"""Word completion for GNU readline.

The completer completes keywords, built-ins and globals in a selectable

namespace (which defaults to __main__); when completing NAME.NAME..., it

evaluates (!) the expression up to the last dot and completes its attributes.

It's very cool to do "import sys" type "sys.", hit the completion key (twice),

and see the list of names defined by the sys module!

Tip: to use the tab key as the completion key, call

    readline.parse_and_bind("tab: complete")

Notes:

- Exceptions raised by the completer function are *ignored* (and generally cause

  the completion to fail).  This is a feature -- since readline sets the tty

  device in raw (or cbreak) mode, printing a traceback wouldn't work well

  without some complicated hoopla to save, reset and restore the tty state.

- The evaluation of the NAME.NAME... form may cause arbitrary application

  defined code to be executed if an object with a __getattr__ hook is found.

  Since it is the responsibility of the application (or the user) to enable this

  feature, I consider this an acceptable risk.  More complicated expressions

  (e.g. function calls or indexing operations) are *not* evaluated.

- When the original stdin is not a tty device, GNU readline is never

  used, and this module (and the readline module) are silently inactive.

"""

import atexit

import builtins

import __main__

__all__ = ["Completer"]

class Completer:

    def __init__(self, namespace = None):

        """Create a new completer for the command line.

        Completer([namespace]) -> completer instance.

        If unspecified, the default namespace where completions are performed

        is __main__ (technically, __main__.__dict__). Namespaces should be

        given as dictionaries.

        Completer instances should be used as the completion mechanism of

        readline via the set_completer() call:

        readline.set_completer(Completer(my_namespace).complete)

        """

        if namespace and not isinstance(namespace, dict):

            raise TypeError('namespace must be a dictionary')

        # Don't bind to namespace quite yet, but flag whether the user wants a

        # specific namespace or to use __main__.__dict__. This will allow us

        # to bind to __main__.__dict__ at completion time, not now.

        if namespace is None:

            self.use_main_ns = 1

        else:

            self.use_main_ns = 0

            self.namespace = namespace

    def complete(self, text, state):

        """Return the next possible completion for 'text'.

        This is called successively with state == 0, 1, 2, ... until it

        returns None.  The completion should begin with 'text'.

        """

        if self.use_main_ns:

            self.namespace = __main__.__dict__

        if not text.strip():

            if state == 0:

                if _readline_available:

                    readline.insert_text('\t')

                    readline.redisplay()

                    return ''

                else:

                    return '\t'

            else:

                return None

        if state == 0:

            if "." in text:

                self.matches = self.attr_matches(text)

            else:

                self.matches = self.global_matches(text)

        try:

            return self.matches[state]

        except IndexError:

            return None

    def _callable_postfix(self, val, word):

        if callable(val):

            word = word + "("

        return word

    def global_matches(self, text):

        """Compute matches when text is a simple name.

        Return a list of all keywords, built-in functions and names currently

        defined in self.namespace that match.

        """

        import keyword

        matches = []

        seen = {"__builtins__"}

        n = len(text)

        for word in keyword.kwlist:

            if word[:n] == text:

                seen.add(word)

                if word in {'finally', 'try'}:

                    word = word + ':'

                elif word not in {'False', 'None', 'True',

                                  'break', 'continue', 'pass',

                                  'else'}:

                    word = word + ' '

                matches.append(word)

        for nspace in [self.namespace, builtins.__dict__]:

            for word, val in nspace.items():

                if word[:n] == text and word not in seen:

                    seen.add(word)

                    matches.append(self._callable_postfix(val, word))

        return matches

    def attr_matches(self, text):

        """Compute matches when text contains a dot.

        Assuming the text is of the form NAME.NAME....[NAME], and is

        evaluable in self.namespace, it will be evaluated and its attributes

        (as revealed by dir()) are used as possible completions.  (For class

        instances, class members are also considered.)

        WARNING: this can still invoke arbitrary C code, if an object

        with a __getattr__ hook is evaluated.

        """

        import re

        m = re.match(r"(\w+(\.\w+)*)\.(\w*)", text)

        if not m:

            return []

        expr, attr = m.group(1, 3)

        try:

            thisobject = eval(expr, self.namespace)

        except Exception:

            return []

        # get the content of the object, except __builtins__

        words = set(dir(thisobject))

        words.discard("__builtins__")

        if hasattr(thisobject, '__class__'):

            words.add('__class__')

            words.update(get_class_members(thisobject.__class__))

        matches = []

        n = len(attr)

        if attr == '':

            noprefix = '_'

        elif attr == '_':

            noprefix = '__'

        else:

            noprefix = None

        while True:

            for word in words:

                if (word[:n] == attr and

                    not (noprefix and word[:n+1] == noprefix)):

                    match = "%s.%s" % (expr, word)

                    try:

                        val = getattr(thisobject, word)

                    except Exception:

                        pass  # Include even if attribute not set

                    else:

                        match = self._callable_postfix(val, match)

                    matches.append(match)

            if matches or not noprefix:

                break

            if noprefix == '_':

                noprefix = '__'

            else:

                noprefix = None

        matches.sort()

        return matches

def get_class_members(klass):

    ret = dir(klass)

    if hasattr(klass,'__bases__'):

        for base in klass.__bases__:

            ret = ret + get_class_members(base)

    return ret

try:

    import readline

except ImportError:

    _readline_available = False

else:

    readline.set_completer(Completer().complete)

    # Release references early at shutdown (the readline module's

    # contents are quasi-immortal, and the completer function holds a

    # reference to globals).

    atexit.register(lambda: readline.set_completer(None))

    _readline_available = True