#!/usr/bin/env python3
"""Applies fixes, generated by buildscripts/clang-tidy.py, across the codebase."""

import argparse
import hashlib
import json
import os
import sys
from collections import defaultdict


def is_writeable(file) -> bool:
    try:
        with open(file, "a") as f:  # noqa: F841
            pass
        return True
    except OSError:
        return False


def can_replacements_be_applied(replacements) -> bool:
    """Checks if the files containing replacements are unchanged since clang-tidy was run and are writeable.
    For any replacement to be valid, all impacted files must be unchanged."""
    for replacement in replacements:
        if (
            os.path.exists(replacement["FilePath"])
            and is_writeable(replacement["FilePath"])
            and replacement["FileContentsMD5"]
        ):
            with open(replacement["FilePath"], "rb") as fin:
                file_bytes = fin.read()
                current_md5 = hashlib.md5(file_bytes).hexdigest()
                if current_md5 != replacement["FileContentsMD5"]:
                    return False
        else:
            return False
    return True


def get_replacements_to_apply(fixes_file) -> dict:
    """Gets a per file listing of the valid replacements to apply."""
    replacements_to_apply = defaultdict(list)

    with open(fixes_file) as fin:
        fixes_data = json.load(fin)
        for clang_tidy_check in fixes_data:
            for main_source_file in fixes_data[clang_tidy_check]:
                for violation_instance in fixes_data[clang_tidy_check][main_source_file]:
                    replacements = fixes_data[clang_tidy_check][main_source_file][
                        violation_instance
                    ]["replacements"]
                    if can_replacements_be_applied(replacements):
                        for replacement in replacements:
                            replacements_to_apply[replacement["FilePath"]].append(replacement)
                    else:
                        print(
                            f"""WARNING: not applying replacements for {clang_tidy_check} in {main_source_file} at offset {violation_instance}, at least one file that is part of the automatic replacement has changed since clang-tidy was run, or is not writeable."""
                        )

    return replacements_to_apply


def main(argv=sys.argv[1:]):
    parser = argparse.ArgumentParser()
    parser.add_argument(dest="fixes_file", help="Path to fixes file.")
    args = parser.parse_args(argv)

    replacements_to_apply = get_replacements_to_apply(args.fixes_file)

    for file in replacements_to_apply:
        with open(file, "rb") as fin:
            file_bytes = fin.read()

        # perform the swap replacement of the binary data
        file_bytes = bytearray(file_bytes)
        replacements_to_apply[file].sort(key=lambda r: r["Offset"])
        adjustments = 0

        for replacement in replacements_to_apply[file]:
            file_bytes[
                replacement["Offset"] + adjustments : replacement["Offset"]
                + adjustments
                + replacement["Length"]
            ] = replacement["ReplacementText"].encode()

            if replacement["Length"] != len(replacement["ReplacementText"]):
                adjustments += len(replacement["ReplacementText"]) - replacement["Length"]

        with open(file, "wb") as fout:
            fout.write(bytes(file_bytes))


if __name__ == "__main__":
    main()