"""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"]

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, self.locals)
 except SystemExit:
 raise
 except:
 self.showtraceback()

 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, tb = sys.exc_info()
 sys.last_type = type
 sys.last_value = value
 sys.last_traceback = tb
 if filename and type is SyntaxError:
 # Work hard to stuff the correct filename in the exception
 try:
 msg, (dummy_filename, lineno, offset, line) = value.args
 except ValueError:
 # 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
 if sys.excepthook is sys.__excepthook__:
 lines = traceback.format_exception_only(type, value)
 self.write(''.join(lines))
 else:
 # If someone has set sys.excepthook, we let that take precedence
 # over self.write
 sys.excepthook(type, value, tb)

 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]
 lines = traceback.format_list(tblist)
 if lines:
 lines.insert(0, "Traceback (most recent call last):\n")
 lines.extend(traceback.format_exception_only(type, value))
 finally:
 tblist = tb = None
 if sys.excepthook is sys.__excepthook__:
 self.write(''.join(lines))
 else:
 # If someone has set sys.excepthook, we let that take precedence
 # over self.write
 sys.excepthook(type, value, tb)

 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 specifies 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__))
 elif banner:
 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)
 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
 input(); a subclass may replace this with a different
 implementation.

 """
 return 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__":
 interact()