# Quellcode für qiskit.opflow.evolutions.evolution_factory

# This code is part of Qiskit.
#
# (C) Copyright IBM 2020.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.

""" EvolutionFactory Class """

from qiskit.opflow.operator_base import OperatorBase
from qiskit.opflow.evolutions.evolution_base import EvolutionBase
from qiskit.opflow.evolutions.pauli_trotter_evolution import PauliTrotterEvolution
from qiskit.opflow.evolutions.matrix_evolution import MatrixEvolution

[Doku]class EvolutionFactory:
""" A factory class for convenient automatic selection of an Evolution algorithm based on the
Operator to be converted.
"""

[Doku]    @staticmethod
def build(operator: OperatorBase = None) -> EvolutionBase:
r"""
A factory method for convenient automatic selection of an Evolution algorithm based on the
Operator to be converted.

Args:
operator: the Operator being evolved

Returns:
EvolutionBase: the EvolutionBase best suited to evolve operator.

Raises:
ValueError: If operator is not of a composition for which we know the best Evolution
method.

"""
primitive_strings = operator.primitive_strings()
if 'Matrix' in primitive_strings:
return MatrixEvolution()

elif 'Pauli' in primitive_strings or 'SparsePauliOp' in primitive_strings:
# TODO figure out what to do based on qubits and hamming weight.
return PauliTrotterEvolution()

else:
raise ValueError('Evolutions of mixed Operators not yet supported.')