from __future__ import annotations

import logging
from datetime import date, datetime
from decimal import Decimal, InvalidOperation
from typing import Any, Dict, List, Tuple

from django.contrib.auth import get_user_model
from django.db import transaction

from basic_info import models as basic_info_models
from stock import models as stock_models
from stock.services import StockFlowService
from basic_info.services import MerchantSettingService

from . import models
from .tasks import create_purchase_order_stock_entries


logger = logging.getLogger(__name__)


def _normalize_order_date(value) -> date:
    if isinstance(value, date):
        return value
    if isinstance(value, datetime):
        return value.date()
    if isinstance(value, str):
        try:
            return date.fromisoformat(value)
        except ValueError as exc:
            raise ValueError('order_date 格式不正确，应为 YYYY-MM-DD') from exc
    raise ValueError('order_date 格式不正确')


def create_purchase_order(
    *,
    merchant: basic_info_models.Merchant,
    supplier: basic_info_models.Supplier,
    order_date,
    warehouse: basic_info_models.WareHouse,
    operator: basic_info_models.Employee,
    items: List[Dict[str, Any]],
    remarks: str | None = '',
    created_by=None,
) -> models.PurchaseOrder:
    """
    创建采购订单并触发异步创建入库单任务。

    Args:
        merchant: 采购单所属商户
        supplier: 供应商
        order_date: 订单日期 (date)
        warehouse: 入库仓库实例
        operator: 经办人
        items: 产品明细，字段会根据仓库模式校验
        remarks: 备注
        created_by: 创建者用户（可选，用于 stock 记录中的 created_by）
    """
    if not items:
        raise ValueError('items 不能为空')

    normalized_date = _normalize_order_date(order_date)
    purchase_items, stock_flow_items = _normalize_purchase_items(
        merchant=merchant,
        warehouse=warehouse,
        items=items,
    )

    with transaction.atomic():
        purchase_order = models.PurchaseOrder.objects.create(
            merchant=merchant,
            supplier=supplier,
            purchase_date=normalized_date,
            operator=operator,
            warehouse=warehouse,
            remarks=remarks,
        )
        bulk_objects = [
            models.PurchaseOrderItem(
                purchase_order=purchase_order,
                product=item_data['product'],
                price=item_data['price'],
                color=item_data.get('color'),
                quantity=item_data['quantity'],
                unit=item_data['unit'],
                spec=item_data.get('spec'),
                empty_diff_percent=item_data['empty_diff_percent'],
                quantity_of_rolls=item_data.get('quantity_of_rolls'),
                num_of_rolls=item_data['num_of_rolls'],
                batch_number=item_data.get('batch_number'),
                remarks=item_data.get('remarks'),
            )
            for item_data in purchase_items
        ]
        models.PurchaseOrderItem.objects.bulk_create(bulk_objects)

    purchase_order.refresh_from_db()
    return purchase_order


def review_purchase_order(
    *,
    purchase_order: models.PurchaseOrder | None = None,
    purchase_order_id: int | None = None,
    target_status: models.PurchaseOrderStatusEnum,
    reviewed_by=None,
) -> models.PurchaseOrder:
    """
    审批或作废采购单。

    当目标状态为 APPROVED 且开启自动入库任务时，将触发入库 Celery 任务；
    当目标状态为 CANCELLED 时，会在更新状态前确认未生成任何出入库单。
    """
    order = _resolve_purchase_order_instance(purchase_order, purchase_order_id)

    if target_status not in {
        models.PurchaseOrderStatusEnum.APPROVED,
        models.PurchaseOrderStatusEnum.CANCELLED,
    }:
        raise ValueError('target_status 只能是 APPROVED 或 CANCELLED')

    if order.status == target_status:
        return order

    if target_status == models.PurchaseOrderStatusEnum.APPROVED:
        if order.status == models.PurchaseOrderStatusEnum.CANCELLED:
            raise ValueError('作废状态的采购单无法再次审批')
        return _approve_purchase_order(order, reviewed_by)

    return _cancel_purchase_order(order)


def _normalize_purchase_items(
    *,
    merchant: basic_info_models.Merchant,
    warehouse: basic_info_models.WareHouse,
    items: List[Dict[str, Any]],
) -> Tuple[List[Dict[str, Any]], List[Dict[str, Any]]]:
    """
    根据仓库模式校验采购明细，并返回
    - purchase_items: 用于创建 PurchaseOrderItem
    - stock_flow_items: 传递给 StockFlowService 的 items 结构
    """
    purchase_items: List[Dict[str, Any]] = []
    stock_flow_items: List[Dict[str, Any]] = []

