from datetime import datetime, timezone

from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, func
from pydantic import BaseModel
from app.core.database import get_db
from app.core.deps import get_current_user, require_roles
from app.models.maintenance import Asset, AssetCategory, AssetChange
from app.models.user import User

router = APIRouter(prefix="/assets", tags=["资产管理"])


# ── Pydantic Schemas ────────────────────────────────────────────────

class AssetCreate(BaseModel):
    name: str
    code: str | None = None
    category_id: int | None = None
    station_name: str | None = None
    location: str | None = None
    manufacturer: str | None = None
    model: str | None = None
    serial_number: str | None = None
    rated_power: float | None = None
    install_date: str | None = None
    warranty_until: str | None = None
    status: str = "active"
    specs: dict | None = None
    notes: str | None = None


class AssetUpdate(BaseModel):
    name: str | None = None
    code: str | None = None
    category_id: int | None = None
    station_name: str | None = None
    location: str | None = None
    manufacturer: str | None = None
    model: str | None = None
    serial_number: str | None = None
    rated_power: float | None = None
    install_date: str | None = None
    warranty_until: str | None = None
    status: str | None = None
    specs: dict | None = None
    notes: str | None = None


class CategoryCreate(BaseModel):
    name: str
    description: str | None = None
    parent_id: int | None = None


class ChangeCreate(BaseModel):
    asset_id: int
    change_type: str
    description: str | None = None
    changed_by: int | None = None
    change_date: str | None = None


# ── Helpers ─────────────────────────────────────────────────────────

def _asset_to_dict(a: Asset) -> dict:
    return {
        "id": a.id, "name": a.name, "code": a.code,
        "category_id": a.category_id, "station_name": a.station_name,
        "location": a.location, "manufacturer": a.manufacturer,
        "model": a.model, "serial_number": a.serial_number,
        "rated_power": a.rated_power,
        "install_date": str(a.install_date) if a.install_date else None,
        "warranty_until": str(a.warranty_until) if a.warranty_until else None,
        "status": a.status, "specs": a.specs, "notes": a.notes,
        "created_at": str(a.created_at) if a.created_at else None,
        "updated_at": str(a.updated_at) if a.updated_at else None,
    }


def _category_to_dict(c: AssetCategory) -> dict:
    return {
        "id": c.id, "name": c.name, "description": c.description,
        "parent_id": c.parent_id,
        "created_at": str(c.created_at) if c.created_at else None,
    }


def _change_to_dict(ch: AssetChange) -> dict:
    return {
        "id": ch.id, "asset_id": ch.asset_id, "change_type": ch.change_type,
        "description": ch.description, "changed_by": ch.changed_by,
        "change_date": str(ch.change_date) if ch.change_date else None,
        "created_at": str(ch.created_at) if ch.created_at else None,
    }


# ── Asset Categories ───────────────────────────────────────────────

@router.get("/categories")
async def list_categories(
    db: AsyncSession = Depends(get_db),
    user: User = Depends(get_current_user),
):
    result = await db.execute(select(AssetCategory).order_by(AssetCategory.id))
    return [_category_to_dict(c) for c in result.scalars().all()]


@router.post("/categories")
async def create_category(
    data: CategoryCreate,
    db: AsyncSession = Depends(get_db),
    user: User = Depends(require_roles("admin", "energy_manager")),
):
    cat = AssetCategory(**data.model_dump())
    db.add(cat)
    await db.flush()
    return _category_to_dict(cat)


# ── Asset Statistics ───────────────────────────────────────────────

@router.get("/stats")
async def asset_stats(
    db: AsyncSession = Depends(get_db),
    user: User = Depends(get_current_user),
):
    # Count by status
    status_q = select(Asset.status, func.count()).group_by(Asset.status)
    status_result = await db.execute(status_q)
    by_status = {row[0]: row[1] for row in status_result.all()}

    # Count by category
    cat_q = select(Asset.category_id, func.count()).group_by(Asset.category_id)
    cat_result = await db.execute(cat_q)
    by_category = {str(row[0]): row[1] for row in cat_result.all()}

    total = sum(by_status.values())

    return {
        "total": total,
        "by_status": by_status,
        "by_category": by_category,
    }


