@gitlab/ui/dist/utils/matrix/columns.js

GitLab UI Components

import { CONFIG, GLYPHS } from './constants';

const randomBetween = (min, max) => min + Math.random() * (max - min);
const sample = values => values[Math.floor(Math.random() * values.length)];
const glyph = () => sample(GLYPHS);
const measureGrid = _ref => {
  let width = _ref.width,
    height = _ref.height;
  return {
    across: Math.ceil(width / CONFIG.cell),
    rows: Math.ceil(height / CONFIG.cell)
  };
};
const createColumns = (stage, colors) => {
  const _measureGrid = measureGrid(stage),
    across = _measureGrid.across,
    rows = _measureGrid.rows;
  return Array.from({
    length: across
  }, (value, column) => ({
    column,
    rows,
    row: -randomBetween(0, CONFIG.startSpread),
    speed: randomBetween(CONFIG.minSpeed, CONFIG.maxSpeed),
    color: sample(colors),
    head: null,
    steps: []
  })).filter(() => Math.random() < CONFIG.columnShare);
};
const advanceColumn = (column, delta) => {
  if (column.row > column.rows + CONFIG.restartAfter) {
    return {
      ...column,
      row: -randomBetween(0, CONFIG.restartSpread),
      head: null,
      steps: []
    };
  }
  const row = column.row + column.speed * delta;
  const from = Math.max(0, Math.ceil(column.row));
  const to = Math.min(column.rows, Math.floor(row));
  const steps = [];
  for (let step = from; step <= to; step += 1) {
    steps.push(step);
  }
  return {
    ...column,
    row,
    head: steps.length ? steps.at(-1) : column.head,
    steps
  };
};

export { advanceColumn, createColumns, glyph, measureGrid };