#!/usr/bin/env python3
#
# ===-----------------------------------------------------------------------===#
#
# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
# See https://llvm.org/LICENSE.txt for license information.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#
# ===-----------------------------------------------------------------------===#

r"""
ClangTidy Diff Checker
======================

This script reads input from a unified diff, runs clang-tidy on all changed
files and outputs clang-tidy warnings in changed lines only. This is useful to
detect clang-tidy regressions in the lines touched by a specific patch.
Example usage for git/svn users:

  git diff -U0 HEAD^ | clang-tidy-diff.py -p1
  svn diff --diff-cmd=diff -x-U0 | \
      clang-tidy-diff.py -fix -checks=-*,modernize-use-override

"""

import argparse
import glob
import json
import multiprocessing
import os
import queue
import re
import shutil
import subprocess
import sys
import tempfile
import threading
import traceback
from pathlib import Path

try:
    import yaml
except ImportError:
    yaml = None


def run_tidy(task_queue, lock, timeout, failed_files):
    watchdog = None
    while True:
        command = task_queue.get()
        try:
            proc = subprocess.Popen(
                command, stdout=subprocess.PIPE, stderr=subprocess.PIPE
            )

            if timeout is not None:
                watchdog = threading.Timer(timeout, proc.kill)
                watchdog.start()

            stdout, stderr = proc.communicate()
            if proc.returncode != 0:
                if proc.returncode < 0:
                    msg = "Terminated by signal %d : %s\n" % (
                        -proc.returncode,
                        " ".join(command),
                    )
                    stderr += msg.encode("utf-8")
                failed_files.append(command)

            with lock:
                sys.stdout.write(stdout.decode("utf-8") + "\n")
                sys.stdout.flush()
                if stderr:
                    sys.stderr.write(stderr.decode("utf-8") + "\n")
                    sys.stderr.flush()
        except Exception as e:
            with lock:
                sys.stderr.write("Failed: " + str(e) + ": ".join(command) + "\n")
        finally:
            with lock:
                if not (timeout is None or watchdog is None):
                    if not watchdog.is_alive():
                        sys.stderr.write(
                            "Terminated by timeout: " + " ".join(command) + "\n"
                        )
                    watchdog.cancel()
            task_queue.task_done()


def start_workers(max_tasks, tidy_caller, arguments):
    for _ in range(max_tasks):
        t = threading.Thread(target=tidy_caller, args=arguments)
        t.daemon = True
        t.start()


def merge_replacement_files(tmpdir, mergefile):
    """Merge all replacement files in a directory into a single file"""
    # The fixes suggested by clang-tidy >= 4.0.0 are given under
    # the top level key 'Diagnostics' in the output yaml files
    mergekey = "Diagnostics"
    merged = []
    for replacefile in glob.iglob(os.path.join(tmpdir, "*.yaml")):
        content = yaml.safe_load(open(replacefile, "r"))
        if not content:
            continue  # Skip empty files.
        merged.extend(content.get(mergekey, []))

    if merged:
        # MainSourceFile: The key is required by the definition inside
        # include/clang/Tooling/ReplacementsYaml.h, but the value
        # is actually never used inside clang-apply-replacements,
        # so we set it to '' here.
        output = {"MainSourceFile": "", mergekey: merged}
        with open(mergefile, "w") as out:
            yaml.safe_dump(output, out)
    else:
        # Empty the file:
        open(mergefile, "w").close()


def get_compiling_files(args):
    """Read a compile_commands.json database and return a set of file paths"""
    current_dir = Path.cwd()
    compile_commands_json = (
        (current_dir / args.build_path) if args.build_path else current_dir
    )
    compile_commands_json = compile_commands_json / "compile_commands.json"
    files = set()
    with open(compile_commands_json) as db_file:
        db_json = json.load(db_file)
        for entry in db_json:
            if "file" not in entry:
                continue
            files.add(Path(entry["file"]))
    return files


