"use client"
import { use, useEffect, useMemo, useRef, useState } from 'react'
import Link from 'next/link'
import {
  Chart as ChartJS,
  CategoryScale,
  LinearScale,
  PointElement,
  LineElement,
  BarElement,
  Tooltip,
  Legend,
} from 'chart.js'
import { Line, Bar, Scatter } from 'react-chartjs-2'
// 仅导入类型以启用插件的类型增强，不触发运行时代码
import type {} from 'chartjs-plugin-zoom'

ChartJS.register(CategoryScale, LinearScale, PointElement, LineElement, BarElement, Tooltip, Legend)

type Detail = {
  id: string
  timestamp: string
  code: number[]
  fit?: { a: number; b: number }
  sampleCount: number
  duration: number
  stats: {
    codeMin: number
    codeMax: number
    codeAvg: number
    forceMin?: number
    forceMax?: number
    forceAvg?: number
  }
}

function toFixed(n: number | undefined | null, d = 3) {
  if (n == null || Number.isNaN(n)) return '-'
  return n.toFixed(d)
}

export default function Page({ params }: { params: Promise<{ id: string }> }) {
  const { id } = use(params)
  const [loading, setLoading] = useState(false)
  const [error, setError] = useState<string | null>(null)
  const [rec, setRec] = useState<Detail | null>(null)
  // 滤波相关状态
  const [filterType, setFilterType] = useState<'none' | 'ema' | 'sg' | 'hampel_sg' | 'gauss'>('hampel_sg')
  const [emaAlpha, setEmaAlpha] = useState(0.01)
  const [sgWindow, setSgWindow] = useState(21)
  const [sgOrder, setSgOrder] = useState<2 | 3>(3)
  const [hampelWindow, setHampelWindow] = useState(11)
  const [hampelK, setHampelK] = useState(2)
  const [gaussSigma, setGaussSigma] = useState(5)
  const [showOriginal, setShowOriginal] = useState(false)
  const [showFiltered, setShowFiltered] = useState(true)

  useEffect(() => {
    const controller = new AbortController()
    async function run() {
      setLoading(true)
      setError(null)
      try {
        const res = await fetch(`/api/records/${id}`, { signal: controller.signal })
        if (!res.ok) throw new Error(`HTTP ${res.status}`)
        const j = await res.json()
        setRec(j)
      } catch (e) {
        // @ts-expect-error any
        if (e.name !== 'AbortError') setError(e.message || '加载失败')
      } finally {
        setLoading(false)
      }
    }
    run()
    return () => controller.abort()
  }, [id])

  // 若存在拟合，默认不显示滤波码值（仅在记录加载时初始化一次）
  useEffect(() => {
    if (rec?.fit) setShowFiltered(false)
  }, [rec?.fit])

  // 侦测小屏（手机）以调整 Chart 布局
  const [isSmall, setIsSmall] = useState(false)
  useEffect(() => {
    if (typeof window === 'undefined') return
    const mql = window.matchMedia('(max-width: 640px)')
    const apply = () => setIsSmall(mql.matches)
    apply()
    if ((mql as any).addEventListener) {
      mql.addEventListener('change', apply)
      return () => mql.removeEventListener('change', apply)
    }
  }, [])

  // 动态加载并注册缩放插件（仅在客户端）
  const zoomRef = useRef<any>(null)
  useEffect(() => {
    let cancelled = false
    ;(async () => {
      try {
        const mod: any = await import('chartjs-plugin-zoom')
        const plugin = mod?.default ?? mod
        if (!cancelled) {
          zoomRef.current = plugin
          ChartJS.register(plugin)
        }
      } catch (err) {
        console.error('Failed to load chartjs-plugin-zoom', err)
      }
    })()
    return () => {
      cancelled = true
      if (zoomRef.current) {
        try { ChartJS.unregister(zoomRef.current) } catch {}
        zoomRef.current = null
      }
    }
  }, [])

