# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

"""Disk utility module, no mixins here!

    examples:
    1) get disk size
    from mozharness.base.diskutils import DiskInfo, DiskutilsError
    ...
    try:
        DiskSize().get_size(path='/', unit='Mb')
    except DiskutilsError as e:
        # manage the exception e.g: log.error(e)
        pass
    log.info("%s" % di)


    2) convert disk size:
    from mozharness.base.diskutils import DiskutilsError, convert_to
    ...
    file_size = <function that gets file size in bytes>
    # convert file_size to GB
    try:
        file_size = convert_to(file_size, from_unit='bytes', to_unit='GB')
    except DiskutilsError as e:
        # manage the exception e.g: log.error(e)
        pass

"""
import ctypes
import logging
import os
import sys

from six import string_types

from mozharness.base.log import INFO, numeric_log_level

# use mozharness log
log = logging.getLogger(__name__)


class DiskutilsError(Exception):
    """Exception thrown by Diskutils module"""

    pass


def convert_to(size, from_unit, to_unit):
    """Helper method to convert filesystem sizes to kB/ MB/ GB/ TB/
    valid values for source_format and destination format are:
        * bytes
        * kB
        * MB
        * GB
        * TB
     returns: size converted from source_format to destination_format.
    """
    sizes = {
        "bytes": 1,
        "kB": 1024,
        "MB": 1024 * 1024,
        "GB": 1024 * 1024 * 1024,
        "TB": 1024 * 1024 * 1024 * 1024,
    }
    try:
        df = sizes[to_unit]
        sf = sizes[from_unit]
        # pylint --py3k W1619
        return size * sf / df
    except KeyError:
        raise DiskutilsError("conversion error: Invalid source or destination format")
    except TypeError:
        raise DiskutilsError("conversion error: size (%s) is not a number" % size)


class DiskInfo(object):
    """Stores basic information about the disk"""

    def __init__(self):
        self.unit = "bytes"
        self.free = 0
        self.used = 0
        self.total = 0

    def __str__(self):
        string = ["Disk space info (in %s)" % self.unit]
        string += ["total: %s" % self.total]
        string += ["used: %s" % self.used]
        string += ["free: %s" % self.free]
        return " ".join(string)

    def _to(self, unit):
        from_unit = self.unit
        to_unit = unit
        self.free = convert_to(self.free, from_unit=from_unit, to_unit=to_unit)
        self.used = convert_to(self.used, from_unit=from_unit, to_unit=to_unit)
        self.total = convert_to(self.total, from_unit=from_unit, to_unit=to_unit)
        self.unit = unit


class DiskSize(object):
    """DiskSize object"""

    @staticmethod
    def _posix_size(path):
        """returns the disk size in bytes
        disk size is relative to path
        """
        # we are on a POSIX system
        st = os.statvfs(path)
        disk_info = DiskInfo()
        disk_info.free = st.f_bavail * st.f_frsize
        disk_info.used = (st.f_blocks - st.f_bfree) * st.f_frsize
        disk_info.total = st.f_blocks * st.f_frsize
        return disk_info

    @staticmethod
    def _windows_size(path):
        """returns size in bytes, works only on windows platforms"""
        # we're on a non POSIX system (windows)
        # DLL call
        disk_info = DiskInfo()
        dummy = ctypes.c_ulonglong()  # needed by the dll call but not used
        total = ctypes.c_ulonglong()  # stores the total space value
        free = ctypes.c_ulonglong()  # stores the free space value
        # depending on path format (unicode or not) and python version (2 or 3)
        # we need to call GetDiskFreeSpaceExW or GetDiskFreeSpaceExA
        called_function = ctypes.windll.kernel32.GetDiskFreeSpaceExA
        if isinstance(path, string_types) or sys.version_info >= (3,):
            called_function = ctypes.windll.kernel32.GetDiskFreeSpaceExW
        # we're ready for the dll call. On error it returns 0
        if (
            called_function(
                path, ctypes.byref(dummy), ctypes.byref(total), ctypes.byref(free)
            )
            != 0
        ):
            # success, we can use the values returned by the dll call
            disk_info.free = free.value
            disk_info.total = total.value
            disk_info.used = total.value - free.value
        return disk_info

    @staticmethod
    def get_size(path, unit, log_level=INFO):
        """Disk info stats:
              total => size of the disk
              used  => space used
              free  => free space
        In case of error raises a DiskutilError Exception
        """
        try:
            # let's try to get the disk size using os module
            disk_info = DiskSize()._posix_size(path)
        except AttributeError:
            try:
                # os module failed. let's try to get the size using
                # ctypes.windll...
                disk_info = DiskSize()._windows_size(path)
            except AttributeError:
                # No luck! This is not a posix nor window platform
                # raise an exception
                raise DiskutilsError("Unsupported platform")

        disk_info._to(unit)
        lvl = numeric_log_level(log_level)
        log.log(lvl, msg="%s" % disk_info)
        return disk_info
