# Copyright 2012-2015 The Meson development team

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""A library of random helper functionality."""

import sys
import stat
import time
import platform, subprocess, operator, os, shutil, re
import collections

from glob import glob

if os.path.basename(sys.executable) == 'meson.exe':
    # In Windows and using the MSI installed executable.
    meson_command = [sys.executable]
    python_command = [sys.executable, 'runpython']
else:
    meson_command = [sys.executable, os.path.join(os.path.dirname(__file__), '..', 'meson.py')]
    python_command = [sys.executable]


# Put this in objects that should not get dumped to pickle files
# by accident.
import threading
an_unpicklable_object = threading.Lock()

class MesonException(Exception):
    '''Exceptions thrown by Meson'''

class EnvironmentException(MesonException):
    '''Exceptions thrown while processing and creating the build environment'''

class FileMode:
    # The first triad is for owner permissions, the second for group permissions,
    # and the third for others (everyone else).
    # For the 1st character:
    #  'r' means can read
    #  '-' means not allowed
    # For the 2nd character:
    #  'w' means can write
    #  '-' means not allowed
    # For the 3rd character:
    #  'x' means can execute
    #  's' means can execute and setuid/setgid is set (owner/group triads only)
    #  'S' means cannot execute and setuid/setgid is set (owner/group triads only)
    #  't' means can execute and sticky bit is set ("others" triads only)
    #  'T' means cannot execute and sticky bit is set ("others" triads only)
    #  '-' means none of these are allowed
    #
    # The meanings of 'rwx' perms is not obvious for directories; see:
    # https://www.hackinglinuxexposed.com/articles/20030424.html
    #
    # For information on this notation such as setuid/setgid/sticky bits, see:
    # https://en.wikipedia.org/wiki/File_system_permissions#Symbolic_notation
    symbolic_perms_regex = re.compile('[r-][w-][xsS-]' # Owner perms
                                      '[r-][w-][xsS-]' # Group perms
                                      '[r-][w-][xtT-]') # Others perms

    def __init__(self, perms=None, owner=None, group=None):
        self.perms_s = perms
        self.perms = self.perms_s_to_bits(perms)
        self.owner = owner
        self.group = group

    def __repr__(self):
        ret = '<FileMode: {!r} owner={} group={}'
        return ret.format(self.perms_s, self.owner, self.group)

    @classmethod
    def perms_s_to_bits(cls, perms_s):
        '''
        Does the opposite of stat.filemode(), converts strings of the form
        'rwxr-xr-x' to st_mode enums which can be passed to os.chmod()
        '''
        if perms_s is None:
            # No perms specified, we will not touch the permissions
            return -1
        eg = 'rwxr-xr-x'
        if not isinstance(perms_s, str):
            msg = 'Install perms must be a string. For example, {!r}'
            raise MesonException(msg.format(eg))
        if len(perms_s) != 9 or not cls.symbolic_perms_regex.match(perms_s):
            msg = 'File perms {!r} must be exactly 9 chars. For example, {!r}'
            raise MesonException(msg.format(perms_s, eg))
        perms = 0
        # Owner perms
        if perms_s[0] == 'r':
            perms |= stat.S_IRUSR
        if perms_s[1] == 'w':
            perms |= stat.S_IWUSR
        if perms_s[2] == 'x':
            perms |= stat.S_IXUSR
        elif perms_s[2] == 'S':
            perms |= stat.S_ISUID
        elif perms_s[2] == 's':
            perms |= stat.S_IXUSR
            perms |= stat.S_ISUID
        # Group perms
        if perms_s[3] == 'r':
            perms |= stat.S_IRGRP
        if perms_s[4] == 'w':
            perms |= stat.S_IWGRP
        if perms_s[5] == 'x':
            perms |= stat.S_IXGRP
        elif perms_s[5] == 'S':
            perms |= stat.S_ISGID
        elif perms_s[5] == 's':
            perms |= stat.S_IXGRP
            perms |= stat.S_ISGID
        # Others perms
        if perms_s[6] == 'r':
            perms |= stat.S_IROTH
        if perms_s[7] == 'w':
            perms |= stat.S_IWOTH
        if perms_s[8] == 'x':
            perms |= stat.S_IXOTH
        elif perms_s[8] == 'T':
            perms |= stat.S_ISVTX
        elif perms_s[8] == 't':
            perms |= stat.S_IXOTH
            perms |= stat.S_ISVTX
        return perms

