import logging
import os

logger = logging.getLogger(__name__)


def check_framework(framework="tf"):
    """
    Checks, whether the given framework is "valid", meaning, whether all
    necessary dependencies are installed. Errors otherwise.

    Args:
        framework (str): Once of "tf", "torch", or None.

    Returns:
        str: The input framework string.
    """
    if framework == "tf":
        try_import_tf(error=True)
    elif framework == "torch":
        try_import_torch(error=True)
    else:
        assert framework is None
    return framework


def try_import_tf(error=False):
    """
    Args:
        error (bool): Whether to raise an error if tf cannot be imported.

    Returns:
        The tf module (either from tf2.0.compat.v1 OR as tf1.x.
    """
    if "RLLIB_TEST_NO_TF_IMPORT" in os.environ:
        logger.warning("Not importing TensorFlow for test purposes")
        return None

    try:
        if "TF_CPP_MIN_LOG_LEVEL" not in os.environ:
            os.environ["TF_CPP_MIN_LOG_LEVEL"] = "3"
        import tensorflow.compat.v1 as tf
        tf.logging.set_verbosity(tf.logging.ERROR)
        tf.disable_v2_behavior()
        return tf
    except ImportError:
        try:
            import tensorflow as tf
            return tf
        except ImportError as e:
            if error:
                raise e
            return None


def try_import_tfp(error=False):
    """
    Args:
        error (bool): Whether to raise an error if tfp cannot be imported.

    Returns:
        The tfp module.
    """
    if "RLLIB_TEST_NO_TF_IMPORT" in os.environ:
        logger.warning("Not importing TensorFlow Probability for test "
                       "purposes.")
        return None

    try:
        import tensorflow_probability as tfp
        return tfp
    except ImportError as e:
        if error:
            raise e
        return None


def try_import_torch(error=False):
    """
    Args:
        error (bool): Whether to raise an error if torch cannot be imported.

    Returns:
        tuple: torch AND torch.nn modules.
    """
    if "RLLIB_TEST_NO_TORCH_IMPORT" in os.environ:
        logger.warning("Not importing Torch for test purposes.")
        return None, None

    try:
        import torch
        import torch.nn as nn
        return torch, nn
    except ImportError as e:
        if error:
            raise e
        return None, None