#!/usr/bin/env python3
"""
Analogous to clang-check, but for use with GCC. Intended use:

    cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=1 $srcdir
    gcc-check path/to/source1.c path/to/source2.c

Like clang-check, you can also add extra compiler options:

    gcc-check -extra-arg=-Wno-missing-prototypes path/to/source.c
"""
import argparse
import json
import os
import shlex
import subprocess
import sys


def llvm_abspath(path):
    # Deliberately preserves ".." in path="../x" for LLVM compatibility.
    return os.path.join(os.getcwd(), path)


# Make paths absolute (simplifying "a/../b" to "b")
#canonicalize_path = os.path.abspath
canonicalize_path = os.path.realpath


def locate_compilation_database(path):
    path = llvm_abspath(path)
    if not os.path.isdir(path):
        path = os.path.dirname(path)
    while True:
        db_path = os.path.join(path, 'compile_commands.json')
        if os.path.exists(db_path):
            return db_path
        if path == '/':
            break
        path = os.path.dirname(path)
    print('Could not auto-detect compilation database', file=sys.stderr)


class DbEntry(object):
    def __init__(self, obj):
        def readstr(key):
            value = obj.get(key)
            if type(value) != str:
                raise RuntimeError('Key %s not found' % key)
            return value
        self.directory = readstr('directory')
        self.file = readstr('file')
        self.command = readstr('command')
        self.filepath = canonicalize_path(self.file)

    def __str__(self):
        return '{"directory": %r, "command": %r, "file": %r}' % \
            (self.directory, self.command, self.file)

    def check(self, extra_arg_before=[], extra_arg=[]):
        args = shlex.split(self.command)
        is_cpp = args[0].endswith('++')
        args[0] = ['gcc', 'g++'][is_cpp]
        args += extra_arg_before
        args = [arg for arg in args if self._filter_cc_arg(arg, is_cpp)]
        args += extra_arg
        args += ['-fsyntax-only']
        #print("Command: is_cpp=%r %r" % (is_cpp, args), file=sys.stderr)
        subprocess.run(args, cwd=self.directory)

    def _filter_cc_arg(self, arg, is_cpp):
        # List of Clang-specific options that are not supported by GCC.
        # (as added by Wireshark)
        common_args = [
            '-Qunused-arguments',
            '-Wheader-guard',
            '-Wcomma',
            '-Wshorten-64-to-32',
            '-Weverything',
            '-Wno-documentation-unknown-command',
            '-Wno-reserved-id-macro',
        ]
        c_args = [
        ]
        cpp_args = [
            '-Wextra-semi',
        ]
        return arg not in common_args + (cpp_args if not is_cpp else c_args)


def parse_db(entries, db_path):
    with open(db_path) as f:
        arr = json.load(f)
        if type(arr) != list:
            raise RuntimeError('Parse Error: expected array')
        for obj in arr:
            entry = DbEntry(obj)
            entries[entry.filepath] = entry


parser = argparse.ArgumentParser()
parser.add_argument('-p', metavar='string', dest='build_path',
                    help='Build path')
parser.add_argument('-extra-arg', metavar='string', dest='extra_arg',
                    action='append', default=[],
                    help='Additional argument to append to the compiler command line')
parser.add_argument('-extra-arg-before', metavar='string',
                    dest='extra_arg_before',
                    action='append', default=[],
                    help='Additional argument to prepend to the compiler command line')
parser.add_argument('sources', nargs='+')


def main():
    args = parser.parse_args()
    sources = [canonicalize_path(path) for path in args.sources]
    build_path = args.build_path
    if not build_path or not os.path.exists(build_path):
        build_path = llvm_abspath(args.sources[0])
    db_path = locate_compilation_database(build_path)
    db = {}
    if db_path:
        parse_db(db, db_path)
    for source_path in sources:
        entry = db.get(source_path)
        if entry is None:
            print('Skipping %s. Compile command not found.' % source_path,
                  file=sys.stderr)
            continue
        entry.check(args.extra_arg_before, args.extra_arg)


if __name__ == '__main__':
    main()