# All files / utils getTicks.ts

95.69% Statements 89/93
89.28% Branches 50/56
100% Functions 9/9
95.29% Lines 81/85

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     // Libraries
    import {scaleUtc} from 'd3-scale'
    import {ticks} from 'd3-array'
    import memoizeOne from 'memoize-one'

    // Types
    import {AxisTicks, Formatter, FormatterType} from '../types'

    // Constants
    import {TIME, VALUE} from '../constants/columnKeys'
    import {TICK_COUNT_LIMIT} from '../constants'

    // Utils
    import {getTextMetrics} from './textMetrics'
    import {isFiniteNumber} from './isFiniteNumber'

    /*
      Minimum spacing defined as:
        I. when there are less than 4 ticks:
          for each tick, spacing is one-quarter of the length of a tick
          thusly: 0.25, 0.50, 0.75 of a tick's length as spacing for 1, 2, and 3 ticks respectively
        II. when there are 4 to 10 ticks:
          sum of all tick lengths is shorter than total available space by at least one tick's length
        III. when there are more than 10 ticks:
          for every group of up to 10 ticks there is spacing equal at least 1 tick's length
        IV. length of a tick is:
             vertical axis - the average of the height and width of a span that wraps the formatted last tick in the range
             horizontal axis - the width of a span that wraps the formatted last tick in the range
    */
    const hasMinimumSpacing = (
      rangeLength: number,
      timeTickLength: number,
      ticks: AxisTicks
    ): boolean => {
      const fractionalSpaceAsPadding = 0.25
      const totalLength = ticks.length * timeTickLength
      if (ticks.length < 4) {
        const padding = totalLength * fractionalSpaceAsPadding
        if (totalLength < rangeLength - padding) {
          return true
        }
        return false
      } else if (ticks.length <= 10) {
        if (totalLength < rangeLength - timeTickLength) {
          return true
        }
        return false
      } else if (
        totalLength <
        rangeLength - Math.ceil(ticks.length / 10) * timeTickLength
      ) {
        return true
      }
      return false
    }

    /*
      Optimal number of ticks is defined as:
      I. allow d3 to choose the ticks and
      II. meets minimum spacing requirements checked by hasMinimumSpacing
    */
    const getOptimalTicks = (
      [d0, d1]: number[],
      rangeLength: number,
      tickLength: number
    ): number[] => {
      const maxNumTicks = Math.floor(rangeLength / tickLength)
      let optimalTicks = ticks(d0, d1, maxNumTicks)

      for (
        let counter = 1;
        counter < maxNumTicks &&
        !hasMinimumSpacing(rangeLength, tickLength, optimalTicks);
        counter += 1
      ) {
        optimalTicks = ticks(d0, d1, maxNumTicks - counter)
      }
      return optimalTicks
    }

    /*
      Similar to getOptimalTicks but for Date objects
    */
    const getOptimalTimeTicks = (
      [d0, d1]: number[],
      rangeLength: number,
      timeTickLength: number
    ): Date[] => {
      const scaledTime = scaleUtc()
        .domain([d0, d1])
        .range([0, rangeLength])
      const maxNumTicks = Math.floor(rangeLength / timeTickLength)
      let optimalTicks = scaledTime.ticks(maxNumTicks)

      for (
        let counter = 1;
        counter < maxNumTicks &&
        !hasMinimumSpacing(rangeLength, timeTickLength, optimalTicks);
        counter += 1
      ) {
        optimalTicks = scaledTime.ticks(maxNumTicks - counter)
      }
      return optimalTicks
    }

    // calculateTicks adheres to spacing requirements as described in helper functions above
    export const calculateTicks = (
      domain: number[],
      rangeLength: number,
      tickSize: number,
      columnKey: string
    ): number[] => {
      return columnKey === TIME
        ? getOptimalTimeTicks(domain, rangeLength, tickSize).map(d => d.getTime())
        : getOptimalTicks(domain, rangeLength, tickSize)
    }

