#! /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, 0o777)

if __name__ == "__main__":
    main()