#!/usr/bin/env python
"""
shell.py - Python Shell Commands
Author: Sean B. Palmer, inamidst.com
"""

from subprocess import Popen, PIPE

def chomp(line): 
   if line.endswith('\n'): 
      return line[:-1]

class Process(object): 
   def __init__(self, args): 
      self.args = args
      self.input = None

   def __iter__(self): 
      process = self
      pipeline = []

      while True:
         pipeline = [process.args] + pipeline
         if process.input is None: break
         process = process.input

      first = pipeline[0]
      procs = [Popen(first, stdout=PIPE)]
      for args in pipeline[1:]: 
         procs.append(Popen(args, stdin=procs[-1].stdout, stdout=PIPE))

      stdout = procs[-1].stdout
      return iter(chomp(line) for line in stdout)

   def __or__(self, obj): 
      if not isinstance(obj, Process): 
         raise TypeError("Expected Process, got %r" % obj)
      obj.input = self
      return obj

def out(*args): 
   return Process(args)

def do(seq): 
   for item in seq: 
      pass

def run(*args): 
   do(out(*args))

def test(): 
   output = out("cat", "shell.py") | out("grep", ".") | out("wc", "-w")
   for line in output: 
      print line
   print 

   cp = lambda *args: out(*["cp"] + list(args))
   ls = lambda *args: out(*["ls"] + list(args))
   rm = lambda *args: out(*["rm"] + list(args))

   do(cp("shell.py", "test.tmp"))
   for line in ls("-al", "test.tmp"): 
      print line
   do(rm("test.tmp"))

if __name__ == '__main__': 
   test()