# coding: utf-8
# pylint: disable=invalid-name, protected-access, too-many-locals, too-many-arguments
"""Symbolic Executor component of MXNet."""
from __future__ import absolute_import

import ctypes
import copy
import warnings
import numpy as np
from .base import _LIB
from .base import mx_uint, NDArrayHandle, ExecutorHandle
from .base import check_call, c_array, py_str
from .ndarray import NDArray
from . import ndarray as nd

# those functions are not used here, we just import them to keep backward compatibility
# in case the end user calls them, as they originally lives here
# pylint: disable=unused-import
from .executor_manager import _split_input_slice, _check_arguments, _load_data, _load_label

def _monitor_callback_wrapper(callback):
    """A wrapper for the user-defined handle."""
    def callback_handle(name, array, _):
        """ ctypes function """
        callback(name, array)
    return callback_handle

class Executor(object):
    """Executor is the actual executing object of MXNet."""
    def __init__(self, handle, symbol, ctx, grad_req, group2ctx):
        """Constructor, used Symbol.bind and Symbol.simple_bind instead.

        Parameters
        ----------
        handle: ExecutorHandle
            ExecutorHandle generated by calling Bind.

        See Also
        --------
        Symbol.bind : to create executor.
        """
        if not isinstance(handle, ExecutorHandle):
            raise TypeError("Handle type error")
        self.handle = handle
        self.arg_arrays = []
        self.grad_arrays = []
        self.aux_arrays = []
        self.outputs = self._get_outputs()
        self._symbol = copy.deepcopy(symbol)
        self._arg_dict = None
        self._grad_dict = None
        self._aux_dict = None
        self._output_dict = None
        self._monitor_callback = None
        self._output_dirty = False
        self._ctx = copy.deepcopy(ctx)
        self._grad_req = copy.deepcopy(grad_req)
        self._group2ctx = copy.deepcopy(group2ctx)

    def __del__(self):
        check_call(_LIB.MXExecutorFree(self.handle))

    @staticmethod
    def _get_dict(names, ndarrays):
        """Get the dictionary given name and ndarray pairs."""
        nset = set()
        for nm in names:
            if nm in nset:
                raise ValueError('Duplicate names detected, %s' % str(names))
            nset.add(nm)
        return dict(zip(names, ndarrays))

    def _get_outputs(self):
        """List all the output NDArray.

        Returns
        -------
        A list of ndarray bound to the heads of executor.
        """
        out_size = mx_uint()
        handles = ctypes.POINTER(NDArrayHandle)()
        check_call(_LIB.MXExecutorOutputs(self.handle,
                                          ctypes.byref(out_size), ctypes.byref(handles)))
        return [NDArray(NDArrayHandle(handles[i])) for i in range(out_size.value)]

    def forward(self, is_train=False, **kwargs):
        """Calculate the outputs specified by the bound symbol.

        Parameters
        ----------
        is_train: bool, optional
            Whether this forward is for evaluation purpose. If True,
            a backward call is expected to follow. Otherwise following
            backward is invalid.

        **kwargs
            Additional specification of input arguments.

        Examples
        --------
        >>> # doing forward by specifying data
        >>> texec.forward(is_train=True, data=mydata)
        >>> # doing forward by not specifying things, but copy to the executor before hand
        >>> mydata.copyto(texec.arg_dict['data'])
        >>> texec.forward(is_train=True)
        >>> # doing forward by specifying data and get outputs
        >>> outputs = texec.forward(is_train=True, data=mydata)
        >>> print(outputs[0].asnumpy())
        """
        if len(kwargs) != 0:
            arg_dict = self.arg_dict
            for name, array in kwargs.items():
                if not isinstance(array, (NDArray, np.ndarray)):
                    raise ValueError('only accept keyword argument of NDArrays and numpy.ndarray')
                if name not in arg_dict:
                    raise TypeError('Unknown argument %s' % name)
                if arg_dict[name].shape != array.shape:
                    raise ValueError('Shape not match! Argument %s, need: %s, received: %s'
                                     %(name, str(arg_dict[name].shape), str(array.shape)))
                arg_dict[name][:] = array

        check_call(_LIB.MXExecutorForward(
            self.handle,
            ctypes.c_int(int(is_train))))

        if self._output_dirty:
            warnings.warn(
                "Calling forward the second time after forward(is_train=True) "
                "without calling backward first. Is this intended?", stacklevel=2)
        self._output_dirty = is_train

        return self.outputs

    def backward(self, out_grads=None):
        """Do backward pass to get the gradient of arguments.

