from typing import List

from ray.rllib.utils.annotations import PublicAPI
from ray.rllib.utils.typing import TensorType, TensorStructType


@PublicAPI
class RepeatedValues:
    """Represents a variable-length list of items from spaces.Repeated.

    RepeatedValues are created when you use spaces.Repeated, and are
    accessible as part of input_dict["obs"] in ModelV2 forward functions.

    Example:
        Suppose the gym space definition was:
            Repeated(Repeated(Box(K), N), M)

        Then in the model forward function, input_dict["obs"] is of type:
            RepeatedValues(RepeatedValues(<Tensor shape=(B, M, N, K)>))

        The tensor is accessible via:
            input_dict["obs"].values.values

        And the actual data lengths via:
            # outer repetition, shape [B], range [0, M]
            input_dict["obs"].lengths
                -and-
            # inner repetition, shape [B, M], range [0, N]
            input_dict["obs"].values.lengths

    Attributes:
        values (Tensor): The padded data tensor of shape [B, max_len, ..., sz],
            where B is the batch dimension, max_len is the max length of this
            list, followed by any number of sub list max lens, followed by the
            actual data size.
        lengths (List[int]): Tensor of shape [B, ...] that represents the
            number of valid items in each list. When the list is nested within
            other lists, there will be extra dimensions for the parent list
            max lens.
        max_len (int): The max number of items allowed in each list.

    TODO(ekl): support conversion to tf.RaggedTensor.
    """

    def __init__(self, values: TensorType, lengths: List[int], max_len: int):
        self.values = values
        self.lengths = lengths
        self.max_len = max_len
        self._unbatched_repr = None

    def unbatch_all(self) -> List[List[TensorType]]:
        """Unbatch both the repeat and batch dimensions into Python lists.

        This is only supported in PyTorch / TF eager mode.

        This lets you view the data unbatched in its original form, but is
        not efficient for processing.

        Examples:
            >>> batch = RepeatedValues(<Tensor shape=(B, N, K)>)
            >>> items = batch.unbatch_all()
            >>> print(len(items) == B)
            True
            >>> print(max(len(x) for x in items) <= N)
            True
            >>> print(items)
            ... [[<Tensor_1 shape=(K)>, ..., <Tensor_N, shape=(K)>],
            ...  ...
            ...  [<Tensor_1 shape=(K)>, <Tensor_2 shape=(K)>],
            ...  ...
            ...  [<Tensor_1 shape=(K)>],
            ...  ...
            ...  [<Tensor_1 shape=(K)>, ..., <Tensor_N shape=(K)>]]
        """

        if self._unbatched_repr is None:
            B = _get_batch_dim_helper(self.values)
            if B is None:
                raise ValueError(
                    "Cannot call unbatch_all() when batch_dim is unknown. "
                    "This is probably because you are using TF graph mode.")
            else:
                B = int(B)
            slices = self.unbatch_repeat_dim()
            result = []
            for i in range(B):
                if hasattr(self.lengths[i], "item"):
                    dynamic_len = int(self.lengths[i].item())
                else:
                    dynamic_len = int(self.lengths[i].numpy())
                dynamic_slice = []
                for j in range(dynamic_len):
                    dynamic_slice.append(_batch_index_helper(slices, i, j))
                result.append(dynamic_slice)
            self._unbatched_repr = result

        return self._unbatched_repr

    def unbatch_repeat_dim(self) -> List[TensorType]:
        """Unbatches the repeat dimension (the one `max_len` in size).

        This removes the repeat dimension. The result will be a Python list of
        with length `self.max_len`. Note that the data is still padded.

        Examples:
            >>> batch = RepeatedValues(<Tensor shape=(B, N, K)>)
            >>> items = batch.unbatch()
            >>> len(items) == batch.max_len
            True
            >>> print(items)
            ... [<Tensor_1 shape=(B, K)>, ..., <Tensor_N shape=(B, K)>]
        """
        return _unbatch_helper(self.values, self.max_len)

    def __repr__(self):
        return "RepeatedValues(value={}, lengths={}, max_len={})".format(
            repr(self.values), repr(self.lengths), self.max_len)

    def __str__(self):
        return repr(self)


def _get_batch_dim_helper(v: TensorStructType) -> int:
    """Tries to find the batch dimension size of v, or None."""
    if isinstance(v, dict):
        for u in v.values():
            return _get_batch_dim_helper(u)
    elif isinstance(v, tuple):
        return _get_batch_dim_helper(v[0])
    elif isinstance(v, RepeatedValues):
        return _get_batch_dim_helper(v.values)
    else:
        B = v.shape[0]
        if hasattr(B, "value"):
            B = B.value  # TensorFlow
        return B


def _unbatch_helper(v: TensorStructType, max_len: int) -> TensorStructType:
    """Recursively unpacks the repeat dimension (max_len)."""
    if isinstance(v, dict):
        return {k: _unbatch_helper(u, max_len) for (k, u) in v.items()}
    elif isinstance(v, tuple):
        return tuple(_unbatch_helper(u, max_len) for u in v)
    elif isinstance(v, RepeatedValues):
        unbatched = _unbatch_helper(v.values, max_len)
        return [
            RepeatedValues(u, v.lengths[:, i, ...], v.max_len)
            for i, u in enumerate(unbatched)
        ]
    else:
        return [v[:, i, ...] for i in range(max_len)]


def _batch_index_helper(v: TensorStructType, i: int,
                        j: int) -> TensorStructType:
    """Selects the item at the ith batch index and jth repetition."""
    if isinstance(v, dict):
        return {k: _batch_index_helper(u, i, j) for (k, u) in v.items()}
    elif isinstance(v, tuple):
        return tuple(_batch_index_helper(u, i, j) for u in v)
    elif isinstance(v, list):
        # This is the output of unbatch_repeat_dim(). Unfortunately we have to
        # process it here instead of in unbatch_all(), since it may be buried
        # under a dict / tuple.
        return _batch_index_helper(v[j], i, j)
    elif isinstance(v, RepeatedValues):
        unbatched = v.unbatch_all()
        # Don't need to select j here; that's already done in unbatch_all.
        return unbatched[i]
    else:
        return v[i, ...]