# vfs.py - Mercurial 'vfs' classes

#

#  Copyright Matt Mackall <mpm@selenic.com>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import contextlib

import errno

import os

import shutil

import stat

import threading

from .i18n import _

from . import (

    encoding,

    error,

    pathutil,

    pycompat,

    util,

)

def _avoidambig(path, oldstat):

    """Avoid file stat ambiguity forcibly

    This function causes copying ``path`` file, if it is owned by

    another (see issue5418 and issue5584 for detail).

    """

    def checkandavoid():

        newstat = util.filestat.frompath(path)

        # return whether file stat ambiguity is (already) avoided

        return (not newstat.isambig(oldstat) or

                newstat.avoidambig(path, oldstat))

    if not checkandavoid():

        # simply copy to change owner of path to get privilege to

        # advance mtime (see issue5418)

        util.rename(util.mktempcopy(path), path)

        checkandavoid()

class abstractvfs(object):

    """Abstract base class; cannot be instantiated"""

    def __init__(self, *args, **kwargs):

        '''Prevent instantiation; don't call this from subclasses.'''

        raise NotImplementedError('attempted instantiating ' + str(type(self)))

    def _auditpath(self, path, mode):

        pass

    def tryread(self, path):

        '''gracefully return an empty string for missing files'''

        try:

            return self.read(path)

        except IOError as inst:

            if inst.errno != errno.ENOENT:

                raise

        return ""

    def tryreadlines(self, path, mode='rb'):

        '''gracefully return an empty array for missing files'''

        try:

            return self.readlines(path, mode=mode)

        except IOError as inst:

            if inst.errno != errno.ENOENT:

                raise

        return []

    @util.propertycache

    def open(self):

        '''Open ``path`` file, which is relative to vfs root.

        Newly created directories are marked as "not to be indexed by

        the content indexing service", if ``notindexed`` is specified

        for "write" mode access.

        '''

        return self.__call__

    def read(self, path):

        with self(path, 'rb') as fp:

            return fp.read()

    def readlines(self, path, mode='rb'):

        with self(path, mode=mode) as fp:

            return fp.readlines()

    def write(self, path, data, backgroundclose=False, **kwargs):

        with self(path, 'wb', backgroundclose=backgroundclose, **kwargs) as fp:

            return fp.write(data)

    def writelines(self, path, data, mode='wb', notindexed=False):

        with self(path, mode=mode, notindexed=notindexed) as fp:

            return fp.writelines(data)

    def append(self, path, data):

        with self(path, 'ab') as fp:

            return fp.write(data)

    def basename(self, path):

        """return base element of a path (as os.path.basename would do)

        This exists to allow handling of strange encoding if needed."""

        return os.path.basename(path)

    def chmod(self, path, mode):

        return os.chmod(self.join(path), mode)

    def dirname(self, path):

        """return dirname element of a path (as os.path.dirname would do)

        This exists to allow handling of strange encoding if needed."""

        return os.path.dirname(path)

    def exists(self, path=None):

        return os.path.exists(self.join(path))

    def fstat(self, fp):

        return util.fstat(fp)

    def isdir(self, path=None):

        return os.path.isdir(self.join(path))

    def isfile(self, path=None):

        return os.path.isfile(self.join(path))

    def islink(self, path=None):

        return os.path.islink(self.join(path))

    def isfileorlink(self, path=None):

        '''return whether path is a regular file or a symlink

        Unlike isfile, this doesn't follow symlinks.'''

        try:

            st = self.lstat(path)

        except OSError:

            return False

        mode = st.st_mode

        return stat.S_ISREG(mode) or stat.S_ISLNK(mode)

    def reljoin(self, *paths):

        """join various elements of a path together (as os.path.join would do)

        The vfs base is not injected so that path stay relative. This exists

        to allow handling of strange encoding if needed."""

        return os.path.join(*paths)

    def split(self, path):