class File:
    def __init__(self, is_built, subdir, fname):
        self.is_built = is_built
        self.subdir = subdir
        self.fname = fname
        assert(isinstance(self.subdir, str))
        assert(isinstance(self.fname, str))

    def __str__(self):
        return self.relative_name()

    def __repr__(self):
        ret = '<File: {0}'
        if not self.is_built:
            ret += ' (not built)'
        ret += '>'
        return ret.format(self.relative_name())

    @staticmethod
    def from_source_file(source_root, subdir, fname):
        if not os.path.isfile(os.path.join(source_root, subdir, fname)):
            raise MesonException('File %s does not exist.' % fname)
        return File(False, subdir, fname)

    @staticmethod
    def from_built_file(subdir, fname):
        return File(True, subdir, fname)

    @staticmethod
    def from_absolute_file(fname):
        return File(False, '', fname)

    def rel_to_builddir(self, build_to_src):
        if self.is_built:
            return self.relative_name()
        else:
            return os.path.join(build_to_src, self.subdir, self.fname)

    def absolute_path(self, srcdir, builddir):
        absdir = srcdir
        if self.is_built:
            absdir = builddir
        return os.path.join(absdir, self.relative_name())

    def endswith(self, ending):
        return self.fname.endswith(ending)

    def split(self, s):
        return self.fname.split(s)

    def __eq__(self, other):
        return (self.fname, self.subdir, self.is_built) == (other.fname, other.subdir, other.is_built)

    def __hash__(self):
        return hash((self.fname, self.subdir, self.is_built))

    def relative_name(self):
        return os.path.join(self.subdir, self.fname)

def get_compiler_for_source(compilers, src):
    for comp in compilers:
        if comp.can_compile(src):
            return comp
    raise RuntimeError('No specified compiler can handle file {!s}'.format(src))

def classify_unity_sources(compilers, sources):
    compsrclist = {}
    for src in sources:
        comp = get_compiler_for_source(compilers, src)
        if comp not in compsrclist:
            compsrclist[comp] = [src]
        else:
            compsrclist[comp].append(src)
    return compsrclist

def is_osx():
    return platform.system().lower() == 'darwin'

def is_linux():
    return platform.system().lower() == 'linux'

def is_haiku():
    return platform.system().lower() == 'haiku'

def is_windows():
    platname = platform.system().lower()
    return platname == 'windows' or 'mingw' in platname

def is_cygwin():
    platname = platform.system().lower()
    return platname.startswith('cygwin')

def is_debianlike():
    return os.path.isfile('/etc/debian_version')

def for_windows(is_cross, env):
    """
    Host machine is windows?

    Note: 'host' is the machine on which compiled binaries will run
    """
    if not is_cross:
        return is_windows()
    elif env.cross_info.has_host():
        return env.cross_info.config['host_machine']['system'] == 'windows'
    return False

def for_cygwin(is_cross, env):
    """
    Host machine is cygwin?

    Note: 'host' is the machine on which compiled binaries will run
    """
    if not is_cross:
        return is_cygwin()
    elif env.cross_info.has_host():
        return env.cross_info.config['host_machine']['system'] == 'cygwin'
    return False

def for_darwin(is_cross, env):
    """
    Host machine is Darwin (iOS/OS X)?

