model-billing.js
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const MICROS_PER_YUAN = 1_000_000
const POLICY_SETTLERS = {
record_only() {
return 0
},
fixed_points(policy) {
return policy.points
},
cost_ratio(policy, supplierCost) {
return Math.ceil(supplierCost.supplier_cost_micros * policy.points_per_yuan / MICROS_PER_YUAN)
},
}
/**
* 模型供应商成本到用户积分的唯一结算入口。
* @param {{ deduct:(input:object)=>Promise<{balance_after:number,ledger_id:string}> }} deps
*/
export function createModelBilling({ deduct }) {
return async function settleModelBilling(input) {
const settlement = modelSettlement(input.policy, input.supplier_cost)
if (settlement.charged_points === 0) return { ...settlement, ledger_id: null }
const ledger = await deduct({
user_id: input.user_id,
amount: settlement.charged_points,
reason: 'model_usage',
ref_type: input.call_ref.type,
ref_id: input.call_ref.id,
idempotency_key: input.idempotency_key,
})
return { ...settlement, ledger_id: ledger.ledger_id }
}
}
/**
* 结算入口的唯一数据构造点。非法策略和金额在写 ledger 前立即失败。
* @param {Record<string, any>} input
*/
function modelSettlement(policy, supplierCost) {
const billingPolicySnapshot = policySnapshot(policy)
const chargedPoints = POLICY_SETTLERS[policy.mode](billingPolicySnapshot, supplierCost)
return {
billing_mode: billingPolicySnapshot.mode,
billing_policy_snapshot: billingPolicySnapshot,
charged_points: chargedPoints,
}
}
/** 校验并构造可审计的精确策略快照；不接受未声明字段。 */
function policySnapshot(policy) {
switch (policy.mode) {
case 'record_only':
return { mode: policy.mode, reason: policy.reason }
case 'fixed_points':
return { mode: policy.mode, points: policy.points }
case 'cost_ratio':
return { mode: policy.mode, points_per_yuan: policy.points_per_yuan }
default:
throw new Error(`Unhandled billing mode: ${policy.mode}`)
}
}