        """split top-most element of a path (as os.path.split would do)

        This exists to allow handling of strange encoding if needed."""

        return os.path.split(path)

    def lexists(self, path=None):

        return os.path.lexists(self.join(path))

    def lstat(self, path=None):

        return os.lstat(self.join(path))

    def listdir(self, path=None):

        return os.listdir(self.join(path))

    def makedir(self, path=None, notindexed=True):

        return util.makedir(self.join(path), notindexed)

    def makedirs(self, path=None, mode=None):

        return util.makedirs(self.join(path), mode)

    def makelock(self, info, path):

        return util.makelock(info, self.join(path))

    def mkdir(self, path=None):

        return os.mkdir(self.join(path))

    def mkstemp(self, suffix='', prefix='tmp', dir=None):

        fd, name = pycompat.mkstemp(suffix=suffix, prefix=prefix,

                                    dir=self.join(dir))

        dname, fname = util.split(name)

        if dir:

            return fd, os.path.join(dir, fname)

        else:

            return fd, fname

    def readdir(self, path=None, stat=None, skip=None):

        return util.listdir(self.join(path), stat, skip)

    def readlock(self, path):

        return util.readlock(self.join(path))

    def rename(self, src, dst, checkambig=False):

        """Rename from src to dst

        checkambig argument is used with util.filestat, and is useful

        only if destination file is guarded by any lock

        (e.g. repo.lock or repo.wlock).

        To avoid file stat ambiguity forcibly, checkambig=True involves

        copying ``src`` file, if it is owned by another. Therefore, use

        checkambig=True only in limited cases (see also issue5418 and

        issue5584 for detail).

        """

        srcpath = self.join(src)

        dstpath = self.join(dst)

        oldstat = checkambig and util.filestat.frompath(dstpath)

        if oldstat and oldstat.stat:

            ret = util.rename(srcpath, dstpath)

            _avoidambig(dstpath, oldstat)

            return ret

        return util.rename(srcpath, dstpath)

    def readlink(self, path):

        return util.readlink(self.join(path))

    def removedirs(self, path=None):

        """Remove a leaf directory and all empty intermediate ones

        """

        return util.removedirs(self.join(path))

    def rmdir(self, path=None):

        """Remove an empty directory."""

        return os.rmdir(self.join(path))

    def rmtree(self, path=None, ignore_errors=False, forcibly=False):

        """Remove a directory tree recursively

        If ``forcibly``, this tries to remove READ-ONLY files, too.

        """

        if forcibly:

            def onerror(function, path, excinfo):

                if function is not os.remove:

                    raise

                # read-only files cannot be unlinked under Windows

                s = os.stat(path)

                if (s.st_mode & stat.S_IWRITE) != 0:

                    raise

                os.chmod(path, stat.S_IMODE(s.st_mode) | stat.S_IWRITE)

                os.remove(path)

        else:

            onerror = None

        return shutil.rmtree(self.join(path),

                             ignore_errors=ignore_errors, onerror=onerror)

    def setflags(self, path, l, x):

        return util.setflags(self.join(path), l, x)

    def stat(self, path=None):

        return os.stat(self.join(path))

    def unlink(self, path=None):

        return util.unlink(self.join(path))

    def tryunlink(self, path=None):

        """Attempt to remove a file, ignoring missing file errors."""

        util.tryunlink(self.join(path))

    def unlinkpath(self, path=None, ignoremissing=False, rmdir=True):

        return util.unlinkpath(self.join(path), ignoremissing=ignoremissing,

                               rmdir=rmdir)

    def utime(self, path=None, t=None):

        return os.utime(self.join(path), t)

    def walk(self, path=None, onerror=None):

        """Yield (dirpath, dirs, files) tuple for each directories under path

        ``dirpath`` is relative one from the root of this vfs. This

        uses ``os.sep`` as path separator, even you specify POSIX

        style ``path``.

