import { useCallback } from 'react'
import { useCanvas } from '../hooks/useCanvas'
import { AXIS, FONT, FRAME, GRID, formatTick, niceTicks } from '../plot'

type Props = {
  samples: Float32Array
  fs: number
  /** start of the visible window in seconds */
  startSec: number
  /** length of the visible window in seconds */
  spanSec: number
  yMax: number
  label: string
  color: string
  /** highlight this region (the zoom window) when drawing the full clip */
  highlight?: [number, number]
}

const M = { l: 48, r: 12, t: 6, b: 22 }

/** One waveform. Draws a min/max envelope when there are many samples per pixel, a line otherwise. */
export function WaveformPlot({ samples, fs, startSec, spanSec, yMax, label, color, highlight }: Props) {
  const draw = useCallback(
    (ctx: CanvasRenderingContext2D, w: number, h: number) => {
      const pw = w - M.l - M.r
      const ph = h - M.t - M.b
      const ymax = yMax > 0 ? yMax : 1
      const y0 = M.t + ph / 2
      const toY = (v: number) => y0 - (v / ymax) * (ph / 2)
      const toX = (t: number) => M.l + ((t - startSec) / spanSec) * pw

      ctx.font = FONT
      ctx.lineWidth = 1
      if (highlight) {
        ctx.fillStyle = 'rgba(31, 95, 168, 0.10)'
        const a = Math.max(M.l, toX(highlight[0]))
        const b = Math.min(M.l + pw, toX(highlight[1]))
        if (b > a) ctx.fillRect(a, M.t, b - a, ph)
      }
      ctx.strokeStyle = GRID
      ctx.fillStyle = AXIS
      ctx.textAlign = 'center'
      ctx.textBaseline = 'top'
      for (const v of niceTicks(startSec, startSec + spanSec, 6)) {
        const x = Math.round(toX(v)) + 0.5
        if (x < M.l || x > M.l + pw) continue
        ctx.beginPath()
        ctx.moveTo(x, M.t)
        ctx.lineTo(x, M.t + ph)
        ctx.stroke()
        ctx.fillText(spanSec < 0.5 ? `${formatTick(v * 1000)}` : formatTick(v), x, M.t + ph + 4)
      }
      ctx.textAlign = 'right'
      ctx.textBaseline = 'middle'
      ctx.fillText(formatTick(ymax), M.l - 5, toY(ymax))
      ctx.fillText('0', M.l - 5, y0)
      ctx.fillText(formatTick(-ymax), M.l - 5, toY(-ymax))
      ctx.strokeStyle = '#b8bcc2'
      ctx.beginPath()
      ctx.moveTo(M.l, Math.round(y0) + 0.5)
      ctx.lineTo(M.l + pw, Math.round(y0) + 0.5)
      ctx.stroke()
      ctx.strokeStyle = FRAME
      ctx.strokeRect(M.l + 0.5, M.t + 0.5, pw, ph)
      ctx.fillStyle = AXIS
      ctx.textAlign = 'right'
      ctx.textBaseline = 'bottom'
      ctx.fillText(spanSec < 0.5 ? 'ms' : 's', M.l + pw, h - 1)

      const i0 = Math.max(0, Math.floor(startSec * fs))
      const i1 = Math.min(samples.length, Math.ceil((startSec + spanSec) * fs))
      const perPx = (i1 - i0) / pw
      ctx.save()
      ctx.beginPath()
      ctx.rect(M.l, M.t, pw, ph)
      ctx.clip()
      ctx.strokeStyle = color
      ctx.fillStyle = color
      ctx.lineWidth = 1.2
      ctx.lineJoin = 'round'
      if (perPx > 2) {
        // min/max envelope per pixel column
        for (let px = 0; px < pw; px++) {
          const a = i0 + Math.floor(px * perPx)
          const b = Math.min(i1, i0 + Math.floor((px + 1) * perPx))
          if (b <= a) continue
          let lo = Infinity
          let hi = -Infinity
          for (let i = a; i < b; i++) {
            const v = samples[i]
            if (v < lo) lo = v
            if (v > hi) hi = v
          }
          const yTop = toY(hi)
          const yBot = toY(lo)
          ctx.fillRect(M.l + px, yTop, 1, Math.max(1, yBot - yTop))
        }
      } else {
        ctx.beginPath()
        for (let i = i0; i < i1; i++) {
          const px = toX(i / fs)
          const py = toY(samples[i])
          if (i === i0) ctx.moveTo(px, py)
          else ctx.lineTo(px, py)
        }
        ctx.stroke()
      }
      ctx.restore()

      ctx.fillStyle = color
      ctx.font = 'bold 12px system-ui, sans-serif'
      ctx.textAlign = 'left'
      ctx.textBaseline = 'top'
      ctx.fillText(label, M.l + 6, M.t + 4)
    },
    [samples, fs, startSec, spanSec, yMax, label, color, highlight],
  )
  const ref = useCanvas(draw)
  return <canvas ref={ref} className="plot waveform-plot" />
}