class ReactCluster extends React.Component {
  componentDidMount() {
    // all the d3 magic will happen
    // *AFTER* render - it will be added to the existing 
    // svg node
    cluster(this.props);
  }
  render() {
    const {height, width} = this.props;
    const id = this.props.container.replace('#', '');
    return <svg id={id} height={height} width={width} />;
  }
}

function cluster({padding, clusterPadding, height, width, maxRadius, n, m, container}) {
  // taken straight from https://bl.ocks.org/mbostock/7881887
  var color = d3.scale.category10()
      .domain(d3.range(m));

  // The largest node for each cluster.
  var clusters = new Array(m);

  var nodes = d3.range(n).map(function() {
    var i = Math.floor(Math.random() * m),
        r = Math.sqrt((i + 1) / m * -Math.log(Math.random())) * maxRadius,
        d = {
          cluster: i,
          radius: r,
          x: Math.cos(i / m * 2 * Math.PI) * 200 + width / 2 + Math.random(),
          y: Math.sin(i / m * 2 * Math.PI) * 200 + height / 2 + Math.random()
        };
    if (!clusters[i] || (r > clusters[i].radius)) clusters[i] = d;
    return d;
  });

  var force = d3.layout.force()
      .nodes(nodes)
      .size([width, height])
      .gravity(.02)
      .charge(0)
      .on("tick", tick)
      .start();

  // following 2 statements changed from original block
  var containerNode = d3.select("body").select(container);

  var node = containerNode.selectAll("circle")
      .data(nodes)
    .enter().append("circle")
      .style("fill", function(d) { return color(d.cluster); })
      .call(force.drag);

  node.transition()
      .duration(750)
      .delay(function(d, i) { return i * 5; })
      .attrTween("r", function(d) {
        var i = d3.interpolate(0, d.radius);
        return function(t) { return d.radius = i(t); };
      });

  function tick(e) {
    node
        .each(cluster(10 * e.alpha * e.alpha))
        .each(collide(.5))
        .attr("cx", function(d) { return d.x; })
        .attr("cy", function(d) { return d.y; });
  }

  // Move d to be adjacent to the cluster node.
  function cluster(alpha) {
    return function(d) {
      var cluster = clusters[d.cluster];
      if (cluster === d) return;
      var x = d.x - cluster.x,
          y = d.y - cluster.y,
          l = Math.sqrt(x * x + y * y),
          r = d.radius + cluster.radius;
      if (l != r) {
        l = (l - r) / l * alpha;
        d.x -= x *= l;
        d.y -= y *= l;
        cluster.x += x;
        cluster.y += y;
      }
    };
  }

  // Resolves collisions between d and all other circles.
  function collide(alpha) {
    var quadtree = d3.geom.quadtree(nodes);
    return function(d) {
      var r = d.radius + maxRadius + Math.max(padding, clusterPadding),
          nx1 = d.x - r,
          nx2 = d.x + r,
          ny1 = d.y - r,
          ny2 = d.y + r;
      quadtree.visit(function(quad, x1, y1, x2, y2) {
        if (quad.point && (quad.point !== d)) {
          var x = d.x - quad.point.x,
              y = d.y - quad.point.y,
              l = Math.sqrt(x * x + y * y),
              r = d.radius + quad.point.radius + (d.cluster === quad.point.cluster ? padding : clusterPadding);
          if (l < r) {
            l = (l - r) / l * alpha;
            d.x -= x *= l;
            d.y -= y *= l;
            quad.point.x += x;
            quad.point.y += y;
          }
        }
        return x1 > nx2 || x2 < nx1 || y1 > ny2 || y2 < ny1;
      });
    };
  }
}

function rand(max) {
  return Math.floor(Math.random() * max);
}

const clusters = <div>
        {[
          {id: 0, clusterPadding: 0, height: 150, m: 1, maxRadius: 10, n: 10, padding: 1.5, width: 200},
          {id: 1, height: 150},
          {id: 2, m: 3, maxRadius: 4, padding: 5, n: 50, height: 150, width: 144},
          {id: 3, width: 669, height: 275}
         ].map(d => 
  <div style={{border: '1px solid #ccc', display: 'inline-block', verticalAlign: 'top', margin: 5}}><ReactCluster 
    clusterPadding={d.clusterPadding || 6}
    container={"#svg" + d.id}
    height={d.height || 300}
    m={d.m || 5}
    maxRadius={d.maxRadius || 10}
    n={d.n || 100}
    padding={d.padding || 1.5}
    width={d.width || 300}
  /></div>)}
</div>;
      
ReactDOM.render(clusters, document.querySelector('#root'));