import { useCallback, useEffect, useRef, useState } from 'react'
import uPlot, { type AlignedData, type Options } from 'uplot'
import 'uplot/dist/uPlot.min.css'

export interface ChartSeries {
  label: string
  values: (number | null)[]
  /** CSS 变量名，例如 --chart-1。 */
  color: string
  dash?: number[]
  fill?: boolean
  /** 原始数据的淡线（开了 EWMA 平滑时垫在平滑线后面）：画细、画淡，图例和提示框里不出现。 */
  faint?: boolean
}

interface Props {
  /** 时间轴，Unix 毫秒。 */
  t: number[]
  series: ChartSeries[]
  height?: number
  /** Y 轴的单位后缀（ms、%）。 */
  unit?: string
  /** 为真时 Y 轴从 0 开始。 */
  zero?: boolean
  /** 缺口：这些时间段用底色标出。 */
  gaps?: { from: number; to: number }[]
  /** 为真时 `t` 是「从起点算起的毫秒数」而不是 Unix 毫秒：横轴显示 0:00、0:15…，用来把两段时间叠在一起比。 */
  offset?: boolean
}

/** 偏移量（毫秒）→ h:mm:ss / m:ss。 */
export function fmtOffset(ms: number): string {
  const total = Math.round(ms / 1000)
  const h = Math.floor(total / 3600)
  const m = Math.floor((total % 3600) / 60)
  const sec = total % 60
  const two = (n: number) => String(n).padStart(2, '0')
  return h > 0 ? `${h}:${two(m)}${sec ? ':' + two(sec) : ''}` : `${m}:${two(sec)}`
}

function cssVar(name: string): string {
  return getComputedStyle(document.documentElement).getPropertyValue(name).trim()
}

/** 毫秒到 1 秒以上换成秒（30000ms → 30s），坐标轴和提示框都不会出现一长串数字。 */
function withUnit(v: number, unit: string, digits?: number): string {
  if (unit === 'ms' && Math.abs(v) >= 1000) return `${digits === undefined ? +(v / 1000).toFixed(1) : (v / 1000).toFixed(digits)}s`
  return `${v}${unit}`
}

function formatValue(v: number | null | undefined, unit: string): string {
  if (v === null || v === undefined) return '—'
  if (unit === 'ms' && Math.abs(v) >= 1000) return withUnit(v, unit, 2)
  const text = Math.abs(v) >= 100 ? v.toFixed(0) : Math.abs(v) >= 10 ? v.toFixed(1) : v.toFixed(2)
  return `${text}${unit}`
}

/**
 * uPlot 的封装：
 * - 跟随主题（明暗切换时重绘）和容器宽度，空值断线；
 * - 在图上拖动选一段放大预览，双击或点「还原」恢复；数据刷新时保持放大的区间；
 * - 鼠标悬停显示这个时刻每条线的值。
 */
export function TimeChart({ t, series, height = 220, unit = '', zero = true, gaps = [], offset = false }: Props) {
  const host = useRef<HTMLDivElement>(null)
  const tip = useRef<HTMLDivElement>(null)
  const plot = useRef<uPlot | null>(null)
  const zoom = useRef<{ min: number; max: number } | null>(null)
  const [zoomed, setZoomed] = useState(false)
  // 数据变了（轮询、实时）只更新数据，不重建图：重建会闪一下，还会丢掉鼠标位置
  const latest = useRef({ t, series, gaps })
  latest.current = { t, series, gaps }
  const structure = JSON.stringify([series.map((x) => [x.label, x.color, x.dash, x.fill, x.faint]), unit, zero, offset, height])
  const dataOf = (): AlignedData => [latest.current.t.map((v) => v / 1000), ...latest.current.series.map((x) => x.values.map((v) => (v === null ? null : v)))]

  const reset = useCallback(() => {
    zoom.current = null
    setZoomed(false)
    const u = plot.current
    if (u && u.data[0].length > 0) u.setScale('x', { min: u.data[0][0], max: u.data[0][u.data[0].length - 1] })
  }, [])