  const timeAxis = useMemo(() => {
    if (!rec) return [] as number[]
    const step = rec.sampleCount > 0 ? (rec.duration * 1000) / rec.sampleCount : 0
    return Array.from({ length: rec.sampleCount }, (_, i) => +(i * step).toFixed(3))
  }, [rec])

  const filteredCode = useMemo(() => {
    if (!rec) return [] as number[]
    const x = rec.code
    switch (filterType) {
      case 'none':
        return x
      case 'ema':
        return applyEMA(x, emaAlpha)
      case 'sg': {
        const w = makeOddSafe(sgWindow, x.length)
        return savitzkyGolay(x, w, sgOrder)
      }
      case 'hampel_sg': {
        const hw = makeOddSafe(hampelWindow, x.length)
        const w = makeOddSafe(sgWindow, x.length)
        const y = hampelFilter(x, hw, hampelK)
        return savitzkyGolay(y, w, sgOrder)
      }
      case 'gauss':
        return gaussianSmooth(x, gaussSigma)
      default:
        return x
    }
  }, [rec, filterType, emaAlpha, sgWindow, sgOrder, hampelWindow, hampelK, gaussSigma])

  const forceSeries = useMemo(() => {
    if (!rec?.fit) return undefined
    const { a, b } = rec.fit
    const dataToUse = filterType === 'none' ? (rec.code) : filteredCode
    return dataToUse.map((c: number) => a * c + b)
  }, [rec, filterType, filteredCode])

  const codeHistogram = useMemo(() => {
    const dataToUse = filterType === 'none' ? (rec?.code || []) : filteredCode
    return buildHistogram(dataToUse, 30)
  }, [rec, filterType, filteredCode])

  return (
    <div className="min-h-screen bg-zinc-50 text-zinc-900 dark:bg-black dark:text-zinc-100">
      <div className="mx-auto max-w-6xl p-2 sm:p-6">
        <div className="mb-3 sm:mb-4 flex items-center justify-between">
          <div className="flex items-center gap-3">
            <Link href="/" className="rounded border px-3 py-1.5">← 返回</Link>
            <h1 className="text-xl font-semibold">记录 {rec?.id || id}</h1>
          </div>
          <div className="flex gap-2">
            <a
              href={`/api/export`}
              onClick={async (e) => {
                e.preventDefault()
                const body = JSON.stringify({ ids: [id], format: 'csv' as const })
                const res = await fetch('/api/export', { method: 'POST', headers: { 'content-type': 'application/json' }, body })
                const blob = await res.blob()
                const url = URL.createObjectURL(blob)
                const a = document.createElement('a')
                a.href = url
                a.download = `record-${id}.csv`
                a.click()
                URL.revokeObjectURL(url)
              }}
              className="rounded bg-zinc-900 px-3 py-1.5 text-white dark:bg-zinc-100 dark:text-black"
            >导出 CSV</a>
          </div>
        </div>

        {loading && <div className="rounded bg-zinc-200 p-4 dark:bg-zinc-800">加载中...</div>}
        {error && <div className="rounded bg-red-100 p-4 text-red-800">{error}</div>}
        {rec && (
          <div className="flex flex-col gap-4 sm:gap-6">
            <section className="grid grid-cols-1 gap-3 sm:gap-4 sm:grid-cols-3">
              <div className="rounded-lg border p-3 sm:p-4 dark:border-zinc-800">
                <div className="text-sm text-zinc-500">上传时间</div>
                <div className="mt-1 text-lg">{new Date(rec.timestamp).toLocaleString()}</div>
              </div>
              <div className="rounded-lg border p-3 sm:p-4 dark:border-zinc-800">
                <div className="text-sm text-zinc-500">采样</div>
                <div className="mt-1 text-lg">{rec.sampleCount} 点 · {rec.duration.toFixed(3)} s · {(rec.sampleCount / rec.duration).toFixed(2)} Hz</div>
              </div>
              <div className="rounded-lg border p-3 sm:p-4 dark:border-zinc-800">
                <div className="text-sm text-zinc-500">拟合</div>
                <div className="mt-1 text-lg">{rec.fit ? `y = ${rec.fit.a.toFixed(4)}x + ${rec.fit.b.toFixed(3)}` : '未拟合'}</div>
              </div>
            </section>

