#!/bin/bash

### Imports ###################################################################

source ScriptFunctions
Import OptionParser

### Options ###################################################################

helpOnNoArguments=yes
scriptNotes="$scriptName processes a file replacing instances of variables marked
with special indicators ('@%', '%@' by default) with the contents of equivalent
environment variables."
Add_Option_Entry "o" "open" "Opening mark." "@%"
Add_Option_Entry "c" "close" "Closing mark." "%@"
Add_Option_Entry "i" "identifier" "Add a prefix identifier in the form of '<entry>_' to the opening markup."
Parse_Options "$@"

### Operation #################################################################

open=`Entry "open"`
close=`Entry "close"`
if Is_Entry "identifier"
then
   open="${open}`Entry identifier`_"
fi

cat "$(Arg 1)" | python -c '
import os,sys,string

op=sys.argv[1]
cl=sys.argv[2]
for line in sys.stdin.readlines():
   while 1:
      op_index=line.find(op)
      if op_index == -1:
         break
      cl_index=line.find(cl)
      if cl_index == -1:
         break
      var = line[op_index + len(op):cl_index]
      try:
         val = os.environ[var]
      except:
         val = ""
      line = line.replace(op + var + cl, val)
   print line,
' "$open" "$close"