        Parameters
        ----------
        out_grads : NDArray or list of NDArray or dict of str to NDArray, optional
            Gradient on the outputs to be propagated back.
            This parameter is only needed when bind is called
            on outputs that are not a loss function.
        """
        if out_grads is None:
            out_grads = []
        elif isinstance(out_grads, NDArray):
            out_grads = [out_grads]
        elif isinstance(out_grads, dict):
            out_grads = [out_grads[k] for k in self._symbol.list_outputs()]

        for obj in out_grads:
            if not isinstance(obj, NDArray):
                raise TypeError("inputs must be NDArray")
        ndarray = c_array(NDArrayHandle, [item.handle for item in out_grads])
        check_call(_LIB.MXExecutorBackward(
            self.handle,
            mx_uint(len(out_grads)),
            ndarray))

        if not self._output_dirty:
            warnings.warn(
                "Calling backward without calling forward(is_train=True) "
                "first. Behavior is undefined.", stacklevel=2)
        self._output_dirty = False

    def set_monitor_callback(self, callback):
        """Install callback.

        Parameters
        ----------
        callback : function
            Takes a string and an NDArrayHandle.
        """
        cb_type = ctypes.CFUNCTYPE(None, ctypes.c_char_p, NDArrayHandle, ctypes.c_void_p)
        self._monitor_callback = cb_type(_monitor_callback_wrapper(callback))
        check_call(_LIB.MXExecutorSetMonitorCallback(
            self.handle,
            self._monitor_callback,
            None))

    @property
    def arg_dict(self):
        """Get dictionary representation of argument arrrays.

        Returns
        -------
        arg_dict : dict of str to NDArray
            The dictionary that maps the names of arguments to NDArrays.

        Raises
        ------
        ValueError : if there are duplicated names in the arguments.
        """
        if self._arg_dict is None:
            self._arg_dict = Executor._get_dict(
                self._symbol.list_arguments(), self.arg_arrays)
        return self._arg_dict

    @property
    def grad_dict(self):
        """Get dictionary representation of gradient arrays.

        Returns
        -------
        grad_dict : dict of str to NDArray
            The dictionary that maps name of arguments to gradient arrays.
        """
        if self._grad_dict is None:
            self._grad_dict = Executor._get_dict(
                self._symbol.list_arguments(), self.grad_arrays)
        return self._grad_dict

    @property
    def aux_dict(self):
        """Get dictionary representation of auxiliary states arrays.

        Returns
        -------
        aux_dict : dict of str to NDArray
            The dictionary that maps name of auxiliary states to NDArrays.

        Raises
        ------
        ValueError : if there are duplicated names in the auxiliary states.
        """
        if self._aux_dict is None:
            self._aux_dict = Executor._get_dict(
                self._symbol.list_auxiliary_states(), self.aux_arrays)
        return self._aux_dict

    @property
    def output_dict(self):
        """Get dictionary representation of output arrays.

        Returns
        -------
        output_dict : dict of str to NDArray
            The dictionary that maps name of output names to NDArrays.

        Raises
        ------
        ValueError : if there are duplicated names in the outputs.
        """
        if self._output_dict is None:
            self._output_dict = Executor._get_dict(
                self._symbol.list_outputs(), self.outputs)
        return self._output_dict

    def copy_params_from(self, arg_params, aux_params=None, allow_extra_params=False):
        """Copy parameters from arg_params, aux_params into executor's internal array.

        Parameters
        ----------
        arg_params : dict of str to NDArray
            Parameters, dict of name to NDArray of arguments.

        aux_params : dict of str to NDArray, optional
            Parameters, dict of name to NDArray of auxiliary states.

        allow_extra_params : boolean, optional
            Whether allow extra parameters that are not needed by symbol.
            If this is True, no error will be thrown when arg_params or aux_params
            contain extra parameters that is not needed by the executor.

