import { Spec } from 'vega';

export const spec: Spec = {
  $schema: 'https://vega.github.io/schema/vega/v5.json',
  width: 400,
  height: 300,
  padding: 5,
  autosize: 'pad',

  signals: [
    {
      name: 'bandwidth',
      value: -1,
      bind: { input: 'range', min: -1, max: 100, step: 1 }
    },
    {
      name: 'resolve',
      value: 'shared',
      bind: { input: 'select', options: ['independent', 'shared'] }
    },
    {
      name: 'counts',
      value: true,
      bind: { input: 'checkbox' }
    }
  ],

  data: [
    {
      name: 'source',
      url: 'data/cars.json',
      transform: [
        {
          type: 'filter',
          expr: 'datum.Horsepower != null && datum.Miles_per_Gallon != null && datum.Acceleration != null'
        }
      ]
    },
    {
      name: 'density',
      source: 'source',
      transform: [
        {
          type: 'kde2d',
          groupby: ['Origin'],
          size: [{ signal: 'width' }, { signal: 'height' }],
          x: { expr: "scale('x', datum.Horsepower)" },
          y: { expr: "scale('y', datum.Miles_per_Gallon)" },
          bandwidth: { signal: '[bandwidth, bandwidth]' },
          counts: { signal: 'counts' }
        }
      ]
    },
    {
      name: 'contours',
      source: 'density',
      transform: [
        {
          type: 'isocontour',
          field: 'grid',
          resolve: { signal: 'resolve' },
          levels: 3
        }
      ]
    }
  ],

  scales: [
    {
      name: 'x',
      type: 'linear',
      round: true,
      nice: true,
      zero: true,
      domain: { data: 'source', field: 'Horsepower' },
      range: 'width'
    },
    {
      name: 'y',
      type: 'linear',
      round: true,
      nice: true,
      zero: true,
      domain: { data: 'source', field: 'Miles_per_Gallon' },
      range: 'height'
    },
    {
      name: 'color',
      type: 'ordinal',
      domain: {
        data: 'source',
        field: 'Origin',
        sort: { order: 'descending' }
      },
      range: 'category'
    }
  ],

  axes: [
    {
      scale: 'x',
      grid: true,
      domain: false,
      orient: 'bottom',
      tickCount: 5,
      title: 'Horsepower'
    },
    {
      scale: 'y',
      grid: true,
      domain: false,
      orient: 'left',
      titlePadding: 5,
      title: 'Miles_per_Gallon'
    }
  ],

  legends: [{ stroke: 'color', symbolType: 'stroke' }],

  marks: [
    {
      name: 'marks',
      type: 'symbol',
      from: { data: 'source' },
      encode: {
        update: {
          x: { scale: 'x', field: 'Horsepower' },
          y: { scale: 'y', field: 'Miles_per_Gallon' },
          size: { value: 4 },
          fill: { value: '#ccc' }
        }
      }
    },
    {
      type: 'image',
      from: { data: 'density' },
      encode: {
        update: {
          x: { value: 0 },
          y: { value: 0 },
          width: { signal: 'width' },
          height: { signal: 'height' },
          aspect: { value: false }
        }
      },
      transform: [
        {
          type: 'heatmap',
          field: 'datum.grid',
          resolve: { signal: 'resolve' },
          color: { expr: "scale('color', datum.datum.Origin)" }
        }
      ]
    },
    {
      type: 'path',
      clip: true,
      from: { data: 'contours' },
      encode: {
        enter: {
          strokeWidth: { value: 1 },
          strokeOpacity: { value: 1 },
          stroke: { scale: 'color', field: 'Origin' }
        }
      },
      transform: [{ type: 'geopath', field: 'datum.contour' }]
    }
  ]
};
