# Copyright (c) 2012-2013 Red Hat, 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 logging
import os
import errno
import stat
import random
import time
from collections import defaultdict
from itertools import repeat
import os.path as os_path    # noqa
from eventlet import sleep
from gluster.swift.common.exceptions import FileOrDirNotFoundError, \
    NotDirectoryError, GlusterFileSystemOSError, GlusterFileSystemIOError
from swift.common.exceptions import DiskFileNoSpace


class Fake_file(object):
    def __init__(self, path):
        self.path = path

    def tell(self):
        return 0

    def read(self, count):
        return None

    def fileno(self):
        return -1

    def close(self):
        pass


def do_walk(*args, **kwargs):
    return os.walk(*args, **kwargs)


def do_write(fd, msg):
    try:
        cnt = os.write(fd, msg)
    except OSError as err:
        filename = get_filename_from_fd(fd)
        if err.errno in (errno.ENOSPC, errno.EDQUOT):
            do_log_rl("do_write(%d, msg[%d]) failed: %s : %s",
                      fd, len(msg), err, filename)
            raise DiskFileNoSpace()
        else:
            raise GlusterFileSystemOSError(
                err.errno, '%s, os.write("%s", ...)' % (err.strerror, fd))
    return cnt


def do_ismount(path):
    """
    Test whether a path is a mount point.

    This is code hijacked from C Python 2.6.8, adapted to remove the extra
    lstat() system call.
    """
    try:
        s1 = os.lstat(path)
    except os.error as err:
        if err.errno == errno.ENOENT:
            # It doesn't exist -- so not a mount point :-)
            return False
        else:
            raise GlusterFileSystemOSError(
                err.errno, '%s, os.lstat("%s")' % (err.strerror, path))

    if stat.S_ISLNK(s1.st_mode):
        # A symlink can never be a mount point
        return False

    try:
        s2 = os.lstat(os.path.join(path, '..'))
    except os.error as err:
        raise GlusterFileSystemOSError(
            err.errno, '%s, os.lstat("%s")' % (err.strerror,
                                               os.path.join(path, '..')))

    dev1 = s1.st_dev
    dev2 = s2.st_dev
    if dev1 != dev2:
        # path/.. on a different device as path
        return True

    ino1 = s1.st_ino
    ino2 = s2.st_ino
    if ino1 == ino2:
        # path/.. is the same i-node as path
        return True

    return False


def do_mkdir(path):
    try:
        os.mkdir(path)
    except OSError as err:
        if err.errno == errno.EEXIST:
            logging.warn("fs_utils: os.mkdir - path %s already exists", path)
        elif err.errno in (errno.ENOSPC, errno.EDQUOT):
            do_log_rl("do_mkdir(%s) failed: %s", path, err)
            raise DiskFileNoSpace()
        else:
            raise GlusterFileSystemOSError(
                err.errno, '%s, os.mkdir("%s")' % (err.strerror, path))


def do_listdir(path):
    try:
        buf = os.listdir(path)
    except OSError as err:
        raise GlusterFileSystemOSError(
            err.errno, '%s, os.listdir("%s")' % (err.strerror, path))
    return buf


def dir_empty(path):
    """
    Return true if directory is empty (or does not exist), false otherwise.

    :param path: Directory path
    :returns: True/False
    """
    try:
        files = do_listdir(path)
        return not files
    except GlusterFileSystemOSError as err:
        if err.errno == errno.ENOENT:
            raise FileOrDirNotFoundError()
        if err.errno == errno.ENOTDIR:
            raise NotDirectoryError()
        raise


def do_rmdir(path):
    try:
        os.rmdir(path)
    except OSError as err:
        raise GlusterFileSystemOSError(
            err.errno, '%s, os.rmdir("%s")' % (err.strerror, path))


def do_chown(path, uid, gid):
    try:
        os.chown(path, uid, gid)
    except OSError as err:
        raise GlusterFileSystemOSError(
            err.errno, '%s, os.chown("%s", %s, %s)' % (
                err.strerror, path, uid, gid))


def do_fchown(fd, uid, gid):
    try:
        os.fchown(fd, uid, gid)
    except OSError as err:
        raise GlusterFileSystemOSError(
            err.errno, '%s, os.fchown(%s, %s, %s)' % (
                err.strerror, fd, uid, gid))


_STAT_ATTEMPTS = 10


def do_stat(path):
    serr = None
    for i in range(0, _STAT_ATTEMPTS):
        try:
            stats = os.stat(path)
        except OSError as err:
            if err.errno == errno.EIO:
                # Retry EIO assuming it is a transient error from FUSE after a
                # short random sleep
                serr = err
                sleep(random.uniform(0.001, 0.005))
                continue
            if err.errno == errno.ENOENT:
                stats = None
            else:
                raise GlusterFileSystemOSError(
                    err.errno, '%s, os.stat("%s")[%d attempts]' % (
                        err.strerror, path, i))
        if i > 0:
            logging.warn("fs_utils.do_stat():"
                         " os.stat('%s') retried %d times (%s)",
                         path, i, 'success' if stats else 'failure')
        return stats
    else:
        raise GlusterFileSystemOSError(
            serr.errno, '%s, os.stat("%s")[%d attempts]' % (
                serr.strerror, path, _STAT_ATTEMPTS))


def do_fstat(fd):
    try:
        stats = os.fstat(fd)
    except OSError as err:
        raise GlusterFileSystemOSError(
            err.errno, '%s, os.fstat(%s)' % (err.strerror, fd))
    return stats