def main():
    parser = argparse.ArgumentParser(
        description="Run clang-tidy against changed files, and "
        "output diagnostics only for modified "
        "lines."
    )
    parser.add_argument(
        "-clang-tidy-binary",
        metavar="PATH",
        default="clang-tidy",
        help="path to clang-tidy binary",
    )
    parser.add_argument(
        "-p",
        metavar="NUM",
        default=0,
        help="strip the smallest prefix containing P slashes",
    )
    parser.add_argument(
        "-regex",
        metavar="PATTERN",
        default=None,
        help="custom pattern selecting file paths to check "
        "(case sensitive, overrides -iregex)",
    )
    parser.add_argument(
        "-iregex",
        metavar="PATTERN",
        default=r".*\.(cpp|cc|c\+\+|cxx|c|cl|h|hpp|m|mm|inc)",
        help="custom pattern selecting file paths to check "
        "(case insensitive, overridden by -regex)",
    )
    parser.add_argument(
        "-j",
        type=int,
        default=0,
        help="number of tidy instances to be run in parallel.",
    )
    parser.add_argument(
        "-timeout", type=int, default=None, help="timeout per each file in seconds."
    )
    parser.add_argument(
        "-fix", action="store_true", default=False, help="apply suggested fixes"
    )
    parser.add_argument(
        "-checks",
        help="checks filter, when not specified, use clang-tidy " "default",
        default="",
    )
    parser.add_argument(
        "-config-file",
        dest="config_file",
        help="Specify the path of .clang-tidy or custom config file",
        default="",
    )
    parser.add_argument("-use-color", action="store_true", help="Use colors in output")
    parser.add_argument(
        "-path", dest="build_path", help="Path used to read a compile command database."
    )
    if yaml:
        parser.add_argument(
            "-export-fixes",
            metavar="FILE_OR_DIRECTORY",
            dest="export_fixes",
            help="A directory or a yaml file to store suggested fixes in, "
            "which can be applied with clang-apply-replacements. If the "
            "parameter is a directory, the fixes of each compilation unit are "
            "stored in individual yaml files in the directory.",
        )
    else:
        parser.add_argument(
            "-export-fixes",
            metavar="DIRECTORY",
            dest="export_fixes",
            help="A directory to store suggested fixes in, which can be applied "
            "with clang-apply-replacements. The fixes of each compilation unit are "
            "stored in individual yaml files in the directory.",
        )
    parser.add_argument(
        "-extra-arg",
        dest="extra_arg",
        action="append",
        default=[],
        help="Additional argument to append to the compiler " "command line.",
    )
    parser.add_argument(
        "-extra-arg-before",
        dest="extra_arg_before",
        action="append",
        default=[],
        help="Additional argument to prepend to the compiler " "command line.",
    )
    parser.add_argument(
        "-quiet",
        action="store_true",
        default=False,
        help="Run clang-tidy in quiet mode",
    )
    parser.add_argument(
        "-load",
        dest="plugins",
        action="append",
        default=[],
        help="Load the specified plugin in clang-tidy.",
    )
    parser.add_argument(
        "-allow-no-checks",
        action="store_true",
        help="Allow empty enabled checks.",
    )
    parser.add_argument(
        "-only-check-in-db",
        dest="skip_non_compiling",
        default=False,
        action="store_true",
        help="Only check files in the compilation database",
    )
    parser.add_argument(
        "-warnings-as-errors",
        help="Upgrades clang-tidy warnings to errors. Same format as '-checks'.",
        default="",
    )
    parser.add_argument(
        "-hide-progress",
        action="store_true",
        help="Hide progress",
    )

    clang_tidy_args = []
    argv = sys.argv[1:]
    if "--" in argv:
        clang_tidy_args.extend(argv[argv.index("--") :])
        argv = argv[: argv.index("--")]

    args = parser.parse_args(argv)

    compiling_files = get_compiling_files(args) if args.skip_non_compiling else None

    # Extract changed lines for each file.
    filename = None
    lines_by_file = {}
    for line in sys.stdin:
        match = re.search(r'^\+\+\+\ "?(.*?/){%s}([^ \t\n"]*)' % args.p, line)
        if match:
            filename = match.group(2)
        if filename is None:
            continue

        if args.regex is not None:
            if not re.match("^%s$" % args.regex, filename):
                continue
        else:
            if not re.match("^%s$" % args.iregex, filename, re.IGNORECASE):
                continue