        Raises
        ------
        ValueError
            If there is additional parameters in the dict but ``allow_extra_params=False``.
        """
        for name, array in arg_params.items():
            if name in self.arg_dict:
                dst = self.arg_dict[name]
                array.astype(dst.dtype).copyto(dst)
            elif not allow_extra_params:
                raise ValueError('Find name \"%s\" that is not in the arguments' % name)

        if aux_params is None:
            return

        for name, array in aux_params.items():
            if name in self.aux_dict:
                dst = self.aux_dict[name]
                array.astype(dst.dtype).copyto(dst)
            elif not allow_extra_params:
                raise ValueError('Find name %s that is not in the auxiliary states' % name)

    def reshape(self, partial_shaping=False, allow_up_sizing=False, **kwargs):
        """Return a new executor with the same symbol and shared memory,
        but different input/output shapes.
        For runtime reshaping, variable length sequences, etc.
        The returned executor shares state with the current one,
        and cannot be used in parallel with it.

        Parameters
        ----------
        partial_shaping : bool
            Whether to allow changing the shape of unspecified arguments.
        allow_up_sizing : bool
            Whether to allow allocating new ndarrays that's larger than the original.
        kwargs : dict of string to tuple of int
            New shape for arguments.
        Returns
        -------
        exec : Executor
            A new executor that shares memory with self.
        """
        # pylint: disable=too-many-branches
        arg_shapes, _, aux_shapes = self._symbol.infer_shape(**kwargs)
        if arg_shapes is None:
            raise ValueError("Insufficient argument shapes provided.")

        new_arg_dict = {}
        new_grad_dict = {}
        for i, name in enumerate(self._symbol.list_arguments()):
            new_shape = arg_shapes[i]
            arr = self.arg_arrays[i]
            darr = None if self.grad_arrays is None else self.grad_arrays[i]
            if partial_shaping or name in kwargs or new_shape == arr.shape:
                if np.prod(new_shape) > np.prod(arr.shape):
                    assert allow_up_sizing, "New shape of arg:%s larger than original. "%name + \
                        "First making a big executor and then down sizing it " + \
                        "is more efficient than the reverse." + \
                        "If you really want to up size, set allow_up_sizing=True " + \
                        "to enable allocation of new arrays."
                    new_arg_dict[name] = nd.empty(new_shape, ctx=arr.context, dtype=arr.dtype)
                    if darr is not None:
                        new_grad_dict[name] = nd.empty(new_shape, ctx=darr.context, dtype=arr.dtype)
                else:
                    new_arg_dict[name] = arr.reshape(new_shape)
                    if darr is not None:
                        new_grad_dict[name] = darr.reshape(new_shape)
            else:
                raise AssertionError("Shape of unspecified array arg:%s changed. "%name + \
                    "This can cause the new executor to not share parameters " + \
                    "with the old one. Please check for error in network." +\
                    "If this is intended, set partial_shaping=True to suppress this warning.")

        new_aux_dict = {}
        for name, new_shape, arr in zip(self._symbol.list_auxiliary_states(),
                                        aux_shapes, self.aux_arrays):
            if partial_shaping or new_shape == arr.shape:
                if np.prod(new_shape) > np.prod(arr.shape):
                    assert allow_up_sizing, "New shape of arg:%s larger than original. "%name + \
                        "First making a big executor and then down sizing it " + \
                        "is more efficient than the reverse." + \
                        "If you really want to up size, set allow_up_sizing=True " + \
                        "to enable allocation of new arrays."
                    new_aux_dict[name] = nd.empty(new_shape, ctx=arr.context, dtype=arr.dtype)
                else:
                    new_aux_dict[name] = arr.reshape(new_shape)
            else:
                raise AssertionError("Shape of unspecified array aux:%s changed. "%name + \
                    "This can cause the new executor to not share parameters " + \
                    "with the old one. Please check for error in network." +\
                    "If this is intended, set partial_shaping=True to suppress this warning.")

        return self._symbol.bind(self._ctx,
                                 args=new_arg_dict,
                                 args_grad=new_grad_dict,
                                 grad_req=self._grad_req,
                                 aux_states=new_aux_dict,
                                 group2ctx=self._group2ctx,
                                 shared_exec=self)

    def debug_str(self):
        """Get a debug string about internal execution plan.

        Returns
        -------
        debug_str : string
            Debug string of the executor.
        """
        debug_str = ctypes.c_char_p()
        check_call(_LIB.MXExecutorPrint(
            self.handle, ctypes.byref(debug_str)))
        return py_str(debug_str.value)