/** 进位方式：向下取整、向上取整、四舍五入 */
export type FormattedNumberRounding = 'floor' | 'ceil' | 'round'

/** 仅保留数字、至多一个小数点、可选前导负号 */
export function sanitizeNumericInput(raw: string): string {
  const t = raw.trim()
  if (!t) return ''
  let i = 0
  let res = ''
  if (t[0] === '-') {
    res = '-'
    i = 1
  }
  let dot = false
  for (; i < t.length; i++) {
    const c = t[i]
    if (c >= '0' && c <= '9') {
      res += c
      continue
    }
    if (c === '.' && !dot) {
      dot = true
      if (res === '' || res === '-') res += '0'
      res += '.'
    }
  }
  return res
}

export function stripNumberGrouping(s: string): string {
  return s.replace(/,/g, '').trim()
}

/**
 * 对已清洗的数字串按整数位、小数位截断输入长度（inputLimit 为 true 时使用）。
 * 整数部分至多 integerDigits 位，小数部分至多 decimalPlaces 位；保留末尾仅小数点（如 `12.`）以便继续输入。
 */
export function applyNumericInputDigitLimits(
  sanitized: string,
  integerDigits: number,
  decimalPlaces: number
): string {
  if (!sanitized || sanitized === '-') return sanitized
  const neg = sanitized[0] === '-'
  let body = neg ? sanitized.slice(1) : sanitized
  const dotIdx = body.indexOf('.')
  if (dotIdx === -1) {
    const maxInt = Math.max(0, integerDigits)
    body = maxInt > 0 ? body.slice(0, maxInt) : body
    return neg ? '-' + body : body
  }
  let intPart = body.slice(0, dotIdx)
  if (integerDigits > 0) {
    intPart = intPart.slice(0, integerDigits)
  }
  const afterDot = body.slice(dotIdx + 1)
  const endsWithDot = afterDot === '' && body.endsWith('.')
  if (decimalPlaces <= 0) {
    return neg ? '-' + intPart : intPart
  }
  if (endsWithDot) {
    return (neg ? '-' : '') + intPart + '.'
  }
  const decPart = afterDot.slice(0, decimalPlaces)
  return (neg ? '-' : '') + intPart + '.' + decPart
}

function maxAbsValue(integerDigits: number, decimalPlaces: number): number {
  const maxInt = Math.pow(10, integerDigits) - 1
  if (decimalPlaces <= 0) return maxInt
  return maxInt + (1 - Math.pow(10, -decimalPlaces))
}

/** 按整数位数上限约束绝对值 */
export function clampByIntegerDigits(
  value: number,
  integerDigits: number,
  decimalPlaces: number
): number {
  const max = maxAbsValue(integerDigits, decimalPlaces)
  const sign = value < 0 ? -1 : 1
  const abs = Math.abs(value)
  if (abs <= max) return value
  return sign * max
}

export function roundToDecimals(
  value: number,
  decimalPlaces: number,
  rounding: FormattedNumberRounding
): number {
  if (decimalPlaces <= 0) {
    switch (rounding) {
      case 'floor':
        return Math.floor(value)
      case 'ceil':
        return Math.ceil(value)
      default:
        return Math.round(value)
    }
  }
  const factor = Math.pow(10, decimalPlaces)
  const x = value * factor
  let y: number
  switch (rounding) {
    case 'floor':
      y = Math.floor(x)
      break
    case 'ceil':
      y = Math.ceil(x)
      break
    default:
      y = Math.round(x)
  }
  return y / factor
}

/**
 * 解析 → 按整数位夹紧 → 按小数位与进位方式舍入 → 再夹紧（防止舍入后越界）
 */
export function normalizeNumericValue(
  value: number,
  integerDigits: number,
  decimalPlaces: number,
  rounding: FormattedNumberRounding
): number {
  let v = clampByIntegerDigits(value, integerDigits, decimalPlaces)
  v = roundToDecimals(v, decimalPlaces, rounding)
  v = clampByIntegerDigits(v, integerDigits, decimalPlaces)
  return v
}

/**
 * 固定小数位数字符串（无千分位），用于表单存值以保留配置的小数位数（number 无法保留尾随 0）。
 */
export function toFixedDecimalString(value: number, decimalPlaces: number): string {
  if (Number.isNaN(value) || !Number.isFinite(value)) return ''
  return value.toFixed(Math.max(0, decimalPlaces))
}

/** 千分位格式化展示（整数部分），小数部分固定 m 位 */
export function formatWithThousands(value: number, decimalPlaces: number): string {
  if (Number.isNaN(value) || !Number.isFinite(value)) return ''
  const fixed = value.toFixed(Math.max(0, decimalPlaces))
  const neg = fixed.startsWith('-')
  const body = neg ? fixed.slice(1) : fixed
  const [intPart, decPart] = body.split('.')
  const withSep = intPart.replace(/\B(?=(\d{3})+(?!\d))/g, ',')
  if (decimalPlaces <= 0 || decPart === undefined) return (neg ? '-' : '') + withSep
  return (neg ? '-' : '') + withSep + '.' + decPart
}

/** 编辑态：无千分位，去掉多余尾部 0（在 m 位精度内） */
export function numberToEditString(value: number, decimalPlaces: number): string {
  if (Number.isNaN(value) || !Number.isFinite(value)) return ''
  let s = value.toFixed(Math.max(0, decimalPlaces))
  s = s.replace(/(\.\d*?)0+$/, '$1')
  s = s.replace(/\.$/, '')
  return s
}