"""
This script asserts that Python config vars with compiler options including
one or more -O flags have the last specified -O flag equal to the script's
first argument.

We use it to check that the debug build (as well as extension modules) was
built with a desired optimization level (usually -Og or -O0).

About -O flags: https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
"If you use multiple -O options, with or without level numbers,
the last such option is the one that is effective."
"""

import sys
import sysconfig

# We will check all flags if none were requested
KEYS_TO_CHECK = sys.argv[2:] or list(sysconfig.get_config_vars().keys())
# For backwards compatibility, if no flags were provided, we assume flags without -O are to be skipped
# But when we provide explicit list of flags, we assert they get the options,
# so we can assert things like "CFLAGS has -O3" vs. "CFLAGS has no -O at all"
NO_FLAG_FAILS = bool(sys.argv[2:])

# The flags that currently don't have the -Og flag on the debug build
# and we consider it OK, because we don't know any better :)
SKIP = [
    'CONFIGURE_CFLAGS',
    'CONFIGURE_CFLAGS_NODIST',
    'CONFIG_ARGS',
    'OPT',
]

print('Expecting that {} is the last -O flag:\n'.format(sys.argv[1]))
ret = 0

for key in KEYS_TO_CHECK:
    if key in SKIP:
        continue
    flags = sysconfig.get_config_vars()[key]
    if isinstance(flags, str):
        oflags = [f for f in flags.split(' ') if f.startswith('-O')]
        if (oflags and oflags[-1] != sys.argv[1]) or (not oflags and NO_FLAG_FAILS):
            print('Problem in {} -O flags: {}'.format(key, ' '.join(oflags) or '<empty>'))
            ret = 1
        elif oflags:
            print('{} are OK'.format(key))

sys.exit(ret)