"""Utilities needed to emulate Python's interactive interpreter.

"""

# Inspired by similar code by Jeff Epler and Fredrik Lundh.

import sys

import traceback

from codeop import CommandCompiler, compile_command

__all__ = ["InteractiveInterpreter", "InteractiveConsole", "interact",

           "compile_command"]

def softspace(file, newvalue):

    oldvalue = 0

    try:

        oldvalue = file.softspace

    except AttributeError:

        pass

    try:

        file.softspace = newvalue

    except (AttributeError, TypeError):

        # "attribute-less object" or "read-only attributes"

        pass

    return oldvalue

class InteractiveInterpreter:

    """Base class for InteractiveConsole.

    This class deals with parsing and interpreter state (the user's

    namespace); it doesn't deal with input buffering or prompting or

    input file naming (the filename is always passed in explicitly).

    """

    def __init__(self, locals=None):

        """Constructor.

        The optional 'locals' argument specifies the dictionary in

        which code will be executed; it defaults to a newly created

        dictionary with key "__name__" set to "__console__" and key

        "__doc__" set to None.

        """

        if locals is None:

            locals = {"__name__": "__console__", "__doc__": None}

        self.locals = locals

        self.compile = CommandCompiler()

    def runsource(self, source, filename="<input>", symbol="single"):

        """Compile and run some source in the interpreter.

        Arguments are as for compile_command().

        One several things can happen:

        1) The input is incorrect; compile_command() raised an

        exception (SyntaxError or OverflowError).  A syntax traceback

        will be printed by calling the showsyntaxerror() method.

        2) The input is incomplete, and more input is required;

        compile_command() returned None.  Nothing happens.

        3) The input is complete; compile_command() returned a code

        object.  The code is executed by calling self.runcode() (which

        also handles run-time exceptions, except for SystemExit).

        The return value is True in case 2, False in the other cases (unless

        an exception is raised).  The return value can be used to

        decide whether to use sys.ps1 or sys.ps2 to prompt the next

        line.

        """

        try:

            code = self.compile(source, filename, symbol)

        except (OverflowError, SyntaxError, ValueError):

            # Case 1

            self.showsyntaxerror(filename)

            return False

        if code is None:

            # Case 2

            return True

        # Case 3

        self.runcode(code)

        return False

    def runcode(self, code):

        """Execute a code object.

        When an exception occurs, self.showtraceback() is called to

        display a traceback.  All exceptions are caught except

        SystemExit, which is reraised.

        A note about KeyboardInterrupt: this exception may occur

        elsewhere in this code, and may not always be caught.  The

        caller should be prepared to deal with it.

        """

        try:

            exec code in self.locals

        except SystemExit:

            raise

        except:

            self.showtraceback()

        else:

            if softspace(sys.stdout, 0):

                print

    def showsyntaxerror(self, filename=None):

        """Display the syntax error that just occurred.

        This doesn't display a stack trace because there isn't one.

        If a filename is given, it is stuffed in the exception instead

        of what was there before (because Python's parser always uses

        "<string>" when reading from a string).

        The output is written by self.write(), below.

        """

        type, value, sys.last_traceback = sys.exc_info()

        sys.last_type = type

        sys.last_value = value

        if filename and type is SyntaxError:

            # Work hard to stuff the correct filename in the exception

            try:

                msg, (dummy_filename, lineno, offset, line) = value

            except:

                # Not the format we expect; leave it alone

                pass

            else:

                # Stuff in the right filename

                value = SyntaxError(msg, (filename, lineno, offset, line))

                sys.last_value = value

        list = traceback.format_exception_only(type, value)

        map(self.write, list)

    def showtraceback(self):

        """Display the exception that just occurred.

        We remove the first stack item because it is our own code.

        The output is written by self.write(), below.

        """

        try:

            type, value, tb = sys.exc_info()

            sys.last_type = type

            sys.last_value = value

            sys.last_traceback = tb

            tblist = traceback.extract_tb(tb)

            del tblist[:1]

            list = traceback.format_list(tblist)

            if list:

                list.insert(0, "Traceback (most recent call last):\n")

            list[len(list):] = traceback.format_exception_only(type, value)

        finally:

            tblist = tb = None

        map(self.write, list)

    def write(self, data):

        """Write a string.

