# Copyright 2013 Rackspace, Inc.
#
# 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.

import abc
import functools
import os

import netifaces
import psutil
import six
import stevedore

from ironic_python_agent import encoding
from ironic_python_agent import errors
from ironic_python_agent.openstack.common import log
from ironic_python_agent import utils

_global_manager = None


class HardwareSupport(object):
    """These are just guidelines to suggest values that might be returned by
    calls to `evaluate_hardware_support`. No HardwareManager in mainline
    ironic-python-agent will ever offer a value greater than `MAINLINE`.
    Service Providers should feel free to return values greater than
    SERVICE_PROVIDER to distinguish between additional levels of support.
    """
    NONE = 0
    GENERIC = 1
    MAINLINE = 2
    SERVICE_PROVIDER = 3


class HardwareType(object):
    MAC_ADDRESS = 'mac_address'


class BlockDevice(encoding.Serializable):
    serializable_fields = ('name', 'size')

    def __init__(self, name, size):
        self.name = name
        self.size = size


class NetworkInterface(encoding.Serializable):
    serializable_fields = ('name', 'mac_address', 'switch_port_descr',
                           'switch_chassis_descr')

    def __init__(self, name, mac_addr):
        self.name = name
        self.mac_address = mac_addr
        # TODO(russellhaering): Pull these from LLDP
        self.switch_port_descr = None
        self.switch_chassis_descr = None


class CPU(encoding.Serializable):
    serializable_fields = ('model_name', 'frequency', 'count')

    def __init__(self, model_name, frequency, count):
        self.model_name = model_name
        self.frequency = frequency
        self.count = count


class Memory(encoding.Serializable):
    serializable_fields = ('total', )

    def __init__(self, total):
        self.total = total


@six.add_metaclass(abc.ABCMeta)
class HardwareManager(object):
    @abc.abstractmethod
    def evaluate_hardware_support(self):
        pass

    @abc.abstractmethod
    def list_network_interfaces(self):
        pass

    @abc.abstractmethod
    def get_cpus(self):
        pass

    @abc.abstractmethod
    def list_block_devices(self):
        pass

    @abc.abstractmethod
    def get_memory(self):
        pass

    @abc.abstractmethod
    def get_os_install_device(self):
        pass

    @abc.abstractmethod
    def erase_block_device(self, block_device):
        """Attempt to erase a block device.

        Implementations should detect the type of device and erase it in the
        most appropriate way possible.  Generic implementations should support
        common erase mechanisms such as ATA secure erase, or multi-pass random
        writes. Operators with more specific needs should override this method
        in order to detect and handle "interesting" cases, or delegate to the
        parent class to handle generic cases.

        For example: operators running ACME MagicStore (TM) cards alongside
        standard SSDs might check whether the device is a MagicStore and use a
        proprietary tool to erase that, otherwise call this method on their
        parent class. Upstream submissions of common functionality are
        encouraged.

        :param block_device: a BlockDevice indicating a device to be erased.
        :raises: BlockDeviceEraseError when an error occurs erasing a block
                 device, or if the block device is not supported.

        """
        pass

    def erase_devices(self):
        """Erase any device that holds user data.

        By default this will attempt to erase block devices. This method can be
        overridden in an implementation-specific hardware manager in order to
        erase additional hardware, although backwards-compatible upstream
        submissions are encouraged.
        """
        block_devices = self.list_block_devices()
        for block_device in block_devices:
            self.erase_block_device(block_device)

    def list_hardware_info(self):
        hardware_info = {}
        hardware_info['interfaces'] = self.list_network_interfaces()
        hardware_info['cpu'] = self.get_cpus()
        hardware_info['disks'] = self.list_block_devices()
        hardware_info['memory'] = self.get_memory()
        return hardware_info


class GenericHardwareManager(HardwareManager):
    def __init__(self):
        self.sys_path = '/sys'

        if os.path.isdir('/mnt/sys'):
            self.sys_path = '/mnt/sys'

    def evaluate_hardware_support(self):
        return HardwareSupport.GENERIC

    def _get_interface_info(self, interface_name):
        addr_path = '{0}/class/net/{1}/address'.format(self.sys_path,
                                                     interface_name)
        with open(addr_path) as addr_file:
            mac_addr = addr_file.read().strip()

        return NetworkInterface(interface_name, mac_addr)

    def get_ipv4_addr(self, interface_id):
        try:
            addrs = netifaces.ifaddresses(interface_id)
            return addrs[netifaces.AF_INET][0]['addr']
        except (ValueError, IndexError):
            # No default IPv4 address found
            return None

    def _is_device(self, interface_name):
        device_path = '{0}/class/net/{1}/device'.format(self.sys_path,
                                                      interface_name)
        return os.path.exists(device_path)

