#!/usr/bin/python3

# SPDX-License-Identifier: GPL-2.0

# Author: Clark Williams <williams@redhat.com>

# Copyright (C) 2022 Red Hat, Inc.

#

# merge.py - a direct replacement for merge.pl in the redhat/configs directory

#

# invocation:   python merge.py overrides baseconfig [arch]

#

# This script merges two kernel configuration files, an override file and a

# base config file and writes the results to stdout.

#

# The script reads the overrides into a dictionary, then reads the baseconfig

# file, looking for overrides and replacing any found, then printing the result

# to stdout. Finally any remaining (new) configs in the override are appended to the

# end of the output

import sys

import re

import os.path

def usage(msg):

    '''print a usage message and exit'''

    sys.stderr.write(msg + "\n")

    sys.stderr.write("usage: merge.py overrides baseconfig [arch]\n")

    sys.exit(1)

isset = re.compile(r'^(CONFIG_\w+)=')

notset = re.compile(r'^#\s+(CONFIG_\w+)\s+is not set')

# search an input line for a config (set or notset) pattern

# if we get a match return the config that is being changed

def find_config(line):

    '''find a configuration line in the input and return the config name'''

    m = isset.match(line)

    if (m is not None):

        return m.group(1)

    m = notset.match(line)

    if (m is not None):

        return m.group(1)

    return None

#########################################################

if len(sys.argv) < 3:

    usage("must have two input files")

override_file = sys.argv[1]

baseconfig_file = sys.argv[2]

if not os.path.exists(override_file):

    usage(f"overrides config file {override_file:s} does not exist!")

if not os.path.exists(baseconfig_file):

    usage(f"base configs file {baseconfig_file:s} does not exist")

if len(sys.argv) == 4:

    print(f"# {sys.argv[3]:s}")

# read each line of the override file and store any configuration values

# in the overrides dictionary, keyed by the configuration name.

overrides = {}

with open(override_file, "rt", encoding="utf-8") as f:

    for line in [l.strip() for l in f.readlines()]:

        c = find_config(line)

        if c and c not in overrides:

            overrides[c] = line

# now read and print the base config, checking each line

# that defines a config value and printing the override if

# it exists

with open(baseconfig_file, "rt", encoding="utf-8") as f:

    for line in [ l.strip() for l in f.readlines() ]:

        c = find_config(line)

        if c and c in overrides:

            print(overrides[c])

            del overrides[c]

        else:

            print(line)

# print out the remaining configs (new values)

# from the overrides file

for v in overrides.values():

    print (v)

sys.exit(0)