"""Conservative OCR cleanup and spoken-form expansion for magazine TTS."""
from __future__ import annotations

import itertools
import json
import re
from functools import lru_cache
from pathlib import Path

_DB_PATH = Path(__file__).with_name("pronunciations.json")
_WORD_RE = re.compile(r"\b[A-Za-zÄÖÜäöüß]{3,}\b")
_LINEBREAK_HYPHEN_RE = re.compile(
    r"(?<=[A-Za-zÄÖÜäöüß])-(?P<gap>\s+)(?P<next>[a-zäöüß][A-Za-zÄÖÜäöüß]*)"
)
_SUSPENDED_COMPOUND_WORDS = {"und", "oder", "beziehungsweise", "sowie"}
_GERMAN_HINTS = {
    "aber", "auch", "auf", "aus", "bei", "das", "dass", "der", "die", "ein",
    "eine", "einer", "einen", "für", "hat", "ist", "mit", "nicht", "oder", "sich",
    "sie", "und", "von", "werden", "wie", "zu",
}


@lru_cache(maxsize=1)
def pronunciation_db() -> dict:
    try:
        data = json.loads(_DB_PATH.read_text("utf-8"))
        return data if isinstance(data, dict) else {}
    except (OSError, ValueError):
        return {}


def remove_linebreak_hyphens(text: str) -> str:
    """Fuse a word split at a printed line end, preserving real compounds."""
    text = (text or "").replace("\u00ad", "")

    def fuse(match: re.Match) -> str:
        # ``Hardware- und Softwareentwicklung`` is a real suspended compound,
        # not a printed line break. OCR historically flattened newlines to a
        # space, so keep this small grammatical exception for saved layouts.
        if match.group("next").casefold() in _SUSPENDED_COMPOUND_WORDS:
            return match.group(0)
        return match.group("next")

    return _LINEBREAK_HYPHEN_RE.sub(fuse, text)


def detect_text_language(text: str) -> str:
    words = re.findall(r"[A-Za-zÄÖÜäöüß]+", (text or "").lower())
    if any(any(c in w for c in "äöüß") for w in words):
        return "de"
    hits = sum(1 for word in words if word in _GERMAN_HINTS)
    return "de" if hits >= max(2, len(words) // 40) else "en"


@lru_cache(maxsize=1)
def _german_spellchecker():
    try:
        from spellchecker import SpellChecker
        return SpellChecker(language="de", distance=1)
    except Exception:
        return None


def _match_case(source: str, replacement: str) -> str:
    if source.isupper() and len(source) > 1:
        return replacement.upper()
    if source[:1].isupper():
        return replacement[:1].upper() + replacement[1:]
    return replacement


def _umlaut_variants(word: str) -> set[str]:
    positions = [(i, {"a": "ä", "o": "ö", "u": "ü"}[c])
                 for i, c in enumerate(word) if c in "aou"]
    if not positions or len(positions) > 5:
        return set()
    variants = set()
    for count in range(1, len(positions) + 1):
        for chosen in itertools.combinations(positions, count):
            chars = list(word)
            for i, replacement in chosen:
                chars[i] = replacement
            variants.add("".join(chars))
    return variants


def restore_german_umlauts(text: str) -> str:
    """Restore only dictionary-backed, unambiguous missing umlauts."""
    explicit = {str(k).lower(): str(v) for k, v in
                (pronunciation_db().get("de_umlaut_repairs") or {}).items()}
    checker = _german_spellchecker()

    def replace(match: re.Match) -> str:
        token = match.group(0)
        lower = token.lower()
        if any(c in lower for c in "äöüß") or token.isupper():
            return token
        if lower in explicit:
            return _match_case(token, explicit[lower])
        # An unknown title-cased token is more likely to be a person's name,
        # product or place than a common noun. Explicit reviewed repairs above
        # may still correct a sentence-opening word such as ``Jahrlich``.
        if token != lower:
            return token
        if checker is None or lower in checker:
            return token
        known = [candidate for candidate in _umlaut_variants(lower) if candidate in checker]
        if len(known) != 1:
            return token
        return _match_case(token, known[0])

    return _WORD_RE.sub(replace, text or "")


def normalize_ocr_text(text: str, language: str = "auto") -> str:
    text = remove_linebreak_hyphens(text)
    lang = detect_text_language(text) if language == "auto" else language
    return restore_german_umlauts(text) if lang == "de" else text


def expand_abbreviations(text: str, language: str = "auto") -> str:
    lang = detect_text_language(text) if language == "auto" else language
    mapping = pronunciation_db().get(lang) or {}
    result = text or ""
    # Longest first so ``LLMs`` wins over ``LLM`` and dotted abbreviations
    # are consumed as one unit. Match tokens only, never substrings in names.
    for short, spoken in sorted(mapping.items(), key=lambda item: len(item[0]), reverse=True):
        pattern = r"(?<!\w)" + re.escape(short) + r"(?!\w)"
        result = re.sub(pattern, spoken, result)
    return result


def prepare_text_for_tts(text: str, language: str = "auto") -> str:
    return expand_abbreviations(normalize_ocr_text(text, language), language)