# ── Asset Change Records ──────────────────────────────────────────

@router.get("/changes")
async def list_changes(
    asset_id: int | None = None,
    change_type: str | None = None,
    page: int = Query(1, ge=1),
    page_size: int = Query(20, ge=1, le=100),
    db: AsyncSession = Depends(get_db),
    user: User = Depends(get_current_user),
):
    query = select(AssetChange)
    if asset_id:
        query = query.where(AssetChange.asset_id == asset_id)
    if change_type:
        query = query.where(AssetChange.change_type == change_type)

    count_q = select(func.count()).select_from(query.subquery())
    total = (await db.execute(count_q)).scalar()

    query = query.order_by(AssetChange.id.desc()).offset((page - 1) * page_size).limit(page_size)
    result = await db.execute(query)
    return {
        "total": total,
        "items": [_change_to_dict(ch) for ch in result.scalars().all()],
    }


@router.post("/changes")
async def create_change(
    data: ChangeCreate,
    db: AsyncSession = Depends(get_db),
    user: User = Depends(get_current_user),
):
    ch = AssetChange(**data.model_dump(exclude={"change_date"}))
    if data.change_date:
        ch.change_date = datetime.fromisoformat(data.change_date)
    else:
        ch.change_date = datetime.now(timezone.utc)
    if not ch.changed_by:
        ch.changed_by = user.id
    db.add(ch)
    await db.flush()
    return _change_to_dict(ch)


# ── Assets CRUD ────────────────────────────────────────────────────

@router.get("")
async def list_assets(
    station_name: str | None = None,
    category_id: int | None = None,
    status: str | None = None,
    search: str | None = None,
    page: int = Query(1, ge=1),
    page_size: int = Query(20, ge=1, le=100),
    db: AsyncSession = Depends(get_db),
    user: User = Depends(get_current_user),
):
    query = select(Asset)
    if station_name:
        query = query.where(Asset.station_name == station_name)
    if category_id:
        query = query.where(Asset.category_id == category_id)
    if status:
        query = query.where(Asset.status == status)
    if search:
        query = query.where(Asset.name.ilike(f"%{search}%"))

    count_q = select(func.count()).select_from(query.subquery())
    total = (await db.execute(count_q)).scalar()

    query = query.order_by(Asset.id.desc()).offset((page - 1) * page_size).limit(page_size)
    result = await db.execute(query)
    return {
        "total": total,
        "items": [_asset_to_dict(a) for a in result.scalars().all()],
    }


@router.get("/{asset_id}")
async def get_asset(
    asset_id: int,
    db: AsyncSession = Depends(get_db),
    user: User = Depends(get_current_user),
):
    result = await db.execute(select(Asset).where(Asset.id == asset_id))
    asset = result.scalar_one_or_none()
    if not asset:
        raise HTTPException(status_code=404, detail="资产不存在")
    return _asset_to_dict(asset)


@router.post("")
async def create_asset(
    data: AssetCreate,
    db: AsyncSession = Depends(get_db),
    user: User = Depends(require_roles("admin", "energy_manager")),
):
    asset = Asset(**data.model_dump(exclude={"install_date", "warranty_until"}))
    if data.install_date:
        asset.install_date = datetime.fromisoformat(data.install_date)
    if data.warranty_until:
        asset.warranty_until = datetime.fromisoformat(data.warranty_until)
    db.add(asset)
    await db.flush()
    return _asset_to_dict(asset)


@router.put("/{asset_id}")
async def update_asset(
    asset_id: int,
    data: AssetUpdate,
    db: AsyncSession = Depends(get_db),
    user: User = Depends(require_roles("admin", "energy_manager")),
):
    result = await db.execute(select(Asset).where(Asset.id == asset_id))
    asset = result.scalar_one_or_none()
    if not asset:
        raise HTTPException(status_code=404, detail="资产不存在")
    for k, v in data.model_dump(exclude_unset=True, exclude={"install_date", "warranty_until"}).items():
        setattr(asset, k, v)
    if data.install_date:
        asset.install_date = datetime.fromisoformat(data.install_date)
    if data.warranty_until:
        asset.warranty_until = datetime.fromisoformat(data.warranty_until)
    return _asset_to_dict(asset)


@router.delete("/{asset_id}")
async def delete_asset(
    asset_id: int,
    db: AsyncSession = Depends(get_db),
    user: User = Depends(require_roles("admin", "energy_manager")),
):
    result = await db.execute(select(Asset).where(Asset.id == asset_id))
    asset = result.scalar_one_or_none()
    if not asset:
        raise HTTPException(status_code=404, detail="资产不存在")
    asset.status = "inactive"
    return {"message": "已删除"}