    warehouse_mode = warehouse.mode

    for index, raw_item in enumerate(items):
        product_id = raw_item.get('product_id')
        if not product_id:
            raise ValueError(f'items[{index}].product_id 不能为空')
        try:
            product = basic_info_models.Product.objects.get(id=product_id, merchant=merchant)
        except basic_info_models.Product.DoesNotExist as exc:
            raise ValueError(f'产品 {product_id} 不存在或不属于当前商户') from exc

        price = _to_decimal(raw_item.get('price', '0'), f'items[{index}].price')
        empty_diff_percent = _to_decimal(raw_item.get('empty_diff_percent', '0'), f'items[{index}].empty_diff_percent')
        color = raw_item.get('color')
        batch_number = raw_item.get('batch_number')
        remarks = raw_item.get('remarks')
        spec = raw_item.get('spec')
        unit = raw_item.get('unit') or product.get_unit_display() or '米'

        if warehouse_mode == basic_info_models.WareHouseModeEnum.UNRESTRICTED:
            if 'numbers' in raw_item and raw_item['numbers']:
                raise ValueError(f'仓库为宽进模式，items[{index}] 不应提供 numbers')
            quantity = _to_positive_int(raw_item.get('quantity'), f'items[{index}].quantity')
            num_of_rolls = _to_positive_int(raw_item.get('num_of_rolls'), f'items[{index}].num_of_rolls')
            quantity_of_rolls = None
            stock_flow_items.append({
                'product_id': product.id,
                'value': str(quantity),
                'num_of_rolls': num_of_rolls,
            })
        else:
            numbers = raw_item.get('numbers')
            if not numbers or not isinstance(numbers, list):
                raise ValueError(f'仓库为严进模式，items[{index}] 需要提供 numbers 数组')
            normalized_numbers = [
                str(_to_positive_int(value, f'items[{index}].numbers[{pos}]'))
                for pos, value in enumerate(numbers)
            ]
            num_of_rolls = len(normalized_numbers)
            quantity = sum(int(val) for val in normalized_numbers)
            quantity_of_rolls = ','.join(normalized_numbers)
            stock_flow_items.append({
                'product_id': product.id,
                'quantities': normalized_numbers,
            })

        purchase_items.append({
            'product': product,
            'price': price,
            'color': color,
            'quantity': quantity,
            'unit': unit,
            'empty_diff_percent': empty_diff_percent,
            'quantity_of_rolls': quantity_of_rolls,
            'num_of_rolls': num_of_rolls,
            'batch_number': batch_number,
            'remarks': remarks,
            'spec': spec,
        })

    return purchase_items, stock_flow_items


def _approve_purchase_order(
    purchase_order: models.PurchaseOrder,
    reviewed_by,
) -> models.PurchaseOrder:
    stock_flow_items = _build_stock_flow_items_from_order(purchase_order)

    with transaction.atomic():
        purchase_order.status = models.PurchaseOrderStatusEnum.APPROVED
        purchase_order.save(update_fields=['status', 'updated_at'])

    created_by_id = getattr(reviewed_by, 'id', None)
    if _auto_stock_task_enabled(purchase_order.merchant):
        logger.info('审批通过采购单 %s，触发入库任务', purchase_order.id)
        create_purchase_order_stock_entries.delay(
            purchase_order_id=purchase_order.id,
            warehouse_id=purchase_order.warehouse_id,
            items=stock_flow_items,
            created_by_id=created_by_id,
        )

    purchase_order.refresh_from_db(fields=['status', 'updated_at'])
    return purchase_order


def _cancel_purchase_order(purchase_order: models.PurchaseOrder) -> models.PurchaseOrder:
    if _purchase_order_has_stock_records(purchase_order):
        raise ValueError('采购单已生成出入库记录，无法作废')

    with transaction.atomic():
        purchase_order.status = models.PurchaseOrderStatusEnum.CANCELLED
        purchase_order.save(update_fields=['status', 'updated_at'])

    purchase_order.refresh_from_db(fields=['status', 'updated_at'])
    return purchase_order


