source: node_modules/d3-hierarchy/src/treemap/squarify.js@ e4c61dd

import treemapDice from "./dice.js";
import treemapSlice from "./slice.js";

export var phi = (1 + Math.sqrt(5)) / 2;

export function squarifyRatio(ratio, parent, x0, y0, x1, y1) {
  var rows = [],
      nodes = parent.children,
      row,
      nodeValue,
      i0 = 0,
      i1 = 0,
      n = nodes.length,
      dx, dy,
      value = parent.value,
      sumValue,
      minValue,
      maxValue,
      newRatio,
      minRatio,
      alpha,
      beta;

  while (i0 < n) {
    dx = x1 - x0, dy = y1 - y0;

    // Find the next non-empty node.
    do sumValue = nodes[i1++].value; while (!sumValue && i1 < n);
    minValue = maxValue = sumValue;
    alpha = Math.max(dy / dx, dx / dy) / (value * ratio);
    beta = sumValue * sumValue * alpha;
    minRatio = Math.max(maxValue / beta, beta / minValue);

    // Keep adding nodes while the aspect ratio maintains or improves.
    for (; i1 < n; ++i1) {
      sumValue += nodeValue = nodes[i1].value;
      if (nodeValue < minValue) minValue = nodeValue;
      if (nodeValue > maxValue) maxValue = nodeValue;
      beta = sumValue * sumValue * alpha;
      newRatio = Math.max(maxValue / beta, beta / minValue);
      if (newRatio > minRatio) { sumValue -= nodeValue; break; }
      minRatio = newRatio;
    }

    // Position and record the row orientation.
    rows.push(row = {value: sumValue, dice: dx < dy, children: nodes.slice(i0, i1)});
    if (row.dice) treemapDice(row, x0, y0, x1, value ? y0 += dy * sumValue / value : y1);
    else treemapSlice(row, x0, y0, value ? x0 += dx * sumValue / value : x1, y1);
    value -= sumValue, i0 = i1;
  }

  return rows;
}

export default (function custom(ratio) {

  function squarify(parent, x0, y0, x1, y1) {
    squarifyRatio(ratio, parent, x0, y0, x1, y1);
  }

  squarify.ratio = function(x) {
    return custom((x = +x) > 1 ? x : 1);
  };

  return squarify;
})(phi);