"""Protected phrase extraction, storage, and runtime matching."""

from __future__ import annotations

import logging
import tomllib
from functools import cache
from pathlib import Path

from python.ebook_search.protected_phrases.text_normalization import normalize_text

logger = logging.getLogger(__name__)


def _load_toml_string_set(path: Path, key: str) -> frozenset[str]:
    """Load and validate a TOML string list as a normalized immutable set."""
    with path.open("rb") as file:
        body = tomllib.load(file)

    values = body.get(key)
    if not isinstance(values, list) or not all(isinstance(item, str) for item in values):
        msg = f"{path} must contain a {key!r} string list"
        raise ValueError(msg)
    return frozenset(normalize_text(value) for value in values if normalize_text(value))


@cache
def _get_phrase_config_dir() -> Path:
    """Return the directory containing phrase configuration files."""
    return Path(__file__).resolve().parent


@cache
def get_ignored_phrases() -> frozenset[str]:
    """Return ignored phrase strings loaded from TOML."""
    return _load_toml_string_set(_get_phrase_config_dir() / "ignored_phrases.toml", "phrases")


@cache
def get_bad_ends() -> frozenset[str]:
    """Return bad phrase-ending tokens loaded from TOML."""
    return _load_toml_string_set(_get_phrase_config_dir() / "bad_ends.toml", "tokens")


@cache
def get_bad_starts() -> frozenset[str]:
    """Return bad phrase-starting tokens loaded from TOML."""
    return _load_toml_string_set(_get_phrase_config_dir() / "bad_starts.toml", "tokens")


@cache
def get_most_common_words() -> frozenset[str]:
    """Return the most common English words loaded from TOML."""
    return _load_toml_string_set(_get_phrase_config_dir() / "most_common_words.toml", "words")