# -*- coding: utf-8 -*-
"""
    sphinx.util.osutil
    ~~~~~~~~~~~~~~~~~~

    Operating system-related utility functions for Sphinx.

    :copyright: Copyright 2007-2016 by the Sphinx team, see AUTHORS.
    :license: BSD, see LICENSE for details.
"""
from __future__ import print_function

import os
import re
import sys
import time
import errno
import locale
import shutil
import filecmp
from os import path
import contextlib
from io import BytesIO, StringIO

from six import PY2, text_type

# Errnos that we need.
EEXIST = getattr(errno, 'EEXIST', 0)
ENOENT = getattr(errno, 'ENOENT', 0)
EPIPE  = getattr(errno, 'EPIPE', 0)
EINVAL = getattr(errno, 'EINVAL', 0)

# SEP separates path elements in the canonical file names
#
# Define SEP as a manifest constant, not so much because we expect it to change
# in the future as to avoid the suspicion that a stray "/" in the code is a
# hangover from more *nix-oriented origins.
SEP = "/"


def os_path(canonicalpath):
    return canonicalpath.replace(SEP, path.sep)


def canon_path(nativepath):
    """Return path in OS-independent form"""
    return nativepath.replace(path.sep, SEP)


def relative_uri(base, to):
    """Return a relative URL from ``base`` to ``to``."""
    if to.startswith(SEP):
        return to
    b2 = base.split(SEP)
    t2 = to.split(SEP)
    # remove common segments (except the last segment)
    for x, y in zip(b2[:-1], t2[:-1]):
        if x != y:
            break
        b2.pop(0)
        t2.pop(0)
    if b2 == t2:
        # Special case: relative_uri('f/index.html','f/index.html')
        # returns '', not 'index.html'
        return ''
    if len(b2) == 1 and t2 == ['']:
        # Special case: relative_uri('f/index.html','f/') should
        # return './', not ''
        return '.' + SEP
    return ('..' + SEP) * (len(b2)-1) + SEP.join(t2)


def ensuredir(path):
    """Ensure that a path exists."""
    try:
        os.makedirs(path)
    except OSError as err:
        # 0 for Jython/Win32
        if err.errno not in [0, EEXIST]:
            raise


# This function is same as os.walk of Python2.7 except a customization
# that check UnicodeError.
# The customization obstacle to replace the function with the os.walk.
def walk(top, topdown=True, followlinks=False):
    """Backport of os.walk from 2.6, where the *followlinks* argument was
    added.
    """
    names = os.listdir(top)

    dirs, nondirs = [], []
    for name in names:
        try:
            fullpath = path.join(top, name)
        except UnicodeError:
            print('%s:: ERROR: non-ASCII filename not supported on this '
                  'filesystem encoding %r, skipped.' % (name, fs_encoding),
                  file=sys.stderr)
            continue
        if path.isdir(fullpath):
            dirs.append(name)
        else:
            nondirs.append(name)

    if topdown:
        yield top, dirs, nondirs
    for name in dirs:
        fullpath = path.join(top, name)
        if followlinks or not path.islink(fullpath):
            for x in walk(fullpath, topdown, followlinks):
                yield x
    if not topdown:
        yield top, dirs, nondirs


def mtimes_of_files(dirnames, suffix):
    for dirname in dirnames:
        for root, dirs, files in os.walk(dirname):
            for sfile in files:
                if sfile.endswith(suffix):
                    try:
                        yield path.getmtime(path.join(root, sfile))
                    except EnvironmentError:
                        pass


def movefile(source, dest):
    """Move a file, removing the destination if it exists."""
    if os.path.exists(dest):
        try:
            os.unlink(dest)
        except OSError:
            pass
    os.rename(source, dest)


def copytimes(source, dest):
    """Copy a file's modification times."""
    st = os.stat(source)
    if hasattr(os, 'utime'):
        os.utime(dest, (st.st_atime, st.st_mtime))


def copyfile(source, dest):
    """Copy a file and its modification times, if possible.

