from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select
from datetime import datetime
from pydantic import BaseModel
from app.core.database import get_db
from app.models.models import User, Debt
from app.schemas.schemas import LoanCreate, LoanResponse
from app.core.deps import get_current_user

router = APIRouter(prefix="/loans", tags=["借款管理"])

METHOD_MAP = {"e": "equal_installment", "p": "interest_first", "i": "lump_sum"}
METHOD_REV = {"equal_installment": "e", "interest_first": "p", "lump_sum": "i"}


class PaidUpdate(BaseModel):
    paid: list[int]


def _debt_to_loan(d: Debt, owner_name: str = "") -> LoanResponse:
    return LoanResponse(
        id=d.id,
        name=d.creditor_name,
        date=d.borrow_date.strftime("%Y-%m-%d") if d.borrow_date else "",
        amount=d.amount / 100,
        rate=d.interest_rate,
        periods=d.period_count,
        method=METHOD_REV.get(d.repayment_method, "e"),
        purpose=d.purpose or "",
        schedule=d.schedule_data or [],
        paid=d.paid_periods or [],
        user_id=d.user_id,
        owner_name=owner_name,
    )


async def _get_visible_user_ids(user: User, db: AsyncSession) -> list[int]:
    if user.role == "admin":
        result = await db.execute(select(User.id))
        return [r[0] for r in result.all()]
    if user.group_id:
        result = await db.execute(select(User.id).where(User.group_id == user.group_id))
        ids = [r[0] for r in result.all()]
        if user.id not in ids:
            ids.append(user.id)
        return ids
    return [user.id]


@router.get("", response_model=list[LoanResponse])
async def list_loans(
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    visible_ids = await _get_visible_user_ids(user, db)
    result = await db.execute(select(Debt).where(Debt.user_id.in_(visible_ids)).order_by(Debt.created_at.desc()))
    debts = result.scalars().all()
    users_result = await db.execute(select(User.id, User.nickname))
    users_map = {uid: (nick or "") for uid, nick in users_result.all()}
    return [_debt_to_loan(d, users_map.get(d.user_id, "")) for d in debts]


@router.post("", response_model=LoanResponse, status_code=201)
async def create_loan(
    req: LoanCreate,
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    debt = Debt(
        user_id=user.id,
        creditor_name=req.name,
        amount=int(req.amount * 100),
        borrow_date=datetime.strptime(req.date, "%Y-%m-%d"),
        interest_rate=req.rate,
        rate_type="annual",
        repayment_method=METHOD_MAP.get(req.method, "equal_installment"),
        period_count=req.periods,
        period_unit="month",
        purpose=req.purpose,
        schedule_data=req.schedule,
        paid_periods=req.paid,
    )
    db.add(debt)
    await db.commit()
    await db.refresh(debt)
    return _debt_to_loan(debt, user.nickname or "")


@router.put("/{loan_id}", response_model=LoanResponse)
async def update_loan(
    loan_id: int,
    req: LoanCreate,
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    result = await db.execute(select(Debt).where(Debt.id == loan_id))
    debt = result.scalar_one_or_none()
    if not debt:
        raise HTTPException(status_code=404, detail="借款不存在")
    if debt.user_id != user.id and user.role != "admin":
        raise HTTPException(status_code=403, detail="无权修改")

    debt.creditor_name = req.name
    debt.amount = int(req.amount * 100)
    debt.borrow_date = datetime.strptime(req.date, "%Y-%m-%d")
    debt.interest_rate = req.rate
    debt.repayment_method = METHOD_MAP.get(req.method, "equal_installment")
    debt.period_count = req.periods
    debt.purpose = req.purpose
    debt.schedule_data = req.schedule
    debt.paid_periods = req.paid

    await db.commit()
    await db.refresh(debt)
    return _debt_to_loan(debt, user.nickname or "")


@router.delete("/{loan_id}")
async def delete_loan(
    loan_id: int,
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    result = await db.execute(select(Debt).where(Debt.id == loan_id))
    debt = result.scalar_one_or_none()
    if not debt:
        raise HTTPException(status_code=404, detail="借款不存在")
    if debt.user_id != user.id and user.role != "admin":
        raise HTTPException(status_code=403, detail="无权删除")
    await db.delete(debt)
    await db.commit()
    return {"message": "已删除"}


@router.patch("/{loan_id}/toggle-paid")
async def toggle_paid(
    loan_id: int,
    req: PaidUpdate,
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    result = await db.execute(select(Debt).where(Debt.id == loan_id))
    debt = result.scalar_one_or_none()
    if not debt:
        raise HTTPException(status_code=404, detail="借款不存在")
    if debt.user_id != user.id:
        raise HTTPException(status_code=403, detail="只能标记自己的还款")

    debt.paid_periods = sorted(req.paid)
    await db.commit()
    return {"paid": debt.paid_periods}