#! /usr/bin/env python

# A rather specialized script to make sure that a symbolic link named

# RCS exists pointing to a real RCS directory in a parallel tree

# referenced as RCStree in an ancestor directory.

# (I use this because I like my RCS files to reside on a physically

# different machine).

import os

def main():

    rcstree = 'RCStree'

    rcs = 'RCS'

    if os.path.islink(rcs):

        print '%r is a symlink to %r' % (rcs, os.readlink(rcs))

        return

    if os.path.isdir(rcs):

        print '%r is an ordinary directory' % (rcs,)

        return

    if os.path.exists(rcs):

        print '%r is a file?!?!' % (rcs,)

        return

    #

    p = os.getcwd()

    up = ''

    down = ''

    # Invariants:

    # (1) join(p, down) is the current directory

    # (2) up is the same directory as p

    # Ergo:

    # (3) join(up, down) is the current directory

    #print 'p =', repr(p)

    while not os.path.isdir(os.path.join(p, rcstree)):

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

        #print 'head = %r; tail = %r' % (head, tail)

        if not tail:

            print 'Sorry, no ancestor dir contains %r' % (rcstree,)

            return

        p = head

        up = os.path.join(os.pardir, up)

        down = os.path.join(tail, down)

        #print 'p = %r; up = %r; down = %r' % (p, up, down)

    there = os.path.join(up, rcstree)

    there = os.path.join(there, down)

    there = os.path.join(there, rcs)

    if os.path.isdir(there):

        print '%r already exists' % (there, )

    else:

        print 'making %r' % (there,)

        makedirs(there)

    print 'making symlink %r -> %r' % (rcs, there)

    os.symlink(there, rcs)

def makedirs(p):

    if not os.path.isdir(p):

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

        makedirs(head)

        os.mkdir(p, 0777)

if __name__ == "__main__":

    main()