"""Schedule steps nested under termsheets. step_no auto-numbers (MAX+1)."""
from fastapi import APIRouter, Depends, Query
from sqlalchemy import func, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.db.engine import get_db
from app.models.procurement import Termsheet, TermsheetScheduleStep
from app.schemas.procurement import ScheduleStepCreate, ScheduleStepUpdate
from app.services.expand_service import schedule_step_to_dict
from app.services.quote_service import next_step_no
from app.utils.errors import ConflictError, NotFoundError
from app.utils.pagination import paginate

router = APIRouter(
    prefix="/quotes/{quote_id}/termsheets/{termsheet_id}/schedule-steps",
    tags=["schedule-steps"],
)


async def _termsheet_or_404(db: AsyncSession, quote_id, termsheet_id) -> Termsheet:
    ts = await db.scalar(
        select(Termsheet).where(Termsheet.id == termsheet_id, Termsheet.quote_id == quote_id)
    )
    if ts is None:
        raise NotFoundError("ترم‌شیت یافت نشد")
    return ts


async def _step_or_404(db: AsyncSession, termsheet_id, step_id) -> TermsheetScheduleStep:
    step = await db.scalar(
        select(TermsheetScheduleStep).where(
            TermsheetScheduleStep.id == step_id, TermsheetScheduleStep.termsheet_id == termsheet_id
        )
    )
    if step is None:
        raise NotFoundError("مرحله پرداخت یافت نشد")
    return step


@router.get("")
async def list_schedule_steps(
    quote_id,
    termsheet_id,
    page: int = Query(1, ge=1),
    page_size: int = Query(20, ge=1, le=100),
    db: AsyncSession = Depends(get_db),
):
    await _termsheet_or_404(db, quote_id, termsheet_id)
    stmt = (
        select(TermsheetScheduleStep)
        .where(TermsheetScheduleStep.termsheet_id == termsheet_id)
        .order_by(TermsheetScheduleStep.step_no.asc())
    )
    items, meta = await paginate(stmt, page, page_size, db)
    return {"data": [schedule_step_to_dict(s) for s in items], "meta": meta}


@router.post("", status_code=201)
async def create_schedule_step(
    quote_id, termsheet_id, payload: ScheduleStepCreate, db: AsyncSession = Depends(get_db)
):
    ts = await _termsheet_or_404(db, quote_id, termsheet_id)
    step_no = payload.step_no
    if step_no is None:
        step_no = await next_step_no(db, ts.id)
    duplicate = await db.scalar(
        select(TermsheetScheduleStep.id).where(
            TermsheetScheduleStep.termsheet_id == ts.id, TermsheetScheduleStep.step_no == step_no
        )
    )
    if duplicate is not None:
        raise ConflictError("شماره مرحله تکراری است", field="step_no")
    step = TermsheetScheduleStep(
        termsheet_id=ts.id,
        step_no=step_no,
        due_date=payload.due_date,
        amount=payload.amount,
        note=payload.note,
    )
    db.add(step)
    await db.flush()
    return {"data": schedule_step_to_dict(step)}


@router.patch("/{step_id}")
async def update_schedule_step(
    quote_id, termsheet_id, step_id, payload: ScheduleStepUpdate, db: AsyncSession = Depends(get_db)
):
    step = await _step_or_404(db, termsheet_id, step_id)
    if payload.step_no is not None and payload.step_no != step.step_no:
        duplicate = await db.scalar(
            select(TermsheetScheduleStep.id).where(
                TermsheetScheduleStep.termsheet_id == termsheet_id,
                TermsheetScheduleStep.step_no == payload.step_no,
                TermsheetScheduleStep.id != step_id,
            )
        )
        if duplicate is not None:
            raise ConflictError("شماره مرحله تکراری است", field="step_no")
        step.step_no = payload.step_no
    if payload.due_date is not None:
        step.due_date = payload.due_date
    if payload.amount is not None:
        step.amount = payload.amount
    if payload.note is not None:
        step.note = payload.note
    await db.flush()
    return {"data": schedule_step_to_dict(step)}


@router.delete("/{step_id}")
async def delete_schedule_step(quote_id, termsheet_id, step_id, db: AsyncSession = Depends(get_db)):
    step = await _step_or_404(db, termsheet_id, step_id)
    count = await db.scalar(
        select(func.count()).select_from(TermsheetScheduleStep).where(
            TermsheetScheduleStep.termsheet_id == termsheet_id
        )
    )
    if count <= 1:
        raise ConflictError("آخرین مرحله پرداخت قابل حذف نیست")
    await db.delete(step)
    await db.flush()
    return {"data": {"deleted": True}}