#!/usr/bin/env python3

# Copyright 2020 gRPC authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# This is based on the script on the Envoy project
# https://github.com/envoyproxy/envoy/blob/master/tools/gen_compilation_database.py

import argparse
import glob
import json
import logging
import os
from pathlib import Path
import re
import shlex
import subprocess

RE_INCLUDE_SYSTEM = re.compile("\s*-I\s+/usr/[^ ]+")


# This method is equivalent to https://github.com/grailbio/bazel-compilation-database/blob/master/generate.sh
def generateCompilationDatabase(args):
    # We need to download all remote outputs for generated source code.
    # This option lives here to override those specified in bazelrc.
    bazel_options = shlex.split(os.environ.get("BAZEL_BUILD_OPTIONS", "")) + [
        "--config=compdb",
        "--remote_download_outputs=all",
    ]

    subprocess.check_call(["bazel", "build"] + bazel_options + [
        "--aspects=@bazel_compdb//:aspects.bzl%compilation_database_aspect",
        "--output_groups=compdb_files,header_files"
    ] + args.bazel_targets)

    execroot = subprocess.check_output(["bazel", "info", "execution_root"] +
                                       bazel_options).decode().strip()

    compdb = []
    for compdb_file in Path(execroot).glob("**/*.compile_commands.json"):
        compdb.extend(
            json.loads(
                "[" +
                compdb_file.read_text().replace("__EXEC_ROOT__", execroot) +
                "]"))

    if args.dedup_targets:
        compdb_map = {target["file"]: target for target in compdb}
        compdb = list(compdb_map.values())

    return compdb


def isHeader(filename):
    for ext in (".h", ".hh", ".hpp", ".hxx"):
        if filename.endswith(ext):
            return True
    return False


def isCompileTarget(target, args):
    filename = target["file"]
    if not args.include_headers and isHeader(filename):
        return False
    if not args.include_genfiles:
        if filename.startswith("bazel-out/"):
            return False
    if not args.include_external:
        if filename.startswith("external/"):
            return False
    return True


def modifyCompileCommand(target, args):
    cc, options = target["command"].split(" ", 1)

    # Workaround for bazel added C++14 options, those doesn't affect build itself but
    # clang-tidy will misinterpret them.
    options = options.replace("-std=c++0x ", "")
    options = options.replace("-std=c++14 ", "")

    # Add -DNDEBUG so that editors show the correct size information for structs.
    options += " -DNDEBUG"

    if args.vscode:
        # Visual Studio Code doesn't seem to like "-iquote". Replace it with
        # old-style "-I".
        options = options.replace("-iquote ", "-I ")

    if args.ignore_system_headers:
        # Remove all include options for /usr/* directories
        options = RE_INCLUDE_SYSTEM.sub("", options)

    if isHeader(target["file"]):
        options += " -Wno-pragma-once-outside-header -Wno-unused-const-variable"
        options += " -Wno-unused-function"
        if not target["file"].startswith("external/"):
            # *.h file is treated as C header by default while our headers files are all C++14.
            options = "-x c++ -std=c++14 -fexceptions " + options

    target["command"] = " ".join([cc, options])
    return target


def fixCompilationDatabase(args, db):
    db = [
        modifyCompileCommand(target, args)
        for target in db
        if isCompileTarget(target, args)
    ]

    with open("compile_commands.json", "w") as db_file:
        json.dump(db, db_file, indent=2)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(
        description='Generate JSON compilation database')
    parser.add_argument('--include_external', action='store_true')
    parser.add_argument('--include_genfiles', action='store_true')
    parser.add_argument('--include_headers', action='store_true')
    parser.add_argument('--vscode', action='store_true')
    parser.add_argument('--ignore_system_headers', action='store_true')
    parser.add_argument('--dedup_targets', action='store_true')
    parser.add_argument('bazel_targets', nargs='*', default=["//..."])
    args = parser.parse_args()
    fixCompilationDatabase(args, generateCompilationDatabase(args))