"""Start processing (background) and poll status/progress."""
from __future__ import annotations

from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException
from sqlalchemy.orm import Session as OrmSession

from ...db import models
from ...services.jobs import run_processing
from ..deps import db_dep, get_session_or_404, session_dict

router = APIRouter(prefix="/api/sessions", tags=["processing"])


@router.post("/{session_id}/process")
def start_processing(session_id: int, background: BackgroundTasks,
                     db: OrmSession = Depends(db_dep)) -> dict:
    s = get_session_or_404(session_id, db)
    if s.month_end_date is None:
        raise HTTPException(400, "Set the month-end date before processing.")
    valid_files = db.query(models.SessionFile).filter(
        models.SessionFile.session_id == session_id).all()
    if not valid_files:
        raise HTTPException(400, "Upload at least one file before processing.")
    if any(f.status == "invalid" for f in valid_files):
        raise HTTPException(400, "One or more files failed validation; fix them before processing.")
    if s.status == "processing":
        raise HTTPException(409, "Already processing.")
    s.status = "processing"
    s.progress_stage = "Queued"
    s.progress_pct = 0.0
    s.error = ""
    db.commit()
    background.add_task(run_processing, session_id)
    return {"started": True, "session_id": session_id}


@router.get("/{session_id}/status")
def status(session_id: int, db: OrmSession = Depends(db_dep)) -> dict:
    s = get_session_or_404(session_id, db)
    return {
        "status": s.status, "stage": s.progress_stage, "pct": s.progress_pct,
        "rows_done": s.progress_rows_done, "rows_total": s.progress_rows_total,
        "eta_seconds": s.eta_seconds, "error": s.error, "session": session_dict(s),
    }