  useEffect(() => {
    const el = host.current
    if (!el) return
    const build = () => {
      plot.current?.destroy()
      const axis = cssVar('--chart-axis')
      const grid = cssVar('--chart-grid')
      const font = '12px ' + (cssVar('--font-sans') || 'sans-serif')
      const shade = cssVar('--app-warn-container')
      const options: Options = {
        width: el.clientWidth || 600,
        height,
        legend: { show: false },
        cursor: { drag: { x: true, y: false, setScale: false }, points: { size: 6 } },
        select: { show: true, left: 0, top: 0, width: 0, height: 0 },
        scales: {
          x: { time: !offset, range: (_u, min, max) => (zoom.current ? [zoom.current.min, zoom.current.max] : [min, max]) },
          y: { range: (_u, min, max) => [zero ? Math.min(0, min) : min, max <= min ? min + 1 : max + (max - min) * 0.08] },
        },
        axes: [
          { stroke: axis, grid: { stroke: grid, width: 1 }, ticks: { stroke: grid }, font, ...(offset ? { values: (_u: uPlot, ticks: number[]) => ticks.map((v) => fmtOffset(v * 1000)) } : {}) },
          { stroke: axis, grid: { stroke: grid, width: 1 }, ticks: { show: false }, font, size: 56, values: (_u, ticks) => ticks.map((v) => withUnit(v, unit)) },
        ],
        series: [
          {},
          ...series.map((s) => {
            const color = cssVar(s.color)
            return {
              label: s.label,
              stroke: s.faint ? color + '55' : color,
              width: s.faint ? 1 : 1.8,
              dash: s.dash,
              fill: s.fill ? color + '22' : undefined,
              spanGaps: false,
              points: { show: false },
            }
          }),
        ],
        hooks: {
          ready: [
            (u) => {
              u.over.addEventListener('dblclick', reset)
            },
          ],
          setSelect: [
            (u) => {
              if (u.select.width < 6) return
              const min = u.posToVal(u.select.left, 'x')
              const max = u.posToVal(u.select.left + u.select.width, 'x')
              if (max - min < 5) return
              zoom.current = { min, max }
              setZoomed(true)
              u.setSelect({ left: 0, top: 0, width: 0, height: 0 }, false)
              u.setScale('x', { min, max })
            },
          ],
          setCursor: [
            (u) => {
              const box = tip.current
              if (!box) return
              const idx = u.cursor.idx
              if (idx === null || idx === undefined || (u.cursor.left ?? -1) < 0) {
                box.style.display = 'none'
                return
              }
              const when = new Date(u.data[0][idx] * 1000)
              const lines = [offset ? `起点后 ${fmtOffset(u.data[0][idx] * 1000)}` : when.toLocaleString('zh-CN', { hour12: false, month: '2-digit', day: '2-digit', hour: '2-digit', minute: '2-digit', second: '2-digit' })]
              for (let i = 0; i < latest.current.series.length; i++) if (!latest.current.series[i].faint) lines.push(`${latest.current.series[i].label}  ${formatValue(u.data[i + 1][idx], unit)}`)
              box.textContent = lines.join('\n')
              box.style.display = 'block'
              const width = box.offsetWidth
              const left = (u.cursor.left ?? 0) + 14
              box.style.left = `${left + width > u.over.clientWidth ? Math.max(0, (u.cursor.left ?? 0) - width - 14) : left}px`
              box.style.top = '8px'
            },
          ],
          drawClear: [
            (u) => {
              const { ctx } = u
              ctx.save()
              ctx.fillStyle = shade
              for (const g of latest.current.gaps) {
                const x0 = Math.max(u.bbox.left, u.valToPos(g.from / 1000, 'x', true))
                const x1 = Math.min(u.bbox.left + u.bbox.width, u.valToPos(g.to / 1000, 'x', true))
                if (x1 > x0) ctx.fillRect(x0, u.bbox.top, x1 - x0, u.bbox.height)
              }
              ctx.restore()
            },
          ],
        },
      }
      plot.current = new uPlot(options, dataOf(), el)
      // 把提示框放进绘图区，这样它的位置和光标是同一个坐标系
      if (tip.current) plot.current.over.appendChild(tip.current)
    }
    build()
    const resize = new ResizeObserver(() => plot.current?.setSize({ width: el.clientWidth, height }))
    resize.observe(el)
    const theme = new MutationObserver(build)
    theme.observe(document.documentElement, { attributes: true, attributeFilter: ['data-theme'] })
    return () => {
      resize.disconnect()
      theme.disconnect()
      plot.current?.destroy()
      plot.current = null
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [structure, reset])

  useEffect(() => {
    const u = plot.current
    if (!u) return
    u.setData(dataOf(), !zoom.current)
    u.redraw(false)
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [t, series, gaps])

  return (
    <div className="chart-wrap">
      <div className="chart-legend">
        {series.filter((s) => !s.faint).map((s) => (
          <span key={s.label}>
            <i style={{ background: `var(${s.color})` }} />
            {s.label}
          </span>
        ))}
        <span className="chart-hint">
          {zoomed ? (
            <button type="button" className="btn small text" onClick={reset}>
              还原缩放
            </button>
          ) : (
            '拖动选择一段放大，双击还原'
          )}
        </span>
      </div>
      <div ref={host} className="chart" />
      <div ref={tip} className="chart-tip" />
    </div>
  )
}