# Small python script to replace full path in prompt with symlinks where
# appropriate. Set your shell prompt to this script's output with
######################################################################
# export PROMPT_COMMAND='PS1="$(python /path-to/symlinkifypath.py)"' #
######################################################################
# in your .bashrc.

# Set 'symLinksDir' and 'tilde' as per your needs below.
# Please make sure all your symlinks are the complete path - no symlinks
# inside another.. This script works for symlinks that start from the root
# directory, it replaces the set of characters starting from the beginning of
# the complete path with your symlink name.

import os
from os.path import isfile,islink,join
from commands import getoutput
from socket import gethostname
import operator

# Set this to where you store symbolic links
symLinksDir = '/home/jmazz'
# May not wish to use '~' if your symLinksDir is not your home directory
tilde = '~'

# Get hostname, username, cwd, pwd
hostname = gethostname()
username = os.environ['USER']
pwd = os.getcwd()
homedir = os.path.expanduser('~')
pwd = pwd.replace(homedir, '~', 1)

# Build list of directories in symLinksDir
dirs = []
for (dirpath, dirnames, filenames) in os.walk(symLinksDir):
    dirs.extend(dirnames)
    break

# Build dict of symlinks. {key,value} pair as
# {linkName, linkPath}
symLinks = {}
for potentialLink in dirs:
    if islink(join(symLinksDir,potentialLink)):
        symLink = potentialLink
        path = join(symLinksDir,potentialLink)
        symLinks.update({symLink:os.readlink(path)})

# Build dict storing lengths of linkPath for each linkName
# {linkName, len(linkPath)}
symLinksLens = {}
for key in symLinks.keys():
    symLinksLens.update({key:len(symLinks[key])})

# Sort symLinksLens by values; gives list of tuples of the form
# (linkName, len(linkPath))
sorted_symLinksLens = sorted(symLinksLens.items(), key=operator.itemgetter(1))
# Highest to lowest
sorted_symLinksLens.reverse()

# List of linkNames, in order from highest to lowest string length of linkPath
linkNames = []
for link in sorted_symLinksLens:
    linkNames.append(link[0])

# Check if full path contains any of the symLinks, and alter pwd accordingly
for linkName in linkNames:
    sL = symLinks[linkName]
    if sL == pwd[:len(sL)]:
        pwd = '%s/%s%s' % (tilde,linkName,pwd[len(sL):])
        break

# Print string for the shell prompt
print '%s@%s:%s$ ' % (username, hostname, pwd)