# -*- coding: utf-8 -*-
# pylint: disable=invalid-name

# Copyright 2017 IBM RESEARCH. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# =============================================================================

"""
Diagonal single qubit gate.
"""
from qiskit import CompositeGate
from qiskit import Gate
from qiskit import InstructionSet
from qiskit import QuantumCircuit
from qiskit import QuantumRegister
from qiskit.extensions.standard import header  # pylint: disable=unused-import


class U1Gate(Gate):
    """Diagonal single-qubit gate."""

    def __init__(self, theta, qubit, circ=None):
        """Create new diagonal single-qubit gate."""
        super(U1Gate, self).__init__("u1", [theta], [qubit], circ)

    def qasm(self):
        """Return OPENQASM string."""
        qubit = self.arg[0]
        theta = self.param[0]
        return self._qasmif("u1(%s) %s[%d];" % (
            theta, qubit[0].name, qubit[1]))

    def inverse(self):
        """Invert this gate."""
        self.param[0] = -self.param[0]
        return self

    def reapply(self, circ):
        """Reapply this gate to corresponding qubits in circ."""
        self._modifiers(circ.u1(self.param[0], self.arg[0]))


def u1(self, theta, q):
    """Apply u1 with angle theta to q."""
    if isinstance(q, QuantumRegister):
        gs = InstructionSet()
        for j in range(q.size):
            gs.add(self.u1(theta, (q, j)))
        return gs

    self._check_qubit(q)
    return self._attach(U1Gate(theta, q, self))


QuantumCircuit.u1 = u1
CompositeGate.u1 = u1
