22 lines
964 B
TypeScript
22 lines
964 B
TypeScript
/**
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* 后台按份数撤销拼单份额：校验并算出保留下来的份数。
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*
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* 口径（已确认）：
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* - 只能部分撤销，撤到 0 份走「单人撤单」，所以 `1 ≤ 撤掉份数 ≤ 当前份数 − 1`；
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* - 押金不随份数减少而退还（保持原冻结额），这里只算数量。
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*/
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export function resolveShareReduceTargetQuantity(input: {
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currentQuantity: number
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reduceQuantity: number
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}): { nextQuantity: number; failureReason: 'invalid_quantity' | null } {
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const current = Math.floor(Number(input.currentQuantity) || 0)
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const reduce = Math.floor(Number(input.reduceQuantity) || 0)
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if (!Number.isFinite(current) || !Number.isFinite(reduce)) {
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return { nextQuantity: 0, failureReason: 'invalid_quantity' }
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}
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if (current < 2 || reduce < 1 || reduce > current - 1) {
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return { nextQuantity: 0, failureReason: 'invalid_quantity' }
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}
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return { nextQuantity: current - reduce, failureReason: null }
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}
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