##############################################################################
# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
# Produced at the Lawrence Livermore National Laboratory.
#
# This file is part of Spack.
# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
# LLNL-CODE-647188
#
# For details, see https://github.com/llnl/spack
# Please also see the LICENSE file for our notice and the LGPL.
#
# 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) version 2.1, February 1999.
#
# This program 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 terms and
# conditions of 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 program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
##############################################################################
import os
import glob
import re
import shutil
import stat
import errno
import getpass
from contextlib import contextmanager
import subprocess
import fileinput

import llnl.util.tty as tty

__all__ = ['set_install_permissions', 'install', 'install_tree',
           'traverse_tree',
           'expand_user', 'working_dir', 'touch', 'touchp', 'mkdirp',
           'force_remove', 'join_path', 'ancestor', 'can_access',
           'filter_file',
           'FileFilter', 'change_sed_delimiter', 'is_exe', 'force_symlink',
           'set_executable', 'copy_mode', 'unset_executable_mode',
           'remove_dead_links', 'remove_linked_tree', 'find_library_path',
           'fix_darwin_install_name', 'to_link_flags', 'to_lib_name']


def filter_file(regex, repl, *filenames, **kwargs):
    """Like sed, but uses python regular expressions.

       Filters every line of each file through regex and replaces the file
       with a filtered version.  Preserves mode of filtered files.

       As with re.sub, ``repl`` can be either a string or a callable.
       If it is a callable, it is passed the match object and should
       return a suitable replacement string.  If it is a string, it
       can contain ``\1``, ``\2``, etc. to represent back-substitution
       as sed would allow.

       Keyword Options:
         string[=False]         If True, treat regex as a plain string.
         backup[=True]          Make backup file(s) suffixed with ~
         ignore_absent[=False]  Ignore any files that don't exist.
    """
    string = kwargs.get('string', False)
    backup = kwargs.get('backup', True)
    ignore_absent = kwargs.get('ignore_absent', False)

    # Allow strings to use \1, \2, etc. for replacement, like sed
    if not callable(repl):
        unescaped = repl.replace(r'\\', '\\')

        def replace_groups_with_groupid(m):
            def groupid_to_group(x):
                return m.group(int(x.group(1)))
            return re.sub(r'\\([1-9])', groupid_to_group, unescaped)
        repl = replace_groups_with_groupid

    if string:
        regex = re.escape(regex)

    for filename in filenames:
        backup_filename = filename + "~"

        if ignore_absent and not os.path.exists(filename):
            continue

        # Create backup file. Don't overwrite an existing backup
        # file in case this file is being filtered multiple times.
        if not os.path.exists(backup_filename):
            shutil.copy(filename, backup_filename)

        try:
            for line in fileinput.input(filename, inplace=True):
                print(re.sub(regex, repl, line.rstrip('\n')))
        except:
            # clean up the original file on failure.
            shutil.move(backup_filename, filename)
            raise

        finally:
            if not backup:
                os.remove(backup_filename)


class FileFilter(object):
    """Convenience class for calling filter_file a lot."""
    def __init__(self, *filenames):
        self.filenames = filenames

    def filter(self, regex, repl, **kwargs):
        return filter_file(regex, repl, *self.filenames, **kwargs)


def change_sed_delimiter(old_delim, new_delim, *filenames):
    """Find all sed search/replace commands and change the delimiter.
       e.g., if the file contains seds that look like 's///', you can
       call change_sed_delimiter('/', '@', file) to change the
       delimiter to '@'.

       NOTE that this routine will fail if the delimiter is ' or ".
       Handling those is left for future work.
    """
    assert(len(old_delim) == 1)
    assert(len(new_delim) == 1)

    # TODO: handle these cases one day?
    assert(old_delim != '"')
    assert(old_delim != "'")
    assert(new_delim != '"')
    assert(new_delim != "'")

    whole_lines = "^s@([^@]*)@(.*)@[gIp]$"
    whole_lines = whole_lines.replace('@', old_delim)

    single_quoted = r"'s@((?:\\'|[^@'])*)@((?:\\'|[^'])*)@[gIp]?'"
    single_quoted = single_quoted.replace('@', old_delim)

    double_quoted = r'"s@((?:\\"|[^@"])*)@((?:\\"|[^"])*)@[gIp]?"'
    double_quoted = double_quoted.replace('@', old_delim)

    repl = r's@\1@\2@g'
    repl = repl.replace('@', new_delim)

