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

"""Circuit utility functions"""

import numpy as np


def summarize_circuits(circuits):
    """Summarize circuits based on QuantumCircuit, and five metrics are summarized.
        - Number of qubits
        - Number of classical bits
        - Number of operations
        - Depth of circuits
        - Counts of different gate operations

    The average statistic of the first four is provided if multiple circuits are provided.

    Args:
        circuits (QuantumCircuit or [QuantumCircuit]): the to-be-summarized circuits

    Returns:
        str: a formatted string records the summary
    """
    if not isinstance(circuits, list):
        circuits = [circuits]
    ret = ""
    ret += f"Submitting {len(circuits)} circuits.\n"
    ret += "============================================================================\n"
    stats = np.zeros(4)
    for i, circuit in enumerate(circuits):
        depth = circuit.depth()
        size = circuit.size()
        num_qubits = sum(reg.size for reg in circuit.qregs)
        num_clbits = sum(reg.size for reg in circuit.cregs)
        op_counts = circuit.count_ops()
        stats[0] += num_qubits
        stats[1] += num_clbits
        stats[2] += size
        stats[3] += depth
        ret = "".join(
            [
                ret,
                "{}-th circuit: {} qubits, {} classical bits and {} "
                "operations with depth {}\nop_counts: {}\n".format(
                    i, num_qubits, num_clbits, size, depth, op_counts
                ),
            ]
        )
    if len(circuits) > 1:
        stats /= len(circuits)
        ret = "".join(
            [
                ret,
                "Average: {:.2f} qubits, {:.2f} classical bits and {:.2f} "
                "operations with depth {:.2f}\n".format(stats[0], stats[1], stats[2], stats[3]),
            ]
        )
    ret += "============================================================================\n"
    return ret