            <section className="grid grid-cols-1 gap-3 sm:gap-4 sm:grid-cols-3">
              <div className="rounded-lg border p-3 sm:p-4 dark:border-zinc-800">
                <div className="text-sm text-zinc-500">码值统计</div>
                <div className="mt-1 text-lg">[{rec.stats.codeMin} ~ {rec.stats.codeMax}] · 均值 {toFixed(rec.stats.codeAvg, 2)}</div>
              </div>
              <div className="rounded-lg border p-3 sm:p-4 dark:border-zinc-800">
                <div className="text-sm text-zinc-500">力值统计</div>
                <div className="mt-1 text-lg">{rec.fit ? `[${toFixed(rec.stats.forceMin, 2)} ~ ${toFixed(rec.stats.forceMax, 2)}] mN · 均值 ${toFixed(rec.stats.forceAvg, 2)}` : '—'}</div>
              </div>
              <div className="rounded-lg border p-3 sm:p-4 dark:border-zinc-800">
                <div className="text-sm text-zinc-500">峰峰值</div>
                <div className="mt-1 text-lg">码值 {rec.stats.codeMax - rec.stats.codeMin}{rec.fit && rec.stats.forceMax != null && rec.stats.forceMin != null ? ` · 力值 ${(rec.stats.forceMax - rec.stats.forceMin).toFixed(2)} mN` : ''}</div>
              </div>
            </section>

            <section className="rounded-lg border p-2 sm:p-4 dark:border-zinc-800">
              <div className="mb-2 sm:mb-3 flex items-center justify-between">
                <div className="text-sm text-zinc-500">时序曲线</div>
                <div className="flex flex-wrap items-center gap-4">
                  <label className="flex items-center gap-2 text-sm">
                    <span>滤波器:</span>
                    <select
                      className="rounded border bg-transparent px-2 py-1 dark:border-zinc-700"
                      value={filterType}
                      onChange={(e) => setFilterType(e.target.value as any)}
                    >
                      <option value="none">无</option>
                      <option value="ema">EMA</option>
                      <option value="sg">Savitzky–Golay</option>
                      <option value="hampel_sg">Hampel + SG</option>
                      <option value="gauss">Gaussian（零相位）</option>
                    </select>
                  </label>

                  {filterType === 'ema' && (
                    <label className="flex items-center gap-2 text-sm">
                      <span>α:</span>
                      <input
                        type="range"
                        min="0.01"
                        max="1"
                        step="0.01"
                        value={emaAlpha}
                        onChange={(e) => setEmaAlpha(Number(e.target.value))}
                        className="w-28"
                      />
                      <span className="w-12 text-right">{emaAlpha.toFixed(2)}</span>
                    </label>
                  )}

                  {filterType === 'sg' && (
                    <div className="flex items-center gap-4 text-sm">
                      <label className="flex items-center gap-2">
                        <span>窗口:</span>
                        <input
                          type="number"
                          className="w-16 rounded border bg-transparent px-2 py-1 dark:border-zinc-700"
                          value={sgWindow}
                          min={5}
                          step={2}
                          onChange={(e) => setSgWindow(Number(e.target.value))}
                        />
                      </label>
                      <label className="flex items-center gap-2">
                        <span>阶数:</span>
                        <select
                          className="rounded border bg-transparent px-2 py-1 dark:border-zinc-700"
                          value={sgOrder}
                          onChange={(e) => setSgOrder(Number(e.target.value) as 2 | 3)}
                        >
                          <option value={2}>2</option>
                          <option value={3}>3</option>
                        </select>
                      </label>
                    </div>
                  )}

