package employeecollection

import (
	"github.com/break/junhong_cmp_fiber/pkg/constants"
	"github.com/break/junhong_cmp_fiber/pkg/errors"
)

// RefundOffsetDecision 是来源订单退款成功对账单的处理判定结果。
type RefundOffsetDecision struct {
	// Outcome 取值见 constants.EmployeeCollectionRefundOutcome*。
	Outcome string
	// ReducedAmount 是本次实际冲减的应收金额（分），仅 reduced 时大于零。
	ReducedAmount int64
}

// DecideRefundOffset 判定来源订单本次退款成功金额对账单的处理方式。
// 判定顺序：已关闭账单与存在已通过或审批中分摊的账单只写退款关联提示，
// 其余按退款成功金额与账单应收比较，等于或超过应收时关闭账单，小于应收时按退款金额冲减。
// 已通过分摊体现为 received_amount > 0，审批中分摊体现为 reserved_amount > 0；
// 这两个金额只由本能力的条件更新维护，因此与「存在已通过或审批中分摊」等价。
func DecideRefundOffset(bill BillAmounts, refundAmount int64) (RefundOffsetDecision, error) {
	if refundAmount <= 0 {
		return RefundOffsetDecision{}, errors.New(errors.CodeInvalidParam, "退款成功金额必须大于零")
	}
	if err := bill.Validate(); err != nil {
		return RefundOffsetDecision{}, err
	}
	if bill.Closed || bill.Received > 0 || bill.Reserved > 0 {
		return RefundOffsetDecision{Outcome: constants.EmployeeCollectionRefundOutcomeHintOnly}, nil
	}
	if refundAmount >= bill.Receivable {
		return RefundOffsetDecision{Outcome: constants.EmployeeCollectionRefundOutcomeClosedFull}, nil
	}
	return RefundOffsetDecision{
		Outcome: constants.EmployeeCollectionRefundOutcomeReduced, ReducedAmount: refundAmount,
	}, nil
}