    Note: ``copyfile`` skips copying if the file has not been changed"""
    if not path.exists(dest) or not filecmp.cmp(source, dest):
        shutil.copyfile(source, dest)
        try:
            # don't do full copystat because the source may be read-only
            copytimes(source, dest)
        except OSError:
            pass


no_fn_re = re.compile(r'[^a-zA-Z0-9_-]')


def make_filename(string):
    return no_fn_re.sub('', string) or 'sphinx'


def ustrftime(format, *args):
    # [DEPRECATED] strftime for unicode strings
    # It will be removed at Sphinx-1.5
    if not args:
        # If time is not specified, try to use $SOURCE_DATE_EPOCH variable
        # See https://wiki.debian.org/ReproducibleBuilds/TimestampsProposal
        source_date_epoch = os.getenv('SOURCE_DATE_EPOCH')
        if source_date_epoch is not None:
            time_struct = time.gmtime(float(source_date_epoch))
            args = [time_struct]
    if PY2:
        # if a locale is set, the time strings are encoded in the encoding
        # given by LC_TIME; if that is available, use it
        enc = locale.getlocale(locale.LC_TIME)[1] or 'utf-8'
        return time.strftime(text_type(format).encode(enc), *args).decode(enc)
    else:  # Py3
        # On Windows, time.strftime() and Unicode characters will raise UnicodeEncodeError.
        # http://bugs.python.org/issue8304
        try:
            return time.strftime(format, *args)
        except UnicodeEncodeError:
            r = time.strftime(format.encode('unicode-escape').decode(), *args)
            return r.encode().decode('unicode-escape')


def safe_relpath(path, start=None):
    try:
        return os.path.relpath(path, start)
    except ValueError:
        return path


fs_encoding = sys.getfilesystemencoding() or sys.getdefaultencoding()


def abspath(pathdir):
    pathdir = path.abspath(pathdir)
    if isinstance(pathdir, bytes):
        pathdir = pathdir.decode(fs_encoding)
    return pathdir


def getcwd():
    if hasattr(os, 'getcwdu'):
        return os.getcwdu()
    return os.getcwd()


@contextlib.contextmanager
def cd(target_dir):
    cwd = getcwd()
    try:
        os.chdir(target_dir)
        yield
    finally:
        os.chdir(cwd)


class FileAvoidWrite(object):
    """File-like object that buffers output and only writes if content changed.

    Use this class like when writing to a file to avoid touching the original
    file if the content hasn't changed. This is useful in scenarios where file
    mtime is used to invalidate caches or trigger new behavior.

    When writing to this file handle, all writes are buffered until the object
    is closed.

    Objects can be used as context managers.
    """
    def __init__(self, path):
        self._path = path
        self._io = None

    def write(self, data):
        if not self._io:
            if isinstance(data, text_type):
                self._io = StringIO()
            else:
                self._io = BytesIO()

        self._io.write(data)

    def close(self):
        """Stop accepting writes and write file, if needed."""
        if not self._io:
            raise Exception('FileAvoidWrite does not support empty files.')

        buf = self.getvalue()
        self._io.close()

        r_mode = 'r'
        w_mode = 'w'
        if isinstance(self._io, BytesIO):
            r_mode = 'rb'
            w_mode = 'wb'

        old_content = None

        try:
            with open(self._path, r_mode) as old_f:
                old_content = old_f.read()
                if old_content == buf:
                    return
        except IOError:
            pass

        with open(self._path, w_mode) as f:
            f.write(buf)

    def __enter__(self):
        return self

    def __exit__(self, type, value, traceback):
        self.close()

    def __getattr__(self, name):
        # Proxy to _io instance.
        if not self._io:
            raise Exception('Must write to FileAvoidWrite before other '
                            'methods can be used')

        return getattr(self._io, name)


def rmtree(path):
    if os.path.isdir(path):
        shutil.rmtree(path)
    else:
        os.remove(path)
