#!/usr/bin/env python3
#
#  Copyright (C) 2018 Bloomberg Finance LP
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU Lesser General Public
#  License as published by the Free Software Foundation; either
#  version 2 of the License, or (at your option) any later version.
#
#  This library is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
#  Lesser General Public License for more details.
#
#  You should have received a copy of the GNU Lesser General Public
#  License along with this library. If not, see <http://www.gnu.org/licenses/>.
#
#  Authors:
#        Jim MacArthur <jim.macarthur@codethink.co.uk>

"""
FileBasedDirectory
=========

Implementation of the Directory class which backs onto a normal POSIX filing system.

See also: :ref:`sandboxing`.
"""

import os
import shutil
import stat
import time

from .directory import Directory, VirtualDirectoryError, _FileType
from .. import utils
from ..utils import link_files, copy_files, list_relative_paths, _get_link_mtime, _magic_timestamp
from ..utils import _set_deterministic_user, _set_deterministic_mtime
from ..utils import FileListResult

# FileBasedDirectory intentionally doesn't call its superclass constuctor,
# which is meant to be unimplemented.
# pylint: disable=super-init-not-called


class FileBasedDirectory(Directory):
    def __init__(self, external_directory=None):
        self.external_directory = external_directory

    def descend(self, *paths, create=False):
        """ See superclass Directory for arguments """

        current_dir = self

        for path in paths:
            # Skip empty path segments
            if not path:
                continue

            new_path = os.path.join(current_dir.external_directory, path)
            try:
                st = os.lstat(new_path)
                if not stat.S_ISDIR(st.st_mode):
                    raise VirtualDirectoryError("Cannot descend into '{}': '{}' is not a directory"
                                                .format(path, new_path))
            except FileNotFoundError:
                if create:
                    os.mkdir(new_path)
                else:
                    raise VirtualDirectoryError("Cannot descend into '{}': '{}' does not exist"
                                                .format(path, new_path))

            current_dir = FileBasedDirectory(new_path)

        return current_dir

    def import_files(self, external_pathspec, *,
                     filter_callback=None,
                     report_written=True, update_mtime=False,
                     can_link=False):
        """ See superclass Directory for arguments """

        from ._casbaseddirectory import CasBasedDirectory  # pylint: disable=cyclic-import

        if isinstance(external_pathspec, CasBasedDirectory):
            if can_link and not update_mtime:
                actionfunc = utils.safe_link
            else:
                actionfunc = utils.safe_copy

            import_result = FileListResult()
            self._import_files_from_cas(external_pathspec, actionfunc, filter_callback, result=import_result)
        else:
            if isinstance(external_pathspec, Directory):
                source_directory = external_pathspec.external_directory
            else:
                source_directory = external_pathspec

            if can_link and not update_mtime:
                import_result = link_files(source_directory, self.external_directory,
                                           filter_callback=filter_callback,
                                           ignore_missing=False, report_written=report_written)
            else:
                import_result = copy_files(source_directory, self.external_directory,
                                           filter_callback=filter_callback,
                                           ignore_missing=False, report_written=report_written)

        if update_mtime:
            cur_time = time.time()

            for f in import_result.files_written:
                os.utime(os.path.join(self.external_directory, f), times=(cur_time, cur_time))
        return import_result

    def import_single_file(self, external_pathspec):
        dstpath = os.path.join(self.external_directory, os.path.basename(external_pathspec))
        result = FileListResult()
        if os.path.exists(dstpath):
            result.ignored.append(dstpath)
        else:
            shutil.copyfile(external_pathspec, dstpath, follow_symlinks=False)
        return result

    def _mark_changed(self):
        pass

    def set_deterministic_mtime(self):
        _set_deterministic_mtime(self.external_directory)

    def set_deterministic_user(self):
        _set_deterministic_user(self.external_directory)

    def export_files(self, to_directory, *, can_link=False, can_destroy=False):
        if can_destroy:
            # Try a simple rename of the sandbox root; if that
            # doesnt cut it, then do the regular link files code path
            try:
                os.rename(self.external_directory, to_directory)
                return
            except OSError:
                # Proceed using normal link/copy
                pass

        os.makedirs(to_directory, exist_ok=True)
        if can_link:
            link_files(self.external_directory, to_directory)
        else:
            copy_files(self.external_directory, to_directory)

