"""Command-line options parser.
With the help of an options spec string, easily parse command-line options.

An options spec is made up of two parts, separated by a line with two dashes.
The first part is the synopsis of the command and the second one specifies
options, one per line.

Each non-empty line in the synopsis gives a set of options that can be used
together.

Option flags must be at the begining of the line and multiple flags are
separated by commas. Usually, options have a short, one character flag, and a
longer one, but the short one can be omitted.

Long option flags are used as the option's key for the OptDict produced when
parsing options.

When the flag definition is ended with an equal sign, the option takes one
string as an argument. Otherwise, the option does not take an argument and
corresponds to a boolean flag that is true when the option is given on the
command line.

The option's description is found at the right of its flags definition, after
one or more spaces. The description ends at the end of the line. If the
description contains text enclosed in square brackets, the enclosed text will
be used as the option's default value.

Options can be put in different groups. Options in the same group must be on
consecutive lines. Groups are formed by inserting a line that begins with a
space. The text on that line will be output after an empty line.
"""
import sys, os, textwrap, getopt, re, struct

class OptDict:
    """Dictionary that exposes keys as attributes.

    Keys can bet set or accessed with a "no-" or "no_" prefix to negate the
    value.
    """
    def __init__(self):
        self._opts = {}

    def __setitem__(self, k, v):
        if k.startswith('no-') or k.startswith('no_'):
            k = k[3:]
            v = not v
        self._opts[k] = v

    def __getitem__(self, k):
        if k.startswith('no-') or k.startswith('no_'):
            return not self._opts[k[3:]]
        return self._opts[k]

    def __getattr__(self, k):
        return self[k]


def _default_onabort(msg):
    sys.exit(97)


def _intify(v):
    try:
        vv = int(v or '')
        if str(vv) == v:
            return vv
    except ValueError:
        pass
    return v


def _atoi(v):
    try:
        return int(v or 0)
    except ValueError:
        return 0


def _remove_negative_kv(k, v):
    if k.startswith('no-') or k.startswith('no_'):
        return k[3:], not v
    return k,v

def _remove_negative_k(k):
    return _remove_negative_kv(k, None)[0]


def _tty_width():
    s = struct.pack("HHHH", 0, 0, 0, 0)
    try:
        import fcntl, termios
        s = fcntl.ioctl(sys.stderr.fileno(), termios.TIOCGWINSZ, s)
    except (IOError, ImportError):
        return _atoi(os.environ.get('WIDTH')) or 70
    (ysize,xsize,ypix,xpix) = struct.unpack('HHHH', s)
    return xsize or 70


class Options:
    """Option parser.
    When constructed, a string called an option spec must be given. It
    specifies the synopsis and option flags and their description.  For more
    information about option specs, see the docstring at the top of this file.

    Two optional arguments specify an alternative parsing function and an
    alternative behaviour on abort (after having output the usage string).

    By default, the parser function is getopt.gnu_getopt, and the abort
    behaviour is to exit the program.
    """
    def __init__(self, optspec, optfunc=getopt.gnu_getopt,
                 onabort=_default_onabort):
        self.optspec = optspec
        self._onabort = onabort
        self.optfunc = optfunc
        self._aliases = {}
        self._shortopts = 'h?'
        self._longopts = ['help', 'usage']
        self._hasparms = {}
        self._defaults = {}
        self._usagestr = self._gen_usage()

    def _gen_usage(self):
        out = []
        lines = self.optspec.strip().split('\n')
        lines.reverse()
        first_syn = True
        while lines:
            l = lines.pop()
            if l == '--': break
            out.append('%s: %s\n' % (first_syn and 'usage' or '   or', l))
            first_syn = False
        out.append('\n')
        last_was_option = False
        while lines:
            l = lines.pop()
            if l.startswith(' '):
                out.append('%s%s\n' % (last_was_option and '\n' or '',
                                       l.lstrip()))
                last_was_option = False
            elif l:
                (flags, extra) = l.split(' ', 1)
                extra = extra.strip()
                if flags.endswith('='):
                    flags = flags[:-1]
                    has_parm = 1
                else:
                    has_parm = 0
                g = re.search(r'\[([^\]]*)\]$', extra)
                if g:
                    defval = g.group(1)
                else:
                    defval = None
                flagl = flags.split(',')
                flagl_nice = []
                for _f in flagl:
                    f,dvi = _remove_negative_kv(_f, _intify(defval))
                    self._aliases[f] = _remove_negative_k(flagl[0])
                    self._hasparms[f] = has_parm
                    self._defaults[f] = dvi
                    if f == '#':
                        self._shortopts += '0123456789'
                        flagl_nice.append('-#')
                    elif len(f) == 1:
                        self._shortopts += f + (has_parm and ':' or '')
                        flagl_nice.append('-' + f)
                    else:
                        f_nice = re.sub(r'\W', '_', f)
                        self._aliases[f_nice] = _remove_negative_k(flagl[0])
                        self._longopts.append(f + (has_parm and '=' or ''))
                        self._longopts.append('no-' + f)
                        flagl_nice.append('--' + _f)
                flags_nice = ', '.join(flagl_nice)
                if has_parm:
                    flags_nice += ' ...'
                prefix = '    %-20s  ' % flags_nice
                argtext = '\n'.join(textwrap.wrap(extra, width=_tty_width(),
                                                initial_indent=prefix,
                                                subsequent_indent=' '*28))
                out.append(argtext + '\n')
                last_was_option = True
            else:
                out.append('\n')
                last_was_option = False
        return ''.join(out).rstrip() + '\n'

    def usage(self, msg=""):
        """Print usage string to stderr and abort."""
        sys.stderr.write(self._usagestr)
        if msg:
            sys.stderr.write(msg)
        e = self._onabort and self._onabort(msg) or None
        if e:
            raise e

    def fatal(self, msg):
        """Print an error message to stderr and abort with usage string."""
        msg = '\nerror: %s\n' % msg
        return self.usage(msg)

    def parse(self, args):
        """Parse a list of arguments and return (options, flags, extra).

        In the returned tuple, "options" is an OptDict with known options,
        "flags" is a list of option flags that were used on the command-line,
        and "extra" is a list of positional arguments.
        """
        try:
            (flags,extra) = self.optfunc(args, self._shortopts, self._longopts)
        except getopt.GetoptError, e:
            self.fatal(e)

        opt = OptDict()

        for k,v in self._defaults.iteritems():
            k = self._aliases[k]
            opt[k] = v

        for (k,v) in flags:
            k = k.lstrip('-')
            if k in ('h', '?', 'help', 'usage'):
                self.usage()
            if k.startswith('no-'):
                k = self._aliases[k[3:]]
                v = 0
            elif (self._aliases.get('#') and
                  k in ('0','1','2','3','4','5','6','7','8','9')):
                v = int(k)  # guaranteed to be exactly one digit
                k = self._aliases['#']
                opt['#'] = v
            else:
                k = self._aliases[k]
                if not self._hasparms[k]:
                    assert(v == '')
                    v = (opt._opts.get(k) or 0) + 1
                else:
                    v = _intify(v)
            opt[k] = v
        for (f1,f2) in self._aliases.iteritems():
            opt[f1] = opt._opts.get(f2)
        return (opt,flags,extra)
