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"""Wrapper object for the file system / source tree."""

from __future__ import with_statement

import codecs
import errno
import exceptions
import os
import shutil
import tempfile
import time

class FileSystem(object):
    """FileSystem interface for webkitpy.

    Unless otherwise noted, all paths are allowed to be either absolute
    or relative."""

    def exists(self, path):
        """Return whether the path exists in the filesystem."""
        return os.path.exists(path)

    def isfile(self, path):
        """Return whether the path refers to a file."""
        return os.path.isfile(path)

    def isdir(self, path):
        """Return whether the path refers to a directory."""
        return os.path.isdir(path)

    def join(self, *comps):
        """Return the path formed by joining the components."""
        return os.path.join(*comps)

    def listdir(self, path):
        """Return the contents of the directory pointed to by path."""
        return os.listdir(path)

    def mkdtemp(self, **kwargs):
        """Create and return a uniquely named directory.

        This is like tempfile.mkdtemp, but if used in a with statement
        the directory will self-delete at the end of the block (if the
        directory is empty; non-empty directories raise errors). The
        directory can be safely deleted inside the block as well, if so
        desired."""
        class TemporaryDirectory(object):
            def __init__(self, **kwargs):
                self._kwargs = kwargs
                self._directory_path = None

            def __enter__(self):
                self._directory_path = tempfile.mkdtemp(**self._kwargs)
                return self._directory_path

            def __exit__(self, type, value, traceback):
                # Only self-delete if necessary.

                # FIXME: Should we delete non-empty directories?
                if os.path.exists(self._directory_path):
                    os.rmdir(self._directory_path)

        return TemporaryDirectory(**kwargs)

    def maybe_make_directory(self, *path):
        """Create the specified directory if it doesn't already exist."""
        try:
            os.makedirs(self.join(*path))
        except OSError, e:
            if e.errno != errno.EEXIST:
                raise

    class _WindowsError(exceptions.OSError):
        """Fake exception for Linux and Mac."""
        pass

    def remove(self, path, osremove=os.remove):
        """On Windows, if a process was recently killed and it held on to a
        file, the OS will hold on to the file for a short while.  This makes
        attempts to delete the file fail.  To work around that, this method
        will retry for a few seconds until Windows is done with the file."""
        try:
            exceptions.WindowsError
        except AttributeError:
            exceptions.WindowsError = FileSystem._WindowsError

        retry_timeout_sec = 3.0
        sleep_interval = 0.1
        while True:
            try:
                osremove(path)
                return True
            except exceptions.WindowsError, e:
                time.sleep(sleep_interval)
                retry_timeout_sec -= sleep_interval
                if retry_timeout_sec < 0:
                    raise e

    def remove_tree(self, path, ignore_errors=False):
        shutil.rmtree(path, ignore_errors)

    def read_binary_file(self, path):
        """Return the contents of the file at the given path as a byte string."""
        with file(path, 'rb') as f:
            return f.read()

    def read_text_file(self, path):
        """Return the contents of the file at the given path as a Unicode string.

        The file is read assuming it is a UTF-8 encoded file with no BOM."""
        with codecs.open(path, 'r', 'utf8') as f:
            return f.read()

    def write_binary_file(self, path, contents):
        """Write the contents to the file at the given location."""
        with file(path, 'wb') as f:
            f.write(contents)

    def write_text_file(self, path, contents):
        """Write the contents to the file at the given location.

        The file is written encoded as UTF-8 with no BOM."""
        with codecs.open(path, 'w', 'utf8') as f:
            f.write(contents)

    def copyfile(self, source, destination):
        """Copies the contents of the file at the given path to the destination
        path."""
        shutil.copyfile(source, destination)

    def files_under(self, path):
        """Return the list of all files under the given path."""
        return [self.join(path_to_file, filename)
            for (path_to_file, _, filenames) in os.walk(path)
            for filename in filenames]