    Note: 'host' is the machine on which compiled binaries will run
    """
    if not is_cross:
        return is_osx()
    elif env.cross_info.has_host():
        return env.cross_info.config['host_machine']['system'] == 'darwin'
    return False

def exe_exists(arglist):
    try:
        p = subprocess.Popen(arglist, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        p.communicate()
        if p.returncode == 0:
            return True
    except FileNotFoundError:
        pass
    return False

def detect_vcs(source_dir):
    vcs_systems = [
        dict(name = 'git',        cmd = 'git', repo_dir = '.git', get_rev = 'git describe --dirty=+', rev_regex = '(.*)', dep = '.git/logs/HEAD'),
        dict(name = 'mercurial',  cmd = 'hg',  repo_dir = '.hg',  get_rev = 'hg id -i',               rev_regex = '(.*)', dep = '.hg/dirstate'),
        dict(name = 'subversion', cmd = 'svn', repo_dir = '.svn', get_rev = 'svn info',               rev_regex = 'Revision: (.*)', dep = '.svn/wc.db'),
        dict(name = 'bazaar',     cmd = 'bzr', repo_dir = '.bzr', get_rev = 'bzr revno',              rev_regex = '(.*)', dep = '.bzr'),
    ]

    segs = source_dir.replace('\\', '/').split('/')
    for i in range(len(segs), -1, -1):
        curdir = '/'.join(segs[:i])
        for vcs in vcs_systems:
            if os.path.isdir(os.path.join(curdir, vcs['repo_dir'])) and shutil.which(vcs['cmd']):
                vcs['wc_dir'] = curdir
                return vcs
    return None

def grab_leading_numbers(vstr, strict=False):
    result = []
    for x in vstr.rstrip('.').split('.'):
        try:
            result.append(int(x))
        except ValueError as e:
            if strict:
                msg = 'Invalid version to compare against: {!r}; only ' \
                      'numeric digits separated by "." are allowed: ' + str(e)
                raise MesonException(msg.format(vstr))
            break
    return result

numpart = re.compile('[0-9.]+')

def version_compare(vstr1, vstr2, strict=False):
    match = numpart.match(vstr1.strip())
    if match is None:
        msg = 'Uncomparable version string {!r}.'
        raise MesonException(msg.format(vstr1))
    vstr1 = match.group(0)
    if vstr2.startswith('>='):
        cmpop = operator.ge
        vstr2 = vstr2[2:]
    elif vstr2.startswith('<='):
        cmpop = operator.le
        vstr2 = vstr2[2:]
    elif vstr2.startswith('!='):
        cmpop = operator.ne
        vstr2 = vstr2[2:]
    elif vstr2.startswith('=='):
        cmpop = operator.eq
        vstr2 = vstr2[2:]
    elif vstr2.startswith('='):
        cmpop = operator.eq
        vstr2 = vstr2[1:]
    elif vstr2.startswith('>'):
        cmpop = operator.gt
        vstr2 = vstr2[1:]
    elif vstr2.startswith('<'):
        cmpop = operator.lt
        vstr2 = vstr2[1:]
    else:
        cmpop = operator.eq
    varr1 = grab_leading_numbers(vstr1, strict)
    varr2 = grab_leading_numbers(vstr2, strict)
    return cmpop(varr1, varr2)

def version_compare_many(vstr1, conditions):
    if not isinstance(conditions, (list, tuple, frozenset)):
        conditions = [conditions]
    found = []
    not_found = []
    for req in conditions:
        if not version_compare(vstr1, req, strict=True):
            not_found.append(req)
        else:
            found.append(req)
    return not_found == [], not_found, found

def default_libdir():
    if is_debianlike():
        try:
            pc = subprocess.Popen(['dpkg-architecture', '-qDEB_HOST_MULTIARCH'],
                                  stdout=subprocess.PIPE,
                                  stderr=subprocess.DEVNULL)
            (stdo, _) = pc.communicate()
            if pc.returncode == 0:
                archpath = stdo.decode().strip()
                return 'lib/' + archpath
        except Exception:
            pass
    if os.path.isdir('/usr/lib64') and not os.path.islink('/usr/lib64'):
        return 'lib64'
    return 'lib'

