# Copyright (C) 2007 by Intevation GmbH
# Authors:
# Bernhard Herzog <bh@intevation.de>
#
# This program is free software under the GPL (>=v2)
# Read the file COPYING coming with the software for details.

"""Collection of functions that didn't fit elsewhere"""

import os
import tempfile
import shutil

import run


def import_dotted_name(dotted_name):
    module = __import__(dotted_name)
    for name in dotted_name.split(".")[1:]:
        module = getattr(module, name)
    return module

def extract_value_for_key(lines, key):
    """Parses a sequence of strings for a key and returns the associated value

    The function determines the first string in lines that starts with
    key.  It returns the rest of the lines stripped of leading and
    trailing whitespace.

    If the key is not found in lines, the function returns None.
    """
    for line in lines:
        if line.startswith(key):
            return line[len(key):].strip()

def extract_lsm_version(lsm_file):
    return extract_value_for_key(open(lsm_file), "Version:")

def debian_changelog_version(changelog):
    """Returns the newest version in a debian changelog."""
    output = run.capture_output(["dpkg-parsechangelog",  "-l" + changelog])
    return extract_value_for_key(output.splitlines(), "Version:")


def ensure_directory(directory):
    """Creates directory and all its parents.

    Unlike os.makedirs, this function doesn't throw an exception
    """
    if not os.path.isdir(directory):
        os.makedirs(directory)


def copytree(src, dst, symlinks=False):
    """Recursively copy a directory tree using copy2().

    This version is basically the same as the one in the shutil module
    in the python standard library, however, it's OK if the destination
    directory already exists.

    If the optional symlinks flag is true, symbolic links in the
    source tree result in symbolic links in the destination tree; if
    it is false, the contents of the files pointed to by symbolic
    links are copied.
    """
    names = os.listdir(src)
    ensure_directory(dst)
    errors = []
    for name in names:
        srcname = os.path.join(src, name)
        dstname = os.path.join(dst, name)
        try:
            if symlinks and os.path.islink(srcname):
                linkto = os.readlink(srcname)
                os.symlink(linkto, dstname)
            elif os.path.isdir(srcname):
                copytree(srcname, dstname, symlinks)
            else:
                shutil.copy2(srcname, dstname)
            # XXX What about devices, sockets etc.?
        except (IOError, os.error), why:
            errors.append((srcname, dstname, why))
    if errors:
        raise Error, errors



def writefile(filename, contents, permissions=None):
    """Write contents to filename in an atomic way.

    The contents are first written to a temporary file in the same
    directory as filename.  Once the contents are written, the temporary
    file is closed and renamed to filename.

    The optional parameter permissions, if given, are the permissions
    for the new file.  By default, or if the parameter is None, the
    default permissions set by the tempfile.mkstemp are used which means
    that the file is only readable for the user that created the file.
    The permissions value is used as the second parameter to os.chmod.
    """
    dirname, basename = os.path.split(filename)
    fileno, tempname = tempfile.mkstemp("", basename, dirname)
    try:
        os.write(fileno, contents)
        if not contents.endswith("\n"):
            os.write(fileno, "\n")
        os.close(fileno)
        if permissions is not None:
            os.chmod(tempname, permissions)
        os.rename(tempname, filename)
    finally:
        if os.path.exists(tempname):
            os.remove(tempname)


class StatusFile(object):

    def __init__(self, filename):
        assert os.path.isabs(filename)
        self.filename = filename

    def read(self):
        f = open(self.filename)
        try:
            self.status = f.read()
        finally:
            f.close()

    def set(self, status, extra=""):
        ensure_directory(os.path.dirname(self.filename))
        writefile(self.filename, status + "\n" + extra)

    def get(self):
        self.read()
        return self.status.strip()