crap helper environment POC

#!/usr/bin/env python
"""
Environment helper for cram.
Proof of concept, would be better implemented inside cram.py,
where we wouldn't have to write a tempfile; in that case, would probably want
to specify a prefix so we could refer to history.

Example usage:

Normal usage - the output is not regexped for clarity, but pin and txid
change with each POST.
  $ $TESTDIR/client.py POST /verify/v1/call phone=5035551212 message=message
  200 OK
  {"stat": "OK", "response": {"pin": "7909", "txid": "0e18f346-891f-4f10-8480-828a126c846c"}}
We need that txid for this GET.
  $ $TESTDIR/client.py GET /verify/v1/status txid=XXX
  400 Bad Request
  {"stat": "FAIL", "code": 40003, "message": "Invalid txid"}

Write environment to /tmp/call-env - we probably want a $SCRATCHDIR.
  $ $TESTDIR/cram_helper.py --envout=/tmp/call_env $TESTDIR/client.py \
  > POST /verify/v1/call phone=5035551212 message=message
  200 OK
  {"stat": "OK", "response": {"pin": ".+", "txid": ".+"}} (re)
Now we have a very ugly env dict stored by position - we need a helper
for this, see comments source.  Again, not regexped for clarity.
  $ cat /tmp/call_env
  {'cram_env_2': '{"stat":', 'cram_env_3': '"OK",', 'cram_env_0': '200', 'cram_env_1': 'OK', 'cram_env_6': '"3959",', 'cram_env_7': '"txid":', 'cram_env_4': '"response":', 'cram_env_5': '{"pin":', 'cram_env_8': '"1092e2e0-6d93-4c3f-929b-f22b3545850c"}}'}
Q&D clean up to make it usable - this is not happy.
  $ $TESTDIR/env_munger.py /tmp/call_env
Show the cleaned up env file, not regexped for clarity.
  $ cat /tmp/call_env
  {'cram_env_8': 'fa28aead-583d-4040-bb71-29789532020d'}
Now we can test success with that env var.
  $ $TESTDIR/cram_helper.py --envin=/tmp/call_env $TESTDIR/client.py GET /verify/v1/status txid='$cram_env_8'
  200 OK
  {"stat": "OK", "response": {"info": "Call request initialized", "state": "started", "event": "INITIALIZED"}}

"""
import getopt
import os, sys, subprocess #, shlex

def read_env(env_filename):
    """
    Return the evaluated contetns of filename.  Contents are assumed to be safe
    to eval.
    """
    env_file = open(env_filename)
    env = eval(env_file.read())
    env_file.close()
    return env

def write_env(env_d, env_filename):
    """
    Write the repr of env_d to env_filename.
    """
    env_file = open(env_filename, 'w')
    env_file.write(repr(env_d))
    env_file.write('\n')
    env_file.close()

def usage():
    sys.stderr.write(
        'usage: %s [--json] [--xml] [--position] '
        '[--envin=<file>] [--envout=<file>] '
        '<command>...\n'
        'only one of --json, --xml, --position can be chosen\n' % sys.argv[0])
    sys.exit(1)

def main():
    parse_json = False
    parse_xml = False
    parse_position = False
    get_stdin = False
    get_stderr = False
    env_in = os.environ.copy()
    env_out = None
    
    # Since we only get args from the front, we don't need -- or similar.
    (optlist, args) = getopt.getopt(
        sys.argv[1:], '',
        ['json', 'xml', 'position', 'envin=', 'envout='])
    opt_d = dict(optlist)

    # I want json and xml helpers, but would need a way to express how the
    # structures should be translated into the env.  Maybe it would be good
    # enough to be able to specify that the entire parsed stream should be
    # written to the env file, so --envin can specify the helper which should
    # eval it.
    if opt_d.has_key('--json'):
        raise NotImplementedError
    elif opt_d.has_key('--xml'):
        raise NotImplementedError
    elif opt_d.has_key('--position'):
        parse_position = True

    elif opt_d.has_key('--stdin'):
        get_stdin = True
    elif opt_d.has_key('--stderr'):
        get_stderr = True
        
    if opt_d.has_key('--envin'):
        env_in.update(read_env(opt_d['--envin']))
    if opt_d.has_key('--envout'):
        env_out = opt_d['--envout']

    # default is position
    if not any([parse_json, parse_xml, parse_position]):
        parse_position = True
    # default is stdin
    if not any([get_stdin, get_stderr]):
        get_stdin = True
        
    # choose only one
    if len(
        [opt for opt in [parse_json, parse_xml, parse_position] if opt]) > 1:
        usage()
    if len([opt for opt in [get_stdin, get_stderr] if opt]) > 1:
        usage()
    if len(args) < 1:
        usage()

    command = ' '.join(args)

    p = subprocess.Popen(['/bin/sh', '-'], bufsize=-1, stdin=subprocess.PIPE,
                         stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                         universal_newlines=True, env=env_in,
                         close_fds=os.name == 'posix')
    p.stdin.write(' '.join(args))
    (stdout, stderr) = p.communicate()

    if get_stderr:
        stream = stderr
    else:
        stream = stdout
    if env_out:
        if parse_position:
            # XXX should be able to specify an env var prefix
            env_vars = dict(
                [('cram_env_%s' % i, var)
                 for (i, var) in enumerate(stream.split())])
            write_env(env_vars, env_out)
        else:
            raise NotImplementedError       # json, xml
        
    sys.stdout.write(stdout)
    sys.stderr.write(stderr)
    sys.exit(p.returncode)

if __name__ == '__main__':
    main()