def default_libexecdir():
    # There is no way to auto-detect this, so it must be set at build time
    return 'libexec'

def default_prefix():
    return 'c:/' if is_windows() else '/usr/local'

def get_library_dirs():
    if is_windows():
        return ['C:/mingw/lib'] # Fixme
    if is_osx():
        return ['/usr/lib'] # Fix me as well.
    # The following is probably Debian/Ubuntu specific.
    # /usr/local/lib is first because it contains stuff
    # installed by the sysadmin and is probably more up-to-date
    # than /usr/lib. If you feel that this search order is
    # problematic, please raise the issue on the mailing list.
    unixdirs = ['/usr/local/lib', '/usr/lib', '/lib']
    plat = subprocess.check_output(['uname', '-m']).decode().strip()
    # This is a terrible hack. I admit it and I'm really sorry.
    # I just don't know what the correct solution is.
    if plat == 'i686':
        plat = 'i386'
    if plat.startswith('arm'):
        plat = 'arm'
    unixdirs += glob('/usr/lib/' + plat + '*')
    if os.path.exists('/usr/lib64'):
        unixdirs.append('/usr/lib64')
    unixdirs += glob('/lib/' + plat + '*')
    if os.path.exists('/lib64'):
        unixdirs.append('/lib64')
    unixdirs += glob('/lib/' + plat + '*')
    return unixdirs


def do_replacement(regex, line, confdata):
    missing_variables = set()

    def variable_replace(match):
        varname = match.group(1)
        if varname in confdata:
            (var, desc) = confdata.get(varname)
            if isinstance(var, str):
                pass
            elif isinstance(var, int):
                var = str(var)
            else:
                raise RuntimeError('Tried to replace a variable with something other than a string or int.')
        else:
            missing_variables.add(varname)
            var = ''
        return var
    return re.sub(regex, variable_replace, line), missing_variables

def do_mesondefine(line, confdata):
    arr = line.split()
    if len(arr) != 2:
        raise MesonException('#mesondefine does not contain exactly two tokens: %s', line.strip())
    varname = arr[1]
    try:
        (v, desc) = confdata.get(varname)
    except KeyError:
        return '/* #undef %s */\n' % varname
    if isinstance(v, bool):
        if v:
            return '#define %s\n' % varname
        else:
            return '#undef %s\n' % varname
    elif isinstance(v, int):
        return '#define %s %d\n' % (varname, v)
    elif isinstance(v, str):
        return '#define %s %s\n' % (varname, v)
    else:
        raise MesonException('#mesondefine argument "%s" is of unknown type.' % varname)


def do_conf_file(src, dst, confdata):
    try:
        with open(src, encoding='utf-8') as f:
            data = f.readlines()
    except Exception as e:
        raise MesonException('Could not read input file %s: %s' % (src, str(e)))
    # Only allow (a-z, A-Z, 0-9, _, -) as valid characters for a define
    # Also allow escaping '@' with '\@'
    regex = re.compile(r'(?<!\\)@([-a-zA-Z0-9_]+)@')
    result = []
    missing_variables = set()
    for line in data:
        if line.startswith('#mesondefine'):
            line = do_mesondefine(line, confdata)
        else:
            line, missing = do_replacement(regex, line, confdata)
            missing_variables.update(missing)
        result.append(line)
    dst_tmp = dst + '~'
    with open(dst_tmp, 'w', encoding='utf-8') as f:
        f.writelines(result)
    shutil.copymode(src, dst_tmp)
    replace_if_different(dst, dst_tmp)
    return missing_variables

def dump_conf_header(ofilename, cdata):
    with open(ofilename, 'w', encoding='utf-8') as ofile:
        ofile.write('''/*
 * Autogenerated by the Meson build system.
 * Do not edit, your changes will be lost.
 */

