# Copyright (c) 2017, Lawrence Livermore National Security, LLC. Produced at
# the Lawrence Livermore National Laboratory. LLNL-CODE-734707. All Rights
# reserved. See files LICENSE and NOTICE for details.
#
# This file is part of CEED, a collection of benchmarks, miniapps, software
# libraries and APIs for efficient high-order finite element and spectral
# element discretizations for exascale applications. For more information and
# source code availability see http://github.com/ceed.
#
# The CEED research is supported by the Exascale Computing Project 17-SC-20-SC,
# a collaborative effort of two U.S. Department of Energy organizations (Office
# of Science and the National Nuclear Security Administration) responsible for
# the planning and preparation of a capable exascale ecosystem, including
# software, applications, hardware, advanced system engineering and early
# testbed platforms, in support of the nation's exascale computing imperative.

from _ceed_cffi import ffi, lib
import tempfile
from abc import ABC
from .ceed_constants import REQUEST_IMMEDIATE, REQUEST_ORDERED, NOTRANSPOSE

# ------------------------------------------------------------------------------


class _OperatorBase(ABC):
    """Ceed Operator: composed FE-type operations on vectors."""

    # Attributes
    _ceed = ffi.NULL
    _pointer = ffi.NULL

    # Destructor
    def __del__(self):
        # libCEED call
        lib.CeedOperatorDestroy(self._pointer)

    # Representation
    def __repr__(self):
        return "<CeedOperator instance at " + hex(id(self)) + ">"

    # String conversion for print() to stdout
    def __str__(self):
        """View an Operator via print()."""

        # libCEED call
        with tempfile.NamedTemporaryFile() as key_file:
            with open(key_file.name, 'r+') as stream_file:
                stream = ffi.cast("FILE *", stream_file)

                lib.CeedOperatorView(self._pointer[0], stream)

                stream_file.seek(0)
                out_string = stream_file.read()

        return out_string

    # Apply CeedOperator
    def apply(self, u, v, request=REQUEST_IMMEDIATE):
        """Apply Operator to a vector.

           Args:
             u: Vector containing input state or CEED_VECTOR_NONE if there are no
                  active inputs
             v: Vector to store result of applying operator (must be distinct from u)
                  or CEED_VECTOR_NONE if there are no active outputs
             **request: Ceed request, default CEED_REQUEST_IMMEDIATE"""

        # libCEED call
        lib.CeedOperatorApply(self._pointer[0], u._pointer[0], v._pointer[0],
                              request)

    # Apply CeedOperator
    def apply_add(self, u, v, request=REQUEST_IMMEDIATE):
        """Apply Operator to a vector and add result to output vector.

           Args:
             u: Vector containing input state or CEED_VECTOR_NONE if there are no
                  active inputs
             v: Vector to sum in result of applying operator (must be distinct from u)
                  or CEED_VECTOR_NONE if there are no active outputs
             **request: Ceed request, default CEED_REQUEST_IMMEDIATE"""

        # libCEED call
        lib.CeedOperatorApplyAdd(self._pointer[0], u._pointer[0], v._pointer[0],
                                 request)

# ------------------------------------------------------------------------------


class Operator(_OperatorBase):
    """Ceed Operator: composed FE-type operations on vectors."""

    # Constructor
    def __init__(self, ceed, qf, dqf=None, dqfT=None):
        # CeedOperator object
        self._pointer = ffi.new("CeedOperator *")

        # Reference to Ceed
        self._ceed = ceed

        # libCEED call
        lib.CeedOperatorCreate(self._ceed._pointer[0], qf._pointer[0],
                               dqf._pointer[0] if dqf else ffi.NULL,
                               dqfT._pointer[0] if dqfT else ffi.NULL,
                               self._pointer)

    # Add field to CeedOperator
    def set_field(self, fieldname, restriction, basis, vector):
        """Provide a field to an Operator for use by its QFunction.

           Args:
             fieldname: name of the field (to be matched with the same name used
                          by QFunction)
             restriction: ElemRestriction
             basis: Basis in which the field resides or CEED_BASIS_COLLOCATED
                      if collocated with quadrature points
             vector: Vector to be used by Operator or CEED_VECTOR_ACTIVE
                       if field is active or CEED_VECTOR_NONE if using
                       CEED_EVAL_WEIGHT in the QFunction"""

        # libCEED call
        fieldnameAscii = ffi.new("char[]", fieldname.encode('ascii'))
        lib.CeedOperatorSetField(self._pointer[0], fieldnameAscii,
                                 restriction._pointer[0], basis._pointer[0],
                                 vector._pointer[0])

# ------------------------------------------------------------------------------


class CompositeOperator(_OperatorBase):
    """Ceed Composite Operator: composition of multiple Operators."""

    # Constructor
    def __init__(self, ceed):
        # CeedOperator object
        self._pointer = ffi.new("CeedOperator *")

        # Reference to Ceed
        self._ceed = ceed
        # libCEED call
        lib.CeedCompositeOperatorCreate(self._ceed._pointer[0], self._pointer)

    # Add sub operators
    def add_sub(self, subop):
        """Add a sub-operator to a composite CeedOperator.

           Args:
             subop: sub-operator Operator"""

        # libCEED call
        lib.CeedCompositeOperatorAddSub(self._pointer[0], subop._pointer[0])

# ------------------------------------------------------------------------------