),
        (task_instance, 'execution_date', 'AIRFLOW_CONTEXT_EXECUTION_DATE'),
        (task_instance, 'try_number', 'AIRFLOW_CONTEXT_TRY_NUMBER'),
        (dag_run, 'run_id', 'AIRFLOW_CONTEXT_DAG_RUN_ID'),
    ]

    context_params = settings.get_airflow_context_vars(context)
    for key, value in context_params.items():
        if not isinstance(key, str):
            raise TypeError(f"key <{key}> must be string")
        if not isinstance(value, str):
            raise TypeError(f"value of key <{key}> must be string, not {type(value)}")

        if in_env_var_format:
            if not key.startswith(ENV_VAR_FORMAT_PREFIX):
                key = ENV_VAR_FORMAT_PREFIX + key.upper()
        else:
            if not key.startswith(DEFAULT_FORMAT_PREFIX):
                key = DEFAULT_FORMAT_PREFIX + key
        params[key] = value

    for subject, attr, mapping_key in ops:
        _attr = getattr(subject, attr, None)
        if subject and _attr:
            mapping_value = AIRFLOW_VAR_NAME_FORMAT_MAPPING[mapping_key][name_format]
            if isinstance(_attr, str):
                params[mapping_value] = _attr
            elif isinstance(_attr, datetime):
                params[mapping_value] = _attr.isoformat()
            elif isinstance(_attr, list):
                # os env variable value needs to be string
                params[mapping_value] = ','.join(_attr)
            else:
                params[mapping_value] = str(_attr)

    return params


class KeywordParameters:
    """Wrapper representing ``**kwargs`` to a callable.

    The actual ``kwargs`` can be obtained by calling either ``unpacking()`` or
    ``serializing()``. They behave almost the same and are only different if
    the containing ``kwargs`` is an Airflow Context object, and the calling
    function uses ``**kwargs`` in the argument list.

    In this particular case, ``unpacking()`` uses ``lazy-object-proxy`` to
    prevent the Context from emitting deprecation warnings too eagerly when it's
    unpacked by ``**``. ``serializing()`` does not do this, and will allow the
    warnings to be emitted eagerly, which is useful when you want to dump the
    content and use it somewhere else without needing ``lazy-object-proxy``.
    """

    def __init__(self, kwargs: Mapping[str, Any], *, wildcard: bool) -> None:
        self._kwargs = kwargs
        self._wildcard = wildcard

    @classmethod
    def determine(
        cls,
        func: Callable[..., Any],
        args: Collection[Any],
        kwargs: Mapping[str, Any],
    ) -> "KeywordParameters":
        import inspect
        import itertools

        signature = inspect.signature(func)
        has_wildcard_kwargs = any(p.kind == p.VAR_KEYWORD for p in signature.parameters.values())

        for name in itertools.islice(signature.parameters.keys(), len(args)):
            # Check if args conflict with names in kwargs.
            if name in kwargs:
                raise ValueError(f"The key {name!r} in args is a part of kwargs and therefore reserved.")

        if has_wildcard_kwargs:
            # If the callable has a **kwargs argument, it's ready to accept all the kwargs.
            return cls(kwargs, wildcard=True)

        # If the callable has no **kwargs argument, it only wants the arguments it requested.
        kwargs = {key: kwargs[key] for key in signature.parameters if key in kwargs}
        return cls(kwargs, wildcard=False)

    def unpacking(self) -> Mapping[str, Any]:
        """Dump the kwargs mapping to unpack with ``**`` in a function call."""
        if self._wildcard and isinstance(self._kwargs, Context):
            return lazy_mapping_from_context(self._kwargs)
        return self._kwargs

    def serializing(self) -> Mapping[str, Any]:
        """Dump the kwargs mapping for serialization purposes."""
        return self._kwargs


def determine_kwargs(
    func: Callable[..., Any],
    args: Collection[Any],
    kwargs: Mapping[str, Any],
) -> Mapping[str, Any]:
    """
    Inspect the signature of a given callable to determine which arguments in kwargs need
    to be passed to the callable.

    :param func: The callable that you want to invoke
    :param args: The positional arguments that needs to be passed to the callable, so we
        know how many to skip.
    :param kwargs: The keyword arguments that need to be filtered before passing to the callable.
    :return: A dictionary which contains the keyword arguments that are compatible with the callable.
    """
    return KeywordParameters.determine(func, args, kwargs).unpacking()


def make_kwargs_callable(func: Callable[..., R]) -> Callable[..., R]:
    """
    Make a new callable that can accept any number of positional or keyword arguments
    but only forwards those required by the given callable func.
    """
    import functools

    @functools.wraps(func)
    def kwargs_func(*args, **kwargs):
        kwargs = determine_kwargs(func, args, kwargs)
        return func(*args, **kwargs)

    return kwargs_func
