from __future__ import annotations

import logging
import re
import unicodedata
from dataclasses import dataclass
from difflib import SequenceMatcher
from typing import Any

import httpx
from config.settings import settings

logger = logging.getLogger(__name__)

SEARCH_URL = "https://openlibrary.org/search.json"
COVERS_URL = "https://covers.openlibrary.org/b/id/{cover_id}-{size}.jpg"
SEARCH_FIELDS = (
    "key,title,author_name,cover_i,first_publish_year,subject,language,"
    "edition_key,number_of_pages_median,publisher"
)

HIGH_CONFIDENCE = 0.8
LOW_CONFIDENCE = 0.6

# EPUB release noise often copied from filenames, e.g. "Title [6494] (r2.3)"
_TITLE_NOISE_PATTERNS = (
    re.compile(r"\s*\[\d+\]"),  # [6494]
    re.compile(r"\s*\([rv][\d.]+\)", re.IGNORECASE),  # (r2.3), (v1.0)
    re.compile(r"\s*\(rev[\d.]*\)", re.IGNORECASE),  # (rev2)
)


def _sanitize_search_title(title: str) -> str:
    cleaned = title.strip()
    for pattern in _TITLE_NOISE_PATTERNS:
        cleaned = pattern.sub("", cleaned)
    return re.sub(r"\s+", " ", cleaned).strip()


@dataclass(frozen=True)
class OpenLibraryHit:
    work_key: str
    title: str
    authors: list[str]
    cover_id: int | None
    first_publish_year: int | None
    subjects: list[str]
    languages: list[str]
    publishers: list[str]
    edition_key: str | None
    number_of_pages_median: int | None
    match_language: str
    score: float


@dataclass(frozen=True)
class OpenLibraryMetadata:
    match_language: str
    match_score: float
    match_status: str
    openlibrary: dict[str, Any]


def _normalize(text: str) -> str:
    cleaned = re.sub(r"[^\w\s]", " ", _strip_accents(text).lower())
    return re.sub(r"\s+", " ", cleaned).strip()


def _strip_accents(text: str) -> str:
    normalized = unicodedata.normalize("NFKD", text)
    return "".join(ch for ch in normalized if not unicodedata.combining(ch))


def _build_search_params(
    title: str,
    author: str,
    *,
    lang: str | None,
    search_mode: str,
) -> dict[str, str | int]:
    title = title.strip()
    author = author.strip()
    params: dict[str, str | int] = {"limit": 10, "fields": SEARCH_FIELDS}

    if search_mode == "spanish_q":
        q_parts = ["language:spa", title]
        if author:
            q_parts.append(author)
        params["q"] = " ".join(q_parts)
    elif search_mode == "q":
        params["q"] = " ".join(part for part in (title, author) if part)
    elif search_mode == "q_unaccent":
        params["q"] = " ".join(
            part for part in (_strip_accents(title), _strip_accents(author) if author else "") if part
        )
    else:
        params["title"] = title
        if author:
            params["author"] = author

    if lang:
        params["lang"] = lang
    return params


def _title_similarity(a: str, b: str) -> float:
    na, nb = _normalize(a), _normalize(b)
    if not na or not nb:
        return 0.0
    if na in nb or nb in na:
        return 1.0
    return SequenceMatcher(None, na, nb).ratio()


def _author_overlap(user_author: str, ol_authors: list[str]) -> float:
    if not user_author.strip():
        return 0.5 if ol_authors else 0.0
    user_tokens = set(_normalize(user_author).split())
    if not user_tokens:
        return 0.0
    best = 0.0
    for name in ol_authors:
        name_tokens = set(_normalize(name).split())
        if not name_tokens:
            continue
        overlap = len(user_tokens & name_tokens) / len(user_tokens)
        best = max(best, overlap)
        if user_tokens <= name_tokens or name_tokens <= user_tokens:
            best = max(best, 0.95)
    return best


def _score_hit(title: str, author: str, doc: dict[str, Any], *, lang: str) -> float:
    ol_title = doc.get("title") or ""
    ol_authors = doc.get("author_name") or []
    title_score = _title_similarity(title, ol_title)
    author_score = _author_overlap(author, ol_authors)
    combined = (title_score * 0.6) + (author_score * 0.4)
    if doc.get("cover_i"):
        combined += 0.05
    return min(combined, 1.0)


def _parse_hit(doc: dict[str, Any], *, lang: str, score: float) -> OpenLibraryHit:
    edition_keys = doc.get("edition_key") or []
    edition_key = edition_keys[0] if edition_keys else None
    cover_id = doc.get("cover_i")
    return OpenLibraryHit(
        work_key=doc.get("key") or "",
        title=doc.get("title") or "",
        authors=list(doc.get("author_name") or []),
        cover_id=int(cover_id) if cover_id else None,
        first_publish_year=doc.get("first_publish_year"),
        subjects=list(doc.get("subject") or [])[:10],
        languages=list(doc.get("language") or []),
        publishers=list(doc.get("publisher") or [])[:5],
        edition_key=edition_key,
        number_of_pages_median=doc.get("number_of_pages_median"),
        match_language=lang,
        score=score,
    )


