#
# Copyright 2017 the original author or authors.
#
# 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.
#
# """ ID generation utils """

from uuid import uuid4


BROADCAST_CORE_ID=hex(0xFFFF)[2:]

def get_next_core_id(current_id_in_hex_str):
    """
    :param current_id_in_hex_str: a hex string of the maximum core id 
    assigned without the leading 0x characters
    :return: current_id_in_hex_str + 1 in hex string 
    """
    if not current_id_in_hex_str or current_id_in_hex_str == '':
        return '0001'
    else:
        return format(int(current_id_in_hex_str, 16) + 1, '04x')


def create_cluster_logical_device_ids(core_id, switch_id):
    """
    Creates a logical device id and an OpenFlow datapath id that is unique 
    across the Voltha cluster. Both ids represents a 64 bits integer where 
    the lower 48 bits represents the switch id and the upper 16 bits  
    represents the core id.  
    :param core_id: string
    :return: cluster logical device id and OpenFlow datapath id
    """
    switch_id = format(switch_id, '012x')
    id = '{}{}'.format(format(int(core_id), '04x'), switch_id)
    hex_int = int(id, 16)
    return id, hex_int

def is_broadcast_core_id(id):
    assert id and len(id) == 16
    return id[:4] == BROADCAST_CORE_ID

def create_empty_broadcast_id():
    """
    Returns an empty broadcast id (ffff000000000000). The id is used to
    dispatch xPON objects across all the Voltha instances.
    :return: An empty broadcast id
    """
    return '{}{}'.format(BROADCAST_CORE_ID, '0'*12)

def create_cluster_id():
    """
    Returns an id that is common across all voltha instances.  The id  
    is a str of 64 bits.  The lower 48 bits refers to an id specific to that 
    object while the upper 16 bits refers a broadcast core_id
    :return: An common id across all Voltha instances
    """
    return '{}{}'.format(BROADCAST_CORE_ID, uuid4().hex[:12])

def create_cluster_device_id(core_id):
    """
    Creates a device id that is unique across the Voltha cluster.
    The device id is a str of 64 bits.  The lower 48 bits refers to the 
    device id while the upper 16 bits refers to the core id.
    :param core_id: string
    :return: cluster device id
    """
    return '{}{}'.format(format(int(core_id), '04x'), uuid4().hex[:12])


def get_core_id_from_device_id(device_id):
    # Device id is a string and the first 4 characters represent the core_id
    assert device_id and len(device_id) == 16
    # Get the leading 4 hexs and remove leading 0's
    return device_id[:4]


def get_core_id_from_logical_device_id(logical_device_id):
    """ 
    Logical Device id is a string and the first 4 characters represent the 
    core_id
    :param logical_device_id: 
    :return: core_id string
    """
    assert logical_device_id and len(logical_device_id) == 16
    # Get the leading 4 hexs and remove leading 0's
    return logical_device_id[:4]


def get_core_id_from_datapath_id(datapath_id):
    """
    datapath id is a uint64 where:
        - low 48 bits -> switch_id
        - high 16 bits -> core id
    :param datapath_id: 
    :return: core_id string
    """
    assert datapath_id
    # Get the hex string and remove the '0x' prefix
    id_in_hex_str = hex(datapath_id)[2:]
    assert len(id_in_hex_str) > 12
    return id_in_hex_str[:-12]