#!/usr/bin/python

import sys
import json
import re

from optparse import OptionParser

parser = OptionParser()
parser.add_option("-i", "--infile", dest="infile",
                  help="read JSON from here (stdin if omitted)", metavar="FILE")
parser.add_option("-o", "--outfile", dest="outfile",
                  help="write JSON to here (stdout if omitted)", metavar="FILE")
parser.add_option("-p", "--path", dest="json_path",
                  help="JSON path to read", metavar="path.to.data")
parser.add_option("-v", "--value", dest="json_value",
                  help="Value to write to the JSON path", metavar="value")

(options, args) = parser.parse_args()

if options.infile is None:
    data = json.load(sys.stdin)
else:
    with open(options.infile) as infile:
        data = json.load(infile)

ref = data
if options.json_value is None:
    # READ mode
    if options.json_path is not None:
        for token in re.split('\.', options.json_path):
            try:
                ref = ref[token]
            except KeyError:
                # JSON path does not exist, we treat that as "empty"
                ref = None
                break
    data = ref

else:
    # WRITE mode
    if options.json_path is not None:
        token_path = re.split('\.', options.json_path)
        if len(token_path) == 0:
            data = options.json_value
        else:
            for token in token_path[0:-1]:
                try:
                    ref = ref[token]
                except KeyError:
                    # JSON path does not exist, create it
                    ref[token] = {}
                    ref = ref[token]
            ref[token_path[-1]] = options.json_value
    else:
        data = options.json_value

if ref is not None:
    if options.outfile is None:
        print json.dumps(data, sys.stdout, indent=2)
    else:
        with open(options.outfile, 'w') as outfile:
            outfile.write(json.dumps(data, indent=2))