#pragma once

''')
        for k in sorted(cdata.keys()):
            (v, desc) = cdata.get(k)
            if desc:
                ofile.write('/* %s */\n' % desc)
            if isinstance(v, bool):
                if v:
                    ofile.write('#define %s\n\n' % k)
                else:
                    ofile.write('#undef %s\n\n' % k)
            elif isinstance(v, (int, str)):
                ofile.write('#define %s %s\n\n' % (k, v))
            else:
                raise MesonException('Unknown data type in configuration file entry: ' + k)

def replace_if_different(dst, dst_tmp):
    # If contents are identical, don't touch the file to prevent
    # unnecessary rebuilds.
    different = True
    try:
        with open(dst, 'r') as f1, open(dst_tmp, 'r') as f2:
            if f1.read() == f2.read():
                different = False
    except FileNotFoundError:
        pass
    if different:
        os.replace(dst_tmp, dst)
    else:
        os.unlink(dst_tmp)

def listify(item, flatten=True, unholder=False):
    '''
    Returns a list with all args embedded in a list if they are not a list.
    This function preserves order.
    @flatten: Convert lists of lists to a flat list
    @unholder: Replace each item with the object it holds, if required

    Note: unholding only works recursively when flattening
    '''
    if not isinstance(item, list):
        if unholder and hasattr(item, 'held_object'):
            item = item.held_object
        return [item]
    result = []
    for i in item:
        if unholder and hasattr(i, 'held_object'):
            i = i.held_object
        if flatten and isinstance(i, list):
            result += listify(i, flatten=True, unholder=unholder)
        else:
            result.append(i)
    return result


def extract_as_list(dict_object, *keys, pop=False, **kwargs):
    '''
    Extracts all values from given dict_object and listifies them.
    '''
    result = []
    fetch = dict_object.get
    if pop:
        fetch = dict_object.pop
    # If there's only one key, we don't return a list with one element
    if len(keys) == 1:
        return listify(fetch(keys[0], []), **kwargs)
    # Return a list of values corresponding to *keys
    for key in keys:
        result.append(listify(fetch(key, []), **kwargs))
    return result


def typeslistify(item, types):
    '''
    Ensure that type(@item) is one of @types or a
    list of items all of which are of type @types
    '''
    if isinstance(item, types):
        item = [item]
    if not isinstance(item, list):
        raise MesonException('Item must be a list or one of {!r}'.format(types))
    for i in item:
        if i is not None and not isinstance(i, types):
            raise MesonException('List item must be one of {!r}'.format(types))
    return item

def stringlistify(item):
    return typeslistify(item, str)

def expand_arguments(args):
    expended_args = []
    for arg in args:
        if not arg.startswith('@'):
            expended_args.append(arg)
            continue

        args_file = arg[1:]
        try:
            with open(args_file) as f:
                extended_args = f.read().split()
            expended_args += extended_args
        except Exception as e:
            print('Error expanding command line arguments, %s not found' % args_file)
            print(e)
            return None
    return expended_args

def Popen_safe(args, write=None, stderr=subprocess.PIPE, **kwargs):
    if sys.version_info < (3, 6) or not sys.stdout.encoding:
        return Popen_safe_legacy(args, write=write, stderr=stderr, **kwargs)
    p = subprocess.Popen(args, universal_newlines=True,
                         close_fds=False,
                         stdout=subprocess.PIPE,
                         stderr=stderr, **kwargs)
    o, e = p.communicate(write)
    return p, o, e

def Popen_safe_legacy(args, write=None, stderr=subprocess.PIPE, **kwargs):
    p = subprocess.Popen(args, universal_newlines=False,
                         stdout=subprocess.PIPE,
                         stderr=stderr, **kwargs)
    if write is not None:
        write = write.encode('utf-8')
    o, e = p.communicate(write)
    if o is not None:
        if sys.stdout.encoding:
            o = o.decode(encoding=sys.stdout.encoding, errors='replace').replace('\r\n', '\n')
        else:
            o = o.decode(errors='replace').replace('\r\n', '\n')
    if e is not None:
        if sys.stderr.encoding:
            e = e.decode(encoding=sys.stderr.encoding, errors='replace').replace('\r\n', '\n')
        else:
            e = e.decode(errors='replace').replace('\r\n', '\n')
    return p, o, e

