/**
 * 分期参数变更（期数 / 间隔 / 开始时间 / 提前天数 / 比例），非缴费模式切换
 * 规则见 docs/superpowers/specs/2026-06-04-protocol-pay-mode-switch-design.md §分期参数变更
 */

import {
  calcFqInstallmentDueDate,
  DEFAULT_INSTALLMENT_ADVANCE_DAYS,
  defaultInstallmentAmounts,
  normalizeInstallmentAmounts,
  sortFqPaymentDetails
} from '@/utils/protocol-payment-installment'
import {
  calcRemainingAmount,
  createPaymentDetailRow,
  type DetailLike,
  type EvaluateResult
} from '@/utils/protocol-pay-mode-switch'

export interface FqParams {
  installmentCount: number | null
  installmentIntervalMonths: number | null
  installmentStartDate: string
  installmentAdvanceDays: number | null
  installmentRatios: number[]
}

const BLOCKING_STATUSES = new Set(['jfqrz', 'tfqrz'])

function formatMoneySummary(v: number): string {
  return `¥${v.toFixed(2).replace(/\B(?=(\d{3})+(?!\d))/g, ',')}`
}

function countByStatus(details: DetailLike[], status: string): number {
  return details.filter((d) => String(d.payStatus || 'dfj') === status).length
}

function ratiosEqual(a: number[], b: number[]): boolean {
  if (a.length !== b.length) return false
  return a.every((v, i) => Math.abs(Number(v) - Number(b[i])) < 0.01)
}

export function fqParamsSnapshot(params: FqParams): FqParams {
  return {
    installmentCount: params.installmentCount,
    installmentIntervalMonths: params.installmentIntervalMonths,
    installmentStartDate: params.installmentStartDate || '',
    installmentAdvanceDays: params.installmentAdvanceDays,
    installmentRatios: [...(params.installmentRatios || [])]
  }
}

export function isSameFqParams(a: FqParams, b: FqParams): boolean {
  return (
    Number(a.installmentCount) === Number(b.installmentCount) &&
    Number(a.installmentIntervalMonths) === Number(b.installmentIntervalMonths) &&
    String(a.installmentStartDate || '') === String(b.installmentStartDate || '') &&
    Number(a.installmentAdvanceDays ?? DEFAULT_INSTALLMENT_ADVANCE_DAYS) ===
      Number(b.installmentAdvanceDays ?? DEFAULT_INSTALLMENT_ADVANCE_DAYS) &&
    ratiosEqual(a.installmentRatios || [], b.installmentRatios || [])
  )
}

export function getPaidInstallmentRows(details: DetailLike[]): DetailLike[] {
  return [...details]
    .filter((d) => String(d.payStatus) === 'yjf')
    .sort((a, b) => Number(a.installmentNo || 0) - Number(b.installmentNo || 0))
}

function maxPaidInstallmentNo(details: DetailLike[]): number {
  return getPaidInstallmentRows(details).reduce(
    (max, d) => Math.max(max, Number(d.installmentNo || 0)),
    0
  )
}

export function evaluateFqParamsChange(
  _oldParams: FqParams,
  newParams: FqParams,
  details: DetailLike[],
  contractAmount: number | null
): EvaluateResult {
  const rows = details.filter((d) => !d._voided)
  const newCount = Number(newParams.installmentCount)
  const interval = Number(newParams.installmentIntervalMonths)
  const startDate = String(newParams.installmentStartDate || '')

  if (!newCount || newCount < 1) {
    return { action: 'blocked', reason: '请填写有效的分期期数。' }
  }
  if (!interval || interval <= 0) {
    return { action: 'blocked', reason: '请填写有效的每期间隔（月）。' }
  }
  if (!startDate) {
    return { action: 'blocked', reason: '请填写分期开始时间。' }
  }

  if (rows.some((d) => BLOCKING_STATUSES.has(String(d.payStatus || '')))) {
    return {
      action: 'blocked',
      reason: '存在付款确认中或退费处理中的明细，请先完成相关流程后再修改分期参数。'
    }
  }

  const paidRows = getPaidInstallmentRows(rows)
  const maxPaidNo = maxPaidInstallmentNo(rows)

  if (maxPaidNo > 0 && newCount < maxPaidNo) {
    return {
      action: 'blocked',
      reason: `已有第 ${maxPaidNo} 期缴费记录，分期期数不能少于 ${maxPaidNo}。`
    }
  }

  const dfjCount = countByStatus(rows, 'dfj')

