from datetime import datetime, timedelta, timezone
from typing import Optional

from fastapi import APIRouter, Depends, HTTPException, Query
from pydantic import BaseModel
from sqlalchemy import select, desc
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.config import get_settings
from app.core.database import get_db
from app.core.deps import get_current_user
from app.models.meter import MeterReading
from app.models.user import User

router = APIRouter(prefix="/meters", tags=["电表管理"])

settings = get_settings()
_customer_config = settings.load_customer_config()


# --------------- Pydantic schemas ---------------

class MeterInfo(BaseModel):
    id: int
    name: str
    meter_no: str | None = None
    modbus_addr: int | None = None


class MeterReadingResponse(BaseModel):
    time: datetime
    meter_id: int
    meter_name: str | None = None
    forward_active_energy: float | None = None
    reverse_active_energy: float | None = None
    active_power: float | None = None
    reactive_power: float | None = None
    power_factor: float | None = None
    voltage_a: float | None = None
    voltage_b: float | None = None
    voltage_c: float | None = None
    current_a: float | None = None
    current_b: float | None = None
    current_c: float | None = None


class MeterLatestResponse(BaseModel):
    meter: MeterInfo
    latest: MeterReadingResponse | None = None


class MeterOverviewItem(BaseModel):
    meter: MeterInfo
    latest: MeterReadingResponse | None = None


class MeterOverviewResponse(BaseModel):
    meters: list[MeterOverviewItem]
    total_forward_energy: float
    total_reverse_energy: float
    total_active_power: float


class MeterListResponse(BaseModel):
    items: list[MeterInfo]
    total: int


# --------------- Helpers ---------------

def _get_meter_configs() -> list[dict]:
    """Load meter list from customer config.yaml."""
    return _customer_config.get("meters", [])


def _meter_config_to_info(cfg: dict) -> MeterInfo:
    return MeterInfo(
        id=cfg["id"],
        name=cfg.get("name", f"Meter-{cfg['id']}"),
        meter_no=cfg.get("meter_no"),
        modbus_addr=cfg.get("modbus_addr"),
    )


def _reading_to_response(r: MeterReading) -> MeterReadingResponse:
    return MeterReadingResponse(
        time=r.time,
        meter_id=r.meter_id,
        meter_name=r.meter_name,
        forward_active_energy=r.forward_active_energy,
        reverse_active_energy=r.reverse_active_energy,
        active_power=r.active_power,
        reactive_power=r.reactive_power,
        power_factor=r.power_factor,
        voltage_a=r.voltage_a,
        voltage_b=r.voltage_b,
        voltage_c=r.voltage_c,
        current_a=r.current_a,
        current_b=r.current_b,
        current_c=r.current_c,
    )


# --------------- Endpoints ---------------

@router.get("", response_model=MeterListResponse)
async def list_meters(
    user: User = Depends(get_current_user),
):
    """列出所有已配置的电表"""
    configs = _get_meter_configs()
    items = [_meter_config_to_info(c) for c in configs]
    return MeterListResponse(items=items, total=len(items))


@router.get("/overview", response_model=MeterOverviewResponse)
async def meter_overview(
    db: AsyncSession = Depends(get_db),
    user: User = Depends(get_current_user),
):
    """仪表盘概览 - 所有电表最新值及汇总"""
    configs = _get_meter_configs()
    overview_items: list[MeterOverviewItem] = []
    total_forward = 0.0
    total_reverse = 0.0
    total_power = 0.0

    for cfg in configs:
        info = _meter_config_to_info(cfg)
        result = await db.execute(
            select(MeterReading)
            .where(MeterReading.meter_id == cfg["id"])
            .order_by(desc(MeterReading.time))
            .limit(1)
        )
        reading = result.scalar_one_or_none()
        latest = _reading_to_response(reading) if reading else None
        if reading:
            total_forward += reading.forward_active_energy or 0
            total_reverse += reading.reverse_active_energy or 0
            total_power += reading.active_power or 0
        overview_items.append(MeterOverviewItem(meter=info, latest=latest))

    return MeterOverviewResponse(
        meters=overview_items,
        total_forward_energy=total_forward,
        total_reverse_energy=total_reverse,
        total_active_power=total_power,
    )


@router.get("/{meter_id}/latest", response_model=MeterLatestResponse)
async def get_meter_latest(
    meter_id: int,
    db: AsyncSession = Depends(get_db),
    user: User = Depends(get_current_user),
):
    """获取指定电表的最新读数"""
    configs = _get_meter_configs()
    cfg = next((c for c in configs if c["id"] == meter_id), None)
    if not cfg:
        raise HTTPException(status_code=404, detail="电表不存在")

    result = await db.execute(
        select(MeterReading)
        .where(MeterReading.meter_id == meter_id)
        .order_by(desc(MeterReading.time))
        .limit(1)
    )
    reading = result.scalar_one_or_none()
    return MeterLatestResponse(
        meter=_meter_config_to_info(cfg),
        latest=_reading_to_response(reading) if reading else None,
    )


@router.get("/{meter_id}/readings", response_model=list[MeterReadingResponse])
async def get_meter_readings(
    meter_id: int,
    start: Optional[datetime] = Query(None, description="开始时间 ISO8601"),
    end: Optional[datetime] = Query(None, description="结束时间 ISO8601"),
    limit: int = Query(100, ge=1, le=10000, description="返回条数上限"),
    db: AsyncSession = Depends(get_db),
    user: User = Depends(get_current_user),
):
    """查询历史读数 (时间范围 + limit)"""
    configs = _get_meter_configs()
    cfg = next((c for c in configs if c["id"] == meter_id), None)
    if not cfg:
        raise HTTPException(status_code=404, detail="电表不存在")

    query = select(MeterReading).where(MeterReading.meter_id == meter_id)
    if start:
        query = query.where(MeterReading.time >= start)
    if end:
        query = query.where(MeterReading.time <= end)
    query = query.order_by(desc(MeterReading.time)).limit(limit)

    result = await db.execute(query)
    readings = result.scalars().all()
    return [_reading_to_response(r) for r in readings]