"""代金券规则引擎：动态加载规则、校验、使用"""

import json
from decimal import Decimal
from datetime import datetime

from appPublic.uniqueID import getID
from .registry import RULE_REGISTRY


def validate_voucher(sor, instance_id, context):
    """
    校验代金券是否可用

    Args:
        sor: SQLor 上下文
        instance_id: 券实例ID
        context: dict, 包含 request_amount, product_type, product_name, user_level 等

    Returns:
        (bool, Decimal, str): (可用, 抵扣金额, 错误信息)
    """
    # 1. 查询券实例
    instance = sor.R('voucher_instance', {'id': instance_id}).first()
    if not instance:
        return False, Decimal('0'), "代金券不存在"

    # 2. 状态检查（一次性使用）
    if instance.status != 'unused':
        return False, Decimal('0'), "代金券已使用或失效"

    # 3. 有效期检查
    now = datetime.now()
    if instance.valid_from and now < instance.valid_from:
        return False, Decimal('0'), "代金券尚未生效"
    if instance.valid_to and now > instance.valid_to:
        return False, Decimal('0'), "代金券已过期"

    # 4. 加载模板规则（按 sort_order 排序）
    rules = sor.R('voucher_rule', {
        'template_id': instance.template_id,
        'enabled': 1
    }, {'sort': 'sort_order'})

    # 5. 构建执行上下文
    ctx = {
        'instance': instance,
        'used_count': instance.get('used_count', 0) if isinstance(instance, dict) else 0,
        'valid_from': instance.valid_from,
        'valid_to': instance.valid_to,
        **context
    }

    # 6. 依次执行规则
    for rule in rules:
        rule_type = rule.rule_type if hasattr(rule, 'rule_type') else rule['rule_type']
        rule_config_str = rule.rule_config if hasattr(rule, 'rule_config') else rule['rule_config']

        if rule_type not in RULE_REGISTRY:
            continue  # 未知规则类型跳过

        try:
            config = json.loads(rule_config_str) if isinstance(rule_config_str, str) else rule_config_str
        except (json.JSONDecodeError, TypeError):
            continue

        validator = RULE_REGISTRY[rule_type]
        ok, err_msg = validator(config, ctx)
        if not ok:
            return False, Decimal('0'), err_msg

    # 7. 计算抵扣金额（一次性，不找零）
    face_value = Decimal(str(instance.face_value if hasattr(instance, 'face_value') else instance['face_value']))
    request_amount = Decimal(str(context.get('request_amount', 0)))
    deductible = min(face_value, request_amount)

    return True, deductible, None


def apply_voucher(sor, instance_id, customer_id, order_id, context):
    """
    使用代金券（一次性，不找零）

    Args:
        sor: SQLor 上下文
        instance_id: 券实例ID
        customer_id: 客户ID
        order_id: 订单ID
        context: dict, 包含 request_amount, product_type, product_name 等

    Returns:
        (bool, Decimal, str): (成功, 抵扣金额, 错误信息)
    """
    # 1. 校验
    ok, deductible, err = validate_voucher(sor, instance_id, context)
    if not ok:
        return False, Decimal('0'), err

    # 2. 获取券实例信息
    instance = sor.R('voucher_instance', {'id': instance_id}).first()
    face_value = Decimal(str(instance.face_value if hasattr(instance, 'face_value') else instance['face_value']))

    now = datetime.now()

    # 3. 记录使用流水
    sor.I('voucher_usage_log', {
        'id': getID(),
        'instance_id': instance_id,
        'customer_id': customer_id,
        'order_id': order_id,
        'face_value': face_value,
        'deducted_amount': deductible,
        'used_at': now,
        'used_by': sor.env.get_user() if hasattr(sor, 'env') else None,
        'product_type': context.get('product_type', ''),
        'product_name': context.get('product_name', '')
    })

    # 4. 标记券为已使用（一次性，直接作废）
    sor.U('voucher_instance', {'id': instance_id}, {
        'status': 'used',
        'actual_deducted': deductible,
        'used_at': now,
        'order_id': order_id
    })

    return True, deductible, None


def batch_apply_vouchers(sor, customer_id, order_id, voucher_ids, context):
    """
    批量使用代金券（依次尝试，直到消费金额抵扣完）

    Args:
        sor: SQLor 上下文
        customer_id: 客户ID
        order_id: 订单ID
        voucher_ids: 券实例ID列表
        context: dict, 包含 request_amount, product_type, product_name 等

    Returns:
        dict: {total_deducted, remaining, details: [{voucher_id, deducted, error}]}
    """
    total_deducted = Decimal('0')
    remaining = Decimal(str(context.get('request_amount', 0)))
    details = []

    for vid in voucher_ids:
        if remaining <= 0:
            break

        ctx = {**context, 'request_amount': remaining}
        ok, deducted, err = apply_voucher(sor, vid, customer_id, order_id, ctx)

        if ok:
            total_deducted += deducted
            remaining -= deducted
            details.append({'voucher_id': vid, 'deducted': float(deducted), 'error': None})
        else:
            details.append({'voucher_id': vid, 'deducted': 0, 'error': err})

    return {
        'total_deducted': float(total_deducted),
        'remaining': float(remaining),
        'details': details
    }


def get_available_vouchers(sor, customer_id, context=None):
    """
    查询客户可用代金券

    Args:
        sor: SQLor 上下文
        customer_id: 客户ID
        context: 可选，用于预校验

    Returns:
        list: 可用券实例列表
    """
    now = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
    vouchers = sor.R('voucher_instance', {
        'customer_id': customer_id,
        'status': 'unused'
    }, {'sort': 'valid_to'})

    if not context:
        return list(vouchers)

    # 带 context 时预校验过滤
    available = []
    for v in vouchers:
        vid = v.id if hasattr(v, 'id') else v['id']
        ok, _, _ = validate_voucher(sor, vid, context)
        if ok:
            available.append(v)

    return available