        # Skip any files not in the compiling list
        if (
            compiling_files is not None
            and (Path.cwd() / filename) not in compiling_files
        ):
            continue

        match = re.search(r"^@@.*\+(\d+)(,(\d+))?", line)
        if match:
            start_line = int(match.group(1))
            line_count = 1
            if match.group(3):
                line_count = int(match.group(3))
            if line_count == 0:
                continue
            end_line = start_line + line_count - 1
            lines_by_file.setdefault(filename, []).append([start_line, end_line])

    if not any(lines_by_file):
        print("No relevant changes found.")
        sys.exit(0)

    max_task_count = args.j
    if max_task_count == 0:
        max_task_count = multiprocessing.cpu_count()
    max_task_count = min(len(lines_by_file), max_task_count)
    if not args.hide_progress:
        print(f"Running clang-tidy in {max_task_count} threads...")

    combine_fixes = False
    export_fixes_dir = None
    delete_fixes_dir = False
    if args.export_fixes is not None:
        # if a directory is given, create it if it does not exist
        if args.export_fixes.endswith(os.path.sep) and not os.path.isdir(
            args.export_fixes
        ):
            os.makedirs(args.export_fixes)

        if not os.path.isdir(args.export_fixes):
            if not yaml:
                raise RuntimeError(
                    "Cannot combine fixes in one yaml file. Either install PyYAML or specify an output directory."
                )

            combine_fixes = True

        if os.path.isdir(args.export_fixes):
            export_fixes_dir = args.export_fixes

    if combine_fixes:
        export_fixes_dir = tempfile.mkdtemp()
        delete_fixes_dir = True

    # Tasks for clang-tidy.
    task_queue = queue.Queue(max_task_count)
    # A lock for console output.
    lock = threading.Lock()

    # List of files with a non-zero return code.
    failed_files = []

    # Run a pool of clang-tidy workers.
    start_workers(
        max_task_count, run_tidy, (task_queue, lock, args.timeout, failed_files)
    )

    # Form the common args list.
    common_clang_tidy_args = []
    if args.fix:
        common_clang_tidy_args.append("-fix")
    if args.checks != "":
        common_clang_tidy_args.append("-checks=" + args.checks)
    if args.config_file != "":
        common_clang_tidy_args.append("-config-file=" + args.config_file)
    if args.quiet:
        common_clang_tidy_args.append("-quiet")
    if args.build_path is not None:
        common_clang_tidy_args.append("-p=%s" % args.build_path)
    if args.use_color:
        common_clang_tidy_args.append("--use-color")
    if args.allow_no_checks:
        common_clang_tidy_args.append("--allow-no-checks")
    for arg in args.extra_arg:
        common_clang_tidy_args.append("-extra-arg=%s" % arg)
    for arg in args.extra_arg_before:
        common_clang_tidy_args.append("-extra-arg-before=%s" % arg)
    for plugin in args.plugins:
        common_clang_tidy_args.append("-load=%s" % plugin)
    if args.warnings_as_errors:
        common_clang_tidy_args.append("-warnings-as-errors=" + args.warnings_as_errors)

    for name in lines_by_file:
        line_filter_json = json.dumps(
            [{"name": name, "lines": lines_by_file[name]}], separators=(",", ":")
        )

        # Run clang-tidy on files containing changes.
        command = [args.clang_tidy_binary]
        command.append("-line-filter=" + line_filter_json)
        if args.export_fixes is not None:
            # Get a temporary file. We immediately close the handle so clang-tidy can
            # overwrite it.
            (handle, tmp_name) = tempfile.mkstemp(suffix=".yaml", dir=export_fixes_dir)
            os.close(handle)
            command.append("-export-fixes=" + tmp_name)
        command.extend(common_clang_tidy_args)
        command.append(name)
        command.extend(clang_tidy_args)

        task_queue.put(command)

    # Application return code
    return_code = 0

    # Wait for all threads to be done.
    task_queue.join()
    # Application return code
    return_code = 0
    if failed_files:
        return_code = 1

    if combine_fixes:
        if not args.hide_progress:
            print(f"Writing fixes to {args.export_fixes} ...")
        try:
            merge_replacement_files(export_fixes_dir, args.export_fixes)
        except:
            sys.stderr.write("Error exporting fixes.\n")
            traceback.print_exc()
            return_code = 1

    if delete_fixes_dir:
        shutil.rmtree(export_fixes_dir)
    sys.exit(return_code)


if __name__ == "__main__":
    main()