# This code is part of Qiskit.
#
# (C) Copyright IBM 2017.
#
# 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.

"""
Quantum measurement in the computational basis.
"""
from qiskit.circuit.instruction import Instruction
from qiskit.circuit.quantumcircuit import QuantumCircuit
from qiskit.circuit.exceptions import CircuitError


class Measure(Instruction):
    """Quantum measurement in the computational basis."""

    def __init__(self):
        """Create new measurement instruction."""
        super().__init__("measure", 1, 1, [])

    def broadcast_arguments(self, qargs, cargs):
        qarg = qargs[0]
        carg = cargs[0]

        if len(carg) == len(qarg):
            for qarg, carg in zip(qarg, carg):
                yield [qarg], [carg]
        elif len(qarg) == 1 and carg:
            for each_carg in carg:
                yield qarg, [each_carg]
        else:
            raise CircuitError("register size error")


def measure(self, qubit, cbit):
    """Measure quantum bit into classical bit (tuples).

    Args:
        qubit (QuantumRegister|list|tuple): quantum register
        cbit (ClassicalRegister|list|tuple): classical register

    Returns:
        qiskit.Instruction: the attached measure instruction.

    Raises:
        CircuitError: if qubit is not in this circuit or bad format;
            if cbit is not in this circuit or not creg.
    """
    return self.append(Measure(), [qubit], [cbit])


QuantumCircuit.measure = measure
