#!/usr/bin/env python

# Copyright (c) 2009, Giampaolo Rodola'. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Routines common to all posix systems."""

import os
import errno
import sys
import time
import glob

from psutil._compat import PY3, unicode
from psutil._error import TimeoutExpired
from psutil._common import nt_diskinfo, usage_percent, memoize


def pid_exists(pid):
    """Check whether pid exists in the current process table."""
    if pid < 0:
        return False
    try:
        os.kill(pid, 0)
    except OSError:
        e = sys.exc_info()[1]
        return e.errno == errno.EPERM
    else:
        return True

def wait_pid(pid, timeout=None):
    """Wait for process with pid 'pid' to terminate and return its
    exit status code as an integer.

    If pid is not a children of os.getpid() (current process) just
    waits until the process disappears and return None.

    If pid does not exist at all return None immediately.

    Raise TimeoutExpired on timeout expired.
    """
    def check_timeout(delay):
        if timeout is not None:
            if timer() >= stop_at:
                raise TimeoutExpired(pid)
        time.sleep(delay)
        return min(delay * 2, 0.04)

    timer = getattr(time, 'monotonic', time.time)
    if timeout is not None:
        waitcall = lambda: os.waitpid(pid, os.WNOHANG)
        stop_at = timer() + timeout
    else:
        waitcall = lambda: os.waitpid(pid, 0)

    delay = 0.0001
    while 1:
        try:
            retpid, status = waitcall()
        except OSError:
            err = sys.exc_info()[1]
            if err.errno == errno.EINTR:
                delay = check_timeout(delay)
                continue
            elif err.errno == errno.ECHILD:
                # This has two meanings:
                # - pid is not a child of os.getpid() in which case
                #   we keep polling until it's gone
                # - pid never existed in the first place
                # In both cases we'll eventually return None as we
                # can't determine its exit status code.
                while 1:
                    if pid_exists(pid):
                        delay = check_timeout(delay)
                    else:
                        return
            else:
                raise
        else:
            if retpid == 0:
                # WNOHANG was used, pid is still running
                delay = check_timeout(delay)
                continue
            # process exited due to a signal; return the integer of
            # that signal
            if os.WIFSIGNALED(status):
                return os.WTERMSIG(status)
            # process exited using exit(2) system call; return the
            # integer exit(2) system call has been called with
            elif os.WIFEXITED(status):
                return os.WEXITSTATUS(status)
            else:
                # should never happen
                raise RuntimeError("unknown process exit status")

def get_disk_usage(path):
    """Return disk usage associated with path."""
    try:
        st = os.statvfs(path)
    except UnicodeEncodeError:
        if not PY3 and isinstance(path, unicode):
            # this is a bug with os.statvfs() and unicode on
            # Python 2, see:
            # - https://code.google.com/p/psutil/issues/detail?id=416
            # - http://bugs.python.org/issue18695
            try:
                path = path.encode(sys.getfilesystemencoding())
            except UnicodeEncodeError:
                pass
            st = os.statvfs(path)
        else:
            raise
    free = (st.f_bavail * st.f_frsize)
    total = (st.f_blocks * st.f_frsize)
    used = (st.f_blocks - st.f_bfree) * st.f_frsize
    percent = usage_percent(used, total, _round=1)
    # NB: the percentage is -5% than what shown by df due to
    # reserved blocks that we are currently not considering:
    # http://goo.gl/sWGbH
    return nt_diskinfo(total, used, free, percent)

@memoize
def _get_terminal_map():
    ret = {}
    ls = glob.glob('/dev/tty*') + glob.glob('/dev/pts/*')
    for name in ls:
        assert name not in ret
        try:
            ret[os.stat(name).st_rdev] = name
        except OSError:
            err = sys.exc_info()[1]
            if err.errno != errno.ENOENT:
                raise
    return ret
