# This code is part of Qiskit.
#
# (C) Copyright IBM 2017, 2018.
#
# 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.

"""Test the Check CNOT direction pass"""

import unittest

import ddt

from qiskit import QuantumRegister, QuantumCircuit
from qiskit.circuit.library import CXGate, CZGate, ECRGate
from qiskit.transpiler.passes import CheckGateDirection
from qiskit.transpiler import CouplingMap, Target
from qiskit.converters import circuit_to_dag
from qiskit.test import QiskitTestCase


@ddt.ddt
class TestCheckGateDirection(QiskitTestCase):
    """Tests the CheckGateDirection pass"""

    def test_trivial_map(self):
        """Trivial map in a circuit without entanglement
        qr0:---[H]---

        qr1:---[H]---

        qr2:---[H]---

        CouplingMap map: None
        """
        qr = QuantumRegister(3, "qr")
        circuit = QuantumCircuit(qr)
        circuit.h(qr)
        coupling = CouplingMap()
        dag = circuit_to_dag(circuit)
        pass_ = CheckGateDirection(coupling)
        pass_.run(dag)
        self.assertTrue(pass_.property_set["is_direction_mapped"])

    def test_true_direction(self):
        """Mapped is easy to check
        qr0:---.--[H]--.--
               |       |
        qr1:--(+)------|--
                       |
        qr2:----------(+)-

        CouplingMap map: [1]<-[0]->[2]
        """
        qr = QuantumRegister(3, "qr")
        circuit = QuantumCircuit(qr)
        circuit.cx(qr[0], qr[1])
        circuit.h(qr[0])
        circuit.cx(qr[0], qr[2])
        coupling = CouplingMap([[0, 1], [0, 2]])
        dag = circuit_to_dag(circuit)

        pass_ = CheckGateDirection(coupling)
        pass_.run(dag)

        self.assertTrue(pass_.property_set["is_direction_mapped"])

    def test_true_direction_in_same_layer(self):
        """Two CXs distance_qubits 1 to each other, in the same layer
        qr0:--(+)--
               |
        qr1:---.---

        qr2:--(+)--
               |
        qr3:---.---

        CouplingMap map: [0]->[1]->[2]->[3]
        """
        qr = QuantumRegister(4, "qr")
        circuit = QuantumCircuit(qr)
        circuit.cx(qr[0], qr[1])
        circuit.cx(qr[2], qr[3])
        coupling = CouplingMap([[0, 1], [1, 2], [2, 3]])
        dag = circuit_to_dag(circuit)

        pass_ = CheckGateDirection(coupling)
        pass_.run(dag)

        self.assertTrue(pass_.property_set["is_direction_mapped"])

    def test_wrongly_mapped(self):
        """Needs [0]-[1] in a [0]--[2]--[1]
        qr0:--(+)--
               |
        qr1:---.---

        CouplingMap map: [0]->[2]->[1]
        """
        qr = QuantumRegister(2, "qr")
        circuit = QuantumCircuit(qr)
        circuit.cx(qr[0], qr[1])
        coupling = CouplingMap([[0, 2], [2, 1]])
        dag = circuit_to_dag(circuit)

        pass_ = CheckGateDirection(coupling)
        pass_.run(dag)

        self.assertFalse(pass_.property_set["is_direction_mapped"])

    def test_true_direction_undirected(self):
        """Mapped but with wrong direction
        qr0:--(+)-[H]--.--
               |       |
        qr1:---.-------|--
                       |
        qr2:----------(+)-

        CouplingMap map: [1]<-[0]->[2]
        """
        qr = QuantumRegister(3, "qr")
        circuit = QuantumCircuit(qr)
        circuit.cx(qr[0], qr[1])
        circuit.h(qr[0])
        circuit.cx(qr[2], qr[0])
        coupling = CouplingMap([[0, 1], [0, 2]])
        dag = circuit_to_dag(circuit)

        pass_ = CheckGateDirection(coupling)
        pass_.run(dag)

        self.assertFalse(pass_.property_set["is_direction_mapped"])

    def test_false_direction_in_same_layer_undirected(self):
        """Two CXs in the same layer, but one is wrongly directed
        qr0:--(+)--
               |
        qr1:---.---

        qr2:---.---
               |
        qr3:--(+)--

        CouplingMap map: [0]->[1]->[2]->[3]
        """
        qr = QuantumRegister(4, "qr")
        circuit = QuantumCircuit(qr)
        circuit.cx(qr[0], qr[1])
        circuit.cx(qr[3], qr[2])
        coupling = CouplingMap([[0, 1], [1, 2], [2, 3]])
        dag = circuit_to_dag(circuit)

        pass_ = CheckGateDirection(coupling)
        pass_.run(dag)

        self.assertFalse(pass_.property_set["is_direction_mapped"])

    def test_2q_barrier(self):
        """A 2q barrier should be ignored
        qr0:--|--
              |
        qr1:--|--