        "The root of this vfs" is represented as empty ``dirpath``.

        """

        root = os.path.normpath(self.join(None))

        # when dirpath == root, dirpath[prefixlen:] becomes empty

        # because len(dirpath) < prefixlen.

        prefixlen = len(pathutil.normasprefix(root))

        for dirpath, dirs, files in os.walk(self.join(path), onerror=onerror):

            yield (dirpath[prefixlen:], dirs, files)

    @contextlib.contextmanager

    def backgroundclosing(self, ui, expectedcount=-1):

        """Allow files to be closed asynchronously.

        When this context manager is active, ``backgroundclose`` can be passed

        to ``__call__``/``open`` to result in the file possibly being closed

        asynchronously, on a background thread.

        """

        # Sharing backgroundfilecloser between threads is complex and using

        # multiple instances puts us at risk of running out of file descriptors

        # only allow to use backgroundfilecloser when in main thread.

        if not isinstance(threading.currentThread(), threading._MainThread):

            yield

            return

        vfs = getattr(self, 'vfs', self)

        if getattr(vfs, '_backgroundfilecloser', None):

            raise error.Abort(

                _('can only have 1 active background file closer'))

        with backgroundfilecloser(ui, expectedcount=expectedcount) as bfc:

            try:

                vfs._backgroundfilecloser = bfc

                yield bfc

            finally:

                vfs._backgroundfilecloser = None

class vfs(abstractvfs):

    '''Operate files relative to a base directory

    This class is used to hide the details of COW semantics and

    remote file access from higher level code.

    'cacheaudited' should be enabled only if (a) vfs object is short-lived, or

    (b) the base directory is managed by hg and considered sort-of append-only.

    See pathutil.pathauditor() for details.

    '''

    def __init__(self, base, audit=True, cacheaudited=False, expandpath=False,

                 realpath=False):

        if expandpath:

            base = util.expandpath(base)

        if realpath:

            base = os.path.realpath(base)

        self.base = base

        self._audit = audit

        if audit:

            self.audit = pathutil.pathauditor(self.base, cached=cacheaudited)

        else:

            self.audit = (lambda path, mode=None: True)

        self.createmode = None

        self._trustnlink = None

    @util.propertycache

    def _cansymlink(self):

        return util.checklink(self.base)

    @util.propertycache

    def _chmod(self):

        return util.checkexec(self.base)

    def _fixfilemode(self, name):

        if self.createmode is None or not self._chmod:

            return

        os.chmod(name, self.createmode & 0o666)

    def _auditpath(self, path, mode):

        if self._audit:

            if os.path.isabs(path) and path.startswith(self.base):

                path = os.path.relpath(path, self.base)

            r = util.checkosfilename(path)

            if r:

                raise error.Abort("%s: %r" % (r, path))

            self.audit(path, mode=mode)

    def __call__(self, path, mode="r", atomictemp=False, notindexed=False,

                 backgroundclose=False, checkambig=False, auditpath=True,

                 makeparentdirs=True):

        '''Open ``path`` file, which is relative to vfs root.

        By default, parent directories are created as needed. Newly created

        directories are marked as "not to be indexed by the content indexing

        service", if ``notindexed`` is specified for "write" mode access.

        Set ``makeparentdirs=False`` to not create directories implicitly.

        If ``backgroundclose`` is passed, the file may be closed asynchronously.

        It can only be used if the ``self.backgroundclosing()`` context manager

        is active. This should only be specified if the following criteria hold:

        1. There is a potential for writing thousands of files. Unless you

           are writing thousands of files, the performance benefits of

           asynchronously closing files is not realized.

        2. Files are opened exactly once for the ``backgroundclosing``

           active duration and are therefore free of race conditions between

           closing a file on a background thread and reopening it. (If the

           file were opened multiple times, there could be unflushed data

           because the original file handle hasn't been flushed/closed yet.)