# All files / transforms heatmap.ts

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     import {range, extent} from 'd3-array'

    import {getContinuousColorScale} from './'
    import {newTable} from '../utils/newTable'
    import {X_MIN, X_MAX, Y_MIN, Y_MAX, COUNT} from '../constants/columnKeys'
    import {resolveDomain} from '../utils/resolveDomain'
    import {Table, RectLayerSpec} from '../types'

    export const heatmapTransform = (
      inputTable: Table,
      xColumnKey: string,
      yColumnKey: string,
      xDomain: number[] | null,
      yDomain: number[] | null,
      width: number,
      height: number,
      binSize: number,
      colors: string[]
    ): RectLayerSpec => {
      const resolvedXDomain = resolveDomain(
        inputTable.getColumn(xColumnKey, 'number'),
        xDomain
      )

      const resolvedYDomain = resolveDomain(
        inputTable.getColumn(yColumnKey, 'number'),
        yDomain
      )

      const table = bin2d(
        inputTable,
        xColumnKey,
        yColumnKey,
        resolvedXDomain,
        resolvedYDomain,
        width,
        height,
        binSize
      )

      const countDomain = extent(table.getColumn(COUNT, 'number'))
      const fillScale = getContinuousColorScale(countDomain, colors)

      return {
        type: 'rect',
        inputTable,
        table,
        binDimension: 'xy',
        xDomain: resolvedXDomain,
        yDomain: resolvedYDomain,
        xColumnKey,
        yColumnKey,
        xColumnType: inputTable.getColumnType(xColumnKey),
        yColumnType: 'number',
        scales: {fill: fillScale},
        columnGroupMaps: {},
      }
    }

    export const bin2d = (
      table: Table,
      xColKey: string,
      yColKey: string,
      xDomain: number[],
      yDomain: number[],
      width: number,
      height: number,
      binSize: number
    ): Table => {
      const xColData = table.getColumn(xColKey, 'number')
      const yColData = table.getColumn(yColKey, 'number')
      const xColType = table.getColumnType(xColKey) as 'time' | 'number'
      const xOriginalColType = table.getOriginalColumnType(xColKey) as
        | 'dateTime:RFC3339'
        | 'long'
        | 'double'
        | 'unsignedLong'
      const yOriginalColType = table.getOriginalColumnType(yColKey) as
        | 'dateTime:RFC3339'
        | 'long'
        | 'double'
        | 'unsignedLong'
      const yColType = table.getColumnType(yColKey) as 'time' | 'number'

      const xBinCount = Math.max(Math.floor(width / (binSize > 0 ? binSize : 1)), 1)
      const yBinCount = Math.max(
        Math.floor(height / (binSize > 0 ? binSize : 1)),
        1
      )
      // Count occurences in each bin in a `xBinCount` by `yBinCount` matrix
      //
      //                 4th y bin
      //
      //                     │
      //                     │
      //                     v
      //       [
      //           [0, 1, 2, 0, 0],
      //           [0, 1, 0, 2, 0],  <──── 2nd x bin
      //           [1, 0, 5, 7, 3]
      //       ]
      //
      const bins = range(xBinCount).map(__ => new Array(yBinCount).fill(0))

      for (let i = 0; i < table.length; i++) {
        const x = xColData[i]
        const y = yColData[i]

        const shouldSkipPoint =
          !x ||
          !y ||
          x < xDomain[0] ||
          x > xDomain[1] ||
          y < yDomain[0] ||
          y > yDomain[1]

        if (shouldSkipPoint) {
          continue
        }

        const xBinIndex = getBinIndex(x, xDomain, xBinCount)
        const yBinIndex = getBinIndex(y, yDomain, yBinCount)

        bins[xBinIndex][yBinIndex] += 1
      }

      // Now build a `Table` from that matrix

      const xBinWidth = (xDomain[1] - xDomain[0]) / xBinCount
      const yBinWidth = (yDomain[1] - yDomain[0]) / yBinCount

      const xMinData: number[] = []
      const xMaxData: number[] = []
      const yMinData: number[] = []
      const yMaxData: number[] = []
      const countData: number[] = []

      for (let i = 0; i < xBinCount; i++) {
        for (let j = 0; j < yBinCount; j++) {
          xMinData.push(xDomain[0] + i * xBinWidth)
          xMaxData.push(xDomain[0] + (i + 1) * xBinWidth)
          yMinData.push(yDomain[0] + j * yBinWidth)
          yMaxData.push(yDomain[0] + (j + 1) * yBinWidth)
          countData.push(bins[i][j])
        }
      }

      const heatmapTable = newTable(xMinData.length)
        .addColumn(X_MIN, xOriginalColType, xColType, xMinData)
        .addColumn(X_MAX, xOriginalColType, xColType, xMaxData)
        .addColumn(Y_MIN, yOriginalColType, yColType, yMinData)
        .addColumn(Y_MAX, yOriginalColType, yColType, yMaxData)
        .addColumn(COUNT, 'system', 'number', countData)

      return heatmapTable
    }

    const getBinIndex = (val: number, domain: number[], binCount: number) => {
      const domainWidth = domain[1] - domain[0]
      const percentage = (val - domain[0]) / domainWidth

      let binIndex = Math.floor(percentage * binCount)

      if (binIndex === binCount) {
        // Special case: last bin is inclusive
        binIndex = binCount - 1
      }

      return binIndex
    }