        The base implementation writes to sys.stderr; a subclass may

        replace this with a different implementation.

        """

        sys.stderr.write(data)

class InteractiveConsole(InteractiveInterpreter):

    """Closely emulate the behavior of the interactive Python interpreter.

    This class builds on InteractiveInterpreter and adds prompting

    using the familiar sys.ps1 and sys.ps2, and input buffering.

    """

    def __init__(self, locals=None, filename="<console>"):

        """Constructor.

        The optional locals argument will be passed to the

        InteractiveInterpreter base class.

        The optional filename argument should specify the (file)name

        of the input stream; it will show up in tracebacks.

        """

        InteractiveInterpreter.__init__(self, locals)

        self.filename = filename

        self.resetbuffer()

    def resetbuffer(self):

        """Reset the input buffer."""

        self.buffer = []

    def interact(self, banner=None):

        """Closely emulate the interactive Python console.

        The optional banner argument specify the banner to print

        before the first interaction; by default it prints a banner

        similar to the one printed by the real Python interpreter,

        followed by the current class name in parentheses (so as not

        to confuse this with the real interpreter -- since it's so

        close!).

        """

        try:

            sys.ps1

        except AttributeError:

            sys.ps1 = ">>> "

        try:

            sys.ps2

        except AttributeError:

            sys.ps2 = "... "

        cprt = 'Type "help", "copyright", "credits" or "license" for more information.'

        if banner is None:

            self.write("Python %s on %s\n%s\n(%s)\n" %

                       (sys.version, sys.platform, cprt,

                        self.__class__.__name__))

        else:

            self.write("%s\n" % str(banner))

        more = 0

        while 1:

            try:

                if more:

                    prompt = sys.ps2

                else:

                    prompt = sys.ps1

                try:

                    line = self.raw_input(prompt)

                    # Can be None if sys.stdin was redefined

                    encoding = getattr(sys.stdin, "encoding", None)

                    if encoding and not isinstance(line, unicode):

                        line = line.decode(encoding)

                except EOFError:

                    self.write("\n")

                    break

                else:

                    more = self.push(line)

            except KeyboardInterrupt:

                self.write("\nKeyboardInterrupt\n")

                self.resetbuffer()

                more = 0

    def push(self, line):

        """Push a line to the interpreter.

        The line should not have a trailing newline; it may have

        internal newlines.  The line is appended to a buffer and the

        interpreter's runsource() method is called with the

        concatenated contents of the buffer as source.  If this

        indicates that the command was executed or invalid, the buffer

        is reset; otherwise, the command is incomplete, and the buffer

        is left as it was after the line was appended.  The return

        value is 1 if more input is required, 0 if the line was dealt

        with in some way (this is the same as runsource()).

        """

        self.buffer.append(line)

        source = "\n".join(self.buffer)

        more = self.runsource(source, self.filename)

        if not more:

            self.resetbuffer()

        return more

    def raw_input(self, prompt=""):

        """Write a prompt and read a line.

        The returned line does not include the trailing newline.

        When the user enters the EOF key sequence, EOFError is raised.

        The base implementation uses the built-in function

        raw_input(); a subclass may replace this with a different

        implementation.

        """

        return raw_input(prompt)

def interact(banner=None, readfunc=None, local=None):

    """Closely emulate the interactive Python interpreter.

    This is a backwards compatible interface to the InteractiveConsole

    class.  When readfunc is not specified, it attempts to import the

    readline module to enable GNU readline if it is available.

    Arguments (all optional, all default to None):

    banner -- passed to InteractiveConsole.interact()

    readfunc -- if not None, replaces InteractiveConsole.raw_input()

    local -- passed to InteractiveInterpreter.__init__()

    """

    console = InteractiveConsole(local)

    if readfunc is not None:

        console.raw_input = readfunc

    else:

        try:

            import readline

        except ImportError:

            pass

    console.interact(banner)

if __name__ == '__main__':

    import pdb

    pdb.run("interact()\n")