                  {filterType === 'hampel_sg' && (
                    <div className="flex items-center gap-4 text-sm">
                      <label className="flex items-center gap-2">
                        <span>Hampel窗口:</span>
                        <input
                          type="number"
                          className="w-16 rounded border bg-transparent px-2 py-1 dark:border-zinc-700"
                          value={hampelWindow}
                          min={5}
                          step={2}
                          onChange={(e) => setHampelWindow(Number(e.target.value))}
                        />
                      </label>
                      <label className="flex items-center gap-2">
                        <span>阈值k:</span>
                        <input
                          type="number"
                          className="w-16 rounded border bg-transparent px-2 py-1 dark:border-zinc-700"
                          value={hampelK}
                          min={1}
                          step={0.5}
                          onChange={(e) => setHampelK(Number(e.target.value))}
                        />
                      </label>
                      <label className="flex items-center gap-2">
                        <span>SG窗口:</span>
                        <input
                          type="number"
                          className="w-16 rounded border bg-transparent px-2 py-1 dark:border-zinc-700"
                          value={sgWindow}
                          min={5}
                          step={2}
                          onChange={(e) => setSgWindow(Number(e.target.value))}
                        />
                      </label>
                      <label className="flex items-center gap-2">
                        <span>SG阶数:</span>
                        <select
                          className="rounded border bg-transparent px-2 py-1 dark:border-zinc-700"
                          value={sgOrder}
                          onChange={(e) => setSgOrder(Number(e.target.value) as 2 | 3)}
                        >
                          <option value={2}>2</option>
                          <option value={3}>3</option>
                        </select>
                      </label>
                    </div>
                  )}

                  {filterType === 'gauss' && (
                    <label className="flex items-center gap-2 text-sm">
                      <span>σ(点):</span>
                      <input
                        type="range"
                        min={0.5}
                        max={10}
                        step={0.5}
                        value={gaussSigma}
                        onChange={(e) => setGaussSigma(Number(e.target.value))}
                        className="w-40"
                      />
                      <span className="w-12 text-right">{gaussSigma.toFixed(1)}</span>
                    </label>
                  )}

                  <label className="flex items-center gap-2 text-sm">
                    <input type="checkbox" className="rounded" checked={showFiltered} onChange={(e) => setShowFiltered(e.target.checked)} />
                    <span>显示滤波码值</span>
                  </label>

                  <label className="flex items-center gap-2 text-sm">
                    <input type="checkbox" className="rounded" checked={showOriginal} onChange={(e) => setShowOriginal(e.target.checked)} />
                    <span>叠加原始</span>
                  </label>

