First commit.

Signed-off-by: Chen Xiao <abigwc@gmail.com>

client/node_modules/d3-force/src/manyBody.js

@@ -0,0 +1,116 @@
+import {quadtree} from "d3-quadtree";
+import constant from "./constant.js";
+import jiggle from "./jiggle.js";
+import {x, y} from "./simulation.js";
+
+export default function() {
+  var nodes,
+      node,
+      random,
+      alpha,
+      strength = constant(-30),
+      strengths,
+      distanceMin2 = 1,
+      distanceMax2 = Infinity,
+      theta2 = 0.81;
+
+  function force(_) {
+    var i, n = nodes.length, tree = quadtree(nodes, x, y).visitAfter(accumulate);
+    for (alpha = _, i = 0; i < n; ++i) node = nodes[i], tree.visit(apply);
+  }
+
+  function initialize() {
+    if (!nodes) return;
+    var i, n = nodes.length, node;
+    strengths = new Array(n);
+    for (i = 0; i < n; ++i) node = nodes[i], strengths[node.index] = +strength(node, i, nodes);
+  }
+
+  function accumulate(quad) {
+    var strength = 0, q, c, weight = 0, x, y, i;
+
+    // For internal nodes, accumulate forces from child quadrants.
+    if (quad.length) {
+      for (x = y = i = 0; i < 4; ++i) {
+        if ((q = quad[i]) && (c = Math.abs(q.value))) {
+          strength += q.value, weight += c, x += c * q.x, y += c * q.y;
+        }
+      }
+      quad.x = x / weight;
+      quad.y = y / weight;
+    }
+
+    // For leaf nodes, accumulate forces from coincident quadrants.
+    else {
+      q = quad;
+      q.x = q.data.x;
+      q.y = q.data.y;
+      do strength += strengths[q.data.index];
+      while (q = q.next);
+    }
+
+    quad.value = strength;
+  }
+
+  function apply(quad, x1, _, x2) {
+    if (!quad.value) return true;
+
+    var x = quad.x - node.x,
+        y = quad.y - node.y,
+        w = x2 - x1,
+        l = x * x + y * y;
+
+    // Apply the Barnes-Hut approximation if possible.
+    // Limit forces for very close nodes; randomize direction if coincident.
+    if (w * w / theta2 < l) {
+      if (l < distanceMax2) {
+        if (x === 0) x = jiggle(random), l += x * x;
+        if (y === 0) y = jiggle(random), l += y * y;
+        if (l < distanceMin2) l = Math.sqrt(distanceMin2 * l);
+        node.vx += x * quad.value * alpha / l;
+        node.vy += y * quad.value * alpha / l;
+      }
+      return true;
+    }
+
+    // Otherwise, process points directly.
+    else if (quad.length || l >= distanceMax2) return;
+
+    // Limit forces for very close nodes; randomize direction if coincident.
+    if (quad.data !== node || quad.next) {
+      if (x === 0) x = jiggle(random), l += x * x;
+      if (y === 0) y = jiggle(random), l += y * y;
+      if (l < distanceMin2) l = Math.sqrt(distanceMin2 * l);
+    }
+
+    do if (quad.data !== node) {
+      w = strengths[quad.data.index] * alpha / l;
+      node.vx += x * w;
+      node.vy += y * w;
+    } while (quad = quad.next);
+  }
+
+  force.initialize = function(_nodes, _random) {
+    nodes = _nodes;
+    random = _random;
+    initialize();
+  };
+
+  force.strength = function(_) {
+    return arguments.length ? (strength = typeof _ === "function" ? _ : constant(+_), initialize(), force) : strength;
+  };
+
+  force.distanceMin = function(_) {
+    return arguments.length ? (distanceMin2 = _ * _, force) : Math.sqrt(distanceMin2);
+  };
+
+  force.distanceMax = function(_) {
+    return arguments.length ? (distanceMax2 = _ * _, force) : Math.sqrt(distanceMax2);
+  };
+
+  force.theta = function(_) {
+    return arguments.length ? (theta2 = _ * _, force) : Math.sqrt(theta2);
+  };
+
+  return force;
+}