"""内置规则校验器，每种规则一个函数，返回 (bool, error_msg)"""

from decimal import Decimal
from datetime import datetime
from .registry import register_rule


@register_rule('min_amount')
def check_min_amount(config, context):
    """最低消费门槛"""
    min_val = Decimal(str(config.get('min_value', 0)))
    request_amount = Decimal(str(context.get('request_amount', 0)))
    if request_amount < min_val:
        return False, f"未达最低消费 {min_val} 元"
    return True, None


@register_rule('max_amount')
def check_max_amount(config, context):
    """最高消费限制"""
    max_val = Decimal(str(config.get('max_value', 0)))
    if max_val <= 0:
        return True, None
    request_amount = Decimal(str(context.get('request_amount', 0)))
    if request_amount > max_val:
        return False, f"超过最高消费 {max_val} 元"
    return True, None


@register_rule('applicable_product_type')
def check_product_type(config, context):
    """限定产品类型（大类：llm/image/video/audio）"""
    allowed_types = config.get('product_types', [])
    if not allowed_types:
        return True, None
    current_type = context.get('product_type', '')
    if current_type and current_type not in allowed_types:
        return False, f"仅限 {', '.join(allowed_types)} 类型使用"
    return True, None


@register_rule('applicable_product')
def check_specific_product(config, context):
    """限定特定产品（具体模型名）"""
    allowed_products = config.get('products', [])
    if not allowed_products:
        return True, None
    current_product = context.get('product_name', '')
    if current_product and current_product not in allowed_products:
        return False, f"仅限 {', '.join(allowed_products)} 使用"
    return True, None


@register_rule('exclude_product')
def check_exclude_product(config, context):
    """排除特定产品"""
    excluded = config.get('products', [])
    if not excluded:
        return True, None
    current_product = context.get('product_name', '')
    if current_product and current_product in excluded:
        return False, f"{current_product} 不可使用此代金券"
    return True, None


@register_rule('max_usage_count')
def check_max_usage_count(config, context):
    """最大使用次数"""
    max_count = int(config.get('max_count', 0))
    if max_count == 0:
        return True, None
    used_count = int(context.get('used_count', 0))
    if used_count >= max_count:
        return False, f"已达最大使用次数 {max_count} 次"
    return True, None


@register_rule('valid_period')
def check_valid_period(config, context):
    """有效期检查（通常由 instance 的 valid_from/valid_to 自动处理，此规则用于额外限制）"""
    now = datetime.now()
    valid_from = context.get('valid_from')
    valid_to = context.get('valid_to')
    if valid_from and now < valid_from:
        return False, "代金券尚未生效"
    if valid_to and now > valid_to:
        return False, "代金券已过期"
    return True, None


@register_rule('user_level')
def check_user_level(config, context):
    """用户等级限制"""
    required_level = int(config.get('min_level', 0))
    if required_level == 0:
        return True, None
    user_level = int(context.get('user_level', 0))
    if user_level < required_level:
        return False, f"需 {required_level} 级以上用户"
    return True, None