"""Модуль работы с книгами"""
import shutil
from uuid import uuid4

from pydantic import Field
from typing_extensions import Annotated

from sqlalchemy.orm import selectinload, defer

from sqlalchemy import text, case, distinct

from datetime import datetime, timezone
from typing import List

from fastapi import APIRouter, Depends, HTTPException, Path, Query, status, UploadFile, File
from ollama import Client
from sqlmodel import Session, select, col, func

from library_service.auth import RequireStaff
from library_service.settings import get_session, OLLAMA_URL, BOOKS_PREVIEW_DIR
from library_service.models.enums import BookStatus
from library_service.models.db import (
    Author,
    AuthorBookLink,
    Book,
    GenreBookLink,
    Genre,
    BookUserLink,
)
from library_service.models.dto import (
    AuthorRead,
    BookCreate,
    BookList,
    BookRead,
    BookUpdate,
    GenreRead,
)
from library_service.models.dto.misc import (
    BookWithAuthorsAndGenres,
    BookFilteredList,
)


router = APIRouter(prefix="/books", tags=["books"])
ollama_client = Client(host=OLLAMA_URL)


def close_active_loan(session: Session, book_id: int) -> None:
    """Закрывает активную выдачу книги при изменении статуса"""
    active_loan = session.exec(
        select(BookUserLink)
        .where(BookUserLink.book_id == book_id) # ty: ignore
        .where(BookUserLink.returned_at == None) # ty: ignore
    ).first() # ty: ignore

    if active_loan:
        active_loan.returned_at = datetime.now(timezone.utc)
        session.add(active_loan)


from sqlalchemy import select, func, distinct, case, exists
from sqlalchemy.orm import selectinload


@router.get("/filter", response_model=BookFilteredList)
def filter_books(
    session: Session = Depends(get_session),
    q: str | None = Query(None, max_length=50, description="Поиск"),
    min_page_count: int | None = Query(None, ge=0),
    max_page_count: int | None = Query(None, ge=0),
    author_ids: List[Annotated[int, Field(gt=0)]] | None = Query(None),
    genre_ids: List[Annotated[int, Field(gt=0)]] | None = Query(None),
    page: int = Query(1, gt=0),
    size: int = Query(20, gt=0, le=100),
):
    statement = select(Book).options(
        selectinload(Book.authors), selectinload(Book.genres), defer(Book.embedding) # ty: ignore
    )

    if min_page_count:
        statement = statement.where(Book.page_count >= min_page_count) # ty: ignore
    if max_page_count:
        statement = statement.where(Book.page_count <= max_page_count) # ty: ignore

    if author_ids:
        statement = statement.where(
            exists().where(
                AuthorBookLink.book_id == Book.id, # ty: ignore
                AuthorBookLink.author_id.in_(author_ids), # ty: ignore
            )
        )

    if genre_ids:
        for genre_id in genre_ids:
            statement = statement.where(
                exists().where(
                    GenreBookLink.book_id == Book.id, GenreBookLink.genre_id == genre_id # ty: ignore
                )
            )

    count_statement = select(func.count()).select_from(statement.subquery())
    total = session.scalar(count_statement)

    if q:
        emb = ollama_client.embeddings(model="mxbai-embed-large", prompt=q)["embedding"]
        distance_col = Book.embedding.cosine_distance(emb) # ty: ignore
        statement = statement.where(Book.embedding.is_not(None)) # ty: ignore

        keyword_match = case((Book.title.ilike(f"%{q}%"), 0), else_=1) # ty: ignore
        statement = statement.order_by(keyword_match, distance_col)
    else:
        statement = statement.order_by(Book.id) # ty: ignore

    offset = (page - 1) * size
    statement = statement.offset(offset).limit(size)
    results = session.scalars(statement).unique().all()

    return BookFilteredList(books=results, total=total)


@router.post(
    "/",
    response_model=BookRead,
    summary="Создать книгу",
    description="Добавляет книгу в систему",
)
def create_book(
    book: BookCreate,
    current_user: RequireStaff,
    session: Session = Depends(get_session),
):
    """Создает новую книгу в системе"""
    full_text = book.title + " " + book.description
    emb = ollama_client.embeddings(model="mxbai-embed-large", prompt=full_text)
    db_book = Book(**book.model_dump(), embedding=emb["embedding"])

    session.add(db_book)
    session.commit()
    session.refresh(db_book)

    book_data = db_book.model_dump(exclude={"embedding", "preview_id"})
    if db_book.preview_id:
        book_data["preview_url"] = f"/static/books/{db_book.preview_id}.png"

    return BookRead(**book_data)


@router.get(
    "/",
    response_model=BookList,
    summary="Получить список книг",
    description="Возвращает список всех книг в системе",
)
def read_books(session: Session = Depends(get_session)):
    """Возвращает список всех книг"""
    books = session.exec(select(Book)).all() # ty: ignore

    books_data = []
    for book in books:
        book_data = book.model_dump(exclude={"embedding", "preview_id"})
        if book.preview_id:
            book_data["preview_url"] = f"/static/books/{book.preview_id}.png"
        books_data.append(book_data)

    return BookList(
        books=[BookRead(**book_data) for book_data in books_data],
        total=len(books),
    )


