#!/usr/bin/env python

# Copyright (c) 2020 Egor Tensin <egor@tensin.name>
# This file is part of the "cmake-common" project.
# For details, see https://github.com/egor-tensin/cmake-common
# Distributed under the MIT License.

"""clang-format all C/C++ files in the project

This script feeds every C/C++ file in the repository to clang-format, either
printing a unified diff between the original and the formatted versions, or
formatting the files in-place.
"""

import argparse
from contextlib import contextmanager
import difflib
import logging
import os
import subprocess
import sys


@contextmanager
def setup_logging():
    level_names = {
        logging.DEBUG: "DBG",
        logging.INFO: "INFO",
        logging.WARNING: "WARN",
        logging.ERROR: "ERR",
        logging.CRITICAL: "CRIT",
    }
    for lvl, name in level_names.items():
        logging.addLevelName(lvl, name)

    logging.basicConfig(
        level=logging.INFO,
        datefmt="%Y-%m-%d %H:%M:%S%z",
        format="%(asctime)s | %(levelname)4s | %(message)s",
    )
    try:
        yield
    except Exception as e:
        logging.exception(e)
        sys.exit(1)


@contextmanager
def cd(path):
    cwd = os.getcwd()
    os.chdir(path)
    try:
        yield
    finally:
        os.chdir(cwd)


def normalize_path(entry):
    return os.path.abspath(entry)


def run(cmd_line):
    logging.debug("Running executable: %s", cmd_line)
    try:
        return subprocess.run(
            cmd_line,
            check=True,
            universal_newlines=True,
            stderr=subprocess.STDOUT,
            stdout=subprocess.PIPE,
        )
    except subprocess.CalledProcessError as e:
        logging.error("Process finished with exit code %d: %s", e.returncode, cmd_line)
        logging.error("Its output was:\n%s", e.output)
        raise


def read_file(path):
    with open(path) as file:
        return file.read()


class ClangFormat:
    def __init__(self, path, style):
        self.path = path
        self.style = style

    def _get_command_line(self, paths, in_place=False):
        cmd_line = [self.path, f"-style={self.style}"]
        if in_place:
            cmd_line.append("-i")
        cmd_line.append("--")
        cmd_line += list(paths)
        return cmd_line

    def format_in_place(self, paths):
        run(self._get_command_line(paths, in_place=True))

    @staticmethod
    def _show_diff(path, formatted):
        original = read_file(path)
        if original and not formatted:
            # Assuming this file is ignored in .clang-format-ignore.
            return True

        original = original.split("\n")
        formatted = formatted.split("\n")
        original_lbl = f"{path} (original)"
        formatted_lbl = f"{path} (formatted)"

        diff = difflib.unified_diff(
            original,
            formatted,
            fromfile=original_lbl,
            tofile=formatted_lbl,
            lineterm="",
        )

        clean = True
        for line in diff:
            clean = False
            print(line)
        return clean

    def show_diff(self, paths):
        clean = True
        for path in paths:
            formatted = run(self._get_command_line([path])).stdout
            clean = self._show_diff(path, formatted) and clean
        return clean


def git_root_dir():
    cmd_line = ["git", "rev-parse", "--show-toplevel"]
    root_dir = run(cmd_line).stdout
    if root_dir[-1] != "\n":
        raise RuntimeError("git rev-parse --show-toplevel should append a newline?")
    return root_dir[:-1]


def list_git_files():
    cmd_line = ["git", "ls-tree", "-r", "-z", "--name-only", "HEAD"]
    repo_files = run(cmd_line).stdout
    repo_files = repo_files.split("\0")
    return repo_files


def list_all_files():
    return (normalize_path(path) for path in list_git_files())


def excluded(path, exclude):
    for entry in exclude:
        if entry == os.path.commonpath((path, entry)):
            return True
    return False


def filter_files(paths, exclude):
    if not exclude:
        return paths
    return (path for path in paths if not excluded(path, exclude))


CPP_FILE_EXTENSIONS = set(
    (".c", ".h", ".cc", ".hh", ".cpp", ".hpp", ".cxx", ".hxx", ".cp", ".c++")
)


def list_cpp_files():
    for path in list_all_files():
        ext = os.path.splitext(path)[1].lower()
        if ext in CPP_FILE_EXTENSIONS:
            yield path


DEFAULT_VERSION = "clang-format"
DEFAULT_STYLE = "file"


def process_cpp_files(
    version=DEFAULT_VERSION, style=DEFAULT_STYLE, in_place=False, exclude=None
):
    clang_format = ClangFormat(version, style)
    with cd(git_root_dir()):
        cpp_files = filter_files(list_cpp_files(), exclude)
        if in_place:
            clang_format.format_in_place(cpp_files)
        else:
            if not clang_format.show_diff(cpp_files):
                sys.exit(1)


def parse_args(argv=None):
    if argv is None:
        argv = sys.argv[1:]

    parser = argparse.ArgumentParser(
        description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter
    )

    parser.add_argument(
        "-b",
        "--clang-format",
        dest="version",
        default=DEFAULT_VERSION,
        help="clang-format executable file path",
    )
    parser.add_argument(
        "-s",
        "--style",
        default=DEFAULT_STYLE,
        help="clang-format -style parameter argument",
    )
    parser.add_argument(
        "-i", "--in-place", action="store_true", help="edit the files in-place"
    )
    parser.add_argument(
        "-e",
        "--exclude",
        nargs="*",
        type=normalize_path,
        help="files or directories to exclude",
    )

    return parser.parse_args(argv)


def main(argv=None):
    args = parse_args(argv)
    with setup_logging():
        process_cpp_files(**vars(args))


if __name__ == "__main__":
    main()