#! /usr/bin/env python

# Fix Python source files to use the new equality test operator, i.e.,

#       if x = y: ...

# is changed to

#       if x == y: ...

# The script correctly tokenizes the Python program to reliably

# distinguish between assignments and equality tests.

#

# Command line arguments are files or directories to be processed.

# Directories are searched recursively for files whose name looks

# like a python module.

# Symbolic links are always ignored (except as explicit directory

# arguments).  Of course, the original file is kept as a back-up

# (with a "~" attached to its name).

# It complains about binaries (files containing null bytes)

# and about files that are ostensibly not Python files: if the first

# line starts with '#!' and does not contain the string 'python'.

#

# Changes made are reported to stdout in a diff-like format.

#

# Undoubtedly you can do this using find and sed or perl, but this is

# a nice example of Python code that recurses down a directory tree

# and uses regular expressions.  Also note several subtleties like

# preserving the file's mode and avoiding to even write a temp file

# when no changes are needed for a file.

#

# NB: by changing only the function fixline() you can turn this

# into a program for a different change to Python programs...

import sys

import re

import os

from stat import *

import string

err = sys.stderr.write

dbg = err

rep = sys.stdout.write

def main():

    bad = 0

    if not sys.argv[1:]: # No arguments

        err('usage: ' + sys.argv[0] + ' file-or-directory ...\n')

        sys.exit(2)

    for arg in sys.argv[1:]:

        if os.path.isdir(arg):

            if recursedown(arg): bad = 1

        elif os.path.islink(arg):

            err(arg + ': will not process symbolic links\n')

            bad = 1

        else:

            if fix(arg): bad = 1

    sys.exit(bad)

ispythonprog = re.compile('^[a-zA-Z0-9_]+\.py$')

def ispython(name):

    return ispythonprog.match(name) >= 0

def recursedown(dirname):

    dbg('recursedown(%r)\n' % (dirname,))

    bad = 0

    try:

        names = os.listdir(dirname)

    except os.error, msg:

        err('%s: cannot list directory: %r\n' % (dirname, msg))

        return 1

    names.sort()

    subdirs = []

    for name in names:

        if name in (os.curdir, os.pardir): continue

        fullname = os.path.join(dirname, name)

        if os.path.islink(fullname): pass

        elif os.path.isdir(fullname):

            subdirs.append(fullname)

        elif ispython(name):

            if fix(fullname): bad = 1

    for fullname in subdirs:

        if recursedown(fullname): bad = 1

    return bad

def fix(filename):

##      dbg('fix(%r)\n' % (dirname,))

    try:

        f = open(filename, 'r')

    except IOError, msg:

        err('%s: cannot open: %r\n' % (filename, msg))

        return 1

    head, tail = os.path.split(filename)

    tempname = os.path.join(head, '@' + tail)

    g = None

    # If we find a match, we rewind the file and start over but

    # now copy everything to a temp file.

    lineno = 0

    while 1:

        line = f.readline()

        if not line: break

        lineno = lineno + 1

        if g is None and '\0' in line:

            # Check for binary files

            err(filename + ': contains null bytes; not fixed\n')

            f.close()

            return 1

        if lineno == 1 and g is None and line[:2] == '#!':

            # Check for non-Python scripts

            words = string.split(line[2:])

            if words and re.search('[pP]ython', words[0]) < 0:

                msg = filename + ': ' + words[0]

                msg = msg + ' script; not fixed\n'

                err(msg)

                f.close()

                return 1

        while line[-2:] == '\\\n':

            nextline = f.readline()

            if not nextline: break

            line = line + nextline

            lineno = lineno + 1

        newline = fixline(line)

        if newline != line:

            if g is None:

                try:

                    g = open(tempname, 'w')

                except IOError, msg:

                    f.close()

                    err('%s: cannot create: %r\n' % (tempname, msg))

                    return 1

                f.seek(0)

                lineno = 0

                rep(filename + ':\n')

                continue # restart from the beginning

            rep(repr(lineno) + '\n')

            rep('< ' + line)

            rep('> ' + newline)

        if g is not None:

            g.write(newline)

    # End of file

    f.close()

    if not g: return 0 # No changes

    # Finishing touch -- move files

    # First copy the file's mode to the temp file

    try:

        statbuf = os.stat(filename)

        os.chmod(tempname, statbuf[ST_MODE] & 07777)

    except os.error, msg:

        err('%s: warning: chmod failed (%r)\n' % (tempname, msg))

    # Then make a backup of the original file as filename~

    try:

        os.rename(filename, filename + '~')

    except os.error, msg:

        err('%s: warning: backup failed (%r)\n' % (filename, msg))

    # Now move the temp file to the original file

    try:

        os.rename(tempname, filename)

    except os.error, msg:

        err('%s: rename failed (%r)\n' % (filename, msg))

        return 1

    # Return succes

    return 0

from tokenize import tokenprog

match = {'if':':', 'elif':':', 'while':':', 'return':'\n', \

         '(':')', '[':']', '{':'}', '`':'`'}

def fixline(line):

    # Quick check for easy case

    if '=' not in line: return line

    i, n = 0, len(line)

    stack = []

    while i < n:

        j = tokenprog.match(line, i)

        if j < 0:

            # A bad token; forget about the rest of this line

            print '(Syntax error:)'

            print line,

            return line

        a, b = tokenprog.regs[3] # Location of the token proper

        token = line[a:b]

        i = i+j

        if stack and token == stack[-1]:

            del stack[-1]

        elif match.has_key(token):

            stack.append(match[token])

        elif token == '=' and stack:

            line = line[:a] + '==' + line[b:]

            i, n = a + len('=='), len(line)

        elif token == '==' and not stack:

            print '(Warning: \'==\' at top level:)'

            print line,

    return line

if __name__ == "__main__":

    main()