def commonpath(paths):
    '''
    For use on Python 3.4 where os.path.commonpath is not available.
    We currently use it everywhere so this receives enough testing.
    '''
    # XXX: Replace me with os.path.commonpath when we start requiring Python 3.5
    import pathlib
    if not paths:
        raise ValueError('arg is an empty sequence')
    common = pathlib.PurePath(paths[0])
    for path in paths[1:]:
        new = []
        path = pathlib.PurePath(path)
        for c, p in zip(common.parts, path.parts):
            if c != p:
                break
            new.append(c)
        # Don't convert '' into '.'
        if not new:
            common = ''
            break
        new = os.path.join(*new)
        common = pathlib.PurePath(new)
    return str(common)

def iter_regexin_iter(regexiter, initer):
    '''
    Takes each regular expression in @regexiter and tries to search for it in
    every item in @initer. If there is a match, returns that match.
    Else returns False.
    '''
    for regex in regexiter:
        for ii in initer:
            if not isinstance(ii, str):
                continue
            match = re.search(regex, ii)
            if match:
                return match.group()
    return False

def _substitute_values_check_errors(command, values):
    # Error checking
    inregex = ('@INPUT([0-9]+)?@', '@PLAINNAME@', '@BASENAME@')
    outregex = ('@OUTPUT([0-9]+)?@', '@OUTDIR@')
    if '@INPUT@' not in values:
        # Error out if any input-derived templates are present in the command
        match = iter_regexin_iter(inregex, command)
        if match:
            m = 'Command cannot have {!r}, since no input files were specified'
            raise MesonException(m.format(match))
    else:
        if len(values['@INPUT@']) > 1:
            # Error out if @PLAINNAME@ or @BASENAME@ is present in the command
            match = iter_regexin_iter(inregex[1:], command)
            if match:
                raise MesonException('Command cannot have {!r} when there is '
                                     'more than one input file'.format(match))
        # Error out if an invalid @INPUTnn@ template was specified
        for each in command:
            if not isinstance(each, str):
                continue
            match = re.search(inregex[0], each)
            if match and match.group() not in values:
                m = 'Command cannot have {!r} since there are only {!r} inputs'
                raise MesonException(m.format(match.group(), len(values['@INPUT@'])))
    if '@OUTPUT@' not in values:
        # Error out if any output-derived templates are present in the command
        match = iter_regexin_iter(outregex, command)
        if match:
            m = 'Command cannot have {!r} since there are no outputs'
            raise MesonException(m.format(match))
    else:
        # Error out if an invalid @OUTPUTnn@ template was specified
        for each in command:
            if not isinstance(each, str):
                continue
            match = re.search(outregex[0], each)
            if match and match.group() not in values:
                m = 'Command cannot have {!r} since there are only {!r} outputs'
                raise MesonException(m.format(match.group(), len(values['@OUTPUT@'])))

def substitute_values(command, values):
    '''
    Substitute the template strings in the @values dict into the list of
    strings @command and return a new list. For a full list of the templates,
    see get_filenames_templates_dict()

    If multiple inputs/outputs are given in the @values dictionary, we
    substitute @INPUT@ and @OUTPUT@ only if they are the entire string, not
    just a part of it, and in that case we substitute *all* of them.
    '''
    # Error checking
    _substitute_values_check_errors(command, values)
    # Substitution
    outcmd = []
    for vv in command:
        if not isinstance(vv, str):
            outcmd.append(vv)
        elif '@INPUT@' in vv:
            inputs = values['@INPUT@']
            if vv == '@INPUT@':
                outcmd += inputs
            elif len(inputs) == 1:
                outcmd.append(vv.replace('@INPUT@', inputs[0]))
            else:
                raise MesonException("Command has '@INPUT@' as part of a "
                                     "string and more than one input file")
        elif '@OUTPUT@' in vv:
            outputs = values['@OUTPUT@']
            if vv == '@OUTPUT@':
                outcmd += outputs
            elif len(outputs) == 1:
                outcmd.append(vv.replace('@OUTPUT@', outputs[0]))
            else:
                raise MesonException("Command has '@OUTPUT@' as part of a "
                                     "string and more than one output file")
        # Append values that are exactly a template string.
        # This is faster than a string replace.
        elif vv in values:
            outcmd.append(values[vv])
        # Substitute everything else with replacement
        else:
            for key, value in values.items():
                if key in ('@INPUT@', '@OUTPUT@'):
                    # Already done above
                    continue
                vv = vv.replace(key, value)
            outcmd.append(vv)
    return outcmd