@router.get(
    "/{book_id}",
    response_model=BookWithAuthorsAndGenres,
    summary="Получить информацию о книге",
    description="Возвращает информацию о книге, её авторах и жанрах",
)
def get_book(
    book_id: int = Path(..., description="ID книги (целое число, > 0)", gt=0),
    session: Session = Depends(get_session),
):
    """Возвращает информацию о книге с авторами и жанрами"""
    book = session.get(Book, book_id)
    if not book:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND, detail="Book not found"
        )

    authors = session.scalars(
        select(Author).join(AuthorBookLink).where(AuthorBookLink.book_id == book_id) # ty: ignore
    ).all()

    author_reads = [AuthorRead(**author.model_dump()) for author in authors]

    genres = session.scalars(
        select(Genre).join(GenreBookLink).where(GenreBookLink.book_id == book_id) # ty: ignore
    ).all()

    genre_reads = [GenreRead(**genre.model_dump()) for genre in genres]

    book_data = book.model_dump(exclude={"embedding", "preview_id"})
    if book.preview_id:
        book_data["preview_url"] = f"/static/books/{book.preview_id}.png"
    book_data["authors"] = author_reads
    book_data["genres"] = genre_reads

    return BookWithAuthorsAndGenres(**book_data)


@router.put(
    "/{book_id}",
    response_model=BookRead,
    summary="Обновить информацию о книге",
    description="Обновляет информацию о книге в системе",
)
def update_book(
    current_user: RequireStaff,
    book_update: BookUpdate,
    book_id: int = Path(..., gt=0),
    session: Session = Depends(get_session),
):
    """Обновляет информацию о книге"""
    db_book = session.get(Book, book_id)
    if not db_book:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND, detail="Book not found"
        )

    if book_update.status is not None:
        if book_update.status == BookStatus.BORROWED:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Статус 'borrowed' устанавливается только через выдачу книги",
            )

        if db_book.status == BookStatus.BORROWED:
            close_active_loan(session, book_id)

        db_book.status = book_update.status

    if book_update.title is not None or book_update.description is not None:
        if book_update.title is not None:
            db_book.title = book_update.title
        if book_update.description is not None:
            db_book.description = book_update.description

        full_text = (
            (book_update.title or db_book.title)
            + " "
            + (book_update.description or db_book.description)
        )
        emb = ollama_client.embeddings(model="mxbai-embed-large", prompt=full_text)
        db_book.embedding = emb["embedding"]

    if book_update.page_count is not None:
        db_book.page_count = book_update.page_count

    session.add(db_book)
    session.commit()
    session.refresh(db_book)

    book_data = db_book.model_dump(exclude={"embedding", "preview_id"})
    if db_book.preview_id:
        book_data["preview_url"] = f"/static/books/{db_book.preview_id}.png"

    return BookRead(**book_data)


@router.delete(
    "/{book_id}",
    response_model=BookRead,
    summary="Удалить книгу",
    description="Удаляет книгу их системы",
)
def delete_book(
    current_user: RequireStaff,
    book_id: int = Path(..., description="ID книги (целое число, > 0)", gt=0),
    session: Session = Depends(get_session),
):
    """Удаляет книгу из системы"""
    book = session.get(Book, book_id)
    if not book:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND, detail="Book not found"
        )
    book_read = BookRead(
        id=(book.id or 0),
        title=book.title,
        description=book.description,
        page_count=book.page_count,
        status=book.status,
    )
    session.delete(book)
    session.commit()
    return book_read

@router.post("/{book_id}/preview")
async def upload_book_preview(
    current_user: RequireStaff,
    file: UploadFile = File(...),
    book_id: int = Path(..., gt=0),
    session: Session = Depends(get_session)
):
    if not file.content_type == "image/png":
        raise HTTPException(status.HTTP_415_UNSUPPORTED_MEDIA_TYPE, "PNG required")

    if (file.size or 0) > 10 * 1024 * 1024:
        raise HTTPException(status.HTTP_413_REQUEST_ENTITY_TOO_LARGE, "File larger than 10 MB")

    file_uuid= uuid4()
    filename = f"{file_uuid}.png"
    file_path = BOOKS_PREVIEW_DIR / filename

    with open(file_path, "wb") as f:
        shutil.copyfileobj(file.file, f)

    book = session.get(Book, book_id)
    if not book:
        file_path.unlink()
        raise HTTPException(status.HTTP_404_NOT_FOUND, "Book not found")

    if book.preview_id:
        old_path = BOOKS_PREVIEW_DIR / f"{book.preview_id}.png"
        if old_path.exists():
            old_path.unlink()

    book.preview_id = file_uuid
    session.add(book)
    session.commit()

    return {"preview_url": f"/static/books/{filename}"}


@router.delete("/{book_id}/preview")
async def remove_book_preview(
    current_user: RequireStaff,
    book_id: int = Path(..., gt=0),
    session: Session = Depends(get_session)
):
    book = session.get(Book, book_id)
    if not book:
        raise HTTPException(status.HTTP_404_NOT_FOUND, "Book not found")

    if book.preview_id:
        old_path = BOOKS_PREVIEW_DIR / f"{book.preview_id}.png"
        if old_path.exists():
            old_path.unlink()

    book.preview_id = None
    session.add(book)
    session.commit()

    return {"preview_url": None}