#!/usr/bin/env python3
# Copyright 2013 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# This script can either source a file and dump the enironment changes done by
# it, or just simply dump the current environment as JSON into a file.

import json
import optparse
import os
import shlex
import subprocess
import sys


def main():
    parser = optparse.OptionParser()
    parser.add_option(
        '-f', '--output-json', help='File to dump the environment as JSON into.'
    )
    parser.add_option(
        '-d',
        '--dump-mode',
        action='store_true',
        help='Dump the environment to sys.stdout and exit immediately.',
    )

    parser.disable_interspersed_args()
    options, args = parser.parse_args()
    if options.dump_mode:
        if args or options.output_json:
            parser.error(
                'Cannot specify args or --output-json with --dump-mode.'
            )
        json.dump(dict(os.environ), sys.stdout)
    else:
        if not options.output_json:
            parser.error('Requires --output-json option.')

        envsetup_cmd = ' '.join(map(shlex.quote, args))
        full_cmd = [
            'bash',
            '-c',
            '. %s > /dev/null; %s -d'
            % (envsetup_cmd, os.path.abspath(__file__)),
        ]
        try:
            output = subprocess.check_output(full_cmd)
        except Exception as e:
            sys.exit('Error running %s and dumping environment.' % envsetup_cmd)

        env_diff = {}
        new_env = json.loads(output)
        for k, val in new_env.items():
            if k == '_' or (k in os.environ and os.environ[k] == val):
                continue
            env_diff[k] = val
        with open(options.output_json, 'w') as f:
            json.dump(env_diff, f)


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