                  <span className="hidden text-xs text-zinc-500 sm:inline">按 Ctrl+滚轮 缩放，拖拽平移</span>
                </div>
              </div>
              <div className="relative h-64 sm:h-96">
              <Line
                data={{
                  labels: timeAxis,
                  datasets: [
                    ...(showOriginal && rec
                      ? [
                          {
                            type: 'line' as const,
                            label: '原始码值',
                            data: rec.code,
                            borderColor: '#a1a1aa',
                            backgroundColor: 'rgba(161,161,170,0.2)',
                            borderDash: [4, 4] as any,
                            borderWidth: 1,
                            yAxisID: 'yCode',
                            pointRadius: 0,
                          },
                        ]
                      : []),
                    ...(showFiltered
                      ? [
                          {
                            type: 'line' as const,
                            label: '滤波码值',
                            data: filterType === 'none' ? rec.code : filteredCode,
                            borderColor: '#0ea5e9',
                            backgroundColor: 'rgba(14,165,233,0.2)',
                            borderWidth: 1.5,
                            yAxisID: 'yCode',
                            pointRadius: 0,
                          },
                        ]
                      : []),
                    ...(rec.fit && forceSeries
                      ? [
                          {
                            type: 'line' as const,
                            label: '力值 (mN)',
                            data: forceSeries,
                            borderColor: '#22c55e',
                            backgroundColor: 'rgba(34,197,94,0.2)',
                            borderWidth: 1.5,
                            yAxisID: 'yForce',
                            pointRadius: 0,
                          },
                        ]
                      : []),
                  ],
                }}
                options={{
                  responsive: true,
                  maintainAspectRatio: false,
                  layout: { padding: isSmall ? 0 : { left: 4, right: 12, top: 8, bottom: 4 } as any },
                  interaction: { mode: 'index', intersect: false },
                  plugins: {
                    legend: { position: (isSmall ? 'bottom' : 'top') as 'top' | 'left' | 'bottom' | 'right', labels: { font: { size: isSmall ? 10 : 12 }, boxWidth: isSmall ? 10 : 12, padding: isSmall ? 8 : 12 } },
                    zoom: {
                      pan: { enabled: true, mode: 'x' as const },
                      zoom: {
                        wheel: { enabled: true, modifierKey: 'ctrl' as const },
                        pinch: { enabled: true },
                        mode: 'x' as const,
                      },
                    },
                  },
                  scales: {
                    x: { title: { display: !isSmall, text: '时间 (ms)' }, ticks: { maxRotation: 0, font: { size: isSmall ? 10 : 12 } } },
                    yCode: { type: 'linear' as const, position: 'left' as const, title: { display: !isSmall, text: '码值' }, ticks: { font: { size: isSmall ? 10 : 12 } } },
                    yForce: { type: 'linear' as const, position: 'right' as const, title: { display: !isSmall, text: '力值 (mN)' }, grid: { drawOnChartArea: false }, ticks: { font: { size: isSmall ? 10 : 12 } } },
                  },
                }}
              />
              </div>
            </section>

            <section className="grid grid-cols-1 gap-3 sm:gap-4 sm:grid-cols-2">
              <div className="rounded-lg border p-2 sm:p-4 dark:border-zinc-800">
                <div className="mb-2 sm:mb-3 text-sm text-zinc-500">码值分布直方图</div>
                <div className="relative h-56 sm:h-80">
                <Bar
                  data={{
                    labels: codeHistogram.labels,
                    datasets: [
                      {
                        label: '频数',
                        data: codeHistogram.counts,
                        backgroundColor: 'rgba(14,165,233,0.3)',
                        borderColor: '#0ea5e9',
                      },
                    ],
                  }}
                  options={{
                    plugins: {
                      legend: { display: false },
                      zoom: {
                        pan: { enabled: true, mode: 'x' as const },
                        zoom: {
                          wheel: { enabled: true, modifierKey: 'ctrl' as const },
                          pinch: { enabled: true },
                          mode: 'x' as const,
                        },
                      },
                    },
                    responsive: true,
                    maintainAspectRatio: false,
                    layout: { padding: isSmall ? 0 : { left: 4, right: 8, top: 4, bottom: 0 } as any },
                    scales: { x: { title: { display: !isSmall, text: '码值' }, ticks: { font: { size: isSmall ? 10 : 12 } } }, y: { title: { display: !isSmall, text: '数量' }, ticks: { font: { size: isSmall ? 10 : 12 } } } },
                  }}
                />
                </div>
              </div>
              <div className="rounded-lg border p-2 sm:p-4 dark:border-zinc-800">
                <div className="mb-2 sm:mb-3 text-sm text-zinc-500">线性度散点图</div>
                {rec.fit && forceSeries ? (
                  <div className="relative h-56 sm:h-80">
                  <Scatter
                    data={{
                      datasets: [
                        {
                          label: '码值 vs 力值',
                          data: (filterType === 'none' ? rec.code : filteredCode).map((c: number, i: number) => ({ x: c, y: forceSeries[i] })),
                          backgroundColor: '#22c55e',
                        },
                      ],
                    }}
                    options={{
                      responsive: true,
                      maintainAspectRatio: false,
                      layout: { padding: isSmall ? 0 : { left: 4, right: 8, top: 4, bottom: 0 } as any },
                      scales: {
                        x: { title: { display: !isSmall, text: '码值' }, ticks: { font: { size: isSmall ? 10 : 12 } } },
                        y: { title: { display: !isSmall, text: '力值 (mN)' }, ticks: { font: { size: isSmall ? 10 : 12 } } },
                      },
                      plugins: {
                        legend: { display: false },
                        zoom: {
                          pan: { enabled: true, mode: 'x' as const },
                          zoom: {
                            wheel: { enabled: true, modifierKey: 'ctrl' as const },
                            pinch: { enabled: true },
                            mode: 'x' as const,
                          },
                        },
                      },
                    }}
                  />
                  </div>
                ) : (
                  <div className="text-sm text-zinc-500">无拟合参数，无法绘制</div>
                )}
              </div>
            </section>
          </div>
        )}
      </div>
    </div>
  )
}