def build_cover_url(cover_id: int, size: str = "L") -> str:
    return COVERS_URL.format(cover_id=cover_id, size=size)


def _client() -> httpx.Client:
    read_timeout = settings.OPENLIBRARY_TIMEOUT_SECONDS
    connect_timeout = settings.OPENLIBRARY_CONNECT_TIMEOUT_SECONDS
    return httpx.Client(
        timeout=httpx.Timeout(
            connect=connect_timeout,
            read=read_timeout,
            write=read_timeout,
            pool=connect_timeout,
        ),
        headers={"User-Agent": settings.OPENLIBRARY_USER_AGENT},
        follow_redirects=True,
    )


def search_works(
    title: str,
    author: str,
    *,
    lang: str | None = None,
    search_mode: str = "title",
    client: httpx.Client | None = None,
) -> list[OpenLibraryHit]:
    if not title.strip():
        return []

    params = _build_search_params(title, author, lang=lang, search_mode=search_mode)

    try:
        if client is not None:
            response = client.get(SEARCH_URL, params=params)
            response.raise_for_status()
            docs = response.json().get("docs") or []
        else:
            with _client() as owned_client:
                response = owned_client.get(SEARCH_URL, params=params)
                response.raise_for_status()
                docs = response.json().get("docs") or []
    except (httpx.HTTPError, ValueError) as exc:
        logger.warning("Open Library search failed: %s", exc)
        return []

    hits: list[OpenLibraryHit] = []
    for doc in docs:
        score = _score_hit(title, author, doc, lang=lang or "")
        if score < LOW_CONFIDENCE:
            continue
        hits.append(_parse_hit(doc, lang=lang or "", score=score))
    hits.sort(key=lambda h: (h.score, h.cover_id is not None), reverse=True)
    return hits


def pick_best_match(title: str, author: str, hits: list[OpenLibraryHit]) -> OpenLibraryHit | None:
    return hits[0] if hits else None


def download_cover(cover_id: int) -> bytes | None:
    url = build_cover_url(cover_id, size="L")
    try:
        with _client() as client:
            response = client.get(url)
            if response.status_code == 404:
                return None
            response.raise_for_status()
            content_type = response.headers.get("content-type", "")
            if not content_type.startswith("image/"):
                return None
            return response.content
    except httpx.HTTPError as exc:
        logger.warning("Open Library cover download failed for %s: %s", cover_id, exc)
        return None


def _hit_to_openlibrary_dict(hit: OpenLibraryHit) -> dict[str, Any]:
    return {
        "work_key": hit.work_key,
        "edition_key": hit.edition_key,
        "title": hit.title,
        "authors": hit.authors,
        "cover_id": hit.cover_id,
        "cover_url": build_cover_url(hit.cover_id) if hit.cover_id else None,
        "first_publish_year": hit.first_publish_year,
        "subjects": hit.subjects,
        "languages": hit.languages,
        "publishers": hit.publishers,
        "number_of_pages_median": hit.number_of_pages_median,
    }


def fetch_metadata(title: str, author: str) -> OpenLibraryMetadata | None:
    if not settings.OPENLIBRARY_ENABLED:
        return None

    preferred = settings.OPENLIBRARY_PREFERRED_LANG
    fallback = settings.OPENLIBRARY_FALLBACK_LANG
    search_title = _sanitize_search_title(title)

    if not search_title:
        return OpenLibraryMetadata(
            match_language=preferred,
            match_score=0.0,
            match_status="not_found",
            openlibrary={},
        )

    search_plan: list[tuple[str, str | None]] = [
        ("spanish_q", preferred),
        ("title", preferred),
        ("q", None),
        ("q_unaccent", None),
    ]
    if fallback != preferred:
        search_plan.extend([("title", fallback), ("q", fallback)])

    hits: list[OpenLibraryHit] = []
    with _client() as client:
        for search_mode, lang in search_plan:
            hits = search_works(search_title, author, lang=lang, search_mode=search_mode, client=client)
            if hits:
                break

    hit = pick_best_match(title, author, hits)
    if not hit:
        return OpenLibraryMetadata(
            match_language=preferred,
            match_score=0.0,
            match_status="not_found",
            openlibrary={},
        )

    status = "matched" if hit.score >= HIGH_CONFIDENCE else "partial"
    return OpenLibraryMetadata(
        match_language=hit.match_language,
        match_score=hit.score,
        match_status=status,
        openlibrary=_hit_to_openlibrary_dict(hit),
    )