const KG_PER_CBM = 167
const KG_PER_BILLABLE_CBM = 363

function formatFormulaNumber(value: number) {
  return value.toLocaleString('zh-CN', { maximumFractionDigits: 6, useGrouping: false })
}

export interface PriceEstimateBreakdown {
  actualLabel: string
  actualQuantity: number
  convertedLabel: string
  convertedQuantity: number
  convertedFormula: string
  chargeableLabel: string
  basisLabel: string
}

/**
 * Explains the server's current first-leg chargeable-quantity rules. The server
 * response remains authoritative for the final chargeable quantity and amount.
 */
export function createPriceEstimateBreakdown(
  actualWeightKg: number,
  actualVolumeCbm: number,
  chargeUnit: string,
): PriceEstimateBreakdown | null {
  if (chargeUnit === 'KG') {
    const volumeWeightKg = actualVolumeCbm * KG_PER_CBM
    return {
      actualLabel: '实际毛重',
      actualQuantity: actualWeightKg,
      convertedLabel: '体积重量',
      convertedQuantity: volumeWeightKg,
      convertedFormula: `${formatFormulaNumber(actualVolumeCbm)} m³ × ${KG_PER_CBM}`,
      chargeableLabel: '计费重量',
      basisLabel: actualWeightKg >= volumeWeightKg ? '采用实际毛重' : '采用体积重量',
    }
  }

  if (chargeUnit === 'CBM') {
    const convertedVolumeCbm = actualWeightKg / KG_PER_BILLABLE_CBM
    return {
      actualLabel: '实际体积',
      actualQuantity: actualVolumeCbm,
      convertedLabel: '重量折算体积',
      convertedQuantity: convertedVolumeCbm,
      convertedFormula: `${formatFormulaNumber(actualWeightKg)} KG ÷ ${KG_PER_BILLABLE_CBM}`,
      chargeableLabel: '计费体积',
      basisLabel: actualVolumeCbm >= convertedVolumeCbm ? '采用实际体积' : '采用重量折算体积',
    }
  }

  return null
}