        CouplingMap map: None
        """
        qr = QuantumRegister(2, "qr")
        circuit = QuantumCircuit(qr)
        circuit.barrier(qr[0], qr[1])
        coupling = CouplingMap()
        dag = circuit_to_dag(circuit)

        pass_ = CheckGateDirection(coupling)
        pass_.run(dag)

        self.assertTrue(pass_.property_set["is_direction_mapped"])

    def test_ecr_gate(self):
        """A directional ECR gate is detected.
                ┌──────┐
           q_0: ┤1     ├
                │  ECR │
           q_1: ┤0     ├
                └──────┘

        CouplingMap map: [0, 1]
        """
        qr = QuantumRegister(2, "qr")
        circuit = QuantumCircuit(qr)
        circuit.ecr(qr[1], qr[0])
        coupling = CouplingMap()
        dag = circuit_to_dag(circuit)

        pass_ = CheckGateDirection(coupling)
        pass_.run(dag)

        self.assertFalse(pass_.property_set["is_direction_mapped"])

    @ddt.data(CXGate(), CZGate(), ECRGate())
    def test_target_static(self, gate):
        """Test that static 2q gates are detected correctly both if available and not available."""
        circuit = QuantumCircuit(2)
        circuit.append(gate, [0, 1], [])

        matching = Target(num_qubits=2)
        matching.add_instruction(gate, {(0, 1): None})
        pass_ = CheckGateDirection(None, target=matching)
        pass_(circuit)
        self.assertTrue(pass_.property_set["is_direction_mapped"])

        swapped = Target(num_qubits=2)
        swapped.add_instruction(gate, {(1, 0): None})
        pass_ = CheckGateDirection(None, target=swapped)
        pass_(circuit)
        self.assertFalse(pass_.property_set["is_direction_mapped"])

    def test_coupling_map_control_flow(self):
        """Test recursing into control-flow operations with a coupling map."""
        matching = CouplingMap.from_line(5, bidirectional=True)
        swapped = CouplingMap.from_line(5, bidirectional=False)

        circuit = QuantumCircuit(5, 1)
        circuit.h(0)
        circuit.measure(0, 0)
        with circuit.for_loop((2,)):
            circuit.cx(1, 0)

        pass_ = CheckGateDirection(matching)
        pass_(circuit)
        self.assertTrue(pass_.property_set["is_direction_mapped"])
        pass_ = CheckGateDirection(swapped)
        pass_(circuit)
        self.assertFalse(pass_.property_set["is_direction_mapped"])

        circuit = QuantumCircuit(5, 1)
        circuit.h(0)
        circuit.measure(0, 0)
        with circuit.for_loop((2,)):
            with circuit.if_test((circuit.clbits[0], True)) as else_:
                circuit.cz(3, 2)
            with else_:
                with circuit.while_loop((circuit.clbits[0], True)):
                    circuit.ecr(4, 3)

        pass_ = CheckGateDirection(matching)
        pass_(circuit)
        self.assertTrue(pass_.property_set["is_direction_mapped"])
        pass_ = CheckGateDirection(swapped)
        pass_(circuit)
        self.assertFalse(pass_.property_set["is_direction_mapped"])

    def test_target_control_flow(self):
        """Test recursing into control-flow operations with a coupling map."""
        swapped = Target(num_qubits=5)
        for gate in (CXGate(), CZGate(), ECRGate()):
            swapped.add_instruction(gate, {qargs: None for qargs in zip(range(4), range(1, 5))})

        matching = Target(num_qubits=5)
        for gate in (CXGate(), CZGate(), ECRGate()):
            matching.add_instruction(gate, {None: None})

        circuit = QuantumCircuit(5, 1)
        circuit.h(0)
        circuit.measure(0, 0)
        with circuit.for_loop((2,)):
            circuit.cx(1, 0)

        pass_ = CheckGateDirection(None, target=matching)
        pass_(circuit)
        self.assertTrue(pass_.property_set["is_direction_mapped"])
        pass_ = CheckGateDirection(None, target=swapped)
        pass_(circuit)
        self.assertFalse(pass_.property_set["is_direction_mapped"])

        circuit = QuantumCircuit(5, 1)
        circuit.h(0)
        circuit.measure(0, 0)
        with circuit.for_loop((2,)):
            with circuit.if_test((circuit.clbits[0], True)) as else_:
                circuit.cz(3, 2)
            with else_:
                with circuit.while_loop((circuit.clbits[0], True)):
                    circuit.ecr(4, 3)

        pass_ = CheckGateDirection(None, target=matching)
        pass_(circuit)
        self.assertTrue(pass_.property_set["is_direction_mapped"])
        pass_ = CheckGateDirection(None, target=swapped)
        pass_(circuit)
        self.assertFalse(pass_.property_set["is_direction_mapped"])


if __name__ == "__main__":
    unittest.main()