    /*
      generateTicks gives control to the user over placement, number, and interval of ticks
        defers to the user's judgement on spacing (tick labels may overlap)
    */
    export const generateTicks = (
      domain: number[],
      columnKey: string,
      totalTicks: number,
      tickStart: number,
      tickStep: number
    ): number[] => {
      const generatedTicks = []
      const [start = 0, end = 0] = domain
      const stepStart = isFiniteNumber(tickStart) ? tickStart : start

      let step = tickStep
      if (!isFiniteNumber(tickStep)) {
        const parts =
          isFiniteNumber(totalTicks) && totalTicks !== 0 ? totalTicks : 1
        step = (end - stepStart) / (isFiniteNumber(tickStart) ? parts : parts + 1)
      }

      const tickCountLimit = isFiniteNumber(totalTicks)
        ? Math.min(totalTicks, TICK_COUNT_LIMIT)
        : TICK_COUNT_LIMIT

      let counter = isFiniteNumber(tickStart) ? 0 : 1
      let generatedTick = stepStart + step * counter

      if (
        tickStep !== 0 &&
        (isFiniteNumber(totalTicks) || isFiniteNumber(tickStep))
      ) {
        /*
          - When 'step' marks the ticks to the right (or up) on the axis
            it is a positive number and should stop at 'end'
          - When 'step' marks the ticks to the left (or down) on the axis
            it is a negative number and should stop at 'start'
        */
        while (
          ((step > 0 && generatedTick <= end) ||
            (step < 0 && generatedTick >= start)) &&
          generatedTicks.length < tickCountLimit
        ) {
          if (generatedTick >= start && generatedTick <= end) {
            if (columnKey === TIME) {
              generatedTicks.push(new Date(generatedTick))
            } else {
              generatedTicks.push(generatedTick)
            }
          }
          counter += 1
          generatedTick = stepStart + step * counter
        }
      }
      return generatedTicks
    }

    /*
      ticks can be either
        - generated: user's defined parameters and judgmenet for spacing
        - calculated: Giraffe's determination and spacing requirements
    */
    const getTicks = (
      domain: number[],
      rangeLength: number,
      tickSize: number,
      columnKey: string,
      totalTicks?: number,
      tickStart?: number,
      tickStep?: number
    ) => {
      const [start = 0, end = 0] = domain
      Iif (isFiniteNumber(totalTicks) || isFiniteNumber(tickStep)) {
        return generateTicks(domain, columnKey, totalTicks, tickStart, tickStep)
      }
      Iif (isFiniteNumber(tickStart)) {
        const specifiedTickStart = Math.min(Math.max(tickStart, start), end)
        return calculateTicks(
          [specifiedTickStart, end],
          rangeLength,
          tickSize,
          columnKey
        )
      }
      return calculateTicks(domain, rangeLength, tickSize, columnKey)
    }

    /*
      for performance memoize both the original arguments and calculated arguments
        keep this separate from a memoized horizontal version
    */
    const getMemoizedVerticalTicks = memoizeOne(getTicks)
    export const getVerticalTicks = memoizeOne(
      (
        domain: number[],
        rangeLength: number,
        tickFont: string,
        formatter: Formatter,
        totalTicks?: number,
        tickStart?: number,
        tickStep?: number
      ): number[] => {
        const sampleTick = formatter(domain[1])
        const tickTextMetrics = getTextMetrics(tickFont, sampleTick)

        const maxTickHeight = 5 * tickTextMetrics.height
        const tickHeight = Math.min(
          tickTextMetrics.height + tickTextMetrics.width / 2,
          maxTickHeight
        )
        const columnKey =
          formatter._GIRAFFE_FORMATTER_TYPE === FormatterType.Time ? TIME : VALUE

        return getMemoizedVerticalTicks(
          domain,
          rangeLength,
          tickHeight,
          columnKey,
          totalTicks,
          tickStart,
          tickStep
        )
      }
    )

    /*
      for performance memoize both the original arguments and calculated arguments
        keep this separate from a memoized vertical version
    */
    const getMemoizedHorizontalTicks = memoizeOne(getTicks)
    export const getHorizontalTicks = memoizeOne(
      (
        domain: number[],
        rangeLength: number,
        tickFont: string,
        formatter: Formatter,
        totalTicks?: number,
        tickStart?: number,
        tickStep?: number
      ): number[] => {
        const sampleTick = formatter(domain[1])
        const tickTextMetrics = getTextMetrics(tickFont, sampleTick)

        const columnKey =
          formatter._GIRAFFE_FORMATTER_TYPE === FormatterType.Time ? TIME : VALUE

        return getMemoizedHorizontalTicks(
          domain,
          rangeLength,
          tickTextMetrics.width,
          columnKey,
          totalTicks,
          tickStart,
          tickStep
        )
      }
    )