from datetime import datetime, timezone

from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.orm import Session

from ..database import get_db
from ..dependencies import get_current_user
from ..models import Annotation, PDF, User
from ..schemas import AnnotationIn, AnnotationOut

router = APIRouter(prefix="/annotations", tags=["annotations"])


def _verify_pdf_ownership(db: Session, pdf_id: int, user_id: int) -> PDF:
    pdf = db.get(PDF, pdf_id)
    if not pdf or pdf.user_id != user_id:
        raise HTTPException(status_code=404, detail="PDF not found.")
    return pdf


# ── GET /api/annotations/{pdf_id}/{page_number} ───────────────────────────────

@router.get("/{pdf_id}/{page_number}", response_model=AnnotationOut)
def get_annotation(
    pdf_id: int,
    page_number: int,
    current_user: User = Depends(get_current_user),
    db: Session = Depends(get_db),
):
    _verify_pdf_ownership(db, pdf_id, current_user.id)

    ann = (
        db.query(Annotation)
        .filter(
            Annotation.pdf_id == pdf_id,
            Annotation.user_id == current_user.id,
            Annotation.page_number == page_number,
        )
        .first()
    )

    # Return empty canvas if no annotation exists yet — not an error
    if ann is None:
        return AnnotationOut(
            id=0,
            pdf_id=pdf_id,
            page_number=page_number,
            canvas_data={},
            updated_at=datetime.now(timezone.utc),
        )

    return ann


# ── PUT /api/annotations/{pdf_id}/{page_number} ───────────────────────────────

@router.put("/{pdf_id}/{page_number}", response_model=AnnotationOut)
def upsert_annotation(
    pdf_id: int,
    page_number: int,
    body: AnnotationIn,
    current_user: User = Depends(get_current_user),
    db: Session = Depends(get_db),
):
    _verify_pdf_ownership(db, pdf_id, current_user.id)

    ann = (
        db.query(Annotation)
        .filter(
            Annotation.pdf_id == pdf_id,
            Annotation.user_id == current_user.id,
            Annotation.page_number == page_number,
        )
        .first()
    )

    if ann is None:
        ann = Annotation(
            pdf_id=pdf_id,
            user_id=current_user.id,
            page_number=page_number,
            canvas_data=body.canvas_data,
        )
        db.add(ann)
    else:
        ann.canvas_data = body.canvas_data
        ann.updated_at = datetime.now(timezone.utc)

    db.commit()
    db.refresh(ann)
    return ann