Golden Ratio

#includepath "~/Documents/;%USERPROFILE%Documents"; // eslint-disable-line
#include "basiljs/bundle/basil.js"; // eslint-disable-line
// A simple sketch makes use of the goldenRatio
//
/**
 * A sample function that shows how to calculate the golden ratio
 * The logic is extracted from https://jumk.de/goldener-schnitt/
 * by Jürgen Kummer
 * It tries to catch errors made by the user but the usage should be:
 *
 * Provide a value for a or b or ab
 *
 * @param  {Number} a  value a the bigger of the two
 * @param  {Number} b  value b the smaller of the two
 * @param  {Number} ab the sum of a + b
 * @return {Object}    Returns an object like this {a: Number, b: Number, ab: Number};
 */
function goldenRatio(a, b, ab) {
  // phi or φ https://de.wikipedia.org/wiki/Phi
  var φ = 1.6180339887498948; // this is phi
  if (a === null && b === null && ab === null) {
    // if no value is given return an error
    return Error('No values given.\nPlease provide just one value for a or b or ab');
  } else if (
    (a !== null && b !== null) || (a !== null && ab !== null) || (b !== null && ab !== null)) {
    // if more then one value is given return an error
    return Error('To many values.\nPlease provide just one value for a or b or ab');
  }
  // now we only have one value.
  // lets calc the according others
  //
  if (a !== null) {
    // a is given
    b = null;
    ab = null;
    b = a / φ;
    ab = a + b;
  } else if (b !== null) {
    // b is given
    a = null;
    ab = null;
    a = φ * b;
    ab = a + b;
  } else if (ab !== null) {
    // ab is given
    a = null;
    b = null;
    a = ab / φ;
    b = a / φ;
  }
  // give back the result
  return {
    a: a,
    b: b,
    ab: ab
  };
};

function draw() {
  var rectWidth = b.random(123, 234); // this is some random number as basis for the calculation
  var ratio = goldenRatio(rectWidth, null, null); // calc the ratio for that
  // some error testing. Actually not needed if you use the
  // goldenRatio function right
  if (ratio instanceof Error) {
    b.println(ratio); // we had an error ;-|
    return -1; // end that whole sketch
  }
  var pw = ratio.ab; // get the ratio for the whole page
  var phratio = goldenRatio(null, ratio.a, null); // calc the ratio for the height
  var ph = phratio.ab; // set the height
  b.clear(b.doc()); // clear the current document
  b.units(b.MM); // we want to print. use MM instead of default pixels
  var doc = b.doc(); // a reference to the current document
  // set some preferneces of the document for better handling
  doc.documentPreferences.properties = {
    pageWidth: pw,
    pageHeight: ph
  }; // set the page size
  doc.viewPreferences.rulerOrigin = RulerOrigin.SPREAD_ORIGIN; // upper left corner
  // ----------
  // main code goes here
  b.noStroke(); // we want no stroke
  b.fill(255); // font color
  b.textFont('Akko Rounded Pro\tThin'); // does this throw an error if the font is not present?
  var r1 = b.rect(0, 0, ratio.a, ratio.a); // the first rectangle
  var r2 = b.rect(ratio.a, 0, ratio.b, ratio.b); // the second rectangle
  var tfa = b.text('A', ratio.a - 10, (ratio.a) - 10, 10, 10); // the text for value a
  var tfb = b.text('B', ratio.ab - 10, (ratio.b) - 10, 10, 10); // text for value b
  var tfab = b.text('AB', ratio.ab - 10, 5, 10, 10); // text for value ab
  // the 0.25 is visual sugar to prevent a minimal white gap
  var bleedfix = 0.25; // to fix bleeding
  b.stroke(255); // white lines
  // start the first line
  b.beginShape();
  b.vertex(0 - bleedfix, 0); // left
  b.vertex(ratio.ab + bleedfix, 0); // right
  var lineab = b.endShape(); // save it
  b.beginShape(); // start the econd line
  b.vertex(0 - bleedfix, ratio.a); // left
  b.vertex(ratio.a + 0.25, ratio.a); // right
  var linea = b.endShape(); // save it
  b.beginShape(); // start the third line
  b.vertex(ratio.a, ratio.b); // left
  b.vertex(ratio.ab + bleedfix, ratio.b); // right
  var lineb = b.endShape(); // save it
  // some properties for all the lines
  // also visual sugar
  var props = {
    strokeTint: 50,
    strokeWeight: 5,
    leftLineEnd: ArrowHead.BAR_ARROW_HEAD,
    rightLineEnd: ArrowHead.BAR_ARROW_HEAD
  };
  linea.properties = props; // set it
  lineb.properties = props; // set it
  lineab.properties = props; // set it
  r1.fillColor = doc.swatches[4]; // set the fill color for the first rectangle
  r2.fillColor = doc.swatches[5]; // and the fill for the second
  // ----------
  // get the name, save the file and export a PNG
  var fname = File($.fileName).parent.fsName + '/' + ($.fileName.split('/')[$.fileName.split('/').length - 1]).split('.')[0] + '.indd';
  // b.println(fname);
  doc.save(fname, false, 'basil', true);
  b.savePNG('out.png');
} // end of draw
b.go(); // run it