  if (paidRows.length === 0) {
    if (rows.length === 0) {
      return { action: 'noop' }
    }
    return {
      action: 'confirm',
      summary: `将按新参数（${newCount} 期）重新生成缴费明细，原有 ${rows.length} 条待缴计划将被替换。是否继续？`
    }
  }

  const remaining = calcRemainingAmount(contractAmount, rows)
  const newUnpaidCount = newCount - paidRows.length

  if (newUnpaidCount < 0) {
    return {
      action: 'blocked',
      reason: `已有 ${paidRows.length} 期缴费记录，分期期数不能少于 ${paidRows.length}。`
    }
  }

  if (remaining <= 0 && dfjCount > 0) {
    return { action: 'blocked', reason: '已缴清，无需调整分期计划。' }
  }

  const countChanged = Number(_oldParams.installmentCount) !== newCount

  if (countChanged) {
    return {
      action: 'confirm',
      summary: `将保留 ${paidRows.length} 期已缴记录，作废 ${dfjCount} 期未缴计划，并重新生成 ${newUnpaidCount} 期未缴明细（剩余 ${formatMoneySummary(remaining)}）。是否继续？`
    }
  }

  return {
    action: 'confirm',
    summary: `将保留已缴记录，并更新 ${dfjCount} 期未缴计划的应缴时间与金额（剩余 ${formatMoneySummary(remaining)}）。是否继续？`
  }
}

function buildFqAmounts(
  contractAmount: number | null,
  installmentAmounts: number[],
  paidRows: DetailLike[],
  count: number
): number[] {
  const amounts = normalizeInstallmentAmounts(installmentAmounts, contractAmount, count)
  if (paidRows.length === 0) {
    return amounts
  }
  paidRows.forEach((d) => {
    const no = Number(d.installmentNo)
    if (no >= 1 && no <= count) amounts[no - 1] = Number(d.dueAmount) || 0
  })
  return amounts
}

/** 按新分期参数重建明细：保留 yjf，作废原 dfj，生成剩余期次 */
export function applyFqParamsChange(
  params: FqParams,
  details: DetailLike[],
  contractAmount: number | null
): DetailLike[] {
  const count = Number(params.installmentCount) || 0
  const interval = Number(params.installmentIntervalMonths) || 0
  const startDate = params.installmentStartDate || ''
  const advanceDays = Number(params.installmentAdvanceDays ?? DEFAULT_INSTALLMENT_ADVANCE_DAYS)
  const installmentAmounts = normalizeInstallmentAmounts(
    params.installmentRatios || [],
    contractAmount,
    count
  )
  if (!count || !interval || !startDate) return details

  const paidRows = getPaidInstallmentRows(details).map((d) => ({
    ...d,
    _payModeLocked: true
  }))
  const remainingCount = count - paidRows.length
  const amounts = buildFqAmounts(contractAmount, installmentAmounts, paidRows, count)

  const result: DetailLike[] = [...paidRows]

  for (let i = 0; i < remainingCount; i++) {
    const periodIndex = paidRows.length + i
    result.push(
      createPaymentDetailRow({
        dueAmount: amounts[periodIndex] ?? null,
        installmentNo: periodIndex + 1,
        installmentDueDate: calcFqInstallmentDueDate(startDate, periodIndex, interval, advanceDays),
        expanded: false
      })
    )
  }

  return sortFqPaymentDetails(result)
}

/** 首次填充分期参数时生成明细（无需确认） */
export function generateInitialFqDetails(
  params: FqParams,
  contractAmount: number | null
): DetailLike[] {
  const count = Number(params.installmentCount) || 0
  const interval = Number(params.installmentIntervalMonths) || 0
  const startDate = params.installmentStartDate || ''
  const advanceDays = Number(params.installmentAdvanceDays ?? DEFAULT_INSTALLMENT_ADVANCE_DAYS)
  const installmentAmounts = normalizeInstallmentAmounts(
    params.installmentRatios || [],
    contractAmount,
    count
  )
  if (!count || !interval || !startDate) return []

  const amounts = installmentAmounts
  const result: DetailLike[] = []
  for (let i = 0; i < count; i++) {
    result.push(
      createPaymentDetailRow({
        dueAmount: amounts[i] ?? null,
        installmentNo: i + 1,
        installmentDueDate: calcFqInstallmentDueDate(startDate, i, interval, advanceDays),
        expanded: i === 0
      })
    )
  }
  return result
}