function applyEMA(data: number[], alpha: number): number[] {
  if (data.length === 0) return []
  const result: number[] = [data[0]]
  for (let i = 1; i < data.length; i++) {
    result.push(alpha * data[i] + (1 - alpha) * result[i - 1])
  }
  return result
}

// ---- 进阶滤波工具函数 ----
function makeOddSafe(w: number, len: number) {
  let ww = Math.max(3, Math.min(Math.floor(w), len))
  if (ww % 2 === 0) ww = ww - 1
  if (ww < 3) ww = Math.min(len, 3)
  if (ww % 2 === 0 && ww > 1) ww = ww - 1
  return Math.max(1, ww)
}

function reflectIndex(i: number, n: number): number {
  if (n <= 1) return 0
  while (i < 0 || i >= n) {
    if (i < 0) i = -i - 1
    if (i >= n) i = 2 * n - i - 1
  }
  return i
}

function convolveReflect(data: number[], kernel: number[]): number[] {
  const n = data.length
  const m = kernel.length
  const half = Math.floor(m / 2)
  const out = new Array<number>(n)
  for (let i = 0; i < n; i++) {
    let acc = 0
    for (let k = 0; k < m; k++) {
      const idx = reflectIndex(i + k - half, n)
      acc += data[idx] * kernel[k]
    }
    out[i] = acc
  }
  return out
}

function gaussianSmooth(data: number[], sigma: number): number[] {
  if (data.length === 0) return []
  if (sigma <= 0) return data.slice()
  const radius = Math.max(1, Math.round(3 * sigma))
  const size = radius * 2 + 1
  const kernel = new Array<number>(size)
  let sum = 0
  for (let i = -radius; i <= radius; i++) {
    const v = Math.exp(-0.5 * (i * i) / (sigma * sigma))
    kernel[i + radius] = v
    sum += v
  }
  for (let i = 0; i < size; i++) kernel[i] /= sum
  return convolveReflect(data, kernel)
}

// Savitzky–Golay 实现（中心点系数 + 反射卷积）
function transpose(A: number[][]): number[][] {
  const r = A.length, c = A[0].length
  const T = Array.from({ length: c }, () => new Array<number>(r).fill(0))
  for (let i = 0; i < r; i++) for (let j = 0; j < c; j++) T[j][i] = A[i][j]
  return T
}

function matMul(A: number[][], B: number[][]): number[][] {
  const r = A.length, klen = A[0].length, c = B[0].length
  const out = Array.from({ length: r }, () => new Array<number>(c).fill(0))
  for (let i = 0; i < r; i++) {
    for (let k = 0; k < klen; k++) {
      const aik = A[i][k]
      for (let j = 0; j < c; j++) out[i][j] += aik * B[k][j]
    }
  }
  return out
}