def get_filenames_templates_dict(inputs, outputs):
    '''
    Create a dictionary with template strings as keys and values as values for
    the following templates:

    @INPUT@  - the full path to one or more input files, from @inputs
    @OUTPUT@ - the full path to one or more output files, from @outputs
    @OUTDIR@ - the full path to the directory containing the output files

    If there is only one input file, the following keys are also created:

    @PLAINNAME@ - the filename of the input file
    @BASENAME@ - the filename of the input file with the extension removed

    If there is more than one input file, the following keys are also created:

    @INPUT0@, @INPUT1@, ... one for each input file

    If there is more than one output file, the following keys are also created:

    @OUTPUT0@, @OUTPUT1@, ... one for each output file
    '''
    values = {}
    # Gather values derived from the input
    if inputs:
        # We want to substitute all the inputs.
        values['@INPUT@'] = inputs
        for (ii, vv) in enumerate(inputs):
            # Write out @INPUT0@, @INPUT1@, ...
            values['@INPUT{}@'.format(ii)] = vv
        if len(inputs) == 1:
            # Just one value, substitute @PLAINNAME@ and @BASENAME@
            values['@PLAINNAME@'] = plain = os.path.split(inputs[0])[1]
            values['@BASENAME@'] = os.path.splitext(plain)[0]
    if outputs:
        # Gather values derived from the outputs, similar to above.
        values['@OUTPUT@'] = outputs
        for (ii, vv) in enumerate(outputs):
            values['@OUTPUT{}@'.format(ii)] = vv
        # Outdir should be the same for all outputs
        values['@OUTDIR@'] = os.path.split(outputs[0])[0]
        # Many external programs fail on empty arguments.
        if values['@OUTDIR@'] == '':
            values['@OUTDIR@'] = '.'
    return values


def windows_proof_rmtree(f):
    # On Windows if anyone is holding a file open you can't
    # delete it. As an example an anti virus scanner might
    # be scanning files you are trying to delete. The only
    # way to fix this is to try again and again.
    delays = [0.1, 0.1, 0.2, 0.2, 0.2, 0.5, 0.5, 1, 1, 1, 1, 2]
    for d in delays:
        try:
            shutil.rmtree(f)
            return
        except (OSError, PermissionError):
            time.sleep(d)
    # Try one last time and throw if it fails.
    shutil.rmtree(f)

class OrderedSet(collections.MutableSet):
    """A set that preserves the order in which items are added, by first
    insertion.
    """
    def __init__(self, iterable=None):
        self.__container = collections.OrderedDict()
        if iterable:
            self.update(iterable)

    def __contains__(self, value):
        return value in self.__container

    def __iter__(self):
        return iter(self.__container.keys())

    def __len__(self):
        return len(self.__container)

    def __repr__(self):
        # Don't print 'OrderedSet("")' for an empty set.
        if self.__container:
            return 'OrderedSet("{}")'.format(
                '", "'.join(repr(e) for e in self.__container.keys()))
        return 'OrderedSet()'

    def add(self, value):
        self.__container[value] = None

    def discard(self, value):
        if value in self.__container:
            del self.__container[value]

    def update(self, iterable):
        for item in iterable:
            self.__container[item] = None

    def difference(self, set_):
        return type(self)(e for e in self if e not in set_)