import React from 'react'
import ReactApexChart from 'react-apexcharts'
import './styles.css'

// ── Reproducible synthetic data (seeded PRNG, no network) ──────────────
function mulberry32(a) {
  return function () {
    a |= 0
    a = (a + 0x6d2b79f5) | 0
    var t = Math.imul(a ^ (a >>> 15), 1 | a)
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296
  }
}
var rng = mulberry32(24681012)

function gauss(mean, sd) {
  var u = 0,
    v = 0
  while (u === 0) u = rng()
  while (v === 0) v = rng()
  return mean + sd * Math.sqrt(-2 * Math.log(u)) * Math.cos(2 * Math.PI * v)
}

// Draw n samples from a mixture of two well-separated normal components — the
// two clusters give each distribution its characteristic twin-hump shape.
function bimodal(n, a, b) {
  var out = []
  for (var i = 0; i < n; i++) {
    var c = rng() < a.w ? a : b
    out.push(Math.max(0, Math.round(gauss(c.mean, c.sd) * 10) / 10))
  }
  return out
}

// Session duration (minutes) per channel — a quick-bounce cluster and an
// engaged-visit cluster, mixed in different proportions.
var CHANNELS = [
  {
    name: 'Direct',
    data: bimodal(320, { w: 0.4, mean: 2, sd: 1 }, { mean: 22, sd: 5 }),
  },
  {
    name: 'Search',
    data: bimodal(320, { w: 0.55, mean: 2, sd: 1 }, { mean: 18, sd: 5 }),
  },
  {
    name: 'Social',
    data: bimodal(320, { w: 0.7, mean: 2, sd: 1 }, { mean: 14, sd: 4 }),
  },
  {
    name: 'Email',
    data: bimodal(320, { w: 0.3, mean: 3, sd: 1.5 }, { mean: 26, sd: 6 }),
  },
]

// Gaussian KDE with a loose bandwidth + coarse step, so the two humps stay
// distinct (a tighter bandwidth would smear them into one) and the outline
// keeps its angular, twin-peaked character.
function kde(values, bw, step) {
  var min = Math.min.apply(null, values) - bw
  var max = Math.max.apply(null, values) + bw
  var N = values.length
  var profile = []
  for (var x = min; x <= max; x += step) {
    var sum = 0
    for (var k = 0; k < N; k++) {
      var d = (x - values[k]) / bw
      sum += Math.exp(-0.5 * d * d)
    }
    profile.push([Math.round(x * 100) / 100, sum / (N * bw)])
  }
  return profile
}

const ApexChart = () => {
  const [state, setState] = React.useState({
    series: [
      {
        name: 'Sessions',
        data: CHANNELS.map(function (c) {
          return {
            x: c.name,
            y: { density: kde(c.data, 2.5, 1.5), points: c.data },
          }
        }),
      },
    ],
    options: {
      chart: {
        type: 'violin',
        height: 480,
      },
      title: {
        text: 'Session duration by channel',
      },
      plotOptions: {
        bar: {
          horizontal: true,
          distributed: true,
        },
        violin: {
          normalize: 'group',
          points: { show: false }, // density curves only
        },
      },
      colors: ['#0ea5e9', '#8b5cf6', '#f97316', '#10b981'],
      stroke: { width: 1, colors: ['#888'] },
      legend: { show: false },
      xaxis: {
        title: { text: 'Session duration (minutes)' },
      },
    },
  })

  return (
    <div>
      <div id="chart">
        <ReactApexChart
          options={state.options}
          series={state.series}
          type="violin"
          height={480}
        />
      </div>
    </div>
  )
}

export default ApexChart