from functools import lru_cache
import pyparsing as pp


@lru_cache(maxsize=None)
def camel_to_snake(s: str) -> str:
    """
    Convert CamelCase to snake_case.
    """
    return "".join("_" + c.lower() if c.isupper() else c for c in s).lstrip("_")


pre_pep8_method_names = """
addCondition addParseAction anyCloseTag anyOpenTag asDict asList cStyleComment canParseNext conditionAsParseAction 
convertToDate convertToDatetime convertToFloat convertToInteger countedArray cppStyleComment dblQuotedString 
dblSlashComment defaultName dictOf disableMemoization downcaseTokens enableLeftRecursion enablePackrat getName 
htmlComment ignoreWhitespace indentedBlock infixNotation inlineLiteralsUsing javaStyleComment leaveWhitespace 
lineEnd lineStart locatedExpr matchOnlyAtCol matchPreviousExpr matchPreviousLiteral nestedExpr nullDebugAction oneOf 
originalTextFor parseFile parseString parseWithTabs pythonStyleComment quotedString removeQuotes replaceWith 
resetCache restOfLine runTests scanString searchString setBreak setDebug setDebugActions setDefaultWhitespaceChars 
setFailAction setName setParseAction setResultsName setWhitespaceChars sglQuotedString stringEnd stringStart tokenMap 
traceParseAction transformString tryParse unicodeString upcaseTokens withAttribute withClass
""".split()

special_changes = {
    "opAssoc": "OpAssoc",
    "delimitedList": "DelimitedList",
    "delimited_list": "DelimitedList",
    "replaceHTMLEntity": "replace_html_entity",
    "makeHTMLTags": "make_html_tags",
    "makeXMLTags": "make_xml_tags",
    "commonHTMLEntity": "common_html_entity",
    "stripHTMLTags": "strip_html_tags",
}

pre_pep8_arg_names = """parseAll maxMatches listAllMatches callDuringTry includeSeparators fullDump printResults 
failureTests postParse matchString identChars maxMismatches initChars bodyChars asKeyword excludeChars asGroupList 
asMatch quoteChar escChar escQuote unquoteResults endQuoteChar convertWhitespaceEscapes notChars wordChars stopOn 
failOn joinString markerString intExpr useRegex asString ignoreExpr""".split()

pre_pep8_method_name = pp.one_of(pre_pep8_method_names, as_keyword=True)
pre_pep8_method_name.set_parse_action(lambda t: camel_to_snake(t[0]))
special_pre_pep8_name = pp.one_of(special_changes, as_keyword=True)
special_pre_pep8_name.set_parse_action(lambda t: special_changes[t[0]])
# only replace arg names if part of an arg list
pre_pep8_arg_name = pp.Regex(
    rf"{pp.util.make_compressed_re(pre_pep8_arg_names)}\s*="
)
pre_pep8_arg_name.set_parse_action(lambda t: camel_to_snake(t[0]))

pep8_converter = pre_pep8_method_name | special_pre_pep8_name | pre_pep8_arg_name

if __name__ == "__main__":
    import argparse
    from pathlib import Path
    import sys

    argparser = argparse.ArgumentParser(
        description = (
            "Utility to convert Python pyparsing scripts using legacy"
            " camelCase names to use PEP8 snake_case names."
            "\nBy default, this script will only show whether this script would make any changes."
        )
    )
    argparser.add_argument("--verbose", "-v", action="store_true", help="Show unified diff for each source file")
    argparser.add_argument("-vv", action="store_true", dest="verbose2", help="Show unified diff for each source file, plus names of scanned files with no changes")
    argparser.add_argument("--update", "-u", action="store_true", help="Update source files in-place")
    argparser.add_argument("--encoding", type=str, default="utf-8", help="Encoding of source files (default: utf-8)")
    argparser.add_argument("--exit-zero-even-if-changed", "-exit0", action="store_true", help="Exit with status code 0 even if changes were made")
    argparser.add_argument("source_filename", nargs="+", help="Source filenames or filename patterns of Python files to be converted")
    args = argparser.parse_args()


    def show_diffs(original, modified):
        import difflib

        diff = difflib.unified_diff(
            original.splitlines(), modified.splitlines(), lineterm=""
        )
        sys.stdout.writelines(f"{diff_line}\n" for diff_line in diff)

    exit_status = 0

    for filename_pattern in args.source_filename:

        for filename in Path().glob(filename_pattern):
            if not Path(filename).is_file():
                continue

            try:
                original_contents = Path(filename).read_text(encoding=args.encoding)
                modified_contents = pep8_converter.transform_string(
                    original_contents
                )

                if modified_contents != original_contents:
                    if args.update:
                        Path(filename).write_text(modified_contents, encoding=args.encoding)
                        print(f"Converted {filename}")
                    else:
                        print(f"Found required changes in {filename}")

                    if args.verbose:
                        show_diffs(original_contents, modified_contents)
                        print()

                    exit_status = 1

                else:
                    if args.verbose2:
                        print(f"No required changes in {filename}")

            except Exception as e:
                print(f"Failed to convert {filename}: {type(e).__name__}: {e}")

    sys.exit(exit_status if not args.exit_zero_even_if_changed else 0)