from __future__ import annotations

from datetime import datetime
from typing import List, Optional

from fastapi import APIRouter, HTTPException
from fastapi.responses import Response
from pydantic import BaseModel, Field

from app.db import get_pool

router = APIRouter(tags=["discounts"])


async def _bump_domain_version(conn, domain: str) -> None:
    """Upsert domain_version: insert with version=1 for new domains, increment for existing."""
    await conn.execute(
        """
        INSERT INTO domain_version (domain, version, updated_at)
        VALUES ($1, 1, NOW())
        ON CONFLICT (domain) DO UPDATE
            SET version = domain_version.version + 1,
                updated_at = NOW()
        """,
        domain,
    )


class DiscountIn(BaseModel):
    domain: str
    discount: float = Field(..., gt=0, le=1, description="折扣系数，如 0.8 表示八折")
    note: Optional[str] = None


class DiscountOut(BaseModel):
    id: int
    domain: str
    discount: float
    note: Optional[str]
    created_at: datetime
    updated_at: datetime


@router.get("/discounts", response_model=List[DiscountOut])
async def list_discounts() -> List[DiscountOut]:
    pool = get_pool()
    rows = await pool.fetch("SELECT * FROM discounts ORDER BY updated_at DESC")
    return [DiscountOut(**dict(r)) for r in rows]


@router.post("/discounts", response_model=DiscountOut, status_code=201)
async def create_discount(body: DiscountIn) -> DiscountOut:
    pool = get_pool()
    async with pool.acquire() as conn:
        async with conn.transaction():
            row = await conn.fetchrow(
                """
                INSERT INTO discounts (domain, discount, note)
                VALUES ($1, $2, $3)
                ON CONFLICT (domain) DO UPDATE
                    SET discount = EXCLUDED.discount,
                        note = EXCLUDED.note,
                        updated_at = NOW()
                RETURNING *
                """,
                body.domain, body.discount, body.note,
            )
            await _bump_domain_version(conn, body.domain)
    return DiscountOut(**dict(row))


@router.put("/discounts/{discount_id}", response_model=DiscountOut)
async def update_discount(discount_id: int, body: DiscountIn) -> DiscountOut:
    pool = get_pool()
    async with pool.acquire() as conn:
        async with conn.transaction():
            row = await conn.fetchrow(
                """
                UPDATE discounts SET domain=$1, discount=$2, note=$3, updated_at=NOW()
                WHERE id=$4 RETURNING *
                """,
                body.domain, body.discount, body.note, discount_id,
            )
            if not row:
                raise HTTPException(status_code=404, detail="不存在")
            await _bump_domain_version(conn, body.domain)
    return DiscountOut(**dict(row))


@router.delete("/discounts/{discount_id}", status_code=204, response_model=None)
async def delete_discount(discount_id: int) -> Response:
    pool = get_pool()
    async with pool.acquire() as conn:
        async with conn.transaction():
            # 先查出 domain，再删除，再 bump 版本
            existing = await conn.fetchrow("SELECT domain FROM discounts WHERE id=$1", discount_id)
            if not existing:
                raise HTTPException(status_code=404, detail="不存在")
            result = await conn.execute("DELETE FROM discounts WHERE id=$1", discount_id)
            if result == "DELETE 0":
                raise HTTPException(status_code=404, detail="不存在")
            await conn.execute("DELETE FROM domain_version WHERE domain=$1", existing["domain"])
    return Response(status_code=204)