export type FixedAxis = { min: number; max: number; interval: number }

export function niceTickInterval(range: number, targetTicks: number): number {
  if (!Number.isFinite(range) || range <= 0) return 1
  const raw = range / targetTicks
  const magnitude = 10 ** Math.floor(Math.log10(raw))
  const fraction = raw / magnitude
  const niceFraction = fraction <= 1 ? 1 : fraction <= 2 ? 2 : fraction <= 5 ? 5 : 10
  return niceFraction * magnitude
}

export function fixedAxisRange(
  type: string,
  dataMin: number | undefined,
  dataMax: number | undefined,
): FixedAxis | null {
  if (dataMin == null || dataMax == null || !Number.isFinite(dataMin) || !Number.isFinite(dataMax)) return null
  let range = dataMax - dataMin
  if (range <= 0) range = Math.max(Math.abs(dataMax) * 0.1, 1e-9)
  const pad = range * 0.1
  let min = dataMin - pad
  let max = dataMax + pad
  if (type === '位移') {
    const interval = niceTickInterval(max - min, 6)
    min = Math.floor(min / interval) * interval
    max = Math.ceil(max / interval) * interval
    return { min, max, interval }
  }
  const raw = (max - min) / 6
  const interval = type === '压力'
    ? Math.max(1, niceTickInterval(Math.max(raw, 1), 1))
    : niceTickInterval(max - min, 6)
  min = Math.floor(min / interval) * interval
  max = Math.ceil(max / interval) * interval
  return { min, max, interval }
}