import { useCallback } from 'react'
import { useCanvas } from '../hooks/useCanvas'
import { renderPeriod } from '../synth'

type Props = {
  amplitudes: number[]
  /** radians */
  phases: number[]
  color: string
  /** vertical half-range; pass the same value for both tones so they share a scale */
  yMax: number
}

const M = { l: 40, r: 10, t: 10, b: 22 }

/** One period of the waveform x(t), unscaled. */
export function WaveformPlot({ amplitudes, phases, color, yMax }: 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 y0 = M.t + ph / 2
      const ymax = yMax > 0 ? yMax : 1
      const toY = (v: number) => y0 - (v / ymax) * (ph / 2)

      ctx.font = '11px system-ui, sans-serif'
      ctx.fillStyle = '#666'
      ctx.strokeStyle = '#ddd'
      ctx.lineWidth = 1

      // frame and zero line
      ctx.strokeRect(M.l + 0.5, M.t + 0.5, pw, ph)
      ctx.beginPath()
      ctx.moveTo(M.l, y0 + 0.5)
      ctx.lineTo(M.l + pw, y0 + 0.5)
      ctx.stroke()
      // quarter-period grid
      for (let q = 1; q < 4; q++) {
        const x = Math.round(M.l + (pw * q) / 4) + 0.5
        ctx.beginPath()
        ctx.moveTo(x, M.t)
        ctx.lineTo(x, M.t + ph)
        ctx.stroke()
      }

      // ticks
      ctx.textAlign = 'right'
      ctx.textBaseline = 'middle'
      ctx.fillText(ymax.toFixed(1), M.l - 4, toY(ymax))
      ctx.fillText('0', M.l - 4, y0)
      ctx.fillText((-ymax).toFixed(1), M.l - 4, toY(-ymax))
      ctx.textAlign = 'center'
      ctx.textBaseline = 'top'
      ctx.fillText('0', M.l, M.t + ph + 4)
      ctx.fillText('T/2', M.l + pw / 2, M.t + ph + 4)
      ctx.fillText('T', M.l + pw, M.t + ph + 4)

      // curve
      const n = Math.max(64, Math.round(pw * 2))
      const y = renderPeriod(amplitudes, phases, n)
      ctx.strokeStyle = color
      ctx.lineWidth = 1.8
      ctx.lineJoin = 'round'
      ctx.beginPath()
      for (let i = 0; i <= n; i++) {
        const px = M.l + (pw * i) / n
        const py = toY(y[i % n])
        if (i === 0) ctx.moveTo(px, py)
        else ctx.lineTo(px, py)
      }
      ctx.stroke()
    },
    [amplitudes, phases, color, yMax],
  )
  const ref = useCanvas(draw)
  return <canvas ref={ref} className="plot waveform-plot" />
}