    # Add a directory entry deterministically to a tar file
    #
    # This function takes extra steps to ensure the output is deterministic.
    # First, it sorts the results of os.listdir() to ensure the ordering of
    # the files in the archive is the same.  Second, it sets a fixed
    # timestamp for each entry. See also https://bugs.python.org/issue24465.
    def export_to_tar(self, tarfile, destination_dir, mtime=_magic_timestamp):
        # We need directories here, including non-empty ones,
        # so list_relative_paths is not used.
        for filename in sorted(os.listdir(self.external_directory)):
            source_name = os.path.join(self.external_directory, filename)
            arcname = os.path.join(destination_dir, filename)
            tarinfo = tarfile.gettarinfo(source_name, arcname)
            tarinfo.mtime = mtime

            if tarinfo.isreg():
                with open(source_name, "rb") as f:
                    tarfile.addfile(tarinfo, f)
            elif tarinfo.isdir():
                tarfile.addfile(tarinfo)
                self.descend(*filename.split(os.path.sep)).export_to_tar(tarfile, arcname, mtime)
            else:
                tarfile.addfile(tarinfo)

    def is_empty(self):
        it = os.scandir(self.external_directory)
        return next(it, None) is None

    def mark_unmodified(self):
        """ Marks all files in this directory (recursively) as unmodified.
        """
        _set_deterministic_mtime(self.external_directory)

    def list_modified_paths(self):
        """Provide a list of relative paths which have been modified since the
        last call to mark_unmodified.

        Return value: List(str) - list of modified paths
        """
        return [f for f in list_relative_paths(self.external_directory)
                if _get_link_mtime(os.path.join(self.external_directory, f)) != _magic_timestamp]

    def list_relative_paths(self):
        """Provide a list of all relative paths.

        Return value: List(str) - list of all paths
        """

        return list_relative_paths(self.external_directory)

    def get_size(self):
        return utils._get_dir_size(self.external_directory)

    def __str__(self):
        # This returns the whole path (since we don't know where the directory started)
        # which exposes the sandbox directory; we will have to assume for the time being
        # that people will not abuse __str__.
        return self.external_directory

    def _get_underlying_directory(self) -> str:
        """ Returns the underlying (real) file system directory this
        object refers to. """
        return self.external_directory

    def _get_filetype(self, name=None):
        path = self.external_directory

        if name:
            path = os.path.join(path, name)

        st = os.lstat(path)
        if stat.S_ISDIR(st.st_mode):
            return _FileType.DIRECTORY
        elif stat.S_ISLNK(st.st_mode):
            return _FileType.SYMLINK
        elif stat.S_ISREG(st.st_mode):
            return _FileType.REGULAR_FILE
        else:
            return _FileType.SPECIAL_FILE

    def _import_files_from_cas(self, source_directory, actionfunc, filter_callback, *, path_prefix="", result):
        """ Import files from a CAS-based directory. """

        for name, entry in source_directory.index.items():
            # The destination filename, relative to the root where the import started
            relative_pathname = os.path.join(path_prefix, name)

            # The full destination path
            dest_path = os.path.join(self.external_directory, name)

            is_dir = entry.type == _FileType.DIRECTORY

            if is_dir:
                src_subdir = source_directory.descend(name)

                try:
                    create_subdir = not os.path.lexists(dest_path)
                    dest_subdir = self.descend(name, create=create_subdir)
                except VirtualDirectoryError:
                    filetype = self._get_filetype(name)
                    raise VirtualDirectoryError('Destination is a {}, not a directory: /{}'
                                                .format(filetype, relative_pathname))

                dest_subdir._import_files_from_cas(src_subdir, actionfunc, filter_callback,
                                                   path_prefix=relative_pathname, result=result)

            if filter_callback and not filter_callback(relative_pathname):
                if is_dir and create_subdir and dest_subdir.is_empty():
                    # Complete subdirectory has been filtered out, remove it
                    os.rmdir(dest_subdir.external_directory)

                # Entry filtered out, move to next
                continue

            if not is_dir:
                if os.path.lexists(dest_path):
                    # Collect overlaps
                    if not os.path.isdir(dest_path):
                        result.overwritten.append(relative_pathname)

                    if not utils.safe_remove(dest_path):
                        result.ignored.append(relative_pathname)
                        continue

                if entry.type == _FileType.REGULAR_FILE:
                    src_path = source_directory.cas_cache.objpath(entry.digest)
                    actionfunc(src_path, dest_path, result=result)
                    if entry.is_executable:
                        os.chmod(dest_path, stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR |
                                 stat.S_IRGRP | stat.S_IXGRP | stat.S_IROTH | stat.S_IXOTH)
                else:
                    assert entry.type == _FileType.SYMLINK
                    os.symlink(entry.target, dest_path)
                result.files_written.append(relative_pathname)