def create_purchase_order_stock_entries_sync(
    *,
    purchase_order_id: int,
    warehouse_id: int,
    items: List[Dict[str, Any]],
    created_by_id: int | None = None,
) -> Dict[str, Any]:
    """
    根据采购单生成入库记录。
    """
    try:
        purchase_order = models.PurchaseOrder.objects.select_related('merchant').get(id=purchase_order_id)
    except models.PurchaseOrder.DoesNotExist:
        logger.error('PurchaseOrder %s 不存在，无法创建入库单', purchase_order_id)
        return {'error': 'purchase_order_not_found', 'purchase_order_id': purchase_order_id}

    merchant = purchase_order.merchant

    created_by = None
    if created_by_id:
        UserModel = get_user_model()
        created_by = UserModel.objects.filter(id=created_by_id).first()

    service = StockFlowService(merchant=merchant, created_by=created_by)
    record, details, created_count = service.stock_in(
        warehouse_id=warehouse_id,
        source_type=stock_models.StockChangeSourceEnum.PURCHASE,
        source_id=purchase_order.id,
        items=items,
    )

    payload = {
        'purchase_order_id': purchase_order.id,
        'stock_change_record_id': getattr(record, 'id', None),
        'created_details_count': created_count,
    }
    logger.info('采购单 %s 入库任务完成: %s', purchase_order.id, payload)
    return payload


def _build_stock_flow_items_from_order(purchase_order: models.PurchaseOrder) -> List[Dict[str, Any]]:
    """
    根据采购单明细还原 StockFlowService 所需的 items 结构。
    """
    warehouse_mode = purchase_order.warehouse.mode
    items_payload: List[Dict[str, Any]] = []

    order_items = purchase_order.items.all()
    if not order_items:
        raise ValueError('采购单没有任何明细，无法生成入库记录')

    if warehouse_mode == basic_info_models.WareHouseModeEnum.UNRESTRICTED:
        for item in order_items:
            items_payload.append({
                'product_id': item.product_id,
                'value': str(item.quantity),
                'num_of_rolls': item.num_of_rolls,
            })
        return items_payload

    # 严进 / 严进严出模式
    for item in order_items:
        raw_numbers = (item.quantity_of_rolls or '').split(',')
        normalized = [value.strip() for value in raw_numbers if value.strip()]
        if not normalized:
            raise ValueError('严进仓采购单缺少 numbers 数据，无法生成入库记录')
        items_payload.append({
            'product_id': item.product_id,
            'quantities': normalized,
        })
    return items_payload


def _auto_stock_task_enabled(merchant: basic_info_models.Merchant) -> bool:
    try:
        setting = MerchantSettingService.get_setting(
            merchant,
            basic_info_models.MerchantSettingKeyEnum.AUTO_CREATE_STOCK_CHANGE_TASKS,
        )
    except basic_info_models.MerchantSetting.DoesNotExist:
        logger.warning('商户 %s 未配置 auto_create_stock_change_tasks，默认关闭', merchant.id)
        return False
    return setting.value is True


def _purchase_order_has_stock_records(purchase_order: models.PurchaseOrder) -> bool:
    return stock_models.StockChangeRecord.objects.filter(
        merchant_id=purchase_order.merchant_id,
        source_type=stock_models.StockChangeSourceEnum.PURCHASE,
        source_id=purchase_order.id,
    ).exists()


def _resolve_purchase_order_instance(
    purchase_order: models.PurchaseOrder | None,
    purchase_order_id: int | None,
) -> models.PurchaseOrder:
    if purchase_order is None and purchase_order_id is None:
        raise ValueError('必须提供 purchase_order 或 purchase_order_id')

    if purchase_order is not None:
        purchase_order_id = purchase_order.id

    return models.PurchaseOrder.objects.select_related('merchant', 'warehouse').prefetch_related('items').get(
        id=purchase_order_id
    )


def _to_decimal(value, field_name: str) -> Decimal:
    try:
        return Decimal(str(value))
    except (InvalidOperation, TypeError) as exc:
        raise ValueError(f'{field_name} 必须是合法数值') from exc


def _to_positive_int(value, field_name: str) -> int:
    if value is None:
        raise ValueError(f'{field_name} 不能为空')
    decimal_value = _to_decimal(value, field_name)
    if decimal_value <= 0:
        raise ValueError(f'{field_name} 必须大于 0')
    if decimal_value != decimal_value.to_integral_value():
        raise ValueError(f'{field_name} 必须为整数')
    return int(decimal_value)