1/**
 2 * @module Color range generator
 3 *
 4 */
 5
 6function calculatePoint(i: number, intervalSize: number, colorRangeInfo: ColorRange) {
 7    const { colorStart, colorEnd, useEndAsStart } = colorRangeInfo;
 8    return (useEndAsStart
 9        ? (colorEnd - (i * intervalSize))
10        : (colorStart + (i * intervalSize)));
11}
12
13/* Must use an interpolated color scale, which has a range of [0, 1] */
14interface ColorRange {
15    colorStart: number;
16    colorEnd: number;
17    useEndAsStart: boolean;
18}
19
20/**
21 * @param dataLength - Number of colors to be generated
22 * @param colorScale - The D3 interpolate color scale 
23 * @param colorRangeInfo - Color range spectrum
24 * @returns An array of colors within the choosen spectrum
25 *
26 * @description 
27 *  - Must use an interpolated color scale, which has a range of [0, 1].
28 *  - D3 Interpolators are interpolateInfero, interpolateCool, interpolateRainbow, interpolateSpectral, interpolateRdYlBu
29 */
30export function interpolateColors(dataLength: number, colorScale: (c: number) => string, colorRangeInfo: ColorRange) {
31    const { colorStart, colorEnd } = colorRangeInfo;
32    const colorRange = colorEnd - colorStart;
33    const intervalSize = colorRange / dataLength;
34    let i, colorPoint;
35    const colorArray = [];
36
37    for (i = 0; i < dataLength; i++) {
38        colorPoint = calculatePoint(i, intervalSize, colorRangeInfo);
39        colorArray.push(colorScale(colorPoint));
40    }
41
42    return colorArray;
43}