    for f in filenames:
        filter_file(whole_lines, repl, f)
        filter_file(single_quoted, "'%s'" % repl, f)
        filter_file(double_quoted, '"%s"' % repl, f)


def set_install_permissions(path):
    """Set appropriate permissions on the installed file."""
    if os.path.isdir(path):
        os.chmod(path, 0755)
    else:
        os.chmod(path, 0644)


def copy_mode(src, dest):
    src_mode = os.stat(src).st_mode
    dest_mode = os.stat(dest).st_mode
    if src_mode & stat.S_IXUSR:
        dest_mode |= stat.S_IXUSR
    if src_mode & stat.S_IXGRP:
        dest_mode |= stat.S_IXGRP
    if src_mode & stat.S_IXOTH:
        dest_mode |= stat.S_IXOTH
    os.chmod(dest, dest_mode)


def unset_executable_mode(path):
    mode = os.stat(path).st_mode
    mode &= ~stat.S_IXUSR
    mode &= ~stat.S_IXGRP
    mode &= ~stat.S_IXOTH
    os.chmod(path, mode)


def install(src, dest):
    """Manually install a file to a particular location."""
    tty.debug("Installing %s to %s" % (src, dest))

    # Expand dest to its eventual full path if it is a directory.
    if os.path.isdir(dest):
        dest = join_path(dest, os.path.basename(src))

    shutil.copy(src, dest)
    set_install_permissions(dest)
    copy_mode(src, dest)


def install_tree(src, dest, **kwargs):
    """Manually install a directory tree to a particular location."""
    tty.debug("Installing %s to %s" % (src, dest))
    shutil.copytree(src, dest, **kwargs)

    for s, d in traverse_tree(src, dest, follow_nonexisting=False):
        set_install_permissions(d)
        copy_mode(s, d)


def is_exe(path):
    """True if path is an executable file."""
    return os.path.isfile(path) and os.access(path, os.X_OK)


def expand_user(path):
    """Find instances of '%u' in a path and replace with the current user's
       username."""
    username = getpass.getuser()
    if not username and '%u' in path:
        tty.die("Couldn't get username to complete path '%s'" % path)

    return path.replace('%u', username)


def mkdirp(*paths):
    """Creates a directory, as well as parent directories if needed."""
    for path in paths:
        if not os.path.exists(path):
            os.makedirs(path)
        elif not os.path.isdir(path):
            raise OSError(errno.EEXIST, "File already exists", path)


def force_remove(*paths):
    """Remove files without printing errors.  Like rm -f, does NOT
       remove directories."""
    for path in paths:
        try:
            os.remove(path)
        except OSError:
            pass


@contextmanager
def working_dir(dirname, **kwargs):
    if kwargs.get('create', False):
        mkdirp(dirname)

    orig_dir = os.getcwd()
    os.chdir(dirname)
    yield
    os.chdir(orig_dir)


def touch(path):
    """Creates an empty file at the specified path."""
    with open(path, 'a'):
        os.utime(path, None)


def touchp(path):
    """Like touch, but creates any parent directories needed for the file."""
    mkdirp(os.path.dirname(path))
    touch(path)


def force_symlink(src, dest):
    try:
        os.symlink(src, dest)
    except OSError:
        os.remove(dest)
        os.symlink(src, dest)


def join_path(prefix, *args):
    path = str(prefix)
    for elt in args:
        path = os.path.join(path, str(elt))
    return path


def ancestor(dir, n=1):
    """Get the nth ancestor of a directory."""
    parent = os.path.abspath(dir)
    for i in range(n):
        parent = os.path.dirname(parent)
    return parent


def can_access(file_name):
    """True if we have read/write access to the file."""
    return os.access(file_name, os.R_OK | os.W_OK)


def traverse_tree(source_root, dest_root, rel_path='', **kwargs):
    """Traverse two filesystem trees simultaneously.

    Walks the LinkTree directory in pre or post order.  Yields each
    file in the source directory with a matching path from the dest
    directory, along with whether the file is a directory.
    e.g., for this tree::

        root/
          a/
            file1
            file2
          b/
            file3

    When called on dest, this yields::

        ('root',         'dest')
        ('root/a',       'dest/a')
        ('root/a/file1', 'dest/a/file1')
        ('root/a/file2', 'dest/a/file2')
        ('root/b',       'dest/b')
        ('root/b/file3', 'dest/b/file3')

    Optional args:

    order=[pre|post] -- Whether to do pre- or post-order traversal.

    ignore=<predicate> -- Predicate indicating which files to ignore.

    follow_nonexisting -- Whether to descend into directories in
                          src that do not exit in dest. Default True.

    follow_links -- Whether to descend into symlinks in src.