function invertMatrix(M: number[][]): number[][] {
  const n = M.length
  const A = M.map((row) => row.slice())
  const I = Array.from({ length: n }, (_, i) => {
    const r = new Array<number>(n).fill(0)
    r[i] = 1
    return r
  })
  // Gauss-Jordan
  for (let i = 0; i < n; i++) {
    // pivot
    let pivot = A[i][i]
    if (Math.abs(pivot) < 1e-12) {
      // 找到下面非零行交换
      let swap = i + 1
      while (swap < n && Math.abs(A[swap][i]) < 1e-12) swap++
      if (swap === n) throw new Error('Matrix not invertible')
      const tmpA = A[i]; A[i] = A[swap]; A[swap] = tmpA
      const tmpI = I[i]; I[i] = I[swap]; I[swap] = tmpI
      pivot = A[i][i]
    }
    const invPivot = 1 / pivot
    for (let j = 0; j < n; j++) { A[i][j] *= invPivot; I[i][j] *= invPivot }
    for (let r = 0; r < n; r++) {
      if (r === i) continue
      const factor = A[r][i]
      if (factor === 0) continue
      for (let j = 0; j < n; j++) {
        A[r][j] -= factor * A[i][j]
        I[r][j] -= factor * I[i][j]
      }
    }
  }
  return I
}

function sgCoefficients(windowSize: number, polyOrder: number): number[] {
  const m = Math.floor(windowSize / 2)
  const rows = windowSize
  const cols = polyOrder + 1
  // 构造范德蒙德矩阵 A，x ∈ [-m, m]
  const A = Array.from({ length: rows }, (_, r) => {
    const x = r - m
    const row = new Array<number>(cols)
    let xp = 1
    for (let c = 0; c < cols; c++) { row[c] = xp; xp *= x }
    return row
  })
  const AT = transpose(A)
  const ATA = matMul(AT, A)
  const ATAi = invertMatrix(ATA)
  const pinv = matMul(ATAi, AT) // (cols x rows)
  const c = pinv[0] // 第一行对应在 x=0 处的估计系数
  return c
}

function savitzkyGolay(data: number[], windowSize: number, polyOrder: 2 | 3): number[] {
  if (data.length === 0) return []
  const w = makeOddSafe(windowSize, data.length)
  const coeff = sgCoefficients(w, polyOrder)
  return convolveReflect(data, coeff)
}

// Hampel 过滤，先去异常值，再可串联平滑
function median(arr: number[]): number {
  if (arr.length === 0) return 0
  const a = arr.slice().sort((x, y) => x - y)
  const mid = Math.floor(a.length / 2)
  return a.length % 2 === 0 ? (a[mid - 1] + a[mid]) / 2 : a[mid]
}

function hampelFilter(data: number[], windowSize: number, k: number): number[] {
  if (data.length === 0) return []
  const n = data.length
  const w = makeOddSafe(windowSize, n)
  const half = Math.floor(w / 2)
  const out = data.slice()
  for (let i = 0; i < n; i++) {
    const win: number[] = []
    for (let t = -half; t <= half; t++) win.push(data[reflectIndex(i + t, n)])
    const med = median(win)
    const absDev = win.map((v) => Math.abs(v - med))
    const mad = median(absDev)
    const s0 = (mad || 1e-12) * 1.4826
    if (Math.abs(data[i] - med) > k * s0) out[i] = med
  }
  return out
}

function buildHistogram(values: number[], bins: number) {
  if (!values.length || bins <= 0) return { labels: [] as string[], counts: [] as number[] }
  let min = values[0]
  let max = values[0]
  for (const v of values) {
    if (v < min) min = v
    if (v > max) max = v
  }
  if (min === max) {
    return { labels: [min.toFixed(2)], counts: [values.length] }
  }
  const step = (max - min) / bins
  const edges = Array.from({ length: bins + 1 }, (_, i) => min + i * step)
  const counts = Array.from({ length: bins }, () => 0)
  for (const v of values) {
    let idx = Math.floor((v - min) / step)
    if (idx >= bins) idx = bins - 1
    if (idx < 0) idx = 0
    counts[idx]++
  }
  const labels = Array.from({ length: bins }, (_, i) => `${edges[i].toFixed(1)}~${edges[i + 1].toFixed(1)}`)
  return { labels, counts }
}
