import sys
from pathlib import Path
import argparse
import re
import fnmatch


def is_five_letter_word(token: str) -> bool:
    token = token.strip()
    return len(token) == 5 and token.isalpha()


def main() -> int:
    parser = argparse.ArgumentParser(description="Filter 5-letter words from words.txt")
    parser.add_argument(
        "--only",
        metavar="LETTERS",
        help="Only include words composed solely of these letters (case-insensitive)",
    )
    parser.add_argument(
        "--exclude",
        metavar="LETTERS",
        help="Exclude words containing any of these letters (case-insensitive)",
    )
    parser.add_argument(
        "--mask",
        metavar="PATTERN",
        help=(
            "Position mask for 5 letters where '_' or '?' are wildcards, "
            "and letters fix positions (e.g., _A_E_)."
        ),
    )
    pattern_group = parser.add_mutually_exclusive_group()
    pattern_group.add_argument(
        "--regex",
        metavar="REGEX",
        help="Python regular expression to match words (defaults to case-insensitive)",
    )
    pattern_group.add_argument(
        "--glob",
        metavar="GLOB",
        help="Wildcard pattern (e.g., *A*E*) to match words (case-insensitive by default)",
    )
    parser.add_argument(
        "--case-sensitive",
        action="store_true",
        help="Make regex/glob matching case-sensitive (default is case-insensitive)",
    )
    args = parser.parse_args()

    only_set = set(args.only.lower()) if args.only else None
    exclude_set = set(args.exclude.lower()) if args.exclude else None

    # Prepare matchers
    # Validate and normalize mask
    mask_positions = None
    if args.mask is not None:
        mask = args.mask.strip()
        if len(mask) != 5:
            print("Invalid --mask: must be exactly 5 characters.", file=sys.stderr)
            return 2
        mask_positions = []
        for ch in mask:
            if ch in ("_", "?"):
                mask_positions.append(None)
            elif ch.isalpha():
                mask_positions.append(ch.lower())
            else:
                print(
                    "Invalid --mask: use letters or '_'/'?' as wildcards.",
                    file=sys.stderr,
                )
                return 2

    regex = None
    if args.regex:
        flags = 0 if args.case_sensitive else re.IGNORECASE
        try:
            regex = re.compile(args.regex, flags)
        except re.error as e:
            print(f"Invalid regex: {e}", file=sys.stderr)
            return 2

    glob_pattern = None
    if args.glob:
        glob_pattern = args.glob if args.case_sensitive else args.glob.lower()

    def matches(word: str) -> bool:
        if only_set is not None and not (set(word.lower()) <= only_set):
            return False
        if exclude_set is not None and (set(word.lower()) & exclude_set):
            return False
        if mask_positions is not None:
            wl = word.lower()
            for i, ch in enumerate(mask_positions):
                if ch is not None and wl[i] != ch:
                    return False
        if regex is not None and regex.search(word) is None:
            return False
        if glob_pattern is not None:
            if args.case_sensitive:
                if not fnmatch.fnmatchcase(word, glob_pattern):
                    return False
            else:
                if not fnmatch.fnmatchcase(word.lower(), glob_pattern):
                    return False
        return True

    words_path = Path("words.txt")
    if not words_path.exists():
        print("Error: words.txt not found in current directory.", file=sys.stderr)
        return 1

    # Read and stream 5-letter words to stdout
    try:
        with words_path.open("r", encoding="utf-8", errors="ignore") as f:
            for line in f:
                word = line.strip()
                if not word:
                    continue
                # If lines may contain multiple tokens, split defensively
                tokens = word.split()
                if len(tokens) == 1:
                    tok = tokens[0]
                    if is_five_letter_word(tok) and matches(tok):
                        print(tok)
                else:
                    for tok in tokens:
                        if is_five_letter_word(tok) and matches(tok):
                            print(tok)
    except OSError as e:
        print(f"Error reading words.txt: {e}", file=sys.stderr)
        return 1

    return 0


if __name__ == "__main__":
    raise SystemExit(main())