#! /usr/bin/env python3

# linktree
#
# Make a copy of a directory tree with symbolic links to all files in the
# original tree.
# All symbolic links go to a special symbolic link at the top, so you
# can easily fix things if the original source tree moves.
# See also "mkreal".
#
# usage: mklinks oldtree newtree

import sys, os

LINK = '.LINK' # Name of special symlink at the top.

debug = 0

def main():
 if not 3 <= len(sys.argv) <= 4:
 print('usage:', sys.argv[0], 'oldtree newtree [linkto]')
 return 2
 oldtree, newtree = sys.argv[1], sys.argv[2]
 if len(sys.argv) > 3:
 link = sys.argv[3]
 link_may_fail = 1
 else:
 link = LINK
 link_may_fail = 0
 if not os.path.isdir(oldtree):
 print(oldtree + ': not a directory')
 return 1
 try:
 os.mkdir(newtree, 0o777)
 except OSError as msg:
 print(newtree + ': cannot mkdir:', msg)
 return 1
 linkname = os.path.join(newtree, link)
 try:
 os.symlink(os.path.join(os.pardir, oldtree), linkname)
 except OSError as msg:
 if not link_may_fail:
 print(linkname + ': cannot symlink:', msg)
 return 1
 else:
 print(linkname + ': warning: cannot symlink:', msg)
 linknames(oldtree, newtree, link)
 return 0

def linknames(old, new, link):
 if debug: print('linknames', (old, new, link))
 try:
 names = os.listdir(old)
 except OSError as msg:
 print(old + ': warning: cannot listdir:', msg)
 return
 for name in names:
 if name not in (os.curdir, os.pardir):
 oldname = os.path.join(old, name)
 linkname = os.path.join(link, name)
 newname = os.path.join(new, name)
 if debug > 1: print(oldname, newname, linkname)
 if os.path.isdir(oldname) and \
 not os.path.islink(oldname):
 try:
 os.mkdir(newname, 0o777)
 ok = 1
 except:
 print(newname + \
 ': warning: cannot mkdir:', msg)
 ok = 0
 if ok:
 linkname = os.path.join(os.pardir,
 linkname)
 linknames(oldname, newname, linkname)
 else:
 os.symlink(linkname, newname)

if __name__ == '__main__':
 sys.exit(main())