    def list_network_interfaces(self):
        iface_names = os.listdir('{0}/class/net'.format(self.sys_path))
        return [self._get_interface_info(name)
                for name in iface_names
                if self._is_device(name)]

    def get_cpus(self):
        model = None
        freq = None
        with open('/proc/cpuinfo') as f:
            lines = f.read()
            for line in lines.split('\n'):
                if model and freq:
                    break
                if not model and line.startswith('model name'):
                    model = line.split(':')[1].strip()
                if not freq and line.startswith('cpu MHz'):
                    freq = line.split(':')[1].strip()

        return CPU(model, freq, psutil.cpu_count())

    def get_memory(self):
        # psutil returns a long, force it to an int
        return Memory(int(psutil.phymem_usage().total))

    def list_block_devices(self):
        report = utils.execute('blockdev', '--report',
                               check_exit_code=[0])[0]
        lines = report.split('\n')
        lines = [line.split() for line in lines if line != '']
        startsec_idx = lines[0].index('StartSec')
        device_idx = lines[0].index('Device')
        size_idx = lines[0].index('Size')
        # If a device doesn't start at sector 0, assume it is a partition
        return [BlockDevice(line[device_idx],
                            int(line[size_idx]))
                for line
                in lines[1:] if int(line[startsec_idx]) == 0]

    def get_os_install_device(self):
        # Find the first device larger than 4GB, assume it is the OS disk
        # TODO(russellhaering): This isn't a valid assumption in all cases,
        #                       is there a more reasonable default behavior?
        block_devices = self.list_block_devices()
        block_devices.sort(key=lambda device: device.size)
        for device in block_devices:
            if device.size >= (4 * pow(1024, 3)):
                return device.name

    def erase_block_device(self, block_device):
        if self._ata_erase(block_device):
            return

        # NOTE(russell_h): Support for additional generic erase methods should
        # be added above this raise, in order of precedence.
        raise errors.BlockDeviceEraseError(('Unable to erase block device '
            '{0}: device is unsupported.').format(block_device.name))

    def _get_ata_security_lines(self, block_device):
        output = utils.execute('hdparm', '-I', block_device.name)[0]

        if '\nSecurity: ' not in output:
            return []

        # Get all lines after the 'Security: ' line
        security_and_beyond = output.split('\nSecurity: \n')[1]
        security_and_beyond_lines = security_and_beyond.split('\n')

        security_lines = []
        for line in security_and_beyond_lines:
            if line.startswith('\t'):
                security_lines.append(line.strip().replace('\t', ' '))
            else:
                break

        return security_lines

    def _ata_erase(self, block_device):
        security_lines = self._get_ata_security_lines(block_device)

        # If secure erase isn't supported return False so erase_block_device
        # can try another mechanism. Below here, if secure erase is supported
        # but fails in some way, error out (operators of hardware that supports
        # secure erase presumably expect this to work).
        if 'supported' not in security_lines:
            return False

        if 'enabled' in security_lines:
            raise errors.BlockDeviceEraseError(('Block device {0} already has '
                'a security password set').format(block_device.name))

        if 'not frozen' not in security_lines:
            raise errors.BlockDeviceEraseError(('Block device {0} is frozen '
                'and cannot be erased').format(block_device.name))

        utils.execute('hdparm', '--user-master', 'u', '--security-set-pass',
                      'NULL', block_device.name)
        utils.execute('hdparm', '--user-master', 'u', '--security-erase',
                      'NULL', block_device.name)

        # Verify that security is now 'not enabled'
        security_lines = self._get_ata_security_lines(block_device)
        if 'not enabled' not in security_lines:
            raise errors.BlockDeviceEraseError(('An unknown error occurred '
                'erasing block device {0}').format(block_device.name))

        return True


def _compare_extensions(ext1, ext2):
    mgr1 = ext1.obj
    mgr2 = ext2.obj
    return mgr2.evaluate_hardware_support() - mgr1.evaluate_hardware_support()


def get_manager():
    global _global_manager

    if not _global_manager:
        LOG = log.getLogger()
        extension_manager = stevedore.ExtensionManager(
            namespace='ironic_python_agent.hardware_managers',
            invoke_on_load=True)

        # There will always be at least one extension available (the
        # GenericHardwareManager).
        if six.PY2:
            preferred_extension = sorted(
                    extension_manager,
                    _compare_extensions)[0]
        else:
            preferred_extension = sorted(
                    extension_manager,
                    key=functools.cmp_to_key(_compare_extensions))[0]

        preferred_manager = preferred_extension.obj

        if preferred_manager.evaluate_hardware_support() <= 0:
            raise RuntimeError('No suitable HardwareManager could be found')

        LOG.info('selected hardware manager {0}'.format(
                 preferred_extension.entry_point_target))

        _global_manager = preferred_manager

    return _global_manager