def do_open(path, flags, **kwargs):
    if isinstance(flags, int):
        try:
            fd = os.open(path, flags, **kwargs)
        except OSError as err:
            raise GlusterFileSystemOSError(
                err.errno, '%s, os.open("%s", %x, %r)' % (
                    err.strerror, path, flags, kwargs))
        return fd
    else:
        try:
            fp = open(path, flags, **kwargs)
        except IOError as err:
            raise GlusterFileSystemIOError(
                err.errno, '%s, open("%s", %s, %r)' % (
                    err.strerror, path, flags, kwargs))
        return fp


def do_close(fd):
    if isinstance(fd, file) or isinstance(fd, Fake_file):
        try:
            fd.close()
        except IOError as err:
            if err.errno in (errno.ENOSPC, errno.EDQUOT):
                do_log_rl("do_close(%s) failed: %s", fd, err)
                raise DiskFileNoSpace()
            else:
                raise GlusterFileSystemIOError(
                    err.errno, '%s, os.close(%s)' % (err.strerror, fd))
    else:
        try:
            os.close(fd)
        except OSError as err:
            if err.errno in (errno.ENOSPC, errno.EDQUOT):
                filename = get_filename_from_fd(fd)
                do_log_rl("do_close(%d) failed: %s : %s", fd, err, filename)
                raise DiskFileNoSpace()
            else:
                raise GlusterFileSystemOSError(
                    err.errno, '%s, os.close(%s)' % (err.strerror, fd))


def do_unlink(path, log=True):
    try:
        os.unlink(path)
    except OSError as err:
        if err.errno != errno.ENOENT:
            raise GlusterFileSystemOSError(
                err.errno, '%s, os.unlink("%s")' % (err.strerror, path))
        elif log:
            logging.warn("fs_utils: os.unlink failed on non-existent path: %s",
                         path)


def do_rename(old_path, new_path):
    try:
        os.rename(old_path, new_path)
    except OSError as err:
        raise GlusterFileSystemOSError(
            err.errno, '%s, os.rename("%s", "%s")' % (
                err.strerror, old_path, new_path))


def do_fsync(fd):
    try:
        os.fsync(fd)
    except OSError as err:
        raise GlusterFileSystemOSError(
            err.errno, '%s, os.fsync("%s")' % (err.strerror, fd))


def do_fdatasync(fd):
    try:
        os.fdatasync(fd)
    except OSError as err:
        raise GlusterFileSystemOSError(
            err.errno, '%s, os.fdatasync("%s")' % (err.strerror, fd))


def mkdirs(path):
    """
    Ensures the path is a directory or makes it if not. Errors if the path
    exists but is a file or on permissions failure.

    :param path: path to create
    """
    try:
        os.makedirs(path)
    except OSError as err:
        if err.errno == errno.EEXIST and os.path.isdir(path):
            return
        elif err.errno in (errno.ENOSPC, errno.EDQUOT):
            do_log_rl("mkdirs(%s) failed: %s", path, err)
            raise DiskFileNoSpace()
        else:
            raise GlusterFileSystemOSError(
                err.errno, '%s, os.makedirs("%s")' % (err.strerror, path))


def get_filename_from_fd(fd, verify=False):
    """
    Given the file descriptor, this method attempts to get the filename as it
    was when opened. This may not give accurate results in following cases:
    - file was renamed/moved/deleted after it was opened
    - file has multiple hardlinks

    :param fd: file descriptor of file opened
    :param verify: If True, performs additional checks using inode number
    """
    filename = None
    if isinstance(fd, int):
        try:
            filename = os.readlink("/proc/self/fd/" + str(fd))
        except OSError:
            pass

    if not verify:
        return filename

    # If verify = True, we compare st_dev and st_ino of file and fd.
    # This involves additional stat and fstat calls. So this is disabled
    # by default.
    if filename and fd:
        s_file = do_stat(filename)
        s_fd = do_fstat(fd)

        if s_file and s_fd:
            if (s_file.st_ino, s_file.st_dev) == (s_fd.st_ino, s_fd.st_dev):
                return filename

    return None


def static_var(varname, value):
    """Decorator function to create pseudo static variables."""
    def decorate(func):
        setattr(func, varname, value)
        return func
    return decorate

# Rate limit to emit log message once a second
_DO_LOG_RL_INTERVAL = 1.0


@static_var("counter", defaultdict(int))
@static_var("last_called", defaultdict(repeat(0.0).next))
def do_log_rl(msg, *args, **kwargs):
    """
    Rate limited logger.

    :param msg: String or message to be logged
    :param log_level: Possible values- error, warning, info, debug, critical
    """
    log_level = kwargs.get('log_level', "error")
    if log_level not in ("error", "warning", "info", "debug", "critical"):
        log_level = "error"

    do_log_rl.counter[msg] += 1  # Increment msg counter
    interval = time.time() - do_log_rl.last_called[msg]

    if interval >= _DO_LOG_RL_INTERVAL:
        # Prefix PID of process and message count to original log msg
        emit_msg = "[PID:" + str(os.getpid()) + "]" \
            + "[RateLimitedLog;Count:" + str(do_log_rl.counter[msg]) + "] " \
            + msg
        # log_level is a param for do_log_rl and not for logging.* methods
        try:
            del kwargs['log_level']
        except KeyError:
            pass

        getattr(logging, log_level)(emit_msg, *args, **kwargs)  # Emit msg
        do_log_rl.counter[msg] = 0  # Reset msg counter when message is emitted
        do_log_rl.last_called[msg] = time.time()  # Reset msg time