    """
    follow_nonexisting = kwargs.get('follow_nonexisting', True)
    follow_links = kwargs.get('follow_link', False)

    # Yield in pre or post order?
    order  = kwargs.get('order', 'pre')
    if order not in ('pre', 'post'):
        raise ValueError("Order must be 'pre' or 'post'.")

    # List of relative paths to ignore under the src root.
    ignore = kwargs.get('ignore', lambda filename: False)

    # Don't descend into ignored directories
    if ignore(rel_path):
        return

    source_path = os.path.join(source_root, rel_path)
    dest_path   = os.path.join(dest_root, rel_path)

    # preorder yields directories before children
    if order == 'pre':
        yield (source_path, dest_path)

    for f in os.listdir(source_path):
        source_child = os.path.join(source_path, f)
        dest_child   = os.path.join(dest_path, f)
        rel_child    = os.path.join(rel_path, f)

        # Treat as a directory
        if os.path.isdir(source_child) and (
                follow_links or not os.path.islink(source_child)):

            # When follow_nonexisting isn't set, don't descend into dirs
            # in source that do not exist in dest
            if follow_nonexisting or os.path.exists(dest_child):
                tuples = traverse_tree(source_root, dest_root, rel_child, **kwargs)  # NOQA: ignore=E501
                for t in tuples:
                    yield t

        # Treat as a file.
        elif not ignore(os.path.join(rel_path, f)):
            yield (source_child, dest_child)

    if order == 'post':
        yield (source_path, dest_path)


def set_executable(path):
    st = os.stat(path)
    os.chmod(path, st.st_mode | stat.S_IEXEC)


def remove_dead_links(root):
    """
    Removes any dead link that is present in root

    Args:
        root: path where to search for dead links

    """
    for file in os.listdir(root):
        path = join_path(root, file)
        if os.path.islink(path):
            real_path = os.path.realpath(path)
            if not os.path.exists(real_path):
                os.unlink(path)


def remove_linked_tree(path):
    """
    Removes a directory and its contents.  If the directory is a
    symlink, follows the link and removes the real directory before
    removing the link.

    Args:
        path: directory to be removed

    """
    if os.path.exists(path):
        if os.path.islink(path):
            shutil.rmtree(os.path.realpath(path), True)
            os.unlink(path)
        else:
            shutil.rmtree(path, True)


def fix_darwin_install_name(path):
    """
    Fix install name of dynamic libraries on Darwin to have full path.
    There are two parts of this task:
    (i) use install_name('-id',...) to change install name of a single lib;
    (ii) use install_name('-change',...) to change the cross linking between
    libs. The function assumes that all libraries are in one folder and
    currently won't follow subfolders.

    Args:
        path: directory in which .dylib files are located

    """
    libs = glob.glob(join_path(path, "*.dylib"))
    for lib in libs:
        # fix install name first:
        subprocess.Popen(["install_name_tool", "-id", lib, lib], stdout=subprocess.PIPE).communicate()[0]  # NOQA: ignore=E501
        long_deps = subprocess.Popen(["otool", "-L", lib], stdout=subprocess.PIPE).communicate()[0].split('\n')  # NOQA: ignore=E501
        deps = [dep.partition(' ')[0][1::] for dep in long_deps[2:-1]]
        # fix all dependencies:
        for dep in deps:
            for loc in libs:
                if dep == os.path.basename(loc):
                    subprocess.Popen(["install_name_tool", "-change", dep, loc, lib], stdout=subprocess.PIPE).communicate()[0]  # NOQA: ignore=E501
                    break


def to_lib_name(library):
    """Transforms a path to the library /path/to/lib<name>.xyz into <name>
    """
    # Assume libXYZ.suffix
    return os.path.basename(library)[3:].split(".")[0]


def to_link_flags(library):
    """Transforms a path to a <library> into linking flags -L<dir> -l<name>.

    Return:
      A string of linking flags.
    """
    dir  = os.path.dirname(library)
    name = to_lib_name(library)
    res = '-L%s -l%s' % (dir, name)
    return res


def find_library_path(libname, *paths):
    """Searches for a file called <libname> in each path.

    Return:
      directory where the library was found, if found.  None otherwise.

    """
    for path in paths:
        library = join_path(path, libname)
        if os.path.exists(library):
            return path
    return None