from fastapi import APIRouter, HTTPException, Depends
from sqlalchemy.orm import Session
from app.core.services import RAGService 
from app.api.dependencies import get_db
from app.api import schemas

def create_api_router(rag_service: RAGService) -> APIRouter:
    """
    Creates and returns an APIRouter with all the application's endpoints.
    """
    router = APIRouter()

    @router.get("/", summary="Check Service Status", tags=["General"])
    def read_root():
        return {"status": "AI Model Hub is running!"}

    # --- Session Management Endpoints ---
    
    @router.post("/sessions", response_model=schemas.Session, summary="Create a New Chat Session", tags=["Sessions"])
    def create_session(
        request: schemas.SessionCreate,
        db: Session = Depends(get_db)
    ):
        """
        Starts a new conversation session and returns its details.
        The returned session_id should be used for subsequent chat messages.
        """
        try:
            # Note: You'll need to add a `create_session` method to your RAGService.
            new_session = rag_service.create_session(
                db=db, 
                user_id=request.user_id, 
                model=request.model
            )
            return new_session
        except Exception as e:
            raise HTTPException(status_code=500, detail=f"Failed to create session: {e}")

    @router.post("/sessions/{session_id}/chat", response_model=schemas.ChatResponse, summary="Send a Message in a Session", tags=["Sessions"])
    async def chat_in_session(
        session_id: int,
        request: schemas.ChatRequest, # We can reuse ChatRequest
        db: Session = Depends(get_db)
    ):
        """
        Sends a message within an existing session and gets a contextual response.
        The model used is determined by the session, not the request.
        """
        try:
            # Note: You'll need to update `chat_with_rag` to accept a session_id
            # and use it to retrieve chat history for context.
            response_text, model_used = await rag_service.chat_with_rag(
                db=db,
                session_id=session_id,
                prompt=request.prompt
            )
            return schemas.ChatResponse(answer=response_text, model_used=model_used)
        except Exception as e:
            raise HTTPException(
                status_code=500, 
                detail=f"An error occurred during chat: {e}"
            )

    # --- Document Management Endpoints ---
    # (These endpoints remain unchanged)
    
    @router.post("/documents", response_model=schemas.DocumentResponse, summary="Add a New Document", tags=["Documents"])
    def add_document(doc: schemas.DocumentCreate, db: Session = Depends(get_db)):
        try:
            doc_data = doc.model_dump()
            document_id = rag_service.add_document(db=db, doc_data=doc_data)
            return schemas.DocumentResponse(
                message=f"Document '{doc.title}' added successfully with ID {document_id}"
            )
        except Exception as e:
            raise HTTPException(status_code=500, detail=f"An error occurred: {e}")

    @router.get("/documents", response_model=schemas.DocumentListResponse, summary="List All Documents", tags=["Documents"])
    def get_documents(db: Session = Depends(get_db)):
        try:
            documents_from_db = rag_service.get_all_documents(db=db)
            return {"documents": documents_from_db}
        except Exception as e:
            raise HTTPException(status_code=500, detail=f"An error occurred: {e}")

    @router.delete("/documents/{document_id}", response_model=schemas.DocumentDeleteResponse, summary="Delete a Document", tags=["Documents"])
    def delete_document(document_id: int, db: Session = Depends(get_db)):
        try:
            deleted_id = rag_service.delete_document(db=db, document_id=document_id)
            if deleted_id is None:
                raise HTTPException(status_code=404, detail=f"Document with ID {document_id} not found.")
            
            return schemas.DocumentDeleteResponse(
                message="Document deleted successfully",
                document_id=deleted_id
            )
        except HTTPException:
            raise
        except Exception as e:
            raise HTTPException(status_code=500, detail=f"An error occurred: {e}")

    return router