from typing import Any
from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy import select
from sqlalchemy.orm import Session
from datetime import datetime, timezone
import json

from app.db import get_db
from app.models.document import Document
from app.models.annotation_state import AnnotationState
from app.auth.dependencies import get_current_user, verify_csrf
from app.schemas.annotations import AnnotationStateResponse, AnnotationStateUpdateRequest, AnnotationStateUpdateResponse

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

def _now_iso() -> str:
    return datetime.now(timezone.utc).isoformat()

@router.get("/{document_id}/annotations", response_model=AnnotationStateResponse)
async def get_annotations(
    document_id: str,
    db: Session = Depends(get_db),
    user_id: Any = Depends(get_current_user)
):
    doc = db.scalar(select(Document).where(Document.id == document_id, Document.deleted_at.is_(None)))
    if not doc:
        raise HTTPException(status_code=404, detail="Document not found")
        
    state = db.scalar(select(AnnotationState).where(AnnotationState.document_id == document_id))
    
    if not state:
        return AnnotationStateResponse(data=[], updatedAt=datetime.now(timezone.utc))
        
    try:
        data = json.loads(state.data)
    except json.JSONDecodeError:
        data = []
        
    return AnnotationStateResponse(
        data=data,
        updatedAt=datetime.fromisoformat(state.updated_at)
    )

@router.put("/{document_id}/annotations", response_model=AnnotationStateUpdateResponse, dependencies=[Depends(verify_csrf)])
async def update_annotations(
    document_id: str,
    request: AnnotationStateUpdateRequest,
    db: Session = Depends(get_db),
    user_id: Any = Depends(get_current_user)
):
    doc = db.scalar(select(Document).where(Document.id == document_id, Document.deleted_at.is_(None)))
    if not doc:
        raise HTTPException(status_code=404, detail="Document not found")
        
    state = db.scalar(select(AnnotationState).where(AnnotationState.document_id == document_id))
    
    # Check for stale tab
    if state and request.baseUpdatedAt:
        current_updated_at = datetime.fromisoformat(state.updated_at).replace(tzinfo=timezone.utc)
        request_updated_at = request.baseUpdatedAt.replace(tzinfo=timezone.utc)
        # Allow a small grace period for timezone/parsing discrepancies
        if abs((current_updated_at - request_updated_at).total_seconds()) > 1.0:
            raise HTTPException(
                status_code=409, 
                detail=f"Conflict: annotations have been modified since {request.baseUpdatedAt}"
            )
            
    now = _now_iso()
    
    import json
    
    # serialize request.data list of models to json string
    data_json = json.dumps([a.model_dump(mode="json", by_alias=True) for a in request.data])

    if not state:
        state = AnnotationState(
            document_id=document_id,
            data=data_json,
            updated_at=now
        )
        db.add(state)
    else:
        state.data = data_json
        state.updated_at = now
        
    # Bump document updated_at
    doc.updated_at = now
        
    db.commit()
    
    return AnnotationStateUpdateResponse(updatedAt=datetime.fromisoformat(now))